• Structural Engineering and Mechanics
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• 제74권3호
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• pp.313-323
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• 2020

Non-destructive tests are commonly used in construction industry to access the quality and strength of concrete. However, till date there is no non-destructive testing method that can be adopted to evaluate the bond condition of reinforced concrete beams. In this regard, the presented research work details the use of ultra-sonic pulse velocity test method to evaluate the bond condition of reinforced concrete beam. A detailed experimental research was conducted by testing four identical reinforced concrete beam samples. The samples were loaded in equal increments till failure and ultra-sonic pulse velocity readings were recorded along the length of the beam element. It was observed from experimentation that as the cracks developed in the sample, the ultra-sonic wave velocity reduced for the same path length. This reduction in wave velocity was used to identify the initiation, development and propagation of internal micro-cracks along the length of reinforcement. Using the developed experimental methodology, researchers were able to identify weak spots in bond along the length of the specimen. The proposed method can be adopted by engineers to access the quality of bond for steel reinforcement in beam members. This allows engineers to carryout localized repairs thereby resulting in reduction of time, cost and labor needed for strengthening. Furthermore, the methodology to apply the proposed technique in real-world along with various challenges associated with its application have also been highlighted.

• Smart Structures and Systems
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• 제23권3호
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• pp.279-293
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• 2019

To ensure high quality data being used for data mining or feature extraction in the bridge structural health monitoring (SHM) system, a practical sensor fault diagnosis methodology has been developed based on the similarity of symmetric structure responses. First, the similarity of symmetric response is discussed using field monitoring data from different sensor types. All the sensors are initially paired and sensor faults are then detected pair by pair to achieve the multi-fault diagnosis of sensor systems. To resolve the coupling response issue between structural damage and sensor fault, the similarity for the target zone (where the studied sensor pair is located) is assessed to determine whether the localized structural damage or sensor fault results in the dissimilarity of the studied sensor pair. If the suspected sensor pair is detected with at least one sensor being faulty, field test could be implemented to support the regression analysis based on the monitoring and field test data for sensor fault isolation and reconstruction. Finally, a case study is adopted to demonstrate the effectiveness of the proposed methodology. As a result, Dasarathy's information fusion model is adopted for multi-sensor information fusion. Euclidean distance is selected as the index to assess the similarity. In conclusion, the proposed method is practical for actual engineering which ensures the reliability of further analysis based on monitoring data.

• Structural Engineering and Mechanics
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• 제76권5호
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• pp.653-661
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• 2020

The paper presents a study regarding rubber compressibility behavior. The objective is to analyze the effect of compression degree of rubber on its mechanical properties and propose a new methodology based on reverse engineering to predict compressibility degree based on uniaxial stretching test and Finite Element Analysis (FEA). In general, rubbers are considered to be almost incompressible and Poisson's ratio is close to 0.5. Since this property is intimately related to the rubber packing density, little changes in Poisson's ratio can lead to significant changes regarding mechanical behavior. The deviatory hyperelastic constants were obtained through experimental data fitting by least squares method for the most relevant constitutive models implemented in commercial software Abaqus, such as: Neo-Hooke, Mooney-Rivlin, Ogden, Yeoh and Arruda-Boyce, whereas the hydrostatic part was determined through an optimization algorithm implemented in the Abaqus environment by Python scripting. The simulation results presented great influence of the Poisson's ratio in the rubber specimen mechanical behavior mainly for high strain levels. A conventional pure volumetric compression test was also carried out in order to compare the results obtained by the proposed methodology.

