• 한국자동차공학회논문집
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• 제22권2호
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• pp.166-174
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• 2014

Fuel injection pressure has steadily increased in diesel engines for the purpose of improving fuel efficiency and cleaning exhaust gas, but it has now reached a point, where the cost for higher pressure does not warrant additional gains. Common rail systems on modern diesel engines have fuel pumps that are mechanically driven by crankshaft. The pumps actually house two pumping module inside: a low pressure pump component and a high pressure pump component. Part of the fuel compressed by the low pressure component returns to the tank in the process of maintaining the pressure in the common rail. Since the returning fuel represents pumping loss, fuel economy improves if the returned fuel can be eliminated by using a properly controled electrical fuel pump. As the first step in developing an electrical fuel pump the fuel supply system on a 6 liter diesel engine was modeled with AMESim to analyze the workload and the fuel feed rate of the injection pump, and the results served as basis for selecting a suitable servo motor and a reducer to drive the pump. A motor controller was built using a DSP and a program which controls the common rail pressure using a proportional control method based on the target fuel pressure information from the engine ECU. A test rig to evaluate performance of the fuel pump is implemented and used to show that the newly developed electrically driven fuel pump can satisfy the fuel flow demand of the engine under various operating conditions when the rotational speed of the pump is adequately controlled.

• 한국정밀공학회지
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• 제23권2호
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• pp.199-206
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• 2006

Automatic grease lubricator is equipment that provides adequate amount of fresh grease constantly to the shaft and the bearings of machines. It minimizes the friction heat and reduces the friction loss of machines to the least. This research is to develop automatic grease lubricator by gear driven mechanism with controlled operation time. The ultimate design of this equipment is to lubricate an adequate amount of grease by a simple switch clicking according to the advanced set cycle. The backlash of the gear was minimized to increase the output power. To increase the power of gear mechanism, the binding frequency and the thickness of the coil were changed. To control the rotating cycles of the main shaft according to its set numbers, different resistance and chips were used to design the circuit to controls electrical signals with pulse. The body of the lubricator was analyzed by stress analysis with different constructed angle. The stress analysis for differing loading pressures applied to the exterior body of grease lubricator due to the setup angle, was found that the maximum stress was distributed over the outlet part where the grease lubricator suddenly narrowed contracts. Digital mock-up was analyzed and the rapid prototyping(RP) trial products were tested with PCB circuit and grease. The evaluation of the outlet capacity for RP trial products was conducted, because the friction caused by the outlet on the wall surface was an important factor in the operation of the equipment. Finally, the finishing process was applied to decrease the roughness of the surface to a comparable level and was able to test the performance examination for the product.

• Journal of Welding and Joining
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• 제28권5호
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• pp.75-79
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• 2010

The Remote welding system(RWS) using $CO_2$ laser equipment has focusable distance of laser beam longer than 800 mm from workpiece and can deflect the laser beam by the scanner mirrors very rapidly. In the case of normal welding system based on robot, there is a limit to move the shortest path in short time and this causes interference between robot and workpiece. On the other hand, RWS is the optimized equipment to get big merits with advanced sequence of welding and short cycle time. However, there is still a pending task such as the control of plasma in the welding process of thick sheets therefore, it requires high power laser beam because of the absence of assist gas equipment in itself. In this study, high-tensile steel plates were overlap welded with $CO_2$ RWS for the production of car body and the influence of penetration depth according to the existence of assist gas was analyzed. Excellent tensile strength with enough width of molten zone independent to penetration depth was observed under welding condition with 3.6 kW laser power and 2.8 m/min welding speed without assist gas. Finally, the proto-type automotive parts were produced by applying the deduced optimal welding condition.

