• The KIPS Transactions:PartC
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• v.15C no.6
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• pp.573-586
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• 2008

The improved performance and miniaturization of computer and the improvement of wireless communication technology have enabled the emergence of many high quality services. Among them multicast services are receiving much attention and their usage is increasing due to the increase of Internet multimedia services such as video conference, multimedia stream, internet TV, etc. Security plays an important role in mobile multicast services. In this paper, we proposed a secure multicast protocol for a hierarchical micro-mobility environment. The proposed secure multicast protocol provides security services such as authentication, access control, confidentiality and integrity using mechanisms including symmetric/asymmetric key crypto-algorithms and capabilities. To provide forward/backward secrecy and scalability, we used sub-group keys based on the hierarchical micro-mobility environment. With this security services, it is possible to guard against all kinds of security attacks performed by illegal mobile nodes. Attacks executed by internal nodes can be thwarted except those attacks which delete packet or cause network resources to be wasted. We used simulator to measure the performance of proposed protocol. As a result, the simulation showed that effect of these security mechanisms on the multicast protocol was not too high.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.2
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• pp.221-227
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• 2016

The main shaft is one of the key components connecting the rotor hub and gear box of a wind power generator. Typically, main shafts are manufactured by open die forging method. However, the main shaft for large MW class wind generators is designed to be hollow in order to reduce the weight. Additionally, the main shafts are manufactured by a casting process. This study aims to develop a manufacturing process for hollow main shafts by the open die forging method. The design of a forging process for a solid main shaft and hollow shaft was prepared by an open die forging process design scheme. Finite element analyses were performed to obtain the flow stress by a hot compression test at different temperature and strain rates. The control parameters of each forging process, such as temperature and effective strain, were obtained and compared to predict the suitability of the hollow main shaft forging process. Finally, high productivity reflecting material utilization ratio, internal quality, shape, and dimension was verified by the prototypes manufactured by the proposed forging process for hollow main shafts.

• Journal of Conservation Science
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• v.33 no.6
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• pp.519-532
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• 2017

Studies on ancient ironmaking technologies are primarily based on archaeological surveys and scientific analysis data, and technological systems are examined by comparing the results of restorative experiments. In this study, to examine the ancient iron production technologies such as smelting and smithing in the Jungwon area, a restoration experiment was conducted based on archaeological data, and the iron and slag, etc. produced in the experiment were analyzed. Further, the changes in physicochemical properties due to the smelting of the raw material, specifically, iron ore were determined, and the smithing process, which involves fabrication of ironwares, was analyzed along with the characteristics of each step. In the case of smelting, increasing recovery rates and production of high-quality primary iron material were important for the following processes. For the iron bars produced through the smithing process, it was found that quality improvements made by reducing physical defects such as inclusions or gas holes were more important than the composition of the iron itself. The study also yielded comparative study data for various byproducts, such as smithing slag, which could be utilized in other ironmaking technology studies.

• 한국가스학회:학술대회논문집
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• 2007.04a
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• pp.195-200
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• 2007

