• 대한기계학회논문집B
• /
• 제30권1호
• /
• pp.24-31
• /
• 2006

Mixing vanes have been installed in the space grid of nuclear fuel rod bundle to improve turbulent heat transfer. Split mixing vanes induce the vortex flow in the cooling water to swirl in sub-channel of fuel assembly. But, The swirling flow decays rapidly so that the heat transfer enhancing effect limited to short length after the mixing vane. In thi present study, the large scale vortex flow(LSVF) is generated by rearranging the mixing vanes to the coordinated directions. This LSVF mixing vanes generate the most strong secondary flow vortices which maintain about 35 $D_H$ after the spacer grid. The streamwise vorticity generated by LSVF sustain two times more than that split mixing vane. Heat transfer in the rod bundle occurs greatly at the same direction to cross flow, and maximum temperature at the surface of bundle drops about 1.5K

• Journal of the Optical Society of Korea
• /
• 제12권3호
• /
• pp.136-146
• /
• 2008

We proposed an adaptive steganography of an optical image using bit-planes and multichannel characteristics. The experiment's purpose was to compare the most popular methods used in optical steganography and to examine their advantages and disadvantages. In this paper we describe two digital methods: the first uses less significant bits(LSB) to encode hidden data, and in the other all blocks of $n{\times}n$ pixels are coded by using DCT(Digital Cosine Transformation), and two optical methods: double phase encoding and digital hologram watermarking with double binary phase encoding by using IFTA(Iterative Fourier Transform Algorithm) with phase quantization. Therefore, we investigated the complexity on bit plane and data, similarity insert information into bit planes. As a result, the proposed method increased the insertion capacity and improved the optical image quality as compared to fixing threshold and variable length method.

• 전기학회논문지
• /
• 제56권11호
• /
• pp.2033-2035
• /
• 2007

This paper proposes a novel iterative LMS-based decision feedback equalizer for short burst transmission with relatively short training sequence. In the proposed equalizer, the longer concatenated training sequence can provide the more sufficient channel information and the reused original training sequence can provide the correct decision feedback information. In addition, the overall adaptive processing is performed using the low complexity LMS algorithm. The study shows the performance of the proposed method is enhanced with the number of iterations and, furthermore, better than that of the conventional LMS-based DFEs with the training sequence of longer or equal length. Computational complexity is increased linearly with the number of iterations.

• Water Engineering Research
• /
• 제3권4호
• /
• pp.247-258
• /
• 2002

This paper presents a non-isotropic turbulence modeling of flows over bedforms. The Reynolds stress model is used for the turbulence closure. In the model, Launder, Reece, and Rodi's model and Hanjalic and Launder's model are employed f3r the pressure strain correlation term and the diffusion term, respectively. The mean flow and turbulence structures are simulated and compared with profiles measured in the experiments. The numerical solutions from two-equation turbulence models are also provided for comparisons. The Reynolds stress model yields the separation length of eddy similar to the other numerical results. Using the developed model, the resistance coefficients are also estimated for the flows at different Froude numbers. Karim's (1999) relationship is used to determine the bedform geometry. It is found that the values of the form drag and the skin friction are very similar to those obtained by the other turbulence models. meaning higher values of the form drag and lower values of the skin friction compared with the empirical formulas.

• 한국통신학회논문지
• /
• 제30권7A호
• /
• pp.542-549
• /
• 2005

In this paper, the optimal pump light power of optical phase conjugator (OPC) and the compensation characteristics of distorted WDM channel signals are numerically investigated, when the OPC with highly-nonlinear dispersion shifted fiber (HNL-DSF) not be placed at the mid-way of total transmission length. The total dispersion of former half section and latter half section is assumed to be same each other in this approach. It is confirmed that, in WDM transmission systems with OPC deviated from the mid-way, the pump light power for best compensation must be flexible selected depending on the OPC position. This optimal pump light power is gradually increased as the OPC is gradually closer to the receiver. Consequently, it is possible to establish the compensation system independent on the OPC position by setting optimal pump light power connected with the OPC position.

