In the three-phase power system using the three-phase motor, when any one-phase is open-phase, the unbalanced current flows and the single-phase power supplied by power supply produces overcurrent to motor coil. As a result, the enormous damage and electrical fire can be given to the power system. Recently, the thermal over-current relay (THR) or electronic motor protection relay (EMPR) is mostly used as the open-phase detection device of the three-phase motor. When the over-current or overheat of electric line is generated, it detects and operates circuit breaker, but there is the defect that the sensing speed is slow, the operation can be sometimes failed, and the precision is decreased. In order to improve these problems, this paper is proposed a new control circuit topology for openphase protection using semiconductor devices. Therefore, the proposed open-phase protection device (OPPD) enhances the sensing speed and precision, and has the advantage of simple fitting in the three-phase motor control panel in the field, as it manufactures into small size and light weight. As a result, the proposed OPPD protects the three-phase motor, minimizes the electrical fire from openphase, and contributes for the stable driving of the power system. The performance and confidence of the proposed OPPD is confirmed by a great variety of the experiments of operation characteristic.
This study investigates turbulent flow around a square cylinder mounted on a flat surface at high Reynolds number using a large-eddy simulation (LES) model, particularly focusing on vortex streets behind the square cylinder. Total 9 simulation cases with different inflow wind directions, inflow wind speeds, and cylinder widths in the x- and y-directions are considered to examine the effects of inflow wind direction, speed, and cylinder widths on turbulent flow and vortex streets. In the control case, the inflow wind parallel to the x-direction has a maximum speed of $5m\;s^{-1}$ and the width and height of the cylinder are 50 m and 200 m, respectively. In all cases, down-drafts in front of the cylinder and updrafts, wakes, and vortex streets behind the cylinder appear. Low-speed flow below the cylinder height and high-speed flow above it are mixed behind the cylinder, resulting in strong negative vertical turbulent momentum flux at the boundary. Accordingly, the magnitude of the vertical turbulent momentum flux is the largest near the cylinder top. In the case of an inflow wind direction of $45^{\circ}$, the height of the boundary is lower than in other cases. As the inflow wind speed increases, the magnitude of the peak in the vertical profile of mean turbulent momentum flux increases due to the increase in speed difference between the low-speed and high-speed flows. As the cylinder width in the y-direction increases, the height of the boundary increases due to the enhanced updrafts near the top of the cylinder. In addition, the magnitude of the peak of the mean turbulent momentum flux increases because the low-speed flow region expands. Spectral analysis shows that the non-dimensional vortex generation frequency in the control case is 0.2 and that the cylinder width in the y-direction and the inflow wind direction affect the non-dimensional vortex generation frequency. The non-dimensional vortex generation frequency increases as the projected width of the cylinder normal to the inflow direction increases.
Park, Deuk-Jin;Park, Seong-Bug;Yang, Hyeong-Sun;Yim, Jeong-Bin
Journal of the Korean Society of Marine Environment & Safety
/
v.22
no.3
/
pp.278-285
/
2016
The key features of maritime accidents are the change of their attributes by new risks from time to time. To prevent maritime accidents in Korea, the impacts by new risks on domestic safety environments should be identified or predicted. The purpose of this paper is to find the hazard factors by new risks on maritime safety in Korea. The meaning of new risks is the elements of accident hazard which is compiled from new or rare or unprecedented events in the worldwide maritime transportations. The problems of new risks are the lacks of optimum countermeasures to mitigate accident risks. Using the questionnaires with 152 event scenarios classified by 20 accident causes, the hazard identification and risk analysis of new risks was performed based on the Formal Safety Assessment (FSA) by IMO. A total of 22 Influence Diagrams, which is to depict the transit flows between accident causes to consequences, is used in the construction of 152 event scenarios. A total of 20 accidents causes is the same contents as the causation factors represented in Statistical Year Book for Maritime Accidents of Korean Maritime Safety Tribunals. After defining the evaluation equations to the response results of questionnaires by 46 experts, the work for risk analysis is carried out. As results from the analysis of 152 scenarios, it is known that the root cause to affect on maritime safety in Korea is the pressure of business competition and it led to the lacks of well experienced crews, the overload of vessel operations and crew's fatigue. In addition, as results from the analysis of 20 accident causes, the three accident causes are to be candidate as main issues in Korea such as the inadequate preparedness of departure, the neglecting of watch keeping in bridge and the inadequate management of ship operations. All of the results are thought to be as basic hazard factors to safety impediments. It is thus found that the optimum Risk Control Options to remove the hazard factors and to mitigate consequences required are the following two factors: business competition and crewing problems.
