• Title/Summary/Keyword: speed-up effect

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Long-Term Trend of Surface Wind Speed in Korea: Anemometer Height Adjustment (한반도 지상 풍속의 장기 추세 분석: 풍속계 고도 보정)

  • Choi, Yeong-Ju;Park, Chang-Hyun;Son, Seok-Woo;Lee, Jae-Won;Hong, Dong-Chan
    • Atmosphere
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    • v.31 no.1
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    • pp.101-112
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    • 2021
  • The long-term trend of surface wind speed in Korea is examined for 31 KMA weather stations from 1985 to 2019. Most stations, except Daegwallyeong, have several times of anemometer height changes from tens of centimeters to several meters. To minimize such height change effect on long-term wind trend, the present study adjusts anemometer height in each station to the standard height of 10 m using the power-law wind profile. This adjustment results in non-negligible trend change. For instance, the increasing surface wind speed at Suwon station, which has six times of anemometer height changes in a range of 0.8 m to 20 m, is weakened up to 67% and becomes statistically insignificant. Likewise, the decreasing trend at Andong station, with three times of anemometer height changes in a range of 10 m to 15.5 m, is weakened up to 66%. A similar weakening in long-term trend is observed in most stations regardless of positive and negative trends. However, due to the cancellation between weakened negative trends and weakened positive trends, the station-averaged wind speed trend in Korea does not change much. This result suggests that anemometer height adjustment is crucial for evaluating local wind speed trend but its impact on nation-wide wind speed trend is rather minor.

Optimization of a geometric form and cutting conditions of a metal slitting saw by experimental method (실험적 방법을 통한 Metal slitting saw의 형상 및 절삭 조건의 최적화)

  • 정경득;고태조;김희술
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.05a
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    • pp.934-938
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    • 2000
  • Built-up edge affects the surface integrity of the machined surface and tool wear. Tool geometry and cutting conditions are very important factors to remove BUE. In this paper, we optimized the geometry of the metal slitting saw .1nd cutting conditions to remove BUE by the experiment. In general, the metal slitting saw is plain milling cutter with thickness less of a 3/16 inch. This is used for cutting workpiece where high dimensional accuracy and surface finish are necessary. The experiment was planned with Taguchi method that is based on the orthogonal array of design factors(coating, rake angle, number of tooth, cutting speed, feed rate). Response table was made by the value of the surface roughness, the optimized tool geometry and cutting conditions through response table could be determined. In addition. the relative effect of factors were identified by the variance analysis. filially. coating and cutting speed turned out important factors.

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Anion Distribution and Correlation Analysis by Fountain Type in Urban (도심지내 분수유형별 음이온 분포 및 상관성 분석)

  • Kim, Jeong-Ho;Park, Seung-Hwan;Kim, Won-Tae;Yoon, Yong-Han
    • Journal of Environmental Science International
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    • v.22 no.12
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    • pp.1599-1610
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    • 2013
  • In order to verify the healing effect in the variety of effects according to fountain type, anion which is the representatives factor of healing, as the center of case studies which in Gwanghwamun(Ground fountain), Cheonggyecheon(Waterfall) and Myeongdong(Formative fountain). According to fountain type, the anion distribution as follow, figures typically$ 15,721{\pm}419ea/cm^3$, Formative fountain $40,190{\pm}788ea/cm^3$, Waterfall $4.480{\pm}290ea/cm^3$ and ground fountain $2.492{\pm}180ea/cm^3$. It is usually exceed to the distribution in natural green, which is $1070{\sim}2100ea/cm^3$. The interrelation between air temperature, relative humidity, wind speed and relative humidity, and wind speed is that, the relative humidity is directly proportional to wind speed and inversely proportional to temperature. As the temperature goes up, the distribution of anion goes down. And as the wind speed and relative humidity goes up, the distribution of anion decrease sharply. The result of interrelation between fountain type and the anion distribution is that, the distance of water falling is directly proportional to the anion distribution in the formative fountain and inversely proportional in the ground fountain. And the distribution of anion is largest in formative fountain. The distribution of anion in ground fountain is lower than in formative fountain, but it is far more than in natural greenery. And as the distance from fountain increase, the distribution of anion goes down.

A Study of Head-Up Display System for Automotive Application (Head-Up Display 장치의 자동차 적용을 위한 연구)

  • Yang, In-Beom;Lee, Hyuck-Kee;Kim, Beong-Woo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.4
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    • pp.27-32
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    • 2007
  • Head-Up Display system makes it possible for the driver to be informed of important vehicle data such as vehicle speed, engine RPM or navigation data without taking the driver's eyes off the road. Long focal length optics, LCD with bright illumination, image generator and vehicle interface controllers are key parts of head-up display system. All these parts have been designed, developed and applied to the test vehicle. Virtual images are located about 2m ahead of the driver's eye by projecting it onto the windshield just below the driver's line of sight. Developed head-up display system shows satisfactory results for future commercialization.