본 연구는 도심지에 위치한 LPG 충전소를 연구범위로 하여 공간정보의 활용이 가장 많이 요구되는 안전관리 분야의 업무를 중심으로 공간정보를 효율적으로 구축 활용하기 위하여 데이터베이스를 중심으로 위험관리정보 시스템을 개발하였다. 이를 바탕으로 정량적 위험성 평가의 자동화를 통해 나타난 위험성을 실시간에 제어하기 위한 필요조건을 표준화하여 기초 정보자료로 구축, 이를 지리정보기능과 연동하여 LPG 충전소의 안전검사의 효율화, 사전 위험성 평가, 사고대응 판단의 효과적인 의사결정을 유도 할 수 있는 기반을 제공한다. 위험관리정보시스템(RMIS, Risk Management Information System) 개발절차는 다음과 같다 첫째, 도심지에 위치한 LPG 충전소 위험성 평가를 수행함에 있어서 기본적인 데이터인 부지내(On-site) 관련 자료와 부지 외(Off-site) 관련 자료를 관계형 데이터베이스(RDB, Relational Database)로 개발하였다. 둘째, Visual Basic을 이용하여 사용자가 효과적으로 위험을 관리 제어 할 수 있는 위험관리 통합 데이터베이스 시스템 개발하였다. 셋째, 위험관리 통합 데이터베이스 시스템과 지리정보시스템에 연동을 통한 의사결정 방안 제시하였다. 위험관리정보시스템(RMIS) 프로그램을 개발을 통하여 다음과 같은 결과를 도출하였다. 첫째, 위험관리 데이터 이용하여 사용자와 검사자가 효과적으로 위험을 사전관리 할 수 있는 공유정보를 구축하였다. 둘째, 위험 관리를 부지 내와 부지 외로 나누어 관리함으로서 시설 내부 뿐 만 아니라 시설외부에 미치는 영향을 모두 고려하여 구축하므로 서, 중대사고에 대응 할 수 있는 종합적인 안전관리 기반을 조성하였다. 셋째, 사용자 인터페이스를 바탕으로 비상사태 발생시에 신속하고 정확한 의사결정을 할 수 있는 기반을 조성하였다. 제공하여 응용GIS 구축의 생산성 및 품질 향상에 기여할 뿐만 아니라 우리의 최종목표인 GIS 소프트웨어 자동 생산에도 크게 기여할 것으로 사료된다. 등)을 교통망상에 표시할 수 있음으로서 의사결정에 보다 많은 도움을 줄 수 있을 것이다. 비트율의 증가와 화질 열화는 각각 최대 1.32%와 최대 0.11dB로 무시할 수 있을 정도로 작음을 확인 하였다.을 알 수 있었다. 현지관측에 비해 막대한 비용과 시간을 절약할 수 있는 위성영상해석방법을 이용한 방법은 해양수질파악이 가능할 것으로 판단되며, GIS를 이용하여 다양하고 복잡한 자료를 데이터베이스화함으로써 가시화하고, 이를 기초로 공간분석을 실시함으로써 환경요소별 공간분포에 대한 파악을 통해 수치모형실험을 이용한 각종 환경영향의 평가 및 예측을 위한 기초자료로 이용이 가능할 것으로 사료된다.염총량관리 기본계획 시 구축된 모형 매개변수를 바탕으로 분석을 수행하였다. 일차오차분석을 이용하여 수리매개변수와 수질매개변수의 수질항목별 상대적 기여도를 파악해 본 결과, 수리매개변수는 DO, BOD, 유기질소, 유기인 모든 항목에 일정 정도의 상대적 기여도를 가지고 있는 것을 알 수 있었다. 이로부터 수질 모형의 적용 시 수리 매개변수 또한 수질 매개변수의 추정 시와 같이 보다 세심한 주의를 기울여 추정할 필요가 있을 것으로 판단된다.변화와 기흉 발생과의 인과관계를 확인하고 좀 더 구체화하기 위한 연구가 필요할 것이다.게 이루어질 수 있을 것으로 기대된다.는 초과수익률이 상승하지만, 이후로는 감소하므로, 반전거래전략을 활용하는 경우 주식투자기간은 24개월이하의 중단기가 적합함을 발견하였다. 이상의 행태적 측면과 투자성과측면의 실증결과를 통하여 한국주식시장에 있어서 시장수익률을 평균적으로 초과할 수 있는 거래전략은 존재하므로 이러한 전략을 개발 및 활용할 수 있으며, 특히, 한국주

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.535-541
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• 2020

FCAW is used mainly in the welding of carbon steel and alloy steel because it can be welded in all positions and can obtain excellent quality at sites with variable working conditions. Recently, many studies in Korea have estimated the fatigue strength, residual stress, and deformation, and to develop a fillet welding process. On the other hand, there have been few studies of the mechanical properties based on the strength, macro and magnetic particle test results for fillet welding. This study shows the following results through fillet welding, macro testing and strength testing using SM490A (solid-structure rolled steel) for thick plates using SS400 (rolled steel) for the upper plate and FCAW. The hardness test, macro test and magnetic particle test were then conducted. The hardness tests showed that all result values were smaller than the KS B 0893 standard values of 350Hv. The macro-test showed that each type of welded part was in a normal organic state and that there were no internal errors, bubbles, or impurities on the front of the welded part. Therefore, there were no concerns about lamination. The magnetic particle examination showed no problems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.417-422
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• 2017

One of the most frightening aspects of weapons of mass destruction (WMD) is their ability to cause death in very small quantities without being visible to the public. The military authorities are making considerable effort to ensure the survivability of the combatants in the event of NBC(Nuclear, Biological and Chemical) contamination. Therefore, in this study, modules were developed for the measurement of the positive pressure and for the detection of the chemicals used for the control of the various shut-off valves used in an NBC shelter. In addition, a high performance gas tight shut-off valve was developed that can overcome the disadvantages associated with manual manufacturing, such as the occurrence of defective products and high manufacturing cost. By applying the positive pressure measurement and chemical detection modules, this valve was able to be used to control the facility. The developed gas-tight shut-off valve maintained airtight characteristics at a pressure loss of 28[Pa] at the prescribed wind velocity and an internal pressure of 30[kPa]. It is expected to be possible to control the gas-tight shut-off valve through the remote measurement of the positive pressure, thereby ensuring the foreign independence of import substitution and defense related technology in the future. In addition, by installing these valves in all of the intake ports or exhaust ports connected to the outside of the NBC shelter, it is possible to prevent the damage resulting from the rapid inflow of the storm pressure caused by conventional weapons and nuclear explosions, thereby protecting the people and equipment in the shelter.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.474-480
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• 2018

