• Tunnel and Underground Space
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• v.25 no.6
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• pp.543-555
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• 2015

At present, local limestone mines with large opening employ auxiliary fans for workplace ventilation which have been used in coal mines with much smaller airways. Considering the low static pressure loss in the large-opening mines, high pressure auxiliary fans face serious economical limitations mainly due to their excessive capacity. The optimal fan selected for the ventilation in large-opening working places should supply air quantity enough for maintaining safe environment and keep its operating cost as low as possible. This study focuses on the development of a low pressure auxiliary fan designed to have smaller range of the static head but to have more potential for higher ventilation and energy efficiency. The flow characteristics of high and low pressure auxiliary fans were theoretical as well as experimentally investigated to assess the ventilation efficiency in term of environmental and economical aspects. Moreover, the low pressure fan was tested in two limestone mine sites with small and large cross-sectional areas for evaluating its ventilation efficiency. Results from this study can be applied to improve the economy and efficiency of auxiliary fan for ensuring better air quality and work environment management.

• Journal of Energy Engineering
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• v.21 no.3
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• pp.292-300
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• 2012

KHNP CRI has been developing APR+ nuclear power plant since 2007, which is GEN III+ model with 4,361 MWth capacity. To develop safer and more economical nuclear power plant than APR1400, we studied domestic and foreign nuclear power plants under construction. We also reviewed nuclear power plants which are appropriate for domestic construction in Korea and also for export. Economic assessments were made twice during the second phase of standard detailed design of the plant. The result of the second phase of economic analysis for APR+ standard detailed design showed that APR+ N-th plant was 24.6% more economical than coal-fired 1,000MW power plant, and was evaluated to be competitive enough in global market for construction of the nuclear power plant.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.16-16
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• 2009

Alloy 82/182로 용접된 원자력 발전소 주기기의 이종 금속 용접부는 장기간 운전 후 응력부식균열(SCC : Stress Corrosion Cracking)에 의한 결함이 나타나게 된다. 2000년대 이후로 원자력 주기기 Alloy 82/182 용접부에서 PWSCC(Primary Water Stress Corrosion Cracking)에 의한 Degradation이 급격히 증가하는 추세를 보이고 있으며, 국내에서도 이와 관련하여 원자력 발전소의 안전성에 대한 Issue 및 대비책에 대한 관심이 고조되고 있다. 이러한 Alloy 600 용접부에 대한 결함을 예방하기 위한 대표적인 기술로써 수명연장 오버레이 기술이 있다. 원자력 주기기 노즐부는 저탄소강으로 제작되어 있으며, 저탄소강에는 제작 시 용접후열처리가 적용된다. 후열처리를 하는 주된 이유는 Tempering을 통해 열영향부의 인성 및 연성의 회복과 강도를 감소시켜 모재와 동등 또는 이 이상의 물성을 갖도록 하는 데 그 목적이 있다. 그러나 수명연장 오버레이의 경우 현장 작업 시에 후열처리가 어렵기 때문에, 이를 대체하기 위한 기술로 템퍼비드 용접을 적용할 경우 후열처리를 면제해 주고 있다. 본 연구에서는 수명연장 오버레이 기술 개발의 일환으로써 저 탄소강에 대한 템퍼비드 용접 기술을 확립하였다. 실험에 사용된 모재는 원자력 주기기의 노즐에 사용되는 SA508 Gr.3 Cl.1을 사용하였으며, 용가재는 Alloy 52 및 52M을 사용하였다. 최적 조건 도출을 위해서 실험 매트릭스를 이용하여 기본 실험을 수행하였으며, 실험에는 자동 GTAW 용접을 적용하였다. 기본 실험을 통해 얻은 최적 조건을 사용하여 PQ 시험을 수행하여 WPS를 확보하였다. 분석은 용접 후 조직 및 경도 시험, 물리시험(인장시험, 굽힘시험 및 충격시험)을 수행하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.112-119
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• 1993

A strength and durability estimation system of involute cylindrical gears which are commonly used as power transmission devices is developed on the personal computer, which analyzed and/or evaluates the gear design and the service performance at the point of view of strength and durability. The typical considerations are the bending strength and the sunface durability, and the strength and durability estimations are carried out using the reliable standards of AGMA&ISO. In addition, the finite element analysis (FEM) of tooth bending stress is conducted in order to compare the real maximum stress with the estimaed bending stress by the standard. Therefore, the system is built so that the variables or factors considered differently in those standards and the strength & durability are appraised seperately by each method, and a series of the estimation processes is integrated into the system can be used in the initial design at the view point of strength and durability. And it is useful to the purpose of the trouble-shooting of gear system and the purpose of introducing the methods for maintaining design strength in service, with appraising the strength and durability after design or with appraising the influencing factors, as a whole. Therefore, this strength and durability estimation system can help the aim of automatic design of cylindrical gears.