• 아태비즈니스연구
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• 제14권1호
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• pp.215-229
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• 2023

Purpose - Based on the funding-horizon theory, this study aims to test the effects of cash needs and the persistence of external funding needs on firms' external financing. Design/methodology/approach - Financial data of Korean listed companies were collected from DataGuide. Immediate and near-term cash shortfalls are defined using the methodology of Haung and Ritter (2021). We estimate multinomial logit regressions for the financing choice. Findings - First, all three cash depletion variables used in our study increase the likelihood of external financing. Second, firms prefer to issue debt to meet immediate spending and equity to meet long-lived cash needs. Third, this effect is more pronounced for high R&D firms. Fourth, chaebol firms with internal capital markets defer raising external capital for immediate and near-term cash needs. Research implications or Originality - This paper provide empirical evidence that immediate and near-term cash needs induce external financing, and the persistence of cash needs affects the choice between debt and equity, the finding which is consistent with the funding-horizon theory of financing decisions. Being the first paper to test the funding-horizon theory using Korean data, this paper contributes to the literature on the capital structure of Korean firms.

• 산경연구논집
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• 제11권11호
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• pp.29-38
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• 2020

Purpose: The problem of housing poverty among young people is a very important problem for the nation. Therefore, the main purpose of this paper is to identify the problems of the government's housing support policy for young people. And it is in presenting specific solutions by fully reflecting the opinions of experts. Research design, data and methodology: This study consisted of analyzing the following three research topics: 1) the differences of youth residential support housing policy impact on young adults' housing stability, 2) the problems and solutions of youth housing support policy, and 3) the differences of experts' opinions on the impact of government policy on youth housing stability. The subject of this study is the government's seven housing policies for young people. The targets include Happy Public Rental Housing (Happiness Housing), Station Area Rental Housing for youth (Station Area 2030), Public Dormitory for College Students (Public Dormitory & Hope Dormitory), Jeonse Rental Housing for College Students (Subject Lease Rental Housing for College Students), Social Housing for Young People, and Share House. The data was organized through expert surveys from 1st to 30th June 2020. The experts surveyed include professors & researchers, public officer & public institutions staff, and private developers of young adults' housing. The methodology of analysis on the problem and the solution of government policy was Frequency analysis. And analysis methods on differences of experts' opinion were ANOVA, Levene' test, and Schefe test. Results: Problems in Government's youth residential support housing policy include high rents, lack of supply, difficulty in acquiring rental housing, inconvenience in using shared spaces, conflicts with cohabitants, and invasion of privacy. Solutions include expanding supply to urban areas, establishing long-term plans, securing privacy, diversifying business methods, establishing platforms for rental housing transactions, and expanding various public support (financial support, etc). Conclusions: There was a difference in perception among groups of experts on the impact of public rental housing (called 'happiness housing') in youth housing stability. It is very urgent to come up with the most reasonable policy to support youth housing. This requires in-depth discussions by experts to narrow their differences.

• 한국산학기술학회논문지
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• 제16권6호
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• pp.4147-4157
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• 2015

전장 환경이 변화함에 따라 무기체계에 다양한 기능이 탑재되고 있다. 이와 함께 무기체계의 이상 유무를 진단하는 무기체계점검장비 또한 이전보다 더 복잡하고 수많은 정보를 다루게 되었다. 하지만, 대부분의 무기체계점검장비는 개발자 중심으로 설계되어있다. 이 때문에, 운용자가 점검장비 디스플레이에 전시되는 정보들을 파악하여 무기체계의 이상 유무를 판단하기 쉽지 않다. 따라서, 점검장비 운용자의 인지부하를 줄이고, 무기체계의 안전한 점검을 수행할 수 있도록 무기체계점검장비 디스플레이를 개발하였다. 이를 위해 생태학적 인터페이스 디자인 기법을 적용하였다. 작업영역분석을 통해 작업영역 모델을 개발하고, 요구정보를 추출하여 무기체계점검장비 디스플레이를 개발하였다. 새로운 디스플레이의 가장 큰 장점은 사용자가 수행하는 점검과 점검장비의 상태를 직관적으로 확인할 수 있다는 것이다. 본 연구 결과로 제시된 디스플레이를 활용하여 운용자가 보다 효율적이고 안전하게 임무를 수행할 수 있을 것으로 기대한다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권2호
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• pp.105-119
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• 2012

