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Two-phase pressure drop due to friction in micro-channel
Lim, Tae-Woo,You, Sam-Sang,Kim, Jong-Su,Moon, Serng-Bae,Seo, Dong-Hoan SAGE Publications 2014 Proceedings of the Institution of Mechanical Engin Vol.228 No.5
<P>This paper deals with an experimental investigation to measure the frictional pressure drops for two-phase flow boiling in a micro-channel with a hydraulic diameter of 500 µm. First, the experimental study is performed under the test conditions: heat fluxes ranging from 100 to 400 kW/m<SUP>2</SUP>, vapor qualities from 0 to 0.2, and mass fluxes of 200, 400 and 600 kg/m<SUP>2</SUP>s. Then, the frictional pressure drop during flow boiling is estimated using two models: the homogeneous model and the separated flow model. The experimental results show that the two-phase multiplier decreases with the increase of mass flux. In addition, the measured pressure drops are compared with those from a few correlation models available for macro-scales and mini/micro-scales. Finally, the present paper proposes a new correlation for two-phase frictional pressure drops in mini/micro-scales. This correlation model is developed based on the Chisholm constant C as a function of two-phase Reynolds and Weber numbers. It is found that the new correlation satisfactorily predicts the experimental data within mean absolute error (MAE) of 3.9%.</P>
홈 네트워크를 위한 Embedded Ethernet Module 설계 및 구현
김판규,황태문,이종혁,Kim Pan-kyu,Hoan Tae-Moon,Lee Jong-hyeok 한국정보통신학회 2005 한국정보통신학회논문지 Vol.9 No.5
초고속 인터넷의 보급, 디지털 정보장비의 확산 및 생활 패턴의 변화에 따라 홈 네트워크의 필요성이 점차 확대되고 있다. 이에 따라 본 연구에서는 홈 네트워크화를 위해서 8051 MCU, Hardware TCP/IP를 이용하여 임베디드 이더넷 모듈을 설계, 개발하였다. 타겟 머신에 간단한 웹 서버를 구축하고 이를 이용한 원격제어 프로그램을 포팅하여 원격지에서도 인터넷으로 가전기기를 제어할 수 있도록 하였다. 본 연구에서 개발한 모듈을 이용하므로 저가격으로 홈 오토메이션을 구현할 수 있으리라 생각한다. The necessity of the home network have been enlarged gradually according to the distribution of ultra-high speed internet, the expansion of a digital information equipment and the change of a life pattern. In this paper, we proposed the embedded ethernet module that could be operate on eight bit system, but it could control home appliance with full ethernet speed. The embedded ethernet module consists of 8051 MCU and Hardware TCP/IP. In this module, we construct simple web server and port remote control program for I/O device control. We verified through internet that the developed embedded ethernet module could control and check home appliances anywhere and anytime. We expect the developed ethernet module can build up niche market at home network. And it will be helpful to activate home network market.
