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Considering the temporality of microbial fermentation process, a soft-sensing modeling method based on Continuous Hidden Markov Model (CHMM) for microbial fermentation process is proposed. Firstly, in order to improve the robustness of... more
Considering the temporality of microbial fermentation process, a soft-sensing modeling method based on Continuous Hidden Markov Model (CHMM) for microbial fermentation process is proposed. Firstly, in order to improve the robustness of CHMM, multi-observation training sample sequences are used to train the CHMM. And the modified Baum-Welch parameters re-estimation formula is used to optimize the parameters of CHMM. Then, the new observation vector is inputed to the CHMM model library and the emission probability of each CHMM in the model library is calculated using the Viterbi Algorithm. Finally, the soft-sensing result can be obtained by computing the weighted average. The model is applied to an erythromycin fermentation process, and case studies show that the new approach has better performance compared to the conventional method based on ANN.
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Thermal reaction rate constants have been determined for the reactions Cl+HI and Cl+HBr in the temperature range 220–400 °K. The rates vary slowly with temperature. For Cl+HI the effective reaction cross section reaches a maximum of 31 Å2... more
Thermal reaction rate constants have been determined for the reactions Cl+HI and Cl+HBr in the temperature range 220–400 °K. The rates vary slowly with temperature. For Cl+HI the effective reaction cross section reaches a maximum of 31 Å2 near 300 °K. A tentative reaction model is proposed in which the attacking halogen atom is attracted to the halogen end of the hydrogen halide and then rotation of the hydrogen, with little or no activation energy, completes the reaction.
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In an irregular sea, waves of different wavenumbers interact nonlinearly and give rise to second order forces at the sum and difference frequencies. A moored or dynamically positioned vessel (ship or platform) can be induced to perform... more
In an irregular sea, waves of different wavenumbers interact nonlinearly and give rise to second order forces at the sum and difference frequencies. A moored or dynamically positioned vessel (ship or platform) can be induced to perform slow drift oscillations at the difference frequencies. To study the slow motion in a narrow- banded sea, the methods of multiple scales and matched asymptotics are combined. It is shown in general terms that slow drift motion is accompanied by long waves. The range of applicability of a formula for the wave force by Newman is discussed. An exception to the formula is a long body in beam seas with a small clearance under its keel. Some recent results for this case are presented, exhibiting resonant motion.
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ABSTRACT Approximate equations for long waves are derived under assumptions similar to those of Boussinesg and Korteweg and deVries. Numerical studies are performed using the method of characteristics. Four cases are investigated (1)... more
ABSTRACT Approximate equations for long waves are derived under assumptions similar to those of Boussinesg and Korteweg and deVries. Numerical studies are performed using the method of characteristics. Four cases are investigated (1) solitary wave on a beach, (2) solitary wave on a shelf, (3) periodic waves generated in a wave tank of constant depth, (4) periodic wave on a shelf. It is discovered that complicated disintegration and evolution appear due to combined effects of nonlinearity and dispersion. Experimental evidence is presented. (Author)
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Since the speed of sound in water is much greater than that of the surface gravity waves, acoustic signals can be used for early warning of tsunamis. We simplify existing works by treating the sound wave alone without the much slower... more
Since the speed of sound in water is much greater than that of the surface gravity waves, acoustic signals can be used for early warning of tsunamis. We simplify existing works by treating the sound wave alone without the much slower gravity wave, and derive a two-dimensional theory for signals emanating from a fault of finite length. Under the assumptions of a slender fault and constant sea depth, the asymptotic technique of multiple scales is applied to obtain analytical results. The modal envelopes of the two-dimensional sound waves are found to be governed by the Schrödinger equation and are solved explicitly. An approximate method is described for the inverse estimation of fault properties from the pressure record at a distant hydrophone.
Research Interests: Engineering, Geology, Acoustics, Fluid Mechanics, Mathematical Sciences, and 2 moreModal and Hydrophone(Modal and Hydrophone)
(Modal and Hydrophone)
With a general pressure gradient the boundary layer equations can be solved by a variety of modern numerical means. An alternative which can still be employed to simplify calculations is the momentum integral method of Karman. We explain... more
With a general pressure gradient the boundary layer equations can be solved by a variety of modern numerical means. An alternative which can still be employed to simplify calculations is the momentum integral method of Karman. We explain this method for a transient boundary layer along the x-axis forced by an unsteady pressure gradient outside. This pressure gradient can be due to some unsteady and nonuniform flow such as waves or gust.
