Sensors

1439 KiB

Open AccessArticle

FRET-Based Nanobiosensors for Imaging Intracellular Ca²⁺ and H⁺ Microdomains

by Alsu I. Zamaleeva, Guillaume Despras, Camilla Luccardini, Mayeul Collot, Michel De Waard, Martin Oheim, Jean-Maurice Mallet and Anne Feltz

Sensors 2015, 15(9), 24662-24680; https://doi.org/10.3390/s150924662 - 23 Sep 2015

Cited by 14 | Viewed by 8186

Abstract

Semiconductor nanocrystals (NCs) or quantum dots (QDs) are luminous point emitters increasingly being used to tag and track biomolecules in biological/biomedical imaging. However, their intracellular use as highlighters of single-molecule localization and nanobiosensors reporting ion microdomains changes has remained a major challenge. Here, [...] Read more.

Semiconductor nanocrystals (NCs) or quantum dots (QDs) are luminous point emitters increasingly being used to tag and track biomolecules in biological/biomedical imaging. However, their intracellular use as highlighters of single-molecule localization and nanobiosensors reporting ion microdomains changes has remained a major challenge. Here, we report the design, generation and validation of FRET-based nanobiosensors for detection of intracellular Ca²⁺ and H⁺ transients. Our sensors combine a commercially available CANdot^®565QD as an energy donor with, as an acceptor, our custom-synthesized red-emitting Ca²⁺ or H⁺ probes. These ‘Rubies’ are based on an extended rhodamine as a fluorophore and a phenol or BAPTA (1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetra-acetic acid) for H⁺ or Ca²⁺ sensing, respectively, and additionally bear a linker arm for conjugation. QDs were stably functionalized using the same SH/maleimide crosslink chemistry for all desired reactants. Mixing ion sensor and cell-penetrating peptides (that facilitate cytoplasmic delivery) at the desired stoichiometric ratio produced controlled multi-conjugated assemblies. Multiple acceptors on the same central donor allow up-concentrating the ion sensor on the QD surface to concentrations higher than those that could be achieved in free solution, increasing FRET efficiency and improving the signal. We validate these nanosensors for the detection of intracellular Ca²⁺ and pH transients using live-cell fluorescence imaging. Full article

(This article belongs to the Special Issue FRET Biosensors)

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Figure 1
FRET-based red-emitting ion sensors: (A) Principle. Coupling a green-emitting quantum dot (QD: here CANdot®565) donor to a red-emitting rhodamine-based ion sensor, the acceptor, produces an analyte-dependent FRET signal upon donor excitation at 405 nm. The custom red-emitting ion sensors used here are Ca2+ (alternatively H+) indicators, the emission of which is quenched by PET in absence of their ligand. Analyte binding results in a strong fluorescence peaking at 602 nm; (B–D) Chemical structure of the sensors: All sensors are built on an extended rhodamine moiety (blue). The two Ca2+ sensor families incorporate a BAPTA moiety (green), without (B) and with (C) an oxygen introduced on one of the aromatic ring of the BAPTA for the lower and higher affinity families: CaRuby1 (µM-mM range) and CaRuby2 (sub-µM range), respectively. Substitutions (Z1, Z2 in red with Z1=Cl, Z2=H for the chloride derivatives, and Z1=H, Z2=F for the fluorine derivatives, Z1=H, Z2=Me for CaRu1-Me) yield compounds with a finely tunable KD for Ca2+ binding. The pH sensor family (HRubies, (D)) is based on the addition of a phenol instead of a BAPTA. Note that all compounds bear an azido/alkyne side arm for click chemistry and the resulting potential for high-yield coupling reactions. The azide bearing linker is introduced in the bridge between the two aromatic rings of the BAPTA for the CaRubies1, and on the additional oxygen for the CaRubies2. HR-PiAC bears an alkyne moiety at the ortho position of the phenol through a piperazine carbamate link; (E–G) Spectral properties of retained donor/acceptor pairs (E) normalized absorbance and emission spectra (dashed and plain lines, respectively) of QD565 (green) and CaRu-Me (red). Since there is only a slight Ca2+ sensitivity of CaRu-Me absorbance when switching from EGTA- to 2 mM Ca2+-containing solution, the KDs of CaRu-Me and QDCaRu-Me were similar, as expected. Similar properties are expected with CaRu2-F and HR-PiAC since their absorbance is respectively Ca2+ and pH insensitive, as illustrated in panels (F) and (G), where blue and red traces are in absence and presence of the analyte, respectively. Full article ">Figure 2
Assembly of FRET-based ion sensors. CANdots have a CdSe core surrounded by a double layer of CdZn and ZnS. The QD TOP/TOPO (Step 1) passivating layer was replaced by a hydrophilic coating peptide made by mixing 50% cysteine-(SH function) and 50% lysine-(NH2 function) terminated peptides (Cys-peptide: Ac-CGSESGGSESG(FCC)3F-amide and Lys-peptide: NH2-KGSESGGSESG(FCC)3F-amide, respectively). Independently, an azide/alkyne-terminated ligand was bound to a clickable NH2-PEG to form a PEGylated dye (Step 2). Nanoparticles were then functionalized by adding the pegylated rhodamine-based sensor (red dots) (Step 3) using a SH/NH2 crosslinking reaction. Other NH2 terminated ligands can be added using the same crosslinking reaction and are included in stoichiometric ratio (not shown). Full article ">Figure 3
FRET between a QD565 donor and rhodamine-based ion-sensing acceptor fluorophores. FRET was measured as donor quenching upon QD excitation at 407 nm and acceptor sensitization, as a function of A/D ratio. Experiments were performed at an elevated analyte concentration (500 µM) to fully relieve the PET quenching of the dye. (A) Series of mixed spectra obtained by increasing the number of PEG5kDa -CaRuby2-F while keeping QD concentration constant (40 nM), in saturating Ca2+, 500 µM. The A/D ratio was determined by absorbance measurements at 407 and 581 nm, to evaluate QD565 and CaRuby concentrations, respectively; (B) Relative donor quenching (QD photoluminescence, red) and FRET efficiency (black) are reported after linear unmixing of donor and acceptor spectra, see Supplementary Material 6. Green data points shows acceptor sensitization (FCaRuby (exc. @ 350 nm) − FQD (exc. @ 350 nm)/(FCaRuby (exc. @ 535 nm)); (C,D) Similar experiments were carried with QD-HR-PiAC, with the pH adjusted to 4. In both cases, symbols ▲, ● show results from two independent runs. Full article ">Figure 4
(A) Fluorometric titration of FRET-based nanobiosensor assemblies: QD-PEG5kDa-CaRu2F (prepared with A/D ratio= 7.4, and using the Invitrogen Ca2+ buffer kit to adjust [Ca2+]); Spectra (left) were obtained when following Ca2+ concentrations were successively applied: 1, 17, 38, 65, 100, 150, 225, 351, 602 nM and 1.35 and 39 µM from bottom to top traces; (right) Resulting titration curves using direct excitation at 545 nm or FRET excitation upon QDs excitation at 407-nm; (B) QD-PEG5kDa -HR-PiAC (A/D ratio= 5.6), universal pH buffer, see Supplementary 3, p. 830 in [<a href="#B20-sensors-15-24662" class="html-bibr">20</a>]). Fluorescence curves are corrected for the pH sensitivity of the QDs fluorescence (see <a href="#sensors-15-24662-s001" class="html-supplementary-material">Figure S3</a> for details). Spectra shown on the left correspond to pH 6, 7.45, 7.65, 8.3, 8.9, 10.3, 11.45 and 11.9 from top to bottom, respectively. On the right: measured KDs are similar when carrying fluorometric titration either by direct excitation (at 545 nm) or by FRET excitation (at 407 nm). Full article ">Figure 5
Live-cell imaging of intracellular ion distributions. (A–C) Confocal images of BHK-21 cells after incubation with QD-HRu PiAC (A) co-stained by Lysotracker Green; (B) and a merged image of the two channels (C). Scale bar is 20 µm; (D–G) Intracellular calibration of pH sensors in a suspension of BHK-21 cells using flow cytometry. Typical histograms showing the internalization of the QD565/H-Ruby pH sensors according to the H-Ruby intensity (in grey, the cell without sensors, and in red, the cells having internalized pH sensors) upon direct (D) and by FRET excitation (F). Calibration curves of the intracellular pH sensors clamped at different pH with the ionophore nigericin were obtained by direct (E) and by FRET excitation (G) of H-Ruby. Intracellular pH as measured by the red histograms of fluorescence H-Ruby in (D,F) was evaluated (black dots) by extrapolation on the calibration curves (E,G), respectively; (H,I) Read-out of local Ca2+ transients upon glutamate application on BHK cells stably expressing the NR1 and NR2A subunits of the N-methyl-D-aspartate receptors (NMDARs). (H) Firstly internalized biosensors (QD-CaRuby-CPP in a ratio 1:10:10) were localized by superimposition of the bright-field and time-averaged TIRF image of cultured BHK cells detected in the green channel upon 405-nm evanescent-wave excitation of the QDs. (I) Repetitive stimulation evokes reversible Ca2+ transients. Superimposed traces obtained in the red channel following 568-nm excitation are responses of the Ca2+ sensor to two successive bath applications of NMDAR agonists at a saturating concentration, with a 15 min long continuous bath perfusion of control saline for recovery from desensitization in between. <a href="#sensors-15-24662-f005" class="html-fig">Figure 5</a>H,I is reprinted with permission from Zamaleeva et al., 2014 [<a href="#B8-sensors-15-24662" class="html-bibr">8</a>]. Copyright 2015 American Chemical Society. Full article ">Figure 6
Twisted-intramolecular charge transfer in CaRuby (at the left) and HRuby (at the right) dyes. Full article ">

