• Journal of Power Electronics
• /
• 제19권5호
• /
• pp.1259-1269
• /
• 2019

PV system performance is dependent on different irradiations and temperature values in addition to the capability of the employed PV inverter / maximum power point tracker (MPPT) circuit or algorithm. Therefore, it would be appropriate to use a PV simulator capable of producing identical repeatable conditions regardless of the weather to evaluate the performance of inverter / MPPT circuits and algorithms. In accordance with this purpose, a photovoltaic (PV) array simulator is presented in this paper. The simulator is designed to generate current-voltage (I-V) and power-voltage (P-V) curves of a PV panel. Series connected cascaded modules constitute the basic part of the simulator. This feature also allows for the modeling of PV arrays since the number of modules can be increased and high voltage values can be reached with the simulator. In addition, the curves obtained at the simulator output become similar to the actual curves of sample PV panels with an increase in the number of modules. In order to show the validity of the proposed simulator, it was simulated for various situations such as panels under full irradiance and partial shading conditions. After completing simulations, experiments were realized to support the simulation study. Both simulation and experimental results show that the proposed simulator will be very useful for researchers to carry out PV studies under laboratory conditions.

• Geomechanics and Engineering
• /
• 제16권6호
• /
• pp.619-626
• /
• 2018

A simple prediction procedure was investigated for calculating the stresses and displacements of a circular opening. Unlike existed approaches, the proposed approach starts each step with a radius increment. The stress for each annulus could be obtained analytically, while strain increments for each step can be determinate numerically from the compatility equation by finite difference approximation, flow rule and Hooke's law. In the successive manner, the distributions of stresses and displacements could be found. It should be noted that the finial radial stress and displacement were equal to the internal supporting pressure and deformation at the tunnel wall, respectively. By assuming different plastic radii, GRC and the evolution curve of plastic radii and internal supporting pressures could be obtained conveniently. Then the real plastic radius can be calculated by using linear interpolation in the evolution curve. Some numerical and engineering examples were performed to demonstrate the accuracy and validity for the proposed procedure. The comparisons results show that the proposed procedure was faster than that in Lee and Pietrucszczak (2008). The influence of annulus number and dilation on the accuracy of solutions was also investigated. Results show that the larger the annulus number was, the more accurate the solutions were. Solutions in Park et al. (2008) were significantly influenced by dilation.

• Nuclear Engineering and Technology
• /
• 제51권7호
• /
• pp.1729-1737
• /
• 2019

This paper presents neutronics design of VVER-1000 fuel assembly using burnable poison particles (BPPs) for controlling excess reactivity and pin-wise power distribution. The advantage of using BPPs is that the thermal conductivity of BPP-dispersed fuel pin could be improved. Numerical calculations have been conducted for optimizing the BPP parameters using the MVP code and the JENDL-3.3 data library. The results show that by using $Gd_2O_3$ particles with the diameter of $60{\mu}m$ and the packing fraction of 5%, the burnup reactivity curve and pin-wise power distribution are obtained approximately that of the reference design. To minimize power peaking factor (PPF), total BP amount has been distributed in a larger number of fuel rods. Optimization has been conducted for the number of BPP-dispersed rods, their distribution, BPP diameter and packing fraction. Two models of assembly consisting of 18 BPP-dispersed rods have been selected. The diameter of $300{\mu}m$ and the packing fraction of 3.33% were determined so that the burnup reactivity curve is approximate that of the reference one, while the PPF can be decreased from 1.167 to 1.105 and 1.113, respectively. Application of BPPs for compensating the reduction of soluble boron content to 50% and 0% is also investigated.

• 정보보호학회논문지
• /
• 제17권3호
• /
• pp.81-90
• /
• 2007

3G 이동 통신 기술 중 하나인 UMTS(Universal Mobile Telecommunications System)에서는 무선 구간의 안전한 통신을 위해 UMTS AKA(Authentication and Key Agreement) 프로토콜을 사용한다. 그러나 이 프로토콜은 SN(Serving Network)과 HN(Home Network)의 네트워크 대역폭 소모 문제, SQN(SeQuence Number) 동기화 문제 등 여러 가지 문제점이 제기되었다. 본 논문에서는 UMTS AKA 프로토콜의 문제점을 개선한 새로운 타원곡선 기반 UMTS AKA 프로토콜을 제안한다. 제안하는 프로토콜은 IMSI(International Mobile Subscriber Identity)의 노출로 인한 문제점으로부터 프라이버시 보호를 강화하고, ECDH(Elliptic Curve Diffie Hellman) 기법을 통해 완전한 전방향 안전성을 제공한다.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2021년도 학술발표회
• /
• pp.141-141
• /
• 2021

