Showing papers by "National Cheng Kung University published in 1988"
TL;DR: In this paper, an analysis has been carried out to determine the heat transfer occurring in the laminar boundary layer on a linearly stretching, continuous surface subject to suction or blowing.
583 citations
TL;DR: In this article, the authors considered the problem of free convection flow of a non-Newtonian power law fluid along an isothermal vertical flat plate embedded in the porous medium.
Abstract: The problem of free convection flow of a non-Newtonian power law fluid along an isothermal vertical flat plate embedded in the porous medium is considered in the present study. The physical coordinate system is shown schematically in Fig 1. In the present study, it is assumed that the modified Darcy law and the boundary layer approximation are applicable. This implies that the present solutions are valid at a high Rayleigh number. With these simplifications, the governing partial nonlinear differential equations can be transformed into a set of coupled ordinary differential equations which can be solved by the fourth-order Runge-Kutta method. Algebraic equations for heat transfer rate and boundary layer thickness as a function of the prescribed wall temperature and physical properties of liquid-porous medium are obtained. The similarity solutions can be applied to problems in geophysics and engineering. The primary purpose of the present study is to predict the characteristics of steady natural convection heat transfer using the model of the flow of a non-Newtonian power law fluid in a porous medium given by Dharmadhikari and Kale (1985). Secondly, the effects of the new power law index n on heat transfer are investigated.
155 citations
Journal Article•
TL;DR: The ability of high-resolution MR imaging to detect invasion of the cavernous sinuses by pituitary adenoma was determined through a retrospective review of 74 patients, and no feature permitted certain distinction between invasive and noninvasive microadenomas.
Abstract: The ability of high-resolution MR imaging (1.5 T) to detect invasion of the cavernous sinuses by pituitary adenoma was determined through a retrospective review of 74 patients. These patients were divided into three groups: 25 normal subjects, 24 subjects with invasive pituitary adenomas, and 25 subjects with noninvasive pituitary adenomas. A fourth group of 30 patients, who subsequently underwent surgery for pituitary adenoma, was evaluated prospectively by MR for the presence or absence of cavernous sinus invasion. Several features were analyzed: (1) the detectability of the medial and lateral dural margins of the cavernous sinus (2) the size and variation in intensity of compartments within the cavernous sinus (3) the relationship of endocrine function to the surgical and MR appearance of the cavernous sinus and (4) carotid artery displacement or encasement by tumor. The normal cavernous sinuses were usually symmetric, but their sizes varied. The lateral dural margin of the cavernous sinus was always recognized on MR as a linear, discrete, low-intensity area. The medial dural margin (pituitary capsule) was seen on MR in only two of the 25 normal patients. In all 24 patients with cavernous sinus invasion involvement was unilateral and was most common with laterally positioned prolactin or adrenocorticotropic hormone secretory adenomas. Invasion of the cavernous sinus was suspected by MR in only two of the 13 invasive microadenomas and was questionable in three. In 10 of the 11 macroadenomas with surgically proved dural invasion, MR demonstrated an asymmetric increase in size and intensity of the superior and inferior cavernous sinus compartments. Noninvasive macroadenomas compressed and displaced the cavernous sinus bilaterally. The prospective MR evaluation of 30 patients undergoing surgery for pituitary tumor revealed a sensitivity for predicting cavernous sinus invasion of 55%, a specificity of 85.7%, a positive predictive value of 62.5%, and a negative predictive value of 81.8%. No feature permitted certain distinction between invasive and noninvasive microadenomas, as the medial dural wall of the cavernous sinus could not be reliably identified. The most specific sign of cavernous sinus invasion was carotid artery encasement.
144 citations
TL;DR: In this paper, the problem of natural convection of a non-Newtonian fluid about a horizontal isothermal cylinder and an isothermal sphere in the porous medium is considered.
76 citations
TL;DR: In this paper, a numerical solution procedure has been developed to analyze gas-particle flow in a solid rocket nozzle, where the time-dependent explicit MacCormack scheme is adopted to solve the governing equations derived from the trajectory model.
Abstract: The numerical solution procedure has been developed to analyze gas-particle flow in a solid rocket nozzle. The time-dependent) explicit MacCormack scheme is adopted to solve the governing equations derived from the trajectory model. The velocity, trajectory, and temperature of the solid particles are treated with the Lagrangian approach. To study the particle diffusive velocity, which is included to account for the turbulent effect, the equation of particle number density is solved by the hybrid scheme. The results of this study indicate the level of gas-particle coupling and the differences that can be expected for the different sizes and mass fractions of particles.