1230 KiB

Open AccessArticle

A Location Method Using Sensor Arrays for Continuous Gas Leakage in Integrally Stiffened Plates Based on the Acoustic Characteristics of the Stiffener

by Xu Bian, Yibo Li, Hao Feng, Jiaqiang Wang, Lei Qi and Shijiu Jin

Sensors 2015, 15(9), 24644-24661; https://doi.org/10.3390/s150924644 - 23 Sep 2015

Cited by 15 | Viewed by 5613

Abstract

This paper proposes a continuous leakage location method based on the ultrasonic array sensor, which is specific to continuous gas leakage in a pressure container with an integral stiffener. This method collects the ultrasonic signals generated from the leakage hole through the piezoelectric [...] Read more.

This paper proposes a continuous leakage location method based on the ultrasonic array sensor, which is specific to continuous gas leakage in a pressure container with an integral stiffener. This method collects the ultrasonic signals generated from the leakage hole through the piezoelectric ultrasonic sensor array, and analyzes the space-time correlation of every collected signal in the array. Meanwhile, it combines with the method of frequency compensation and superposition in time domain (SITD), based on the acoustic characteristics of the stiffener, to obtain a high-accuracy location result on the stiffener wall. According to the experimental results, the method successfully solves the orientation problem concerning continuous ultrasonic signals generated from leakage sources, and acquires high accuracy location information on the leakage source using a combination of multiple sets of orienting results. The mean value of location absolute error is 13.51 mm on the one-square-meter plate with an integral stiffener (4 mm width; 20 mm height; 197 mm spacing), and the maximum location absolute error is generally within a ±25 mm interval. Full article

(This article belongs to the Section Physical Sensors)

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11865 KiB

Open AccessArticle

A New Approach for Combining Time-of-Flight and RGB Cameras Based on Depth-Dependent Planar Projective Transformations

by Carlota Salinas, Roemi Fernández, Héctor Montes and Manuel Armada

Sensors 2015, 15(9), 24615-24643; https://doi.org/10.3390/s150924615 - 23 Sep 2015

Cited by 12 | Viewed by 6103

Abstract

Image registration for sensor fusion is a valuable technique to acquire 3D and colour information for a scene. Nevertheless, this process normally relies on feature-matching techniques, which is a drawback for combining sensors that are not able to deliver common features. The combination [...] Read more.

Image registration for sensor fusion is a valuable technique to acquire 3D and colour information for a scene. Nevertheless, this process normally relies on feature-matching techniques, which is a drawback for combining sensors that are not able to deliver common features. The combination of ToF and RGB cameras is an instance that problem. Typically, the fusion of these sensors is based on the extrinsic parameter computation of the coordinate transformation between the two cameras. This leads to a loss of colour information because of the low resolution of the ToF camera, and sophisticated algorithms are required to minimize this issue. This work proposes a method for sensor registration with non-common features and that avoids the loss of colour information. The depth information is used as a virtual feature for estimating a depth-dependent homography lookup table (Hlut). The homographies are computed within sets of ground control points of 104 images. Since the distance from the control points to the ToF camera are known, the working distance of each element on the Hlut is estimated. Finally, two series of experimental tests have been carried out in order to validate the capabilities of the proposed method. Full article

(This article belongs to the Section Physical Sensors)

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2020 KiB

Open AccessArticle

Integrated WiFi/PDR/Smartphone Using an Unscented Kalman Filter Algorithm for 3D Indoor Localization

by Guoliang Chen, Xiaolin Meng, Yunjia Wang, Yanzhe Zhang, Peng Tian and Huachao Yang

Sensors 2015, 15(9), 24595-24614; https://doi.org/10.3390/s150924595 - 23 Sep 2015

Cited by 117 | Viewed by 11336

Abstract

Because of the high calculation cost and poor performance of a traditional planar map when dealing with complicated indoor geographic information, a WiFi fingerprint indoor positioning system cannot be widely employed on a smartphone platform. By making full use of the hardware sensors [...] Read more.

Because of the high calculation cost and poor performance of a traditional planar map when dealing with complicated indoor geographic information, a WiFi fingerprint indoor positioning system cannot be widely employed on a smartphone platform. By making full use of the hardware sensors embedded in the smartphone, this study proposes an integrated approach to a three-dimensional (3D) indoor positioning system. First, an improved K-means clustering method is adopted to reduce the fingerprint database retrieval time and enhance positioning efficiency. Next, with the mobile phone’s acceleration sensor, a new step counting method based on auto-correlation analysis is proposed to achieve cell phone inertial navigation positioning. Furthermore, the integration of WiFi positioning with Pedestrian Dead Reckoning (PDR) obtains higher positional accuracy with the help of the Unscented Kalman Filter algorithm. Finally, a hybrid 3D positioning system based on Unity 3D, which can carry out real-time positioning for targets in 3D scenes, is designed for the fluent operation of mobile terminals. Full article

(This article belongs to the Special Issue Sensors for Indoor Mapping and Navigation)

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807 KiB

Open AccessArticle

Location Dependence of Mass Sensitivity for Acoustic Wave Devices

by Kewei Zhang, Yuesheng Chai and Z.-Y. Cheng

Sensors 2015, 15(9), 24585-24594; https://doi.org/10.3390/s150924585 - 23 Sep 2015

Cited by 5 | Viewed by 4271

Abstract

It is introduced that the mass sensitivity (S_m) of an acoustic wave (AW) device with a concentrated mass can be simply determined using its mode shape function: the S_m is proportional to the square of its mode shape. By [...] Read more.

It is introduced that the mass sensitivity (S_m) of an acoustic wave (AW) device with a concentrated mass can be simply determined using its mode shape function: the S_m is proportional to the square of its mode shape. By using the S_m of an AW device with a uniform mass, which is known for almost all AW devices, the S_m of an AW device with a concentrated mass at different locations can be determined. The method is confirmed by numerical simulation for one type of AW device and the results from two other types of AW devices. Full article

(This article belongs to the Section Physical Sensors)

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Figure 1
Simulated Sm (solid squares) for the concentrated mass load at different locationsm (xc) for the MSP operated at the fundamnetal resonant mode. The parameters of the MSP is listed in <a href="#sensors-15-24585-t001" class="html-table">Table 1</a>. The numerical simulation is done for a mass load of M* = Δm/M = 10−5. The solid line is the fitting curve. Full article ">Figure 2
Mass sensitivity (Sm) of a cantilever with a concentrated mass versus the location (x) of the mass, where Sm is calculated using the methodology introduced here. The y-axis is normalized as <math display="inline"> <semantics> <mrow> <msub> <mi>S</mi> <mi>m</mi> </msub> <mrow> <mo>(</mo> <mi>x</mi> <mo>)</mo> </mrow> <mo>/</mo> <msubsup> <mi>S</mi> <mi>m</mi> <mrow> <mi>u</mi> <mi>n</mi> <mi>i</mi> </mrow> </msubsup> </mrow> </semantics> </math>, where <math display="inline"> <semantics> <mrow> <msubsup> <mi>S</mi> <mi>m</mi> <mrow> <mi>u</mi> <mi>n</mi> <mi>i</mi> </mrow> </msubsup> </mrow> </semantics> </math> is defined by Equations (1) and (10). Full article ">

705 KiB

Open AccessArticle

Effect of Electrode Configuration on Nitric Oxide Gas Sensor Behavior

by Ling Cui and Erica P. Murray

Sensors 2015, 15(9), 24573-24584; https://doi.org/10.3390/s150924573 - 23 Sep 2015

Cited by 6 | Viewed by 6384

Abstract

The influence of electrode configuration on the impedancemetric response of nitric oxide (NO) gas sensors was investigated for solid electrochemical cells [Au/yttria-stabilized zirconia (YSZ)/Au)]. Fabrication of the sensors was carried out at 1050 °C in order to establish a porous YSZ electrolyte that [...] Read more.