In this paper, we have proposed a methodology which can make effective test for system integration of complex guided missile system. System integration test play a significant role in the development of weapon system, providing the means to detect and isolate faults on first linkage between sub-systems. Integration tests for domestic weapon system has executed not a technology-intensive method based on tool but labor-intensive method based on experience. Higher cost, longer period, and more resource are required to execute system integration test for complex guided missile system comparing with past weapon systems, because recently weapon systems have more complex and more networked functions. Because the proposed design method for system integration test decreases number of test case, it lead to a decrease of cost, period, and resource for integration test of weapon system. The proposed configuration for system integration test will ensure reliability through detection and isolation of fault on linkage between sub-systems.

• 한국산학기술학회논문지
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• 제10권6호
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• pp.1191-1195
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• 2009

본 논문에서는 스캔 체인의 레이아웃 거리를 고려한 효율적인 Test Wrapper 설계 방식을 제안한다. SoC내의 스캔체인들을 태스트하기 위해서는 외부 TAM 라인(line)에 각 스캔체인들을 할당해야 한다. IP 내에 존재하는 스캔체인들은 정상모드에서는 타이밍 위반(Timing Violation)이 발생하지 않도록 레이아웃이 되지만, 테스트 모드에서는 TAM 라인(line)과 연결되는 스캔체인들 간에 부가적인 레이아웃 거리를 갖게 되므로 스캔체인에서 타이밍 위반이 발생될 수 있다. 본 논문에서는 타이밍 위반이 발생하지 않도록 체인간 레이아웃거리를 고려하여 스캔체인을 할당하는 새로운 test wrapper 설계 방식을 제안하였다.

• 영어어문교육
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• 제17권4호
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• pp.123-139
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• 2011

The purpose of the current study is to analyze a model of OPIc-based speaking test for Korea English classroom. The research questions were (1). What is the English teachers' opinion on the current speaking teaching and testing? (2). Is the OPIc speaking test appropriate in the Korea English class? and (3). What are the English education students' perceptions of the OPIc-based speaking test for English classes? To answer the first research question, a survey was conducted targeting one hundred and forty-seven teachers. The result of the survey shows that Korea English teachers' great concern on the English teaching and speaking test are "communicative competence," "scoring and criteria," and "condition and need." To answer the second research question, the OPIc speaking test for the class was analyzed and it was found that in terms of the communicative competence," "scoring and criteria," and "condition and need" issues, OPIc based speaking test is appropriate in Korea English class. For the third research question, Q methodology was used targeting English education students and the result shows that most English education students strongly agree to the statements that the OPIc-based speaking test has the advantage to improve communicative competence. This study may provide the information about creating and adopting tests for English classes and relating standardized test and the English classes.

• 동아시아식생활학회지
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• 제23권6호
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• pp.799-809
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• 2013

This study was performed to determine the optimal composition of a makgeolli administered nuruk, water and Asparagus cochinchinensis. The experiment was designed base on BBD (box-behnken design), and an evaluation was carried out by means of RSM (response surface methodology), which included 15 experimental points with 3 replicates for the three independent variables nuruk, water and Asparagus cochinchinensis. The nuruk levels were tested in a range of 10~30 g, the water levels in a range 120~180% and Asparagus cochinchinensis was tested within a range of 2~6% by the weight of cooked-rice. Using the F-test, brix and appearance were expressed as a linear model, whereas the pH, acidity, DPPH radical scavenging, L-value, savory taste, taste, fresh aroma, after swallow and overall acceptability were expressed as a quadratic model. Increased amount of Asparagus cochinchinensis led to the reduction of the sensory scores for appearance, flavor, taste, texture and overall quality. The optimum formulation by numerical and graphical method were similar: nuruk 24.50 g, water 174.95% and Asparagus cochinchinensis 2.40%.