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.6
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• pp.411-419
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• 1999

It has been well recognized that a long term service at elevated temperature of $350^{\circ}C{\sim}550^{\circ}C$ induces embrittlement damage due to carbide precipitation and/or P, Sb and Sn segregation at grain boundaries and thereby deteriorates the grain boundary strength of heat resisting components in the energy-related plants. Therefore, it is very important to assess quantitatively the extent of embrittlement damage of heat resisting components to secure the reliable and efficient service condition and to prevent brittle failure in service. However, because fracture tests are limited in size and number of specimen obtained from the structural components, nondestructive test method is required. In this study, the optimum electrochemical parameters are investigated and discussed to evaluate nondestructive embrittlement damage for aged 2.25Cr-1Mo steels by means of electrochemical polarization test method (ECPTM) in proper corrosive environment. In addition, the electrochemical test results are compared with embrittlement degree evaluated by semi-nondestructive SP test.

• Journal of the Society of Disaster Information
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• v.7 no.2
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• pp.87-95
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• 2011

The skid resistant of pavement surface is an important parameter since it is directly related to the traffic safety under moving vehicular loads. In particular, it should be considered as a major factor in pavement performance evaluations to reduce the traffic accident from vehicular sliding. In this study, a portable and an automatic skid resistance tests were used to evaluate the skid resistances of the in-situ pavements. The test results showed that the skid resistance of the conventional dense graded pavement was more noticeable than the other pavement types such as the drainage pavement and the stone mastic asphalt(SMA) pavement as the service life of pavement was increased.

• Journal of Sensor Science and Technology
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• v.9 no.5
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• pp.380-388
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• 2000

The finite element analysis of a micro turbine was made to investigate safety margin of its operating condition for the high aspect ratio nickel micro turbine blades fabricated by conventional LIGA-like method. From our study, we found that the fabricated turbine could not exceed its yield strength even if the pressure difference between inlet and outlet of turbine blade was about 44kPa, and the correlation of friction coefficient and the maximum stress, caused by contact friction between outer diameter of shaft and inner diameter of turbine blade, was somewhat reciprocal. The maximum stress was decreased with the increasing contact friction, when turbine blade was in its state of rotation. By the results of our study, we conclude that it is possible to fabricate metal micro turbine more easily han surface micromachining technology and to operate with no risk of metal structure's damage, which is caused by yield strength, if the operating condition with the design of micro turbine itself are optimized. It is useful to adopt other applications which have the contact problems between a moving part and the fixed one in micro structures.

• Journal of Broadcast Engineering
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• v.12 no.3
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• pp.203-213
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• 2007

DMB video/audio service was successfully launched. DMB data service is a matter of primary concern now. The TTI(Traffic and Travel Information) service is considered as a killer application of the data service. Tn this paper, we propose a method for design and implementation of the broadcasting system for TTI service. The proposed TTI service system consists of an authoring tool, the DB module, the Transmission module and Monitoring module. This system satisfies the national TTA standards of the Traffic and Travel Information data services for terrestrial DMB; TPEG(Transport Protocol Experts Group) platform. The system was designed to support real-time automatic transmission for CTT and CTT SUM, and non real-time authoring & automatic transmission for POI and SDI, and was focused on the capability to make high-quality contents efficiently and to send them to the data inserter reliably. The performance of the implemented system was proven through the conformance tests with the various commercial receivers. After the continuous upgrade, the system is being used in commercial service.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.670-677
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• 2009

This paper is a study of testing on-board signalling equipment in advanced high speed rail at the maximum speed of 400km/h. The on-board signalling equipment in advanced high speed rail provides operating information to the driver when operating at ATC, ATS, and ATP sections, and maintains safety from driver oversight, signalling equipment malfunction, natural disasters and so on. Since the testing train performance of advanced high speed rail at 400km/h must include the function test of on-board signalling equipment, this thesis focuses on the function test of on-board signalling equipment and analyze the necessity of the test at the maximum speed. Finally, it is suggested to change some infrastructure and to use specific test methods to test the train performance at the maximum speed in high speed line ATC section.

• Nuclear Engineering and Technology
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• v.16 no.1
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• pp.36-46
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• 1984

Studied are the statistical thermal design (STD) methods that have been developed to satisfy the design basis which protects a pressurized water reactor (PWR) core against departure from nucleate boiling (DNB) during normal operations and anticipated transients. The objective of the statistical thermal design is to quantify the thermal design margin and to remove any excess conservatism from the DNB ratio calculations through statistically combining design parameter uncertainties, while still maintaining a high level of core protection. This report describes and compares the STD methods developed by the two U.S. reactor vendors (Westinghouse and B & W). Included are the characteristics of STD, statistical treatment of uncertainties, DNB design limit development methodology and the sample application of the STD technique to core thermal design analysis. It is observed that the STD methods developed by the two vendors are similiar to each other in principle, but different in the treatment of the uncertainties associated with the design parameters. The statistical thermal design is found to significantly improve the thermal design margin.