• Computers and Concrete
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• 제29권1호
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• pp.31-45
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• 2022

Experimental and numerical simulation were used to investigate the effects of angle and number of T shape non-persistent crack on the shear behaviour of crack's bridge area under uniaxial compressive test. concrete samples with dimension of 150 mm×150 mm×40 mm were prepared. Within the specimen, T shape non-persistent notches were provided. 16 different configuration systems were prepared for T shape non-persistent crack based on two and three cracks. In these configurations, the length of cracks were taken as 4 cm and 2 cm based on the cracks configuration systems. The angle of larger crack related to horizontal axis was 0°, 30°, 60° and 90°. Similar to cracks configuration systems in the experimental tests, 28 models with different T shape non-persistent crack angle were prepared in numerical model. The length of cracks were taken as 4 cm and 2 cm based on the cracks configuration systems. The angle of larger crack related to horizontal axis was 0°, 15°, 30°, 45°, 60°, 75° and 90°. Tensile strength of concrete was 1 MPa. The axial load was applied to the model. Displacement loading rate was controlled to 0.005 mm/s. Results indicated that the failure process was significantly controled by the T shape non-persistent crack angle and crack number. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. Furthermore, it was shown that the compressive behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the crack number and crack angle. The strength of samples decreased by increasing the crack number. In addition, the failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods (PFC2D).

• 한국환경복원기술학회지
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• 제12권2호
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• pp.73-82
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• 2009

The traffic volume of Seoul is extremely high in comparison to other major cities in Korea, and the result has been harmful physical and mental exposure to pollution by Seoulites on a regular basis. The street air pollution is more important than the others, because the air pollution generated by street traffic directly impacts the health of nearby pedestrians. This problem requires urgent attention and resolution. Among the factors creating the air pollution originating from the street, is the configuration of streets, which have emerged as the most significant because it is related to air and pollutant dispersion. Therefore, this study was conducted under the assumption that street form affects the air quality. Study sites were classified by street characteristics, and air quality was analyzed in each class. Then the OSPM (Operational Street Pollution Model) was employed to simulate the relationship between street configuration and air quality of streets within the old city center and new city center in Seoul. After that this study analyzed the correlation between air pollution and the spatial configuration of urban streets (ex. street width, building height, building density, etc.) to determine their contributions to air pollution. The outcome of this study is as follows : First, the result that was derived from the correlation analysis between street configuration and air quality hewed that the air pollution of the street is influenced by the average height of building, width of the roads as well as traffic volume. On the roadside, the concentration level of $NO_2$ is mainly affected by the average height of building and the deviation of building height along the street and CO is affected by street width. The outcome of this study can be used as a basis for more sound urban design policies, and the promotion of desirable street environments for pedestrians.

• Steel and Composite Structures
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• 제19권4호
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• pp.877-895
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• 2015

Connections to circular hollow steel sections (CHS) are considered one of the most complex and time consuming connections in steel construction. Such connections are usually composed of gusset plates welded to the outside of the steel tube or penetrating the steel tube. Design guides, accounting for the effect of connection configuration on the strength of the connection, are not present. This study aims to investigate, through experimental testing and a parametric study, the influence of connection configuration on the strength of one sided branch plate-to-CHS members. A notable effect was observed on the behavior of the connections due to its detailing changes with respect to capacity, failure mode, ductility, and stress distribution. A parametric study is performed using the calibrated analytical model to include a wider range of parameters. The study involves 26 numerical analyses of finite element models including parameters of the diameter-to-thickness (D/t) ratio, length of gusset plate, and connection configuration. Accordingly, a modification to the formulas provided by the current design recommendations was suggested to include connection configuration effects for the one sided branch plate-to-CHS members.

• 한국세라믹학회지
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• 제48권6호
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• pp.493-498
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• 2011

Optimal atomic configurations in a nanoparticle were predicted by genetic algorithm. A truncated octahedron with a fixed composition of 1 : 1 was investigated as a model system. A Python code for genetic algorithm linked with a molecular dynamics method was developed. Various operators were implemented to accelerate the optimization of atomic configuration for a given composition and a given morphology of a nanoparticle. The combination of random mix as a crossover operator and total_inversion as a mutation operator showed the most stable structure within the shortest calculation time. Pt-Ag core-shell structure was predicted as the most stable structure for a nanoparticle of approximately 4 nm in diameter. The calculation results in this study led to successful prediction of the atomic configuration of nanoparticle, the size of which is comparable to that of practical nanoparticls for the application to the nanocatalyst.

• 한국항공우주학회지
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• 제33권9호
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• pp.9-15
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• 2005

국방과학연구소 풍동실험실에서는 회전익 항공기 개발에 소요되는 관련 풍동시험 기법의 확립과 형상연구 관련 시험자료의 확보를 위한 실험적 연구를 수행하였다. 본 연구는 회전익 항공기 동체구성품의 형상조합에 따른 항력증분과 안정성 평가를 위한 공기역학적 특성의 추출을 목적으로 하였으며, 풍동시험에는 모듈화된 1:8 축척의 회전익 항공기 동체형상과 500 rpm으로 회전하는 로터허브의 부분모형이 사용되었다. 시험결과들을 기존의 유사 항공기 시험결과들과 비교하였으며, 기존 연구결과들과 잘 부합됨을 확인하였다.