The influence of electrode configuration on the impedancemetric response of nitric oxide (NO) gas sensors was investigated for solid electrochemical cells [Au/yttria-stabilized zirconia (YSZ)/Au)]. Fabrication of the sensors was carried out at 1050 °C in order to establish a porous YSZ electrolyte that enabled gas diffusion. Two electrode configurations were studied where Au wire electrodes were either embedded within or wrapped around the YSZ electrolyte. The electrical response of the sensors was collected via impedance spectroscopy under various operating conditions where gas concentrations ranged from 0 to 100 ppm NO and 1%–18% O₂ at temperatures varying from 600 to 700 °C. Gas diffusion appeared to be a rate-limiting mechanism in sensors where the electrode configuration resulted in longer diffusion pathways. The temperature dependence of the NO sensors studied was independent of the electrode configuration. Analysis of the impedance data, along with equivalent circuit modeling indicated the electrode configuration of the sensor effected gas and ionic transport pathways, capacitance behavior, and NO sensitivity. Full article

(This article belongs to the Special Issue Gas Sensors—Designs and Applications)

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Graphical abstract
Full article ">Figure 1
Diagrams of the NO sensors with electrode configurations (a) EC1 and EC2; (b) Cross sectional view illustrating the placement of the Au electrodes within the YSZ tape layers composing the sensor. Full article ">Figure 2
Typical Nyquist plot showing the impedance response of EC1 and EC2 sensors at an operating temperature of 650 °C, in 10.5% O2 with and without NO present. The equivalent circuit used to model the data is shown in the upper right corner of the plot. The model that fit the data is described by the solid lines. Full article ">Figure 3
The capacitance versus NO concentration is shown for the (a) high and (b) low frequency arcs associated with the EC1 and EC2 sensors. Full article ">Figure 4
The change in capacitance is plotted for EC1 and EC2 sensors for NO concentrations ranging from 5 to 100 ppm. Full article ">Figure 5
The change in the angular phase angle is plotted for EC1 and EC2 sensors for NO concentrations ranging from 5 to 100 ppm. Full article ">Figure 6
The oxygen partial pressure dependence of the EC1 and EC2 sensors is shown for data collected at 650 °C for oxygen concentrations ranging from 1% to 18%. Full article ">Figure 7
The temperature dependence is described by the Arrhenius plot for the EC1 and EC2 sensors along with corresponding activation energies. Full article ">

892 KiB

Open AccessArticle

Wireless Power Transfer for Autonomous Wearable Neurotransmitter Sensors

by Cuong M. Nguyen, Pavan Kumar Kota, Minh Q. Nguyen, Souvik Dubey, Smitha Rao, Jeffrey Mays and J.-C. Chiao

Sensors 2015, 15(9), 24553-24572; https://doi.org/10.3390/s150924553 - 23 Sep 2015

Cited by 19 | Viewed by 7816

Abstract

In this paper, we report a power management system for autonomous and real-time monitoring of the neurotransmitter L-glutamate (L-Glu). A low-power, low-noise, and high-gain recording module was designed to acquire signal from an implantable flexible L-Glu sensor fabricated by micro-electro-mechanical system (MEMS)-based processes. [...] Read more.

In this paper, we report a power management system for autonomous and real-time monitoring of the neurotransmitter L-glutamate (L-Glu). A low-power, low-noise, and high-gain recording module was designed to acquire signal from an implantable flexible L-Glu sensor fabricated by micro-electro-mechanical system (MEMS)-based processes. The wearable recording module was wirelessly powered through inductive coupling transmitter antennas. Lateral and angular misalignments of the receiver antennas were resolved by using a multi-transmitter antenna configuration. The effective coverage, over which the recording module functioned properly, was improved with the use of in-phase transmitter antennas. Experimental results showed that the recording system was capable of operating continuously at distances of 4 cm, 7 cm and 10 cm. The wireless power management system reduced the weight of the recording module, eliminated human intervention and enabled animal experimentation for extended durations. Full article

(This article belongs to the Special Issue Power Schemes for Biosensors and Biomedical Devices)

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3496 KiB

Open AccessArticle

Research on the Sensing Performance of the Tuning Fork-Probe as a Micro Interaction Sensor

by Fengli Gao and Xide Li

Sensors 2015, 15(9), 24530-24552; https://doi.org/10.3390/s150924530 - 23 Sep 2015

Cited by 12 | Viewed by 5496

Abstract

The shear force position system has been widely used in scanning near-field optical microscopy (SNOM) and recently extended into the force sensing area. The dynamic properties of a tuning fork (TF), the core component of this system, directly determine the sensing performance of [...] Read more.

The shear force position system has been widely used in scanning near-field optical microscopy (SNOM) and recently extended into the force sensing area. The dynamic properties of a tuning fork (TF), the core component of this system, directly determine the sensing performance of the shear positioning system. Here, we combine experimental results and finite element method (FEM) analysis to investigate the dynamic behavior of the TF probe assembled structure (TF-probe). Results from experiments under varying atmospheric pressures illustrate that the oscillation amplitude of the TF-probe is linearly related to the quality factor, suggesting that decreasing the pressure will dramatically increase the quality factor. The results from FEM analysis reveal the influences of various parameters on the resonant performance of the TF-probe. We compared numerical results of the frequency spectrum with the experimental data collected by our recently developed laser Doppler vibrometer system. Then, we investigated the parameters affecting spatial resolution of the SNOM and the dynamic response of the TF-probe under longitudinal and transverse interactions. It is found that the interactions in transverse direction is much more sensitive than that in the longitudinal direction. Finally, the TF-probe was used to measure the friction coefficient of a silica–silica interface. Full article

(This article belongs to the Section State-of-the-Art Sensors Technologies)

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720 KiB

Open AccessArticle

Validation of Inter-Subject Training for Hidden Markov Models Applied to Gait Phase Detection in Children with Cerebral Palsy

by Juri Taborri, Emilia Scalona, Eduardo Palermo, Stefano Rossi and Paolo Cappa

Sensors 2015, 15(9), 24514-24529; https://doi.org/10.3390/s150924514 - 23 Sep 2015

Cited by 60 | Viewed by 7161

Abstract

Gait-phase recognition is a necessary functionality to drive robotic rehabilitation devices for lower limbs. Hidden Markov Models (HMMs) represent a viable solution, but they need subject-specific training, making data processing very time-consuming. Here, we validated an inter-subject procedure to avoid the intra-subject one [...] Read more.

