Showing papers by "National Tsing Hua University published in 1987"

Estimating the population size for capture-recapture data with unequal catchability.

Abstract: A point estimator and its associated confidence interval for the size of a closed population are proposed under models that incorporate heterogeneity of capture probability. Real data sets provided in Edwards and Eberhardt (1967, Journal of Wildlife Management 31, 87-96) and Carothers (1973, Journal of Animal Ecology 42, 125-146) are used to illustrate this method and to compare it with other estimates. The performance of the proposed procedure is also investigated by means of Monte Carlo experiments. The method is especially useful when most of the captured individuals are caught once or twice in the sample, for which case the jackknife estimator usually does not work well. Numerical results also show that the proposed confidence interval performs satisfactorily in maintaining the nominal levels.

Comparison of hydrogen gas embrittlement of austenitic and ferritic stainless steels

Abstract: Hydrogen-induced slow crack growth (SCG) was compared in austenitic and ferritic stainless steels at 0 to 125 °Cand 11 to 216 kPa of hydrogen gas. No SCG was observed for AISI 310, while AISI 301 was more susceptible to hydrogen embrittlement and had higher cracking velocity than AL 29-4-2 under the same test conditions. The kinetics of crack propagation was modeled in terms of the hydrogen transport in these alloys. This is a function of temperature, microstructure, and stress state in the embrittlement region. The relatively high cracking velocity of AISI 301 was shown to be controlled by the fast transport of hydrogen through the stress-induced α′ martensite at the crack tip and low escape rate of hydrogen through the γ phase in the surrounding region. Faster accumulation rates of hydrogen in the embrittlement region were expected for AISI 301, which led to higher cracking velocities. The mechanism of hydrogen-induced SCG was discussed based upon the concept of hydrogen-enhanced plasticity.

Kinetics and mechanism of urethane reactions: Phenyl isocyanate–alcohol systems

Abstract: Urethane reactions of phenyl isocyanate alcohol systems with toluene as solvent and various aprotic polar solvents (including tertiary amines) as additives were carried out at constant temperature of 10–40°C. Analysis of the variation of the second order rate constants of these systems and those available in the literature indicates that formation of the hydrogen bonding complexes (alcohol with phenyl isocyanate and with aprotic solvent) and electron donor number (DN) of the aprotic solvent are the two factors allowing satisfactory explanation of the catalysis and inhibition effects of the wide range of aprotic solvents (including amines, amides, etc.). Based on these considerations, an ion-pair mechanism and the resulting kinetic equation for the urethane reaction are proposed. Verification on the kinetic equation with experimental results for the systems of phenyl isocyanate with alcohol in toluene (for the self catalysis of the alcohol), with dimethyl formamide and dimethyl sulfoxide in toluene (for the catalysis of the aprotic solvents), and with triethylamine in toluene (for the catalysis of the tertiary amines) shows satisfactory. In the mechanism, the aprotic solvent is considered to solvate the complex of phenyl isocyanate/alcohol at the active hydrogen to form an ion-pair which can undergo the urethane reaction more easily.

Magnetic fluctuations and two-dimensional ordering in ErBa2Cu3O7

Abstract: Neutron-diffraction and small-angle scattering techniques have been used to study the magnetic properties of ErBa/sub 2/Cu/sub 3/O/sub 7/. Below the superconducting transition of 95 K there is a decrease in the small-angle scattering, which has the correct amplitude, temperature dependence, and q dependence to be interpreted as the screening of the paramagnetic fluctuations by the superconducting electrons. At low temperatures (--1/2 K) the Er moments become ordered two dimensionally, with chains of spins coupled ferromagnetically, while adjacent chains align antiparallel.

Vorticity-Velocity Method for the Graetz Problem and the Effect of Natural Convection in a Horizontal Rectangular Channel With Uniform Wall Heat Flux

Abstract: Numerical solutions given by a vorticity-velocity method are presented for combined free and forced laminar convection in the thermal entrance region of a horizontal rectangular channel without the assumptions of large Prandtl number and small Grashof number. The channel wall is heated with a uniform wall heat flux. Typical developments of temperature profile, secondary flow, and axial velocity at various axial positions in the entrance region are presented. Local friction factor and Nusselt number variations are shown for Rayleigh numbers Ra = 10{sup 4}, 3 {times} 10{sup 4}, 6 {times} 10{sup 4}, and 10{sup 5} with the Prandtl number as a parameter. The solution for the limiting case of large Prandtl number and small Grashof number obtained from the present study confirms the data of existing literature. It is observed that the large Prandtl number assumption is valid for Pr = 10 when Ra {le} 3 {times} 10{sup 4} but for a larger Prandtl number when the Rayleigh number is higher.

