• Korea-Australia Rheology Journal
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• v.16 no.2
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• pp.63-73
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• 2004

Flow in a channel with an obstruction at the entry can be reverse, stagnant or forward depending on the position of the obstruction. These flow phenomena have potential applications in the control of energy and various flows in process engineering. Parameters that affect this flow inside and around the test channel are the gap (g) between the obstruction geometry and the test channel, the Reynolds number (Re) and the length (L) of the test channel. The influence of these parameters on the flow behavior was investigated using a flat plate obstruction at the entry of the channel. A low concentration polyacrylamide solution (0.018% by weight) showing a powerlaw fluid behavior was used as the fluid in this investigation. The flow phenomena were investigated by the velocity measurement and the flow visualization and their results were compared with numerical simulation. These results of low concentration polyacrylamide solution are also compared with the results of water published elsewhere (Kabir et al., 2003). The maximum reverse flow inside the test channel observed was 20% - 30% of the outside test channel velocity at a g/w (gap to width) ratio of 1 for Reynolds numbers of 1000 to 3500. The influence of the test channel length (L) and the Reynolds number (Re) on the velocity ratio ($V_i$/$V_o$: inside velocity/outside velocity in the test channel) are also presented and discussed here.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.9 s.339
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• pp.19-28
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• 2005

We establish a statistical model for the ultra-wide bandwidth (UMB) indoor channel based on over 2000 frequency response measurements campaign in a Practical apartment. The approach is based on the investigation of the statistical properties of the multipath profiles measured in different place with different rooms. Based on the experimental results, a characterization of the propagation channel from theoretic view point is described. Also we describe a method for measurement of the channel impulse response and channel transfer function. Using the measured data, the authors compares channel impulse responses obtained from time-domain and channel transfer functions obtained from frequency-domain with statistical path loss model. The bandwidth of the signal used in this experiment is from 10MHz to 8.01 GHz. The time-domain results such as maximum excess delay, men excess delay and ms delay spread are presented. As well as, omni-directional biconical antenna were used for transmitter and receiver In addition, measurements presented here support m channel model including the antenna characteristics.

• Journal of Digital Convergence
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• v.12 no.3
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• pp.249-254
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• 2014

Wireless LAN system is evolving toward high-speed data transmission and more accurate channel estimation is necessarily required to improve communication performance. The PLCP preamble field in IEEE 802.11 based wireless MODEM consists of ten short symbols and two long symbols and is used for synchronization and channel estimation. The existing least square (LS) channel estimation is based on only two long training symbols. After estimating channel response separately by using each long training symbol, the final channel estimation is obtained by the average of each estimation. In this paper, a new channel estimation algorithm is presented to improve the performance of the existing LS channel estimation algorithm. From the fact that the short training symbol consists of 12 non-zero subcarriers, it gives us a clue of being able to additionally estimate at least one fourth of channel coefficients. The new LS algorithm performs channel estimation based on both two long training symbols and a short training symbol. The proposed LS algorithm shows a little bit performance improvement over the existing LS estimation and it will be able to be applied to the IEEE 802.11p WAVE system.

• Journal of the Korea Safety Management & Science
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• v.19 no.2
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• pp.173-180
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• 2017

Omni-channel strategy is an innovative paradigm for integrated information distribution of inventory, sales, operations, marketing, delivery, pickups and returns in supply chain management. Recently the distribution strategy faces new challenges with the advent of mobile distribution channels. Social media with countless apps imposes additional stress on supply chain operations. Due to these changes, distribution network in supply chain is changing naturally and rapidly from multi-channel to omnni-channel platform. Recently numerous domestic distributors establish and adapt this new supply chain optimization tool as a part of seamless flow of movements of goods from one channel to other channels. The objective of this paper is to present a preliminary findings on how omnni-channel affects the supply chain management. A survey is used to ascertain in the degree of omnni-channel implementation and statistical evidence is provided to test sets of hypothesis. The results of the questionnaire showed that consumers' purchasing styles differed by gender, age, purchase purpose, and product type. In particular, women consider purchasing experience in omni-channel to be important. As food and household goods can be conveniently shipped, consumers prefer online purchasing it. Conversely, consumers tend to favor omni-channel strategy in connection with offline experience in IT products.

• Korean Management Science Review
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• v.26 no.1
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• pp.161-169
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• 2009

A traffic analysis on the Internet has an advantage for obtaining the characteristics of transferred packets. There were many studies to understand the characteristics of the Internet traffic with mathematical statistical approach. The approach of this study is different from previous studies. We first introduced a virtual network concept to present the Internet as a simplified mathematical model. It also represents each traffic flowing on the Internet as a parallel Gaussian channel on the virtual network. We suggest the optimal capacity of each parallel Gaussian channel using some related studies on the Gaussian channel model.