• Journal of Biosystems Engineering
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• 제39권1호
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• pp.21-33
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• 2014

Background: Significant technological development and changes happened in the tractor industries. Contrariwise, the test procedures of the major standard development organizations (SDO's) remained unchanged or with a little modification over the years, demanding new tractor test standards or improvement of existing ones for tractor performance, safety, and comfort. Purpose: This study focuses on reviewing the research trends regarding performance, safety and comfort evaluation of agricultural tractors. Based on this review, few recommendations were proposed to revise or improve the current test standards. Review: Tractor power take-off power test using the DC electric dynamometer reduced human error in the testing process and increased the accuracy of the test results. GPS signals were used to determine acceleration and converted into torque. High capacity double extended octagonal ring dynamometer has been designed to measure drawbar forces. Numerical optimization methodology has been used to design three-point hitch. Numerous technologies, driving strategies, and transmission characteristics are being considered for reducing emissions of gaseous and particulate pollutants. Engine emission control technology standards need to be revised to meet the exhaust regulations for agricultural tractors. Finite Element Analysis (FEA) program has been used to design Roll-Over Protective Structures (ROPS). Program and methodology has been presented for testing tractor brake systems. Whole-body vibration emission levels have been found to be very dependent upon the nature of field operation performed, and the test track techniques required development/adaptation to improve their suitability during standardized assessment. Emphasizes should be given to improve visibility and thermal environment inside the cab for tractor operator. Tractors need to be evaluated under electromagnetic compatibility test conditions due to large growing of electronic devices. Research trends reviewed in this paper can be considered for possible revision or improvement of tractor performance, safety, and comfort test standards.

• 한국건설관리학회논문집
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• 제10권2호
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• pp.34-45
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• 2009

우리나라 건설공사의 품질관리체계는 관련법에 근거한 규정의 조합과 시공자가 구축한 ISO/KS A 9001에 의한 품질경영 시스템의 운용에 의한 방법의 혼합형이다. 이 두 가지의 품질확보체계는 상호 보완적이며 통합된 체계로 운영되어야 하나, 시공자의 품질경영시스템을 활용하지 못하고 법에서 정한 기준과 방법, 절차 등의 규정에 따라 모든 공사에 있어서 일상화된 품질관리업무가 수행되고 있다. 이러한 현상은 ISO규격이 도입된 이래 지난 10여 년간 계속된 문제점으로 개선이 요구되고 있다. 품질관리의 철저를 목표로 고객 만족을 위한 예방적 품질관리사고를 정착하는 일은 건설산업의 당면과제이다. 이에 본 논문에서는 건설현장 의 실무자를 대상으로 품질관리 관련 의식에 관한 설문조사를 실시하였으며 그 결과를 토대로 건설공사 품질관리 체계의 운용에 대한 만족도를 정리하고, 나아가 향후의 개선방안에 대한 논점을 제시하고자 한다.

• 한국세라믹학회지
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• 제42권11호
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• pp.749-752
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• 2005

When an electric field higher than a characteristic coercive field is applied to a ferroelectric such as $LiNbO_3$, the orientation of the spontaneous polarization is reversed, which causes the reversal of the sign of odd-rank tensor properties such as electro-optic and nonlinear optic coefficients. A fabrication process of insulator and periodic external field assisted poling of a z-cut $LiNbO_3$ have been optimized for a periodic $180^{\circ}$ phase inversion along z-axis. The poling jig and the poling control system, fully controlled by a computer, for high quality and reproducible PPLN fabrication have been devised. Periodically polarization reversed PPLN was adjusted based on the fabricated thickness of insulator. The poling structure of PPLN was observed under a microscope after etching PPLN samples by an etching solution ($HF:HNO_3$ = 1 : 2) for about 15 min.

• Journal of Welding and Joining
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• 제31권2호
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• pp.26-29
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• 2013

마찰교반용접(FSW) 및 마찰교반처리(FSP) 기술 관련 국제 심포지움인 'Friction Stir Welding & Processing VII'에서 발표된 연구논문의 내용을 토대로 아래와 같이 최신 연구개발 동향을 정리하였다. ${\cdot}$ 알루미늄합금과 마그네슘합금의 경량금속에 대한 마찰교반용접이 주류를 이루었던 과거와 달리 최근에는 구조용 연강, 고강도강, 초내열합금 및 타이타늄 합금 등의 고융점 금속재료에 대한 마찰교반용접 공정기술 및 툴의 개발이 수행되고 있다. ${\cdot}$ 주조재 표면 조직의 균질화 및 나노 사이즈의 초미세 결정립 조직을 얻기 위한 개질(改質)을 비롯하여 CNTs 및 Graphene 등의 첨단 탄소소재를 판재의 표면에 코팅 또는 판재 내부에 분산시켜 금속기 나노탄소복합재(MMNCC: Metal Matrix Nano Carbon Composites)의 제조 및 기계적 특성 향상을 목적으로 하는 FSP 관련 연구가 다각적으로 수행되고 있다. ${\cdot}$ 마찰교반용접 공정 중의 접합부의 형성 및 금속유동(Metal flow)에 대한 모델링(Modeling) 관련 연구가 다수 진행되고 있으며, 수학적 해석 및 실시간 모니터링을 통한 연구가 의욕적으로 진행되고 있다.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2008년도 정기학술발표대회 논문집
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• pp.729-732
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• 2008