Gait-phase recognition is a necessary functionality to drive robotic rehabilitation devices for lower limbs. Hidden Markov Models (HMMs) represent a viable solution, but they need subject-specific training, making data processing very time-consuming. Here, we validated an inter-subject procedure to avoid the intra-subject one in two, four and six gait-phase models in pediatric subjects. The inter-subject procedure consists in the identification of a standardized parameter set to adapt the model to measurements. We tested the inter-subject procedure both on scalar and distributed classifiers. Ten healthy children and ten hemiplegic children, each equipped with two Inertial Measurement Units placed on shank and foot, were recruited. The sagittal component of angular velocity was recorded by gyroscopes while subjects performed four walking trials on a treadmill. The goodness of classifiers was evaluated with the Receiver Operating Characteristic. The results provided a goodness from good to optimum for all examined classifiers (0 < G < 0.6), with the best performance for the distributed classifier in two-phase recognition (G = 0.02). Differences were found among gait partitioning models, while no differences were found between training procedures with the exception of the shank classifier. Our results raise the possibility of avoiding subject-specific training in HMM for gait-phase recognition and its implementation to control exoskeletons for the pediatric population. Full article

(This article belongs to the Special Issue Sensor Systems for Motion Capture and Interpretation)

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8250 KiB

Open AccessArticle

Sea-Based Infrared Scene Interpretation by Background Type Classification and Coastal Region Detection for Small Target Detection

by Sungho Kim

Sensors 2015, 15(9), 24487-24513; https://doi.org/10.3390/s150924487 - 23 Sep 2015

Cited by 15 | Viewed by 9710

Abstract

Sea-based infrared search and track (IRST) is important for homeland security by detecting missiles and asymmetric boats. This paper proposes a novel scheme to interpret various infrared scenes by classifying the infrared background types and detecting the coastal regions in omni-directional images. The [...] Read more.

Sea-based infrared search and track (IRST) is important for homeland security by detecting missiles and asymmetric boats. This paper proposes a novel scheme to interpret various infrared scenes by classifying the infrared background types and detecting the coastal regions in omni-directional images. The background type or region-selective small infrared target detector should be deployed to maximize the detection rate and to minimize the number of false alarms. A spatial filter-based small target detector is suitable for identifying stationary incoming targets in remote sea areas with sky only. Many false detections can occur if there is an image sector containing a coastal region, due to ground clutter and the difficulty in finding true targets using the same spatial filter-based detector. A temporal filter-based detector was used to handle these problems. Therefore, the scene type and coastal region information is critical to the success of IRST in real-world applications. In this paper, the infrared scene type was determined using the relationships between the sensor line-of-sight (LOS) and a horizontal line in an image. The proposed coastal region detector can be activated if the background type of the probing sector is determined to be a coastal region. Coastal regions can be detected by fusing the region map and curve map. The experimental results on real infrared images highlight the feasibility of the proposed sea-based scene interpretation. In addition, the effects of the proposed scheme were analyzed further by applying region-adaptive small target detection. Full article

(This article belongs to the Special Issue Infrared and THz Sensing and Imaging)

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1804 KiB

Open AccessArticle

Techniques for Updating Pedestrian Network Data Including Facilities and Obstructions Information for Transportation of Vulnerable People

by Seula Park, Yoonsik Bang and Kiyun Yu

Sensors 2015, 15(9), 24466-24486; https://doi.org/10.3390/s150924466 - 23 Sep 2015

Cited by 8 | Viewed by 4769

Abstract

Demand for a Pedestrian Navigation Service (PNS) is on the rise. To provide a PNS for the transportation of vulnerable people, more detailed information of pedestrian facilities and obstructions should be included in Pedestrian Network Data (PND) used for PNS. Such data can [...] Read more.

Demand for a Pedestrian Navigation Service (PNS) is on the rise. To provide a PNS for the transportation of vulnerable people, more detailed information of pedestrian facilities and obstructions should be included in Pedestrian Network Data (PND) used for PNS. Such data can be constructed efficiently by collecting GPS trajectories and integrating them with the existing PND. However, these two kinds of data have geometric differences and topological inconsistencies that need to be addressed. In this paper, we provide a methodology for integrating pedestrian facilities and obstructions information with an existing PND. At first we extracted the significant points from user-collected GPS trajectory by identifying the geometric difference index and attributes of each point. Then the extracted points were used to make an initial solution of the matching between the trajectory and the PND. Two geometrical algorithms were proposed and applied to reduce two kinds of errors in the matching: on dual lines and on intersections. Using the final solution for the matching, we reconstructed the node/link structure of PND including the facilities and obstructions information. Finally, performance was assessed with a test site and 79.2% of the collected data were correctly integrated with the PND. Full article

(This article belongs to the Section Physical Sensors)

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214 KiB

Open AccessConference Report

4th International Symposium on Sensor Science (I3S2015): Conference Report

by Peter Seitz, Debbie G. Senesky, Michael J. Schöning, Peter C. Hauser, Roland Moser, Hans Peter Herzig, Assefa M. Melesse, Patricia A. Broderick and Patrick Thomas Eugster

Sensors 2015, 15(9), 24458-24465; https://doi.org/10.3390/s150924458 - 23 Sep 2015

Viewed by 5795

Abstract

An international scientific conference was sponsored by the journal Sensors under the patronage of the University of Basel. The 4th edition of the International Symposium on Sensor Science (I3S2015) ran from 13 to 15 July 2015 in Basel, Switzerland. It comprised five plenary [...] Read more.

An international scientific conference was sponsored by the journal Sensors under the patronage of the University of Basel. The 4th edition of the International Symposium on Sensor Science (I3S2015) ran from 13 to 15 July 2015 in Basel, Switzerland. It comprised five plenary sessions and one morning with three parallel sessions. The conference covered the most exciting aspects and the latest developments in sensor science. The conference dinner took place on the second evening of the conference. The I3S2015 brought together 170 participants from 40 different countries. [...] Full article

(This article belongs to the Special Issue I3S 2015 Selected Papers)

1253 KiB

Open AccessArticle

Using LDR as Sensing Element for an External Fuzzy Controller Applied in Photovoltaic Pumping Systems with Variable-Speed Drives

by Geraldo Neves De A. Maranhão, Alaan Ubaiara Brito, Anderson Marques Leal, Jéssica Kelly Silva Fonseca and Wilson Negrão Macêdo

Sensors 2015, 15(9), 24445-24457; https://doi.org/10.3390/s150924445 - 22 Sep 2015

Cited by 8 | Viewed by 7602

Abstract

In the present paper, a fuzzy controller applied to a Variable-Speed Drive (VSD) for use in Photovoltaic Pumping Systems (PVPS) is proposed. The fuzzy logic system (FLS) used is embedded in a microcontroller and corresponds to a proportional-derivative controller. A Light-Dependent Resistor (LDR) [...] Read more.

In the present paper, a fuzzy controller applied to a Variable-Speed Drive (VSD) for use in Photovoltaic Pumping Systems (PVPS) is proposed. The fuzzy logic system (FLS) used is embedded in a microcontroller and corresponds to a proportional-derivative controller. A Light-Dependent Resistor (LDR) is used to measure, approximately, the irradiance incident on the PV array. Experimental tests are executed using an Arduino board. The experimental results show that the fuzzy controller is capable of operating the system continuously throughout the day and controlling the direct current (DC) voltage level in the VSD with a good performance. Full article

(This article belongs to the Section Physical Sensors)

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827 KiB

Open AccessArticle

Optimizing the De-Noise Neural Network Model for GPS Time-Series Monitoring of Structures

by Mosbeh R. Kaloop and Jong Wan Hu

Sensors 2015, 15(9), 24428-24444; https://doi.org/10.3390/s150924428 - 22 Sep 2015

Cited by 12 | Viewed by 6523

Abstract

The Global Positioning System (GPS) is recently used widely in structures and other applications. Notwithstanding, the GPS accuracy still suffers from the errors afflicting the measurements, particularly the short-period displacement of structural components. Previously, the multi filter method is utilized to remove the [...] Read more.

The Global Positioning System (GPS) is recently used widely in structures and other applications. Notwithstanding, the GPS accuracy still suffers from the errors afflicting the measurements, particularly the short-period displacement of structural components. Previously, the multi filter method is utilized to remove the displacement errors. This paper aims at using a novel application for the neural network prediction models to improve the GPS monitoring time series data. Four prediction models for the learning algorithms are applied and used with neural network solutions: back-propagation, Cascade-forward back-propagation, adaptive filter and extended Kalman filter, to estimate which model can be recommended. The noise simulation and bridge’s short-period GPS of the monitoring displacement component of one Hz sampling frequency are used to validate the four models and the previous method. The results show that the Adaptive neural networks filter is suggested for de-noising the observations, specifically for the GPS displacement components of structures. Also, this model is expected to have significant influence on the design of structures in the low frequency responses and measurements’ contents. Full article

(This article belongs to the Section Sensor Networks)

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1293 KiB

Open AccessArticle

Toward Epileptic Brain Region Detection Based on Magnetic Nanoparticle Patterning

by Maysam Z. Pedram, Amir Shamloo, Aria Alasty and Ebrahim Ghafar-Zadeh

Sensors 2015, 15(9), 24409-24427; https://doi.org/10.3390/s150924409 - 22 Sep 2015

Cited by 17 | Viewed by 5818

Abstract

Resection of the epilepsy foci is the best treatment for more than 15% of epileptic patients or 50% of patients who are refractory to all forms of medical treatment. Accurate mapping of the locations of epileptic neuronal networks can result in the complete [...] Read more.

