Browsing by Author "Wang, HC"

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A new analysis of direct-sequence pseudonoise code acquisition on Rayleigh fading channels
(2001-11-01)
Sheen, WH
;
Wang, HC
;
電信工程研究所
;
Institute of Communications Engineering
Accurate performance evaluation of direct-sequence pseudonoise code acquisition on Rayleigh fading channels is investigated in this paper. For fading channels the homogeneous Markov chain model, used to characterize the acquisition process over additive white Gaussian noise channels, is no longer valid due to the correlations between cell detections incurred by fading. Hence, the traditional direct and now-graph approaches for performance evaluation of the code acquisition are not applicable to fading channels. In this paper, a new analysis is proposed for accurate evaluation of the acquisition performance on Rayleigh fading channels. The analysis is quite general and can include various search strategies, types of correlators, and test methods with different performance measures: probability mass function and/or moments of acquisition time. Analytical and simulation results show that the new method predicts the acquisition performance very accurately.
A Web-based data extraction system for supply chain management-using SAP R/3
(2002)
Chen, RS
;
Wang, HC
;
Wang, CM
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資訊管理與財務金融系註：原資管所+財金所
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Department of Information Management and Finance
This paper presents a prototype of logistics flows and information extraction system between customers and vendors by using World Wide Web (WWW), XML with SAP R/3 programming technology (ABAP/4 Language). Three kinds of benefits are approved for most of the supply chain system. ( 1) To resolve the SAP SAPLPD performance issue existing in the Multi-Bytes Character Print with SAPWIN by developing a HTML Layout Set for the report printout. ( 2) To support business process improvement for customer services, logistics, planning and manufacturing through XML data interface embedded in the software solutions. ( 3) To provide a reliable and scalable information technology infrastructure which could fulfill the requirements of data transparency and data consistency. The result of this paper, we demonstrate an open architecture of data extraction method. It can be used in data transparency and data consistency for a supply chain. Enterprise within multi database can improve the performance of information flows. It can solve data printing problem in many types of layout set to meet the demand of enterpris.
Airflow velocity effects on air bearing with grooved disk surface in near-field optical disk drives
(2006-05-01)
Wang, HC
;
Liu, TS
;
機械工程學系
;
Department of Mechanical Engineering
By means of an air bearing, the pickup head slider of a near-field optical disk drive flies above data tracks on a rotating disk surface to achieve a stable flying height. The influence of airflow velocities of the air bearing on lift force deserves investigation, as the airflow velocity varies during track seeking or disk speed variation. In this study, a direct simulation Monte Carlo method is used to investigate three-dimensional nanoscale gas film lubrication at the air bearing between a slider and a rotating disk. This study aims to investigate air bearing behavior at different airflow velocities. Computational results show that faster flow generates larger pressure and lift force. Lower flying height reduces force variation caused by different velocities. This study also proposes a method for maintaining the flying height within the near-field range. (C) 2006 American Institute of Physics.
Fabrication and characterization of the conic diamond field emission arrays with gated structure
(2000-04-01)
Chen, CF
;
Wang, HC
;
Hsieh, HC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this study, we successfully fabricate conic diamond field emitter array devices by applying an IC process capable of forming a metal-insulator-semiconductor (MIS) diode structure. The conic diamonds are selectively deposited and, ultimately, grow inside of the electric gates. In addition, the field emission current is measured when applying +1000V voltage on the anode in which the applied gate voltage is varied from 0 to 50 volts. Experimental results indicate that the threshold voltage of this device is about 12 V, and the field emission current is about 40 mu A when the gate voltage is 30 V. Furthermore, current-voltage (I-V) characterization of the electrical properties demonstrates that the reason fur the change of the threshold voltage of conic diamond held emission arrays (FEAs) fabricated under different CH4 concentration may be attributed to the diamond tip radius.
Low temperature (850 degrees C) two-step N2O annealed thin gate oxides
(1996)
Lai, CS
;
Lee, CL
;
Lei, TF
;
Chao, TS
;
Peng, CH
The electrical characteristics of thin gate dielectrics prepared by low temperature (850 degrees C) two-step N2O nitridation (LTN) process are presented. The gate oxides were grown by wet oxidation at 800 degrees C and then annealed in N2O at 850 degrees C. The oxide with N2O anneal, even for low temperature (850 degrees C), had nitrogen incorporation at oxide/silicon interface. The charge trapping phenomena and interface-state generation (Delta D-itm) induced by constant current stressing were reduced and charge-to-breakdown (Q(bd)) under constant current stressing was increased. This LTN oxynitride was used as gate dielectric for N-channel MOSFET, whose hot-carrier immunity was shown improved and reverse short channel effect (RSCE) was suppressed.