69 citations
TL;DR: A functionally active human microplasminogen without kringle structures was produced by incubation of plAsminogen with urokinase-free plasmin at an alkaline pH.
68 citations
TL;DR: In this paper, the authors investigated the phenomenon in phase transfer catalysis that the reaction rate constant increased sharply when the amount of phase transfer catalyst added is beyond a certain value and found that the third liquid phase is the main portion for the phase transfer catalyze the reaction.
65 citations
TL;DR: In this article, four high-impedance fault-detection algorithms (proportional relay, ratio ground relaying, second-order harmonic current relaying and third-order HLC relaying) were simulated by mathematical models.
Abstract: Four high-impedance fault-detection algorithms-proportional relaying, ratio ground relaying, second-order harmonic current relaying, and third-order harmonic current relaying-were simulated by mathematical models. Relaying performances using staged fault data were then compared. Results of the fault data processing were used to distinguish the detection characteristics: fault identification, stability, threshold setting adaptability, transient recovery characteristic, and availability. The operations of a ground overcurrent relay and a ratio ground relay were also checked in the test. The results can be used as a reference for the development of a reliable high-impedance fault detector. >
63 citations
TL;DR: In this paper, a finite element model is applied to the vibration and stability of a rotating blade with a single edge crack, and the effects of transverse shear deformation and rotatory inertia are taken into account.
61 citations
TL;DR: In this paper, the dielectric properties of the (Zr0,8Sn0,2)TiO4 ceramic with a homogeneous phase are investigated and two kinds of TiO2 phase of raw material in comparison show that anatase phase is clearly better than rutile phase for higher unload Q. Among these additives, CdO and La2O3 are regarded as a firing agent and Ni as a grain growth enhancer.
60 citations
TL;DR: In this article, a general finite element model is proposed to deal with dynamic theromelastic problems especially with longer transient period, which consists of formulating and solving the problem in the Laplace transform domain by the Finite Element Method (FEM) and then numerically inverting the transformed solution to obtain the time-domain response.
Abstract: A general finite-element model is proposed to deal with dynamic theromelastic problems especially with longer transient period. The method consists of formulating and solving the problem in the Laplace transform domain by the Finite Element Method (FEM) and then numerically inverting the transformed solution to obtain the time-domain response. Therefore, the transient solutions at any time could be evaluated directly. A number of examples are presented which demonstrate the accuracy, efficiency, and versatility of the proposed method, and show the effects of relaxation times, inertia, and thermoelastic coupling terms.
TL;DR: In this paper, an a-Si/SiC:H superlattice avalanche photodiode (SAPD) was successfully fabricated on an ITO/glass substrate by plasmaenhanced chemical vapor deposition.
Abstract: An a-Si/SiC:H superlattice avalanche photodiode (SAPD) has been successfully fabricated on an ITO/glass substrate by plasma-enhanced chemical vapor deposition. The room-temperature electron and hole impact ionization rates, alpha and beta , have been determined for the a-Si/SiC:H superlattice structure by photocurrent multiplication measurements. The ratio alpha / beta is 6.5 at a maximum electric field of 2.08*10/sup 5/ V/cm. Avalanche multiplications in the superlattice layer yields an optical gain of 184 at a reverse bias V/sub R/=20 V and an incident light power P/sub in/=5 mu W. An LED-SAPD photocouple exhibited a switching time of 4.5 mu s at a load resistance R-1.8 k Omega . >
21 Aug 1988
TL;DR: Two SECC schemes are proposed in this paper, the first is a block encryption using Preparata based nonlinear codes; the second one is based on block chaining technique, which can be secure.
Abstract: A secret error-correcting coding (SECC) scheme is one that provides both data secrecy and data reliability in one process to combat with problems in an insecure and unreliable channel. In an SECC scheme, only the authorized user havingsecretly held information can correct channel errors systematically. Two SECC schemes are proposed in this paper. The first is a block encryption using Preparata based nonlinear codes; the second one is based on block chaining technique. Along with each schemes can be secure.
