• 한국도로학회논문집
• /
• 제17권4호
• /
• pp.1-9
• /
• 2015

PURPOSES : The purpose of this study is to revise the weight to power ratio of the representative truck in S. Korea. So far, S. Korea has been using the unit lb/hp, and the construction machines were not considered in the evaluation of the performance of trucks. METHODS : This study was performed to recommend the use of ISO system of units, and to analyze the weight to power ratios of the representative trucks in S. Korea, including the dump trucks, concrete mixer trucks, and asphalt and concrete diffusers. RESULTS: From this study, the 85 percentile value of the weight to power ratio of the trucks in S. Korea's was found to be 103.6 kg/kw. CONCLUSIONS : The performance standard for the representative truck has to be increased upward, considering the travel pattern of the dump trucks, concrete mixers, and asphalt and concrete diffuser trucks, travel distances, narrow area (work zone) of operation, and the saving in construction budget for climbing lane. Based on this study, the weight to power ratio of the representative truck in S. Korea could possibly be revised to 100~110 kg/kW.

• Journal of Welding and Joining
• /
• 제21권1호
• /
• pp.48-53
• /
• 2003

The object of this study is to examine the effect of short circuit time ratio (SCTR) and current rise delay time (Td) on the spatter generation at low and medium current range in $CO_2$ welding. The spatter was evaluated by the weight generated in the welding of bead-on-plate for 30 seconds (3 times). Td was varied by order of 0, 0.4, 0.8 and 1.2 msec. At each Td, the short circuit time ratio was varied by the output voltage of the welding power source. In the low current range, it was found that the optimum SCTR was 20~25%, and the minimum spatter generation weight was obtained in the case of Td=0.4msec and SCTR=22% even though the remarkable difference was not showed by the application of Td. In the medium current range, it was confirmed that the arc was stable though the SCTR was increased from 20% to 40% by the control of current wave. Spatter generation weight depended on the variation of Td, and the lowest value of spatter generation weight occurred at Td=0.8~1.2msec.

• 한국항행학회논문지
• /
• 제22권2호
• /
• pp.111-122
• /
• 2018

현재 우리나라를 포함한 다수의 국가에서 지상 교통수송 체계가 포화상태에 이르렀다. 이를 해결하기 위해 교통체계의 3차원 화로 교통체증을 완화하고 door-to-door 이동성을 달성하고자 도로주행형 개인용 항공기 (PAV; personal air vehicle)에 관한 많은 연구가 진행되고 있다. 본 연구에서는 도로주행형 PAV의 사이징에서 지상 활주거리, 상승률, 최대 순항속도, 최대 상승고도, 실속 속도 등의 구속조건하에서 주요 설계 변수인 추력대중량비, 익면하중, 동력대중량비를 구하기 위한 구속조건 해석을 수행하였다. 또한 사이징 과정에서 국내 환경과 일반항공기급 인증기준인 FAR PART 23을 고려한 임무형상에 대하여 추력대중량비, 익면하중, 동력대중량비, 그리고 제동마력의 그래프를 통해서 설계점을 결정하는 연구도 수행하였다.

• 한국항행학회논문지
• /
• 제23권1호
• /
• pp.44-54
• /
• 2019

많은 나라들에서 늘어가는 자동차로 인한 교통체증에 대체 할 수 있는 새로운 교통수단에 대한요구가 증가하고 있다. 또한, 경제적인 성장으로 인한 자동차 보유 대수의 증가로 앞으로 교통체증은 더욱 증가할 것이다. 이를 위해 도로주행형 개인용 항공기(PAV; personal air vehicle)에 관한 많은 연구가 진행되고 있다. 본 연구에서는 도로주행형 PAV의 사이징에서 엔진과 익형의 종류에 따른 주요 설계 변수인 익면하중과 동력대중량비를 구하기 위한 사이징을 수행하였다. 즉, 사이징 과정에서 국내 환경과 일반 항공기급 인증기준인 FAR PART 23을 고려한 임무형상에 대하여 익면하중, 동력대중량비, 제동마력, 그리고 연료효율의 그래프를 통해서 설계점을 결정하는 연구도 수행하였다. 사이징 결과 디젤 엔진을 사용하는 경우 가솔린 엔진보다 더 큰 중량으로 인해 더 큰 이륙총중량, 날개 면적, 그리고 더 큰 동력을 요구한다.