The effects of intra-duodenal infusion of methionine (Met), lysine (Lys) and leucine (Leu) on dry matter intake (DMI), the concentrations of insulin-like growth factor I (IGF-I), growth hormone (GH) and insulin in plasma, and liver IGF-I mRNA level were investigated in two experiments for Liuyang Black growing wether goats. In Experiment 1, three goats ($10.0{\pm}0.1$ kg) were fitted with ruminal, proximal duodenal and terminal ileal fistulaes to determine the infusion amounts of Met, Lys and Leu at the duodenum according to essential amino acid flows into the duodenum and their apparent digestibility. The infusion amounts were 0.77 g/d, 0.91 g/d and 0.58 g/d respectively. In Experiment 2, 4 groups of goats (($10.0{\pm}0.2$ kg) for each group, were cannulated at the duodenum, and were infused with a mixture of Met, Lys and Leu (Control), or mixtures with 21% Met, Lys or Leu replaced with glutamate respectively on a nitrogenous basis. The replacement of 21% Met, Lys or Leu with glutamate did not affect intakes of maize stover, concentrate or both (p>0.05) when compared with the control. The replacement of 21% Met or Lys significantly (p<0.05) reduced plasma GH, insulin and IGF-I concentrations and liver IGF-I mRNA level. The replacement of 21% Leu with glutamate reduced (p<0.05) plasma IGF-I concentration only, but not plasma insulin and GH, as well as liver IGF-I mRNA level (p>0.05). The close relationships between supplying Met and Lys in the lumen of the duodenum and plasma IGF-I, GH and insulin concentrations, as well as liver IGF-I mRNA level in this study indicate that the effects of the limiting amino acids on nutrition of animals are likely intermediated via their effects on these hormones, and these hormone profiles could be used as intermediate markers for the limiting order of amino acids.
The traffic management schemes through traffic signal control and information provision could be effective when the link-level data and trip-level data were used simultaneously in analysis Procedures. But, because the trip-level data. such as origin, destination and departure time, can not be obtained through the existing surveillance systems directly. It is needed to estimate it using the link-level data which can be obtained easily. Therefore the objective of this study is to develop the model to estimate O-D demand using only the link flows in highway network as a real time. The methodological approaches in this study are kalman filer, least-square method and normalized least-square method. The kalman filter is developed in the basis of the bayesian update. The normalized least-square method is developed in the basis of the least-square method and the natural constraint equation. These three models were experimented using two kinds of simulated data. The one has two abrupt changing Patterns in traffic flow rates The other is a 24 hours data that has three Peak times in a day Among these models, kalman filer has Produced more accurate and adaptive results than others. Therefore it is seemed that this model could be used in traffic demand management. control, travel time forecasting and dynamic assignment, and so forth.
