• Journal of Electrical Engineering and Technology
• /
• 제12권5호
• /
• pp.1689-1696
• /
• 2017

In recent academic and industrial circles of the Republic of Korea, the securement of available reactive power reserve against the line faults is at issue. Thus, simulations have been performed for the securing of effective reactive power reserve (effective Q) to prepare for the line faults and improve reactive power monitoring and control methods. That is, a research has been conducted for the fast-decoupled Newton-Raphson method. In this study, a method that distinguishes source and sink regions to carry out faster provision of information in the event of line fault has been proposed. This method can perform quantification with the formula that calculates voltage variations in the line flow. The line flow and voltage changes can be easily induced by the power flow calculation performed every second in the operation system. It is expected that the proposed method will be able to contribute to securement of power system stability by securing efficient reactive power. Also, the proposed method will be able to contribute to prepare against contingencies effectively. It is not easy to prepare quickly for the situation where voltage drops rapidly due to the exhaustion of reactive power source by observing voltage information only. This paper's simulation was performed on the large scale Korean power system in steady state.

• 한국도로학회논문집
• /
• 제18권6호
• /
• pp.145-152
• /
• 2016

OBJECTIVES : Visibility at night can be improved by using retroreflection for short distances and phosphorescent line markings for long distances. In this study, we analyzed the characteristics of the phosphorescent line marking through a laboratory luminance test. Field performance analysis was performed through tests conducted on the road. We also examined the luminance measurement methods using the digital image obtained during the phosphorescent visibility evaluation. METHODS : In this study, the laboratory luminance test of the phosphorescent line marking was conducted using seven specimens to characterize the luminance changes according to the type of the glass beads, the thickness of the phosphorescent line marking, and the brightness and irradiation time of the light source. Phosphorescent and general line markings were made at 150 m to investigate the field luminance performance. A preliminary review of the luminance measurement methods was made using a digital image from a digital single-lens reflex (DSLR) camera. The measured luminance ratio of the general and the phosphorescent line markings was compared with the calculated luminance ratio using luminance analysis. RESULTS : Through the laboratory luminance test, it was seen that the change in luminance, which corresponds to the brightness of the light source, appears large but the influence of the thickness and irradiation time is low. The field performance test of the phosphorescent line marking conducted on the road involved measuring the luminance on the day the marking was made and 7 days after the marking was made. The luminance was found to be $190mcd/m^2$ at 30 min after sunset and approximately $10-12mcd/m^2$ 4h after sunset. The results of the luminance test were captured using a digital image for each time group. The luminance ratio of the phosphorescent line marking, when compared to that of the general line marking, showed a similar trend within a 13% maximum error. Additionally, when this luminance ratio is compared to the direct field measurement, it could be confirmed that the luminance ratio, as captured in the digital image, showed a similar tendency. CONCLUSIONS : 1) The change in luminance corresponding to the brightness of the light source is significant in comparison with that corresponding to the thickness and the irradiation time. In addition, the results of the field test for the phosphorescent line marking satisfied the phosphorescent fire protection standard. 2) We examined the validity of the luminance measurement method using a digital image and we concluded that the change in the luminance ratio shows a similar tendency in both the cases. The results can form the basis for luminance measurement methodology for the construction and maintenance of phosphorescent line markings.

• 한국전자통신학회논문지
• /
• 제10권1호
• /
• pp.39-46
• /
• 2015

본 논문은 유니코드 한글글자마디부호를 사용할 때 스크램블링으로 인하여 회선부호기의 데이터 전송효율에 미치는 영향을 연구하였다. 회선부호기의 스크램블링은 원천부호의 문제를 해결하기 위한 것이다. 본 논문은 장거리전송에 사용되는 AMI회선부호화에 적용하는 국제표준방식인 HDB-3 스크램블링 방식을 토대로 하였다. 본 연구에 필요한 한글글자마디와 이에 대한 사용빈도는 국립국어원의 한국어자료를 분석한 데이터를 사용하였다. 연구결과 유니코드 한글글자마디에서 평균 24%의 스크램블링이 발생하였다. 유니코드 한글글자마디부호에 참고된 한글글자마디를 적용할 경우에 평균 27%의 스크램블링이 발생하였다. 유니코드 총 11,172개의 한글글자마디에서 스크램블링이 발생하지 않는 글자마디는 총 8,928개였다. 그러므로 참고된 한글글자마디 총1,540자를 스크램블링이 발생하지 않는 부호영역에 수용하여 스크램블링이 발생되지 않는 원천부호체계를 만드는 것이 가능하다는 결론을 도출하였다. 새로운 한글글자마디 부호체계를 적용할 경우, 27%의 스크램블링을 완전히 제거할 수 있다. 또한 물리계층의 회선 부호화기에서 발생하는 스크램블링을 표현계층에서 소프트웨어 적으로 수행하게 되어, 회선부호기의 데이터전송처리 효율을 최소 27%이상 제고시킬 수 있다.