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Motivated by potential applications for offshore airports supported on vertical piles, we report a theory of wave diffraction by a periodic array of circular cylinders. The simple case of normal incidence on a rectangular array is studied... more
Motivated by potential applications for offshore airports supported on vertical piles, we report a theory of wave diffraction by a periodic array of circular cylinders. The simple case of normal incidence on a rectangular array is studied here, which is equivalent to a line array along the centre of a long channel. An asymptotic theory is developed for cylinders much smaller than the incident wavelength, which is comparable to the cylinder spacing. Focus is on Bragg resonance near which scattering is strong. A combination of the method of multiple scales and the Bloch theorem leads to simple evolution equations coupling the wave envelopes. Dispersion of transient wave envelopes is investigated. Scattering of detuned waves by a large but finite number of cylinders is investigated for frequencies in and outside the band gap. Quantitative accuracy is assessed by comparisons with numerical computations via finite elements. The analytical theory prepares the ground for nonlinear studies ...
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Many papers have been devoted to nonlinear waves on a thin layer of viscous fluid flowing down an incline at low to moderate Reynolds numbers (see Chang 1994 for a survey). Motivated by interests in chemical engineering, surface tension... more
Many papers have been devoted to nonlinear waves on a thin layer of viscous fluid flowing down an incline at low to moderate Reynolds numbers (see Chang 1994 for a survey). Motivated by interests in chemical engineering, surface tension is emphasized in past studies where the Weber number W e is ususally assumed to be large W e = O(∈—2) where ∈ = is a small parameter denoting the depth-to-wavelength ratio. Among the few papers on high Reynolds numbers, the boundary layer approximation to O(∈2) accuracy and the momentum integral method are used for analytical convenience. Due to the complexity of these nonlinear evolution equations, most reported studies concentrate on permanent (or stationary) waves which propagate at a constant speed without changing form. However in these papers there exist inconsistencies since pressure is taken to be only hydrostatic which implies omission of 0(e 2) terms in the transverse momentum equation. A consistent second order theory has been worked out for large Reynolds numbers and small-to-moderate surface tension (Lee, 1995, Lee & Mei, 1995).
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I. Some initial value problems are studied regarding the radiation and scattering of gravity waves by finite bodies in an infinitely deep ocean. Emphasis is placed on the case where a finite number of thin plates lie on a vertical line,... more
I. Some initial value problems are studied regarding the radiation and scattering of gravity waves by finite bodies in an infinitely deep ocean. Emphasis is placed on the case where a finite number of thin plates lie on a vertical line, for which the general solution is obtained by transforming the boundary value problem to one of the Riemann-Hilbert type. Explicit investigations are made for the large time behavior of the free surface elevation for the case of a rolling plate, and for the Cauchy-Poisson problems in the presence of a stationary plate. By taking the limit as t → ∞, the steady state solution is derived for a harmonic point pressure acting on the free surface near a vertical barrier. Finally a formal asymptotic representation of the free surface elevation is given for large time when the geometry of the submerged bodies is arbitrary. II. The subject gravity waves in the two dimensional flow of a vertically stratified fluid is investigated with regard to the dynamic eff...
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Let us model the effect of turbulence by a constant eddy viscosity. Assume that convective inertia is negligible, the seabed is horizontal and vertical shear is important, the governing equation in a shallow sea are ∂u ∂x + ∂v ∂y + ∂w ∂z... more
Let us model the effect of turbulence by a constant eddy viscosity. Assume that convective inertia is negligible, the seabed is horizontal and vertical shear is important, the governing equation in a shallow sea are ∂u ∂x + ∂v ∂y + ∂w ∂z = 0 (7.4.1) ∂u ∂t − fv = −g ∂η ∂x + ν ∂ 2 u ∂z 2 (7.4.2) ∂v ∂t + fu = −g ∂η ∂z + ν ∂ 2 u ∂z 2 (7.4.3) The boundary conditons are u = v = w = 0, z = −h (7.4.4) µ ∂u ∂z = τ S x , µ ∂v ∂z = τ S y (7.4.5) As in a thin boundary layer, the vertical shear dominates. Integrating over depth and defining the horizontal transport rates,
The spreading of a finite mass of paint, paper pulp, mud or lava on an inclined plane is of interest to a variety of industrial and geological problems. For mud modeled as a Binghamplastic non-Newtonian fluid, Liu & Mei (1989) solved the... more
The spreading of a finite mass of paint, paper pulp, mud or lava on an inclined plane is of interest to a variety of industrial and geological problems. For mud modeled as a Binghamplastic non-Newtonian fluid, Liu & Mei (1989) solved the equation similar to (2.3.22) numerically. An analytical solution for Herschel-Bulkley fluid was given later by Huang & Garcia (1997). We modify their theories for the simpler case of Newtonion fluid here. The free surface of a thin layer is expected to flatten in time over most of the profile, but it should steepen near the downstream front where the spatial derivative is much more important than elsewhere. Let us study the problem by dividing the total fluid extent into two: the far field not too close to the steep front and the near field around the front.
