• Korean Journal of Materials Research
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• v.21 no.9
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• pp.477-481
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• 2011

Composites of insulating polyethylene and carbon black are widely used in switching elements, conductive paint, and other applications due to the large gap of resistance value. This research addresses the critical exponent of dielectric breakdown strength of polymer matrix composites (PMC) made with carbon black and polyethylene below the percolation threshold (Pt) for the first time. Here, Pt means the volume fraction of carbon black of which the resistance of the PMC is transferred from its sharp decrease to gradual decrease in accordance with the increase of carbon-black-filled content. First, the Pt is determined based on the critical exponents of resistivity and relative permittivity. Although huge cohesive bodies of carbon black are formed in case of being less than the Pt, a percolation path connecting the conducting phases is not formed. The dielectric breakdown strength (Dbs) of the PMC below Pt is measured by using an impulse voltage in the range from 10 kV to 40 kV to avoid the effect of joule heating. Although the observed Dbs data seems to be well fitted to a straight line with a slope of 0.9 on a double logarithm of (Pt-$V_{CB}$) and Dbs, the least squares method gives a slope of 0.97 for the PMC. It has been found that finite carbon-black clusters play an important role in dielectric breakdown.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.6
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• pp.574-578
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• 2006

Toward the practical applications, on operation of conduction-cooled HTS SMES at temperatures well below 77 K should be investigated, in order to take advantage of a greater critical current density of HTS and considerably reduce the size and weight of the system. Recently, research and development concerning application of the conduction-cooled HTS SMES that is easily movement are actively progressing in Korea. Electrical insulation under cryogenic temperature is a key and an important element in the application of this apparatus. Using multi wrapped copper by Polyimide film for HTS SMES, the breakdown characteristics of models for turn-to-turn, that is surface contact model, were investigated under ac and impulse voltage at 77 K. A material that is Polyimide film (Kapton) 0.025 mm thickness is used for multi wrapping of the electrode. Statistical analysis of the results using Weibull distribution to examine the wrapping number effects on breakdown voltage under at and impulse voltage in $LN_2$ was carried.

• Journal of Korean Medical classics
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• v.19 no.2 s.33
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• pp.248-265
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• 2006

Impulse of ki refers to palpitation around the navel, it is mostly caused by impairment of yang due to erroneous sweating, deficiency of the spleen yang. Behcet's syndrome caused by prolonged damp-heat and pathogenic germs. Its symptoms are characterized by conjunctival congestion, blue canthus and ulceration of the oral cavity, restlessness all the time, etc. It is advisable to follow the therapeutic principles of clearing away heat and drying damp, detoxicating and sterilizing. Lily disease is one of the emotional disease. It caused by yin deficiency of the heart and lung, found in mental depression or convalescence after a critical disease. Its symptoms are characterized by restlessness, reticence, insomnia, failure to walk, poor appetite, a subjective hot or cold, bitter taste and dark urine. It is advisable to follow the therapeutic principle of nourishing yin to clear away heat. Cholera refers to the disease marked by sudden severe vomiting and diarrhea, and colic of the heart and the abdomen. It is mostly caused by deficiency of the ki in the middle-energizer, emotional stress, etc. It is characterized by such symptoms as sudden severe vomiting and diarrhea, restlessness, etc. It is advisable to follow the therapeutic principles of warming yang and removing toxic substances, and strengthening the spleen and stomach. Heat invasion of blood chamber due to affection of the exterior pathogens, pathogenic heat invading the blood in deficiency and fighting with the blood. Its symptoms are marked by fever, feeling of the fullness, etc. There are deficiency of blood, hot blood and stasis of blood. The different therapeutic treatment should be taken according to different types thereof.

• Explosives and Blasting
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• v.41 no.4
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• pp.1-8
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• 2023

On August 4, 2020, 2750 tons of ammonium nitrate stored in a storage warehouse at the Port of Beirut exploded. This explosion is said to be the largest ammonium nitrate explosion ever. By applying the TNT equivalency method, TNT equivalent amount corresponding to the explosion energy of 2750 tons of ammonium nitrate was calculated, and it is found to be 856 tons. Overpressure and impulse were calculated in a range up to 3600 m from the blast using the Kingery-Bulmash explosion parameter calculator tool. As the distance from the explosion center increases, the overpressure and impulse decrease exponentially, but the overpressure decreases more significantly, showing that overpressure is more affected by distance than the impact. As a result of applying the damage criteria to evaluate the effects of overpressure and impulse on the structure, the critical distances at which partial collapse, major damage, and minor damage to the structure occur are found to be approximately 500, 800, and 2200 m from the center of the explosion, respectively. The probit function was applied to evaluate the probability of damage to structures and human body. The points where the probability of collapse, major damage, minor damage, and breakage of window-panes to structures are greater than 50% are found to be approximately 500, 810, 2200, and 3200 m, respectively. For people within 200 m from the center of the explosion, the probability of death due to lung damage is more than 99%, and the 50% probability of eardrum rupture is approximately 300 m. The points with a 100% probability of death due to skull rupture and whole body impact due to whole body displacement are evaluated to be 300 and 100 m, respectively.

