Browsing by Author "CHEN, JS"

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A GENERAL EXPRESSION FOR THE TOTAL RELEASE OF DIFFUSANT THROUGH HETEROGENEOUS MEMBRANES
(1992-02-19)
CHEN, JS
;
ROSENBERGER, F
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應用化學系
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Department of Applied Chemistry
An expression for the total amount of diffusant Q(t) released into a receiver by diffusion through a heterogeneous membrane is rigorously derived for time-dependent boundary conditions and a position-dependent initial condition. The heterogeneity of the membrane is characterized by a position-dependent diffusivity and partition coefficient. Two examples are given to demonstrate the utility of this general expression. It is shown that the expression for Q(t) proposed by Keister [ J. Membrane Sci., 29 (1986) 333-3441 is only valid when the asymptotic concentration of the diffusant within the membrane is zero.
CALCULATION OF LAG TIME FOR CONVECTIVE-REACTIVE DIFFUSION
(1991-11-28)
CHEN, JS
;
ROSENBERGER, F
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應用化學系
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Department of Applied Chemistry
Closed form solutions for the steady-state permeability P and the lag time L of a linear diffusion system with concurrent convection and reaction were obtained by two methods. In the first method, we identify the singularity at s = 0 of the Laplace transform of the total amount of diffusant, Q(s), released into the receiver as representation of the asymptotic diffusion behavior. P and L are then obtained from the time-independent coefficients of an expansion of Q(s) about s = 0. In the second method, we transform the convective-reactive diffusion equation into a form that contains only first and second derivatives of the concentration distribution function. By comparison of the resulting equation with that for a heterogeneous diffusion system, relationships of the convection velocity and rate constant with the position-dependent partition coefficient in heterogeneous diffusion is found. Taking advantage of the known solutions for permeabiliy and lag time in heterogeneous diffusion, the corresponding expressions for P and L in convective-reactive diffusion are then obtained by transcription. These methods have the advantage over earlier approaches in that solutions in an infinite form are avoided.
DIAPHRAGM DIFFUSION CELL - A CLOSED FORM SOLUTION TO THE TRANSPORT-EQUATION AND ITS APPLICATION TO THE DETERMINATION OF THE CONCENTRATION-DEPENDENCE OF THE HCL-H2O INTERDIFFUSION COEFFICIENT
(1992)
CHEN, JS
;
CLUNIE, JC
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BAIRD, JK
;
ROSENBERGER, F
;
應用化學系
In a thermodynamically non-ideal solution, the interdiffusion coefficient D(c) of a two-component system is a function of the concentration c. Since the mean concentration cBAR in a diaphragm cell remains constant during interdiffusion, we have found it useful to expand D(c) in a Taylor series about cBAR. After truncating the series and substituting the result into the diaphragm cell transport equation, we obtain a Bernoulli ordinary differential equation, which we solve in closed form. This solution is experimentally tested by determining D(c) from diaphragm cell data which we accumulated on aqueous hydrochloric acid at 25-degrees-C. Our results are in qualitative agreement with those of R. H. Stokes, who obtained D(c) from diaphragm cell data by using a graphical method [J. Am. Chem. Soc. 72, 2243 (1950)].
DIFFUSION LAG TIME FOR MULTIPLE AND PERIODIC LAMINATES
(1991)
CHEN, JS
;
ROSENBERGER, F
;
應用化學系
;
Department of Applied Chemistry
DIRECTIONAL SYMMETRY OF THE TIME-LAG FOR DOWNSTREAM ABSORPTIVE PERMEATION STUDIED BY THE MATRIX-METHOD
(1994-09-21)
CHEN, JS
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
;
Department of Applied Chemistry
The directional symmetry of the downstream time lag for absorptive permeation, accompanying a first-order reaction, across a heterogeneous membrane has been proven by the matrix method based on the theory of Siegel. Owing to the heterogeneity the partition coefficient (K), diffusivity (D) and rate constant (k) are all dependent on position. The directional symmetry was first shown for multiple laminates with each laminate having a distinct K, D and k. The transmission matrix of the system is then a sequential product of those of the individual laminates. The proof is for the unit value of the determinant of the transmission matrix for each laminate and, hence, for the whole system. Directional symmetry is thus proven for the heterogeneous membrane, since it can be visualized to be an assembly of an infinite number of infinitely thin, homogeneous laminates.
