• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.1
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• pp.69-75
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• 2004

This paper presents the thermal characteristics analysis of a high-speed motor-separated spindle system consisted of angular contact ball bearings and built-in motor with oil-jet lubrication. The spindle system is composed of the main spindle and sub-spindle which are mechanically connected by a flexible coupling. The spindles are supported by two front and rear bearings, and the built-in motor is located between the front and rear bearings of the sub-spindle. The thermal analysis model of spindle system is constructed by the finite element method, and the thermal characteristics in the design stage are estimated based on temperature distribution and heat flow under the various testing conditions related to material of bearing ball, spindle speed and coolant temperature.

• International Journal of Air-Conditioning and Refrigeration
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• v.11 no.1
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• pp.40-49
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• 2003

Dynamic characteristics of water hammer arresters installed in a building water supply system have been investigated numerically by utilizing a commercial code that employs the method of characteristics. Some preliminary results with those arrester models produced in this study agree well with the previously reported. Then, the arrester models have been incorporated into a water supply pipe system of a 59 $m^2$apartment unit constructed by a leading construction company, and their dynamic characteristics have been investigated, especially on the reduction in the water hammer pressure. It is found that the setting of the arresters in the pipe system, which is recommended by the company, may not be proper for reducing the pressure down below 1,082.0 kPa (10.0 kg$g_f$/$cm^2$) when quick-closure valves in the pipe system are closed within 30 ms at the static pressure of 542.6 kPa (4.5 kg$g_f$/$cm^2$). More arresters in the system may be required to meet pressure criteria stated on the related standards and codes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.4
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• pp.269-277
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• 2002

Dynamic characteristics of water hammer arresters installed in a building water supply system have been investigated numerically by utilizing a commercial rode that employs the method of characteristics. Some preliminary results with those arresters produced in this study agree well with the previously reported. Then, the arresters have been incorporated into a water supply pipe system of a $59m^2$ apartment unit constructed by a leading construction company, and their dynamic characteristics, especially on the reduction in the water hammer pressure, are investigated. It is found that the setting of the arresters in the pipe system, which is recommended by the company, may not be proper for reducing the pressure to less than 1082.0 kPa when buick-closure valves in the pipe system are closed within 30 ms at the static pressure of 542.6 kPa. More arresters in the system may be required to meet a pressure criteria.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.312-318
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• 2001

This paper suggests the finite element method to analyze the dynamic characteristics of a rotating HDD system including the supporting structure with general shape. The flexible supporting structure was modeled by tetrahedra elements to produce a finite element model of disk-spindle-shaft-housing system and the dynamic characteristics of the HDD system was investigated due to the change of rotating speed. The validity of the presented method was verified by the modal testing. The supporting structure has an crucial effect on lower modes for HDD system, so that it is required to consider the supporting structure to accurately analyze the dynamic characteristics of HDD system.

• Solar Energy
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• v.19 no.3
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• pp.75-83
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• 1999

The optimum drive control method have to be developed to exhibit the use object contributed trust, accuracy, amenity and energy save of product. To develop the optimum drive control method is, first, grasped the static characteristics for the entire system combined each element which consists the machine and performed the dynamic characteristics explanation based on the satisfied result which acquires at the static characteristics explanation. According to this explanation, the response of the system shows same characteristics tendency and the increasing same quantify comparing to response change of each element. So the dynamic response of the entire system shows different. Therefore this study performs the static and the dynamic characteristic explanation of entire system and each element for using air-conditioning system of solar energy based on the performed result from now on, so for application of this result.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.4
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• pp.280-286
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• 2008

In this study, characteristics simulation of heat pump system is investigated for heating and cooling using sewage water as a heat source. A simulation program for preestimate operation characteristics of heat pump system is developed. The performance of this system is resolved by several variables and the characteristics which is based on actual air and sewage temperature data. The simulation results agree well with the experimental values of COP. In the analysis of system characteristics, the COP is changed between $3\sim5$ in winter season for heating load, $4\sim6$ in summer season for cooling load. As the results of Life Cycle Cost analysis over a 15 year life cycle, the energy cost could be reduced by 250 million won if a heat pump system was used instead of a conventional boiler and an absorbtion refrigerator on the office building.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.486-487
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• 2011

In this paper, a configurable DC distributiong system is being proposed considering national power systems conditions and a comparative analysis of the transient response of the contingencies is performed with the conventional AC systems. DC systems are evaluated as a promising next-generation distribution system that provides reliable operation through high efficiency of energy use and converter control. This paper discusses about the required elements for the national DC distribution system and has analysed the fault characteristics of the AC and DC distribution systems using PSCAD/EMTDC. According to the simulation results, the DC system has improved response, due to the DC/DC converter's charging/discharging characteristics, in terms of voltage and power system characteristics when compared to AC systems.

• Asia pacific journal of information systems
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• v.4 no.2
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• pp.35-61
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• 1994

Accounting information system is the most important and formal subsystem of the total information system of an organization which produces and delivers financial information. An organization has its own contigent characteristics. It is the key to a successful development of accounting information system to select the development mode and information characteristics appropriate for the contigent characteristics. The main purpose of this study is to analyze the relationship between the contigent factors and the development mode of accounting information system. In addition, this study will examine the relationship between the contigent variables and the information characteristics of accounting information system. The research method adopted in this study is the survey. The results show that the environmental uncertainty, organization size, task diversity, task interrelatedness, and management commitment are positively related with the involvement and role of user in the system development process. The aggregate information regarding various departments tends to be produced by an organization under the uncertain environment. The information is reported periodically by a centralized organization. The aggregate information is preferred when tha task for implementation is diversified. The output information is more aggregate and provided more frequently when there exists a high interrelatioship between tasks. The output information is more external and reported more frequently in an organization with the high management commitment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.6
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• pp.491-496
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• 2005

In this paper, test on characteristics of 3-phase line-interactive UPS system, known as delta conversion UPS system, is studied. Delta conversion UPS system is new line-interactive UPS system using two series-parallel PWM converters instead of using series inductor in conventional single conversion line-interactive UPS system. It is known that the characteristics of input and output in delta conversion UPS system is much improved by controlling source current of AC lines directly. Here the results on load test, normal/backup mode test, and normal/bypass mode test, which are very important in the test on characteristics of UPS system, is presented. And finally overall evaluation on delta conversion UPS system is given.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.20 no.4
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• pp.191-204
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• 2009

It is essential to estimate and evaluate for user satisfaction and quality management of database system, understanding of user needs and quality characteristics. Based on ISO 25000 series, it was suggested, the first research, that 5 main quality characteristics, 21 sub quality characteristics and 48 internal quality characteristics. There are comparative significance methods of main quality characteristics, sub quality characteristics and internal quality characteristics but it is not easy to use directly quality model in database system industry field. Also, Considering time and cost in quality evaluation, it is impossible to evaluate 48 internal quality characteristics and its level of quality evaluation is not equal in accordance with integrity level of database system. By using AHP, this study presents selection method of quality characteristics in weight and possibility of application quality model.