• 융합신호처리학회논문지
• /
• 제9권4호
• /
• pp.329-336
• /
• 2008

최근 발전소의 첨단기술을 적용한 설비들이 대형화되고, 발전기의 정지나 사고 등으로 막대한 유지보수 비용을 필요로 하고 있다. 따라서 이러한 기계설비들의 운전 상태를 감시하고 고장을 예측할 수 있는 새로운 진단장치의 개발이 요구된다고 본다. 본 연구는 이러한 점에 착안하여 기계들의 정상/비정상 운전 상태를 정상레벨/비정상레벨/주의레벨/위험레벨/고장 즉 5단계로 세분화하고 각 단계별 판별기준을 정하여 운전 중 발생하는 기기들의 신호를 취득 및 분석하여 기기들의 정지 없이 기기의 운전 상태를 실시간 판별할 수 있는 시스템을 개발한다. 이를 위하여, 영역분할 알고리즘에 기반하여 기기의 운전 상태를 주파수특성 행렬로 표시하는 방법을 고안하였다. 각 기기들의 운전 상태를 간략히 피크코드화하고, 이 피크코드를 바코드처럼 활용할 수 있도록 발전설비 기기에 부착함으로서 기기의 운전상태 관리를 시스템화 할 수 있도록 하였다. 5단계 중 주의레벨에서 기기들의 예방정비를 수행하여 발전소의 경제적이고 안정적인 운전효율을 높이는 것이 궁극적 목표이며, 현장 적용 시의 이동성을 고려하여 노트북 컴퓨터로 신호취득에서 판별까지 가능하도록 알고리즘을 개발하였다.

• 한국식생활문화학회지
• /
• 제19권3호
• /
• pp.336-347
• /
• 2004

This study was conducted to investigate eating-out behavior patterns of youths, especially junior high and senior high school students. 1600 questionnaire surveys were distributed and 1487 were used for analysis. In order to consider regional differences as well as overall characteristics of youths' eating-out behaviors, the subjects were evenly sampled from north Seoul, south Seoul, big cities, middle/small cities and small towns. As for the frequency of eating-out, 62.7% of respondents answered once to twice per week. For the can of more than 5 times of eating-out per week, the respondents from south Seoul showed the highest frequency. For the case of no eating-out, the highest frequency was shown from the small towns. As for the most frequently visited place for eating-out, 33.6% of respondents answered Korean style restaurants, and 17.6% Boon-sik(Sanck-bar). Regarding the preference of Korean style restaurants, the highest rate was shown from the residents of big cities. For the question of when they eat out, 89.6% answered dinner and 6.3% lunch. For the question about reason of choosing particular restaurants, 61.5% of respondents referred to tastes and 16.6% price. For the question of the most important reason of eating out, 52.6% point out 'meal solution' and 25.6% 'for meeting.' As for the people accompanied when eating out, 67.2% of the respondents answered family. For the cost of eating out per person, 45.7% of the respondents spent 2000-4000 won for lunch; 31.1% spent 5000-10,000 won for dinner; 33.7% of the respondents spent more than 20,000 won for the special events. Regarding the regional differences of eating-out cost, respondents from south Seoul tended to spend the biggest amount of money for lunch, dinner and special day.

• 한국정보시스템학회지:정보시스템연구
• /
• 제15권3호
• /
• pp.187-211
• /
• 2006

As port competitiveness is becoming more important in the global market environment RFID (Radio Frequency Identification) Is also becoming a crucial enabler In implement efficient visible, secure and productive ports. However there Is a lack of practical validated RFID technology acceptance cases in the port logistics industry until now, even though various related projects have been undertaken. In this study, we applied 13.56MHz passive RFID readers, tags, and their applications into existing bar-code based gate systems to improve the port logistics process, and we analyzed results of a pilot test in economic and non-economic perspectives. The main purpose of this study is to develop the RFID based automatic gate passing system in container terminals, and is to validate its economic and non-economic feasibility. In order to accomplish the purpose of this study, first, we examined previous researches on RFID technology acceptance in the port logistics industry, second, we Identified and analyzed the business process of existing gate systems in container terminals, third, we build RFID gate systems with 13.56Mhz tags, readers, and its middle-ware, finally we tested the system and its performance. The results were successful and showed the feasibility of the system in real container terminal gates. Economic and non-economic contribution was confirmed. Although the system has technological limitations with short range passive type, we clearly identified its potential capability and its economic validity in the field, which are the implications of this study.

