Browsing by Issue Date, starting with "1997-10-01"

Now showing 1 - 20 of 83401

Lifetime and compactness of range for super-Brownian motion with a general branching mechanism
(1997-10-01)
Sheu, YC
;
交大名義發表
;
應用數學系
;
National Chiao Tung University
;
Department of Applied Mathematics
Let X be a super-Brownian motion with a general (time-space) homogeneous branching mechanism. We study a relation between lifetime and compactness of range for X. Under a restricted condition on the branching mechanism, we show that the set X survives is the same as that the range of X is unbounded. (For alpha-branching super-Brownian motion, 1 < alpha less than or equal to 2, similar results were obtained earlier by Iscoe (1988) and Dynkin (1991).) We also give an interesting example in that case X dies out in finite time, but it has an unbounded range. (C) 1997 Elsevier Science B.V.
Plasma transferred are repair welding of the nickel-base superalloy IN-738LC
(1997-10-01)
Su, CY
;
Chou, CP
;
Wu, BC
;
Lih, WC
;
機械工程學系
Plasma transferred are welding (PTA) has been considered a promising process tea restore worn areas of land-based gas turbine blades and vanes. The objective of this investigation was to study the effect of PTA welding on the repairing of IN-738LC superalloy components, Tensile tests were conducted on specimens welded with various combinations of parameters, Room temperature, 760 degrees C, and 980 degrees C were selected Its tensile test temperatures, High-temperature phase transformed, during solidification, were identified by differential thermal analysis (DTA), The weld-pool shapes and microstructures of welded specimens prepared by various welding parameters were evaluated by optical metallography (OM), a scanning electron microscope (SEM) equipped with energy dispersive x-ray spectrometer (EDS), and microhardness testing. Results of this study showed that PTA welded specimens exhibited 96% nominal tensile strength of IN-738LC base materials, Specimen failure was observed predominantly in the base materials instead of in the heat-affected zone (HAZ) for gas tungsten are weld (GTAW) repair weldments, IN-738LC is considered susceptible to weld cracking during fusion welding; however, using a low-input heat repair welding process (PTA), cracking susceptibility could be minimized by the optimized welding parameters.
Transformation models for interval scale grouped data with applications
(1997-10-01)
Lu, HHS
;
Hsieh, FS
;
統計學研究所
;
Institute of Statistics
Interval scale grouped data have peculiar structures of their own rights among various archetypes of polytomous data that deserve special statistical treatments. Maximum likelihood type approaches along with heteroscedastic and transformation models are adapted to take into account this kind of architecture with current state-of-art computation capabilities. Meanwhile, misclassification rates instead of sum of squared residuals are suggested for model fitting and selection in light of the data formation. Successful applications of these methods are demonstrated by a set of empirical data regarding the endotracheal tube size selection for small children in the emergency room of a hospital.
A new power collection architecture for future spacecraft
(1997-10-01)
Kuo, MY
;
Kuo, MS
;
Kuo, CC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The generalized tree-like transmission line network system having n layers in total with m-to-1 branch connection at each joint (T-TLNS-n-m) is proposed to replace the traditional series-parallel combined dc networks to automatically accumulate identically distributed power cells into the large amount of useful power for the spacecrafts, The proposed system has the attractive features of simple structure, easy construction and maintenance, and low cost, because two kinds of parts, ac current sources and m-to-1 transmission line (TL) branch connection parts, are used in the whole system. A method of implementing ac current cells having high output impedance is proposed to improve the power collection efficiency of the whole network system. Simulated results show that that low-pass nominal pi- or T-circuit with high characteristic impedance, which is used for the voltage source to current source converter in the current cell, improves the efficiency of the voltage inverter, filters out the harmonics, and increases the output impedance of the whole current cell.
Design of a rule-based flexible manufacturing system controller using modified IDEF0 methodology
(1997-10-01)
Chen, SG
;
Wu, MZ
;
Li, RK
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This article proposes a new method to design a rule-based FMS controller. This approach adopts modified IDEFO (MI) diagrams as a graphical representation of the production rules. Initially, the material flows or functional requirements for the FMS are specified by synthesizing the MI diagram primitives. The control flows for the FMS are then created by a number of transformation rules. The manufacturing policy, e.g. deadlock avoidance policy, is also specified and attached. The MI diagrams are therefore transformed to the final MI (FMI) diagrams which can be directly transformed to the production rules. Thus, a concise rule-based FMS controller is developed. The fact that the production rules are created by systematic transformation eliminates any redundant, contradictory, or unnecessary rules. Two approaches can verify the consistency of the designed FMS controller. The controlled Petri net approach can be adopted for verifying a small system, while a simulation approach is preferable for verifying a large system. By iterating the process, a feasible rule-based FMS controller can be systematically developed. This method not only provides graphical representations to construct well-organized production rules, but also includes a systematic transformation of the control flows for an FMS controller.
