합성고분자첨가제의 난류마찰저항 감소효과 연구

김남수,김종보,김인석,최형진,Kim, N.S.,Kim, C.B.,Kim, I.S.,Choi, H.J. 대한설비공학회 1993 설비공학 논문집 Vol.5 No.3

Experimental investigations have been carried out to find the effect of drag reduction caused by effective polymer additives in turbulent flows. The experiments were undertaken with a test section of 9.8mm pipe diameter and 3500 mm pipe length(L/D=357) in a closed loop, and Copolymer-X and Polyacrylamide(PAAM) were used as polymer additives for comparisons. The tests were carried out under different polymer concentrations, and the temperatures of the flow considered were $26^{\circ}C$, $60^{\circ}C$ at the flow velocity of 5.3 m/s. The rate of drag reduction obtained by Copolymer-X is found to be considerably higher than that of PAAM in turbulent flows. Copolymer-X is also found to be very reliable for mechanical degradation, which has not been the case in any other additives. It is concluded that Copolymer-X is considered to be one of the most effective agents as an additive especially for long time hydraulic transports. It is also found that polymer degradation in more likely at lower polymer concentrations in the turbulent flows.

Dual Gate Emitter Switched Thyristor의 전기적 특성

김남수,이응래,최지원,김영석,김경원,주변권,Kim, Nam-Soo,Lee, Eung-Rae,Cui, Zhi-Yuan,Kim, Yeong-Seuk,Kim, Kyoung-Won,Ju, Byeong-Kwon 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.5

Two dimensional MEDICI simulator is used to study the electrical characteristics of Dual Gate Emitter Switched Thyristor. The simulation is done in terms of the current-voltage characteristics with the variations of p-base impurity concentrations and current flow. Compared with the other power devices such as MOS Controlled Cascade Thyristor(MCCT), Conventional Emitter Switched Thyristor(C-EST) and Dual Channel Emitter Switched Thyristor(DC-EST), Dual Gate Emitter Switched Thyristor(DG-EST) shows to have tile better electrical characteristics, which is the high latch-up current density and low forward voltage-drop. The proposed DG-EST which has a non-planer u-base structure under the floating N+ emitter indicates to have the better characteristics of latch-up current and breakover voltage in spite of the same turn-off characteristics.

CDF 스케쥴링을 적용한 상향링크 NOMA 시스템의 오수신 성능

김남수,Kim, Nam-Soo 한국인터넷방송통신학회 2021 한국인터넷방송통신학회 논문지 Vol.21 No.4

NOMA (Non-orthogonal multiple Access) 시스템은 스펙트럼의 효율이 높아서 차세대 이동통신 방식으로 주목을 받고 있지만, 여러 사용자가 동시에 채널을 엑세스 하는 다중 사용자 시스템이므로 사용자 스케쥴링이 필요하다. 대표적인 스케쥴링 방식으로 PF (Proportional fairness) 스케쥴링 방식과 CDF (Cumulative distribution function) 스케쥴링 방식이 있는데, PF 스케쥴링 방식은 셀 가장자리에 위치한 사용자는 전송기회를 갖기가 매우 어렵다. 그러므로 최근에는 사용자들의 위치와 무관하게 동일한 전송기회를 갖는 CDF 스케쥴링이 주목을 받고 있다. 본 논문에서는 상향 NOMA 시스템에 CDF 스케쥴링을 적용하였을 때 사용자의 채널 획득확률, 사용자 수에 따른 오수신율, 그리고 송신 가중치에 따른 시스템의 오수신율을 시뮬레이션을 통하여 구하였다. 시뮬레이션 결과 각각의 사용자들의 채널 획득 확률이 동일함을 확인하였고, 사용자의 수가 증가할수록 오수신율은 감소하였다. 그리고 셀 가장 자리에 있는 사용자의 송신 가중치를 증가하여도 시스템의 오수신율에 미치는 영향은 미미함을 알 수 있었다. NOMA (Non-orthogonal multiple Access) system has been focused on the next generation cellular system for higher spectral efficiency. However, this requires user scheduling as the NOMA system is a multi-user system which accesses simultaneously. There are two representative scheduling schemes, proportionate scheduling (FP) and cumulative distribution function (CFD) scheduling. The PF scheduling is applied, the cell edge user is hard to obtain a transmit opportunity. Recently, CDF scheduling is obviously noted that it offers the same possibility of transmission for a user regardless of the location in a cell. We consider an uplink NOMA system with CDF scheduling, and obtain the channel access probabilities, the outage probabilities of the system with different number of users and different kinds of weights through simulation. The results indicate that the likelihood of each user accessing the channel is the same and the probability of failure decreases as the number of users increases. We found that the effect of the probability of failure is negligible as the weight of the cell edge user increases.