• 조명전기설비학회논문지
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• 제28권12호
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• pp.74-83
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• 2014

This paper proposes a study on the configuration of balancing of plant(BOP) and implementation of battery management system(BMS) functions for vanadium redox flow battery(VRFB) and propose a method consists of sensor and required design specifications BOP system configuration. And it proposes an method of the functions implementation and control algorithm of the BMS for flow battery. Functions of BMS include temperature control, the charge and discharge control, flow control, level control, state of charge(SOC) estimation and a battery protection through the sensor signal of BOP. Functions of BMS is implemented by the sensor signal, so it is recognized as a very important factor measurement accuracy of the data. Therefore, measuring a mechanical signal(flow rate, temperature, level) through the BOP test model, and the measuring an electrical signal(cell voltage, stack voltage and stack current) through the VRFB charge-discharge system and analyzes the precision of data in this paper. Also it shows a good charge-discharge test results by the SOC estimation algorithm of VRFB. Proposed BOP configuration and BMS functions implementation can be used as a reference indicator for VRFB system design.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.97-104
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• 2005

Vision-based lane sensing systems require accurate and robust sensing performance in lane detection. Besides, there exists trade-off between the computational burden and processor cost, which should be considered for implementing the systems in passenger cars. In this paper, a stereo vision-based lane detection system is developed with considering sensor configuration aspects. An inverse perspective mapping method is formulated based on the relative correspondence between the left and right cameras so that the 3-dimensional road geometry can be reconstructed in a robust manner. A new monitoring model for estimating the road geometry parameters is constructed to reduce the number of the measured signals. The selection of the sensor configuration and specifications is investigated by utilizing the characteristics of standard highways. Based on the sensor configurations, it is shown that appropriate sensing region on the camera image coordinate can be determined. The proposed system is implemented on a passenger car and verified experimentally.

• 전력전자학회논문지
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• 제19권1호
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• pp.31-40
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• 2014

This paper describes an optimal configuration for multi-central inverters in a medium-voltage (MV) grid, which is suitable for large-scale photovoltaic (PV) power plants. We theoretically analyze a proposed common-mode equivalent model for problems associated with multi-central transformerless-type three-phase full bridge(3-FB) PV inverters employing two-winding MV transformers. We propose a synchronized PWM control strategy to effectively reduce the common-mode voltages that may simultaneously occur. In addition, we propose that the existing 3-FB topology may also have the configuration of a multi-central inverter with a two-winding MV transformer by making a simple circuit modification. Simulation and experimental results of three 350kW PV inverters in a multi-central configuration verify the effectiveness of the proposed synchronization control strategy. The modified transformerless-type 3-FB topology for a multi-central PV inverter configuration is verified using an experimental prototype of a 100kW PV inverter.

• 한국신뢰성학회지:신뢰성응용연구
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• 제14권4호
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• pp.225-229
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• 2014

A one-shot device is defined as a product, system, weapon, or equipment that can be used only once. After use, the device is destroyed or must undergo extensive rebuild. Determining the reliability of a one-shot device poses a unique challenge to the manufacturers and users due to the destructive nature and costs of the testing. This paper presents a reliability growth prediction for a one-shot system. It is assumed that 1) test duration is discrete(i.e. trials or rounds); 2) trials are statistically independent; 3) the number of failures for a given system configuration is distributed according to a binomial distribution; and 4) the cumulative expected number of failures through any sequence of configurations is given by AMSAA model. When the system development is represented by three configurations and the number of trials and failures during configurations are given, the AMSAA model parameters and reliability at configuration 3 are estimated by using a reliability growth analysis software. Further, if the reliability growth predictions do not meet the target reliability, the sample size of an additional test is determined for achieving the target reliability.

• 대한기계학회논문집B
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• 제33권7호
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• pp.541-551
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• 2009

Configuration of the inlet transition square duct (hereinafter referred to as "transition duct") for heat recovery steam generator (hereinafter referred to as "HRSG") in combined cycle power plant is limited by the construction type of HRSG and plant site condition. The main purpose of the present study is to analyze the effect of a variation in turbulent flow pattern by roof slop angle change of transition duct for horizontal HRSG, which is influencing heat flux in heat transfer structure to the finned tube bank. In this study, a computational fluid dynamics(CFD) is applied to predict turbulent flow pattern and comparisons are made to 1/12th scale cold model test data for verification. Re-normalization group theory (RNG) based k-$\epsilon$ turbulent model, which improves the accuracy for rapidly strained flow and swirling flow in comparison with standard k-$\epsilon$ model, is used for the results cited in this study. To reduce the amount of computer resources required for modeling the finned tube bank, a porous media model is used.