• Title/Summary/Keyword: Impact speed

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Performance Enhancement of High-Speed TCP Protocols using Pacing (Pacing 적용을 통한 High-Speed TCP 프로토콜의 성능 개선 방안)

  • Choi Young Soo;Lee Gang Won;Cho You Ze;Han Tae Man
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.12B
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    • pp.1052-1062
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    • 2004
  • Recent studies have pointed out that existing high-speed TCP protocols have a severe unfairness and TCP friendliness problem. As the congestion window achieved by a high-speed TCP connection can be quite large, there is a strong possibility that the sender will transmit a large burst of packets. As such, the current congestion control mechanisms of high-speed TCP can lead to bursty traffic flows in hi인 speed networks, with a negative impact on both TCP friendliness and RTT unfairness. The proposed solution to these problems is to evenly space the data sent into the network over an entire round-trip time. Accordingly, the current paper evaluates this approach with a high bandwidth-delay product network and shows that pacing offers better TCP friendliness and fairness without degrading the bandwidth scalability.

Test and Numerical Analysis for Penetration Residual Velocity of Bullet Considering Failure Strain Uncertainty of Composite Plates (복합판재의 파단 변형률 불확실성을 고려한 탄 관통 잔류속도에 대한 시험 및 수치해석)

  • Cha, Myungseok;Lee, Minhyung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.3
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    • pp.281-288
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    • 2016
  • The ballistic performance data of composite materials is distributed due to material inhomogeneity. In this paper, the uncertainty in residual velocity is obtained experimentally, and a method of predicting it is established numerically for the high-speed impact of a bullet into laminated composites. First, the failure strain distribution was obtained by conducting a tensile test using 10 specimens. Next, a ballistic impact test was carried out for the impact of a fragment-simulating projectile (FSP) bullet with 4ply ([0/90]s) and 8ply ([0/90/0/90]s) glass fiber reinforced plastic (GFRP) plates. Eighteen shots were made at the same impact velocity and the residual velocities were obtained. Finally, simulations were conducted to predict the residual velocities by using the failure strain distributions that were obtained from the tensile test. For this simulation, two impact velocities were chosen at 411.7m/s (4ply) and 592.5m/s (8ply). The simulation results show that the predicted residual velocities are in close agreement with test results. Additionally, the modeling of a composite plate with layered solid elements requires less calculation time than modeling with solid elements.

Effects of Observation Network Density Change on Spatial Distribution of Meteorological Variables: Three-Dimensional Meteorological Observation Project in the Yeongdong Region in 2019 (관측망 밀도 변화가 기상변수의 공간분포에 미치는 영향: 2019 강원영동 입체적 공동관측 캠페인)

  • Kim, Hae-Min;Jeong, Jong-Hyeok;Kim, Hyunuk;Park, Chang-Geun;Kim, Baek-Jo;Kim, Seung-Bum
    • Atmosphere
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    • v.30 no.2
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    • pp.169-181
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    • 2020
  • We conducted a study on the impact of observation station density; this was done in order to enable the accurate estimation of spatial meteorological variables. The purpose of this study is to help operate an efficient observation network by examining distributions of temperature, relative humidity, and wind speed in a test area of a three-dimensional meteorological observation project in the Yeongdong region in 2019. For our analysis, we grouped the observation stations as follows: 41 stations (for Step 4), 34 stations (for Step 3), 17 stations (for Step 2), and 10 stations (for Step 1). Grid values were interpolated using the kriging method. We compared the spatial accuracy of the estimated meteorological grid by using station density. The effect of increased observation network density varied and was dependent on meteorological variables and weather conditions. The temperature is sufficient for the current weather observation network (featuring an average distance about 9.30 km between stations), and the relative humidity is sufficient when the average distance between stations is about 5.04 km. However, it is recommended that all observation networks, with an average distance of approximately 4.59 km between stations, be utilized for monitoring wind speed. In addition, this also enables the operation of an effective observation network through the classification of outliers.

New approaches to testing and evaluating the impact capability of coal seam with hard roof and/or floor in coal mines

  • Tan, Y.L.;Liu, X.S.;Shen, B.;Ning, J.G.;Gu, Q.H.
    • Geomechanics and Engineering
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    • v.14 no.4
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    • pp.367-376
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    • 2018
  • Samples composed of coal and rock show different mechanical properties of the pure coal or rock mass. For the same coal seam with different surrounding rocks, the frequency and intensity of rock burst can be significantly different in. First, a method of measuring the strain variation of coal in the coal-rock combined sample was proposed. Second, laboratory tests have been conducted to investigate the influences of rock lithologies, combined forms and coal-rock height ratios on the deformation and failure characteristics of the coal section using this method. Third, a new bursting liability index named combined coal-rock impact energy speed index (CRIES) was proposed. This index considers not only the time effect of energy, but also the influence of surrounding rocks. At last, a new approach considering the influences of roof and/or floor was proposed to evaluate the impact capability of coal seam. Results show that the strength and elastic modulus of coal section increase significantly with the coal-rock height ratio decreasing. In addition, the values of bursting liability indexes of the same coal seam vary greatly when using the new approach. This study not only provides a new approach to measuring the strain of the coal section in coal-rock combined sample, but also improves the evaluation system for evaluating the impact capability of coal.