• Journal of the Korean Institute of Gas
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• v.12 no.1
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• pp.1-6
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• 2008

The notched Charpy impact test is one of the most prevalent techniques used to characterize the effect of high impulse loads on polymeric materials. In this study, a method of analysis in nylon plastic materials is suggested to evaluate the critical strain energy release rate for variation of notch angles from the Charpy impact energy measurement. Instrumented Charpy impact tester was used to extract ancillary information concerning fracture parameters in addition to total fracture properties and maximum critical load. The dynamic stress intensity factor of nylon plastic material was calculated for the ASTM Charpy specimen from the obtained maximum critical load. Also, the finite element model was developed to figure out the stress distributions for Charpy specimen with different notch angles subject to 3 point bending load which is equivalent to the load applied in the experiment.

• The Research Journal of the Costume Culture
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• v.22 no.2
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• pp.346-359
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• 2014

Black Friday, a biggest holiday shopping season in the United States, has been regarded as a great opportunity that fashion retailers can dramatically increase their sales. However, there has been a lack of attention to consumers' shopping experiences on Black Friday from the consumer perspectives. The objective of this study is to explore consumer shopping experiences on Black Friday, in terms of consumer responses toward the experiences, shopping values, and any possible factors influencing the experiences. The method of critical incident technique was used with 198 critical incidents extracted from 165 responses of university students in the United States. As results, the shopping experiences on Black Friday were categorized into positive vs. negative shopping experiences. After that, the positive and negative experiences were respectively divided into two common themes: utilitarian shopping value vs. hedonic shopping value. In addition to the common themes, 12 categories were also emerged. Among positive experiences, utilitarian shopping experiences includes two categories of off-price shopping and shopping for expensive products, whereas hedonic shopping experiences includes three categories of impulse buying, holiday atmosphere, and shopping for the latest or luxury brand products. Among negative experiences, utilitarian shopping experiences includes four categories of modest discounts, out of stock, time-consuming queues, and fatigue of holiday shopping, while hedonic shopping experiences includes three categories of crowded environments, compulsive buying, and poorly managed stores. In conclusion, it is notable that consumer can undergo negative as well as positive shopping experiences on Black Friday. Implications and suggestions are also discussed.

• Journal of Korean Critical Care Nursing
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• v.3 no.1
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• pp.29-40
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• 2010

Purpose: This study was to investigate Job Stress and the Health status of ICU Nurses. Methods: Data was accumulated from 230 ICU nurses serving at least more than one year in 500 bed order hospitals during the period of three months from June 1 to August 31, 2009. Results: The average job stress was $3.14{\pm}.59$ points, which was relatively high, The average health status was $1.52{\pm}.19$ points, There was significant difference according to religion and subjective health status in Job Stress, There was significant difference according to age, religion and subjective health status in Health Status, There was significant difference according to satisfaction of work, satisfaction of personal relations, impulse to give up duty and in service education in Job Stress, There was significant difference according to satisfaction of work. satisfaction of personal relations, and expectant nursing job in Health Status, There was significantly negative relationship between job stress and health status. Conclusion: Job stress has the most important impact on health status of ICU nurses, Based on the finding, we could conclude that job stress management of ICU nurses should be required to improve health status.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.846-851
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• 1995

A motor-integrated high-speed spindle system with .psi. 65*25, 000rpm is modeled for analytical and experimental studies related to the dynamic characteristics. And the systematic and rational identification processes for evaluating the material properties of spindle and built-in motor is introduced. The impulse excitation method is applied for the experimental model testing, and the dynamic characteristics of test model is theoretically analysed by using the finite element method based on Timoshenko theory. Especially, the experimental and theoetical results reveal that the test model under the required operational conditions has no critical problem for dynamic characteristics.

• The Journal of the Acoustical Society of Korea
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• v.16 no.1E
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• pp.15-23
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• 1997

Zero-Crossings with Peak Amplitudes(ZCPA) model motivated by human auditory periphery was proposed to extract reliable features speech signals even in noisy environments for robust speech recognition. In this paper, some practical considerations for digital hardware implementations of the ZCPA model are addressed and evaluated for recognition of speech corrupted by several real world noises as well as white Gaussian noise. Infinite impulse response(IIR) filters which constitute the cochliar filterbank of the ZCPA are replaced by hamming bandpass filters of which frequency responses are less similar to biological neural tuning curves. Experimental results demonstrate that the detailed frequency response of the cochlear filters are not critical to performance. Also, the sensitivity of the model output to the variations in microphone gain is investigated, and results in good reliability of the ZCPA model.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.305-308
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• 2008

This paper presents characteristics of soil ionization when high currents such as lightning and switching surge currents are injected into a grounding rod. Soil ionization phenomena are investigated by using both voltage and current signals recorded by oscilloscope. As a result, a critical electric field intensity($E_C$) for ionization is decreased with reduction of grain size. The pre-ionization resistance($R_1$) and post-ionization resistance($R_2$) at the sand with fine grain size are getting lower with increasing current magnitude. Finally, the time to ionization($t_1$) and ionization current peak($t_2$) of fine grain size are significantly shorter than those of medium grain size.