• 공학교육연구
• /
• 제9권4호
• /
• pp.63-70
• /
• 2006

여러 분야에서 온라인 교육이 활성화되고 있지만, 온라인 교육의 효율성에 관해서는 많은 사람이 회의적이다. 이러닝에서는 교수자의 역할이 중요한데, "e-moderator" 라는 말이 나올 정도로 학습의 중재자로서의 역할이 강조되고 있다. 그러나 실제적으로 이러한 역할은 이러닝에서 교수자와 관리자간에 서로 책임을 전가하는 경향이 있다. 또 다른 측면에서는 오픈소스의 활용이 활성화되고 결과물을 활용하여 무료로 이러닝 환경을 구축할 수 있는데도 불구하고 국내에서의 활용 율은 상당히 낮은 실정이다. 본 논문에서는 어떻게 이러한 오픈소스 결과물을 가지고 온라인 환경을 구축하고 "e-moderator"의 역할에 충실하면서 블렌디드 러닝까지 확장하여 활용할 수 있는지를 교육 현장에서의 구현 사례를 중심으로 기술하고자 한다. Moodle을 LMS(Learning Management System)으로 사용하였으며 2006년도 2학기에 공주대학교에서 자바와 전기기기에 적용하여 수업을 진행한 내용을 반영하였다.

• 한국생물공학회:학술대회논문집
• /
• 한국생물공학회 2003년도 생물공학의 동향(XII)
• /
• pp.343-347
• /
• 2003

황토볼을 이용하여 폐수처리를 한 결과 다음과 같은 결과를 보였다. 흐름도 A에서는 T-P 0.5ppm이하, T-N 1.0 ppm이하, COD 10ppm 이하였으며, 흐름도 B에서는 T-P 0.3ppm이하, T-N 5.0 ppm이하, COD 15 ppm 이하의 결과를 보여 주었다. 흐름도 C에서는 T-P 0.6ppm이하, T-N 10 ppm이하, COD 15 ppm 이하였으며, 흐름도 D에서는 T-P 1 ppm, T-N 8 ppm이하, COD 20ppm 이하의 결과를 보여 주었다. BOD는 각 흐름도 A, B, C, D에서 COD보다 높은 경우에는 6 ppm, 낮은 경우에는 3 ppm 정도의 차이를 보였다. SS는 각 공정에 따라 그다지 큰 차이를 보이고 있지 않으며, 1.0 처리 용량 Ton/day으로 계산 할 경우에 5 - 20 g/day 정도를 보이고 있다. 이러한 결과치는 하수종말처리장(특별대책지역 및 잠실수중보권지역)의 2 ppm 및 폐수처리시설(농공단지, 오${\cdot}$폐수처리시설 포함)의 T-P 8 ppm, T-N 질소성분 60 ppm이내의 탄소원 COD 40 ppm 이내의 기준에 해당하는 수치의 좋은 결과로 황토볼을 이용한 폐수처리 시스템의 가능성을 보여주고 있다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.250.1-250.1
• /
• 2014

A multicusp ion source has been used widely in negative hydrogen cyclotrons mainly for radioisotope productions. The ion source is designed to have cusp geometries of magnetic field inside plasma chamber, where ions are confining and their mean lifetimes increase. The magnetic confinement produced a number of permanent magnetic poles helps to increase beam currents and reduce the emittance. Therefore optimizing the number of magnets confining more ions and increasing their mean lifetime in plasma has to be investigated in order to improve the performance of the ion source. In this work a numerical simulation of the magnetic flux density from a number of permanent magnets is carried to optimize the cusp geometries producing the highest plasma density, which is clearly indicated along the full-line cusp geometry. The effect of magnetic fields and a number of poles on the plasma structure are investigated by a computing tool. The electron confinement effect becomes stronger and the density increases with increasing the number of poles. On the contrary, the escape of electrons from the loss cone becomes more frequent as the pole number increases [1]. To understand above observation the electron and ion's trajectories along with different cusp geometries are simulated. The simulation has been shown that the optimized numbers of magnets can improve the ion density and uniformity.