Journal of the Korean Society of Marine Environment & Safety
/
v.25
no.6
/
pp.802-808
/
2019
DC motors are used extensively on shipboard, including as the ship's winch operating motor, owing to their simple speed control and excellent output torque characteristics. Moreover, they were used as propulsion motors in the early days of electric propulsion ships. However, mechanical rectifiers, such as brushes, used in DC motors have certain disadvantages. Hence, brushless DC (BLDC) motors are increasingly being used instead. While the electrical characteristics of both types of motors are similar, BLDC motors employ electronic rectifying devices, which use semiconductor elements, instead of mechanical rectifying devices. The inverter system for driving conventional BLDC motors uses a two-phase excitation method so that the waveform of the back electromotive force becomes trapezoidal. This causes harmonics and torque ripple in the phase current switching period in which the winding wire through which the current flows is changed. Researchers have studied and presented various methods to reduce the harmonics and torque ripple. This study applies a cascaded H-bridge multilevel inverter, which implements a proportional-integral speed current controller algorithm in the driving circuit of the BLDC motor for electric propulsion ships using a power analysis program. The simulation results of the modeled BLDC motor show that the driving method of the proposed BLDC motor improves the voltage waveform of the input side of the motor and remarkably reduces the harmonics and torque ripple compared with the conventional driving method.
Journal of the Institute of Electronics Engineers of Korea SD
/
v.44
no.2
/
pp.61-71
/
2007
The instruction level parallelism, which has been used to improve the performance of processors, expose its limit. The change of a control flow by a branch miss prediction is one of the obstacles that restrict the instruction level parallelism. The single chip multiprocessors have been developed to utilize the thread level parallelism. However, we could not use the maximum performance of the single chip multiprocessor in case of executing the coded programs without considering the multi-thread. In order to overcome the two performance degradation factors, in this paper, we suggest the concurrent branch execution method that applies to the multi-path execution method at a single chip multiprocessor. We executes all two flows of the conditional branch using the idle core processor. Through this, we can improve the processor's efficiency with blocking the control flow termination by the branch instruction and reducing the idle time. We analyze the effects of concurrent branch execution proposed in this paper through the simulation. As a result of that, concurrent branch execution reduces about 20% of idle time and improves the maximum 10% of the branch prediction accuracy. We show that our scheme improves the overall performance of maximum 39% compared to the normal single chip multiprocessor and maximum 27% compared to the superscalar processor.
Lee, Bong Hyo;Lim, Sung Chul;Kim, Jae Soo;Lee, Yun Kyu;Lee, Hyun Jong;Jung, Tae Young;Lee, Sang Nam
Korean Journal of Acupuncture
/
v.30
no.3
/
pp.145-150
/
2013
Objectives : The aim of this study is to review the acupoints used in cocaine studies and interpret the effectiveness in an aspect of meridian theory of Korean medicine. Methods : Authors searched 50 articles in PubMed, 16 in KISS, 9 in OASIS, 40 in NDSL, and 19 in DBPIA, with the keyword of 'cocaine' or 'acupuncture'. The articles written in English only were included. The articles related with cocaine(abuse, dependence, sensitization, intake, withdrawal sign, withdrawal syndrome, reinstatement, seeking) only were subjected. The articles which used manual- or electro-acupuncture were included, and auricular was excluded. Results : The most frequently used acupoint was HT7, while LI4, LU9, ST36, and SP6 were used once respectively. HT7 could be understood to be used from the meaning of the name as well as the theory that Heart Meridian is deeply related with the brain function. LU9 seems to be used to enhance the effect of HT7. LI4 is thought to control reverting yin that flows toward the top of head following the theory of Jang Bu Sang Tong. ST36 appears to be used because it could regulate stress reaction that reverting yin is associated with. SP6 seems to have effect on brain function due to its ability to control spiritual disorder. Conclusions : The acupoints used in the cocaine studies are thought to influence the brain function through diverse mechanism, and Jang Bu Sang Tong theory seems to be involved in the mechanism, at least in part.