This study proposed an equation for Rainfall Threshold for Flood Warning (RTFW) for urban areas based on computer simulations. First, a coupled 1D-2D dual-drainage model was developed for nine watersheds in Seoul, Korea. Next, the model simulation was repeated for a total of 540 combinations of the synthetic rainfall events and watershed imperviousness (9 watersheds × 4 NRCS Curve Number (CN) values × 15 rainfall events). Then, the results of the 101 simulations with the critical flooded depth (0.25m-0.35m) were used to develop the equation that relates the value of RTFW to the rainfall event temporal variability (represented as coefficient of variation) and the watershed Curve Number. The results suggest that 1) the rainfall with greater temporal variability causes critical floods with less amount of total rainfall; and that 2) the greater imperviousness requires less rainfall to have critical floods. For validation, the proposed equation was applied for the flood warning system with two storm events occurred in 2010 and 2011 over 239 watersheds in Seoul. The results of the application showed high performance of the warning system in issuing the flood warning, with the hit, false and missed alarm rates at 68%, 32% and 7.4% respectively for the 2010 event and 49%, 51% and 10.7% for the event in 2011.

• Journal of Medicine and Life Science
• /
• 제20권3호
• /
• pp.107-114
• /
• 2023

Epidemiological control of coronavirus disease 2019 (COVID-19) is needed to estimate the infection period of confirmed cases and identify potential cases. The present study, targeting confirmed cases for which the time of COVID-19 symptom onset was disclosed, aimed to investigate the relationship between intervals (day) from symptom onset to testing the cycle threshold (CT) values of real-time reverse transcription-polymerase chain reaction. Of the COVID-19 confirmed cases, those for which the date of suspected symptom onset in the epidemiological investigation was specifically disclosed were included in this study. Interval was defined as the number of days from symptom onset (as disclosed by the patient) to specimen collection for testing. A locally weighted regression smoothing (LOWESS) curve was applied, with intervals as explanatory variables and CT values (CTR for RdRp gene and CTE for E gene) as outcome variables. After finding its non-linear relationship, a polynomial regression model was applied to estimate the 95% confidence interval values of CTR and CTE by interval. The application of LOWESS in 331 patients identified a U-shaped curve relationship between the CTR and CTE values according to the number of interval days, and both CTR and CTE satisfied the quadratic model for interval days. Active application of these results to epidemiological investigations would minimize the chance of failing to identify individuals who are in contact with COVID-19 confirmed cases, thereby reducing the potential transmission of the virus to local communities.

• 에너지공학
• /
• 제29권3호
• /
• pp.74-85
• /
• 2020

본 논문은 PEVs가 배전계통 모선에 연계되었을 때 PEVs 보급 시나리오별로 PEVs 일간 충전 패턴에 따라 배전계통 모선별 PEVs 충전 일부하곡선을 산정하여 배전계통 모선별 과부하 영향 평가를 하기 위한 알고리즘을 제시하였다. 제안한 알고리즘은 첫째 배전계통 모선별 가구 수 산출을 위한 PEVs 대수 산출, 둘째 PEVs 운행 특성을 고려한 PEVs 충전시작시간 확률밀도 함수 산출, 셋째 PEVs 보급시나리오별로 배터리 특성을 반영한 해당 모선별 PEVs 충전 일부하곡선을 산출하였다. 넷째 산출된 해당 모선별 PEVs 충전 일부하곡선과 기존 일부 하곡선을 합산하여 PEVs 보급시나리오별로 해당 모선의 과부하 영향 평가를 시행하였다. 추가로 제안된 알고리즘에 대해 배전계통 모선별 과부하 영향 평가 검증을 위해 한국 동탄 신도시의 배전계통 회선의 해당 모선(아파트, 단독주택 지역)을 대상으로 사례 검토를 실시하였다.

