• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.52-59
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• 2010

As electric power demand of customers is constantly increasing, more bulk power systems are needed to install in a network. By development of renewable energies and high-efficient facilities and deregulated electricity market, moreover, the amount of distributed resource is considerably increasing in distribution network consequently. Also, distribution network has become more and more complex as mesh network to improve the distribution system reliability and increase the flexibility and agility of network operation. These changes make fault current increase. Therefore, the fault current will exceed a circuit breaker capacity. In order to solve this problem, replacing breaker, changing operation mode of system and rectifying transformer parameters can be taken into account. The SFCL(Superconducting Fault Current Limiter) is one of the most promising power apparatus. This paper proposes a methodology for on optimal location of SFCL. This place is defined as considering the decrement of fault current by component type and the increment of reliability by customer type according to an location of SFCL in a distribution network connected with DG(Distributed Generation). With case studies on method of determining optimal location for SFCL applied to a radial network and a mesh network respectively, we proved that the proposed method is feasible.

• The Korean Journal of Physiology
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• v.20 no.1
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• pp.1-7
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• 1986

It has been well documented that the peripheral autonomic nervous system plays an important role in exocrine pancreatic secretion. However, the role of the central nervous system in pancreatic function is still obscure even though the central nervous system has been known to control gastrointestinal functions through the autonomic nervous system. Since the reticular formation in the mesencephalone seems to integrate the autonomic function, the present study was undertaken to investigate a possible influence of the reticular formation upon the exocrine pancreatic secretion. Twenty·two albino rats fasted for 24 hours were anesthetized by intraperitoneal injection of urethane in a dose of 1 g/kg, The pancreatic duct was cannulated to collect pancreatic juice and bile juice was diverted to the jejunum. The gastroduodenal junction was ligated to Prevent passage of gastic juice into the duodenum. A pair of electrodes were bilaterally inserted in the reticualr formation of the mesencephalone with aid of a stereotaxic apparatus. When the volume of pancreatic juice secreted for 10 min became constant, the reticular formation was electrically stimulated for 10 min. Parameters of the electical stimulation was 1.3V, 40 Hz and 2 msec. When the pancreatic secretion returned to the level before the electrical stimulation, cervical vagotomy (11 rats) or administration of propranolol (11 rats) in a dose of 0.1 mg/kg through the jugular vein was carried out. Ten minutes after the treatment, the electrical stimulation of the reticular formation was repeated. The brain was fixed by perfusion of 10% formaline solution through the heart, and then placement of the electrode tip was examined histologically. Protein concentration and amylase activity in samples of Pancreatic secretion were measured. The electrical stimulation of the reticular formation significantly increased in volume $({\mu}l/10\;min)$, Protein output $({\mu}g/10\;min)$ and amylase output (U/10 min) in the pancreatic secretion. The stimulatroy effects were not affected by the cervical vagotomy but completely abolished by propranolol. Meantime, it was also observed that both vagotomy and propranolol significantly reduced the pancreatic secretory function. These results indicate that the reticular formation in the mesencephalone may exert a stimulatory effect upon the Pancreatic secretory function not through the vagus nerve but through the sympathetic pathway in anesthetized rats.

• Journal of the Korean Wood Science and Technology
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• v.36 no.6
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• pp.1-12
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• 2008

A series of the studies on the applied physical properties of domestic species have been conducted last three years. Liriodendron tulipifera, Betula costata, Paulownia coreana were examined on sorption property, thermal property, electric property, acoustic property. Because the same apparatus and experimental procedures were used for all species, their results can be easily comparable. The experiments for sorption property were conducted with 80 mesh wood powder and resulted in their EMC's and sorption isotherms. The thermal conductivity and diffusivity, and electric resistance and volumetric electric resistivity were measured with a thermal-wire device and a high electric resistance meter. The differences of the thermal and electric properties between quarter-and flat-sawn specimens were observed, which was partially attributed to their anatomical differences. An acoustic measurement system was used to evaluate dynamic MOE and internal friction. This paper provides the useful fundamental data for designing a wood structure, correcting a portable resistance-type moisture meter, and acoustic properties of wood.

