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Intracavity measurement of liquid crystal layer thickness by wavelength tuning of an external cavity laser diode
Get PDF[[abstract]]The gap of a planar-aligned liquid crystal (LC) cell is measured by a novel method: Monitoring the change in output wavelength of an external-cavity diode laser by varying the voltage driving the LC cell placed in the laser cavity. This method is particularly suitable for measurement of LC cells of small phase retardation. Measurement errors of +/- 0.5 % and +/- 0.6 % for 9.6-mu m and 4.25-mu m cells with phase retardations of 1.63 mu m and 0.20 mu m respectively are demonstrated.[[fileno]]2010144010126[[department]]物理
Dependence of terahertz radiation on gap sizes of biased multi-energy arsenic-ion-implanted and semi-insulating GaAs antennas
Get PDF[[abstract]]We investigate the characteristics of terahertz radiation pulses using biased multi-energy arsenic-ion-implanted and semi-insulating GaAs photoconductive antennas with different gap sizes in terahertz time-domain spectroscopy. At a specific fluence excitation, with increasing antenna gap size, the absolute values of the (peak) normalized terahertz waveform minimum (valley), as well as the bandwidth, reveal an increasing trend for multi-energy arsenic-ion-implanted GaAs antennas and a decreasing trend for semi-insulating GaAs antennas. We find that the largest reachable bias fields applied to arsenic-ion-implanted GaAs antennas are higher than those applied to semi-insulating GaAs antennas. On the basis of pump fluence dependences of peak terahertz amplitude, we deduce that multi-energy arsenic-ion-implanted GaAs antennas have the ability to acquire higher THz power at even higher pump fluence in comparison with semi-insulating GaAs antennas.[[fileno]]2010144010174[[department]]物理
Optical properties and potential applications of ε-GaSe crystal at terahertz frequencies
No full text[[abstract]]Ordinary and extraordinary refractive indices of an epsilon-GaSe crystal at terahertz (THz) frequencies are experimentally determined in this study. Fitting experimental data by THz time-domain spectroscopy (THz-TDS) and a Fourier transform infrared spectrometer (FTIR), we proposed revised complex dielectric functions and Sellmeier equations of GaSe for both ordinary and extraordinary waves from 0.2 to 100 THz. Phonon vibrational modes and overtones in the THz frequency range are examined in detail. The high magnitude of the figure of merit (FOM similar to 10(3) at 1 THz), the large birefringence (Delta n similar to 0.76 at 1 THz). and the low absorption coefficient (alpha similar to 0.2 cm(-1) at 1 THz) of GaSe are also identified. Potential applications to practical photonic devices such as phase shifters at THz frequencies are proposed.[[fileno]]2010144010178[[department]]物理
A terahertz plastic wire based evanescent field sensor for high sensitivity liquid detection
Get PDF[[abstract]]A highly sensitive detection method based on the evanescent wave of a terahertz subwavelength plastic wire was demonstrated for liquid sensing. Terahertz power spreading outside the wire core makes the waveguide dispersion sensitive to the cladding index variation, resulting in a considerable deviation of waveguide dispersion. Two liquids with transparent appearances, water and alcohol, are easily distinguished based on the waveguide dispersion, which is consistent with theoretical predictions. A melamine alcohol solution with various concentrations is identified successfully, and the detection limit is up to 20ppm, i.e. equivalent to the index variation on the order of 0.01.[[fileno]]2010144010183[[department]]物理
The Complex Refractive Indices of the Liquid Crystal Mixture E7 in the THz Frequency Range
No full text[[abstract]]We have used terahertz time-domain spectroscopy to investigate the complex optical constants and birefringence of a widely used liquid crystal mixture E7 in both nematic and isotropic phases (26 degrees C-70 degrees C). The extinction coefficient of E7 at room temperature is less than 0.035 and without sharp absorption features in the frequency range of 0.2-2.0 THz. The extraordinary (n(e)) and ordinary (n(o)) indices of refraction at 26 C are 1.690-1.704 and 1.557-1.581, respectively, giving rise to a birefringence of 0.130-0.148 in this frequency range. The temperature-dependent (26 degrees C-70 degrees C) order parameter extracted from the birefringence data agrees with that in the visible region quite well. Further, the temperature gradients of the terahertz optical constants of E7 are also determined. The optical constants of E7 in the terahertz or sub-millimeter wave range are found to deviate significantly from values predicated by the usual extended Cauchy equations used in the visible and near-infrared.[[fileno]]2010144010191[[department]]物理
A History-based Cost-Cognizant Test Case Prioritization Technique in Regression Testing
No full text[[abstract]]Software testing is typically used to verify whether the developed software product meets its requirements. From the result of software testing, developers can make an assessment about the quality or the acceptability of developed software. It is noted that during testing, the test case is a pair of input and expected output, and a number of test cases will be executed either sequentially or randomly. The techniques of test case prioritization usually schedule test cases for regression testing in an order that attempts to increase the effectiveness. However, the cost of test cases and the severity of faults are usually varied. In this paper, we propose a method of cost-cognizant test case prioritization based on the use of historical records. We gather the historical records from the latest regression testing and then propose a genetic algorithm to determine the most effective order. Some controlled experiments are performed to evaluate the effectiveness of our proposed method. Evaluation results indicate that our proposed method has improved the fault detection effectiveness. It can also been found that prioritizing test cases based on their historical information can provide high test effectiveness during testing.[[fileno]]2030240010039[[department]]資訊工程學
A Study on the Applicability of Modified Genetic Algorithms for the Parameter Estimation of Software Reliability Modeling
No full text[[abstract]]In order to assure software quality and assess software reliability, many software reliability growth models (SRGMs) have been proposed for estimation of reliability growth of products in the past three decades. In principle, two widely used methods for the parameter estimation of SRGMs are the maximum likelihood estimation (MLE) and the least squares estimation (LSE). However, the approach of these two estimations may impose some restrictions on SRGMs, such as the existence of derivatives from formulated models or the needs for complex calculation. Thus in this paper, we propose a modified genetic algorithm (MGA) to estimate the parameters of SRGMs. Experiments based on real software failure data are performed, and the results show that the proposed genetic algorithm is more effective and faster than traditional genetic algorithms.[[fileno]]2030240030082[[department]]資訊工程學
國立清華大學簡訊第854期
Get PDF[[abstract]]‧ 賀 工業工程與工程管理學系陳彥綾(指導教授：工業工程與工程管理學系吳建瑋教授)、化學工程學系曲華德(指導教授：化學工程學系陳信文教授)、生醫工程與環 境科學系劉芯彤(指導教授：孫毓璋教授)獲大專學生研究計畫研究創作獎
‧ 賀 中文系博士生李柏翰獲科技部獎勵人文與社會科學領域博士候選人撰寫博士論文
‧ 賀 生醫工程與環境科學系鍾年凱同學榮獲全國中胡獨奏冠軍
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‧ 演講資訊─大數據與圖書館應用[[fileno]]JA02_2014_85
國中歷史作業「我在歐洲的日子」教學設計與實施
No full text[[abstract]]可否設計培養與發展學科能力，特別是歷史思維能力的作業課題？設計以學生學習為中心，增加學生在教學過程餐與的歷史作業，是否有利於思維能力的培養及提升？這樣的歷史作業，學生必須改變學習的方式，學生的反應如何？本文記錄一個國中歷史課後作業，「探索過去，模擬角色：『我在歐洲的日子』」，從想法、設計到實施、成果的點滴與體驗，期與同行們共勉。[[fileno]]204_JA04_2006_n17_p