• International Journal of Automotive Technology
• /
• 제1권1호
• /
• pp.17-25
• /
• 2000

The electromechanical valve train (EMV) technology allows for a reduction in fuel consumption while operating under a stoichiometric air-fuel-ratio and preserves the ability to use conventional exhaust gas aftertreatment technology with a 3-way-catalyst. Compared with an engine with a camshaft-driven valve train, the variable valve timing concept makes possible an additional optimization of cold start, warm-up and transient operation. In contrast with the conventionally throttled engine, optimized control of load and in-cylinder gas movement can be used for each individual cylinder and engine cycle. A load control strategy using a "Late Intake Valve Open" (LIO) provides a reduction in start-up HC emissions of approximately 60%. Due to reduced wall-wetting, the LIO control strategy improves the transition from start to idle. "Late Exhaust Valve Open" (LEO) timing during the exhaust stroke leads to exhaust gas afterburning and, thereby, results in high exhaust gas temperatures and low HC emissions. Vehicle investigations have demonstrated an improved accuracy of the air-fuel-ratio during transient operation. Results in the New European Driving Cycle have confirmed a reduction in fuel consumption of more than 15％ while meeting EURO IV emission limits.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
• /
• 제6권2호
• /
• pp.113-119
• /
• 2000

본 논문에서는 주기억장치 데이타베이스의 특성을 반영하여 시간제약조건을 처리할 수 있는 실시간 주기억장치 데이타베이스시스템을 위한 질의 처리기를 설계하고 구현한다. 제안된 질의 처리기는 메타 데이타베이스를 이용하여 시간제약을 갖는 실시간 데이타를 유지 관리한다. 응용 프로그램의 작성을 위해서 CLI를 지원하고 있으며, 이를 확장한 확장 CLI와 저장 CLI를 지원하여 확장 CLI를 이용하여 실시간 트랜잭션의 정보를 CLI를 사용으로 표현할 수 있도록 하였고, 빈번하게 수행되는 트랜잭션을 지원하기 위해 저장 CLI를 지원한다. 제안된 질의 처리기는 주기억장치 실시간 데이타베이스 관리시스템의 질의처리기로 구현하였으며, 성능평가를 통해서 시스템의 질의처리 능력과 실시간 데이타의 효율적인 관리를 통해서 종료시한을 만족하는 실시간 트랜잭션의 비율이 증가됨을 보였다.

• 방송공학회논문지
• /
• 제21권2호
• /
• pp.261-267
• /
• 2016

본 논문에서는 타이밍 오프셋 보상을 위한 위상 전 왜곡 기법, 파일럿 성분 추정과 제거를 위한 직류 제거기, 송수신 신호 사이의 상관도를 기반으로 귀환 신호의 지연 시간을 추정하는 기법을 이용한 DAB(Digital Audio Broadcasting)용 간섭 제거 기반 동일 채널 중계기를 제안하고, 이를 ATSC(Advanced Television Systems Committee)시스템에 적용한다. 제안한 간섭 제거 기반의 동일 채널 중계기는 주송신 신호보다 간섭 신호가 더 큰 환경에서의 간섭 제거 능력이 확인되었으며, 이에 따라 중계기의 송출 능력의 개선, 짧은 처리 지연 시간과 더불어 양호한 신호 품질이 얻어짐을 시뮬레이션을 통하여 확인한다.

• 한국통신학회논문지
• /
• 제33권4A호
• /
• pp.473-478
• /
• 2008

5.9 GHz WAVE(Wireless Access for the Vehicular Environment)는 노변-차량, 차량-차량 통신을 통하여 공공안전과 개인통신을 지원하기 위한 중단거리 무선통신 방식이다. WAVE 물리계층의 핵심기술은 시간동기오류에 민감한 OFDM 방식이며 통신링크상의 지연을 최소화하여 고속의 차량통신 환경을 제공하는 것이 매우 중요하다. 본 논문에서는 오류에 강인하고 복잡도가 낮고 지연시간이 적은 WAVE 시스템 응용을 위한 시간동기 알고리즘과 하드웨어 구조를 제안한다. 제안된 알고리즘은 기존의 알고리즘에 비교하여 연산의 복잡도와 지연시간이 감소되며 하드웨어 구조는 파이프라인 구조와 고속 동작에 영향을 줄 수 있는 RAM이 필요하지 않다는 장점이 있다. Matlab과 FPGA를 이용한 하드웨어 구현을 통한 동기화 오차율(SER) 실험결과, 제안된 알고리즘이 고속 이동환경에 대해 강인하고 효율적이라는 확인하였다.

