Showing papers by "National Tsing Hua University published in 1993"

Reliability evaluation of a limited-flow network in terms of minimal cutsets

Abstract: Many systems can be regarded as flow networks whose arcs have discrete and multi-valued random capacities. The probability of the maximum flow at each various level and the reliability of such a flow network can be calculated in terms of K-lattices which are generated from each subset of the family of all MCs (minimal cutsets). However the size of such a family 2/sup m/-1 (m=number of MCs) grows exponentially with m. Such a flow network can be considered as a multistate system with multistate components so that its reliability can be evaluated in terms of upper boundary points of each level d (named d-MCs here). This work presents an algorithm to generate all d-MCs from each MC for each system capacity level d. The new algorithm is analyzed and compared with the algorithm given by J. Xue (1985). Examples show how all d-MCs are generated; the reliability of one example is computed. >

Improved moment invariants for shape discrimination

Abstract: Moment invariants used as features for shape recognition has been widely used. The moments were computed using all the information of shape boundary associated with the interior region. This paper presents the theoretical improved moments computed based only on the shape boundary. Some invariants derived from improved moments in variation to translation, rotation, and scaling are presented. The computations of improved moment invariants based on chain code representation of a shape boundary can be done in real time. Experiments of discriminating country maps, industrial tools, and printed numerals by using improved moment invariants as features via graphical plots suggest that the improved moment invariants be good shape features close to human visual processing.

A fuzzy multi-criteria decision-making approach for robot selection

Abstract: From combing the concepts of fuzzy set theory and hierarchical structure analysis, a robot selection algorithm is proposed. It is used to aggregate decision-makers' fuzzy assessments about criteria weightings and the suitability ratings of a robot vs various selection criteria to obtain fuzzy suitability indices. The suitability ratings are then ranked to select the most suitable robot. By utilizing this decision algorithm, the decision-makers' fuzzy assessments with various rating attitudes and the trade-off between various selection criteria can be taken into account in the aggregation process to ensure more convincing and accurate decision-making.

Elementary excitations in cylindrical tubules.

Abstract: A detailed study of the elementary excitations of an electron gas confined to a tubule system is presented. The system could consist either of a single cylindrical tubule or of several tubules sharing a common axis. Graphene tubules with a radius as small as 11 \AA{} have been recently realized. Essential features revealed from this study are expected to be common to the graphene tubules. The dielectric function of the quasi-one-dimensional (1D) tubular system has been evaluated exactly within the random-phase approximation, where both the intrasubband and the intersubband excitations are included. The angular momentum (L) is conserved in the tubule system. The excitations, e.g., plasmons, of different L's are thus mutually decoupled. At any given L, only a small number of plasmon branches exist, every one of which can be studied systematically. Intertubule interaction for coaxial tubules has been included. The coupling among coaxial tubules adds unique features that distinguish the tubules from other quasi-1D systems.

Effect of Sintering Aids on Microstructures and PTCR Characteristics of (Sr0.2Ba0.8)TiO3 Ceramics

Abstract: The effects of liquid-phase sintering aids on the microstructures and PTCR characteristics of (Sr0.2Ba0.8)TiO3 materials have been studied. The grain size of sintered materials monotonically decreases with increasing content of Al2O3–SiO2–TiO2 (AST). The ultimate PTCR properties with ρht/ρrt as great as 105.61 are obtained for fine-grain (10-μm) samples, which contain 12.5 mol% AST and were sintered at 1350°C for 1.5 h. The quantity of liquid phase formed due to eutectic reaction between AST and (Sr,Ba)TiO3 is presumably the prime factor in determining the grain size of samples. The grains grow rapidly at the sintering temperature in the first stage until the liquid phase residing at the grain boundaries reaches certain critical thickness such that the liquid–solid interfacial energy dominates the mechanism of grain growth.