• Journal of the Korean Institute of Gas
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• v.22 no.4
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• pp.27-31
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• 2018

Classification of explosion hazard areas is very important in terms of cost and safety in the workplace handling flammable materials. This is because the radius of the hazardous area determines whether or not the explosion-proof equipment is installed in the electrical machinery and apparatus. From November 6, 2017, KS C IEC-60079-10-1: 2015 will be issued and applied as a new standard. It is important to understand and apply the difference between the existing standard and the new standard. Leakage coefficients and compression factors were added to the leakage calculation formula, and the formula of evaporation pool leakage, application of leakage ball size, and shape of explosion hazard area were applied. The range of the safety factor K has also been changed. Also, in the radius of the hazardous area, the existing standard applies the number of ventilation to the virtual volume, but the revised standard is calculated by using the leakage characteristic value. In this study, we investigated the differences from existing standards in terms of ventilation and dilution and examined the effect on the radius of the hazard area. Comparisons and analyzes were carried out by applying revised standards to workplaces where existing explosion hazard locations were selected. The results showed that even if the ventilation and dilution were successful, the risk radius was not substantially affected.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.3
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• pp.257-272
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• 2016

It is usually not an easy task to counter-measure on time and appropriately when confronting with troubles in mechanized tunnelling job-sites because of the limitation of available spaces to perform those actions with the existence of disk cutter, cutter head, chamber and other various apparatus in Tunnel Boring Machine (TBM). So, it is important to predict the ground condition ahead of a tunnel face during tunnel excavation. Efforts have been made to utilize geophysical methods such as elastic wave survey, electromagnetic wave survey, electrical resistivity survey, etc for predicting the ground condition ahead of the TBM tunnel face. Each prediction method among these geophysical methods has its own advantage and disadvantage. Therefore, it might be needed to apply several geophysical methods rather than just one to predict the ground condition ahead of the tunnel face in the complex and/or mixed grounds since those methods will compensate among others. The problem is that each prediction method will give us different answer on the predicted ground condition; how to combine different solutions into a most reasonable and representative predicted value might be important. Therefore, in this study, we proposed a methodology how to systematically combine each prediction method utilizing probabilistic analysis as well as analytic hierarchy process. The proposed methods is applied to a virtual job site to confirm the applicability of the model to predict the ground condition ahead of the tunnel face in the mechanized tunnelling.

• Journal of IKEEE
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• v.22 no.2
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• pp.495-498
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• 2018

In this paper, we propose an DAP system for dose evaluation of medical and industrial X-ray generator. Based on the DAP measurement technique using the Ion-Chamber, the proposed system can clearly measure the exposure radiation dose generated by the diagnostic X-ray apparatus. The hardware part of the DAP measures the amount of charge in the air that is captured by an X-ray. The high-speed processing algorithm part for cumulative radiation dose measurement through microcurrent measures the amount of charge captured by X-ray at a low implementation cost (power) with no input loss. The wired/wireless transmission/reception protocol part synchronized with the operation of the X-ray generator improves communication speed. The PC-based control program part for interlocking and aging measures the amount of X-ray generated in real time and enables measurement graphs and numerical value monitoring through PC GUI. As a result of evaluating the performance of the proposed system in an accredited testing laboratory, the measured values using DAP increased linearly in each energy band (30, 60, 100, 150 kV). In addition, since the standard deviation of the measured value at the point of 4 division was ${\pm}1.25%$, it was confirmed that the DAP showed uniform measurements regardless of location. It was confirmed that the normal operation was not less than ${\pm}4.2%$ of the international standard.

