Showing papers by "National Cheng Kung University published in 1993"

An expert system for transformer fault diagnosis using dissolved gas analysis

Abstract: A prototype expert system based on the dissolved gas analysis (DGA) technique for diagnosis of suspected transformer faults and their maintenance actions is developed. A synthetic method is proposed to assist the gas ratio method. The uncertainties of key gas analysis, norms threshold, and gas ratio boundaries, are managed by using a fuzzy set concept. The expert system is implemented on a PC-AT using KES with rule-based knowledge representation. The system has been tested to show its effectiveness in transformer diagnosis. >

A controller design framework for telerobotic systems

Abstract: A framework for designing a telerobotic system controller is presented. This controller is designed so the dynamic behaviors of the master robot and the slave robot are functions of each other. These functions, which the designer chooses based upon the application, are described, and a control architecture is proposed to achieve these functions. To guarantee that the specified functions and proposed architecture govern the system behavior, H/sub infinity / control theory and model reduction techniques are used. Several experiments were conducted to verify the theoretical derivations. This control method is unique, because it does not require any transfer of either position or velocity information between the master robot and the slave robot; it only requires the transfer of forces. Although this property leads to a wider communication bandwidth between the master and slave robots, the entire system may still suffer from a positional error buildup between the master robot and slave robot. >

Dynamic search-window adjustment and interlaced search for block-matching algorithm

Abstract: A technique called dynamic search-window adjustment is proposed to improve the performance of three-step searches (TSS) and to prevent the search direction from being easily misdirected by insufficient information. An interlaced-search technique is presented for the purpose of reducing the search positions. A fast search algorithm using both techniques is proposed. It is shown that the average displaced frame difference and search positions of the proposed algorithm are about 1-7% and 24-44% fewer than TSS, respectively. >

The shear strength and the failure mode of plasma‐sprayed hydroxyapatite coating to bone: The effect of coating thickness

Abstract: Plasma-sprayed hydroxyapatite coated (HAC) 50 and 200 microns thick on Ti-6Al-4V cylinders was transcortically implanted in the femora of canines to evaluate in detail the effect of coating thickness on the pushout shear strength and failure mode examined under scanning electron microscope after the periods of 4, 6, 8, and 12 weeks. The HAC coating exhibited higher shear strength at 50 microns than at 200 microns. Its failure mode was conclusively at or near the HAC-bone interface, and the slight attack of body fluid had not degraded the implant to the extent that failure occurred at the HAC-Ti alloy interface after 12 weeks of observation. For 200 microns-HAC, failure was found at the HAC-bond interface, inside the HAC lamellar splat layer and at the HAC-Ti alloy substrate interface, depending on the period of implantation. It was also deduced that the variation of failure mode of 200 microns-HAC with time could not be accounted for by the attack of body fluid alone; the degradation must be a synergetic adverse result of residual stress in the HAC and the attack of body fluid.

Molecular basis of genetic variation in debrisoquin hydroxylation in Chinese subjects: polymorphism in RFLP and DNA sequence of CYP2D6.

Abstract: Debrisoquin hydroxylation phenotype was determined in 124 Chinese persons living in Taiwan, and two poor metabolizers were identified with a urinary metabolic ratio (MR) greater than 12.6. The other subjects, extensive metabolizers, showed a normal frequency distribution of log(MR). Most subjects (50%) showed a 44/29 kb pattern in restriction fragment length polymorphism (RFLP) analysis with use of Xba I, and 30% and 15% of the subjects exhibited a homozygous 29/29 kb and 44/44 kb pattern, respectively. Among extensive metabolizers, subjects with the 44/44 kb pattern had a significant higher log(MR) than those with the 44/29 pattern, and the log(MR) of the subjects with the 44/29 kb pattern was significantly higher than that of the subjects with 29/29 kb pattern. All nine exons and intron 3 of CYP2D6 were amplified with polymerase chain reaction (PCR) and sequenced for four extensive metabolizers. Two major polymorphisms were found: one at position 188 of exon 1 and the other at position 4268 in exon 9. With PCR and endonuclease digestion, polymorphisms at exon 1, intron 3, and exon 9 were investigated. Only two of 254 alleles showed a heterozygous guanine at 1934 base pairs (G1934) to adenine (A) mutation, commonly found in white poor metabolizers. Approximately 70% of alleles showed thymine at 188 base pairs (T188), and 76% showed cytosine at 4268 base pairs (C4268) instead of C188 and G4268, as is found in most white subjects. Subjects with T188 or C4268 showed a significant higher log(MR) than subjects with homozygous C188 and G4268. The C/T188, G/A1934, G/C4268, and RFLP polymorphisms may explain the interracial variations between Chinese and white subjects, as well as the genetic variations among Chinese subjects. Clinical Pharmacology and Therapeutics (1993) 53, 410–418; doi:10.1038/clpt.1993.44

Elastic moduli of a composite of hollow spheres in a matrix

Abstract: L ow density foams deform primarily by bending of the cell edges. Their mechanical properties could be improved by increasing the flexural rigidity of the wall. The introduction of a high volume fraction of thin walled hollow spheres into a foamed matrix produces a composite cellular solid with a sandwich cell wall: the walls of the spheres act as the faces of the sandwich while the foamed matrix acts as the core. As a first step to producing cellular solids with sandwich cell walls, in this paper we describe the elastic moduli of a composite cellular solid made by introducing thin walled hollow spheres into a solid matrix.

