• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.56-59
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• 2001

An effective method of detecting inter-turn short circuits on round rotor windings is described. Shorted-turns can have significant effects on a generator and its performance. A method of detecting inter-turn short circuits on rotor windings is described. The approach used is to measure the rate of change of the air-gap flux density wave when the rotor is at operating speed and excitation is applied to the field winding. The inter-turn short circuits sensor for synchronous generator's field winding has been developed. The sensor, installed in the generator air-gap, senses the slot leakage flux of field winding and produces a voltage waveform proportional to the rate of change of the flux. For identification of reliability for sensor, a inter-turn short circuits test was performed at the West-Inchon combined cycle power plant on gas turbine generator and steam turbine generator. This sensor will be used as a detecting of shorted-turn for field winding of synchronous generator. The purpose of this paper is to describe the design and operation of a sensitive inter-turn short circuits detector. In this paper, development of inter-turn short circuits sensor for field winding of synchronous generator and application in a field.

• Journal of Chest Surgery
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• v.44 no.6
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• pp.418-422
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• 2011

Background: It has recently become most general to use the small bore catheter to perform closed thoracostomy in treating iatrogenic pneumothorax. This study was performed for analysis of the efficacy of treatment methods by using small bore catheter such as 7 F (French) central venous catheter, 10 F trocar catheter, 12 F pigtail catheter and for analysis of the appropriateness of each procedure. Materials and Methods: From March 2007 to February 2010, Retrospective review of 105 patients with iatrogenic pneumothorax, who underwent closed thoracostomy by using small bore catheter, was performed. We analyzed the total success rate for all procedures as well as the individual success rate for each procedure, and analyzed the cause of failure, additional treatment method for failure, influential factors of treatment outcome, and complications. Results: The most common causes of iatrogenic pneumothorax were presented as percutaneous needle aspiration(PCNA) in 48 cases (45.7%), and central venous catheterization in 26 cases (24.8%). The mean interval to thoracostomy after the procedure was measured as 5.2 hours (1~34 hours). Total success rate of thoracostomy was 78.1%. The success rate was not significantly difference by tube type, with 7 F central venous catheter as 80%, 10 F trocar catheter as 81.6%, and 12 F pigtail catheter as 71%. Twenty one out of 23 patients that had failed with small bore catheter treatment added large bore conventional thoracostomy, and another 2 patients received surgery. The causes for treatment failure were presented as continuous air leakage in 12 cases (52.2%) and tube malfunction in 7 cases (30%). The causes for failure did not present significant differences by tube type. Statistically significant factors affecting treatment performance were not discovered. Conclusion: Closed thoracostomy with small bore catheter proved to be effective for iatrogenic pneumothorax. The success rate was not difference for each type. However, it is important to select the appropriate catheter by considering the patient status, pneumothorax aspect, and medical personnel in the cardiothoracic surgery department of the relevant hospital.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3747-3765
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• 2017

Existing authentication mechanisms in cellular mobile communication networks are realized in the upper layer by employing cryptographic techniques. Authentication data are broadcasted over the air in plaintext, enabling attackers to completely eavesdrop on the authentication and get some information about the shared secret key between legitimate nodes. Therefore, reusing the same secret key to authenticate several times results in the secret key's information leakage and high attacking rate. In this paper, we consider the most representative authentication mechanism, Authentication and Key Agreement (AKA), in cellular communication networks and propose an enhanced AKA scheme based on Physical Layer Authentication (AKA-PLA). Authentication responses generated by AKA are no longer transmitted in plaintext but masked by wireless channel characteristics, which are not available to adversaries, to generate physical layer authentication responses by a fault-tolerant hash method. The authenticator sets the threshold according to the authentication requirement and channel condition, further verifies the identity of the requester based on the matching result of the physical layer authentication responses. The performance analyses show that the proposed scheme can achieve lower false alarm rate and missing rate, which are a pair of contradictions, than traditional AKA. Besides, it is well compatible with AKA.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.11
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• pp.595-599
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• 2013

The pipes used in buildings are generally categorized into metallic or plastic materials. Metal pipes, such as copper and stainless steel pipes, are mainly used for water and hot water supply, and for the heating system. However, plastic pipes made of polyethylene and cross-linked polyethylene are used for floor heating, water drainage, and air vent systems. Usually, plastic pipes have thermal demerits, such as high linear expansion coefficients and bending phenomenon by hot water, although the pipes have several merits of light weight, low price, low thermal conductivity, and the comparatively high workability of metal pipes. Therefore, if those kind of demerits are overcome, plastic pipes can be easily accepted for hot water systems. This research is aimed to evaluate the applicability for vertical heating pipes of a plastic pipe system consisting of electric fusion fitting of a conductive carbon compound and propylene random glass fiber pipe, through measurement of the expansion rate and leakage in summer and winter seasons, in the apartment construction field.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.114-120
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• 2006

The basic effects of hydrogen addition for engine performance and emission were investigated in single cylinder research engine. Seven commercial injectors were tested to choose a suitable injector for hydrogen injection prior to its engine implementation. The hydrogen fuel leakage and flow rate were evaluated for each injector and KN3-1(Keihin, CO.) showed the best performance for hydrogen fuel. At the higher excess air ratio(${\lambda}=1.7$, 2.0), the better combustion stability was found with hydrogen addition even though its effect was small at lower excess air ratio (${\lambda}=1.0$, 1.3). Stable operation of the engine was even guaranteed at ${\lambda}=2.0$, if the amount of hydrogen gas was near 15% of total energy. In the lean region, ${\lambda}>1.3$, thermal efficiency was improved slightly while it was not clearly observed at ${\lambda}=1.0$, 1.3. It is considered that, in some cases, high temperature environment due to hydrogen combustion caused further heat loss to surroundings. Except for ${\lambda}=1.0$, with larger amount of hydrogen addition, CO was reduced drastically but it was emitted more at the leaner region. Nitric oxides(NOx) was increased a little more with hydrogen addition at ${\lambda}=1.0$, 1.3. However, at ${\lambda}>1.3$ its relative amount of emission was low. In addition, the amount of NOx was continuously decreased with hydrogen addition, but, at ${\lambda}=2.0$ the amount of NOx was lowered to 1/100 of that of ${\lambda}=1.0$. THC emission was significantly increased as air/fuel ratio was raised to leaner region due to misfire and partial burn.