Nuclear power plants are often located near a large lake so that cold water can be withdrawn to cool the engines. If the lake is thermally stratified so that there is apprciable temperature gradient vertically. Cold water can be withdrawn... more
Nuclear power plants are often located near a large lake so that cold water can be withdrawn to cool the engines. If the lake is thermally stratified so that there is apprciable temperature gradient vertically. Cold water can be withdrawn from lake bottom, and warm water from the power plant can be returned to the top of lake. Due to the fact that stratification supresses vertical motion, water motion hence thermal mixing should be limited to a vertically thin layer not far away from the intake. In this section we treat the slow and steady flow of an isothermal but stratified fluid, due perhaps to salinity variation, into a twodimensional line sink. The molecular diffusivity of salt is ignored. These simplifications permits a analytical solution which is easy to examine the physical implicaions. For a slow flow of a viscous fluid flowing in a vertically stratified fluid. we expect, in light of Yih’s theorem, that the motion of the fluid should be confined within a thin layer.
A mechanical theory is described for a phenomenon in the surgical procedure of resuscitative endovascular balloon occlusion of the aorta (REBOA). In this procedure a balloon is pushed into the aorta by a catheter and then inflated in... more
A mechanical theory is described for a phenomenon in the surgical procedure of resuscitative endovascular balloon occlusion of the aorta (REBOA). In this procedure a balloon is pushed into the aorta by a catheter and then inflated in order to stop haemorrhage. One of the hazards of this procedure is the tendency for the balloon to migrate away from its intended position. This work examines the mechanics of balloon anchoring and migration by analysing the effects of pressure waves, the sheet flow and solid friction in the thin gap between the walls of the aorta and balloon. A viscoelastic model is adopted for the aorta wall for pressure waves between the left ventricle and the balloon. The lubrication approximation is used for blood flow in the thin gap between the walls of the balloon and aorta. Samples of quantitative predictions are discussed on how the inflation pressure and balloon characteristics affect the balloon anchoring and migration. The crucial roles of solid friction an...
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Salter has demonstrated experimentally that a horizontal cylinder in the free surface of water can be a device to extract energy from the incident waves. This paper proposes a design which is based on the idea of a tethered-float... more
Salter has demonstrated experimentally that a horizontal cylinder in the free surface of water can be a device to extract energy from the incident waves. This paper proposes a design which is based on the idea of a tethered-float breakwater, and gives the theoretical design criteria for maximum power extraction from a general floating cylinder with one or two degrees of freedom. It is shown that the rate of energy extraction must be equal to the rate of radiation damping and that the floating body must be made to resonate then for a body with one degree of freedom, the maximum efficiency at a given frequency can be at leastone half if the body is symmetrical about a vertical axis, and greater for an asymmetrical body. For a body with two degrees of freedom, all the wave power can be extracted. Hydrodynamical aspects of the controlled motion are examined. Viscous effects are ignored.
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By assuming a head loss across the harbor entrance the wave-induced response in a rectangular model harbor is studied theoretically. The loss is assumed to be quadratic in local velocity with a constant friction coefficient. Bottom and... more
By assuming a head loss across the harbor entrance the wave-induced response in a rectangular model harbor is studied theoretically. The loss is assumed to be quadratic in local velocity with a constant friction coefficient. Bottom and side-wall dissipation are not considered. It is ...
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The tidal waves scattered by a small island and a small cape of elliptical shape are derived by the method of matched asymptotics. The results complement the irrotational flow approximation of the near field by Proudman (Proc. Lond. Math.... more
The tidal waves scattered by a small island and a small cape of elliptical shape are derived by the method of matched asymptotics. The results complement the irrotational flow approximation of the near field by Proudman (Proc. Lond. Math. Soc., vol. 14, 1915, pp. 89–102). The potential for harnessing tidal power is assessed for the limiting case of a coast-connected thin dam.
