• 전자공학회논문지
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• 제53권11호
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• pp.89-96
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• 2016

잠수함 정숙화 기술의 발달로 대잠 소나의 탐지성능 향상이 요구되고 있다. 이와 같은 성능향상의 필요성에 의해 소나체계에 널리 쓰이는 일반적인 빔형성 기법(CBF : Conventional BeamForming)보다 성능이 뛰어난 적응 빔형성(ABF : Adaptive BeamForming) 기법이 대체 알고리즘으로 검토되고 있다. 소나 체계에 적응 빔형성기를 적용하여 성능향상을 도모하기 위해서는 적응 빔형성 기법의 체계 적용성이 검증되어야 하는데 이를 위해서는 체계 적용성을 측정하기 위한 성능지표가 정립되어야 한다. 본 논문에서는 적응 빔형성기와 일반적인 빔형성기의 추적 개시(Tracking initiation) 확률을 산출하여 두 기법의 성능을 정량화하여 적응 빔형성기의 체계 적용성을 검토하였다.

• 전기학회논문지
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• 제60권5호
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• pp.921-928
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• 2011

This paper presents a new method of local voltage control to achieve coordinative control among UPFC(Unified Power Flow Controller) and conventional reactive compensation equipments, such as switched-shunt and ULTC(Under-Load Tap Changing) transformer. Reactive power control has various difficult aspects to control because of difficulty of system analysis. Recently, the progress of power electronics technologies has lead to commercial availability of several FACTS(Flexible AC Transmission System) devices. The UPFC(Unified Power Flow Controller) simultaneously allows the independent control of active and reactive power flows as well as control of the voltage profile. When conventional reactive power sources and UPFC are used to control system voltage, the UPFC reacts to the voltage deviation faster than the conventional reactive power sources. Keeping reactive power reserve in an UPFC during steady-state operation is always needed to provide reactive power requirements during emergencies. Therefore, coordination control among UPFC and conventional reactive power sources is needed. This paper describe the method to keep or control the voltage of power system of local area and to manege reactive power reserve using PSS/E with Python. The result of simulation shows that the proposed method can control the local bus voltage within the given voltage limit and manege reactive power reserve.

• International Journal of Contents
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• 제11권4호
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• pp.38-43
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• 2015

Non-orthogonal multiple access (NOMA) where all users share the entire time and frequency resource has paid attention as one of the key technologies to enhance the spectral efficiency and the total throughput. Nevertheless, as the number of users and SIC error increase, the inter-user interference and the residual interference due to the SIC error also increase, resulting in performance degradation. In order to mitigate the performance degradation, we propose grouping-based NOMA system. In the proposed scheme, all users are divided into two groups based on the distance between the BS and each user, where one utilizes the first half of the bandwidth and the other utilizes the rest in the orthogonal manner. On the other hand, users in each group share the spectrum in the non-orthogonal manner. Grouping users can reduce both the inter-user interference and residual interference due to the SIC error, so it can outperform conventional NOMA system, especially in case that the number of users and the SIC error increase. Based on that, we also present the hybrid operation of the conventional and the proposed NOMA systems. In numerical results, the total throughput of the proposed NOMA systems is compared with that of the conventional NOMA systems with regard to the number of users and SIC error. It is confirmed that the proposed NOMA system outperforms the conventional NOMA system as the number of users and the SIC error increase.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 A
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• pp.205-210
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• 1992

The power flow calculations are the most important and powerful tools in the various studies of power system engineering. Newton-Raphson method, among the various power flow calculation techniques, is normally used due to its rapidness of numerical convergency. In the conventional Newton-Raphson method, however, there are some unrealistic assumptions, in which all the system power losses are considered to be supplied by the slack bus generator. Introducing the system power loss formula and augmenting the conventional Newton-Raphson power flow method, we can relieve the unrealistic assumption and improve the performance of power flow calculation. In this study, A new approach for handling the losses and augmenting the conventional power flow problem is proposed. The proposed method estimates the increamental changes of active power on each generation bus with respect to the change of total system power losses and the estimated value are used to update the slack bus power. If some studies for more theoritical investigations and verifications are followed, the proposed approach will show some improvement of the conventional method and give lots of contribution to increase the performance of power flow techniques in power systems engineering.

• 한국연초학회지
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• 제32권1호
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• pp.35-40
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• 2010

This study was carried out to enhance the analytical methods of phenolic compounds in mainstream cigarette smoke using high efficiency column and RRLC(Rapid Resolution Liquid Chromatography) system, and to compare these methods. RRLC system offers significantly faster results with higher data quality of phenolic compounds than conventional HPLC, but it is disadvantage that it is expensive. On the other hand, the method using monolithic column offers faster results by the use of conventional HPLC system without new equipment introduction. In this study, we used the linear type smoking machine and Health Canada method for pre-treatment process of phenolic compounds. The analysis time of phenolic compounds using RRLC and monolithic column was individually 8 and 15 minutes, whereas in the conventional HPLC it was 45 minutes. These new methods were accompanied with the minimal solvent consumption and had lower analysis costs. Also, we proved that there were no difference between new methods and conventional method in accuracy by statistic.