Melatonin Decreases Brain Serotonin Release, Arterial Pressure and Heart Rate in Rats

Abstract: The effects of intravenous administration of melatonin (30–60 mg/kg) or vehicle (10% alcohol) on arterial pressure, heart rate, blood gases or brain serotonin release were assessed in rats under ureth

Effects of Pore Morphology and Grain Size on the Dielectric Properties and Tetragonal–Cubic Phase Transition of High‐Purity Barium Titanate

Abstract: The effects of pore morphology and grain size on the dielectric behavior of high-purity stoichiometric BaTiO3 have been intensively investigated. It was found that the dielectric constant was influenced not only by grain size but also by pore morphology. Dielectric constants below the Curie temperature could be evaluated by the Maxwell relationship for specimens with fractional density >90%ρt and be estimated by the modified Niesel's equation, but depolarization might be involved for specimens with fractional density 6100 at 25°C and 1 kHz) and a low dissipation factor (<0.025) could be achieved.

Liquid-phase oxidation of cyclohexane using CoAPO-5 as the catalyst

Abstract: In this study, CoAPO-5 was found to be an effective heterogeneous catalyst for the liquid-phase oxi- dation of cyclohexane with glacial acetic acid as the solvent without any promotors being added to the reaction mixture. The effects of cobalt content, BET surface area and dissolved cobalt ions and the kinetics of the reaction were investigated at 5–15 kg/cm2 and 115–135°C in a semi-batch autoclave reactor. Under these reaction conditions, no induction period was observed. The products of reaction were cyclohexanone, cyclohexanol, dibasic acids, and caprolactone, etc. The ratio of the concentration of adipic acid to succinic acid had a maximum value at the middle stage of reaction. The initial rate of reaction was found to be proportional to the 2.0 power of the cyclohexane concentration and to the 0.5 power of the catalyst loading. The effects of oxygen pressure on the reaction rate depended on the cobalt content and the reaction conditions. The cobalt ions of CoAPO-5 are mainly in the lattice positions and they can transform reversibly between the oxidizing states of CoII and CoIII. Reaction mechanism and rate expressions were proposed. Since the conversion and selectivity reported in this study were mod- erately good, and because CoAPO-5 has the advantage of being a durable heterogeneous catalyst, it could prove useful as a catalyst for the one-step liquid-phase oxidation of cyclohexane.

Investigation of magnetizing inrush current in transformers. I. Numerical simulation

Abstract: A simple method for simulating magnetizing inrush currents in power transformers using real-time measurements is proposed. The method is based on a simplified model for representing the inrush current under different loading conditions. A digital simulation method using a PC-AT microcomputer is also proposed. Transformer operating conditions, including transformer loading power factors, switching-on angles, and remanent flux, are included. The simulation result show very good agreement with experiment results. >

On the anisotropic elastic inclusions in plane elastostatics

Abstract: By combining the method of Stroh`s formalism, the concept of perturbation, the technique of conformal mapping and the method of analytical continuation, a general analytical solution for the elliptical anisotropic elastic inclusions embedded in an infinite anisotropic matrix subjected to an arbitrary loading has been obtained in this paper. The inclusion as well as the matrix are of general anisotropic elastic materials which do not imply any material symmetry. The special cases when the inclusion is rigid or a hole are also studied. The arbitrary loadings include in-plane and antiplane loadings. The shapes of ellipses cover the lines or circles when the minor axis is taken to be zero or equal to the major axis. The solutions of the stresses and deformations in the entire domain are expressed in complex matrix notation. Simplified results are provided for the interfacial stresses along the inclusion boundary. Some interesting examples are solved explicitly, such as point forces or dislocations in the matrix and uniform loadings at infinity. Since the general solutions have not been found in the literature, comparison is made with some special cases of which the analytical solutions exists, which shows that our results are exact and universal.

Physical conditioning can modulate endothelium-dependent vasorelaxation in rabbits.