• Journal of the Mineralogical Society of Korea
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• v.14 no.2
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• pp.99-110
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• 2001

A gem-quality yttria-stabilized zirconium oxide crystals were synthesized by the skull-melting method, using the RF electrical apparatus. Principal raw materials used were $ZrO_2$and 25 wt.% $Y_2O_3$as stabilizer and 0.03~0.05 wt.% $Nd_2O_3$decolorizing agent were added to it. The single crystals were approximately 20$\times$63 mm in size with chemical composition $Zr_{0.73}$ $Y_{0.27}$ $O_{1.87}$ . The crystals are isotropic with no appreciable anisotropism under a polarizing microscope. Their refractive indices are in the range of 2.15~2.18, specific gravity 5.85, Mohs' hardness 8~8.5, and reflectivity 13.47%. The zirconia crystals were confirmed to have cubic structure with Face-centered lattice(Z=4), space group Fm3m ($CaF_2$-type structure) and unit cell parameters are a=5.157 $\AA$. The optimal growing conditions for yttria-stabilized zirconia are 50 kW, 2.94 MHz in power and to use a crucible with 105 mm $\times$ 135 mm in size. When the lowering speed of the crucible was set 16mm/hr gave the best yield, 42%. Since the refractive index(2.15~2.18) of cubic zirconia is smaller than that of diamond, the angle between crown and pavilion should be fashioned to make it smaller than $40.5^{\circ}$ to show the maximum brilliancy and fire.

• Journal of the Korean Wood Science and Technology
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• v.36 no.4
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• pp.1-10
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• 2008

A series of the studies on the applied physical properties of domestic species have been conducted last three years. Pinus koraiensis and Larix kaempferi were two of the three species examined for the first year. Because the same apparatus and experimental procedures were used for all species, their results can be easily comparable. The experiments for sorption property were conducted with 20- and 80-mesh wood powder and resulted in their EMCs and sorption isotherms at various RH conditions. The thermal conductivity and diffusivity, and electric resistance and volumetric electric resistivity were measured with a thermal-wire device and a high electric resistance meter. The differences in the thermal and electric properties between quarter- and flat-sawn specimens were observed, which were partially attributed to their anatomical differences. An acoustic measurement system was used to evaluate dynamic MOE and internal friction. This paper provides the useful fundamental data for designing a wood structure, correcting a portable resistance-type moisture meter, and acoustic properties of wood.

• Journal of Periodontal and Implant Science
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• v.34 no.3
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• pp.551-562
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• 2004

The purpose of this study was to evaluate the effects of negatively electric field on bone healing in rabbit segmental long bone defects using negatively charged PTFE membrane. Ten millimeter segmental defects in the rabbit radius were used as the experimental model. After membranes were then charge injected using a corona-charging apparatus, the left defects were covered with non charged PTFE membranes as control groups, whereas the right defect was covered with negatively charged PTFE membranes as test group. The animals were divided into 4 groups of 2 rabbits each, and sacrificed at 2, 4, 6, and 8 weeks. Histomorphometric analysis showed a more newly formed bone in negatively charged membrane at early healing period. At 2 weeks, the proportion of new bone formation to total defect area was 0.32% in control group, 1.10% in experimental group. At 4 weeks, the proportion of new bone formation to total defect area was 6.86% in control, and 13.75% in experimental. At 6 and 8 weeks, no obvious difference was found between the two groups but newly formed bone in test groups were slightly more than that in control groups. In conclusion, negatively charged membranes showed more newly bone tissue than noncharged membranes at an early healing period. Although the number of samples was small, this study showed that the combination of negatively electrical stimulation and P1FE membrane may be of value in long bone healing.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.8
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• pp.511-519
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• 2017

In this study, we have performed tests to improve the productivity of hybrid solar stills, which can be operated by solar thermal energy and/or waste heat of exhaust gas from electrical generators. The experimental apparatus is a hybrid solar still with a $1m{\times}2m$ collecting area, which consists of a conventional simple solar still and a vertical multi-effect diffusion(MED) section. The experiments were conducted under various operating conditions, with two identical hybrid solar stills, using solar radiation as the energy source. The results of the tests showed that the yield of the hybrid solar still depends on the various operating conditions. Insulation at the side glasses and a lower basin seawater level increased the productivity of the hybrid solar still. Reflecting fins with less than 47% reflectivity unexpectedly decreased the total productivity. However, the various feeding flow rate of the seawater into MED part did not show clear effects on productivity in the tested range.