• Title/Summary/Keyword: Acceleration coefficient

Search Result 296, Processing Time 0.024 seconds

Estimation of the Virtual Mass of Conical Nets using Circulating Water Channel (회류수조를 이요한 자루그물의 가상질량 추정)

  • 김현영
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.36 no.1
    • /
    • pp.60-65
    • /
    • 2000
  • The virtual mass of net is an important parameter in the analysis and control of net movement in the water. This experiment was performed with the purpose of getting a relation on the quantity of netting and virtual mass of trawl nets using the circulating water channel that can control flow speed. Twelve types of conical nets were examined. Resistance of the conical net at the steady and acceleration state was recorded as text on the personal computer through the tension meter and current meter. The results were obtained as follows ;1. Resistance(R) of the conical net is proportional to the degree of attack angle in the sam e amount of twine material.2. Coefficient of the resistance(Cd)could be defined by the following regression model as a function of Reynolds Number(Re). Cd=0.039Re-0.14743. Resistance(R) is proportional to TSA(Twine surface area) and defined as follows; R=21.398TSA-0.12194. Coefficient of virtual mass(CM) could be calculated by the following first order regression model. CM=37.557U-8.96845. Virtual mass is directly proportional to Volume of net(V) or d/l.

  • PDF

Development of Pulsating Type Electromagnetic Hammer Drive Systems (맥동파 전자해머 구동시스템의 개발)

  • Ahn, Dong-Jun;Nam, Hyun-Do
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.17 no.5
    • /
    • pp.269-274
    • /
    • 2016
  • This paper proposes the development of a low frequency electronic hammer drive system that is used to prevent scaling or clogging in the hopper process. The electro-mechanical hammering driving method involves the generation of vibration and impact energy. The operation principles of the electromagnetic hammer were considered by parallel/series spring coefficient analysis and the amount of kinetic energy generated was calculated from the product of the equivalent spring constant, which is coupled with the E core and the gap of between the E core and I core. In addition, the Pulsation Driving algorithm was applied to the proposed electromagnetic hammer to obtain the maximizing kinetic energy. This algorithm was then implemented by a logical AND operation process and micro-controller (atmega128) built in functions with a timer interrupt and PWM generation function. The driving circuit of the electromagnetic hammer was designed using the H-bridge type IGBT circuit. The experimental test was performed by usefulness of the developed electromagnetic hammer systems with the acceleration measurement method. The experimental result showed that the proposed system has good kinetic energy generation performance and can be applied to the hopper process.

Evaluation Methods of Cyclic Shear Stress Ratio for the Assessment of Liquefaction in Korea (국내 액상화 평가를 위한 진동전단응력비 산정)

  • Yoo, Byeong-Soo;Bong, Tae-Ho;Kim, Sung-Ryul
    • Journal of the Korean Geotechnical Society
    • /
    • v.35 no.6
    • /
    • pp.5-15
    • /
    • 2019
  • Usually, the cyclic shear stress ratio (CSR) for the assessment of liquefaction has been determined by performing ground response analysis or adopting simplified method suggested by Seed & Idriss with some modifications. In order to analyze the applicability of the CSR evaluation methods, the present study performed one-dimensional equivalent linear analysis and evaluated CSR based on design codes from FHWA, JRA, and KDS. The comparison of the CSR obtained from each code showed that the CSR from KDS showed the largest error with the analysis results. The reason is because KDS has an error, which defines the stress reduction coefficient applying the maximum acceleration at each depth, not the maximum cyclic shear stress mobilized in the soil.

Construction of Design Table for Envelope Curve Analysis of Base Isolated Buildings (면진건물의 포락해석을 위한 설계용 도표 산정면진건물의 포락해석을 위한 설계용 도표 산정면진건물의 포락해석을 위한 설계용 도표 산정)

  • Lee, Hyun-Ho;Cheon, Yeong-Soo
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.10 no.2
    • /
    • pp.59-67
    • /
    • 2006
  • The aim of this study is to evaluate the design table for envelope curve analysis of base isolated buildings, which represent the period of base isolated buildings and the lateral displacement of base isolation devices. For the construction of design table, $V_E$ spectrum, which represents the energy, is developed instead of acceleration of seismic hazard. Based on the seismic coefficient of UBC 97, boundary period $T_G$ and maximum velocity response $V_0$ are proposed considering Korea seismic hazard. Using $T_G$ and $V_0$, finally, $V_E$ spectrum is developed for the four types of soil conditions. Base on the $V_E$ spectrum, design table for envelope curve analysis is also developed for soil types.

