• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.1
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• pp.11-19
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• 2009

A number of trend test methods, i.e., Military Handbook test and Laplace test etc., have been applied to investigate recurrent failures trend in repairable systems. Existing methods provide information about only existence of trend in the system. In this paper, we propose a new change-point test based on the Schwarz Information Criterion(SIC). The change-point approach is more informative than other trend test methods in that it provides the number of change-points and the location of change-points if it exists, as well as the existence of change-point for recurrent failures. The change-point test is applied to nine 300MW generating units operated in East China. We confirm that the change-point test has a potential for establishing optimal preventive maintenance policy by detecting change-point of failure rate.

• Computers and Concrete
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• v.32 no.5
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• pp.465-474
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• 2023

The point load test (PLT) is a widely-used alternative method in the field to determine the uniaxial compressive strength due to its simple testing machine and procedure. The point load test index can estimate the uniaxial compressive strength through conversion factors based on the rock types. However, the mechanism correlating these two parameters and the influence of the mechanical properties on PLT results are still not well understood. This study proposed a theoretical model to understand the mechanism of PLT serving as an alternative to the UCS test based on laboratory observation and literature survey. This model found that the point load test is a self-confined compression test. There is a compressive ellipsoid near the loading axis, whose dilation forms a tensile ring that provides confinement on this ellipsoid. The peak load of a point load test is linearly positive correlated to the tensile strength and negatively correlated to the Poisson ratio. The model was then verified using numerical and experimental approaches. In numerical verification, the PLT discs were simulated using flat-joint BPM of PFC3D to model the force distribution, crack propagation and BPM properties' effect with calibrated micro-parameters from laboratory UCS test and point load test of Berea sandstones. It further verified the mechanism experimentally by conducting a uniaxial compressive test, Brazilian test, and point load test on four different rocks. The findings from this study can explain the mechanism and improve the understanding of point load in determining uniaxial compressive strength.

• Communications for Statistical Applications and Methods
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• v.14 no.2
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• pp.443-457
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• 2007

This paper deals with the problem of testing the existence of change in mean and estimating the change-point using nonparametric bootstrap technique. A test statistic using Gombay and Horvath (1990)'s functional form is applied to derive a test statistic and nonparametric change-point estimator with bootstrapping idea. Achieved significance level of the test is calculated for the proposed test to show the evidence against the null hypothesis. MSE and percentiles of the bootstrap change-point estimators are given to show the distribution of the proposed estimator in simulation.

• Journal of Korean Academy of Nursing
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• v.3 no.1
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• pp.53-66
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• 1972

There is an urgent need to improve the tool predicting success or failure of academic achievement of nursing in Korea so as to identify as early as possible those students who should receive special instruction and to improve screening procedures for admission of nursing. The main purpose of this study is to identify the correlation between the grade point averages of courses learned and their psychological test characteristics in a baccalaureate nursing program. All 240 students, except freshmen, enrolled in Nursing Department of Seoul National University in the spring semester, 1972, participated in this study. All of the subjects completed the psychometric tests such as interest test, personality test and test of self-concept. Total grade point averages, grade point averages of general education subjects, of supporting science courses and of professional education subjects were used as performance criteria of the students. Through the calculation of product-moment correlation coefficients between the test scores and four grade point averages of each class and of total subjects, the following findings and recommendations were obtained. 1. There was so much variation in characteristics of interest test correlated with academic achievement of nursing students in each class. 2. Since the school objectives, curriculum and teaching strategies may affect predictive efficiency of characteristics of students'interest test, interest test must-be utilized in a homogeneous group in order to predict school achievement. 3. Characteristics of interest test positively correlated at significant level with total grade point averages of all subjects were scientific interest-biological, scientific interest-physical, and humanitarian interest. Scientific interest-physics: was the only characteristic positively correlated at significant level with total grade point averages and grade point averages of professional courses. 4. There were various patterns in characteristics of personality test correlated with school achievement of nursing students by class pattern and personality maturation as they progress toward higher classes. 5. A characteristic of personality test, responsibility, is in high positive correlation with academic achievement in the upper division of classes. 6. Responsibility was the sole personality factor positively correlated at significant level with total grade point averages and grade point averages of nursing courses in the total number of students. 7. There were very different correlation coefficients between characteristics of self-concept test and academic achievement according to the type of each class and type of courses they learned. 8. Characteristics of self-concept test positively correlated at significant level with total grade point averages and grade point averages of nursing courses of all students were physical self and row variability. Those who have positive concept on their own physical status and who are deficient in self-concept were higher in total grade point averages and grade point averages of professional courses than other students. 9. Scores of professional courses offered in freshmen and sophomore classes were in positive correlation with limited number of characteristics of psychological tests. In pursuit of a tool predicting successful academic achievement of nursing students, their G.P.A. during the junior and senior year of nursing will serve as the more reasonable criteria. 10. Junior students of this school were in higher positive correlation with many psychological factors than other classes.