LDV Measurements of Periodic Fully Developed Main and Secondary Flows in a Channel With Rib-Disturbed Walls

Abstract: Laser-Doppler velocimeter measurements of mean velocities, turbulence intensities, and Reynolds stresses are presented for periodic fully developed flows in a channel with square rib-disturbed walls on two opposite sides Quantities such as the vorticity thickness and turbulent kinetic energy are used to characterize the flow The investigated flow was periodic in space The Reynolds number based on the channel hydraulic diameter was 33 [times] 10[sup 4] The ratios of pitch to rib-height and rib-height to chamber-height were 10 and 0133, respectively Regions where maximum and minimum Reynolds stress and turbulent kinetic energy occurred were identified from the results The growth rate of the shear layers of the present study was compared with that of a backward-facing step The measured turbulence anisotropy and structure parameter distribution were used to examine the basic assumptions embedded in the [kappa]-[epsilon] and [kappa]-[epsilon]-A models For a given axial station, the peak axial mean-velocity was found not to occur at the center point The secondary flow was determined to be Prandtl's secondary flow of the second kind according to the measured streamwise mean vorticity and its production term

Leader election in uniform rings

Abstract: A self-stabilizing leader election protocol is proposed here for uniform rings of primal size. A ring of processors is said to be uniform if no distinguished leader processor exists. Having the proposed protocol as the first phase, all self-stabilizing protocols for nonuniform rings can be implemented as the second phase. Dijkstra's self-stabilizing mutual exclusion protocol for nonuniform rings is superimposed as an example on the leader election protocol. The result is a two-phase self-stabilizing mutual exclusion protocol for uniform rings. Let the size of the ring be n. Our self-stabilizing mutual exclusion protocol uses 3n states for each processor, which improves a previous result that uses approximately (n 2 /ln n) states

Erase and program verification circuit for non-volatile memory

Abstract: For non-volatile memory devices, such as flash EPROM integrated circuits, which have memory cells (10) and reference cells (23), and sense circuitry (27) responsive to addressed memory cells (10) and the reference cells (23), and in which a read potential is supplied to the gate of the selected memory cells and a reference potential is supplied to the gate of a reference memory cell during a read mode, the state of the programmable memory cells (10) is verified by (1) supplying a first verify potential to the gate of an address programmable memory cell; and (2) supplying a second verify potential to the gate of the reference cell which is different from the first verify potential. Because cell current is a very strong function of the gate voltage, applying different gate voltages to the memory (10) and reference cells (23) is equivalent to adjusting the sense ratio.

Investigation of the Vibration of a Blade With Friction Damper by HBM

Abstract: The friction damper has been widely used to reduce the resonant vibration of blades. The most commonly used methods for studying the dynamic behavior of a blade with a friction damper are direct integration methods. Although the harmonic balance method (HBM) is a well-known method for studying nonlinear vibration problems, generally only a one-term approximation has been proposed to study the nonlinear vibration of a frictionally damped blade. In this work, a HMB procedure with a multiterm approximation is proposed. The results show that the steady-state response and other related behavior of a frictionally damped blade can be predicted accurately and quickly by an HBM with a multiterm approximation.

Surface effects and band measurements in photonic crystals.

Abstract: An analytic study of Bloch waves near photonic crystal surfaces has been carried out. This is a generalization of Heine's theory of metal/semiconductor interfaces. The main concern of this study is how the surfaces of a finite system affect band determination--which usually involves transmission measurements on small photonic crystals. An analytic expression for transmission is obtained. The results show that the usual band measurements could lead to considerable errors, especially when they involve narrow band gaps. A possible method to improve band measurements has been suggested. The analytic surface analysis has been demonstrated to be fairly accurate, even for a small system. The theory is expected to be applicable to other surface-related problems of photonic systems.

The slab dividing approach to solve the euclidean p-center problem

Abstract: Givenn demand points on the plane, the EuclideanP-Center problem is to findP supply points, such that the longest distance between each demand point and its closest supply point is minimized. The time complexity of the most efficient algorithm, up to now, isO(n 2 p−1· logn). In this paper, we present an algorithm with time complexityO(n 0(√P)).

Flash eprom with block erase flags for over-erase protection

Abstract: A FLASH EPROM device comprises a memory array (10) organized into a plurality of blocks of memory cells. An energizing circuit applies energizing voltages to the blocks of memory cells to read and program addressed cells, and to erase selected blocks or the whole memory array (10). An erase verify circuit (12) separately verifies erasure of blocks in the plurality of block memory cells. Control logic controls the energizing circuit to re-erase blocks which fail erase verify. The control logic includes a plurality of block erase flags (13) which correspond to respective blocks of memory cells in the array (10). The erase verify is responsive to the block erase flags (13) to verify only those blocks having a set block erase flag. If the block passes erase verify, then the block erase flag is reset.

Experimental study of an injection-locked gyrotron backward-wave oscillator.