Kinetics of polyesterification III: Solid-state polymerization of polyethylene terephthalate

Abstract: Experimental studies on the solid-state polymerization (SSP) of polyethylene terephthalate (PET) for the particle sizes of 14–16 mesh at 170–200°C and for the particle sizes of 14–18 mesh at 210–240°C are carried out under a vacuum of about 60 mtorr. Analysis of the data of the concentrations of hydroxyl and carboxyl groups and the number average molecular weight during the SSP allows determinations of the rates of esterification and ester interchange separately. It is found that at the temperature 170–200°C and the particle size 80–100 mesh the SSP is end-group diffusion limiting, and that at the temperature 210–240°C and the particle size 14–16 mesh the ester interchange is ethylene glycol diffusion limiting and the esterification is predominantely end-group diffusion limiting due to higher diffusion rate of water. These phenomena are explored by an assistance of the proposed rate expressions for the end-group diffusion limited reactions and diffusion models for the by-products, water, and ethylene glycol.

Substrate protection of immobilized glucose isomerase.

Abstract: Using commercial immobilized glucose isomerase (SWETASE(R), Nagase Co.), the effect of substrate protection on enzyme deactivation has been studied in a batch manner. The data analysis was carried out based on Briggs-Haldane kinetics in which enzyme deactivation accompanying the protection of substrates was also considered. The protection factor was proposed to elucidate the dependence of the degree of substrate protection. The existence of the protection of glucose isomerase by the substrates has been verified experimentally. Also, the enzyme-substrate complex deactivates with a decay constant which is one-half that of the free enzyme. Theoretical analysis of enzyme deactivation with substrate protection offers an effective understanding which is essential for enzyme replacement and process optimization.

Mixed Convection Along Vertical Cylinders and Needles with Uniform Surface Heat Flux

Abstract: Mixed convection along vertical cylinders and needles with uniform surface heat flux is investigated for the entire mixed convection regime. A single modified buoyancy parameter {chi} and a single curvature parameter {Lambda} are employed in the analysis such that a smooth transition from pure forced convection ({chi} = 1) to pure free convection ({chi} = 0) can be accomplished. For large values of the curvature parameter and/or Prandtl number, the governing transformed equations become stiff. Thus, a numerically stable finite-difference method is employed in the numerical solution in conjunction with the cubic spline interpolation scheme to overcome the difficulties that arise from the stiffness of the equations. Local Nusselt numbers are presented for 0.1 {le} Pr {le} 100 that cover 0 {le} {chi} {le} 1 ({infinity} {ge} {Omega}{sub x} {ge} 0) and 0 {le} {Lambda} {le} 50. For needles ({Lambda} {ge} 5), the local Nusselt numbers (Nu{sub x}/Re{sub x}{sup 1/2} + Gr{sub x}{sup 1/5}*) are found to be nearly independent of the buoyancy parameter {chi}. Correlation equations for the local Nusselt numbers are also presented.

Model reduction by power decomposition and frequency response matching

Abstract: A mixed method of linear system model reduction, retaining the advantages of the power decomposition method and the frequency response matching method, is proposed From the viewpoint of energy contributions to the system output, the dynamic modes with dominant energy contributions instead of those with dominant eigenvalues will be preserved Having determined the denominator of the reduced model, the parameters of the numerator are found by using the frequency response matching technique

Electrolytic oxidation of cuprocyanide electroplating waste waters under different pH conditions

Abstract: The main purpose of this work was to investigate the electrolytic oxidation of cuprocyanide solution with various total cyanide to copper molar ratios ranging from 2.8 to 20 and under different pH conditions. In strong alkaline solution (pH≥12), cuprocyanide ions Cu(CN) /(−1)− , wheren=2, 3 or 4, are directly electroxidized, and copper oxide precipitates on the anode. Cyanate ions, as well as nitrogen gas, were detected as the products and 0.30–0.43 g mol of total cyanide was destroyed per Faraday. For less alkaline solutions (pH<12), cuprocyanide ions first dissociated to free cyanide ions and then electroxidized. At a pH of 10.5–11.7, cyanate ion and brown azulmin polymer were produced in the anolyte. In the neutral solution (pH=7.0–8.6), carbonate and ammonium ions and azulmin were formed and 0.52–0.56 g mol of total cyanide was destroyed per Faraday. In weak acidic solution (pH=5.2–6.8), oxalate and ammonium ions and white oxamide were produced and 1.01–1.18 g mol of total cyanide were destroyed per Faraday.

