Browsing by Author "Hsieh, CM"

Now showing 1 - 4 of 4

A turbulence model of wave-induced sheet flow
(2003-12-01)
Hsu, TW
;
Chang, HK
;
Hsieh, CM
;
土木工程學系
;
Department of Civil Engineering
This paper present a turbulence model that describes the sediment concentration and turbulent boundary layer of a wave-induced sheet flow. The simultaneous interactions between oscillatory, turbulent flow, and suspended sediment are included. The model specifies the equivalent roughness as a function of the Shields parameter, which is variable with time and is more physically realistic over a mobile flat bed. A wave friction factor, which differs from the conventional rough wall law, is obtained from the velocity gradient. A comparison of the turbulent boundary layer and sediment concentration for different equivalent roughness is given. The present model is shown to provide more accurate estimates than those using an equivalent roughness. Numerical results also show that the presence of suspended sediment retards mean velocity profile and decrease corresponding turbulence dynamic quantities.
Data broadcasting and seamless channel transition for highly demanded videos
(2001-05-01)
Tseng, YC
;
Yang, MH
;
Hsieh, CM
;
Liao, WH
;
Sheu, JP
One way to broadcast a popular video is to use a number of dedicated channels, each responsible for broadcasting some portion of the video periodically in a predefined way. The stress on channels can be alleviated, and new viewers do not have to wait long to start their playback, Many approaches falling in this category have been proposed, One such scheme that interests us is the fast broadcasting (FB) scheme, which can broadcast a video using k channels by incurring at most O(D/2(k)) waiting time on new-coming viewers, where D is the length of the video. In this paper, we consider a set of videos, each being broadcast by the FB scheme, Since the levels of demands on these videos may change by time, it is sometimes inevitable to change the numbers of channels assigned to some videos. We propose a novel seamless channel transition enhancement on top of the FB scheme to dynamically change the number of channels assigned to a video on-the-fly. Clients currently viewing this video will not experience any disruption because of the transition. A channel allocation scheme is also proposed based on the arrival rates of videos to minimize the average waiting experienced by all viewers, From the system manager's point of view, the enhancement will make the FB scheme more attractive.
Impact of air filter material on metal oxide semiconductor (MOS) device characteristics in HF vapor environment
(2004-05-15)
Hsiao, CW
;
Lou, JC
;
Yeh, CF
;
Hsieh, CM
;
Lin, SJ
Airborne molecular contamination (AMC) is becoming increasingly important as devices are scaled down to the nanometer generation. Optimum ultra low penetration air (ULPA) filter technology can eliminate AMC. In a cleanroom, however, the acid vapor generated from the cleaning process may degrade the ULPA filter, releasing AMC to the air and the surface of wafers, degrading the electrical characteristics of devices. This work proposes the new PTFE ULPA filter, which is resistant to acid vapor corrosion, to solve this problem. Experimental results demonstrate that the PTFE ULPA filter can effectively eliminate the AMC and provide a very clean cleanroom environment.
The removal of airborne molecular contamination in cleanroom using PTFE and chemical filters
(2004-05-01)
Yeh, CF
;
Hsiao, CW
;
Lin, SJ
;
Hsieh, CM
;
Kusumi, T
Cleanroom contamination and its impact on the performance of devices are beginning to be investigated due to the increasing sensitivity of the semiconductor manufacturing process to airborne molecular contamination (AMC). A clean bench was equipped with different filter modules and then most AMC in the cleanroom and in the clean bench was detected through air-sampling and wafer-sampling experiments. Additionally, the effect of AMC on device performance was examined by electrical characterization. A combination of the NEUROFINE PTFE filter and chemical filters was found to control metal, organic, and inorganic contamination. We believe that the new combination of filters can be used to improve the manufacturing environment of devices, which are being continuously shrunk to the nanometer scale.