ELECTRICAL-PROPERTIES OF INSB METAL-INSULATOR SEMICONDUCTOR DIODES PREPARED BY PHOTOCHEMICAL VAPOR-DEPOSITION
(1987-08-03)
HUANG, KF
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SHIE, JS
;
LUO, JJ
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CHEN, JS
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交大名義發表
GRAPHIC METHOD FOR THE DETERMINATION OF THE COMPLEX NMR SHIFT AND EQUILIBRIUM-CONSTANT FOR A HETERO-ASSOCIATION ACCOMPANYING A SELF-ASSOCIATION
(1994-02-07)
CHEN, JS
;
SHIAO, JC
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交大名義發表
;
應用化學系
;
National Chiao Tung University
A novel graphic method to determine the complex shift and equilibrium constant for a hetero-association, A + B reversible arrow AB, accompanying a self-association A + A reversible arrow A(2), has been described. The method is to be used in conjunction with a graphic determination of the monomer shift, dimer shift and dimerization constant proposed previously. Our new method is advantageous over the conventional Benesi-Hildebrand (BH) plot in that the limitations, (1) that the concentration of one component must be much less than that of the other and (2) that self-association of species is not allowed, are completely removed. The related parameters of the self-association of 2-isopropylphenol (A) and the hetero-association of 2-isopropylphenol with acetone (B) in the inert solvent [H-2(12)]cyclohexane has been used to demonstrated the use of this new graphic method. Comparison with the results from a BH plot has also been made.
GRAPHICAL DETERMINATION OF MONOMER SHIFT, DIMER SHIFT AND DIMERIZATION CONSTANT FOR SELF-ASSOCIATION - 2-ISOPROPYL PHENOL IN C6D12 AS AN EXAMPLE
(1995-06-01)
CHEN, JS
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SHIAU, JC
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FANG, CY
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交大名義發表
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應用化學系
We propose a graphical method to treat dilution shift in NMR spectra to determine the monomer shift, dimer shift and dimerization constant simultaneously and consistently for the system of monomer/dimer equilibrium. The salient features include avoiding error-prone manual extrapolation to zero concentration to obtain a monomer shift, and providing consistent assessment and error estimation for the determination. The dilution shifts of 2-isopropyl phenol in C6D12 serve to demonstrate this graphical method. The enthalpy and entropy of dimerization are determined via a van't Hoff plot from the temperature variation of the dimerization constant.
NMR-STUDY OF EPSILON-CAPROLACTAM IN VARIOUS SOLVENTS - GRAPHICAL DETERMINATION OF MONOMER SHIFT, DIMER SHIFT AND DIMERIZATION CONSTANT FROM THE DILUTION SHIFT DATA
(1994-03-07)
CHEN, JS
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
;
Department of Applied Chemistry
A graphical method for the simultaneous determination of the monomer shift, dimer shift and dimerization constant of a self-association system from the dilution NMR shift data is proposed. This method avoids the conventional extrapolation to infinite dilution to obtain the monomer shift. Three self-association systems: epsilon-caprolactam in [H-2(1)]chloroform, [H-2(3)]acetone and [H-2(3)]acetonitrile were studied at various temperatures. The enthalpy and entropy of dimerization were also determined from van't Hoff plots.
NONLINEAR-ANALYSIS OF STABILITY FOR MOTORCYCLE-RIDER SYSTEMS
(1992)
LIU, TS
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CHEN, JS
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交大名義發表
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機械工程學系
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National Chiao Tung University
In this study, linear and nonlinear analyses of motorcycle-rider motion are carried out to investigate the stability of the motorcycle-rider integrated system. Equations of motion are derived using Lagrange's equation. Transfer functions that account for the rider's perception and action are taken into account. In the linear analysis, its dynamic behaviour is characterized by eigenvalues and eigenvectors. The effects of design parameter changes on capsize. weave and wobble modes are examined, and the design implication is discussed. The nonlinear analysis for system stability is conducted by means of the centre manifold theory and bifurcation theory. Stability boundaries in a parameter space and the corresponding bifurcation diagrams are obtained for in-depth understanding of the system stability. Moreover, comparison of results with and without rider's control shows the significant effect of the rider on the stability performance of the entire system.
