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박순식,최지웅,윤관섭,나정열 한양대학교 이학기술연구소 2002 이학기술연구지 Vol.5 No.-
During the last several decades, although there have been lots of efforts to develope the high-frequency bottom reflection loss model, the frequency dependence of bottom loss was not considered in most cases because the sea bottom was assumed to be generally much smoother and lower gradient than the sea surface. However, if the sea bottom is rougher than acoustic wavelength, the scattered field will be increased and the reflected field will be decreased. In this paper, the high-frequency bottom reflection losses were obtained through the measurement of reflected waves from the artificially-made-flat sandy bottom. The experimental data were compared with the values calculated by the forward loss model of Mourad & Jackson. Conseouently, we suggest the frequency dependence of bottom reflection loss. 기존 해저면 반사손실 모델들은 해저면을 해수면에 비해 거칠기와 경사도가 매우 평탄하거나 완만한 경계면으로 가정하므로 주파수에 따른변화를 고려하지 않거나 미약하다고 가정하였다. 그러나 고주파를 사용하는 소오나 시스템의 경우, 음파의 파장에 비해 해저면이 거칠다면 음파는 산란 영향이 증가하게 되므로 상대적으로 반사손실 또한 증가하게 된다. 따라서 본 논문에서는 임의로 모의된 사질 성분의 해저면에서 수십 ㎑ 이상의 고주파들을 사용하여 주파수별 반사손실을 계산하고, 이를 기존의 해저면 반사손실 모델과 비교하였으며, 해저면 반사손실의 주파수 종속성을 제시하고자 한다.
Popliteal Fossa Pain in 24 Year-old Female
( Kwan Woong Choi ),( Kyung Bong Yoon ),( Duck Mi Yoon ),( Do Hyeong Kim ) 대한통증학회 2012 The Korean Journal of Pain Vol.25 No.4
The pain around the posterior knee, called ``popliteal fossa``, has been known to be caused by a variety of disease entities. Venous malformation is a very rare cause of popliteal area pain, and its diagnosis is frequently delayed, missed, or given incorrectly. Here, we report a case of a patient with popliteal fossa pain for 2 years and was diagnosed as intramuscular venous malformation using ultrasound.
Popliteal Fossa Pain in 24 Year-old Female
Choi, Kwan-Woong,Yoon, Kyung-Bong,Yoon, Duck-Mi,Kim, Do-Hyeong The Korean Pain Society 2012 The Korean Journal of Pain Vol.25 No.4
The pain around the posterior knee, called 'popliteal fossa', has been known to be caused by a variety of disease entities. Venous malformation is a very rare cause of popliteal area pain, and its diagnosis is frequently delayed, missed, or given incorrectly. Here, we report a case of a patient with popliteal fossa pain for 2 years and was diagnosed as intramuscular venous malformation using ultrasound.
Thermoelectric Properties of Manganese Monosilicide Synthesized by Mechanical Alloying Process
Choi, Moon Kwan,Lee, Woong Jae,Kim, Il Ho,Lee, Young Geun,Kweon, Soon Yong,Yoon, Man Soon,Ur, Soon Chul Trans Tech Publications, Ltd. 2012 Materials science forum Vol.724 No.-
<P>Manganese silicide is one of the potential thermoelectric materials for high temperature application. As a fundamental investigation on these materials group, manganese monosilicides were synthesized by the mechanical alloying of stoichiometric elemental powder compositions, and the as-milled powders were consolidate by vacuum hot pressing. Phase transformation and microstructure evolution during mechanical alloying and hot consolidation were investigated using XRD and SEM. Near single phase of monosilicides were successfully produced in this process. Thermoelectric properties as a function of temperature were evaluated in terms of Seebeek coefficient, electrical resistivity, thermal conductivity and the figure of merit for the hot pressed specimens. Mechanically alloyed manganese monosilicide, MnSi, appeared to have a potential as a thermoelectric material in this study.</P>
Choi, Jong-Soon,Kim, Il-Woong,Hwang, Seock-Yeon,Shin, Bong-Jeong,Kim, Si-Kwan BLACKWELL SCIENCE 2008 BJU INTERNATIONAL Vol.101 No.2
<P>OBJECTIVES</P><P>To determine the detrimental role of tetrachlorodibenzo-<I>p</I>-dioxin (TCDD) in testicular histology, spermatogenesis-related panels and proteome, and serum sex hormone levels.</P><P>MATERIALS AND METHODS</P><P>In all, 40 male rats were divided into equal groups: a normal control (NC) group that received vehicle and saline, and a TCDD-treated (TT) group injected intraperitoneally with TCDD (one dose, 50 µg/kg body weight). The rats were killed 4 weeks after TCDD exposure and testicular weight, histopathology, proteome and variables related to spermatogenesis, and serum sex hormone levels were investigated.</P><P>RESULTS</P><P>TCDD induced a significant decrease in testicular weight, Johnsen’s score, seminiferous tubular size, percentage of tubules containing sperm, sperm counts, germ cell counts and Sertoli cell index. In addition, there was a significant decrease in serum testosterone level (<I>P</I> < 0.01) and a remarkable increase in oestradiol (<I>P</I> < 0.01), follicle-stimulating hormone (<I>P</I> < 0.05) and luteinizing hormone (<I>P</I> < 0.05) levels in the TT group. The expression of six testicular proteins including testis-specific heat shock protein (Hsp70), protein disulphide isomerase A3 precursor, 3-phosphoglycerate dehydrogenase, nonmuscle myosin heavy-chain type B-like protein, and superoxide dismutase 1 were significantly up-regulated (<I>P</I> < 0.05–0.01). Interestingly, fertility protein SP22 and phosphatidylethanolamine-binding protein were down-regulated but this was only significant for fertility protein SP22 (<I>P</I> < 0.05).</P><P>CONCLUSION</P><P>TCDD induces marked histological changes in the testis, impairs variables related to spermatogenesis, and increases serum oestradiol levels but decreases testosterone levels. In particular, TCDD disturbs testicular proteome profiles in rats.</P>