• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.5
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• pp.359-365
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• 2022

Air-to-ground missile(AGM), which can be operated by being mounted on the outside of the aircraft, is capable of precision strikes, ensuring high survivability. Helicopter, which is one of the AGM operating platforms, is reported to experience a lightning strike once between 1000 and 20000 flight hours in average. When the lightning strikes the helicopter fuselage, lightning transient signal can be induced to internal and external electronic equipment cables through the skin of the helicopter. If the transient signal exceeding the criteria to electrically initiated device(EID) related to the explosive in the AGM can affect the safety of the helicopter by a warhead explosion, etc. In this paper, we suggest an indirect lightning test method to prove the safety of AGM on helicopter, and present the indirect lightning test results.

• Journal of Yeungnam Medical Science
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• v.39 no.1
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• pp.31-38
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• 2022

Background: To prepare for future work stoppages in the medical industry, this study aimed to identify the effects of healthcare worker strikes on the mortality rate of patients visiting the emergency department (ED) at six training hospitals in Daegu, South Korea. Methods: We used a retrospective, cross-sectional, multicenter design to analyze the medical records of patients who visited six training hospitals in Daegu (August 21-September 8, 2020). For comparison, control period 1 was set as the same period in the previous year (August 21-September 8, 2019) and control period 2 was set as July 1-19, 2020. Patient characteristics including age, sex, and time of ED visit were investigated along with mode of arrival, length of ED stay, and in-hospital mortality. The experimental and control groups were compared using t-tests, and Mann-Whitney U-test, chi-square test, and Fisher exact tests, as appropriate. Univariate logistic regression was performed to identify significant factors, followed by multivariate logistic regression analysis. Results: During the study period, 31,357 patients visited the ED, of which 7,749 belonged to the experimental group. Control periods 1 and 2 included 13,100 and 10,243 patients, respectively. No significant in-hospital mortality differences were found between strike periods; however, the results showed statistically significant differences in the length of ED stay. Conclusion: The ED resident strike did not influence the mortality rate of patients who visited the EDs of six training hospitals in Daegu. Furthermore, the number of patients admitted and the length of ED stay decreased during the strike period.

• The Southeast Asian review
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• v.19 no.1
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• pp.67-111
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• 2009

지난여름 베트남 남부의 호치민시와 인근의 공장지대는 전례 없는 파업의 확산을 경험했다. 연구자가 만난 한국기업의 매니저들은 이를 "파업의 도미노 현상"으로 묘사했다. 호치민시 노동조합의 고위간부는 "도이머이(Doi Moi) 이후 노사관계에 가장 혼란스러운 변화가 일어나고 있다"라고 단언하기도 했다. 본 연구는 한국계 다국적 공장을 사례로 1) 최근 파업의 정치경제학적 배경은 무엇인지를 살펴본 다음, 2) 왜 어떤 공장은 최근의 파업의 소용돌이 속에서 상대적으로 안전했던 반면 다른 기업은 그렇지 못했는지, 3) 왜 어떤 공장은 파업의 과정에서 협상을 성공적으로 이끈 반면 다른 기업은 그렇지 못했는지, 4) 최근의 파업이 개별 다국적 공장의 체제에 어떤 사회적, 문화적, 정치적 영향을 미쳤는지 살펴보고자 하였다. 연구자는 연구목적을 위하여 호치민 인근과 동나이에 위치한 약 20여개의 공장을 방문하였으며 서로 다른 특징을 가지고 있는 3개의 섬유공장을 선별하여 현지연구를 실시하였다. 이 가운데 첫 번째 공장은 연구자가 90년대 말 현지연구를 실시하여 공장체제의 성격을 잘 알고 있는 다국적 공장이었다. 나머지 두 공장은 재정 상황과 정치과정의 특징이 첫 번째 공장과 대조될 뿐 아니라 서로 다른 공장이었다. 세 공장을 비교 연구함으로써 연구자는 다국적 공장의 재정적 혹은 경제적 상태가 노동쟁의의 성격을 만드는 주요한 조건이 되지만, 회사의 경제적 조건이 양호하고 경영진이 온정주의적 철학을 실천하고 있다고 해서 파업을 미연에 방지할 수 없다는 점을 보여주고자 하였다. 호치민 인근의 파업이 크게는 세계적인 경제위기, 작게는 회사의 재정상태에 영향을 받고 있지만 특정 공장에서 노동쟁의가 일어나는가의 여부는 이 공장의 정치과정과 레짐의 성격에 의해 좌우된다는 점을 밝히고자 했다. 특히 다국적 공장의 정치과정의 안정을 위해서는 '매개자' 역할을 하는 베트남 중간간부, 사무실 직원, 노조간부 등의 역할이 매우 중요하였다. 이들이 위계적으로 그리고 사회문화적으로 다른 외국인 경영진과 공장 노동자의 갈등을 어떻게 흡수하고 중재하는가에 따라 공장체제의 안정 여부가 달려 있었다. 이번 파업은 각각 다른 정치경제적 조건을 가진 여러 공장의 경영진과 노동자가 이러한 사실을 새삼 깨닫게 하는 계기로 작용했다.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.35-45
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• 2023

