• 한국자동차공학회논문집
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• 제20권5호
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• pp.8-12
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• 2012

Application for laser welding have increased steadily in recent years due to its benefits such as high speed, high productivity and high density energy heat source. In this study, the influence of welding parameters was investigated on penetration characteristics, mechanical properties including formability test in disk laser welded 1000MPa class steels. A shielding gas was used and bead-on-plate test was performed with various welding speeds. The main welding test was performed by butt welding with various welding speeds at 2.5 kW laser power.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 창립기념 춘계학술대회 논문집
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• pp.596-603
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• 1998

The entry compression wave, which is generated at the entrance of the tunnel, is almost always associated with the pressure transients in the tunnel as well as the impulse noise at the exit of the tunnel. It is highly required to design the train nose shape that can minimize such undesirable phenomena. The objective of the current work is to investigate the effects of the train nose shape on the entry compression wave. Numerical computations were applied to one-dimensional unsteady compressible flow in high-speed railway train/tunnel systems. A various shape of train noses were tested for a wide range of train speeds. The results showed that the strength of the entry compression wave is not influenced by the train nose shape, but the time variation of pressure in the entry compression wavefront is strongly related to the train nose shape. The current method of the characteristics was able to represent a desirable nose shape for various train speeds. Optimum nose shape was found to considerably reduce the maximum pressure gradient of the entry compression wave.

• 산업경영시스템학회지
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• 제37권1호
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• pp.133-140
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• 2014

An efficient heuristic for two-vehicle-one-depot problems is developed in this research. Vehicle moving speeds are various along hour based time intervals due to traffic jams of rush hours. Two different heuristics are examined. One is that the delivery area assignment is made using Sweep algorithm for two vehicles by splitting the whole area in half to equally divide all delivery points. The other is using common area by leaving unassigned area between the assigned for two vehicles. The common area is reassigned by two stages to balance the completion time of two vehicle's delivery. The heuristic with common area performed better than the other due to various vehicle moving speeds and traffic jams.

• 한국도로학회:학술대회논문집
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• 한국도로학회 2006년도 학술발표회 논문집
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• pp.217-222
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• 2006

• 한국도로학회:학술대회논문집
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• 한국도로학회 2006년도 춘계학술대회 논문집
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• pp.37-44
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• 2006

• International Journal of Automotive Technology
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• 제4권3호
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• pp.109-117
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• 2003

The analysis and evaluation of the transient performance by the transient response specifications under various acceleration speeds and types based on driver's typical acceleration habit are implemented by the experimental study to provide the appropriate direction for the transient control in a gasoline engine. The concept of the transient response specifications which consist of delay time, rising time, maximum overshoot and settling time, and the analysis method using them are introduced to evaluate the characteristics of the transient performance quantitatively. Furthermore four acceleration speeds and four acceleration types are set respectively to realize the various transient states which are similar to the real drive. Several performance parameters in terms of engine speed, manifold absolute pressure, fuel injection duration and air excess ratio are measured simultaneously during the various acceleration using a throttle actuator controlled by a PC. The transient response specifications characterized well the transient performance for the various acceleration speed and types quantitatively. Delay and rising time with increment of the acceleration speed became shorter, but settling time did longer. Intensified acceleration type appeared to be the most economical in view of fuel consumption, and linear acceleration type was found to have the least harmful emission concentration.

• 대한토목학회논문집
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• 제34권6호
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• pp.1851-1861
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• 2014