• Transactions on Electrical and Electronic Materials
• /
• 제11권6호
• /
• pp.253-256
• /
• 2010

Different active layer thicknesses for zinc oxide (ZnO) bottom-contact thin-film transistors (TFTs) were fabricated with a poly-4-vinyphenol polymeric dielectric using injector type atomic layer deposition. The properties of the ZnO TFTs were influenced by the active thickness and width-to-length (W/L) ratio of the device. The threshold voltage of ZnO TFTs shifted positively as the active layer thickness decreased, while the subthreshold slope decreased. The W/L ratio of ZnO TFTs also affected the mobility and subthreshold slope. An optimized TFT structure exhibited an on-tooff current ratio of above 106 with solid saturation.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2000년도 하계학술대회 논문집 C
• /
• pp.1754-1756
• /
• 2000

Organic semiconductors based on fused-ring polycyclic aromatic hydrocarbon have great potential to be utilized as an active layer for electronic and optoelectronic devices. In this study, pentacene thin films and electrode materials were deposited by Organic Molecular Beam Deposition(OMBD) and vacuum evaporation respectively. For the gate dielectric, polyamic acid was spin-coated and cured into polyimide at 350$^{\circ}C$. Electrical characteristics of the devices were investigated, where the channel length and width was 50${\mu}m$ and 5mm. It was found that field effect mobility was 0.012$cm^{2}/Vs$, and on/off current ratio was $10^5$.

• 한국산학기술학회논문지
• /
• 제15권5호
• /
• pp.2655-2661
• /
• 2014

본 연구는 치유예술로서의 춤이 여성노인의 뇌기능에 어떤 영향을 미치는 지, 2channel system EEG를 통해 검증하였다. 연구 대상은 K시 소재 65세이상 여성노인 60명, 연구기간은 2013년 3월에서 2013년 7월까지, 주 1회, 회기 당 60분씩, 총 16주 동안 프로그램을 실시하였다. 참여대상 30명은 실험집단, 30명은 통제집단으로 구성하여 프로그램 실시전후에 뇌파를 측정하였다. 연구 결과는, 실험집단에서 기초율동지수 좌뇌 사후(79.11/89.56, p<.015), 주파수우뇌 사후 평균값(8.33/9.37, p<.003), 진폭좌뇌 사후 평균값(39.87/47.19, p<.006), 진폭우뇌 사후(40.09/49.87, p<.000)의 상승을 보였다. 따라서 치유예술로서의 춤이 여성노인의 기초율동지수, 주파수와 진폭을 상승시켜 뇌기능 향상 프로그램으로서의 효용과 가치를 검증하였다.

• 한국유통학회지:유통연구
• /
• 제1권2호
• /
• pp.173-198
• /
• 1996

Distribution of farm produce in Korea is known to be inefficient due to the numerous stages that exist in the distribution channel. This has resulted in dissatisfaction for both farmer and consuers; farmers sell their produce at low prices to middlemen while consumers pay high prices for them because of price increases that occur in the distribution chain. We apply Spengler's theory of double marginalization to show that price increases are inevitable as the length of the farm distribution chain increases. We then show that the negative effects of double marginalization can be contained by setting up a physical distribution center. The physical distribution center effectively reduces the stages in the distribution from 5 or 6 stages to 3 or 4 stages. We also lay out the design and major characteristics of the distribution center, as well as the expected cost savings.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2009년도 춘계학술대회 논문집
• /
• pp.263-265
• /
• 2009

In this study, ultrafine grained (UFG) oxygen free high conductivity copper (OFHC Cu) having two different grain morphologies, one the severely elongated and the other the equiaxed, was prepared by equal channel angular pressing (ECAP) with routes A and $B_c$, respectively. The results of quasi-static tensile tests at $10^{-1}\;s^{-1}$ and $1\;s^{-1}$ and dynamic compression tests at $10^3\;s^{-1}$ order revealed that the equiaxed UFG Cu exhibited higher strength and less ductility compared to the elongated one. The difference of the plastic flow characteristics between the two were rationalized by considering their dislocation mean free length based on the orientation relationship between the possible slip planes and the loading direction.