01 Sep 1988-Graphical Models \/graphical Models and Image Processing \/computer Vision, Graphics, and Image Processing
TL;DR: An automatic understanding system using the techniques of image processing, pattern recognition, and artificial intelligence has been developed for electronic circuit diagrams to extract three categories of essential components: circuit symbols, characters, and connection lines.
Abstract: An automatic understanding system using the techniques of image processing, pattern recognition, and artificial intelligence has been developed for electronic circuit diagrams. Part of the system is presented to extract three categories of essential components: circuit symbols, characters, and connection lines. Each essential component consists of a set of picture segments which are appropriately detected by a segment tracking algorithm. A heuristic piecewise linear approximation algorithm is proposed to approximate picture segments for primitive recognition. On the basis of topological context, a one-pass manner called the relational best search method applies a depth first search technique uniting a set of specified rules during the traversal of a circuit diagram. This method combines the constituents of each circuit symbol or character into a cluster. All the clusters together with the remaining components are extracted and grouped into the three categories as soon as the traversal is finished. A variety of electronic circuit diagrams have been used for testing the component extractor. So far, the present extractor has shown favorable results.
01 Dec 1988
TL;DR: In this paper, the authors applied the finite element method to study the effect of moisture and temperature on the stability of a general orthotropic cylindrical composite shell panel subjected to axial or in-plane shear loading.
Abstract: The finite element method is applied to study the problem of moisture and temperature effects on the stability of a general orthotropic cylindrical composite shell panel subjected to axial or in-plane shear loading. The element employed is a nine-node isoparametric shell element. As the hygrothermal effects on the elastic properties of the matrices and the fibers are very different, the degradation of elastic moduli, the transverse shear effect and the induced initial stress are all considered. Numerical investigation shows that if the temperature increases from 300 to 422 K and the moisture concentration is saturated, the buckling load with both the degradation of elastic moduli and transverse shear deformation considered is ca . 12% lower than Snead and Papazotto's result where only the degradation of elastic moduli was considered. In addition, it is shown that the influence of the initial stress, induced by the same environmental variations, on the buckling load is far less significant.
TL;DR: Rhinacanthin-A and -B, two new naphthoquinones, and the known lupeol, β-sitosterol, stigmasterol, as well as the glucosides of β-Sitosterol and stig masterol were isolated from the roots of Rhinacanthus nasutus.
TL;DR: In this paper, a robust state feedback controller design in the time domain is developed for parametrically perturbed linear systems with time delay, where the properties of the matrix measure and comparison theorem are employed to investigate the robust stability conditions of systems with linear structured or unstructured perturbations.
Abstract: A new robust state feedback controller design in the time domain is developed for parametrically perturbed linear systems with time delay. The properties of the matrix measure and comparison theorem are employed to investigate the robust stability conditions of systems with linear structured or unstructured perturbations. A method is proposed to design the robust state feedback controller to satisfy the robustness requirement. Examples are given to illustrate the proposed method.
TL;DR: In this article, the performance of finite width journal bearings with micropolar and newtonian fluids was analyzed by using the finite difference method to solve the generalized three-dimensional Reynolds equation.
TL;DR: In this article, the temperature distribution in a visco-elastic fluid of Walters' liquid B model over a horizontal stretching plate is investigated. But the results are expressed in terms of Kummer's functions.
TL;DR: In this paper, a graph representation of multiple joints is introduced and the modified Euler formula is derived, and the number of kinematic chains with one and two multiple joints up to ten links is listed.
TL;DR: In this article, the authors present adiabatic solutions for a finite width hydrodynamic journal bearing with non-newtonian lubricants, obeying the power-law model.
TL;DR: The Boolean n-cube network is proved to have the super-line-connectivity property and the reliability function for large failure rate can be readily computed.
Abstract: Two graph-theoretic results concerning Boolean n-cube network reliability are presented. First, a simple formula for the number of spanning trees of the Boolean n-cube network is derived. As a result, the reliability function for large failure rate can be readily computed. Second, the Boolean n-cube network is proved to have the super-line-connectivity property. Thus the number of line-disconnecting sets (a set of lines the removal of which results in a disconnected or trivial graph) or order lambda for the Boolean n-cube network is equal to 2/sup n/. >
TL;DR: In this paper, an analysis of the flow and vortex instability of natural convection in a porous medium is performed, and the results indicate that the Nusselt number and Sherwood number are higher than those for pure thermal convection and the flow is more susceptible to vortex instability.