Resection of the epilepsy foci is the best treatment for more than 15% of epileptic patients or 50% of patients who are refractory to all forms of medical treatment. Accurate mapping of the locations of epileptic neuronal networks can result in the complete resection of epileptic foci. Even though currently electroencephalography is the best technique for mapping the epileptic focus, it cannot define the boundary of epilepsy that accurately. Herein we put forward a new accurate brain mapping technique using superparamagnetic nanoparticles (SPMNs). The main hypothesis in this new approach is the creation of super-paramagnetic aggregates in the epileptic foci due to high electrical and magnetic activities. These aggregates may improve tissue contrast of magnetic resonance imaging (MRI) that results in improving the resection of epileptic foci. In this paper, we present the mathematical models before discussing the simulation results. Furthermore, we mimic the aggregation of SPMNs in a weak magnetic field using a low-cost microfabricated device. Based on these results, the SPMNs may play a crucial role in diagnostic epilepsy and the subsequent treatment of this disease. Full article

(This article belongs to the Special Issue Inorganic Nanoparticles as Biomedical Probes)

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537 KiB

Open AccessArticle

Configuration Analysis of the ERS Points in Large-Volume Metrology System

by Zhangjun Jin, Cijun Yu, Jiangxiong Li and Yinglin Ke

Sensors 2015, 15(9), 24397-24408; https://doi.org/10.3390/s150924397 - 22 Sep 2015

Cited by 34 | Viewed by 6097

Abstract

In aircraft assembly, multiple laser trackers are used simultaneously to measure large-scale aircraft components. To combine the independent measurements, the transformation matrices between the laser trackers’ coordinate systems and the assembly coordinate system are calculated, by measuring the enhanced referring system (ERS) points. [...] Read more.

In aircraft assembly, multiple laser trackers are used simultaneously to measure large-scale aircraft components. To combine the independent measurements, the transformation matrices between the laser trackers’ coordinate systems and the assembly coordinate system are calculated, by measuring the enhanced referring system (ERS) points. This article aims to understand the influence of the configuration of the ERS points that affect the transformation matrix errors, and then optimize the deployment of the ERS points to reduce the transformation matrix errors. To optimize the deployment of the ERS points, an explicit model is derived to estimate the transformation matrix errors. The estimation model is verified by the experiment implemented in the factory floor. Based on the proposed model, a group of sensitivity coefficients are derived to evaluate the quality of the configuration of the ERS points, and then several typical configurations of the ERS points are analyzed in detail with the sensitivity coefficients. Finally general guidance is established to instruct the deployment of the ERS points in the aspects of the layout, the volume size and the number of the ERS points, as well as the position and orientation of the assembly coordinate system. Full article

(This article belongs to the Section Sensor Networks)

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Open AccessReview

Recent Progress in Fluorescent Imaging Probes

by Yen Leng Pak, K. M. K. Swamy and Juyoung Yoon

Sensors 2015, 15(9), 24374-24396; https://doi.org/10.3390/s150924374 - 22 Sep 2015

Cited by 100 | Viewed by 12127

Abstract

Due to the simplicity and low detection limit, especially the bioimaging ability for cells, fluorescence probes serve as unique detection methods. With the aid of molecular recognition and specific organic reactions, research on fluorescent imaging probes has blossomed during the last decade. Especially, [...] Read more.

Due to the simplicity and low detection limit, especially the bioimaging ability for cells, fluorescence probes serve as unique detection methods. With the aid of molecular recognition and specific organic reactions, research on fluorescent imaging probes has blossomed during the last decade. Especially, reaction based fluorescent probes have been proven to be highly selective for specific analytes. This review highlights our recent progress on fluorescent imaging probes for biologically important species, such as biothiols, reactive oxygen species, reactive nitrogen species, metal ions including Zn²⁺, Hg²⁺, Cu²⁺ and Au³⁺, and anions including cyanide and adenosine triphosphate (ATP). Full article

(This article belongs to the Special Issue Fluorescent Probes for Intracellular Imaging and Super Resolution Microscopy)

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1104 KiB

Open AccessArticle

Implementation and Evaluation of Four Interoperable Open Standards for the Internet of Things

by Mohammad Ali Jazayeri, Steve H. L. Liang and Chih-Yuan Huang

Sensors 2015, 15(9), 24343-24373; https://doi.org/10.3390/s150924343 - 22 Sep 2015

Cited by 35 | Viewed by 8942

Abstract

Recently, researchers are focusing on a new use of the Internet called the Internet of Things (IoT), in which enabled electronic devices can be remotely accessed over the Internet. As the realization of IoT concept is still in its early stages, manufacturers of [...] Read more.

Recently, researchers are focusing on a new use of the Internet called the Internet of Things (IoT), in which enabled electronic devices can be remotely accessed over the Internet. As the realization of IoT concept is still in its early stages, manufacturers of Internet-connected devices and IoT web service providers are defining their proprietary protocols based on their targeted applications. Consequently, IoT becomes heterogeneous in terms of hardware capabilities and communication protocols. Addressing these heterogeneities by following open standards is a necessary step to communicate with various IoT devices. In this research, we assess the feasibility of applying existing open standards on resource-constrained IoT devices. The standard protocols developed in this research are OGC PUCK over Bluetooth, TinySOS, SOS over CoAP, and OGC SensorThings API. We believe that by hosting open standard protocols on IoT devices, not only do the devices become self-describable, self-contained, and interoperable, but innovative applications can also be easily developed with standardized interfaces. In addition, we use memory consumption, request message size, response message size, and response latency to benchmark the efficiency of the implemented protocols. In all, this research presents and evaluates standard-based solutions to better understand the feasibility of applying existing standards to the IoT vision. Full article

(This article belongs to the Section Sensor Networks)

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1630 KiB

Open AccessArticle

Measurement and Evaluation of the Gas Density and Viscosity of Pure Gases and Mixtures Using a Micro-Cantilever Beam

by Anastasios Badarlis, Axel Pfau and Anestis Kalfas

Sensors 2015, 15(9), 24318-24342; https://doi.org/10.3390/s150924318 - 22 Sep 2015

Cited by 22 | Viewed by 8126

Abstract

Measurement of gas density and viscosity was conducted using a micro-cantilever beam. In parallel, the validity of the proposed modeling approach was evaluated. This study also aimed to widen the database of the gases on which the model development of the micro-cantilever beams [...] Read more.

Measurement of gas density and viscosity was conducted using a micro-cantilever beam. In parallel, the validity of the proposed modeling approach was evaluated. This study also aimed to widen the database of the gases on which the model development of the micro-cantilever beams is based. The density and viscosity of gases are orders of magnitude lower than liquids. For this reason, the use of a very sensitive sensor is essential. In this study, a micro-cantilever beam from the field of atomic force microscopy was used. Although the current cantilever was designed to work with thermal activation, in the current investigation, it was activated with an electromagnetic force. The deflection of the cantilever beam was detected by an integrated piezo-resistive sensor. Six pure gases and sixteen mixtures of them in ambient conditions were investigated. The outcome of the investigation showed that the current cantilever beam had a sensitivity of 240 Hz/(kg/m³), while the accuracy of the determined gas density and viscosity in ambient conditions reached ±1.5% and ±2.0%, respectively. Full article

(This article belongs to the Section Physical Sensors)

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2311 KiB

Open AccessArticle

Leveraging Two Kinect Sensors for Accurate Full-Body Motion Capture

by Zhiquan Gao, Yao Yu, Yu Zhou and Sidan Du

Sensors 2015, 15(9), 24297-24317; https://doi.org/10.3390/s150924297 - 22 Sep 2015

Cited by 37 | Viewed by 8465

Abstract

Accurate motion capture plays an important role in sports analysis, the medical field and virtual reality. Current methods for motion capture often suffer from occlusions, which limits the accuracy of their pose estimation. In this paper, we propose a complete system to measure [...] Read more.