• 전자공학회논문지A
• /
• 제33A권3호
• /
• pp.107-116
• /
• 1996

Recently, the flash memory has been abstracting great attention in the semiconductor market in the world because of its potential applications as mass storage devices. One of the most significant barriers to the scalling-down of the stacked-gate devices such as EPROM's and flash EEPROM's is the large subthreshold leakage in the unselected cells connected with the bit line of a selected cell in the array during programming. The large subthreshold leakge is majorly due to the capacitive coupling between the floating gates of the unselectd cells and the bit line of selected cell. In this paper, a new programming method to redcue significantly the drain turn-on leakage in the unselected cells during programming has been studied, where a little positive voltage (0.25-0.75V) is applied to the soruce during programming unlike the conventional programming method in which the source is grounded. The resutls of the PISCES simulations and the electrical measurements for the standard EPROM with 0.35.mu.m effective channel length and 1.0.mu.m effective channel width show that the subthreshold leakage in the unselectd cells is significantly large when the source is grounded, whereas it is negligibly small when the source is biased ot a little positive voltage during programming. On the other hadn, the positive bias on the source is found to have little effects on the programming speed of the EPROM.

• Journal of Power Electronics
• /
• 제3권4호
• /
• pp.239-248
• /
• 2003

This paper presents a novel prototype of three-phase voltage source type zero voltage soft-switching inverter with the auxiliary resonant snubbers suitable for high-power applications with IGBT power module packages in order to reduce their switching power losses as well as electromagnetic conductive and radiative noises. A proposed single inductor-assisted resonant AC link snubber circuit topology as one of some auxiliary resonant commutation snubbers developed previously to achieve the zero voltage soft-switching (ZVS) for the three-phase voltage source type sinewave PWM inverter operating under the instantaneous space voltage vector modulation is originally demonstrated as compared with the other types of resonant AC link snubber circuit topologies. In addition to this, its operation principle and unique features are described in this paper. Furthermore, the practical basic operating performances of the new conceptual instantaneous space voltage vector modulation resonant AC link snubber-assisted three-phase voltage source type soft-switching PWM inverter using IGBT power module packages are evaluated and discussed on the basis of switching voltage and current waveforms, output line to line voltage quality, power loss analysis, actual power conversion efficiency and electromagnetic conductive and radiative noises from an experimental point of view, comparing with those of conventional three-phase voltage source hard-switching PWM inverter using IGBT power modules.

• Journal of Electrical Engineering and Technology
• /
• 제6권1호
• /
• pp.1-7
• /
• 2011

This paper proposes an enhanced noise robust algorithm for fault location on double-circuit transmission line for the case of single line-to-ground (SLG) fault, which uses distributed parameter line model that also considers the mutual coupling effect. The proposed algorithm requires the voltages and currents from single-terminal data only and does not require adjacent circuit current data. The fault distance can be simply determined by solving a second-order polynomial equation, which is achieved directly through the analysis of the circuit. The algorithm, which employs the faulted phase network and zero-sequence network with source impedance involved, effectively eliminates the effect of load flow and fault resistance on the accuracy of fault location. The proposed algorithm is tested using MATLAB/Simulink under different fault locations and shows high accuracy. The uncertainty of source impedance and the measurement errors are also included in the simulation and shows that the algorithm has high robustness.

• 한국전자통신학회논문지
• /
• 제10권7호
• /
• pp.831-836
• /
• 2015

본 논문은 국제적 문자부호체계인 유니코드 체계를 기반으로 한 한글글자마디의 UTF-8부호가 회선부호기상에서 어느 정도 스크램블링이 발생하는 지를 연구하였다. 회선부호기의 ${\ldots}$ 경우를 대상으로 하였다. 이것은 ITU-T의 규격중 AMI 회선부호기에 적용되는 HDB-3 스크램블링과 관련된다. 본 논문은 스크램블링이 발생하는 문자의 코드를 분석하기 위해 문자의 원천부호화 규칙을 적용하였다. 연구결과 유니코드를 기반으로 하는 UTF-8한글글자마디부호 중에서 약 39%의 스크램블링이 발생하는 것으로 분석되었다.