Showing papers by "National Taiwan University of Science and Technology published in 1995"
TL;DR: The crystalline structure and chemical composition of 3C-SiC films were found to depend on the SiH4/CH4 flow ratio as mentioned in this paper, and only polycrystalline SiC was obtained at a SiH 4/CH 4 flow ratio higher than 0.5.
Abstract: β‐SiC (3C–SiC) films were deposited on silicon substrates by electron cyclotron resonance chemical vapor deposition from SiH4/CH4/H2 mixtures at 500 °C. The crystalline structure and chemical composition of the deposited film were found to depend on the SiH4/CH4 flow ratio. With a sufficient energy supply from microwave power and a SiH4/CH4 flow ratio of 0.5 and lower, stoichiometric SiC could be deposited on Si substrates. Microcrystalline β‐SiC was grown at a SiH4/CH4 flow ratio of 0.5, whereas amorphous SiC was obtained at the SiH4/CH4 flow ratios lower than 0.5. When the SiH4/CH4 flow ratio was above 0.5, only polycrystalline Si could be deposited.
41 citations
Journal Article•
22 citations
TL;DR: In this article, the optical-absorption study of synthetic pyrite FeS2 single crystals prepared by the chemical-vaportransport method is reported over a temperature range from 4.2 to 300 K. At lower temperatures several features which occur below the absorption edge are superposed on the absorption curve.
Abstract: The optical‐absorption study of synthetic pyrite FeS2 single crystals prepared by the chemical‐vapor‐transport method is reported over a temperature range from 4.2 to 300 K. At lower temperatures several features which occur below the absorption edge are superposed on the absorption curve. The origin of the sharpest peak is identified as the transition between the top of valence band and Cr3+ trapping center through comparison of the results with that of the low‐temperature photoconductivity and the photoelectron paramagnetic resonance measurements. The nature of other weaker features is discussed. The existence of these features prevents the determination of the band gap of FeS2 by fitting the optical‐absorption data to the form of (αhν)∝(hν−E0)n. Therefore, the energy gap of FeS2 at low temperatures is estimated by adding the thermal ionization energy of the shallow acceptor states to the photoionization energy between the (SCl)2− states and the bottom of the conduction band. The band gap of various tem...
21 citations
TL;DR: In this paper, a videoenhanced plate method is developed to monitor the dynamic surface tension and contact angle simultaneously, where the profile of the air-water interface adjacent to a flat plate is captured by an image digitization technique.
Abstract: The assumption of zero contact angle of the Wilhelmy plate method causes error for the surface pressure‐area characteristics of some spread monolayers. To avoid this problem, a video‐enhanced plate method is developed to monitor the dynamic surface tension and contact angle simultaneously. According to this method, the profile of the air–water interface adjacent to a flat plate is captured by an image digitization technique. The surface tension and contact angle are obtained from the best fit between the edge coordinates of the captured image and a theoretical equation derived from the Young–Laplace equation. Preliminary results show satisfactory agreement between the curve of the air–water interface obtained from experimental data and the theoretical curve for obtained values of surface tension and contact angle. Twenty tests for pure water at 25 °C give an average surface tension 72.0±0.2 mN/m, which confirms the accuracy of this method. A preliminary dynamic test also indicates that the effect of the contact angle in the Wilhelmy method can be corrected by dividing the apparent surface tension obtained from the Wilhelmy method by the cosine of contact angle measured by the present method.
18 citations
Journal Article•
13 citations
TL;DR: When the correlation of parameters between the consecutive phases of snatch weight lifting was analyzed, it was demonstrated that the preactivation, normalized electromyographic values correlated negatively with GRFI while in the FP and SP, all of the parameters correlated positively with each other except lifting time.
Abstract: The biomechanical characteristics of 13 snatch lifts performed by 4 elite athletes were analyzed. Electromyographic data, ground reaction force index (GRFI), knee angular velocities, barbell velocities, and lifting time were obtained 0.2 s before the lift, for the first pulling phase (FP), and for the second pulling phase (SP). The preactivation, normalized electromyographic values correlated negatively with GRFI (p < .01). In the FP and SP, all of the parameters correlated positively with each other except lifting time. GRFI in the FP also correlated positively with GRFI, maximum knee angular velocities, and maximum barbell velocities of the SP (p < .01). In the SP, the ground reaction force reached its maximum first, followed by knee angular velocity and then barbell velocity. Barbell velocity reached its maximum before the knee and the hip joint were fully extended. When the correlation of parameters between the consecutive phases of snatch weight lifting was analyzed, it was demonstrated that the prea...
11 citations
14 Nov 1995
TL;DR: The experimental results show that the PAR model is capable of capturing the statistics of both the histogram and autocorrelation, and the proposed bandwidth allocation method is better than that of the fixed bandwidth allocation and is suitable for, the application of MPEG video services.