Cross‐sectional transmission electron microscope study of the growth kinetics of hexagonal MoSi2 on (001)Si

Abstract: Cross‐sectional transmission electron microscopy (XTEM) has been applied to the study of the growth kinetics of hexagonal MoSi2 on (001)Si. Growth rates, interface structures, and microstructures in the growth layers were determined for samples annealed at 560–580 °C for various periods of time. The silicide thickness was found to be proportional to the square root of annealing time. The activation energy and the rate constant of the growth were measured to be 2.3 eV and 14 cm2/s, respectively. Growth mechanisms are discussed. The results of the previous studies on the MoSi2 growth are summarized. Advantages of the present approach in the study of the growth kinetics of silicides on silicon, both in sample preparation and in the employment of XTEM technique, are outlined.

Improvement of the Current Efficiency of an Al‐Zn‐In Anode by Heat‐Treatment

Abstract: Aluminum anodes, each having one of several heat-treatments (namely as-cast (A), furnace-cooled (B), quenched (C), and quenched and aged (D-1)) were electrically coupled to structural steels to provide cathodic protection. The electro-chemical potential of each galvanic couple depended on the type of heat-treatment: anodes A, B, and C exhibited a potential of -1.10V, and anode D-1 was somewhat less negative at -0.95V. Empirical relationships between galvanic current density and area ratio (AR), based on 120h tests, have been established. Surface examination showed that anodes A, B, and C corrode uniformly, whereas anode D-1 dissolves locally. Results showed that the current efficiency of a sacrificial aluminum anode is dependent on its microstructure, which is, in turn, affected by its heat-treatment. Both anodes A and B possessed an equilibrium precipitate of In and the corresponding efficiencies did not vary with time. However, anode C, and especially anode D-1, suffered from aging, and their efficiencies varied with time. The microstructure of anode C contained thermal defects such as dislocation loops, while anode D-1 contained both dislocation loops and microsegregates. Results confirm that as-cast and furnace-cooled anodes have the best efficiencies (94-98%), while quenched and aged anodes have significantly lower efficiencies (69%).

Thermal and rheological properties of poly(phenylene sulfide) and poly(ether etherketone) resins and composites

Abstract: Poly(phenylene sulfide) (PPS) and poly(ether etherketone) (PEEK) are high performance engineering thermoplastics with a unique combination of excellent environmental, mechanical, and thermal properties. Research on the thermal and rheological properties of PPS and PEEk resins and carbon fiber reinforced prepregs are described. Experimental studies of the dynamic viscoelasticity and thermal properties of these materials are summarized. The effects of processing cycles and environment on the thermal and rheological properties are discussed. The effects of the processing environment and the addition of carbon fiber on the thermal stability are reported. Crosslinking of poly(phenylne sulfide) in air, enhancing thermal stability, is also investigated. 16 references.

Localized epitaxial growth of IrSi3 on (111) and (001) silicon

Abstract: Transmission electron microscopy has been applied to the study of interfacial reactions of iridium thin films on silicon with particular emphasis on the epitaxial growth of IrSi3 on (111) and (001)Si. The formation of precursor phases, IrSi and IrSi1.75, were found to occur mainly in the temperature ranges of 300–500 and 600–900 °C, respectively. The stable IrSi3 was found to grow epitaxially on (111) and (001)Si annealed at 1000–1100 °C. There are three dominant modes of epitaxial IrSi3 on (111)Si and one dominant mode of epitaxial IrSi3 on (001)Si. Interface structures of these different epitaxial modes were determined by diffraction contrast analysis. The quality of IrSi3 epitaxy in terms of the fraction of the silicon surface coverage, size, and the regularity of the interfacial dislocations was found to be the best in (111) samples annealed at 1000 °C. Epitaxial regions of IrSi3, as large as 40 μm in size, were observed on (111)Si. No direct correlation between lattice match and quality of epitaxy co...