고압응용 생명과학의 미래

김남수,Kim, Nam-Soo 한국식품연구원 2011 食品技術 Vol.24 No.1

신기술 신소재: 중금속 생체지표인 메탈로티오닌의 나노리터 수준 전기화학 검출기술

김남수,Kim, Nam-Soo 한국식품연구원 2010 食品技術 Vol.23 No.2

상향링크 NOMA 시스템의 성능 해석 방법 비교 연구

김남수,Kim, Nam-Soo 한국인터넷방송통신학회 2020 한국인터넷방송통신학회 논문지 Vol.20 No.5

최근 차세대 이동통신 시스템에 적용하기 위하여 비직교 다중화 (Non-orthogonal multiple access, NOMA) 방식이 많은 주목을 받고 있다. 그런데 NOMA 시스템에서는 동일한 통신자원에 많은 사용자를 중첩하므로 필수적으로 사용자 간섭이 존재하게 된다. 그동안 사용자 간섭을 해석하기 위하여 대표적으로 근사 백색잡음 방식과 랜덤변수 방식의 두 가지 방식을 사용해 왔다. 본 논문에서는 이 두 가지 방법을 NOMA 시스템의 상향 링크에 적용하여 사용자의 오수신률을 각각 유도하고 두 가지 방식의 결과를 서로 비교하였다. 송신전력에 따른 오수신률, 거리에 따른 오수신률, 그리고 전력할당에 따른 오수신률의 수치적인 결과를 각각 비교하였다. 비록 두 가지 방식에서 유도한 수식 표현은 서로 다르지만, 수치적인 예에서는 서로 동일한 결과를 얻었다. 따라서 본 논문의 결과는 NOMA 시스템을 해석하는데 두 가지 방식 모두 적용이 가능하다는 것을 보여주었다. Recently, non-orthogonal multiple access (NOMA) have been received considerable attention to be involved in the next generation mobile system. However, there are inherent inter-user interferences caused by the multiplexing multiple users in the same communication resource in NOMA systems. Two representative methods, the approximate white noise and random variable methods, have been adapted for the analysis of interferences in NOMA systems. In this paper, we derive the outage probabilities of an uplink NOMA system with the two analysis methods and compare the results. The numerical results of the outage probabilities versus transmitted power, distances, and power allocation are compared. We noticed that the derived functions are different each other, but the numerical results are coincident. It is shown that the two interference analysis methods can be applied to the analysis of NOMA systems.