Abstract: We extend the autoregressive (AR) model to the projected AR (PAR) model for the purpose of fitting the histogram of VBR Motion Picture Expert Group (MPEG) and at the same time preserving the autocorrelation property. We also propose a bandwidth allocation scheme based on a prediction method where the frame sequence and the autocorrelation between consecutive frames are considered. Our experimental results show that the PAR model is capable of capturing the statistics of both the histogram and autocorrelation. The PAR model is then used as the traffic generator of a video source for an exhaustive simulation on the effectiveness of the proposed bandwidth allocation scheme. The proposed bandwidth allocation method, which predicts the bandwidth by the frame correlation (FC), demonstrates a quite good performance when comparing to a previous scheme, especially for the video scenes with the combination of intraframes and interframes. Bandwidth allocation of a multiplexer connected with several video sources is also studied and the results show that the proposed method is better than that of the fixed bandwidth allocation and is suitable for, the application of MPEG video services.
10 citations
TL;DR: In this article, an optical absorption study of synthetic RuS2−xSex single crystals is reported over a temperature range from 80 to 300 K. The data are fitted to several expressions for the shape of the absorption edge, with the best fit being to that expected for indirect allowed transitions.
Abstract: An optical‐absorption study of synthetic RuS2−xSex single crystals is reported over a temperature range from 80 to 300 K. The data are fitted to several expressions for the shape of the absorption edge, with the best fit being to that expected for indirect allowed transitions. The band gaps at any temperature varies smoothly with the Se composition x, indicating that the nature of the band edges are similar for RuS2, RuSe2, and the compounds of intermediate compositions. The indirect band gaps of various temperatures are determined and their temperature dependence are analyzed by the Varshni equation [Physica 34, 149 (1967)] and an empirical expression proposed by O’Donnell and Chen [Appl. Phys. Lett. 58, 2924 (1991)]. The parameters that describe the temperature dependence of energy gap of RuS2−xSex are evaluated and discussed.
4 citations
TL;DR: In this article, the optical absorption study of synthetic RuS2 single crystals grown in tellurium fluxes is reported over a temperature range from 4.2 K to 300 K. The data are fitted to several expressions for the shape of the absorption edge, with the best fit being to that expected for indirect allowed transitions.
Abstract: The optical absorption study of synthetic RuS2 single crystals grown in tellurium fluxes is reported over a temperature range from 4.2 K to 300 K. The data are fitted to several expressions for the shape of the absorption edge, with the best fit being to that expected for indirect allowed transitions. The indirect band gaps at various temperatures are determined. The temperature dependence is analysed by the Varshni equation and an empirical expression proposed by O'Donnell and Chen. The parameters that describe the temperature dependence of the energy gap of RuS2 are evaluated. At temperatures lower than 100 K, several features which occur below the absorption edge are superposed on the absorption curve. The origin of these features is discussed.
4 citations
TL;DR: The time complexities of the event and state matching modules are constant, which allows us to better control or predict the behavior of a real time task — a very important feature in a real‐time system.
Abstract: A real time Petri net (RTPN) model is proposed to model the task specification of a real time system in terms of events, actions, states, and temporal constraints. The basic operations of a RTPN include executable transition identification, marking updating, temporal constraint check, and shared input/output calculation. These are time‐consuming processes on whatever computers they are executed. A hardware‐implementable execution model is proposed to improve their performance. Detailed hardware designs of the event and state matching modules in the execution model are described. They employ an associative technique to provide massive parallelism needed in the modules. Moreover, the time complexities of the event and state matching modules are constant, which allows us to better control or predict the behavior of a real time task — a very important feature in a real‐time system.
3 citations
TL;DR: In this paper, a correlation between the HgTe lattice vibration TO mode and the electronic band structure of Hg1-x Znx Te alloys was found and the temperature dependence of electronic states for Hg 1 − Zn x Te can be explained well by a clustering effect in crystals.
Abstract: Infrared spectra, including transmission and reflection, have been used to characterize Hg1-x Znx Te crystals with various compositions x from cryostat temperature to room temperature. The energy band gap of the crystals were determined from the transmission spectra and their temperature dependence was observed. The reflection spectra of Hg1-x Znx Te crystals have been measured in the wave-number region of 60 to 450 cm-1. The frequencies of optical mode lattice vibrations are determined and their temperature dependence is discussed. A correlation between the HgTe lattice vibration TO mode and the electronic band structure of Hg1-x Znx Te alloys was found and the temperature dependence of electronic states for Hg1-x Znx Te can be explained well by a clustering effect in crystals.
TL;DR: In this paper, the temperature dependence of the energy band gap of the crystals was determined from the FT-IR experiments, and the relation between them can be fitted by an analytical expression: d(E g ) dT = (5.948 − 16.53x + 5.211x 2 ) × 10 −4 eV K −1.
TL;DR: In this paper, a correlation between the HgTe lattice vibration mode and the electronic structure of Hg1-xZnxTe alloys has been found, which indicates that there is a correlation that there are two TO phonon structures.
Abstract: The far-infrared reflection spectra of Hg1-xZnxTe crystals with various composition x have been measured at temperatures ranging from 90 to 295 K in the wavenumber region of 60 to 450 cm-1 In all but the pure compounds, HgTe and ZnTe, a two TO phonon structure is clearly observed The optical phonon frequencies are well determined by Kramers-Kronig integrations and dynamic dielectric function fitting As the temperature is increased, the lattice vibration frequencies of the ZnTe-like optical mode decreases in the composition range x