정석희 ( Seuk Hee Chung ),문승환 ( Seung Hwan Moon ),백정환 ( Jeung Hoan Paik ),김경태 ( Kyoung Tae Kim ),최세웅 ( Se Woong Choi ),이창재 ( Chang Jae Lee ),조용락 ( Young Rak Cho ),나서희 ( Seo Heui Ra ),안원석 ( Won Suk An ),김 대한내과학회 2006 대한내과학회지 Vol.70 No.6
Background: The manifestation of Membranoproliperative glomerulonephritis (MPGN) is variable from asymptomatic hematuria, nephrotic syndrome to advanced chronic kidney disease. The etiology, pathogenesis, and treatment of MPGN are unclear. The incidence of idiopathic MPGN is also rare in Korea, and the clinical course was rarely studied. So we investigated clinical course of idiopathic MPGN type 1. Methods: From March 1990 to November 2004, renal biopsy was done in about 1500 patients in Dong-A universty hospital. Among them, 16 patients were diagnosed as idiopathic MPGN. Fourteen patients were observed over 6 months. We analyzed clinical data of these patients retrospectively. Results: Male to female ratio of total 16 patients is 2.2:1. Mean age of patients was 37.6 years (14-76years) at the time of diagnosis. Thirteen cases (81%) had nephrotic range proteinuria, 8 cases (50%) had hypertention, 12 cases (75%) had edema, and 4 cases (25%) had decreased renal fuction (serum creatinine>1.2 mg/dL) at the time of diagnosis. Average observation time was 55.7±37.4 (6-122)months. Six cases ended up with progressive renal failure. Three cases achieved complete remission. Renal survival time for 50% of cases was 92 months. In our study, edema and decreased renal fucntion at the time of diagnosis were related with later development of progressive renal failure (p<0.05). Of the total 14 cases, 4 cases ware treated conservatively, 6 cases were treated with anti-platelet agents, and 4 cases were treated with anti-platelet agents and prednisone. In conservative treatment group, 1 case ended up with progressive renal failure and 1 case achieved complete remission. In anti-platelet agents treatment goup, 4 cases ended up progressive renal failure. In combined anti-platelet agents and prednisone treatment group, 1 case ended up progressive renal failure and 2 cases achieved complete remission. However, the effect of each treatment is inconclusive because the number of the patients are too small. Conclusions: We suspect that deceased renal function and edema at the time of diagnosis may be risk factor predicting progressive renal failure in patients with idiopathic MPGN type 1.(Korean J Med 70:663-671, 2006)
김수민,오은영,한승경,문태기,유정환,전우택 대한피부과학회 1998 大韓皮膚科學會誌 Vol.36 No.6
Background : Vitiligo is an acquired disorder which causes body disfiguring and may provoke emotional stress, functional impairment, and psychiatric symptoms. Objective : (1) To assess whether the psychiatric symptoms are more frequent in vitiligo patients than control patients. (2) To investigate whether the vitiligo patients with more severe psychiatric symptoms use more negative and passive coping mechanisms than patients with less severe psychiatric symptoms. To carry out this study we evaluated psychiatric symptoms, problems in daily activities, and the relation-ship between coping mechanisms and psychiatric symptoms. Methods : A clinical study was done on 150 vitiligo patients. Other dermatology patients were used as a control group. Both groups had visited the dermatology clinic of the Severance hospital. Questionaires regarding age, sex, severity of disease, duration of disease, SCL-90(symptom check list 90), the coping list of Weisman, and items for adaptability of daily activity were recorded. Results: Male vitiligo patients showed more psychological symptoms than female patients. Vitiligo patients had many more difficulties in daily activities than the control patients. The patients who had more severe psychiatric symptoms used more negative and passive coping mechanisms than less severe patients. Conclusion: Vitiligo provoked psychiatric symptoms and difficulties in daily activities. Psychiatrically more severe patients used negative and passive coping mechanisms. Comprehensive dermatologic and psychiatric treatment may be required in the treatment of vitiligo.
심관식(Kwan-Shik Shim),남해곤(Hae-Kon Nam),김용구(Yong-Gu Kim),문영환(Young-Hoan Moon),김상태(Sang-Tae Kim) 대한전기학회 2009 전기학회논문지 Vol.58 No.7
The present study explained the phenomenon that low frequency oscillation is synchronized with discrete data obtained from a wide area system, and a sync search method. When a disturbance occurs in an power system, various controllers operate in order to maintain synchronization. If the system’s damping is poor, low frequency oscillations continue for a long time and the oscillations are synchronized with one another at specific frequency. The present study estimated dominant modes, magnitude and phase of signals by applying parameter estimation methods to discrete signals obtained from an power system, and performed sync search among wide area signals by comparing the estimated data. Sync search was performed by selecting those with the same frequency and damping constant from dominant oscillation modes included in a large number of signals, and comparing their magnitude and phase. In addition, we defined sync indexes in order to indicate the degree of sync between areas in a wide area system. Furthermore, we proposed a wide area sync search method by normalizing mode magnitude in discrete data obtained from critical generator of the wide area. By applying the sync search method and sync indexes proposed in this study to two area systems, we demonstrated that sync scanning can be performed for discrete signals obtained from power systems.