Phase diagram of crystals of dusty plasma
(1997-10-01)
Lee, HC
;
Chen, DY
;
Rosenstein, B
;
電子物理學系
;
Department of Electrophysics
Dust particles effectively charged by plasma recently have been optically observed to exhibit crystalline phases not expected of Wigner or Yukawa crystals. Under varying conditions the crystal sometimes appears as deformed and oriented three-dimensional close-packed lattices of bcc, fcc, or hcp type, but mostly as a triangular array of vertical chains of particles. The unusual phases are shown to be caused by dipole-dipole interactions. The dipole moments are induced on the dust particles by gravity and by drag forces generated by ion stream. We describe in detail stable lattice structures and present the highly complex phase diagram of the dusty plasma. It turns out that in large parts of the phase diagram the stable phases indeed correspond to chains, but particles in neighboring chains belong to different sublattices. The stability of the lattices against excitations due to compression (i.e., aspect ratio variations) and vibration (i.e., phonons or charge density waves) is established.
Signed degree sequences of signed graphs
(1997-10-01)
Yan, JH
;
Lih, KW
;
Kuo, D
;
Chang, GJ
;
應用數學系
This paper gives necessary and sufficient conditions for an integral sequence to be the signed degree sequence of a signed graph or a signed tree, answering a question raised by Chartrand et al. (1994). (G. Chartrand, H. Gavlas, F. Harary, and M. Schultz, On signed degrees in signed graphs, Czech. Math. J.44 (1994), 677-690). (C) 1997 John Wiley & Sons, Inc.
Mode distinction and radiation-efficiency analysis of planar leaky-wave line source
(1997-10-01)
Lin, YD
;
Sheen, JW
;
交大名義發表
;
傳播研究所
;
National Chiao Tung University
Using the first microstrip-line higher order mode as an example, mode distinction and radiation efficiency of leaky-wave line sources in the radiation region are presented in this paper, The spectral-domain approach is used to calculate complex power hows, leaving the line source in the transverse directions and those guided down the line source. Ply observing the behavior of these complex power flows in different frequency regions, the leaky-wave line source can be distinguished into the antenna mode and the reactive mode in the radiation region, Experimental results are shown to confirm this mode distinction, Moreover, by comparing the power carried away by the surface and the space waves, radiation efficiency of the first microstrip-line higher order mode of various structural parameters is analyzed. The microstrip line is more efficient as a leaky-wave line source when its substrate is thin, the dielectric constant of the substrate is low, and the antenna main,cam is away from the end-fire direction.
The instability characteristics of amorphous silicon thin film transistors with various interfacial and bulk defect states
(1997-10-01)
Cheng, HC
;
Tsai, JW
;
Huang, CY
;
Luo, FC
;
Tuan, HC
The instability characteristics of hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs) with various interfacial and bulk defect states were systematically investigated. It was found that, under positive bias stresses; the threshold voltage shifts of a-Si:H TFT's with the same interfacial defect states but with different bulk defect states exhibited similar threshold voltage shift characteristics. In contrast, a-Si:H TFTs with different interfacial defect states but the same bulk defect states showed threshold voltage shifts proportional to the interfacial defect states under positive bias stresses. Furthermore, both the above kinds of a-Si:H TFT under positive bias stresses exhibited that the subthreshold swing shift characteristics closely related to both the interfacial and bulk defect states.
Implementation of an active headset by using the H-infinity robust control theory
(1997-10-01)
Bai, MS
;
Lee, D
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
This paper presents a methodology for implementing an active headset by using H-infinity robust control theory. The adopted structure is feedback tracking control. Performance, stability, and robustness of the closed-loop system have been taken into account in the design procedure by using a general framework of the H-infinity theory. The resultant controller is realized on the basis of operational amplifier circuitry. Experiments are conducted to test the developed headset. The result shows that the headset achieves broadband attenuation up to approximately 15 dB in the band 200-800 Hz. The design considerations indicated in the experimental result are also addressed. (C) 1997 Acoustical Society of America. [S0001-4966(97)05709-3] PACS numbers: 43.50.Ki, 43.38.Si [GAD].
Transformation models for interval scale grouped data with applications
(1997-10-01)
Lu, HHS
;
Hsieh, FS
;
統計學研究所
;
Institute of Statistics
Interval scale grouped data have peculiar structures of their own rights among various archetypes of polytomous data that deserve special statistical treatments. Maximum likelihood type approaches along with heteroscedastic and transformation models are adapted to take into account this kind of architecture with current state-of-art computation capabilities. Meanwhile, misclassification rates instead of sum of squared residuals are suggested for model fitting and selection in light of the data formation. Successful applications of these methods are demonstrated by a set of empirical data regarding the endotracheal tube size selection for small children in the emergency room of a hospital.