건설공사의 규모와 설계 및 시공 방식이 다양하고, 규모가 확대됨에 따라 공사수행을 위한 초기 정보 획득 및 건설공사의 자동화의 실현을 위하여 RFID 기술을 적용할 수 있다. 건설 정보의 부족은 건설 자재 낭비, 작업률의 감소, 잘못된 정보로 인한 공정의 재수행, 건설 안전 사고등 전체 프로젝트의 비용적 시공성적 문제성을 야기한다. 이에 따라 본 연구는 IEEE 802.15.4a 혁신 무선 기술을 사용한 무선 공유 시스템과 RFID 시스템의 연계를 통한 향후 현장 시연 및 관련 문헌 조사, 현황 파악등을 통하여 RFID의 건설 현장 적용을 확인하고 건설 자동화를 위한 일환으로 자동화 건설 굴삭기 개발 등 건설 시공법 발전을 위하여 기여할 것이다. 이를 위해 RFID 시스템의 분석과 RTLS 와의 연동 방안을 제안하였다.

• 한국콘텐츠학회논문지
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• 제8권9호
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• pp.84-93
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• 2008

2005년부터 장편 3D 애니메이션 제작의 세계적인 증가추세와 하드웨어와 소프트웨어의 기술적 진보가 시각적 표현의 한계치를 넘어설 정도가 되면서 전체 작업 공정 중에서 렌더링(rendering)이 차지하는 비중이 더욱 중요하게 되었다. 렌더링 직전의 최종 파일은 데이터의 크기가 증가하는 문제가 발생한다. 이것은 수정 작업 시에 대용량 파일을 불러오고 저장하는 불필요한 소요시간과, 수정할 부분 외에 전체적으로 다시 렌더링을 수행하게 되는 시간을 소모하게 만든다. 본 논문에서는 연구 방법으로 Maya API를 활용하여 렌더링 레이어들의 정보 수정 방법을 연구하고 이를 적용하여 렌더링을 실행하는 Tool을 구현하는 것이다. 연구결과, 상업적인 애니메이션 제작에서는 제작 일정의 준수는 매우 중요하다. 그러므로 수정 작업에서 효율을 극대화 할 수 있기 위하여 독립적인 렌더링 툴 기반의 레이어 렌더링 구현이 필요하다고 판단된다.

• 한국사회복지학
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• 제47권
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• pp.272-309
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• 2001

It is a recent trend to emphasize community services for the rehabilitation of the mentally ill. However, it is also necessary to provide social work services for those living in the institutions, who is the most underprivileged in our society. To deal with interpersonal skill deficits which is one of the main characteristics of the mentally ill, social skills programs are being utilized, usually in the communities, but not in the institutions. Therefore, the objective of this study is to develop and evaluate institution-relevant program for the improvement of assertiveness, which is the basic ability among the interpersonal skills, and self-esteem, which is the emotional basis of assertiveness. Because there has been little literature on such a program, a preliminary program had been implemented in order to include the peculiarities of the life in the institutions on the main program. The evaluation of the program effect was done by pretest-post test control group design, and its results are as follows. Firstly, in regard to program effectiveness, the pre and post test showed that self-esteem improved in a statistically meaningful way, but that assertiveness did not so. However, the staff verified the improvement of the group members' assertiveness to some degree in their actual lives. Secondly, in regard to the group process, the group interaction improved in a statistically meaningful way between 2nd and 5th session, and the improvement maintained till the program termination. Also the group members evaluated the program as helpful in their everyday lives. Therefore it can be said that the result of this program is encouraging. In light of this, several suggestions were made: utilizing more dynamic techniques in the program; developing the advanced level of the program; making an effort to change environmental structures as well as individuals; applying this kind of program to another living facilities such as those for the homeless or handicapped.