• Computers and Concrete
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• 제12권6호
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• pp.785-802
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• 2013

Ready-mixed soil material, known as a kind of controlled low-strength material, is a new way of soil cement combination. It can be used as backfill materials. In this paper, artificial neural network and nonlinear regression approach were applied to predict the compressive strength of ready-mixed soil material containing Portland cement, slag, sand, and soil in mixture. The data used for analyzing were obtained from our testing program. In the experiment, we carried out a mix design with three proportions of sand to soil (e.g., 6:4, 5:5, and 4:6). In addition, blast furnace slag partially replaced cement to improve workability, whereas the water-to-binder ratio was fixed. Testing was conducted on samples to estimate its engineering properties as per ASTM such as flowability, strength, and pulse velocity. Based on testing data, the empirical pulse velocity-strength correlation was established by regression method. Next, three topologies of neural network were developed to predict the strength, namely ANN-I, ANN-II, and ANN-III. The first two models are back-propagation feed-forward networks, and the other one is radial basis neural network. The results show that the compressive strength of ready-mixed soil material can be well-predicted from neural networks. Among all currently proposed neural network models, the ANN-I gives the best prediction because it is closest to the actual strength. Moreover, considering combination of pulse velocity and other factors, viz. curing time, and material contents in mixture, the proposed neural networks offer better evaluation than interpolated from pulse velocity only.

• 비파괴검사학회지
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• 제22권2호
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• pp.177-186
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• 2002

본 논문에서는 3차원 형태의 결함을 가진 지하매설 가스관에서 누설자속(magnetic flux leakage, MFL) 탐상 법을 사용한 결함 검출에 관하여 연구하였다. 영구자석과 요크로 구성된 자기 시스템을 유한요소법을 사용하여 해석하고 동작점을 설정하였다. 가스관이 충분히 포화되지 않은 경우에는 측정이 곤란하며, 과대포화 된 경우에는 결함에 의한 누설자속의 변화량이 적어서 측정이 곤란하므로 적정한 값을 설정하여야 하므로 자기 시스템의 동작점은 결함이 있을 때 누설자속 증가율이 최대가 되도록 설정하여야 한다. 본 논문에서는 3차원 비선형 유한요소법을 사용하여, 가스관에 결함이 있는 경우 결합의 크기, 깊이에 따른 결함신호를 예측하여 그 결과 가스관 포화상태의 적절여부, 홀 센서 range 및 resolution의 적정도 등을 연구하였다. 또한 홀 센서의 민감도 형장을 위하여 back-yoke를 사용하여 측정신호를 향상시키는 방법을 제안하였다.

• 비파괴검사학회지
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• 제14권3호
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• pp.172-176
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• 1994

핀-핑거형 터빈 동익 루트의 사각 초음파탐상에서의 기하신호가 해석된다. 동익루트의 기하가 설명되고, 기하신호가 형성되기 위한 반사조건들이 제시된다. 그리고, 이 기하신호의 빔경로에 관한 일반식들이 유도되고 검증된다. 이 기하신호는 리가먼트 모서리 신호이며, 그 위치와 진폭은 핀홀과 리가먼트의 크기 및 탐촉자의 빔지향 특성으로부터 결정될 수 있다는 것이 보여진다.

• 대한물리의학회지
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• 제18권2호
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• pp.49-59
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• 2023

PURPOSE: This study examined the relationship between lumbar instability and shortening of the iliopsoas muscles in patients with chronic low back pain. METHODS: Forty-nine patients with chronic low back pain participated in this study. The modified Thomas test was used to examine the shortening state of the iliopsoas muscle. The length of the iliopsoas muscle was measured using the hip flexion angle, and those with a flexion angle of 10° or more were classified as positive. Five subtests were used for the lumbar instability test: testing for prone lumbar instability, passive lumbar extension, anterior-posterior mobility, passive straight leg raise, and age. Those who tested positive for at least three of these tests were classified as positive for the lumbar segment instability test. RESULTS: There was a significant association between the results of the lumbar instability test and the shortening of the iliopsoas test (p < .05). After analyzing the association between the iliopsoas length test and the five lumbar instability subtests, the results of the prone lumbar instability test (p < .001) and the anterior-posterior mobility test (p < .05) showed a significant association with the iliopsoas length test. CONCLUSION: The association between lumbar instability and shortening of the iliopsoas muscles was examined in 49 patients with chronic low back pain. Patients with shortened iliopsoas muscles tested positive in the lumbar instability tests more often. Hence, the length test of the iliopsoas muscle can be used to determine lumbar instability in patients with chronic low back pain.