Clustered affinity scheduling on large-scale NUMA multiprocessors
(1997-10-01)
Wang, YM
;
Wang, HH
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
Modern shared-memory multiprocessors have high and non-uniform memory access (NUMA) costs. The communication cost gradually dominates the source of parallel applications' execution. Algorithms based on affinity, like affinity scheduling algorithm (AFS), perform better than dynamic algorithms, such as guided self-scheduling (GSS) and trapezoid self-scheduling (TSS). However, as the number of processors increases, AFS suffers heavy overheads for migrating workload. The overheads include remote reads to the queues for the indices information, synchronous writes to the queues for migrating iterations, and the time in loading data into cache. In this paper, we propose a new loop scheduling algorithm, clustered affinity scheduling (CAFS), to improve affinity scheduling algorithm. We distribute the processors into several clusters, and cluster-based migrations are carried on when imbalance occurs. We confirm our idea by running many applications under a realistic hierarchy memory simulator. Our results show that CAFS reduces at least 1/3 of both remote reads and synchronous writes to the queues under most applications. CAFS also improves the cache hit ratios, and balances the workload. Therefore, we conclude that under large NUMA multiprocessor, CAFS is a better choice among loop scheduling algorithms. (C) 1997 Elsevier Science Inc.
Modelling and measurement of UHF radio propagating through floors in a multifloored building
(1997-10-01)
Tarng, JH
;
Perng, DW
;
電信工程研究所
;
Institute of Communications Engineering
A general three-dimension theoretical model is developed to predict the path loss of UHF radio propagation through floors in a multifloored building. The computed propagation loss is compared with the measured value of 900 MHz, 1.4 GHz, 1.9 GHz, and 2.44 GHz and gives a reasonable agreement. It is found that the floor, lateral beams and the walls around the receiver are the major construction features to affect the estimation of the penetration loss through floors.
Varactor-tuned Gunn diode voltage controlled oscillator antenna array
(1997-10-01)
Lee, SH
;
Jou, CF
;
Lee, CP
;
Hu, CC
;
傳播研究所
A simple varactor tuned X-band Gunn diode VCO antenna array which is strongly coupled has been demonstrated. These arrays have the advantages of simple biasing circuit, no resistors required to eliminate multimode problem and suitable for monolithic integration circuit. Preliminary results show a maximum tuning range of 47MHz for 1x1 array and 170MHz for 2x2 array. In order to solve power combining heating problem, we move the backside metal forward and it becomes a microstrip form. The measured frequency and radiation patterns of these grid arrays agree very well with theoretical calculations.
Investigation of the evolution of YBa2Cu3O7-delta films deposited by scanning pulsed laser deposition on different substrates
(1997-10-01)
Wu, KH
;
Chen, SP
;
Juang, JY
;
Uen, TM
;
Gou, YS
The evolution of surface morphology of YBa2Cu3O7-delta (YBCO) thin films with sequential thickness ranging from 2 to 250 nm on (110) NdGaO3, as-polished and annealed (110) SrTiO3 and (100) MgO substrates has been systematically investigated with atomic force microscopy (AFM) to elucidate the effects of lattice mismatch, pre-annealing treatment and substrate orientation on the growth mechanism of YBCO films. A scanning pulsed laser deposition system, which has been used to produce 50-mm-diameter thin films, allows us to deposit (001) or (103) YBCO films with various thicknesses on separated substrates in a single run under essentially identical deposition conditions. The AFM images show that (001) YBCO films grown on NdGaO3 follow the Stranski-Krastanov (layer then island growth) mode, while films grown on as-polished MgO and on annealed MgO follow the Volmer-Weber (island without layer growth) mode and step-flow mode, respectively. On the other hand, the evolution of (103) YBCO films grown on both as-polished and annealed (110) SrTiO3 substrates reveals the similar step-flow growth along tilt steps, i.e. the growth proceeds with the c-axis of YBCO along [100] or [010] directions of substrate. The formations of distinct elongated grains and microcracks in planar view of such films are also discussed. (C) 1997 Elsevier Science B.V.
