• Journal of the Korean Society for Heat Treatment
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• v.11 no.4
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• pp.283-294
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• 1998

This paper presents an investigation why Mn-steel high pressure gas cylinders have been failed in service. The fractured cylinders have been collected to identify the reason of the failure using various methods. The undamaged, new cylinder has also been tested for the base data. We examined the chemical compositions and fracture facets as well as the mechanical properties of the vessels. The microstructural observations of the fractured regions of the cylinder did not indicate the noticeable defects which might cause the failure. The experiments of cylinders on the compositinal and mechanical tests showed that the cylinder was in good shape according the standards of gas pressure vessel. The morphological analysis of the fracture surfaces concluded that the origin of the failure was the local weak segments induced by the external impact to the cylinder, which result in a sudden, fast fracture.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.4
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• pp.297-305
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• 1997

The experimental study by use of SPCP was fulfilled to remove toluene emitted from various industrial processes. First of all, discharge characteristic was experimented as the change of applied voltage and frequency. Then toluene removal characteristic was tested with the analysis of by-products. As a result, optimum electrical discharge condition was from 20.0 kHz to 25.0 kHz of frequency and from 3.5 kV to 4.0 kV of voltage range. The variation of applied voltage had a more important effect on the removal characteristic of toluene than the frequency variation. The toluene removal efficiency was proportioned to ozone concentration and retention time on discharge plate. It was dropped as increase of toluene concentration, but total treated volume of tolene per power consumption was high. The decomposed toluene was transformed to $CO, CO_2$ and particulates, and the rate of transformation to particulates was higher than CO and $CO_2$ at high toluene concentration. Particulates were increased from 0.017 $\mum$ to 0.3 $\mum$ range of size distribution.

• 한국디지털정책학회:학술대회논문집
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• 2007.06a
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• pp.149-161
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• 2007

This study aims to examine the relationships between job attitude and leadership styles perceived by employees in venture firms. This study have the two purposes, 1) to investigate the relationship between leadership styles and job attitudes(Organizational Commitment and Turnover Intention), 2) to verify the effective leadership style in venture companies. We examined the impact of critical leadership styles on the job attitude of employees in venture firms. Hypotheses on four factors were tested for 26 organizations. In order to test these hypotheses, survey questionnaires were sent to employees of venture firms in Gumi. As a result, the 184 available data were collected from venture companies. Correlation analysis, ANOVA, and regression gad been performed and the results supported first, second, and third hypotheses. However, fourth hypothesis was not supported.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.1133-1138
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• 2009

This study was conducted in order to know the internal application of the critical strain graph. To evaluate critical strain graph, we carried out an uniaxial compression test with some of internal rocks: sandstone, shale, weathered granite, and pink granitic. Based on the uniaxial compression test, we deduced relations among critical strain, failure strain, uniaxial compression strength and modulus of elasticity. As a result, the study has found out the rocks, which have been tested, can be possibly evaluated by critical strain graph.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.51-54
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• 2003

We investigated the quench characteristics of thin film type SFCLs with shunt layers of various thickness. The SFCLs ware based on 2 inch diameter YBa$_2$Cu$_3$O$_{7}$ thin films coated in-situ with a gold shunt layer. The shunt layer thickness was varied by Ar ion milling. The limiters were tested with simulated fault currents at various source voltages. The thinner the shunt layer was, the slower was the rise of SFCL temperatures. This means SFCLs of thinner shunt layers had higher voltage ratings. The voltage rating was approximately inversely proportional to the square root of the shunt layer thickness. This result could be understood through the concept of heat balance.e.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.242-245
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• 2003

We investigated the quench characteristics of thin film type SFCLs with shunt layers of various thickness. The SFCLs ware based on 2 inch diameter YBa$_2$Cu$_3$3O$_{7}$ thin films coated in-situ with a gold shunt layer. The shunt layer thickness was varied by Ar ion milling. The limiters were tested with simulated fault currents at various source voltages. The thinner the shunt layer was, the slower was the rise of SFCL temperatures. This means SFCLs of thinner shunt layers had higher voltage ratings. The voltage rating was approximately inversely proportional to the square root of the shunt layer thickness. This result could be understood through the concept of heat balance.e.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.87-90
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• 1988

This paper reports a simple posteriori error estimate method for adaptive finite element mesh generation using quadratic shape function especially for the magnetic field problems. The elements of quadratic shape function have more precise solution than those of linear shape function. Therefore, the difference of two solutions gives error quantity. The method uses the magnetic flux density error as a basis for refinement. This estimator is tested on two dimensional problem which has singular points. The estimated error is always under estimated but in same order as exact error, and this method is much simpler and more convenient than other methods. The result shows that the adaptive mesh gives even better rate of convergence in global error than the uniform mesh.

• Journal of Information Technology Applications and Management
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• v.9 no.1
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• pp.27-44
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• 2002

Performance evaluations of database algorithms are usually conducted on a set of queries for a given test database. For more detailed evaluation results, it is often necessary to use different query workloads several times. Each query workload should reflect the querying patterns of the application domain in real world, which are non-uniform in the usage frequencies of attributes in queries of the workload for a given database. It is not trivial to generate many different query workloads manually, while considering non-uniform distributions of attributes'usage frequencies. In this paper we propose a technique to generate non-uniform distributions, which will help construct query workloads more efficiently. The proposed algorithm generates a query-attribute usage distribution based on given constraints on usage frequencies of attributes and qreries. The algorithm first allocates as many attributes to queries as Possible. Then it corrects the distribution by considering attributes and queries which are not within the given frequency constraints. We have implemented and tested the performance of the proposed algorithm, and found that the algorithm works well for various input constraints. The result of this work could be extended to help automatically generate SQL queries for various database performance benchmarking.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.4
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• pp.146-154
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• 2003

This paper describes various characteristics of the new compounds for cable jackets and model cables advanced in waterproof performance in order to essentially solve the problems of underground (URD) distribution class power cable failures. Several compounds were manufactured by the inclusion of additives to base resins available in Korea and tested for basic property, mechanical and electrical characteristics. Two model cables were created by using the compounds determined in the test as being the most appropriate for new structured model cable jacket material. The waterproof performance and mechanical strength of the new cable jackets were verified by applicable tests. As a result, MDPE and LLDPE compounds were superior as cable jackets in both mechanical and electrical characteristic aspects when compared with conventional PVC. In addition, the model cables composed of the new compounds based on MDPE showed good quality results in the water permeability test.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.26-29
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• 2001

In this paper, a brief overview of problems related to the electromagnetic, mechanical design criteria is reported. Also, we described the results about the comparisons between BLDC motor and induction motor for Turbo Compressor considering motor cost, efficiency and reliability. As a result, we select an induction motor for 12.5RT Turbo compressor for the application of small building's all-conditioning system. Finally, a prototype induction motor was manufactured and tested under compressor set. The test results were successfully met the mechanical, thermal and electromagnetic point of view.