In this paper, we analyze the influence of indirect lightning strikes based on the structure of shielded cables used in an aircraft and propose a cable structure to enhance shielding effectiveness. Cables in an aircraft account for the largest proportion among components and play a crucial role in connecting aircraft frames and electronic devices; thus, making them highly influential. In particular, indirect lightning strike noise can lead to malfunctions and cause damage in aircraft electronic equipment, making the utilization of shielded cables essential for mitigating damage caused by indirect lightning strike noise. We conducted an analysis of the impact of indirect lightning strikes on aircraft shielded cables considering factors, such as the presence of shielding layers, core, and insulation in the cable structure. Furthermore, we validated our findings through simulations and experiments by applying the internationally recognized standard for indirect lightning, RTCA DO-160G Sec. 22.

• Journal of Wind Energy
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• v.14 no.4
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• pp.50-56
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• 2023

With the abnormal weather phenomena caused by global warming, the frequency and intensity of lightning strikes are increasing, and lightning accidents are becoming one of the biggest causes of failures and accidents in offshore wind turbines. In order to secure generator operation reliability, effective and practical measures are needed to reduce lightning damage. Because offshore wind turbines are tall structures installed at sea, the possibility of direct lightning strikes is very high compared to other structures, and the role of surge protection devices to minimize damage to the electrical and electronic circuits inside the wind turbine is very important. In this study, a varistor, which is a key element for a class 1 surge protection device for direct lightning protection, was developed. The current density was improved by changing the varistor composition, and the distance between the electrode located on the varistor surface and the edge of the varistor was optimized through a simulation program to improve the fabrication process. Considering the combined effects of heat distribution, electric field distribution, and current density on the optimized varistor surface, silver electrodes were formed with a gap of 0.5 mm. The varistor developed in this study was confirmed to have an energy tolerance of 10/350 ㎲, 50kA, which is a representative direct lightning current waveform, and good protection characteristics with a limiting voltage of 2 kV or less.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.339-346
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• 1999

The stability of rock slope is considered to have a deep relation with types of rocks because types of rocks have their own typical weathering profiles, geological structures and characteristics of failures. Therefore it is essential for the evaluation of rock slope stability to analyze geological and engineering characteristics in rock mass. The data which collected from investigated slopes in sedimentary rock of Kyengsang Basin along highways were analyzed. Primary factors affecting slope stability in rock mass are: dips and strikes of slopes and discontinuities, shear strength of discontinuities, slope geometry and geological structures etc.

• Economic and Environmental Geology
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• v.2 no.2
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• pp.53-67
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• 1969

Magnetite deposit of Pocheon Iron Mine is a contact replacement skarn deposit embedded in the carbonate rocks (limestone and dolomite) which are intruded by granite porphyry. The shape of ore bodies is sweet potato-like and/or irregular massive form; D-ore body, the biggest one is of $180m{\times}40m{\times}200m$ in size. The ore is in general of high grade. The location of the ore bodies is controlled by the fault which strikes north south and dips $60^{\circ}$ to $70^{\circ}$ to the west. A regular distribution of mineralized zones is recognized in order of outward (hanging wall side) from granite porphyry as follows: compact fine-grained skarn, limesilicates, magnetite ore body, marble, limesilicates, pyritized meta-sediments.

• Journal of the Korean Society of Marine Environment & Safety
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• v.6 no.1
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• pp.77-83
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• 2000

En coastal area, many submarine facilities such as pipes and cables are installed on/under the sea bed. Also, there are heavy traffic due to numerous vessels which call in ports or navigate passages in adjacent water. Therefore, the frequency of dropping anchors will be increased to avoid various dangerous situations. When an anchor is dropped from vessel on the sea bed, the anchor strikes on the sea bed, and then, the anchor penetrates to certain depth into the sea bed. In this case, sometimes submarine facilities on/under the sea bed may be damaged by the strike or the maximum penetrating depth of anchor. In this paper, some approximate equations on the strike and the penetrating depth of anchors have been derived on the basis of actual data, and the results are expected to use as basic design data of related facilities.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.3
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• pp.472-480
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• 2007

This paper analyzes overvoltage on testing line for various parameter effect examination. Model systems consist of overhead line and underground cable. The model considered actual characteristic data of distribution lines. and will be constructed at testing yard. The simulations were performed under various line configuration such as cable kinds, cable length, lightning wave, lightning wave time, transformer and branch circuits. The simulation models are established by EMTP/ATPDraw and Line Constants are calculated by ATP_LCC. When lightning surge strikes on conductor of overhead line, EMTP/ATPDraw calculates overvoltage in many cases. Simulation results will be compared with real testing results at testing yard. The compared results will be used to establish protection methods in actual underground distribution systems.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1265-1270
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• 2018

One of the ways to improve the stability of power facilities used in power systems is to use power surge arresters and to protect against transient overvoltages and surges in normal operation. Also it is important to reduce the impact of lightning strikes because lightning can create overvoltage in the grid of the wind turbine and affect power quality. So This paper analyzes the effects of overvoltage and adjacent turbines due to single strike and multi strike to ground impedance changes when the surge arrester is deteriorated in a wind power farm.