Call performance for a PCS network
(1997-10-01)
Fang, YG
;
Chlamtac, I
;
Lin, YB
;
資訊工程學系
;
Department of Computer Science
It is well known that, due to the mobility of a portable and limited channel availability, calls of portables may not be completed due to being blocked or terminated during the call initiation or the handover process, The characteristics of the call-completion and call holding times for both a complete call and an incomplete call are of critical importance for establishing the actual billing process in the PCS network. In this paper, we derive the call-completion probability (hence, call-dropping probability) and the effective call-holding time distributions for complete/incomplete calls with a general cell-residence time and a general call-holding time are analyzed, and. general computable formulas are obtained, We show that when fall-holding times are Erlang distributed, easy-to-compute formulas for the probability of a call completion and the expected effective call-holding times for both a complete call and an incomplete call can be derived.
From ''multi-system nations'' to ''linkage communities'': A new conceptual scheme for the integration of divided nations
(1997-10-01)
Wei, Y
;
交大名義發表
;
National Chiao Tung University
Studies of the issues related to the unification of ''divided nations'' have focused too heavily on the political and legal sides of the problem. Frequently, analyses have been clouded by concepts of conventional international law such as ''sovereignty'' and ''jurisdiction.'' Moving beyond the innovative concept of ''multi-system nations'' coined by this author in the 1970s, the idea of ''linkage communities'' emphasizes the natural process of economic, cultural, and people-to-people exchanges between different parts of a ''divided nation.'' The conceptual scheme argues that through continuous interactions in the private sectors, ''linkage communities'' will be developed within both sides of a divided nation which in turn Will bring about gradual functional integration, if not political unification of a divided state.
Vision-based autonomous land vehicle guidance in outdoor road environments using combined line and road following techniques
(1997-10-01)
Chen, KH
;
Tsai, WH
;
資訊工程學系
;
Department of Computer Science
An intelligent approach to autonomous land vehicle (ALV) guidance in outdoor road environments using combined line and road following and color information clustering techniques is proposed. Path lines and road boundaries are selected as reference models, called the line-model and the road-model, respectively. They are used to perform line-model matching (LMM) and road-model matching (RMM) to locate the ALV for line and road following, respectively. If there are path lines in the road, the LMM process is used to locate the ALV because it is faster than the RMM process. On the other hand, if no line can be found in the road, the RMM process is used. To detect path lines in a road image, the Hough transform is employed, which does not take much computing time because bright pixels in the road are very few. Various color information on roads is used for extracting path lines and road surfaces. And the ISODATA clustering algorithm based on an initial-center-choosing technique is employed to solve the problem caused by great changes of intensity in navigations. The double model matching procedure combined with the color information clustering process enables the ALV to navigate smoothly in roads even if there are shadows, cars, people, or degraded regions on roadsides. Some intelligent methods to speed up the model matching processes and the Hough transform based on the feedback of the previous image information are also presented. Successful navigations show that the proposed approach is effective for ALV guidance in common roads. (C) 1997 John Wiley & Sons, Inc.
Pulsed KrF laser annealing of Ni/Si0.76Ge0.24 films
(1997-10-01)
Luo, JS
;
Lin, WT
;
Chang, CY
;
Tsai, WC
;
電子工程學系及電子研究所
Pulsed KrF laser annealing can suppress the island structure formation and Ge segregation associated with the interfacial reactions of Ni/Si0.76Ge0.24 For the Ni/Si0.76Ge0.24 films annealed at an energy density of 0.1-0.3 J/cm(2) nickel germanosilicide associated with the amorphous overlayer was formed, while at energy densities above 0.4 J/cm(2) cellular structures of Ge-deficient S1-xGex islands surrounded by Ni(Si1-xGex)(2) due to the constitutional supercooling occurred. For the continuous Ni(Si1-xGex) films grown at 200 degrees C, subsequent laser annealing at a higher energy density of 0.6-1.0 J/cm(2) caused transformation into homogeneous Ni(Si0.76Ge0.24)(2) films without island structure and Ge deficiency which readily appeared on furnace annealing at temperatures above 400 degrees C. At energy densities above 1.6 J/cm(2) the same cellular structures as described above were also noted. (C) 1997 American Institute of Physics.
Resolving feature interactions in 3D part editing
(1997-10-01)
Perng, DB
;
Chang, CF
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Feature-based design approach has been regarded as a promising approach for 3D parts design. However, the critical issues of modifying a part design by 3D features have not yet evoked sufficient discussion. This paper aims to address issues of feature interaction, especially for enclosure and intersection, among the modified feature and the other existing features. An efficient new approach to solve the feature interaction problems encountered in part-editing is proposed. The parts are assumed to consist of subtractive volume-features only. A set of rules that facilitate updating the B-rep data and feature-based representation of the part are devised. Computer simulation examples are given to show that the proposed approach is both feasible and effective. This research contributes to several aspects of feature-based design research, especially to the area of providing simple feature-based commands. (C) 1997 Elsevier Science Ltd.