Solvent Sublation and Adsorbing Colloid Flotation of Magenta

Abstract: Magneta was removed from aqueous solution into paraffin oil by solvent sublation of a magenta-lauryl sulfate complex. Over 96% of magenta was removed in 25 min. A stoichiometric amount of surfactant was found to be most effective for magenta removal (1 mol of surfactant to 1 mol of dye). First-order kinetics was not followed. It is proposed that some kinds of aggregate of the dye-surfactant complex may exist in the solution. Magenta was also removed by adsorbing colloid flotation techniques using either ferric hydroxide or aluminum hydroxide as the coagulant. Sodium lauryl sulfate was used as the collector. Over 99.6% of magenta was removed from the solution in as little as 3 min. However, the amount of surfactant needed appears to be high.

Chemical and chemotaxonomical studies of ferns. LXXIII. New flavonoids with modified B-ring from the genus Pseudophegopteris(Thelypteridaceae).

Abstract: Chemical studies of three representatives of the genus Pseudophegopteris (Thelypteridaceae) revealed that the genus is characterized by the occurrence of unusual flavonoids with a modified B-ring related to protogenkwanin (VII). From P. hirtirachis HOLTT., three novel compounds, protogenkwanone (I), tetrahydroprotogenkwanone (II) and tetrahydroprotogenkwanin (III), were isolated, along with protogenkwanin 4'-O-β-D-glucoside (VI). From P. subaurita CHING, two new acylated glucosides of protogenkwanin, protogenkwanin 4'-O- (2-O-acetyl) -β-D-glucoside (IV) and 4'-O- (6-O-acetyl) -β-D-glucoside (V), were obtained, together with I, II and VI. From P. bukoensis HOLTT., IV, V and VI were isolated, in addition to apigenin 7-O-α-L-rhamnoside and kaempferol. The structures of the new compounds were determined by means of spectroscopic methods and chemical transformations.

Systolic algorithms for the longest common subsequence problem

Abstract: The concept of systolic array processors is very suitable for VLSI implementation. In this paper, we propose two systolic algorithms to solve the longest common subsequence problem by dynamic programming approach and also prove that these two algorithms are correct. The order of the time‐processor‐product of our algorithms is equal to that of the corresponding sequential method.

The influence of firing profile and additives on the PTCR effect and microstructure of BaTiO3 ceramics

Abstract: Nonstoichiometric BaTiO3 PTCR type materials are investigated with various amounts of MnO2, Sb2O3 and MgO dopants. Specimens fired with a nonisothermal rate-controlled sintering profile exhibit a rather fine and uniform microstructure as compared to those processed by conventional sintering techniques. The temperature at which the resistivity anomaly begins is observed to decrease with Sb2O3 and MgO contents. The Curie point of BaTiO3-based ceramics can be altered by addition of Sb2O3, and the dielectric peak is maintained by the presence of MgO additive. Magnesium ions act as acceptors in the BaTiO2 lattice, while antimony ions as donors. The presence of magnesium compensates some of the antimony, hence the doped-BaTiO3 seminonductive region is pushed to higher contents.

Endogenous Basic Protein Phosphatases in the Brain Myelin

Abstract: Direct treatment of brain myelin with freezing/thawing in 0.2 M2-mercaptoethanol stimulated the endogenous myelin phosphatase activity manyfold when 32P-la-beled phosphorylase a was used as a substrate, a result indicating that an endogenous myelin phosphatase is a latent protein phosphatase. When myelin was treated with Triton X-100, this endogenous latent phosphatase activity was further stimulated 2.5-fold. Diethylaminoethyl-cellulose and Sephadex G-200 chromatography of solubilized myelin revealed a pronounced peak of protein phosphatase activity stimulated by freezing/thawing in 0.2 M2-mercaptoethanol and with a molecular weight of 350, 000, which is characteristic of latent phosphatase 2, as previously reported. Moreover, endogenous phosphorylation of myelin basic protein (MBP) in brain myelin was completely reversed by a homogeneous preparation of exogenous latent phosphatase 2. By contrast, under the same conditions, endogenous phosphorylation of brain myelin was entirely unaffected by ATP. Mg-dependent phosphatase and latent phosphatase 1, although both enzymes are potent MBP phosphatases. Together, these findings clearly indicate that a high-molecular-weight latent phosphatase, termed latent phosphatase 2, is the most predominant phosphatase responsible for dephosphorylation of brain myelin.

Systolic algorithms to examine all pairs of elements

Abstract: Four methods to solve the all pairs examination problem are presented. The first two methods are based on the fold-over scheme. The remaining two methods are adopted from some parallel sorting algorithms. All of these approaches can be implemented on a linear systolic array.