• ETRI Journal
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• 제45권6호
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• pp.996-1006
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• 2023

Renewable energy is promoted massively to overcome problems that fossil fuel power plants generate. One popular renewable energy type that offers easy installation is a photovoltaic (PV) system. However, the energy harvested through a PV system is not optimal because influenced by exposure to solar irradiance in the PV module, which is constantly changing caused by weather. The maximum power point tracking (MPPT) technique was developed to maximize the energy potential harvested from the PV system. This paper presents the MPPT technique, which is operated on a new high-gain voltage DC/DC converter that has never been tested before for the MPPT technique in PV systems. Fuzzy logic (FL) was used to operate the MPPT technique on the converter. Conventional and adaptive perturb and observe (P&O) techniques based on variables step size were also used to operate the MPPT. The performance generated by the FL algorithm outperformed conventional and variable step-size P&O. It is evident that the oscillation caused by the FL algorithm is more petite than variables step-size and conventional P&O. Furthermore, FL's tracking speed algorithm for tracking MPP is twice as fast as conventional P&O.

• 한국철도학회논문집
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• 제10권5호
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• pp.582-588
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• 2007

분기기 시스템은 기존선의 속도향상을 저해하는 요소들 중에 하나이며, 우리나라에서는 안전을 위하여 분기기 직선측 통과속도를 130km/h로 제한하고 있어 기존선 속도향상을 위해서는 반드시 개선되어야할 사항이다. 본 연구에서는 기존 및 개량 분기기 궤도 성능을 평가 기 위해 동적윤중 현장계측 데이터를 이용하여 충격계수가 산정되었으며, 수치해석을 이용하여 분기기 하부 노반의 지지력을 평가하였다. 그 결과 분기기 개선에 따른 노반응력 저감효과를 확인 할 수 있었으며, 기존 및 개량 분기기에서 발생한 노반응력은 허용지지력 이하로 나타났다.

• ETRI Journal
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• 제36권2호
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• pp.271-279
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• 2014

This paper proposes a new broadcasting system for the service-compatible 3DTV in which the 3D service can coexist with the conventional digital TV broadcast. In the proposed system, the commercial 3DTV service can be implemented via the existing DTV channel without utilizing the dedicated 3DTV system. This 2D/3D system interworks with the conventional system and can switch to 2D or 3D service according to the broadcast programming and schedule. The system also provides a mechanism that can prevent the synchronization mismatch between left and right video streams and between the stream and the associated signaling in the 2D/3D transition periods. The picture quality measurements are carried out based on the ITU-R recommended test to check the level of quality of service provided by the proposed scheme. The conformity tests are also performed with the conventional channel and the receiver for the DTV system to confirm the feasibility of the proposed one for the commercial service.

• Smart Structures and Systems
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• 제3권3호
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• pp.373-384
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• 2007

For structural health monitoring (SHM) of civil infrastructures, displacement is a good descriptor of the structural behavior under all the potential disturbances. However, it is not easy to measure displacement of civil infrastructures, since the conventional sensors need a reference point, and inaccessibility to the reference point is sometimes caused by the geographic conditions, such as a highway or river under a bridge, which makes installation of measuring devices time-consuming and costly, if not impossible. To resolve this issue, a visionbased real-time displacement measurement system using digital image processing techniques is developed. The effectiveness of the proposed system was verified by comparing the load carrying capacities of a steel-plate girder bridge obtained from the conventional sensor and the present system. Further, to simultaneously measure multiple points, a synchronized vision-based system is developed using master/slave system with wireless data communication. For the purpose of verification, the measured displacement by a synchronized vision-based system was compared with the data measured by conventional contact-type sensors, linear variable differential transformers (LVDT) from a laboratory test.

• 한국소음진동공학회논문집
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• 제18권7호
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• pp.764-774
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• 2008

A fire-out-of-battery(FOOB) mechanism, which is a new recoil technology, can reduce dramatically the level of a recoil force compared to the conventional recoil system. The FOOB mechanism pre-accelerates the recoil parts in direction opposite of conventional recoil before ignition. This momentum of the recoil parts due to pre-acceleration can reduce the firing impulse. In this paper, the dynamics of the recoil system with this FOOB mechanism is formulated and simulated numerically. The results of the simulation show that the FOOB system can reduce the recoil force and stroke compared to the conventional system under normal condition. When the fault modes happen, the FOOB system may not perform well and may be damaged seriously due to excessive recoil force and stroke. Hence, the control of the fault modes is necessary to achieve the normal operation of the FOOB system. The results that an additional MR damper enables the FOOB system to perform well under all firing condition.