• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.22 no.2
• /
• pp.155-161
• /
• 2008

The grounding systems provide a low resistance path for fault or normal currents into the earth. The material for reducing ground resistance is buried around the grounding electrode to increase its effective size of the electrode and thus to obtain low ground resistance. Increasing the contacting area with the grounding electrode is effective for lowering the ground resistance in soils. Using this idea the conductive expansion ground resistance reducing material was developed. In this paper experimental data has shown that the ground resistance reduction method using proposed material is superior to using a typically available commercial ground resistance reducing material.

• Proceedings of the KIEE Conference
• /
• 2001.07b
• /
• pp.696-698
• /
• 2001

This paper considers the research of the hybrid interrupter which adopts both rotating arc and thermal expansion technology. The operating principle of this device depends on rapid arc rotation due to the magnetic field created by the fault current through a coil which is mounted on contacts and also relies on the principle of thermal expansion created by arc energy in extinguishing chamber and finally causes pressure rise in expansion volume. To develope this type of interrupter, we introduced analytical analysis including electromagnetic and arc fluid simulation and experimental analysis including construction of current source generation facility and arc behavior measurements. In this research, the principle of the interrupting techniques are given and analytical and experimental results of hybrid interrupter which is developed by new technology is introduced.

• Journal of the Korean housing association
• /
• v.17 no.5
• /
• pp.137-146
• /
• 2006

This study was aimed to analyze the influences of urban expansion by developing a new large scale residential district on changes of whole urban spatial structure. For the analysis, time serial analysis was conducted on the Daejeon Metropolitan City by using the space syntax method. The results of the study are as follows ; First, an expansion of urban area led to lower both of the local and global integration levels, second, the spatial occupation ratio of upper 10% in the whole integration showed that old city center was separated, and moved to the Dunsan District, third, the results also showed that an integration of the old city center region maintained a high level in spite of a movement of city center and its local integration still had highest level so that the old city center will take one of the two city center roles together with Dunsan District.

• Journal of Genetic Medicine
• /
• v.1 no.1
• /
• pp.23-26
• /
• 1997

Myotonic dystrophy (DM) is caused by the expansion of CTG trinucleotide repeat near the 3' end of the gene encoding for a member of protein kinase gene family (DMPK). The normal range of the CTG repeat was determined in 178 normal individuals (141 unrelated individuals and 37 of 9 families) by polymerase chain reaction (PCR), polyacrylamide gel electrophoresis and silver staining method. And the expansion of the CTG repeats in a DM family was analyzed with Southern analysis. In normal population, the range of CTG repeat is between 5 and 34 and 19 different alleles were observed in that range, and $(CTG)_{11-14}$ alleles were predominant. 4 members of an affected family showed the 0.5-2.0 kb size expansion of CTG repeats. In this study we could predict the incidence of DM in Korea as 1 in 20,000 and we could establish the diagnostic procedure for myotonic dystrophy.

• International Journal of Highway Engineering
• /
• v.14 no.6
• /
• pp.37-43
• /
• 2012

PURPOSES : This study is to evaluate the feasibility of setting the standard of cement alkali content by using ASTM C 1260(accelerated mortar bar test) METHODS : This study analyzes the ASR(alkali silica reaction) expansion of cement mortar bar based on the changes in the aggregate type(fine, coarse), cement type(ordinary, low alkali), and replacement contents of fly ash. ASR tests were conducted according to ASTM C 1260. RESULTS : In this test results, There is no big difference in the ASR expansion between ordinary cement and low alkali cement. From this test results, it was found that the variation of cement alkali content did not have a effect on ASR expansion because mortar bar was placed in a container with sufficient alkali aqueous solution at high temperature during the test process of ASTM C 1260. CONCLUSIONS : It is evidently clear that the alkali content of cement have a effect on ASR. But ASTM C 1260 is difficult to assess this effect.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.886-891
• /
• 2000