• 한국항공우주학회지
• /
• 제40권7호
• /
• pp.590-600
• /
• 2012

본 논문에서는 태양전지나 연료전지와 같은 전기 에너지원을 사용하는 항공기에 적용할 수 있는 일반화된 사이징 방법에 대해 연구를 수행하였다. 다중 추진 시스템이나 에너지원이 사용되는 경우를 고려하여 다중 동력경로를 모델링하였고 소모성 에너지와 비소모성 에너지 중량을 각 임무 단계의 중량변화 계산에 반영하였다. 구속조건의 분석에서 기존의 추력 대 중량비 대신 동력 대 중량비를 선택하여 동력 균형 및 에너지 균형의 사이징 과정에 사용하였다.

• 한국항해학회지
• /
• 제17권3호
• /
• pp.69-76
• /
• 1993

In harbour the practical shiphandlers should have a expert knowledge of systematically reducing head-way and keeping ship's positions to the final position with confidence and under control. But now in the practical approaches we do not have any special maneuvers of controlling the ship effi-ciently regarding the headway and approaches except some existing reduction of speeds according to the Weight-to-Power Ratio, use of astern power and Rudder Cycling. Consequently this study put Woo's Super Rudder Controlling originally developed by Captain Woo, Ph. D. to practical use as a special maneuvers in the port approaches. The conclusions of this paper are drawn as follows : 1) Optimum standard and desirable controls in combination of three engine speeds with three yaw ang-les were proposed for the practical shiphandlers, 2) According to simulation of the pilotships the Super advances are 10.5 ship lengths for Full full full maneuvers, and 7.9 ship lengths for Full half maneuvers approximately, 3) Approach maneuvers to anchorages by trying Woo's Super Rudder Controlling saved about 30% of total standby time in comparison with the existing Weight-to-Power Ratio maneuvers in the Pusan and Kwang Yang ports.

• Journal of Biosystems Engineering
• /
• 제2권1호
• /
• pp.49-54
• /
• 1977

In order to obtain the field efficiency of the power tiller plowing on the various size of and its length-width field tests were performed with 8ps.10ps. power tiller popularly used in the korean rural area, and Satoh 5ps. made in Japan, Land Master 5ps. made in England were tested to compare with the field efficiency of the above power tillers. The results obtained in this tests were as follows ; 1. In considering of the resting time and the refueling time and others, the field efficiency of Satoh was the highest among the power tillers as to be 80%, at the 8ps. power tiller 76.5%, at the 10ps. power tiller 79.3% and the lowest field efficiency was obtained at the Land Master as 75.7%. 2. The field efficiency of the each power tiller increased as the ratio of the length to width of the field was increased. 3. The increasing rate of field efficiency was much bigger in the below the ratio of 5 : 1 but at the upper ratio increased above, the ratio was nearly constant. 4. The field efficiency of the power tiller was higher at the smaller power tiller than the larger, except the Land Master , because of easily operating and turning of the power tiller by virtue of its lighter weight.

• 한국정밀공학회지
• /
• 제10권2호
• /
• pp.14-21
• /
• 1993

Pneumatic actuators have greater power to weight ratio than electric ones, but they have been rarely used as robotic actuators because of poor accuracy resulted from nonliearity of air. On the other hand, electric servo motors have glld controllability, but they have poor power to weight ratio. For the heavy load handling robot a combined actuating method was developed for vertical and horizontal axes of RISTBOT-ll which handles up to 250kgf load. In this paper, the control method is implemented and analyzed for the manufactured heavy load handling robot.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
• /
• pp.311-314
• /
• 2008

The volume and size of the wind turbine gearbox has been increased with increasing transmitted power. The optimal sizing of gearbox is important due to limited space on the nacelle. The power-split type planetary gear train has been regarded as a better solution than conventional type from the point of view of the volume and weight. The purpose of this paper is to optimize the volume and weight of the gearbox by the analysis of structural characteristics and evaluation of strength of the power-split type planetary gear train.

• 대한전자공학회논문지SP
• /
• 제45권4호
• /
• pp.100-106
• /
• 2008

본 논문에서는 다양한 잡음 환경에서 음성의 통계적 모델에 기반한 음성 검출기의 성능향상을 위해 PSFM (Power Spectral Flatness Measure)을 이용하여 실시간으로 변별적 가중치 학습 (Discriminative Weight Training) 기반의 최적화된 우도비 테스트 (Likelihood Ratio Test, LRT)를 제안한다. 먼저, 기존의 통계모델기반의 음성 검출기를 분석하고, 이를 기반으로 MCE (Minimum Classification Error)방법을 도입하여 도출한 각 주파수 채널별 가중치를 PSFM 값에 기반하여 실시간 매 프레임마다 다른 가중치를 적용한 우도비 기반의 음성 검출 결정법을 제시한다. 제안된 알고리즘은 다양한 잡음 환경에서 기존에 제시된 음성 검출기와 비교하였으며, 우수한 성능을 보인다.