• Communications for Statistical Applications and Methods
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• v.12 no.2
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• pp.473-481
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• 2005

The testing problem for sphericity structure of the covariance matrix in a multivariate normal distribution is introduced when there is a sample with 2-step monotone missing data pattern. The maximum likelihood method is described to estimate the parameters on the basis of the sample. Using these estimates, the likelihood ratio criterion for testing sphericity is derived.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.701-707
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• 2000

In this work, we propose to employ magnetostrictive sensors to develop a new non-contacting modal testing method. Specific applications are made in the modal testing of a beam in bending. The role of bias magnetic fields in measuring bending waves is addressed and an approximate analysis to explain the principle to measure bending signals is carried out. The measured modal data by the present method agree well with those by conventional methods using accelerometers.

• Geotechnical Engineering
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• v.5 no.3
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• pp.51-62
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• 1989

Prior to the centrifugal model experiments of reinforced earth retaining walls, frictional tests were performed to investigate the frictional behavior between the sand and the reinforcements. Coefficient of friction between the soil and the reinforcements was evaluated using different reinforcements, their lengths and testing methods. Two different testing methods, the direct shear and the pull-out tests, were adopted and their testing results were compared to determine which. method better represented the actual behavior In the field.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.10a
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• pp.71-78
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• 1994

The main objectives of the study may be stated as follows : \circled1 the acquisition of fundamental updated data for the assessment of aged wharf structures of pier type based on systematic static/dynamic load testing \circled2 the study of techniques and methods for field testing \circled3 realistic safety and load carrying capacity assessment based on practical reliability analysis. In this study field testing of real structure is performed and the results are compared with those of the 2D and 3D linear structural analysis. It may be seen that the practical reliability methods can be applied for the safety and capacity assessment of aged wharf structures of pier type.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.2
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• pp.21-25
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• 2011

Although many defects in PZR heater sleeve have been reported continually from operating experiences in oversea nuclear power plant, utilities get into difficulties in finding appropriate methods for diagnostics of the components due to the limited access or high radiation problems. Recently, as an alternative, diagnostics using Guided Wave Testing(GWT) are proposed and the attention of the methods has been growing gradually because of their long range inspection capability. This study is to investigate the effectiveness of GWT to detect PWSCC in welding points of PZR heater sleeve. Moreover, mode sensitivity analysis of GWT and optimal frequency for the diagnostics of PWSCC are presented by testing the mock-ups specimens that contain artificial flaws.

• Journal of the Korean Ceramic Society
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• v.45 no.12
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• pp.788-795
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• 2008

An electrolyte supported SOFC cell was tested at $800^{\circ}C$ in air for 3600 h with an applied current density of $200\;mA/cm^2$ to examine possible cathode degradation issues. A scandium- stabilized zirconia (ScSZ) with additional manganese doping (ScSZ: Mn) was used as electrolyte. A strontium and copper-doped lanthanum ferrite (LaSrCuFe) and platinum were used as cathode and quasi-anode material, respectively. The DC resistance was logged over the complete testing period. Additionally, impedance spectroscopy was used from time to time to track changes of the cell in-situ. Post-test analysis of the cell using methods like scanning electron microscopy imaging and other electrochemical testing methods allow the identification of different degradation sources. The results indicate a promising combination of electrolyte and cathode material in terms of chemical compatibility and electrical performance.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.191-194
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• 2002

The tensile properties of materials can be obtained just in accordance with conventional tensile testing methods which are described in several standards. However, the standard testing methods cannot be applicable due to the destructive testing procedure and specimen size requirement for some cases including on-service facility materials. Therefore, simple, non-destructive and advanced indentation technique was proposed. This test measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation and fracture. In this paper, the research trend of non-destructive evaluation of tensile properties using advanced indentation system and its application fields are reviewed and discussed.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1972-1975
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• 2002

A new test approach based on a supply current test method is proposed for testing open faults in bipolar logic circuits. In the approach, only the open faults are detected by the supply current test method, which are difficult to be detected by functional test methods. The effectiveness of the approach is examined experimentally on open fault detection in TTL combinational circuits. The results shows that higher fault coverage can be established by applying a small number of test input vectors of the supply current test method after test vectors of functional test methods based on stuck-at models.

• International journal of advanced smart convergence
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• v.12 no.3
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• pp.40-50
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• 2023

Blockchain is a technology designed to prevent tampering with digital documents or information, safeguarding transaction data and managing it in a structured manner. This proves beneficial in addressing issues of trust and data protection in B2B, B2C, and C2B transactions. Blockchain finds utility not only in financial transactions but also across diverse industrial sectors. This study outlines significant cases and responses that jeopardize the security of blockchain networks and cryptocurrency technology. Additionally, it analyzes safety and risk factors related to blockchain and proposes effective testing methods to preemptively counter these challenges. Furthermore, this study presents key security evaluation metrics for blockchain to ensure a balanced assessment. Additionally, it provides evaluation methods and various test case models for validating the security of blockchain and cryptocurrency transaction services, making them easily applicable to the testing process.

• Communications for Statistical Applications and Methods
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• v.7 no.2
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• pp.403-414
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• 2000

A diagnostic tool for testing homogeneity for random effects is proposed in unbalanced linear mixed model based on score statistic. The finite sample behavior of the test statistic is examined using Monte Carlo experiments examine the chi-square approximation of the test statistic under the null hypothesis.