Transactions of the Korean Society of Mechanical Engineers A
/
v.39
no.11
/
pp.1123-1129
/
2015
A pair of two-way valves typically is used in automotive washing machines, where the water flow direction is frequently reversed and highly pressurized clean water is sprayed to remove the oil and dirt remaining on machined engine and transmission blocks. Although this valve system has been widely used because of its competitive price, its application is sometimes restricted by surging effects, such as pressure ripples occurring in rapid changes in water flow caused by inaccurate valve control. As an alternative, one three-way reversing valve can replace the valve system because it provides rapid and accurate changes to the water flow direction without any precise control device. However, a cavitation effect occurs because of the complicated bottom plug shape of the valve. In this study, the cavitation index and percent of cavitation (POC) were introduced to numerically evaluate fluid flows via computational fluid dynamics (CFD) analysis. To reduce the cavitation effect generated by the bottom plug, the optimal shape design was carried out through a parametric study, in which a simple computer-aided engineering (CAE) model was applied to avoid time-consuming CFD analysis and difficulties in achieving convergence. The optimal shape design process using full factorial design of experiments (DOEs) and an artificial neural network meta-model yielded the optimal waist and tail length of the bottom plug with a POC value of less than 30%, which meets the requirement of no cavitation occurrence. The optimal waist length, tail length and POC value were found to 6.42 mm, 6.96 mm and 27%, respectively.
Three plans(induction of water flow, supply of oxygen into water, control of fish causing resuspension of solids) proposed to improve the pollutant removal efficiency of Sihwa Constructed Wetland(CW) were estimated by considering the their efficiency and application to the wetland. After construction of facility for induction of water flow in lower part(W 122m${\times}$L 103m) of the wetland, the mean removal efficiencies of BOD, SS, TN and TP were in range of 12.8~37.4% and BOD was showing the highest efficiency. This result indicates that water flows is one of very important factors in the pollutant removal of wetland, especially near the outlet of a large scale wetland such as Sihwa CW. Dissolved oxygen(DO) concentrations after operation of two oxygen supply systems such as Air Bubble Diffuser and Surface Aeration System increased 15.5% and 27.2%, respectively. For maintaining effective DO concentration in Sihwa CW, the operation of oxygen supply system may be desirable during midnight to dawn in the location in which DO concentration is not enough, for instance less than 2 mg/L in CW. In experiments of the fish removal from Sihwa CW, the mean turbidity was lower in test site(6.2 NTU) than control site(10.6). The removal efficiency of thurbidity by th fish removal from the wetland was 41.5%. Therefore, a relevant fish management through a periodical monitoring of fish and turbidity is needed.
본 웹사이트에 게시된 이메일 주소가 전자우편 수집 프로그램이나
그 밖의 기술적 장치를 이용하여 무단으로 수집되는 것을 거부하며,
이를 위반시 정보통신망법에 의해 형사 처벌됨을 유념하시기 바랍니다.
[게시일 2004년 10월 1일]
이용약관
제 1 장 총칙
제 1 조 (목적)
이 이용약관은 KoreaScience 홈페이지(이하 “당 사이트”)에서 제공하는 인터넷 서비스(이하 '서비스')의 가입조건 및 이용에 관한 제반 사항과 기타 필요한 사항을 구체적으로 규정함을 목적으로 합니다.
제 2 조 (용어의 정의)
① "이용자"라 함은 당 사이트에 접속하여 이 약관에 따라 당 사이트가 제공하는 서비스를 받는 회원 및 비회원을
말합니다.
② "회원"이라 함은 서비스를 이용하기 위하여 당 사이트에 개인정보를 제공하여 아이디(ID)와 비밀번호를 부여
받은 자를 말합니다.
③ "회원 아이디(ID)"라 함은 회원의 식별 및 서비스 이용을 위하여 자신이 선정한 문자 및 숫자의 조합을
말합니다.
④ "비밀번호(패스워드)"라 함은 회원이 자신의 비밀보호를 위하여 선정한 문자 및 숫자의 조합을 말합니다.
제 3 조 (이용약관의 효력 및 변경)
① 이 약관은 당 사이트에 게시하거나 기타의 방법으로 회원에게 공지함으로써 효력이 발생합니다.