• Food Science and Preservation
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• v.10 no.3
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• pp.272-277
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• 2003

This study was conducted to determine the minimal processing characteristics as affected by the storage duration of whole Asian pears(Pyrus pyrifolia Nakai cv. Niitaka). Before and after storage for 4 months under air at 0$^{\circ}C$, whole pears were sliced, placed in unsealed plastic bags, and kept for 4 days at 10$^{\circ}C$. Storage of whole pears increased the initial levels of electrolyte leakage, total phenols and browning index and decreased the initial content of vitamin C in pear slices. Slices from stored pears maintained higher respiration rate compared with slices from non-stored pears during keeping. The increase of electrolyte leakage, browning index and microbial number and the decrease of total phenol in slices during keeping were more fast in slices from stored pears than in those from non-stored pears. These results suggest that the minimal processing characteristics of ‘Niitaka’ pears are depending upon storage duration.

• Journal of the Korean Institute of Gas
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• v.22 no.4
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• pp.1-6
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• 2018

An LNG bunkering system stores LNG in a horizontal IMO's C-Type tank insulated with perlite powder, and $10^{-2}$ Torr vacuum in the annular space between the double walls. Current storage tanks have high heat leakage, evaporating over 2.0% daily. A more efficiently insulated storage tank reducing the evaporation rate is required to develope. This research carried out thermal analysis on a new effective insulation method, i.e. double shield insulation system, that separates high super vacuum in the annular space between two tanks with a perlite vacuum in the back side of outer tank. This highly efficient insulation system obtained an evaporation rate of 0.16% per day under a $10^{-4}$ Torr vacuum. Even if the space loses its vacuum, the new insulation system showed a lower evaporation rate of 5.23% than the present perlite system of 4.9%.

• Fire Science and Engineering
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• v.25 no.4
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• pp.48-55
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• 2011

This paper presents the failure analysis of the rate of rise spot type heat detectors on artificially accelerated aging. The failures of heat detector turned out by two reasons. The first one is the separation of binder from plastic moulding, resulting in the leakage of air from heat chamber. The second reason is the crack of plastic. The large cracks were maybe created by these reasons, thermal expansion difference, mechanical stress, or growth of microcrack. In the sound detector, the separation and the crack were not occurred or not developed to the critical size. The glass fibers which increase the mechanical strength were added in the binder of detector 2010G. The densities of binder or plastic of each detector were similar. However, the TGA result shows that the thermal characteristics of 2005A and 2005B were not similar.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.4
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• pp.415-424
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• 2004

Cooling the electronic equipment is one of the major focal points of the design process and the key to successful product launch. The two-phase loop thermosyphone which is a good candidate among many available options was investigated fur cooling of the high power amplifiers. The system is composed of evaporator which contains 6 parallel cold plates, fan cooled condenser, gas-liquid separator, and interconnecting tubes. Experiments were performed for several refrigerant charging values, hs and as a experiment result, the optimum charging value fur this system was proposed. In order to optimize the system design, the operating cycle pressure and inlet/outlet temperatures of evaporator and condenser are measured and analyzed. The effect of the three parameters such as flow rate and temperature of condenser cooling air, and thermal load on the evaporator are investigated. The lower the operating pressure and the cycle temperatures are also better to prevent the leakage of the system. The system invesigated in this paper can be directly used for cooling of a real unmanned wireless communication station.

• Journal of Chest Surgery
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• v.8 no.2
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• pp.125-134
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• 1975

The record of 137 patients with spontaneous pneumothorax seen at Busan National University Hospital during past 3years were reviewed to study the possible pathogenesis and its effective management. and the results obtained as follows; 1] The incidence of the "spontaneous" pneumothorax which developed without underlying pathology was 13-1%. The majority of those cases was considered as the result of rupture of subpleural blebs. 2] The incidence of secondary pneumothorax which developed with underlying pathology was 50.0%, in which 42.3% was combined with pulmonary tuberculosis and 8, 0% was combined with pulmonary infection. The traumatic pneumothorax was developed in 36-5% of total series. 3] In age distribution, there was pronounced difference between spontaneous and secondary pneumothorax. The majority of spontaneous pneumothorax cases was 20-30 decade and tall and tall and thin in body structure. In secondary pneumothorax, however, the incidence was relatively high in age group more than 50 years old. 4] The incidence of pneumothorax combined with pulmonary tuberculosis was particularly high in our country, and the cause of pneumothorax was seemed due to the rupture of subpleural caseous foci in some cases, but the majority was seen due to the rupture of emphysematous blebs which were formed with a pathological process of chronic tuberculosis. 5]Closed [tube] thoracotomy was the main therapeutic approach of choice in the great majority ,of pneumothorax in our series with the relapse rate of 19.6%. However, open thoracotomy and adequate surgical procedures should be undertaken in patients with continuous air leakage over 7 days and recurrent attack of pneumothorax.