Impact conditions of motorcyclists on road protection systems by numerical simulation

  • Peng, Li;Brizard, Denis;Massenzio, Michel
    • Structural Engineering and Mechanics
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    • v.82 no.2
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    • pp.233-244
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    • 2022
  • Following a loss of control, the impact against a road barrier in a turn predominates among the most severe motorcyclist accidents. These road restraint devices can be equipped with a motorcycle screen, the function of which is to restrain the rider and minimize the consequences of the impact in terms of the severity of injuries. The performance of these screens is evaluated by the European normative procedure EN1317-8, which specifies the test conditions, based on one or two configurations. In practice, however, these impact conditions are very diverse, difficult to extrapolate from accident analysis and therefore poorly investigated. This study is interested in improving knowledge of these impact conditions in terms of impact speed, impact angle and particularly position of the rider. A finite element model has been developed to simulate the dynamic behavior of the rider from loss of control to impact on the screen. Statistical analysis of the results shows a high variability of the impact conditions, in particular with regard to the direction of turn (to the right or to the left). Some improvements are suggested in order to overcome the limitations inherent in standard procedures.

Influence of Thermal Expansion on Eccentricity and Critical Speed in Dry Submersible Induction Motors

  • Lv, Qiang;Bao, Xiaohua;He, Yigang
    • Journal of Electrical Engineering and Technology
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    • v.9 no.1
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    • pp.106-113
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    • 2014
  • Rotor eccentricity is one of the major factors that directly influence the security of horizontal electrical machines, and the critical speed of the shaft has a close relationship with vibration. This paper deals with the influence of thermal expansion on the rotor eccentricity and critical speed in large dry submersible motors. The dynamic eccentricity (where the rotor is still turning around the stator bore centre but not its own centre) and critical speed of a three-phase squirrel-cage submersible induction motor are calculated via hybrid analytical/finite element method. Then the influence of thermal expansion is investigated by simulation. It is predicted from the study that the thermal expansion of the rotor and stator gives rise to a significant air-gap length decrement and an inconspicuous slower critical speed. The results show that the thermal expansion should be considered as an impact factor when designing the air gap length.

A Case Study on Speed Analysis of the Rear-end Collision Accident (자동차 추돌사고 속도분석에 관한 사례 연구)

  • Kim, Daebong;Yun, Daekwon;Park, Jeongho;Ha, Seongyong;Park, Jechul
    • Transactions of the Korean Society of Automotive Engineers
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    • v.24 no.6
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    • pp.724-729
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    • 2016
  • This case study carried out a rear-end collision accident analysis and physical simulation of an SUV and passenger car. The speed of the SUV by physical analysis is 71 ~ 87 km/h, while the speed of the passenger car is 6 ~ 22 km/h. Simulation results showed the optimal speed conditions for the SUV was 71 km/h, and 7 km/h for the passenger car. Simulations can be verified for the collision analysis. The findings of this study are expected to increase the reliability of accident reconstructions.

Turbulence Intensity Effects on Small Wind Turbine Power Performance (난류강도가 소형 풍력발전기 출력에 미치는 영향)

  • Kim, Seokwoo
    • Journal of the Korean Solar Energy Society
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    • v.33 no.6
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    • pp.19-25
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    • 2013
  • Energy generation from an instrumented Skystream 3.7 small wind turbine was used to investigate the effect of ambient turbulence levels on wind turbine power output performance. It is widely known that elevated ambient turbulence level results in decreased energy production, especially for large sized wind turbine. However, over the entire wind speed range from cut in to the rated wind speed, the measured energy generation increased as ambient turbulence levels elevated. The impact degree of turbulence levels on power generation was reduced as measured wind speed approached to the rated wind speed of 13m/s.

The Design Comparison of High-Speed & Common Railway Bridge with the Example of a Cable Supported Bridge (케이블 지지 교량을 예제로 한 고속철도 및 일반철도의 설계 차이점 분석)

  • Kim, Sung-Il;Byun, Hyung-Gyun
    • Proceedings of the KSR Conference
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    • 2009.05b
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    • pp.649-655
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    • 2009
  • Traffic safety and vibration serviceability of a railway bridge set a limitation to the application of long-span cable supported bridges even though the design trend of the bridge becomes longer and lighter. In the case of high speed railway, it becomes more severe for the high speed of the train and resonance of the structure. Therefore, the cable supported bridge does not exist in Korea high speed railway until now. On the other hand, in recent, Italia, Japan and China do design and construct the long-span cable supported bridges for high speed railway recently with overcoming of traffic safety and passenger comforts. In the present study, prior to analysis of traffic safety and passenger comforts, a extradosed bridge for common railway is re-designed for high speed railway. The difference of member forces and displacements by design live load, the difference of impact coefficient and variable stresses of cables are investigated.

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Analysis of Structures for Improving Pedestrian Wind Environment in Urban Areas (도시지역의 보행자 풍환경 개선을 위한 구조물 분석)

  • Park, Ha-Jun;Woo, Yun-Hee;Yoo, Moo-Young
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2023.05a
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    • pp.231-232
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    • 2023
  • With taller buildings and larger typhoons, the impact of building winds is growing. During the 11th Typhoon Hinnamno in 2022, the building wind in Busan L City exceeded 60m/s, reaching the highest speed ever. Although many studies have been conducted on reducing the wind load of buildings, which is one of the problem factors caused by strong wind speed, there is a lack of research on wind speed reducing sculptures that can directly control strong wind speed. In this paper, several types of wind speed reduction sculptures were proposed to solve these problems, and the wind speed reduction capability of the proposed sculptures was analyzed through computational fluid dynamics (CFD). These results can contribute to suggesting effective design methods for improving the urban environment and reducing pedestrian stress.

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