• ETRI Journal
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• v.36 no.6
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• pp.942-952
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• 2014

This paper presents a novel test point insertion (TPI) method for a pseudo-random built-in self-test (BIST) to reduce the area overhead. Recently, a new TPI method for BISTs was proposed that tries to use functional flip-flops to drive control test points instead of adding extra dedicated flip-flops for driving control points. The replacement rule used in a previous work has limitations preventing some dedicated flip-flops from being replaced by functional flip-flops. This paper proposes a logic cone analysis-based TPI approach to overcome the limitations. Logic cone analysis is performed to find candidate functional flop-flops for replacing dedicated flip-flops. Experimental results indicate that the proposed method reduces the test point area overhead significantly with minimal loss of testability by replacing the dedicated flip-flops.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.6
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• pp.35-41
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• 2011

In order to design effectively the grounding system, it is very important to determine the optimum soil resistivity at the desired location of the connection to earth. This paper deals with the reasonable methods of measuring the soil resistivity where grounding electrodes are buried. The soil resistivity at three test sites with different resistivity of soil were measured as functions of the spacing between the test probes in the Wenner's four-point method and the length of test ground rod in the three-point method. In the case of the three-point method, the length of test ground rod of 2-10[m] in length was appropriate in two-layered soil structure. In the length range of 2-10[m], the results measured by the three-point method using the test ground rod with the length corresponding to the spacing between the test probes of the Wenner's four-point method are in good agreement with the data obtained from the Wenner's four-point method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.5
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• pp.434-445
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• 1990

Protocol testing techniques are expanded from the traditional simple function- testing based on the OSI model, to sophisticated performance testing, conformance testing and interoperability testing. In addition, both point-to-point and point-to-multipoint protocols are to be covered. This paper presents a new multiple-purpose protocol test system where the common platform includes the test sequence generation and test result analysis, and the modular test execution part is selectively adjusted according to the test purposes and protocols under test. This paper describes test system for network routing protocol and test system for transport protocol, designed upon the ideas of the multiple-purpose protocol test system.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.3
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• pp.375-386
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• 2024

Autonomous weapon systems act according to artificial intelligence-based judgement based on recognition through various sensors. Test and evaluation for various scenarios is required depending on the characteristics that artificial intelligence-based judgement is made. As a part of this approach, this paper proposed a LiDAR point cloud augmentation method for mixed-reality based test and evaluation. The augmentation process is achieved by mixing real and virtual LiDAR signals based on the virtual LiDAR synchronized with the pose of the autonomous weapon system. For realistic augmentation of test and evaluation purposes, appropriate intensity values were inserted when generating a point cloud of a virtual object and its validity was verified. In addition, when mixing the generated point cloud of the virtual object with the real point cloud, the proposed method enhances realism by considering the occlusion phenomenon caused by the insertion of the virtual object.

• The Korean Journal of Applied Statistics
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• v.13 no.2
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• pp.515-523
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• 2000

In this paper we detect edges using stutistical methods of the change-point problem. For this, we perform the hypothesis testing for differences in gray levels to see whether any $n\timesn$ subimage contains edge segments. The proposed method based on the twosample Kolmogorov-Smirnov test is introduced and the likelihood ratio test and the \VolfeSchechtman test for change-point problem arc also applied for edge detection. \Ve perform the experimental study to assess the performance of these methods in both noisy and uncontaminated sample noises.

• 한국데이터정보과학회:학술대회논문집
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• 2004.10a
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• pp.25-32
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• 2004

In this study, we use various change-point detection methods to detects Korea economic crisis of 1997, and then compares their performance. In change-point detection method, there are three major categories: (1) the parametric approach, (2) the nonparametric approach, and (3) the model-based approach. Through the application to Korea foreign exchange rate during her economic crisis, we compare the employed change-point detection methods and, furthermore, determine which of them performs better.