A Proposal on Calculation Model to Predict Environmental Noise Prediction Emitted by High Speed Trains (고속철도 환경소음예측을 위한 계산 모델 제안)

  • Cho, Dae-Seung;Cho, Jun-Ho;Kim, Jin-Hyeong;Jang, Kang-Seok;Yoon, Jae-Won
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2011.10a
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    • pp.843-848
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    • 2011
  • Planning and construction of railway for high speed trains up to 400 km/h are recently driven in Korea. High speed train is one of the environment-friendly fastest mass transportation means but its noise generated by rolling, traction and aerodynamic mechanism can cause public complaints of residents nearby railways. To cost-effectively prevent the troublesome noise in a railway planning stage, the rational railway noise prediction method considering the characteristics of trains as well as railway structures should be required but it is difficult to find authentic methods for Korean high speed trains such as KTX and KTX-II. In this study, we propose a framework of our own railway noise prediction model emitted by Korean high speed trains over 250 km/h based on the recent research results carried out in EU countries. The model considers railway sound power level using several point sources distributed in heights as well as tracks, whose detail speed- and frequency-dependent emission characteristics of Korean high speed trains should be determined in near future by measurement or numerical analysis. The attenuation during propagation outdoors is calculated by the well-known ISO 9613-2 and auxiliary methods to consider undulated terrain and wind effect.

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An Analysis of Running Safety according to the Guard Rail Change of F10/F12 Turnout (F10/F12 분기기에서의 가드레일 변화에 따른 주행안전성 해석)

  • Kim, Sung-Jong;Kim, Tae-Geon;Eom, Beom-Gyu;Kang, Bu-Byoung;Lee, Hi-Sung
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.1881-1887
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    • 2011
  • The speed-limit regulation on the turnout is the main cause which hinders the speed-up of conventional lines among many factors. The specification speed for the train which passes the turnout system is lower than that on the general track. In this paper, shape of guard rail of Daegu Metropolitan Transit Corporation was investigated, and the effect of the variation of guard rail length on the running safety of a vehicle was analyzed for the purpose of speed improvement on turnout using the developed analysis method.

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Light Weighted Design of Aluminum Bumper Backbeam by Rib Shape Change (리브 형상 변경에 의한 알루미늄 범퍼 백빔의 경량화 설계)

  • Kang, Sungjong
    • Journal of Auto-vehicle Safety Association
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    • v.10 no.2
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    • pp.6-12
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    • 2018
  • Optimized section shape of aluminum bumper backbeam for enhancing the front high speed crashworthiness was investigated. Front body analysis model of a convertible vehicle was built up and parameter studies were carried out with changing the inner rib shape and the section thickness distribution. First an inner rib shape displaying most efficient structural performance was selected. Next, for the selected section the effect of section thickness combination was examined. Also, a light weighed backbeam section displaying crash performance over the current design was suggested. Finally RCAR front low speed impact analyses were carried out for the optimized models.

A Study on the Characteristics to working Condition of STD11 in Wire-Cut EDM (Wire-Cut EDM에서 가공조건에 따른 STD11의 가공특성에 관한 연구)

  • Lee, Hong-Gil;Kim, Won-Il;Lee, Yun-Kyung;Wang, Duk-Hyun;Kim, Jong-Up
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.4 no.3
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    • pp.5-12
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    • 2005
  • In wire discharge machining which is using STD 11 as die materials, the major factors of machining speed are discharge voltage, discharge current, and discharge time. All of the three factors give the effect. Increasing of the discharge pulse time gets groove width wider and it relatively increases surface roughness and clearance. If no load voltage is decreased, surface roughness is good but it decreases machining speed. If on time is increased, machining speed will get faster and clearance and offset value also get bigger.

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Noise Prediction and Design of Soundproof Facilities for the High Speed Train (고속열차(TGV) 주행시 연변에서의 소음예측 및 방음시설설계)

  • ;J. P. Clairbois
    • Journal of KSNVE
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    • v.9 no.6
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    • pp.1106-1115
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    • 1999
  • This paper sums up the study of the soundproof facilities (noise barriers) to be placed on the test track section within the Seoul-Pusan H.S.T. project. The objective of this study is to determine optimum design of soundproof including height, length, location, sound absorbing materials for test track(chonan-taejon). This paper shows the model to design the shape and materials of noise barrier for high speed trains(TGV, ICE, ect). The design of soundproof facilities is to be conducted by MITHRA for the prediction of noise impact of the TGV and for optimising noise barriers in order to reduce the noise generated by high speed trains. A number of computer simulations are carried out in order to determine the specification of noise barrier on test track.

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Effect of Screen Printing and Sintering Conditions on Properties of Thick Film Resistor on AlN Substrate (인쇄 및 소결조건이 AlN 기판용 후막저항체의 특성에 미치는 영향)

  • Koo, Bon Keup
    • Journal of the Korean Ceramic Society
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    • v.51 no.4
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    • pp.344-349
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    • 2014
  • $RuO_2$-based high frequency thick-film resistor paste was printed at the speed of 10, 100, 300 mm/sec on the AlN substrate, and then sintered at between 750 and $900^{\circ}C$. The sintered thick films were characterized in terms of printing and sintering conditions. With increasing printing speed, the thickness and roughness of sintered film increased. The resistance of the thick film resistor was reduced by increasing the printing speed from 10 to 100 mm/sec, but did not significantly change at 300 mm/sec speed. With increasing sintering temperature, the surface roughness and thickness of sintered resistor film decreased. The reduction rate was large in case of fast printed resistor. The resistance of the resistor increased up to $800^{\circ}C$ with sintering temperature, but again decreased at the higher sintering temperature.