② 당 사이트는 이 약관을 개정할 경우에 적용일자 및 개정사유를 명시하여 현행 약관과 함께 당 사이트의
초기화면에 그 적용일자 7일 이전부터 적용일자 전일까지 공지합니다. 다만, 회원에게 불리하게 약관내용을
변경하는 경우에는 최소한 30일 이상의 사전 유예기간을 두고 공지합니다. 이 경우 당 사이트는 개정 전
내용과 개정 후 내용을 명확하게 비교하여 이용자가 알기 쉽도록 표시합니다.
제 4 조(약관 외 준칙)
① 이 약관은 당 사이트가 제공하는 서비스에 관한 이용안내와 함께 적용됩니다.
② 이 약관에 명시되지 아니한 사항은 관계법령의 규정이 적용됩니다.
제 2 장 이용계약의 체결
제 5 조 (이용계약의 성립 등)
① 이용계약은 이용고객이 당 사이트가 정한 약관에 「동의합니다」를 선택하고, 당 사이트가 정한
온라인신청양식을 작성하여 서비스 이용을 신청한 후, 당 사이트가 이를 승낙함으로써 성립합니다.
② 제1항의 승낙은 당 사이트가 제공하는 과학기술정보검색, 맞춤정보, 서지정보 등 다른 서비스의 이용승낙을
포함합니다.
제 6 조 (회원가입)
서비스를 이용하고자 하는 고객은 당 사이트에서 정한 회원가입양식에 개인정보를 기재하여 가입을 하여야 합니다.
제 7 조 (개인정보의 보호 및 사용)
당 사이트는 관계법령이 정하는 바에 따라 회원 등록정보를 포함한 회원의 개인정보를 보호하기 위해 노력합니다. 회원 개인정보의 보호 및 사용에 대해서는 관련법령 및 당 사이트의 개인정보 보호정책이 적용됩니다.
제 8 조 (이용 신청의 승낙과 제한)
① 당 사이트는 제6조의 규정에 의한 이용신청고객에 대하여 서비스 이용을 승낙합니다.
② 당 사이트는 아래사항에 해당하는 경우에 대해서 승낙하지 아니 합니다.
- 이용계약 신청서의 내용을 허위로 기재한 경우
- 기타 규정한 제반사항을 위반하며 신청하는 경우
제 9 조 (회원 ID 부여 및 변경 등)
① 당 사이트는 이용고객에 대하여 약관에 정하는 바에 따라 자신이 선정한 회원 ID를 부여합니다.
② 회원 ID는 원칙적으로 변경이 불가하며 부득이한 사유로 인하여 변경 하고자 하는 경우에는 해당 ID를
해지하고 재가입해야 합니다.
③ 기타 회원 개인정보 관리 및 변경 등에 관한 사항은 서비스별 안내에 정하는 바에 의합니다.
제 3 장 계약 당사자의 의무
제 10 조 (KISTI의 의무)
① 당 사이트는 이용고객이 희망한 서비스 제공 개시일에 특별한 사정이 없는 한 서비스를 이용할 수 있도록
하여야 합니다.
② 당 사이트는 개인정보 보호를 위해 보안시스템을 구축하며 개인정보 보호정책을 공시하고 준수합니다.
③ 당 사이트는 회원으로부터 제기되는 의견이나 불만이 정당하다고 객관적으로 인정될 경우에는 적절한 절차를
거쳐 즉시 처리하여야 합니다. 다만, 즉시 처리가 곤란한 경우는 회원에게 그 사유와 처리일정을 통보하여야
합니다.
제 11 조 (회원의 의무)
① 이용자는 회원가입 신청 또는 회원정보 변경 시 실명으로 모든 사항을 사실에 근거하여 작성하여야 하며,
허위 또는 타인의 정보를 등록할 경우 일체의 권리를 주장할 수 없습니다.
② 당 사이트가 관계법령 및 개인정보 보호정책에 의거하여 그 책임을 지는 경우를 제외하고 회원에게 부여된
ID의 비밀번호 관리소홀, 부정사용에 의하여 발생하는 모든 결과에 대한 책임은 회원에게 있습니다.
