Effects of inlet velocity profile on flow and heat transfer in the entrance region of a ribbed channel

Kim, D.H.,Lee, B.J.,Park, J.S.,Kwak, J.S.,Chung, J.T. Pergamon Press ; Elsevier Science Ltd 2016 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.92 No.-

Due to a complex channel structure, the coolant flow supplied to the internal cooling passage of a gas turbine blade shows an asymmetrical pattern rather than a fully developed or uniform distribution. In this study, the effect of the non-uniform inlet velocity profile of the coolant on the flow and heat transfer in a ribbed channel was investigated using the numerical analysis method. Four inlet velocity profiles were applied to a stationary ribbed channel and three Reynolds numbers of 10,000, 20,000 and 30,000 were considered. The hydraulic diameter of the channel was 24mm and the rib installation angle was 60<SUP>o</SUP>. The rib height-to-hydraulic-diameter ratio (e/D<SUB>h</SUB>) and the rib-pitch-to-height-ratio (P/e) were 0.125 and 10, respectively. Numerical analysis results showed that in the entrance region, the location and shape of the reattachment and the recirculation region were altered by the local velocity distribution caused by the different inlet velocity profiles. Therefore, the distribution and the strength of the vorticity in the channel were changed, and the local heat transfer coefficient and pressure drop in the channel were affected by the inlet velocity profile. The overall heat transfer coefficients for all cases showed similar values, however, the fully developed flow profile resulted in the highest thermal performance factor due to the lowest value of friction factor.

Analysis of Program Speed Characteristics Having Non-ideal Channel Profile in 3D NAND Flash Memory

Jaewoo Lee,Yungjun Kim,Yoocheol Shin,Seongjo Park,Hojong Kang,Daewoong Kang,Myounggon Kang 대한전자공학회 2024 Journal of semiconductor technology and science Vol.24 No.4

This study presents an in-depth investigation of the channel profile and program speed of non-ideal vertical 3-dimensional (3D) NAND Flash Memory. Using 3D technology computer-aided design (TCAD) simulations, the channel profiles were transformed into oxide-nitride-oxide (O/N/O) structures, providing insights into their impact on the device performance. Step-by-step programming was conducted for the initial state of each channel profile. Upon applying the programmed voltage, variations in the E-field of the tunneling oxide were observed based on the channel profile. Consequently, the concentration of the trapped electrons in the nitride, depending on the channel profile, was identified. Therefore, this study analyzed the influence of E-field differences due to channel profiles on the program speed and investigated vulnerable structures.

이동통신 채널의 PDP에 따른 OFDM 통신 시스템의 성능 분석

이종길 한국정보통신학회 2005 한국정보통신학회논문지 Vol.9 No.7

In this paper, various power delay profiles (PDP) are simulated to study the influence of the PDP shape on the bit error rate (BER) performance of Orthogonal Frequency Division Multiplexing (OFDM) communication systems. Assuming Rayleigh fading with 16-QAM modulation scheme, the simulation focuses on the investigation of the various shapes of the PDP which are often characterized by peaks, slope, attenuation and distance of an echo profile of waves. This yields information about the properties of the channel, and can be applied to decide the performance of the systems according to the channel. 본 논문에서는 OFDM 방식의 이동 통신 시스템의 성능분석을 위하여 다양한 PDP (Power Delay Profile) 형태에 따른 BER (Bit Error Rate) 의 변화 정도를 고찰하였다. 모의실험은 16-QAM 변조방식의 OFDM 통신 시스템 및 Rayleigh 채널을 가정하였다. 채널상태에 따라 매우 다양한 모습을 보이는 PDP의 peak 형태, 기울기, 감쇠정도, echo group 등에 따른 BER의 변화를 자세히 분석하였다. 또한 기존의 제한적인 실측 데이터 모델을 확장하여 새로운 모델을 적용함으로서 좀 더 완전한 성능평가가 이루어질 수 있도록 하였다. 실측 데이터에 근거한 여러 가지 채널모델을 기준으로 모의구현 모델의 파라메터 값들을 도출하여 다양한 전파환경에서의 성능을 분석하였다. 이러한 결과들은 OFDM 시스템에서의 채널상태 변화에 따른 BER 정도를 파악할 수 있는 기준을 제시하고 있으므로 향후 시스템의 설계 및 제작, 성능시험 등의 목적으로 폭넓게 활용될 수 있을 것이다.