PASSIVATION OF GAAS POWER FIELD-EFFECT TRANSISTOR USING ELECTRON-CYCLOTRON-RESONANCE CHEMICAL-VAPOR-DEPOSITION SILICON-NITRIDE TECHNIQUE
(1994-12-01)
CHANG, EY
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LIN, KC
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WU, JW
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CHEN, TH
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CHEN, JS
Monolithic microwave integrated circuit (MMIC) chips are typically passivated with dielectric films to improve their long-term environmental reliability. Improper passivation generally degrades chip performance and reduces wafer yield. This paper reports the change of metal-semiconductor field-effect transistor (MESFET) parameters after silicon nitride passivation using electron cyclotron resonance chemical vapor deposition (ECR-CVD). In general, the changes in the electrical parameters after passivation are small. Gate-drain breakdown voltage of the MESFET's after ECR-CVD passivation is significantly improved compared to that after PECVD. The microwave characteristics of the high-powered MESFET's passivated using ECR-CVD silicon nitride are also reported in this paper.
PERMEABILITY AND THE TIME-LAG FOR DOWNSTREAM ABSORPTIVE PERMEATION WITH CONCOMITANT REACTION ACROSS A SERIES-PARALLEL PATH STUDIED BY THE MATRIX-METHOD
(1995-02-07)
SHI, WG
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CHEN, JS
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應用化學系
;
Department of Applied Chemistry
Based on Siegel's theory, the permeability (P) and the downstream time lag (t(L)) for absorptive unidirectional permeation, accompanying a first-order reaction, across a membrane composed of two parallel laminae in series with another lamina, have been calculated from the transmission matrix of the whole membrane. This matrix can be constructed from the transmission matrix of each component lamina. The transmission matrix of the whole membrane is first calculated from the matrices of the component laminae in the Laplace domain. P and t(L) are then derived from the first row and second column of the transmission matrix of the whole membrane according to Siegel's theory. Thus, P and t(L) can be represented in terms of the elements of the transmission matrix, and hence the diffusion parameters, of each component lamina. The directional symmetry of t(L) is also proven, based on the unity value of the determinant of the transmission matrix. The advantage of the matrix method is also discussed.
RECIPROCITY OF LAG TIME FOR REACTIVE DIFFUSION THROUGH HETEROGENEOUS MEMBRANES - A GREEN-FUNCTION APPROACH
(1991)
CHEN, JS
;
ROSENBERGER, F
;
應用化學系
;
Department of Applied Chemistry
THE RELIABILITY OF MULTILEVEL METALLIZATION ON INGAAS/GAAS LAYERS
(1994)
CHANG, EY
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CHEN, JS
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WU, JW
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LIN, KC
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材料科學與工程學系
THE THERMAL-STABILITY OF OHMIC CONTACT TO N-TYPE INGAAS LAYER
(1995-02-01)
WU, JW
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CHANG, CY
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LIN, KC
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CHANG, EY
;
CHEN, JS
The thermal stability of ohmic contact to n-type InGaAs layer is investigated. When Ni/Ge/Au is used as the contact metal, the characteristics of the ohmic contact are degraded after thermal treatment. The specific contact resistance of (Ni/Ge/Au)-InGaAs ohmic contact after annealing at 450 degrees C is about 15 times larger than that of as-deposited sample. This is due to the decomposition of InGaAs and the interdiffusion of Ga and Au.-A new phase of Au4In appears after annealing at 300 degrees C. While in the case of Ti/Pt/Au, Au does not penetrate into the InGaAs layer as revealed by secondary ion mass spectroscopy. The specific contact resistance of(Ti/Pt/Au)-InGaAs ohmic contact after annealing at 450 degrees C is eight times larger than that of as-deposited sample. Therefore, the thermal stability of(Ti/Pt/Au)-InGaAs ohmic contact is better than that of(Ni/Ge/Au)-InGaAs ohmic contact.
THEORY OF THE TIME-LAG DIFFUSION METHOD FOR THE CASE OF AN OUTGASSING SOLID
(1993-06-01)
BAIRD, JK
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CHEN, JS
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應用化學系
;
Department of Applied Chemistry
In the ordinary application of the time-lag method to the measurement of the diffusion coefficient of a gas passing through a plane sheet of an inert solid, the gas is pressurized on one side of the sheet and evacuated on the other. After decay of transients, the cumulative amount, Q(t), of gas diffused through the sheet in time, t, assumes the ''time-lag'' form, Q(t) = A(t - L). Measurements of the slope, A, and the intercept, L, can be used to determine the diffusion coefficient and the solubility of the gas in the solid. We have rederived this law for the case of a solid that is actively evolving this same gas at an arbitrary rate and have used it to predict the rate of outgassing of the solid upon standing. Practical applications of the theory include radioactive decay of minerals, rejection of plasticizers by plastics, and the decomposition of solid rocket propellants.