Abstract: To investigate whether exercise training can modulate endothelium-dependent vasorelaxation, male New Zealand White rabbits were divided into either control or training groups. The training animals were trained on a treadmill with a running speed of 0.88 km/hr on a 0 degree grade for 10-60 minutes/day, 5 days/week for 8 weeks. After exercise training, the resting heart rate was lowered (p < 0.05). At the end of the experiments, three vessel segments, i.e., the thoracic aortas, the pulmonary arteries, and the common carotid arteries, were isolated and precontracted with norepinephrine. Acetylcholine-stimulated endothelium-derived relaxing factor (EDRF) release was assessed by bioassay in the presence of indomethacin (10(-5) M). Basal release of EDRF was examined by the addition of hemoglobin. In addition, the relaxing responses of the thoracic aortas and pulmonary arteries to A23187, a calcium ionophore, and to sodium nitroprusside, a direct vasodilator of vascular smooth muscle, were compared between control and trained groups to further investigate possible underlying mechanisms. The results indicated that after exercise training 1) both the thoracic aorta and pulmonary artery, but not the carotid artery, became more sensitive to acetylcholine-induced vasorelaxation; 2) no significant differences in basal release of EDRF between control and trained rabbits were observed; and 3) there were no significant differences in the vascular responses to A23187 or sodium nitroprusside between the two groups. Our data suggest that exercise training may enhance endothelium-dependent vasodilation to acetylcholine via the stimulated EDRF release and that this elevated sensitivity to acetylcholine may not be caused by the alteration of the relaxing response in vascular smooth muscle.

Dynamic Responses of Composite Sandwich Plate Impacted by a Rigid Ball

Abstract: A refined formulation of composite sandwich plate is employed to study the dynamic response of impacted sandwich plate. In this refined formulation, the faces of the sandwich plate are modeled as t...

Piezoelectric properties of multiphase fibrous composites: Some theoretical results

Abstract: A number of exact results are established for overall moduli of a piezoelectric composite medium consisting of many perfectly-bonded transversely isotropic phases of cylindrical shape and arbitrary transverse geometry. It is shown that for three-phase media of this type three universal relationships, which are independent of geometry at given volume fractions, connect six of these effective physical constants. When the phases have equal transverse rigidities in shear, exact values of certain overall moduli can be derived for multiphase systems. The explicit formulae depend solely on the concentrations and phase moduli and are unaffected by the transverse geometry of the inclusions. Specifically, seven out of a total of 10 overall moduli of a transversely isotropic composite can be found. The remaining three constants p, e15 and k11 are shown to obey an exact relation, which also applies to other physical phenomena, such as magnetoelectric and thermoelectric effects. The result is a generalization of the relations found by H ill [J. Mech. Phys. Solids12, 199 (1964)] for purely elastic media and by Mendelson[J. Appl. Phys.46, 917 (1975)] for the purely dielectric problem.

Detection of hepatitis C virus RNA in peripheral blood mononuclear cells and in saliva

Abstract: The nested polymerase chain reaction (PCR) technique was applied to investigate hepatitis C virus (HCV) RNA in the peripheral blood mononuclear cells (PBMCs), saliva, and serum of patients with chronic type C hepatitis. The specificity of the amplified products was analyzed and confirmed by agarose gel electrophoresis, Southern blot hybridization, and restriction endonuclease pattern analysis. HCV RNA was detectable in the PBMCs of 24% (12/50) of the patients. The HCV RNA detected in PBMCs was not due to the contamination from plasma, since no viral sequences could be detected in the third washing of PBMCs. Of the 12 patients with HCV RNA in PBMCs, five were negative for HCV RNA sequences in the serum. Thus the presence of HCV RNA in PBMCs was not strictly correlated to the results for sera. Among 25 patients with HCV RNA in their saliva, 18 were negative for PBMCs. Among 25 patients without HCV RNA in their saliva, five had HCV RNA in PBMCs. In conclusion, PBMCs are an extrahepatic target for chronic HCV infection. However, we do not suggest that PBMCs act as a vehicle for carrying HCV to saliva, since the presence of HCV RNA in PBMCs and in saliva was not closely correlated.

Optimization of noncollocated sensor/actuator location and feedback gain in control systems

Abstract: An analytical model is developed for structural control optimization in which both noncollocated sensor/actuator placement and feedback control gain are considered as independent design variables. Two different control algorithms-active damping control and optimal output feedback control-are applied to derive the control input, and the optimal set of solutions is determined by the modified method of feasible direction. Analytical results show that noncollocated sensor/actuator location can lead to instability of the closed-loop system; however, the optimal sensor/actuator location, together with the optimal feedback control gain, can stabilize the structural control systems. In addition, the performance of both active damping control and LQ control can be maximized.

Robust output tracking for nonlinear systems with weakly non-minimum phase

Abstract: This paper is concerned with the problem of designing a robust output tracking controller for MIMO nonlinear systems with weakly non-minimum phase. Based on our system formulation, control plants with uncertainties and/or with actuator dynamics fall into the class under consideration. The controller design here is divided into two phases: fast feedback control and slow feedback control, so that a final composite control is obtained. The former is chosen to stabilize the boundary layer system, whereas the latter essentially handles the mismatched uncertainties after the system is reformulated. Under some mild assumptions, it is shown that the overall states are bounded and the tracking errors converge to a residual set whose size is a class k function of e. As e → 0, the residual set shrinks to the origin. An interesting application to a simplified aircraft model with fast actuator dynamics, which turns out to be weakly non-minimum phase, is given. The computer simulation has verified the expected satisfac...