이동통신 채널의 PDP에 따른 OFDM 통신 시스템의 성능 분석

이종길,Lee, Jong-Gil 한국정보통신학회 2005 한국정보통신학회논문지 Vol.9 No.6

본 논문에서는 OFDM 방식의 이동 통신 시스템의 성능분석을 위하여 다양한 PDP (Power Delay Profile) 형태에 따른 BER (Bit Error Rate) 의 변화 정도를 고찰하였다. 모의실험은 16-QAM 변조방식의 OFDM 통신시스템 및 Rayleigh 채널을 가정하였다. 채널상태에 따라 매우 다양한 모습을 보이는 PDP의 peak 형태, 기울기, 감쇠정도, echo group 등에 따른 BER의 변화를 자세히 분석하였다. 또한 기존의 제한적인 실측 데이터 모델을 확장하여 새로운 모델을 적용함으로서 좀 더 완전한 성능평가가 이루어질 수 있도록 하였다. 실측 데이터에 근거한 여러 가지 채널모델을 기준으로 모의구현 모델의 파라메터 값들을 도출하여 다양한 전파환경에서의 성능을 분석하였다. 이러한 결과들은 OFDM 시스템에서의 채널상태 변화에 따른 BER 정도를 파악할 수 있는 기준을 제시하고 있으므로 향후 시스템의 설계 및 제작, 성능시험 등의 목적으로 폭넓게 활용될 수 있을 것이다. In this paper, various power delay profiles (PDP) are simulated to study the influence of the PDP shape on the bit error rate (BER) performance of Orthogonal Frequency Division Multiplexing (OFDM) communication systems. Assuming Rayleigh fading with 16-QAM modulation scheme, the simulation focuses on the investigation of the various shapes of the PDP which are often characterized by peaks, slope, attenuation and distance of an echo profile of waves. This yields information about the properties of the channel, and can be applied to decide the performance of the systems according to the channel.

Analysis of Doping Profile Dependent Threshold Voltage for DGMOSFET Using Gaussian Function

Jung, Hak-Kee The Korea Institute of Information and Commucation 2011 Journal of information and communication convergen Vol.9 No.3

This paper has presented doping profile dependent threshold voltage for DGMOSFET using analytical transport model based on Gaussian function. Two dimensional analytical transport model has been derived from Poisson's equation for symmetrical Double Gate MOSFETs(DGMOSFETs). Threshold voltage roll-off is very important short channel effects(SCEs) for nano structures since it determines turn on/off of MOSFETs. Threshold voltage has to be constant with decrease of channel length, but it shows roll-off due to SCEs. This analytical transport model is used to obtain the dependence of threshold voltage on channel doping profile for DGMOSFET profiles. Also we have analyzed threshold voltage for structure of channel such as channel length and gate oxide thickness.

차분방법에 의한 OFDM 심볼 동기검출 방식

주창복,박남천,Joo Chang-Bok,Park Nam-Chun 대한전자공학회 2006 電子工學會論文誌-TC (Telecommunications) Vol.43 No.2

본 논문에서는 멀티패스 채널의 지연프로필이나 채널에 부가되는 잡음에 영향을 받지 않으면서 정확한 GI검출 성능을 보이는 간단한 구조의 수정차분방식의 동기검출 방식에 있어서 동기 검출점에서의 S/N비율과 동기점 검출성능과의 관계를 보여준다. 컴퓨터 시뮬레이션에서는 또 IEEE802.11a 표준의 OFDM 프레임을 사용하고 쇼트와 롱 트레이닝의 4심볼을 심볼 동기타이밍 검출에 사용한다. 수신 OFDM신호위상이 1심볼내에서 ${\pi}/2$이내로 일어나는 최소위상채널은 물론 ${\pi}$까지 회전하는 비최소위상 채널에서도 수정차분방식은 채널에 부가되는 잡음전력의 크기에 관계없이 OFDM신호의 1샘풀간격 이내의 오차로 타이밍을 검출해내는 성능을 보인다. In this paper, we introduce modified difference type symbol timing detection method of simple structure and show the relations between S/N ratio and timing detection performance which less influenced by multipath channel delay profile and added noise level and it show very exact GI detection performance characteristics. In the computer simulations, 4 symbol time duration of short and long training of IEEE802.11a standard OFDM frame are used for symbol synchronization timing detection. The computer simulation results show the very exact symbol timing detection performance characteristic within 1 sample error of OFDM signal regardless channel delay profile from minimn phase channels of phase rotation ${\pi}/2$ to non-minimum phase channels of phase rotation ${\pi}/2$ of received OFDM signal and added noise level in channel.

면광원 램프 및 이를 이용한 LCD TV용 백라이트

박종리,김청수,임성규,Park, Jong-Lee,Kim, Chung-Soo,Lim, Sung-Kyoo 한국마이크로전자및패키징학회 2007 마이크로전자 및 패키징학회지 Vol.14 No.2