Accurate motion capture plays an important role in sports analysis, the medical field and virtual reality. Current methods for motion capture often suffer from occlusions, which limits the accuracy of their pose estimation. In this paper, we propose a complete system to measure the pose parameters of the human body accurately. Different from previous monocular depth camera systems, we leverage two Kinect sensors to acquire more information about human movements, which ensures that we can still get an accurate estimation even when significant occlusion occurs. Because human motion is temporally constant, we adopt a learning analysis to mine the temporal information across the posture variations. Using this information, we estimate human pose parameters accurately, regardless of rapid movement. Our experimental results show that our system can perform an accurate pose estimation of the human body with the constraint of information from the temporal domain. Full article

(This article belongs to the Section Physical Sensors)

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(a) Setup of our system; (b) data acquisition: RGB image (top) and depth data (bottom) from two Kinect sensors; (c) template SCAPEmodel; (d) reconstructed SCAPE model (top) and projection (bottom); the yellow shadows are the projections of our reconstructed model. Full article ">Figure 2
(a) SCAPE model; (b) scanned point cloud; (c) template SCAPE model. Full article ">Figure 3
Registration results: (a) registration results using our calibration method; (b) registration results using stereo calibration in the calibration toolbox of MATLAB. Full article ">Figure 4
Impact of our temporal term: the yellow shadow on these four pictures is the projection of our model transformed with the estimated pose parameters. (a) projection of the reconstructed model for the left camera without our temporal term; (b) projection of our reconstructed model for the left camera with our temporal term; (c) projection of the reconstructed model for the left camera without our temporal term; (d) projection of our reconstructed model for the left camera with our temporal term. Full article ">Figure 5
Results of the motion capture: Column 1 shows the RGB images from the left camera (for brevity, we do not show the RGB images from the right camera). Column 2 shows our results in the front view. Column 3 shows the results from viewpoints different from Column 1. Full article ">Figure 6
Comparison against Kinect: (a) skeletons from Kinect; (b,c) skeletons of our reconstructed model projections to the RGB images from the left camera and the right camera; the red dots are the joints of the model, and blue dots in (b,c) are the centers of the corresponding bones. Full article ">Figure 7
Comparison against [<a href="#B15-sensors-15-24297" class="html-bibr">15</a>]: (a,b) the reconstructed SCAPE model’s projection respectively using the depth data from the left and the right camera with the method of [<a href="#B15-sensors-15-24297" class="html-bibr">15</a>]; (c,d) our reconstructed model’s projection using the depth data from the left and the right camera at the same time. Full article ">Figure 8
OptiTrack system setup for ground truth data. Full article ">Figure 9
Quantitative comparison of the average reconstruction error. The vertical axis represents the error of joint position discrepancy, and its coordinate unit is mm. The horizontal axis successively shows the name of all of the joints, except that Column 14 shows the average error. Full article ">Figure 10
Difficult poses. Figures on the top are RGB images from the left camera. Figures on the bottom are reconstructed models from the front view. Full article ">Figure 11
Skeletons of difficult poses obtained by the OptiTrack system, Xu’s monocular setup [<a href="#B15-sensors-15-24297" class="html-bibr">15</a>], the Kinect SDK [<a href="#B20-sensors-15-24297" class="html-bibr">20</a>] and our two-Kinect system. The first column shows the RGB images from the left camera. Column 2 shows a comparison of our reconstructed poses and that from the OptiTrack system, where the red skeletons are from the OptiTrack system and the blue are our reconstructed results. Red skeletons in Column 3 are also from the OptiTrack system, and the black ones are derived by Xu’s method [<a href="#B15-sensors-15-24297" class="html-bibr">15</a>]. In Column 4, the green skeletons are obtained from the Kinect SDK, while the red are from the OptiTrack system. Full article ">

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Open AccessArticle

An Enhanced Error Model for EKF-Based Tightly-Coupled Integration of GPS and Land Vehicle’s Motion Sensors

by Tashfeen B. Karamat, Mohamed M. Atia and Aboelmagd Noureldin

Sensors 2015, 15(9), 24269-24296; https://doi.org/10.3390/s150924269 - 22 Sep 2015

Cited by 17 | Viewed by 6638

Abstract

Reduced inertial sensor systems (RISS) have been introduced by many researchers as a low-cost, low-complexity sensor assembly that can be integrated with GPS to provide a robust integrated navigation system for land vehicles. In earlier works, the developed error models were simplified based [...] Read more.

Reduced inertial sensor systems (RISS) have been introduced by many researchers as a low-cost, low-complexity sensor assembly that can be integrated with GPS to provide a robust integrated navigation system for land vehicles. In earlier works, the developed error models were simplified based on the assumption that the vehicle is mostly moving on a flat horizontal plane. Another limitation is the simplified estimation of the horizontal tilt angles, which is based on simple averaging of the accelerometers’ measurements without modelling their errors or tilt angle errors. In this paper, a new error model is developed for RISS that accounts for the effect of tilt angle errors and the accelerometer’s errors. Additionally, it also includes important terms in the system dynamic error model, which were ignored during the linearization process in earlier works. An augmented extended Kalman filter (EKF) is designed to incorporate tilt angle errors and transversal accelerometer errors. The new error model and the augmented EKF design are developed in a tightly-coupled RISS/GPS integrated navigation system. The proposed system was tested on real trajectories’ data under degraded GPS environments, and the results were compared to earlier works on RISS/GPS systems. The findings demonstrated that the proposed enhanced system introduced significant improvements in navigational performance. Full article

(This article belongs to the Special Issue Advances on Resources Management for Multi-Platform Infrastructures)

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743 KiB

Open AccessArticle

A Lateral Differential Resonant Pressure Microsensor Based on SOI-Glass Wafer-Level Vacuum Packaging

by Bo Xie, Yonghao Xing, Yanshuang Wang, Jian Chen, Deyong Chen and Junbo Wang

Sensors 2015, 15(9), 24257-24268; https://doi.org/10.3390/s150924257 - 21 Sep 2015

Cited by 23 | Viewed by 6009

Abstract

This paper presents the fabrication and characterization of a resonant pressure microsensor based on SOI-glass wafer-level vacuum packaging. The SOI-based pressure microsensor consists of a pressure-sensitive diaphragm at the handle layer and two lateral resonators (electrostatic excitation and capacitive detection) on the device [...] Read more.

This paper presents the fabrication and characterization of a resonant pressure microsensor based on SOI-glass wafer-level vacuum packaging. The SOI-based pressure microsensor consists of a pressure-sensitive diaphragm at the handle layer and two lateral resonators (electrostatic excitation and capacitive detection) on the device layer as a differential setup. The resonators were vacuum packaged with a glass cap using anodic bonding and the wire interconnection was realized using a mask-free electrochemical etching approach by selectively patterning an Au film on highly topographic surfaces. The fabricated resonant pressure microsensor with dual resonators was characterized in a systematic manner, producing a quality factor higher than 10,000 (~6 months), a sensitivity of about 166 Hz/kPa and a reduced nonlinear error of 0.033% F.S. Based on the differential output, the sensitivity was increased to two times and the temperature-caused frequency drift was decreased to 25%. Full article

(This article belongs to the Section Physical Sensors)

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716 KiB

Open AccessArticle

Cell Selection Game for Densely-Deployed Sensor and Mobile Devices In 5G Networks Integrating Heterogeneous Cells and the Internet of Things

by Lusheng Wang, Yamei Wang, Zhizhong Ding and Xiumin Wang

Sensors 2015, 15(9), 24230-24256; https://doi.org/10.3390/s150924230 - 18 Sep 2015

Cited by 13 | Viewed by 6174

Abstract

With the rapid development of wireless networking technologies, the Internet of Things and heterogeneous cellular networks (HCNs) tend to be integrated to form a promising wireless network paradigm for 5G. Hyper-dense sensor and mobile devices will be deployed under the coverage of heterogeneous [...] Read more.