• 전자공학회논문지T
• /
• 제36T권4호
• /
• pp.1-8
• /
• 1999

본 논문에서는 2차원 물체영상으로부터 면을 분할하고 분할된 면의 형태에 대한 정보를 추출하는 새로운 면 분할 및 표현 알고리즘을 제안한다. 본 논문에서 사용된 signature기법은 물체나 면의 중심을 구하고 중심점으로부터 반시계방향으로 360도 회전하면서 중심점과 경계선까지의 거리 D를 회전각도 ${\theta}$의 함수로 표현하는 방법으로, 물체영상에 적용했을 때 면의 위치에 따라 signature영역에서 하나의 회전각도에 대응하여 2개 이상의 거리값을 갖는 구간들이 존재하게 되며, 이들 거리값들은 각 구간 내에서 면의 개수 만큼의 폐곡선을 형성한다. 이와 같은 특징을 이용하여 면을 분할할 수 있으며, 분할된 면으로부터 꼭지점의 수, 모서리의 수, 오목특성 등과 같은 면의 특성을 얻을 수 있다. 제안된 알고리즘은 면의 일부분이 손실된 경우에도 curve fitting방법을 적용하여 손실된 부분을 용이하게 복구할 수 있다는 장점을 갖는다.

• 한국ITS학회 논문지
• /
• 제7권2호
• /
• pp.100-109
• /
• 2008

야간 교통사고는 도로 조명이 적절하지 못할 때 증가되는 경향이 있고, 차량이 도로 밖으로 이탈하는 사고는 시선유도 시설의 부재로 인한 대표적인 사고의 유형이라 할 수 있다. 곡선부의 교통사고와 인적피해를 줄이기 위해 운전자의 안전운행을 유도하고 교통소통 증진과 도로상의 안전을 도모하는 도로안전시설의 설치가 시급한 실정이다. 이에 교통량이 상대적으로 적은 지방부 도로에 대한 도로조명 설치와 같은 과다한 지출을 줄이고 오히려 비용 절감효과는 물론 시설물 설치가 용이한 시선유도시설(Delineators)의 설치기준이 요구되어진다. 곡선부에서 운전자의 시선을 유도하기 위한 시설은 시선유도표지(Delineator), 갈매기표지(Chevron Alignment Sign), 표지병(Raised Pavement Marker)이 널리 사용되고 있다. 본 연구에서는 곡선부의 선형 변화에 대한 정보를 가장 효율적으로 전달하는 시설물인 갈매기표지와 차량의 차로이탈 및 차로침범 예방시설물인 표지병을 대상으로 설치기준에 대해 검토하고 운전자의 시각행태 및 차로침범을 고려하여 안전하고 효율적인 설치기준을 제시하였다.

• 대한기계학회논문집A
• /
• 제21권12호
• /
• pp.1992-2007
• /
• 1997

A new algorithm for planning a collision-free path is developed based on linear prametric curve. In this paper robot is assumed to a point, and two linear parametric curve is used to construct a path connecting start and goal point, in which single intermediate connection point between start and goal point is considered. The intermediate connection point is set in polar coordinate(${\theta}{\delta}$) , and the interference between path and obstacle is mapped into CPS(connection point space), which is defined a CWS GM(circular work space geometry mapping). GM of all obstacles in workspace creates overlapping images of obstacle in CPS(Connection Point Space). The GM for all obstacles produces overlapping images of obstacle in CPS. The empty area of CPS that is not occupied by obstacle images represents collision-free paths in Euclidian Space. A GM based on connection point in elliptic coordinate(${\theta}{\delta}$) is also developed in that the total length of path is depend only on the variable .delta.. Hence in EWS GM(elliptic work space geometry mapping), increasing .delta. and finding the value of .delta. for collision-free path, the shortest path can be searched without carring out whole GM. The GM of obstacles expersses all possible collision-free path as empty spaces in CPS. If there is no empty space available in CPS, it indicates that path planning is not possible with given number of connection points, i.e. path planning is failed, and it is necessary to increase the number of connection point. A general case collision-free path planning is possible by appling GM to configuration space obstacles. Simulation of GM of obstacles in Euclidian space is carried out to measure performance of algorithm and the resulting obstacle images are reported.