FRP is a new material that is lightweight, has high strength and high durability, and is emerging as a third construction material in many countries. The composite material panel targeted in this study was a curved member and is the most frequently used arch-shaped member of a structures, such as tunnels. Composite curved panels can be produced in high quality and large quantities through automation operations. On the other hand, the frequency of application is low, and the design criteria and experimental data are lacking. Therefore, this study examined the mechanical performance of the member unit first to verify its performance as structural members of the FRP curved panel. For this purpose, tensile, compression, and connection performance tests were carried out. The tensile tests showed greater tensile strength of specimens with larger curvature, and the compression tests showed that the composite section of a composite material has greater compressive strength than the concrete section. Finally, the test of the performance of the connection showed that the attachment performance of the connection was more than equal to that of the FRP composite material panel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.648-655
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• 2020

The firing pin of modern automatic rifles detonates the primer of loaded ammunition via a hammer. During this process, the firing pin receives an impact load and repetitive force throughout the life of the rifle. An endurance test of a rifle showed that the firing pin breaks prematurely at 96.26% of life. Accordingly, a case study was conducted through cause analysis and a reconstruction test. Optical microscopy and scanning electron microscopy of the broken surface of the firing pin showed that a crack began in the circumferential direction of the surface, resulting in a fatigue crack to the core after repeated impact. Crack growth and fatigue destruction occurred at the end due to the repetitive impact and was estimated using a notch. For verification, a sample that produced a 0.03mm circumferential notch was broken at 64.25% of life in the reconstruction test. A test of breakage according to the notch types showed that a 0.3mm and a 0.5mm one-side notch were broken at 66.53% and 50.76%, respectively, and a 0.03mm six-point notch was broken at 85.65%. The endurance life of a sample firing pin with a rough surface and tool mark was examined, but an approximately 381 ㎛ internal crack formed. Through this study, failure for each notch type was considered. These results show that quality control of the notch and surface roughness is essential for ensuring the reliability of a component subjected to repeated impact.

• Food Science and Preservation
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• v.15 no.2
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• pp.209-213
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• 2008

We examined the dough properties, baking qualities, and sensory aspects of commercial hard wheat flour (Q1) that was supplemented with up to 30% rice bran flour. The loaf volumes of bread with 20% and 30% rice bran were 83% and 65% respectively, of the control (wheat flour only). However, a 5% and 10% supplement of rice bran increased loaf volume by 5.2% and 0.7% respectively, over the control. After storage of loaves for three days, bread crumbs from loaves with 5% rice bran were significantly softer than those with 10% 20% and 30% rice bran. The hardness of dough increased with the proportion of rice bran, but springiness and cohesiveness were inversely related to hardness. Addition of rice bran increased loaf pH. Rice bran decreased lightness, but significantly increased redness and yellowness in a concentration dependent manner. Sensory investigation indicated that bread with 5% rice bran was not significantly different from the control. However, more panel members preferred the appearance and flavor of bread with 5% rice bran.

• Food Science and Preservation
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• v.16 no.2
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• pp.139-146
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• 2009

Whole and stem-off cherry tomatoes were packaged using perforated films(LF05, LF10, LF20, and LF40). Gas composition(ethylene, $O_2$, and $CO_2$), firmness(compression and penetration force), color, brix degree, acidity, and total microbial counts were assessed during storage at $10^{\circ}C$ and 85% relative humidity. Gas composition varied with film gas permeability, indicating that modified atmospheric(MA) conditions were achieved. Firmness fell during storage; samples packed using LF05 showed the lowest firmness, corresponding to low gas transmission conditions. L(lightness) and a(redness) values respectively decreased and rose slightly with increasing storage time, but the b(yellowness) values fell notably. Film permeability significantly affected acidity and soluble solid levels. When LF40 packaging was used, acidity and brix scale changes were similar to those seen after PET container packaging. Total microbial counts increased with time after packaging in most films, and pretreatment differences were not significant. Microflora varied between stem on/off tomatoes. Skin wrinkling and juice appearance were common in tomatoes stored in PET containers and LF films of low gas permeabilities(LF05, LF10, and LF20). White molds were partially found on stem-on tomatoes stored using packaging systems. When film packagings were compared, LF40 was optimal, permitting minimal pretreatment yet offering maximal sanitation.