With the rapid development of wireless networking technologies, the Internet of Things and heterogeneous cellular networks (HCNs) tend to be integrated to form a promising wireless network paradigm for 5G. Hyper-dense sensor and mobile devices will be deployed under the coverage of heterogeneous cells, so that each of them could freely select any available cell covering it and compete for resource with others selecting the same cell, forming a cell selection (CS) game between these devices. Since different types of cells usually share the same portion of the spectrum, devices selecting overlapped cells can experience severe inter-cell interference (ICI). In this article, we study the CS game among a large amount of densely-deployed sensor and mobile devices for their uplink transmissions in a two-tier HCN. ICI is embedded with the traditional congestion game (TCG), forming a congestion game with ICI (CGI) and a congestion game with capacity (CGC). For the three games above, we theoretically find the circular boundaries between the devices selecting the macrocell and those selecting the picocells, indicated by the pure strategy Nash equilibria (PSNE). Meanwhile, through a number of simulations with different picocell radii and different path loss exponents, the collapse of the PSNE impacted by severe ICI (i.e., a large number of picocell devices change their CS preferences to the macrocell) is profoundly revealed, and the collapse points are identified. Full article

(This article belongs to the Section Sensor Networks)

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Scenario with multiple picocells and densely-deployed devices in a single macrocell. Full article ">Figure 2
System model. Each picocell holds a circular boundary (i.e., the azure dashed circle) indicating the PSNE. Device A is inside the boundary, so it transmits to the picocell and interferes with the macrocell. Although Device B is within the edge of the picocell, it is outside of the dashed circle, so it selects the macrocell and interferes with the picocell. Full article ">Figure 3
Two-dimensional case of the traditional congestion game (TCG) for the proof of Theorem 1. Full article ">Figure 4
Monotonicity of payoff functions in Theorems 2 and 3. Obtained by setting <math display="inline"> <mrow> <msub> <mi>B</mi> <mi>i</mi> </msub> <mo>=</mo> <mn>2</mn> <mo>/</mo> <mn>3</mn> <msub> <mi>B</mi> <mn>0</mn> </msub> </mrow> </math>, <math display="inline"> <mrow> <msub> <mi>R</mi> <mi>i</mi> </msub> <mo>=</mo> <mn>300</mn> </mrow> </math> m, <math display="inline"> <mrow> <mi>w</mi> <mo>=</mo> <mn>3</mn> <mo>×</mo> <msup> <mn>10</mn> <mn>6</mn> </msup> </mrow> </math> and other parameters commonly configured as in <a href="#sec5-sensors-15-24230" class="html-sec">Section 5</a>, for a scenario with one picocell located within the macrocell. Curves are obtained by searching for the PSNE, so the number of devices selecting the picocell gradually decreases during iterations. (a) Cost in Theorem 2; (b) capacity in Theorem 3. Full article ">Figure 5
Verification of the theorems. (a) Theorem 1; (b) Theorem 2; (c) Theorem 3. Full article ">Figure 6
Impact of ICI on CS preference and spatial spectral efficiency using TCG and the congestion game with ICI (CGI). (a) Path Loss 2 (free space); (b) Path Loss 2 (free space); (c) Path Loss 3 (suburbs); (d) Path Loss 3 (suburbs); (e) Path Loss 4 (downtown); (f) Path Loss 4 (downtown). Full article ">Figure 7
Impact of ICI on CS preference and spatial spectral efficiency using CGC-fractional frequency reuse (FFR) and CGC-orthogonal frequency division (OFD). (a) Path Loss 2 (free space); (b) Path Loss 2 (free space); (c) Path Loss 3 (suburbs); (d) Path Loss 3 (suburbs); (e) Path Loss 4 (downtown); (f) Path Loss 4 (downtown). Full article ">Figure 8
The polar coordinate systems for calculating the ICI. (a) To calculate x; (b) to calculate y. Full article ">

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Open AccessArticle

A Fiber Bragg Grating Sensing Based Triaxial Vibration Sensor

by Tianliang Li, Yuegang Tan, Yi Liu, Yongzhi Qu, Mingyao Liu and Zude Zhou

Sensors 2015, 15(9), 24214-24229; https://doi.org/10.3390/s150924214 - 18 Sep 2015

Cited by 27 | Viewed by 6553

Abstract

A fiber Bragg grating (FBG) sensing based triaxial vibration sensor has been presented in this paper. The optical fiber is directly employed as elastomer, and the triaxial vibration of a measured body can be obtained by two pairs of FBGs. A model of [...] Read more.

A fiber Bragg grating (FBG) sensing based triaxial vibration sensor has been presented in this paper. The optical fiber is directly employed as elastomer, and the triaxial vibration of a measured body can be obtained by two pairs of FBGs. A model of a triaxial vibration sensor as well as decoupling principles of triaxial vibration and experimental analyses are proposed. Experimental results show that: sensitivities of 86.9 pm/g, 971.8 pm/g and 154.7 pm/g for each orthogonal sensitive direction with linearity are separately 3.64%, 1.50% and 3.01%. The flat frequency ranges reside in 20–200 Hz, 3–20 Hz and 4–50 Hz, respectively; in addition, the resonant frequencies are separately 700 Hz, 40 Hz and 110 Hz in the x/y/z direction. When the sensor is excited in a single direction vibration, the outputs of sensor in the other two directions are consistent with the outputs in the non-working state. Therefore, it is effectively demonstrated that it can be used for three-dimensional vibration measurement. Full article

(This article belongs to the Section Physical Sensors)

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4194 KiB

Open AccessArticle

A Self-Adaptive Dynamic Recognition Model for Fatigue Driving Based on Multi-Source Information and Two Levels of Fusion

by Wei Sun, Xiaorui Zhang, Srinivas Peeta, Xiaozheng He, Yongfu Li and Senlai Zhu

Sensors 2015, 15(9), 24191-24213; https://doi.org/10.3390/s150924191 - 18 Sep 2015

Cited by 24 | Viewed by 5574

Abstract

To improve the effectiveness and robustness of fatigue driving recognition, a self-adaptive dynamic recognition model is proposed that incorporates information from multiple sources and involves two sequential levels of fusion, constructed at the feature level and the decision level. Compared with existing models, [...] Read more.

To improve the effectiveness and robustness of fatigue driving recognition, a self-adaptive dynamic recognition model is proposed that incorporates information from multiple sources and involves two sequential levels of fusion, constructed at the feature level and the decision level. Compared with existing models, the proposed model introduces a dynamic basic probability assignment (BPA) to the decision-level fusion such that the weight of each feature source can change dynamically with the real-time fatigue feature measurements. Further, the proposed model can combine the fatigue state at the previous time step in the decision-level fusion to improve the robustness of the fatigue driving recognition. An improved correction strategy of the BPA is also proposed to accommodate the decision conflict caused by external disturbances. Results from field experiments demonstrate that the effectiveness and robustness of the proposed model are better than those of models based on a single fatigue feature and/or single-source information fusion, especially when the most effective fatigue features are used in the proposed model. Full article

(This article belongs to the Section Physical Sensors)

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635 KiB

Open AccessArticle

Continuous-Wave Stimulated Emission Depletion Microscope for Imaging Actin Cytoskeleton in Fixed and Live Cells

by Bhanu Neupane, Tao Jin, Liliana F. Mellor, Elizabeth G. Loboa, Frances S. Ligler and Gufeng Wang

Sensors 2015, 15(9), 24178-24190; https://doi.org/10.3390/s150924178 - 18 Sep 2015

Cited by 10 | Viewed by 6543

Abstract

Stimulated emission depletion (STED) microscopy provides a new opportunity to study fine sub-cellular structures and highly dynamic cellular processes, which are challenging to observe using conventional optical microscopy. Using actin as an example, we explored the feasibility of using a continuous wave (CW)-STED [...] Read more.