Cell Traffic Untensity 에 따른 DS-CDMA 셀룰러 시스템의 최소기간 차단율

김남수,Kim, Nam-Soo 한국전자파학회 2001 한국전자파학회논문지 Vol.12 No.4

셀룰러 시스템에서 최소기간 차단율은 수신된 신호 레벨이 최소기간 이상 계속하여 임계치 이하로 될 확률을 의미한다. 이는 수신 신호만을 대상으로 하여 임계치 이하로 될 때는 오수신으로 정의하는 것보다 더욱 현실적이다. 특히 DS-CDMA 셀룰러 시스템에서는 셀의 통화량에 따라서 수신되는 신호대 간섭비가 계속하여 가변되는데 기존의 해석에서는 셀의 통화량과는 무관하게 최소기간 차단율을 해석하였으나, 이 논문에서는 셀의 통화량에 따른 최소기간 차단을 유도한다. 해석결과 셀의 통화량이 증가할수록 최소기간 오수신율을 급격히 증가함을 알 수 있었다. The minimum duration outage probability of a cellular system is defined the probability that the received signal level is hold under minimum required threshold duration. This definition is more realistic compared to the outage probability which is the received signal strength level is below predefined threshold level. Especially, in a DS-CDMA cellular system the received signal-to-interference ratio is a function of cell traffic, while the former researches are only considered the minimum duration outage probability independent of the cell traffic. We noticed that the minimum outage probability is rapidly increases as cell traffic increase.

양자점 표지 형광미세비드의 합성 및 응용

김남수,Kim, Nam-Soo 한국식품연구원 2009 食品技術 Vol.22 No.3

골혈성 지표로써 bone alkaline phosphatase(BALP)와 TALP치에 대한 BALP치 비율(B/T)의 응용

김남수,최인혁,Kim, Nam-soo,Choi, In-hyuk 대한수의학회 1999 大韓獸醫學會誌 Vol.39 No.6

Twenty-one dogs(male 11 heads, female 10 heads) which were about 16 months ($16.3{\pm}3.5$) old and 10kg($10.1{\pm}2.0$) body weight, were allotted randomly into four groups as follows. Group I consisted of five dogs whose muscles were operated for sham muscle injuries. Group II consisted of seven dogs treated for cystic duct obstruction. Group III consisted of five dogs treated for the union fracture model. Group IV consisted of five dogs treated for the non-union fracture model. Radiographical and histological observations were carried out to determine bone alkaline phosphatase(BALP) and total alkaline phosphatase(TALP) values of each group for 20 weeks after the treatments with the condition of new bone formation. And also the applicability of percentage of BALP values to TALP (B/T) was studied after BALP was compared respectively with TALP. The level of TALP was increased without any relation to bone formation in group II, and all levels of BALP and B/T were increased in group III. The mean of B/T was high in statistical significance, due to varied levels of B/T and BALP. The changes of rates of B/T were significantly increased only in the case of the active new bone formation in group III, union fracture model. It was recognized that the mean values of B/T were statistical significant of the high applicability of the B/T ratio as an index of bone formation.

흰쥐에서 난소제거술로 유발시킨 골다공증시 osteocalcin, bone- specific alkaline phosphatase, estrogen, IGF-I, Ca²⁺, P와 bone density의 변화

김남수,유유순,강창원,최인혁,Kim, Nam-soo,You, You-soon,Kang, Chang-won,Choi, In-hyuk 대한수의학회 2000 大韓獸醫學會誌 Vol.40 No.4

The aim of this investigation was to examine the effects of osteocalcin, bone-specific alkaline phophatase, estrogen, insulin-like growth factor-I (IGF-I), Ca, P and bone mineral density on osteoporosis induced by ovariectomy in rats. Female Sprague-Dawley 30 rats of three-forth's birth, weighing $215{\pm}10g$, were divided into two groups including the sham operation group(5 heads) and ovariectomy group(25 heads). They were fed normal diets for 2 weeks before the experimental operation and for 8 more weeks after operation. The level of osteocalcin, TALP, BALP, estrogen, bone mineral density and IGF-I were increased in experimental group, but a little increased in sham operation group at same period. The change of rates of osteocalcin, TALP, BALP, estrogen, bone mineral density and IGF-I were significantly higher in experimental group than sham operation group. $Ca^{2+}$ was not changed between two groups and P was significantly decreased in experimental group and Ca/P ratio was higher in experimental group than sham operation group. Body weights were increased in all two groups and growth rate per day was higher in experimental group than sham operation group. However, femur weight I body weight ratio was lower in experimental group than sham operation group.