• Korea-Australia Rheology Journal
• /
• 제19권4호
• /
• pp.233-242
• /
• 2007

We performed a numerical investigation to find out the optimal choice of the spatial discretization in the distributed-Lagrangian-multiplier/fictitious-domain (DLM/FD) method for the solid/fluid interaction problem. The elastic solid bar attached on the bottom in a pressure-driven channel flow of a Newtonian fluid was selected as a model problem. Our formulation is based on the scheme of Yu (2005) for the interaction between flexible bodies and fluid. A fixed regular rectangular discretization was applied for the description of solid and fluid domain by using the fictitious domain concept. The hydrodynamic interaction between solid and fluid was treated implicitly by the distributed Lagrangian multiplier method. Considering a simplified problem of the Stokes flow and the linearized elasticity, two numerical factors were investigated to clarify their effects and to find the optimum condition: the distribution of Lagrangian multipliers and the solid/fluid interfacial condition. The robustness of this method was verified through the mesh convergence and a pseudo-time step test. We found that the fluid stress in a fictitious solid domain can be neglected and that the Lagrangian multipliers are better to be applied on the entire solid domain. These results will be used to extend our study to systems of elastic particle in the Stokes flow, and of particles in the viscoelastic fluid.

• 한국정밀공학회지
• /
• 제17권4호
• /
• pp.220-225
• /
• 2000

This paper develops a finite element model for studying occupant behavior of a mid-size truck equipped with a driver side airbag. The developed model simulates an occupant behavior using PAM-CRASH/PAM-SAFE in super computer SP2. The model is developed based on a sled test. A 50% hybrid dummy III is used for measuring head and chest accelerations and femur loads, and major injury coefficients such as HIC, CA and femur load. Inferior components such as foot rest, seat, kneebolster, crash pad, etc. are roughly modeled and defined by a rigid material model. And contact type II is used for detecting a contact with dummy. Contact type II definition uses force-deflection relationship of each body Such components as steering column which directly affect on the occupant injuy are modeled in detail and defined by an elastic-plastic material model. Airbag cushion is modeled using rivet elements. Airbag cover groove is modeled using rivet elements. Airbag tether is modeled as nonlinear bar elements. Airbag model has two vent holes to ventilating the exploded gas. Airbag is folded close to the real airbag folding procedure, and folded cautiously in order not to have initial penetration. A vehicle pulse acquired from 31mph frontal barrier test is used as input signal for the simulation. The simulation conditions are tuned to the sled test ones. The measured dummy accelerations and major injury coefficients, and filmed dummy behavior and airbag inflation process using high speed camera are compared to the simulation results to verify the developed finite element model.

• 대한토목학회논문집
• /
• 제31권4A호
• /
• pp.279-286
• /
• 2011

FRP 긴장재는 PS 강연선의 부식 문제를 해결하기 위한 대안으로써 사용될 수 있으며, FRP 긴장재의 재료특성(부착강도, 인장강도, 전달길이 등)은 구조물에 적용하기 위해서 결정되어야 한다. 재료특성 중에 부착은 FRP 긴장재로 긴장된 PSC 구조물에 적용하기 위해 명확하게 요구되어야 한다. 이 연구는 다양한 표면형상을 갖는 FRP 보강재의 부착특성을 연구하였다. 콘크리트의 철근과 강연선 대신에 사용되는 FRP 재료의 부착특성을 결정하기 위해 CAN/CSA S806-02에서 제안된 직접인발 시험을 수행하였다. 강연선, 이형 철근, 6가지 다른 표면 형상을 갖는 탄소 또는 유리섬유 FRP 보강재에 대하여 총 40개의 시편이 제작되었다. 부착실험 결과 각 실험체의 다양한 부착응력-슬립 곡선을 나타냈고, 국내에서 제작된 CFRP 긴장재의 부착특성과 비교하였다.

• Journal of Advanced Marine Engineering and Technology
• /
• 제29권8호
• /
• pp.891-898
• /
• 2005

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint race, and energy required lot welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy amount of upset. working time, and residual stresses in the joint. Inertia welding was conducted to make the large exhaust valve spindle for low speed marine diesel engine. superalloy Nimonic 80A for valve head of 540mm and high alloy SNCrW for valve stem of 115mm. Due to different material characteristics such as, thermal conductivity and flow stress. on the two sides of the weld interface, modeling is crucial in determining the optimal weld geometry and Parameters. FE simulation was performed by the commercial code DEFORM-2D. A good agreement between the Predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters. especially for welds for which are very expensive materials or large shaft. Many kinds of tests, including macro and microstructure observation, chemical composition tensile , hardness and fatigue test , are conducted to evaluate the qualify of welded joints. Based on the results of the tests it can be concluded that the inertia welding joints of the superalloy exhaust valve spindle are better properties than the material specification of SNCrW.