Stimulated emission depletion (STED) microscopy provides a new opportunity to study fine sub-cellular structures and highly dynamic cellular processes, which are challenging to observe using conventional optical microscopy. Using actin as an example, we explored the feasibility of using a continuous wave (CW)-STED microscope to study the fine structure and dynamics in fixed and live cells. Actin plays an important role in cellular processes, whose functioning involves dynamic formation and reorganization of fine structures of actin filaments. Frequently used confocal fluorescence and STED microscopy dyes were employed to image fixed PC-12 cells (dyed with phalloidin- fluorescein isothiocyante) and live rat chondrosarcoma cells (RCS) transfected with actin-green fluorescent protein (GFP). Compared to conventional confocal fluorescence microscopy, CW-STED microscopy shows improved spatial resolution in both fixed and live cells. We were able to monitor cell morphology changes continuously; however, the number of repetitive analyses were limited primarily by the dyes used in these experiments and could be improved with the use of dyes less susceptible to photobleaching. In conclusion, CW-STED may disclose new information for biological systems with a proper characteristic length scale. The challenges of using CW-STED microscopy to study cell structures are discussed. Full article

(This article belongs to the Special Issue Fluorescent Probes for Intracellular Imaging and Super Resolution Microscopy)

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Full article ">Figure 1
CW-STED microscopy. (A) Schematic of our home-built CW-STED microscope; (B) Confocal images of 45 nm FITC-doped polystyrene nanoparticles; (C) CW-STED image in the same area. The 2 µm scale bar applies to both images; (D) and (E) Representative cross-sections of the confocal and CW-STED images of the 45 nm particles. Full article ">Figure 2
Confocal and CW-STED images of fixed PC-12 cells stained with phalloidin-FITC. (A) Confocal image of PC-12 cell with different sized neurites; (B) Expanded views of three selected neurites of different diameters; B and B’ refer to confocal and STED images, respectively; (C) A pair of confocal and STED images of another typical neurite showing an increase in geometric resolution for the STED image. Full article ">Figure 3
Confocal and STED images of live rat chondrocyte cells transfected with green fluorescent protein. (A) Confocal image of chondrocyte cells; (B) Confocal image of selected cells; (C–F) STED images of the same cells at different times. The scale bar in (B) also applies to (C–F). Full article ">Figure 4
Fluorescence intensity in CW-STED imaging. (A) Comparison of confocal and STED image intensity. The intensity was measured from the maximum intensity of five cell features with similar intensities in <a href="#sensors-15-24178-f003" class="html-fig">Figure 3</a>. The error bar is calculated from the standard deviation of the intensity of the five cell features; (B) Photobleaching of STED image upon multiple exposures to the depletion laser beam. Black curve: the average intensity of the whole image in <a href="#sensors-15-24178-f003" class="html-fig">Figure 3</a>. The other five curves: the maximum intensity of five selected cell features in <a href="#sensors-15-24178-f003" class="html-fig">Figure 3</a> at different exposures. The total image intensity decays smoothly while the cell feature intensity fluctuated slightly because of the movement of the live cell. Full article ">

888 KiB

Open AccessArticle

Evaluation of Content-Matched Range Monitoring Queries over Moving Objects in Mobile Computing Environments

by HaRim Jung, MoonBae Song, Hee Yong Youn and Ung Mo Kim

Sensors 2015, 15(9), 24143-24177; https://doi.org/10.3390/s150924143 - 18 Sep 2015

Cited by 7 | Viewed by 5201

Abstract

A content-matched (CM) rangemonitoring query overmoving objects continually retrieves the moving objects (i) whose non-spatial attribute values are matched to given non-spatial query values; and (ii) that are currently located within a given spatial query range. In this paper, we propose a new [...] Read more.

A content-matched (CM) rangemonitoring query overmoving objects continually retrieves the moving objects (i) whose non-spatial attribute values are matched to given non-spatial query values; and (ii) that are currently located within a given spatial query range. In this paper, we propose a new query indexing structure, called the group-aware query region tree (GQR-tree) for efficient evaluation of CMrange monitoring queries. The primary role of the GQR-tree is to help the server leverage the computational capabilities of moving objects in order to improve the system performance in terms of the wireless communication cost and server workload. Through a series of comprehensive simulations, we verify the superiority of the GQR-tree method over the existing methods. Full article

(This article belongs to the Section Sensor Networks)

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2003 KiB

Open AccessArticle

Self-Adaptive Strategy Based on Fuzzy Control Systems for Improving Performance in Wireless Sensors Networks

by Vicente Hernández Díaz, José-Fernán Martínez, Néstor Lucas Martínez and Raúl M. Del Toro

Sensors 2015, 15(9), 24125-24142; https://doi.org/10.3390/s150924125 - 18 Sep 2015

Cited by 8 | Viewed by 6188

Abstract

The solutions to cope with new challenges that societies have to face nowadays involve providing smarter daily systems. To achieve this, technology has to evolve and leverage physical systems automatic interactions, with less human intervention. Technological paradigms like Internet of Things (IoT) and [...] Read more.

The solutions to cope with new challenges that societies have to face nowadays involve providing smarter daily systems. To achieve this, technology has to evolve and leverage physical systems automatic interactions, with less human intervention. Technological paradigms like Internet of Things (IoT) and Cyber-Physical Systems (CPS) are providing reference models, architectures, approaches and tools that are to support cross-domain solutions. Thus, CPS based solutions will be applied in different application domains like e-Health, Smart Grid, Smart Transportation and so on, to assure the expected response from a complex system that relies on the smooth interaction and cooperation of diverse networked physical systems. The Wireless Sensors Networks (WSN) are a well-known wireless technology that are part of large CPS. The WSN aims at monitoring a physical system, object, (e.g., the environmental condition of a cargo container), and relaying data to the targeted processing element. The WSN communication reliability, as well as a restrained energy consumption, are expected features in a WSN. This paper shows the results obtained in a real WSN deployment, based on SunSPOT nodes, which carries out a fuzzy based control strategy to improve energy consumption while keeping communication reliability and computational resources usage among boundaries. Full article

(This article belongs to the Special Issue Cyber-Physical Systems)

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1258 KiB

Open AccessArticle

Inline Measurement of Particle Concentrations in Multicomponent Suspensions using Ultrasonic Sensor and Least Squares Support Vector Machines

by Xiaobin Zhan, Shulan Jiang, Yili Yang, Jian Liang, Tielin Shi and Xiwen Li

Sensors 2015, 15(9), 24109-24124; https://doi.org/10.3390/s150924109 - 18 Sep 2015

Cited by 13 | Viewed by 5896

Abstract

This paper proposes an ultrasonic measurement system based on least squares support vector machines (LS-SVM) for inline measurement of particle concentrations in multicomponent suspensions. Firstly, the ultrasonic signals are analyzed and processed, and the optimal feature subset that contributes to the best model [...] Read more.

This paper proposes an ultrasonic measurement system based on least squares support vector machines (LS-SVM) for inline measurement of particle concentrations in multicomponent suspensions. Firstly, the ultrasonic signals are analyzed and processed, and the optimal feature subset that contributes to the best model performance is selected based on the importance of features. Secondly, the LS-SVM model is tuned, trained and tested with different feature subsets to obtain the optimal model. In addition, a comparison is made between the partial least square (PLS) model and the LS-SVM model. Finally, the optimal LS-SVM model with the optimal feature subset is applied to inline measurement of particle concentrations in the mixing process. The results show that the proposed method is reliable and accurate for inline measuring the particle concentrations in multicomponent suspensions and the measurement accuracy is sufficiently high for industrial application. Furthermore, the proposed method is applicable to the modeling of the nonlinear system dynamically and provides a feasible way to monitor industrial processes. Full article

(This article belongs to the Section Physical Sensors)

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1036 KiB

Open AccessArticle

Three-Component Decomposition Based on Stokes Vector for Compact Polarimetric SAR

by Hanning Wang, Zhimin Zhou, John Turnbull, Qian Song and Feng Qi

Sensors 2015, 15(9), 24087-24108; https://doi.org/10.3390/s150924087 - 18 Sep 2015

Cited by 11 | Viewed by 5204

Abstract

In this paper, a three-component decomposition algorithm is proposed for processing compact polarimetric SAR images. By using the correspondence between the covariance matrix and the Stokes vector, three-component scattering models for CTLR and DCP modes are established. The explicit expression of decomposition results [...] Read more.

In this paper, a three-component decomposition algorithm is proposed for processing compact polarimetric SAR images. By using the correspondence between the covariance matrix and the Stokes vector, three-component scattering models for CTLR and DCP modes are established. The explicit expression of decomposition results is then derived by setting the contribution of volume scattering as a free parameter. The degree of depolarization is taken as the upper bound of the free parameter, for the constraint that the weighting factor of each scattering component should be nonnegative. Several methods are investigated to estimate the free parameter suitable for decomposition. The feasibility of this algorithm is validated by AIRSAR data over San Francisco and RADARSAT-2 data over Flevoland. Full article

(This article belongs to the Section Remote Sensors)

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Sensors, Volume 15, Issue 9 (September 2015) – 183 articles , Pages 20945-24680

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