TL;DR: The results indicate that the activity of 5‐HT nerve cells adjacent to the ventrolateral surface of the medulla oblongata and projecting to the spinal cord serves to elevate pain threshold.
Abstract: The antinociceptive role of spinal serotonin (5-HT) neurons descending from 5-HT cells near the ventrolateral surface of the medulla oblongata was investigated by stimulating these cells in normal rats, in rats with generalized or selective chemical ablation of 5-HT nerves, and in rats with postsynaptic blockade of 5-HT receptors Electrical stimulation of the lateral medulla elicited analgesia in normal rats; the increase in pain threshold was proportional to the intensity and to the frequency of stimulation In addition, microinjection of kainic acid or l -glutamate at the same sites also produced analgesia However, generalized destruction of CNS 5-HT nerves produced by intraventricular injection of 5,7-dihydroxytryptamine (5,7-DHT) or selective destruction of spinal 5-HT nerves produced by intraspinal injection of 5,7-DHT reduced the magnitude of the antinociceptive responses to electrical stimulation Postsynaptic blockade of CNS 5-HT receptors produced by intraventricular injection of cyproheptadine also reduced the stimulation-produced analgesia The specificity of the lesions for 5-HT nerves is demonstrated by the lack of effect on the levels of noradrenaline in the same brain regions The results indicate that the activity of 5-HT nerve cells adjacent to the ventrolateral surface of the medulla oblongata and projecting to the spinal cord serves to elevate pain threshold
TL;DR: In this paper, an implicit finite difference method is used to analyze the natural convection boundary layer flow in a saturated porous medium resulting from combined heat and mass buoyancy effects adjacent to an inclined surface.
TL;DR: In this paper, a cation-exchange membrane was used for the selective separation of nickel and copper in a batch dialyzer, which enabled determination of the enrichment factor and the separation factor.
TL;DR: An acetone extract of root bark of Citrus grandis Osbeck gave a new flavone, honyucitrin, and a new coumarin, Honyudisin, together with nine known coumarins and 11 acridone alkaloids as mentioned in this paper.
TL;DR: In this article, the adaptive grid method is used to solve the problem of flow in a channel with a sudden expansion and natural convection in an enclosed square cavity, where the grid distribution is adapted to the different characteristics of laminar and turbulent flows.
Abstract: Recently the concept of adaptive grid computation has received much attention in the computational fluid dynamics research community. This paper continues the previous efforts of multiple one-dimensional procedures in developing and asessing the ideas of adaptive grid computation. The focus points here are the issue of numerical stability induced by the grid distribution and the accuracy comparison with previously reported work. Two two-dimensional problems with complicated characteristics—namely, flow in a channel with a sudden expansion and natural convection in an enclosed square cavity—are used to demonstrate some salient features of the adaptive grid method. For the channel flow, by appropriate distribution of the grid points the numerical algorithm can more effectively dampen out the instabilities, especially those related to artificial boundary treatments, and hence can converge to a steady-state solution more rapidly. For a more accurate finite difference operator, which contains less undesirable numerical diffusion, the present adaptive grid method can yield a steady-state and convergent solution, while uniform grids produce non-convergent and numerically oscillating solutions. Furthermore, the grid distribution resulting from the adaptive procedure is very responsive to the different characteristics of laminar and turbulent flows. For the problem of natural convection, a combination of a multiple one-dimensional adaptive procedure and a variational formulation is found very useful. Comparisons of the solutions on uniform and adaptive grids with the reported benchmark calculations demonstrate the important role that the adaptive grid computation can play in resolving complicated flow characteristics.
TL;DR: In this paper, a new bioglass ceramic with composition of Na2O 12, CaO 28, P2O5 10% and SiO2 50% with a high bending strength (120-140 MPa) and compressive strength (600-750 MPa), was studied.
Abstract: A new bioglass ceramic with composition of Na2O 12%, CaO 28%, P2O5 10% and SiO2 50% with a high bending strength (120–140 MPa) and compressive strength (600–750 MPa) was studied. The crystallized phases ofβ-Ca2P2P7 and Na2Ca3Si6O16 were determined by X-ray diffraction. Optical microscopy of the material revealed that a very uniform crystal size of about 30 μm was obtained with high nucleation frequency. The nucleation and crystallization processes were also investigated. The rat shoulder test showed that the material formed a tight chemical bond with biological texture and had good biocompatibility.