• 한국농림기상학회지
• /
• 제8권4호
• /
• pp.270-274
• /
• 2006

본 연구에서 고안 설계한 적설 관측용 수위 센서는 야외에서 일 변화량은 0.1 mm 내외의 적은 양의 오차를 기록하여 강설관측 센서로 적합한 것으로 판명되었으며, 실내 검정 결과 기상청에서 요구하고 100 mm의 강수 검정범위에 대해서 1%이하의 신뢰성 있는 검정결과를 나타내어 강설량 관측에 적합한 것으로 판명되었다. 또한 $-20^{\circ}C$의 테스트에서도 0.1 mm에 해당하는 아주 작은 변화 값을 타나내어 겨울철 야외환경에도 적합한 것으로 판명되었다. 깔때기가 없으며 수수구의 크기에 제한을 받지 않는 새로운 강수 관측구조는 적은 양의 강설관측이 가능하여 겨울철 예보에 필요한 레이다. 영상과 위성 영상에 의한 강설 연구와 해석에 많은 도움을 줄 수 있을 것이다. 또한 적설상당수량 관측이 가능하여 수자원 분야의 연구에도 많은 도움이 될 수 있다. 부동액을 사용하므로 고체 상태의 강설에 대해서 직접 관측이 가능하여 강설 관측에 있어 문제점으로 지적이 되고 있는 신적설 관측의 어려움을 해결할 수 있으며, 추후 야외 관측용 모델을 제작하여 야외 환경에서 여타 장비들과 비교 실험을 통해서 성능을 검정하고 개선할 계획이다.

• Journal of Biosystems Engineering
• /
• 제34권1호
• /
• pp.21-29
• /
• 2009

A rapeseed reaping equipment attachable to a conventional combine was developed in order to harvest rapeseed for bio-diesel materials. This study was carried out to measure the harvest feasibility of a prototype combine in rapeseed fields. Grain, stem and pod flow rate, grain qualities (whole kernel, damaged kernel, unhulled kernel, material-other-than-grain) and grain loss rates (header, threshing, separation) were investigated in each field test. As the result of the fold test, the average grain flow rates of SUNMANG and MS varieties showed 1,430 kg/h and 2,038 kg/h, respectively. The average stem and pod flow rates showed 3,443 kg/h and 6,596 kg/h, respectively. In each working speed, the average whole kernel rate and the material-other-than-grain showed 99.9% and below 0.08%, respectively. In the average grain loss, the rates showed 5.66% in case of SUNMANG and 5.94% in MS. Header loss was higher than other parts for SUNMANG. However, threshing loss was relatively higher than other parts for MS. Header loss rate due to side cutter knifes, however, was not so high when compared with a grain loss due to the cutter bar. Effective field capacity and field efficiency of the prototype combine showed 0.389 ha/h and 44%, respectively. Comparison of customary combine with the prototype combine through field test demonstrated that the header loss was reduced by 69.3% when the prototype combine was used.

• 정보관리학회지
• /
• 제34권4호
• /
• pp.127-152
• /
• 2017

다양한 분야에 걸쳐 생산성과 경쟁력 강화를 위한 IT활용 방안 중 하나인 RFID 기술은 바코드 시스템을 대체하고 시스템 이용에 보다 편리함을 가져올 기술로 주목받고 있다. RFID시스템은 이미 도서관을 비롯한 일부 기록관에도 적용되어 있으며, 한층 효과적인 기록관리 시스템 개발에 진보를 가져올 것으로 기대 받고 있다. 그러나 아직 시스템은 도입 초기단계에 놓여있고, 사소한 문제점과 불안전한 요소를 포함하고 있어 기록관 도입에 어려움을 겪고 있으며 시스템의 구체적인 문제를 파악한 연구는 이루어지지 않고 있다. 본 연구에선 이러한 점에 착안하여 RFID기반 기록관리체계를 운영하고 있는 기록관의 실무 담당자들을 대상으로 인터뷰 및 설문조사를 실시하였다. 이를 바탕으로 현재 기록관에서 운영 중인 RFID기반 기록관리체계의 운영 현황을 파악하고, RFID기반 기록관리체계의 문제점을 도출하여 이를 통해 효율적 운영방법에 있어 개선방안을 제시해보고자 한다.