• Bulletin of Food Technology
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• v.18 no.2
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• pp.52-58
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• 2005

최근 20여년 동안 Panax ginseng의 다양한 효과가 연구 되어져 왔다. Panax ginseng의 주요 활성 성분인 ginsenosides는 오직 인삼에서만 발견되어지는 saponin이다. 최근 들어 신경, 非신경 또는 복합적으로 분포된 세포에서 ginsenoside가 $Ca^2+$, $K^+$,$Na^+$,$Cl^-$ channel이나 ligand gated ionchannel (5-HT3, nicotinic acetylcholine, NMDA receptor)과 같은 다양한 ion channel을 조절하는증거들이 발표되고 있다. Ginsenoside는 voltage-dependent $Ca^2+$, $K^+$,$Na^+$ channel의 활성을 억제하는 반면 $Ca^2+$-activated $Cl^-$ channel이나 $Ca^2+$-activated $K^+$ channel의 활성은 증가 시키는 것으로 나타났다. 또한 흥분성 ligand-gated ion channel인 $5-HT_3$, nicotinic acetylcholine, NMDA receptor의 활성은 억제한다. 본 총설에서는 현재까지 알려진 ion channel 활성에 대한 ginsenoside의 조절작용과 이것으로 인해 어떻게 생물학적 효능과 연결이 되어있는지에 대하여 이야기하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.438-444
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• 1993

The circuit board of an electronic equipment were simulated with a vertical channel which had thermal blocks protruded from one of the channel walls. A rought front plate was made of a circuit board attached with short wires to simulate the back side of a printed circuit board. Natural convection experiments were carried out to study the effects of channel space and rough front plate and to find the suitable characteristic value after the fourth row. The effect of a rough front plate was negligble. There were negligible effects of the channel space on the first and second heaters. Heat transfer coefficients after the third row decreased as the channel space decreased. Heat transfer coefficients were almost constant for larger than 20 mm channel space. A characteristic length was suggested to non-dimensionalize Nu and Ra numbers in a vertical channel with protruded heaters. A correlation was obtained using the new characteristic lengths.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.8
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• pp.126-132
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• 1995

The electrical stress of short channel polycrystalline silicon (poly-Si) thin film transistor (TFT) has been investigated. The device characteristics of short channel poly-Si TFT with 5$\mu$m channel length has been observed to be significantly degraded such as a large shift in threshold voltage and asymmetric phenomena after the electrical stress. The dominant degradation mechanism in long channel poly-Si TFT's with 10$\mu$m and 20$\mu$m channel length respectively is charage trappling in gate oxide while that in short channel device with 5.mu.m channel length is defect creation in active poly-Si layer. We propose that the increased defect density within depletion region near drain junction due to high electric field which could be evidenced by kink effect, constitutes the important reason for this significant degradation in short channel poly-Si TFT. The proposed model is verified by comparing the amounts of the defect creation and the charge trapping from the strechout voltage.

• Journal of the Korean Operations Research and Management Science Society
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• v.25 no.1
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• pp.85-92
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• 2000

Channel management is critical in designing a cellular mobile system that offers high capacity and high quality. In this paper, an integrated channel management scheme is proposed, which consists of a dynamic channel allocation scheme and an admission control scheme. The dynamic channel allocation scheme allocates a call request the channel which minimizes the impact on its interfering cell, and consists of two types of channel allocation strategies : nominal channel allocation strategy and non-nominal channel allocation strategy. The admission control scheme named the variable cutoff priority scheme reserves some frequency channels for handoff cells in each cell the number of which varies according to the blocking probability of handoff class in that cell. Computationl tests are performed to evaluate the performance of the proposed scheme in terms of overall blocking probability, defined by the weighted value of the blocking probabilities of new calls and handoff calls. The results show that the proposed scheme yields better performance than other compared schemes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.113-114
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• 2007

Hole mobility characteristics of single surface channel and dual channel Si/SiGe structure are compared, where the former one consists of a relaxed SiGe buffer layer and a tensile strained Si layer on top, and for dual channel structure a compressively strained SiGe layer is inserted between them. Due to the difference of hole mobility enhancement factors of layers between them, hole mobility characteristics with respect to the Si cap thickness shows the opposite tend. Hole mobility increases with thicker Si cap for single channel structure, whereas it decreases with thicker Si cap for dual channel structure.