• 정보보호학회논문지
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• 제22권5호
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• pp.1191-1204
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• 2012

정보보안시스템을 무력화하는 공격이 나타남에 따라, 정보보안제품의 취약성을 분석하는 보안 테스팅에 대한 관심이 높아지고 있다. 보안제품 개발의 주요 단계인 침투 테스팅은, 공격자가 악용할 수 있는 취약성을 찾기 위해 컴퓨터 시스템을 실제적으로 테스팅하는 것이다. 침투 테스팅과 같은 보안 테스팅은 대상 시스템에 대한 정보 수집, 가능한 진입점 식별, 침입 시도, 결과 보고 등의 과정을 포함한다. 따라서 취약성 분석 및 보안 테스팅에서 일반성, 재사용성, 효율성을 극대화하는 것이 매우 중요하다. 본 논문에서는, 정보보호제품이 자신의 보안 기능을 무력화하거나 우회하는 공격에 대응할 수 있는 자체보호기능 및 우회불가성을 제공하는 가를 평가할 수 있는 위협분석 기반의 소프트웨어 보안 테스팅을 제안한다. 위협분석으로 취약성을 식별한 후, 보안 테스팅의 재사용성과 효율성을 개선하기 위해 소프트웨어 모듈과 보안 기능에 따라 테스팅 전략을 수립한다. 제안기법은 위협 분석 및 테스팅 분류, 적절한 보안테스팅 전략 선정, 보안 테스팅으로 구성된다. 사례연구와 보안테스팅을 통해 제안 기법이 보안 시스템을 체계적으로 평가할 수 있음을 보였다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권2호
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• pp.142-145
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• 2005

The life expectancy of a transformer largely depends on the temperature-rise it experiences. If the temperature-rise exceeds limits specified in the design standards, the aging of insulating materials is accelerated and the capability of the cooling medium is deteriorated. Consequently, applicable limits for the temperature-rise are essential in designing the transformer and the coolers, demanding the estimation of the transformer's thermal behavior. In order to analyze the temperature characteristics of the transformer, numerical analysis by way of the commercial CFD code has been carried out, and temperature-rise testing to verify computed results was performed. The results obtained in this study show that there is a good agreement between computed outcomes and experimental outcomes.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.538-547
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• 2005

This paper presents the shaking table testing method, only using building specimen as an experimental part taking into account the dynamic soil-structure interaction based on the substructure method. The Parmelee's soil stiffness is used as an assumed soil model in here. The proposed methodologies are summarized as: (1) Acceleration feedback method is the one that the shaking table is driven by the motion, corresponding to the acceleration at foundation of the total SSI system. This is found by observing the fed-back accelerations of superstructure and using the interaction force based on the acceleration formulation. (2) Velocity feedback method is the one that the shaking table is driven by the motion, corresponding to the velocity at foundation of the total SSI system. This is found by observing the fed-back accelerations of superstructure and using the interaction force based on the velocity formulation. The applicability of the proposed methodologies to the shaking table test is investigated and experimentally verified in this paper.

• 대한수학회지
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• 제47권2호
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• pp.385-407
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• 2010

To study the relationship between the levels of chemical pollutants and the number of daily total hospital admissions for respiratory diseases and to find the effect of temperature/relative humidity on the admission number, Wong et al. [17] introduced the varying-coefficient single-index model (VCSIM). As pointed out, it is a popular multivariate nonparametric fitting technique. However, the tests of the model have not been very well developed. In this paper, based on the estimators obtained by the local linear technique, the average method and the one-step back-fitting technique in the VCSIM, the generalized likelihood ratio (GLR) tests for varying-coefficient parts on the VCSIM are established. Under the null hypotheses the new proposed GLR tests follow the $\chi^2$-distribution asymptotically with scale constant and degree of freedom independent of the nuisance parameters, known as Wilks phenomenon. Simulations are conducted to evaluate the test procedure empirically. A real example is used to illustrate the performance of the testing approach.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2001년도 학술발표회 발표논문집
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• pp.59-64
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• 2001

The objectives of the thesis are to propose a pattern classification method for remote sensing data using artificial neural network. First, we apply the error back propagation algorithm to classify the remote sensing data. In this case, the classification performance depends on a training data set. Using the training data set and the error back propagation algorithm, a layered neural network is trained such that the training pattern are classified with a specified accuracy. After training the neural network, some pixels are deleted from the original training data set if they are incorrectly classified and a new training data set is built up. Once training is complete, a testing data set is classified by using the trained neural network. The classification results of Landsat TM data show that this approach produces excellent results which are more realistic and noiseless compared with a conventional Bayesian method.

• 대한전기학회논문지
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• 제43권2호
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• pp.278-285
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• 1994

Aging test was done by loading back method for 20kVA amorphous core transformers manufactured by Hyosung Industries Co. and korea Electric Power Corporation. Iron losses, copper losses and insulation oil temperatures of the transfromers was measured for all the testing period. Expected life of amorphous core transformers on the basis of the degradation of the insulators was 46 years at 100% load, and 2.4 years at 130% load. Average temperature rising of transformer oil of amorphous core transformers was higher than that of silicon steel core transformers. Hence lowering the oil temperature by optimized design is needed for improving the expected life of the amorphous transformers.