One of the domestic co-generation plants have undergone excessive vibration problems of turbine attributed to external force for years. The root cause of turbine vibration may be shan alignment problem which sometimes is changed by thermal expansion and external farce, even if turbine technicians perfectly performed it. To evaluate the alignment condition from plant start-up to full load, a strain measurement of turbine and main steam piping subjected to thermal loading is monitored by using strain gages. The strain gages are bonded on both bearing housing adjusting bolts and pipe stoppers which. installed in the x-direction of left-side main steam piping near the turbine inlet in order to monitor closely the effect of turbine under thermal deformation of turbine casing and main steam piping during plant full load. Also in situ load of constant support hangers in main steam piping system is measured by strain gages and its results are used to rebalance the hanger rod load. Consequently, the experimental stress analysis by using strain gages turns out to be very useful tool to diagnose the trouble and failures of not only to stationary components but to rotating machinery in power plants.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.568-573
• /
• 2003

When a safety valve equipped in a nuclear power plant opens in an instant by an accident, a moving shock wave propagates downstream the valve, inducing a complicated unsteady flow field. The moving shock wave may exert severe load to the structure. So, to reduce the load acting on the wall of POSRV, a gradual opening of POSRV is adopted in general. In theses connections, a numerical work is performed to investigate the effect of valve opening time on the unsteady flow fields downstream of the valve. Compressible, two-dimensional Navier-Stokes equations are used with the finite volume method. The obtained results show that sharp pressure rise through moving shock tor the case of instant opening is attenuated by employing the gradual opening of valve. It is turned that the flows for the two cases of gradual valve opening time show the similar to that of highly under-expanded one in jet structure having expansion and compression waves and Mach stem. Also, comparing with the results for the two cases of opening time, the shorter the valve opening is, the pressure gradient at the downstream of the valve becomes softly.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.225-231
• /
• 2004

Scroll compressor has been used extensively for refrigeration since the early 1980's for its improved efficiency, greater reliability, smoother operation, lower noise and vibration. And also, nowadays, the scroll mechanism is used for expander even though in niche market yet. But scroll expander has not been used for high-temperature and high-pressure gas, because the continuous expansion of the gas causes a wide range of temperature distribution over the whole scroll wrap that leads to differential thermal expansion of scroll elements, which results in system vibrations, noise and efficiency losses. For the scroll expander to produce power more efficiently, all of radial and radial clearances between scroll wrap must be the same. In order to reduce differential thermal expansion in addition to improvements in thermal efficiency and specific power, we propose a scroll expander with heating structure. Heat-pipe heating structure is considered as the most effective method to heat the scroll expander at a uniform temperature. This paper includes some results of preliminary study of the scroll expander with heating structure and proposals of their systems for power generation and refrigeration.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.17 no.2
• /
• pp.173-178
• /
• 2011

Marine TEMA heat exchanger is the equipment to transfer the heat energy through both fluids that are enclosed separately by applying conduction and convection phenomena for a large vessels, Especially for heat exchanger working under the high temperature and high pressure, the expansion ratio should be taken into account other than under the low temperature and low pressure. This study was tried to find out the ideal expansion ratio through analyzing the elasto-plastic stress behavior of deformation while tubes are expanded with the finite element methods.

• Korean Journal of Optics and Photonics
• /
• v.13 no.6
• /
• pp.530-536
• /
• 2002

The accurate measurements of thermal expansion coefficients is one of the most important techniques required not only in material science but also in industries. A high precision interferometric dilatometer, using acoustic optical modulator, has been constructed and its performance has been tested. The system consists of a double-path optical heterodyne interferometer and a radiant heating furnace. This provides highly accurate length measurement, and allows rapid heating and cooling method for the specimen. A three longitudinal mode frequency stabilized He-Ne laser, using the secondary beat frequency, is constructed. Its stability is found to be $5{\times}10^{-9}$. The uncertainty in the length measurement is estimated to be of nanometer order in the range between room temperature to 1100 K.