③ 회원은 당 사이트 및 제 3자의 지적 재산권을 침해해서는 안 됩니다.
제 4 장 서비스의 이용
제 12 조 (서비스 이용 시간)
① 서비스 이용은 당 사이트의 업무상 또는 기술상 특별한 지장이 없는 한 연중무휴, 1일 24시간 운영을
원칙으로 합니다. 단, 당 사이트는 시스템 정기점검, 증설 및 교체를 위해 당 사이트가 정한 날이나 시간에
서비스를 일시 중단할 수 있으며, 예정되어 있는 작업으로 인한 서비스 일시중단은 당 사이트 홈페이지를
통해 사전에 공지합니다.
② 당 사이트는 서비스를 특정범위로 분할하여 각 범위별로 이용가능시간을 별도로 지정할 수 있습니다. 다만
이 경우 그 내용을 공지합니다.
제 13 조 (홈페이지 저작권)
① NDSL에서 제공하는 모든 저작물의 저작권은 원저작자에게 있으며, KISTI는 복제/배포/전송권을 확보하고
있습니다.
② NDSL에서 제공하는 콘텐츠를 상업적 및 기타 영리목적으로 복제/배포/전송할 경우 사전에 KISTI의 허락을
받아야 합니다.
③ NDSL에서 제공하는 콘텐츠를 보도, 비평, 교육, 연구 등을 위하여 정당한 범위 안에서 공정한 관행에
합치되게 인용할 수 있습니다.
④ NDSL에서 제공하는 콘텐츠를 무단 복제, 전송, 배포 기타 저작권법에 위반되는 방법으로 이용할 경우
저작권법 제136조에 따라 5년 이하의 징역 또는 5천만 원 이하의 벌금에 처해질 수 있습니다.
제 14 조 (유료서비스)
① 당 사이트 및 협력기관이 정한 유료서비스(원문복사 등)는 별도로 정해진 바에 따르며, 변경사항은 시행 전에
당 사이트 홈페이지를 통하여 회원에게 공지합니다.
② 유료서비스를 이용하려는 회원은 정해진 요금체계에 따라 요금을 납부해야 합니다.
제 5 장 계약 해지 및 이용 제한
제 15 조 (계약 해지)
회원이 이용계약을 해지하고자 하는 때에는 [가입해지] 메뉴를 이용해 직접 해지해야 합니다.
제 16 조 (서비스 이용제한)
① 당 사이트는 회원이 서비스 이용내용에 있어서 본 약관 제 11조 내용을 위반하거나, 다음 각 호에 해당하는
경우 서비스 이용을 제한할 수 있습니다.
- 2년 이상 서비스를 이용한 적이 없는 경우
- 기타 정상적인 서비스 운영에 방해가 될 경우
② 상기 이용제한 규정에 따라 서비스를 이용하는 회원에게 서비스 이용에 대하여 별도 공지 없이 서비스 이용의
일시정지, 이용계약 해지 할 수 있습니다.
제 17 조 (전자우편주소 수집 금지)
회원은 전자우편주소 추출기 등을 이용하여 전자우편주소를 수집 또는 제3자에게 제공할 수 없습니다.
제 6 장 손해배상 및 기타사항
제 18 조 (손해배상)
당 사이트는 무료로 제공되는 서비스와 관련하여 회원에게 어떠한 손해가 발생하더라도 당 사이트가 고의 또는 과실로 인한 손해발생을 제외하고는 이에 대하여 책임을 부담하지 아니합니다.
제 19 조 (관할 법원)
서비스 이용으로 발생한 분쟁에 대해 소송이 제기되는 경우 민사 소송법상의 관할 법원에 제기합니다.
[부 칙]
1. (시행일) 이 약관은 2016년 9월 5일부터 적용되며, 종전 약관은 본 약관으로 대체되며, 개정된 약관의 적용일 이전 가입자도 개정된 약관의 적용을 받습니다.