Structural Properties

Ordered (SBA-15) and disordered (KIL-2) mesoporous silica supports have been synthesized and used for incorporation of titania with different Ti/Si molar ratios (1/2, 1/1, 2/1) via sol–gel impregnation method. Titanium isopropoxide and aqueous titania sol prepared by low-temperature sol–gel processing were used as a source of titania. Characterization by powder X-ray diffraction (XRD), nitrogen sorption measurements, scanning electron microscopy (SEM) and UV–vis–NIR diffuse reflectance spectroscopy (DRS) has been carried out to investigate the chemical framework and morphology of powders. The photocatalytic degradation of isopropanol in the gaseous medium was selected as a probe reaction to test the photoactivity of powders and to verify the potential application of these materials for air remediation. It was found that the titania source, Ti/Si molar ratio and the type of silica support influenced the functional properties of the material, which were evaluated by adsorption capacity and photocatalytic activity in the gas–solid reactor. The adsorption capacity of isopropanol was the highest in the presence of the SBA-15-supported materials. The photoactivity results indicated that the powders which were prepared using SBA-15 as a silica support and a Ti/Si molar ratio of 1/1 were the most active towards isopropanol oxidation monitored in situ by FT-IR spectroscopy.

Detailed numerical results for the structural properties of three-dimensional classical Coulomb clusters confined in a spherical parabolic trap are presented. Based on extensive high accuracy computer simulations the shell configurations and energies for particle numbers in the range $2 \le N\le 160$ are reported. Further, the mean shell radii and shell widths are calculated.

The opportunities provided by the use of Carbon Fiber Reinforced Polymer (CFRP) composites for the seismic repair of reinforced concrete (RC) structures were assessed on a full-scale dual system subjected to pseudodynamic tests in the ELSA laboratory. The aim of the CFRP ...

Artificial intelligence techniques useful in diagnosis can be classified into eight categories. Among these techniques the integrated diagnostic techniques are often presented as the most efficient to resolve practical problems. This approach may lack however some flexibility to be applied in many application domains, when the role played by users takes an important part of the diagnosis process. Hypertext systems

Network robustness and network reliability are important issues in the design of Internet Service Providers’ topologies. In this paper, we examine the structural characteristics of network topologies that affect robustness and reliability. We examine the interplay between the structural characteristics of network topologies and the resource capacity over-provisioning strategies when the network breakdowns subject to practical constraints (router technology) and economic considerations (link costs). We study the robustness of the Internet connectivity under node intentional harmful attack using two attacks strategies: static degree-based and static load-based. We find that the robustness of network topologies is affected by the variation of their structural characteristics. In our proposed approach, we show that highly-heterogeneous topologies have less robustness compared with lightly-heterogeneous topologies. The observations from the robustness study provide us useful insights for proposing multiple efficient preventive resource capacity over-provisioning strategies for mitigation of intentional attacks. The proposed strategies utilize the structural properties by calculating the excess traffic in case of single global cascading failure for each node and measure its influence on the other nodes as well as locally. The results show that our proposed strategies can significantly enhance the robustness and increase the resilience of network topology. We also show that highly-heterogeneous topologies have high resilience compared with lightly-heterogeneous topologies. By using real data from the Sprint network at the router level, we provide further empirical evidence in support of the proposed approach.

In this paper, we report structural and optical properties of nanocrystalline chromium (Cr) doped ZnS particle, which have been synthesized by co-precipitation method. The structural properties of ZnS:Cr nanoparticles have been characterized by X-ray diffraction (XRD) analysis. The XRD patterns show hexagonal structure in nanoparticles without any additional phase. The mean crystallite size calculated from the XRD patterns has been found in the range 2.45-1.50 nm with the increase in molar concentration of doping agent. Absorption spectra have been obtained using UV-Vis spectrophotometer to find the optical direct band gap. The obtained values have been founded to being range 3.82-4.42 eV. It was also found that optical band gap (Eg) increases with the increase in molar concentration of doping agent is attributed to size quantization effect due to the small size of the particles.

Hydroxyapatite (HA) - Ca(10)(PO(4))(6)(OH)(2) is a basic inorganic model component of hard biological tissues, such as bones and teeth. The significant property of HA is its ability to exchange Ca(2+) ions, which influences crystallinity, physico-chemical and biological properties of modified hydroxyapatite materials. In this work, FTIR, Raman spectroscopy, XRD. SEM and EDS techniques were used to determine thermal stability, chemical and phase composition of Mn containing hydroxyapatite (MnHA). Described methods confirmed thermal decomposition and phase transformation of MnHA to alpha TCP, beta TCP and formation of Mn(3)O(4) depending on sintering temperature and manganese content. In vitro biological evaluation of Mn-modified HA ceramics was also performed using human osteoblast cells. (C) 2010 Elsevier B.V. All rights reserved.

We report a detailed study of the electronic and structural properties of the 39K superconductor \mgbtwo and of several related systems of the same family, namely \mgalbtwo, \bebtwo, \casitwo and \cabesi. Our calculations, which include zone-center phonon frequencies and transport properties, are performed within the local density approximation to the density functional theory, using the full-potential linearized augmented plane wave

ABSTRACT This paper develops a mathematical model to derive the optimal periodical preventive maintenance (PM) policy for a leased facility with Weibull life-time. Within a lease period, any failures of the facility are rectified by minimal repairs and a penalty may occur to the lessor when the time required to perform a minimal repair exceeds a reasonable time limit. To reduce failures of the facility, additional PM actions are carried out periodically during the lease period. When the life-time distribution of a product is Weibull, the optimal number of PM actions and the corresponding maintenance degrees are derived such that the expected total maintenance cost is minimized. The structural properties of the optimal policy are investigated and an efficient algorithm is provided to search for the optimal policy. Finally, numerical examples are provided to illustrate the features of the proposed model.

In this paper, indium tin oxide (ITO) thin films were prepared by unipolar and bipolar direct current (DC)-pulsed magnetron sputtering in a mixture of argon and oxygen onto unheated glass substrates. The target of ITO with 10 wt.% tin is used. The influences of polar modes (unipolar and bipolar); output frequencies (0 to 33 kHz); and times and off times on the optical, electrical, and structural properties of ITO films are investigated. The correlations between the deposition parameters and the film properties are discussed. It is found that the resistivity with 10−3 Θ-cm and transmittance with ≥90% of amorphous ITO films can be prepared by the reactive bipolar DC-pulsed sputtering with t on− between 45 µs and 85 µs (i.e., t on−/t on+ is 9–17), and t on+, t off− and t off+ are constant at 5 µs, 10 µs, and 5 µs, respectively. An optimal condition, based on the polar mode and frequency of reactive-pulsed sputtering, for obtaining the high transmittance and low resistivity of ITO films is suggested.