• KDI Journal of Economic Policy
• /
• 제32권1호
• /
• pp.97-129
• /
• 2010

본고에서는 2002년 1월에서 2008년 12월까지 존재한 국내 주식형 펀드를 대상으로 하여 투자성과를 평가하고 마켓타이밍 능력의 존재 여부를 검토하였다. 주요 분석 결과는 다음과 같다. 첫째, 모든 투자비용을 공제한 순수익률 기준 펀드의 초과성과는 0과 다르지 않았다. 둘째, 투자비용이 공제되기 이전 총수익률 기준 펀드의 초과성과는 통계적으로 유의하게 0을 상회하였다. 특히, 보수수준과 초과성과 간에는 양의 상관관계가 있는 것으로 나타났다. 셋째, 보수수준이 높은 그룹에서 발견된 양의 초과성과를 마켓타이밍 능력과 주식선별능력으로 구분하는 추정을 실시하였으나, 추정 결과는 일의적인 해석이 곤란하였다. 분석 결과는 일단 Grossman and Stiglitz(1980)가 상정한 정보비용이 존재하는 효율적 시장가설과 일치한다. 그러나 보수가 높은 펀드의 초과성과 창출요인이 밝혀지지 않았으므로 이 해석의 타당성에 대한 결론적 언명은 추가 연구를 필요로 한다.

• 국제물리치료학회지
• /
• 제6권2호
• /
• pp.884-890
• /
• 2015

This study observed the effects of ankle strengthening exercise and whole body vibration on the balance ability of older adults, thereby intending to provide basic materials for intervention methods aimed at improving older adults' balance ability. The subjects were 20 older adults who had experienced a fall. They were equally divided into two groups. Ankle strengthening training was applied to one group and ankle strengthening training and whole body vibration were applied to the other group, a timed up and go (TUG) test and Tinetti performance oriented mobility assessment (POMA) were performed, and changes in the subjects' limits of stability were observed. The TUG and POMA results significantly differed between before and after the experiment in the angle strengthening training (AST) group and the angle strengthening training with whole body vibration (ASTWV) group. In addition, the interaction between timing and each group was statistically significant. The limits of stability significantly changed after the intervention in both groups. Differences in the posterior and right limits of stability were significant between the AST group and ASTWV group. Therefore, ankle strengthening exercise and whole body vibration improve older adults' balance maintenance and reduce falls or the risk factors for falls in older adults.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• 제16권3호
• /
• pp.359-370
• /
• 1994

The reconstruction of major head and neck defects must be an integral part of the overall cancer treatment plan. The priorities of surgical treatment of head and neck tumor are 1) local tumor control, 2) relief of pain, 3) avoidance of difficult dressing, 4) provision of oral continence, and 5) ability to swallow and manage saliva. The recent advances in reconstructive surgery including the development of musculocutaneous flaps and microvascular free tissue transfer have allowed the surgical restoration of head and neck tumor defects that previously were not possible. These techniques have provided the opportunity to undertake larger, more aggressive resection while at the same time permitting functional rehabilitation. The timing of reconstruction demands on the nature of the resection, the ability of the ablative and reconstructive teams to coordinate efforts, the overall health of the patients, the patient's needs and wishes. So, we report to emphasize current methods for restoring major head and neck tumor defects after tumor ablation, reviewing for the reconstructive operations, postoperative complications, and postoperative sequelae etc, of patients from Jan, 1990 to Dec, 1993.

• 한국초등과학교육학회지:초등과학교육
• /
• 제26권2호
• /
• pp.161-170
• /
• 2007

This study aims at helping us improve the methods used to teach elementary school students how to handle experimental apparatus by examining their manual skills and their understanding of the alcohol lamp, spuit and thermometer. To evaluate their ability to handle each experimental apparatus, a practical skills test and knowledge evaluation sheets were developed. The evaluation was carried out with 270 students from 2 classes each in the 3rd, 4th, 5th and 6th grade of D Elementary School located in Daejeon City. For their handling ability of the alcohol lamp, the results for the practical skills test showed that the students had a very low ability in placing objects in the center of the apparatus for safe use and also in adjusting the height of the trivet to place objects so that they contact the outer flames correctly. For the spuit, the pass rate of the skills test was generally low in regards to how students should grasp a spuit and the timing and method of depressing the rubber part before dipping it into liquid. For the thermometer, on the other hand, the pass rate was relatively high in every respect. The knowledge evaluation results for the use of experimental apparatus showed a very high rate of correct answers for alcohol lamps and thermometers. The test results for spoils also produced a relatively high rate of correct answers, with the exception of the test item regarding the way that students should grasp them.

• 한국연소학회지
• /
• 제11권4호
• /
• pp.14-21
• /
• 2006

In this study, syngas which is reformed from fossil fuel and has hydrogen as a major component, was added to a gasoline engine to improve combustion stability and exhaust emissions of idle state. Syngas fraction of the total supplied fuel varied to 0 %, 25 %, 50 % with various ignition timing and excess air ratio. Combustion stability, exhaust emissions, fuel consumption and exhaust gas temperature were measured to investigate the effects of syngas addition on idle performance. Results showed that syngas has ability to widely extend lean operation limit and ignition retard range with dramatical reduction of engine out emissions. It is supposed that the usage of syngas in the internal combustion engine is an effective solution to meet the future strict emission regulations.

• 산업기술연구
• /
• 제30권B호
• /
• pp.75-81
• /
• 2010

This paper presents the development of LED street light lamp which is controled by central command system. This system includes a lamp unit controller, data repeater and command repeater as well as the LED lamps. These devices enable the individual power control and partial on/off control of the LED lamps by the control repeater through full duplex communication line. Also, they have the ability to control the brightness and period of on/off timing by detecting the car's existence. As a result of this development, it is founded that the performances of the system have been satisfied to apply for the actual road test.