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An approximate theory is developed for the two-dimensional propagation of tsunami emanated from a slender fault of fine length. Assuming significant contrasts between the sea depth, fault width, fault length and the bathymetric length... more
An approximate theory is developed for the two-dimensional propagation of tsunami emanated from a slender fault of fine length. Assuming significant contrasts between the sea depth, fault width, fault length and the bathymetric length scales, we invoke parabolic approximation to deduce a linear Kademtsev-Petviashivili (K-P) equation governing the two-dimensional propagation of dispersive long waves over great distances. Analytical techniques are employed to explore the far-field radiation in the forward and spanwise directions in a sea of constant depth. The solution can be used as a convenient input for predicting local variations of wave scattering and possibly breaking along a coast.
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This paper concerns in-plane vibration analysis of coupled bending and longitudinal vibrations in H- and T-shaped planar frame structures. An exact analytical solution is obtained using wave vibration approach. Timoshenko beam theory,... more
This paper concerns in-plane vibration analysis of coupled bending and longitudinal vibrations in H- and T-shaped planar frame structures. An exact analytical solution is obtained using wave vibration approach. Timoshenko beam theory, which takes into account the effects of both rotary inertia and shear distortion, is applied in modeling the flexural vibrations in the planar frame. Reflection and transmission matrices corresponding to incident waves arriving at the “T” joint from various directions are obtained. Bending and longitudinal waves generated by a combination of point longitudinal forces, point bending forces, and bending moments are also obtained. Assembling these wave relations provides a concise and systematic approach to both free and forced vibration analyses of coupled bending and longitudinal vibrations in H- and T-shaped planar frame structures. Natural frequencies, modeshapes, and forced responses are obtained from wave vibration standpoint. The results are compar...
Research Interests: Engineering, Mechanical Engineering, Civil Engineering, Modeling, Vibration, and 13 moreReflection, Structural Analysis, VIBRATION ANALYSIS, Acoustics and Vibration, Waves, Timoshenko Beam, Force, Interdisciplinary Engineering, Bending Moment, Inercia, Frequency Response, Inertia, and Wave reflection
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Approximate equations for the slow spreading of a thin sheet of Bingham plastic fluid. [Physics of Fluids A: Fluid Dynamics 2, 30 (1990)]. KF Liu, CC Mei. Abstract. A model that can approximately describe a non‐Newtonian fluid ...
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Abstract : The main part of the study is concerned with the analytical theory of harbor oscillations. The harbor system is composed of coast lines, basins and channels connected by narrow passages. The method of matched asymptotics is... more
Abstract : The main part of the study is concerned with the analytical theory of harbor oscillations. The harbor system is composed of coast lines, basins and channels connected by narrow passages. The method of matched asymptotics is used to avoid the usual solution of integral equations. Among several geometrical configurations, a harbor with two coupled basins is examined in detail for its physics. In a supplement a semi-empirical model theory is developed to study losses at the harbor entrance. (Author)
Research Interests: Physics, Estuaries, Water Waves, Ocean Waves, Flow Separation, and 2 moreOscillation and Excitation(Oscillation and Excitation)
(Oscillation and Excitation)
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Abstract : Theoretical results of scattering and radiation of simple-harmonic gravity waves by a vertical cylinder of elliptical cross-section are worked out in this report. The cylinder extends from the free surface to the bottom of the... more
Abstract : Theoretical results of scattering and radiation of simple-harmonic gravity waves by a vertical cylinder of elliptical cross-section are worked out in this report. The cylinder extends from the free surface to the bottom of the sea of constant depth. Linearized theory for small amplitude waves is adopted. The question of flow separation is not treated. The mathematical solution leads to Mathieu's equations and the computer program by Clemm is used. Physical quantities calculated include the wave forces and moments in various directions on, and the scattering amplitude around, a stationary cylinder due to a plane incident wavetrain. Also calculated are the damping coefficients representing radiation energy losses due to various modes of oscillation of a cylinder in the absence of incident waves. By the method of images the scattering of plane incident wave by a semi-elliptical peninsula is studied. Extensive numerical results are presented for various degrees of ellipticity, angles of incidence, and for wave-lengths ranging from very long to comparable to the horizontal dimensions of the cylinder. These results should provide useful information for the design of large ocean structures. (Author)
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