Abstract: A Ka-band gyrotron backward-wave oscillator (gyro-BWO) experiment has been performed to investigate the phase control, fast tunability, and power capability. Efficient injection locking was accomplished by novel circuit arrangements. Maximum power of 113 kW at -19% efficiency was achieved, showing favorable scaling to still higher powers. Stable voltage tuning bandwidth of 5% at 67 kW peak power was also observed. The measured performance has demonstrated a strong potential of the gyro-BWO for new applications requiring high-power tunable millimeter-wave sources

Protein Kinase FA/GSK‐3 Phosphorylates on Ser235‐Pro and Ser404‐Pro that Are Abnormally Phosphorylated in Alzheimer's Disease Brain

Abstract: Previously, we identified protein kinase FA/glycogen synthase kinase-3 (GSK-3) as a microtubule-associated protein tau kinase that can incorporate 4 mol of phosphates into 1 mol of tau protein and cause its electrophoretic mobility shift in sodium dodecyl sulfate gels, a unique property characteristic of paired helical filament-associated pathological tau (PHF-tau) in Alzheimer's disease brains. In this report, we identified TPPKS(p)PSAAK and SPVVSGDTS(p)PR as two phosphorylation site sequences phosphorylated by kinase FA/GSK-3 in tau using peptide sequence analysis and sequential manual Edman degradation for radiosequencing. When mapping with human brain tau sequence, we further identified Ser235-Pro and Ser404-Pro as the two major phosphorylation sites according to the numbering of the longest tau isoform. Ser235 and Ser404 have been reported as two of the major abnormal phosphorylation sites in PHF-tau. Taken together, the results provide initial evidence that protein kinase FA/GSK-3 may represent one of the Ser-Pro motif-directed tau kinases involved in the abnormal phosphorylation of pathological PHF-tau in Alzheimer's disease brain.

Answering heterogeneous database queries with degrees of uncertainty

Abstract: In heterogeneous database systems,partial values have been used to resolve some schema integration problems. Performing operations on partial values may producemaybe tuples in the query result which cannot be compared. Thus, users have no way to distinguish which maybe tuple is the most possible answer. In this paper, the concept of partial values is generalized toprobabilistic partial values. We propose an approach to resolve the schema integration problems using probabilistic partial values and develop a full set of extended relational operators for manipulating relations containing probabilistic partial values. With this approach, the uncertain answer tuples of a query are associated with degrees of uncertainty (represented by probabilities). That provides users a comparison among maybe tuples and a better understanding on the query results. Besides, extended selection and join are generalized to α-selection and α-join, respectively, which can be used to filter out maybe tuples with low probabilities — those which have probabilities smaller than α.

New strategy for assumed stresses for 4‐node hybrid stress membrane element

Abstract: An oblique (skew) co-ordinate system defined at the origin of the isoparametric co-ordinates is introduced as the reference co-ordinate system for assumed stresses in the formulation of a 4-node hybrid membrane element. The initially uncoupled stresses in these reference co-ordinates can be constrained to satisfy the equilibrium conditions pointwise by using the procedure of Pian and Wu7, when suitable incompatible displacements are introduced. Such strategy allows the element stiffness to be formulated by using either the Hellinger-Reissner or the complementary energy functional. Numerical results show that the performances of three elements, constructed by using different sets of incompatible displacements in this paper, are practically identical and are all of slightly higher accuracy than that of the Pian-Sumihara element6.

Learning-by-doing and the sources of productivity growth: A dynamic model with application to U.S. agriculture

Abstract: The significance of learning to productivity growth is formulated within a dynamic adjustment-cost framework Explicitly treating the acquisition of knowledge as a firm-specific capital good entering the production function along with other conventional inputs, the dynamic optimization model integrates the learning-by-doing hypothesis with technical change, scale, and disequilibrium input use effects in the aggregate productivity analysis The theoretical framework is applied to examining the dynamic components accounting for the growth of US production agriculture over the 1950–82 period The results imply a less important role for technical change and assign a substantial role to the previously unmeasured contribution of learning-by-doing to the growth of aggregate agriculture industry

Self-stabilizing depth-first token circulation on networks

Abstract: This paper proposes a self-stabilizing protocol which circulates a token on a connected network in nondeterministic depth-first-search order, rooted at a special node. Starting with any initial state in which the network may have no token at all or more than one token, the protocol eventually makes the system stabilize in states having exactly one circulating token. With a slight modification to the protocol - by removing nondeterminism in the search - a depth-first-search tree on the network can be constructed. The proposed protocol runs on systems that allow parallel operations.