Quadratic time domain BEM formulation for 2D elastodynamic transient analysis
(1997-01-01)
Wang, CC
;
Wang, HC
;
Liou, GS
;
土木工程學系
;
Department of Civil Engineering
An accurate and efficient time domain BEM for the 2D elastodynamic wave transient analysis method is presented. Emphasis is focused on developing time domain fundamental convoluted kernels and methodology for quadratic temporal solution procedures which have never been presented before. In the presented BEM method, called the QC method, the temporal variations of displacement and traction are assumed to be quadratic and constant, respectively. The spatial variations of displacement and traction fields are assumed to be quadratic. Also, the LC method, assuming linear temporal variation of displacement field and constant temporal variation of traction field, is examined in the paper. For the verification of the QC method, rectangular bars subject to different end loads are studied. The numerical results by the QC method are compared with analytical solutions and those by the LC method. Numerical study reveals that the QC method is more accurate and stable. In the QC method, a good numerical result can still be obtained even when beta=1.0-2.0. However beta=0.50-0.75 should be used in the LC method in order to obtain good numerical results. This would provide evidence that the QC method has great advantages over the LC method. Some conclusions regarding the QC method are also made. Copyright (C) 1996 Elsevier Science Ltd.
Study of air bearing with grooved disk surface in near-field optical disk drives
(2005-02-01)
Wang, HC
;
Liu, TS
;
Chang, CS
;
機械工程學系
;
Department of Mechanical Engineering
To achieve stable flying height of a pickup head in near-field optical disk drives, the influence of disk grooves on the airflow of an air bearing deserves investigation, since at a very low flying height, groove geometry is comparable to the flying height. This paper aims to compare air bearing airflows between near-field optical disks with grooved surface and conventional disks without grooved surface. Computational results show that grooved disks generate smaller pressure than smooth disks since grooves can accommodate air molecules and tune air pressure. Flying higher makes pressure magnitudes closer between grooved disks and smooth disks in negative pressure area on slider bottoms. Further, track pitches and groove depths essentially do not affect pressure at rails.
The effect of laser wavelength on the photorefractive characteristics of PMDA-DR19 based photorefractive polymeric materials
(1997-09-01)
Chang, CJ
;
Wang, HC
;
Liao, GY
;
Whang, WT
;
Liu, JM
The photoconductivity and photorefractive characteristics of PMDA-DR19-based photoconducting nonlinear optical polymeric films with different compositions were studied using red and green lasers. Contributions of dopants and the host to the photoconductive and photorefractive properties are systematically discussed. The virgin nonlinear optical material PMDA-DR19 was neither photoconductive nor photorefractive in nature. However, it became photoconductive and photorefractive once the charge transport material was incorporated into the PMDA-DR19/PVB polymer film. Films containing more nonlinear optical chromophore exhibited higher diffraction efficiency. Response speed was further elevated when an additional charge generation material was doped in. Diffraction grating was observed under zero electric field and was confirmed due to a photorefractive effect by the two-beam coupling effect. In addition to composition modification, the laser light source was also an important factor in changing the PR response speed. The photorefractive response speed was tremendously improved when films were written and read by two different laser beams, either red/green lasers or green/red lasers. (C) 1997 Elsevier Science Ltd.
The effect of laser wavelength on the photorefractive characteristics of PMDA-DR19 based photorefractive polymeric materials
(1997-09-01)
Chang, CJ
;
Wang, HC
;
Liao, GY
;
Whang, WT
;
Liu, JM
The photoconductivity and photorefractive characteristics of PMDA-DR19-based photoconducting nonlinear optical polymeric films with different compositions were studied using red and green lasers. Contributions of dopants and the host to the photoconductive and photorefractive properties are systematically discussed. The virgin nonlinear optical material PMDA-DR19 was neither photoconductive nor photorefractive in nature. However, it became photoconductive and photorefractive once the charge transport material was incorporated into the PMDA-DR19/PVB polymer film. Films containing more nonlinear optical chromophore exhibited higher diffraction efficiency. Response speed was further elevated when an additional charge generation material was doped in. Diffraction grating was observed under zero electric field and was confirmed due to a photorefractive effect by the two-beam coupling effect. In addition to composition modification, the laser light source was also an important factor in changing the PR response speed. The photorefractive response speed was tremendously improved when films were written and read by two different laser beams, either red/green lasers or green/red lasers. (C) 1997 Elsevier Science Ltd.
Two-dimensional elastodynamic transient analysis by QL time-domain BEM formulation
(1996-03-30)
Wang, CC
;
Wang, HC
;
Liou, GS
;
土木工程學系
;
Department of Civil Engineering
A quadratic time-domain Boundary Element Method (BEM) for two-dimensional (2-D) elastodynamic transient wave analysis is presented. Emphasis is focused on developing time-domain fundamental convoluted kernels and methodology for quadratic temporal solution procedure which are never presented before. In the presented BEM method, the displacement temporal variation is assumed to be quadratic, the traction temporal variation is assumed to be linear (called QL method, a two-time-step piecewise continuity method), and the spatial variations are assumed to be quadratic variation. The QL method is compared with the LC method and the QC method by solving several example problems. Numerical study reveals that the QC and QL methods are more accurate and stable than the LC method, and the QL method is much better than the QC method for transient problems.