LCD(Liquid Crystal Display) TV(Television) 용 백라이트의 광원으로서 면광원을 개발하였으며 이를 이용한 백라이트를 개발하였다. 백라이트의 광원으로 사용된 면광원은 유리성형을 통하여 채널을 형성하였으며 채널의 모양이 타원형 구조, 높이 4.4 mm, 채널의 실링 부위를 1.4 mm로 최적화된 면광원을 이용하여 제작한 백라이트의 성능을 향상시킬 수 있었다. 본 논문에서는 특히 면광원의 채널구조에 따른 백라이트의 휘도균일도의 변화에 대하여 연구하였으며 특히 광학 시뮬레이션을 통하여 면광원의 채널형상을 최적화 하였다. 채널의 구조가 최적화된 면광원을 이용하여 제작된 32", LCD TV의 휘도는 $576\;cd/m^2$ 이었다. A flat fluorescent lamp (FFL) was developed as a light source for LCD TV Backlight. The channels of FFL were realized by forming the flat glass at high temperature. The performance of the backlight with FFL was shown to improve by optimizing the FFL channel profile that has elliptical shape, 4.4 mm height and 1.4 mm sealing distance. In this paper, the brightness uniformity of LCD TV backlights was investigated by optical simulation of FFL channel profiles. The brightness of LCD TV using FFL with the optimized channel profile was shown to be $576\;cd/m^2$.

프로파일링 단계에서 파형 선별을 통한 템플릿 공격의 성능 향상

진성현(Sunghyun Jin),김태원(Taewon Kim),김희석(HeeSeok Kim),홍석희(Seokhie Hong) 한국정보보호학회 2017 정보보호학회논문지 Vol.27 No.1

템플릿 공격은 공격 대상 장비와 동일한 테스트 장비를 보유한 경우에 수행할 수 있는 강력한 부채널 분석 방법이다. 템플릿 공격은 테스트 장비를 이용하여 비밀정보에 대한 템플릿을 구성하는 프로파일링 단계와 공격 대상 장비에서 수집한 전력 파형을 템플릿과 비교하여 비밀정보를 찾는 매칭 단계로 구성된다. 템플릿 공격의 성능을 향상시키는 방법 중 하나는 가우시안 분포에 대한 템플릿의 추정을 향상시키는 것이다. 그러나 프로파일링 단계에서 각 중간값에 대한 템플릿을 계산할 때 사용되는 전력 파형의 수가 제한된다면 템플릿 계산이 부정확해진다. 본 논문에서는 프로파일링 단계에서 템플릿을 계산하기 위해 사용하는 파형의 수가 제한될 때 노이즈 파형으로 간주되는 전력 파형을 제거하는 방법론을 제시한다. 제시한 방법론에 따라 노이즈로 간주되는 전력 파형을 제외하여 템플릿을 구성할 경우에 템플릿 추정의 정확도가 향상되어 템플릿 공격의 성능이 향상된다. 또한 본 논문에서는 실험을 통해 템플릿 공격의 성능이 향상됨을 보임으로써 제시한 방법론이 타당함을 증명한다. Template attack is a powerful side-channel analysis technique which can be performed by an attacker who has a test device that is identical to target device. Template attack is consisted of building template in profiling phase and matching the target device using template that were calculated in profiling phase. One methods to improve the success rate of template attack is to better estimate template which is consisted sample mean and sample covariance matrix of gaussian distribution in template profiling. However restriction of power trace in profiling phase led to poor template estimation. In this paper, we propose new method to select noisy power trace in profiling phase. By eliminating noisy power trace in profiling phase, we can construct more advanced mean and covariance matrix which relates to better performance in template attack. We proved that the proposed method is valid through experiments.

Gene expression profile analysis in cultured human neuronal cells after static magnetic stimulation

임우석,이순태,김승찬 한국바이오칩학회 2012 BioChip Journal Vol.6 No.3

Although the magnetic force has been used in various human environments and medicines, their influence on the nervous system has not been fully elucidated. In this study, we investigated mRNA expressions profiles of neuronal cells after the application of static magnetic fields. Two perpetual magnets were applied to the cultured SH-SY5Y human neuronal cell, and the gene expression profiles were evaluated by using human mRNA microarray targeting 30968 genes. Results showed that the expressions of 827-known genes were altered in response to the magnetic force. Among them, 112 genes showed significant changes(>2-fold changes); 44 genes were up- regulated and 68 genes were down-regulated. Among the up-regulated genes, we further confirmed the increased expressions of synapsin III and chloride channel-2 by using RT-PCR and immunocytochemistry. These re-sults suggest that static magnetic fields influence neuronal-and biological related gene expression profiles in human neuronal cells.

비등간격 전극열에서의 입자 통과시간을 이용한 전기적 입자속도분포 검출기

김태윤(Taeyoon Kim),이동우(Dong Woo Lee),조영호(Young-Ho Cho) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.4

We present an electrical particle velocity profiler using particle transit time across uneven inter-gap electrodes. We measure both the particle position and velocity from the voltage signals generated by the particles passing across sensing electrodes, thus obtaining the velocity profile of the particles in a microfluidic channel. In the experimental study, we use polystyrene microparticles to characterize the performance of the electrical particle velocity profiler. The particle velocity profile is measured with the uncertainty of 5.44%, which is equivalent to the uncertainty of 5% in the previous optical method. We also experimentally demonstrate the capability of the present method for in-channel clogging detection. Compared to the previous optical methods, the present electrical particle velocity profiler offers the simpler structure, the cheaper cost, and the higher integrability to micro-biofluidic systems.