본 연구는 단속류에서 수집된 프로브 자료의 특성을 고려하여 신뢰성 있는 구간 통행속도를 산출하는 것을 목표로 하고 있다. 먼저, 프로브 자료의 특성을 분석하기 위하여 각 프로브 차량의 구간 통행시간 분포를 살펴보았고, 단거리전용통신(DSRC)을 통해 수집된 프로브 차량별 구간 통행속도 차이를 비교하였다. 그 결과, 구간 통행시간의 분포는 이상치를 제거하여야 하는 것으로 나타났다. 하지만, DSRC 프로브 차량의 구간 통행속도는 뚜렷한 차이가 없는 것으로 나타났다. 끝으로, 프로브 차량의 구간 통행속도 분포 특성과 수집 주기 동안에 집계된 대표값을 토대로 본 연구에서는 최적의 이상치 제거 절차를 도출하였고, 추정 오차를 평가하였다. 평가 결과, DSRC 구간 통행속도는 실 주행차량의 관측값과 유사한 값으로 나타났다. 반면에, 시내버스 구간 통행속도의 경우는 DSRC 구간 통행속도보다 덜 정확한 것으로 분석되었다. 향후 BIS 프로세스 개선과 실시간으로 수집되는 시내버스의 운행정보를 이용하여 도로소통정보로도 활용할 수 있는 다양한 방안을 모색할 필요가 있다.

• 한국도로학회논문집
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• 제15권1호
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• pp.127-134
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• 2013

PURPOSES: Speeding is often the primary contributor to fatal crashes. Surprisingly, driving behaviors are indirectly affected by personal factors such as law-abidance, risk sensitivity, and situational adaptability. This research aims to verify the effectiveness of pavement markings at reducing the speeds of high-risk drivers. The purpose of this study is to establish how drivers (including law-abiding or law-breaking, high-risk or low-risk) react to different pavement markings in a driving simulator. METHODS: The five different pavement markings were selected from markings used in other nations. The forty-two drivers were then surveyed, via questionnaires, and placed into the corresponding groups. Finally, statistical analysis was conducted to determine the extent of speed reduction for each pavement marking. RESULTS: Higher speeds were linked to the high-risk drivers. Furthermore, after analysis of the mean difference of average speeds by pavement marking, it was determined that Dragon's Teeth had the greatest speed reducing effect on these drivers. CONCLUSIONS: Perceptual countermeasures are unlikely to strongly affect high-risk drivers' perception of speed on the curves. This statistically demonstrates that Dragon's Teeth have a subtle effect on reducing speeds in the driving simulator. This study's significance lies in the improved understanding of high-risk drivers in terms of road facilities. It approaches the effects of various patterns of pavement markings for high-risk drivers.

• 소성∙가공
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• 제12권1호
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• pp.3-10
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• 2003

The formation of surface defects associated with Jotting in injection molding is related to the geometries of cavity and fate, operational conditions and the rheological properties of polymer. In this study we have examined jetting phenomena in injection molding process for the throe kinds of PCs which have different molecular weights and structures, PBT and PC/ABS alloy with several injection speeds. We have used various cavity shapes those are tensile, flexural and impact test specimens with various gates and cavity thicknesses. Through this study we have observed that the jetting is related to the dic swell of material. This means that the jotting is strongly affected by the elastic flow property rather than the viscous flow property in viscoelastic characteristics of molten polymer. Different resins have different elastic properties, and elastic flow behavior depends on the shear rate of flow, i.e. injection speed. Large die swell would eliminate jetting however, the retardation of die swell would stimulate jetting. In the point of mole design, reducing the thickness ratio of cavity to gate can reduce or eliminate jetting regardless of amount of elasticity of polymer melt.

• Composites Research
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• 제28권2호
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• pp.65-69
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• 2015

본 연구는 도로시설물에 적용될 수 있는 복합재료 지주구조에 대하여 실차 차량 충돌 시뮬레이션을 통한 동적 특성을 다룬다. 다양한 차량 충돌 속도에 대한 서로 다른 복합재료 물성의 영향을 LS-DYNA 유한요소 프로그램을 사용하여 분석하였다. 본 연구에서는 LS-DYNA 프로그램을 적용하여 기존의 강재 지주구조에 대한 유한 요소해석을 다양한 복합재료로 구성된 지주구조로 확장하여 적용하였다. 탑승자 안전성 평가를 기반으로 다양한 매개변수에 대한 수치해석 결과는 지주와 차량에서 발생하는 내부에너지를 비교 분석하여 규명하였다.