Neighboring Vehicle Maneuver Detection using IMM Algorithm for ADAS (지능형 운전보조시스템을 위한 IMM 기법을 이용한 전방차량 거동추정기법)

  • Jung, Sun-Hwi;Lee, Woon-Sung;Kang, Yeonsik
    • Journal of Institute of Control, Robotics and Systems
    • /
    • v.19 no.8
    • /
    • pp.718-724
    • /
    • 2013
  • In today's automotive industry, there exist several systems that help drivers reduce the possibility of accidents, such as the ADAS (Advanced Driver Assistance System). The ADAS helps drivers make correct and quick decisions during dangerous situations. This study analyzed the performance of the IMM (Interacting Multiple Model) method based on multiple Kalman filters using the data acquired from a driving simulator. An IMM algorithm is developed to identify the current discrete state of neighboring vehicles using the sensor data and the vehicle dynamics. In particular, the driving modes of the neighboring vehicles are classified by the cruising and maneuvering modes, and the transition between the states is modeled using a Markovian switching coefficient. The performance of the IMM algorithm is analyzed through realistic simulations where a target vehicle executes sudden lane change or acceleration maneuver.

Comparative Studies of Heat Transfer Coefficients for Rocket Nozzle (로켓 노즐의 열전달계수 비교 연구)

  • Hahm, Hee-Cheol;Kang, Yoon-Goo
    • Journal of the Korean Society of Propulsion Engineers
    • /
    • v.16 no.2
    • /
    • pp.42-50
    • /
    • 2012
  • The goal of heat transfer studies is the accurate prediction of temperature and heat flux distribution on material boundaries. To this purpose, general-purpose computational fluid dynamics(CFD) code is used : FLUENT. Mass fluxes and pressure ratio are calculated for two types of nozzle. The comparative studies reveal that the computational results are in agreement with the experimental data. Also, heat transfer coefficients from FLUENT for one type of nozzle are very similar and agree well with the experimental data in the diverging part of the nozzle, but the calculated results are large in the converging part. The heat transfer coefficients from Bartz equation are over-predicted. We can consider various reasons for these differences, i.e., laminarization by the highly accelerated flow in the nozzle, turbulent flow model and grid generation.

Determination of taxiing resistances for transport category airplane tractive propulsion

  • Daidzic, Nihad E.
    • Advances in aircraft and spacecraft science
    • /
    • v.4 no.6
    • /
    • pp.651-677
    • /
    • 2017
  • For the past ten years' efforts have been made to introduce environmentally-friendly "green" electric-taxi and maneuvering airplane systems. The stated purpose of e-taxi systems is to reduce the taxiing fuel expenses, expedite pushback procedures, reduce gate congestion, reduce ground crew involvement, and reduce noise and air pollution levels at large airports. Airplane-based autonomous traction electric motors receive power from airplane's APU(s) possibly supplemented by onboard batteries. Using additional battery energy storages ads significant inert weight. Systems utilizing nose-gear traction alone are often traction-limited posing serious dispatch problems that could disrupt airport operations. Existing APU capacities are insufficient to deliver power for tractive taxiing while also providing for power off-takes. In order to perform comparative and objective analysis of taxi tractive requirements a "standard" taxiing cycle has been proposed. An analysis of reasonably expected tractive resistances has to account for steepest taxiway and runway slopes, taxiing into strong headwind, minimum required coasting speeds, and minimum acceptable acceleration requirements due to runway incursions issues. A mathematical model of tractive resistances was developed and was tested using six different production airplanes all at the maximum taxi/ramp weights. The model estimates the tractive force, energy, average and peak power requirements. It has been estimated that required maximum net tractive force should be 10% to 15% of the taxi weight for safe and expeditious airport movements. Hence, airplanes can be dispatched to move independently if the operational tractive taxi coefficient is 0.1 or higher.

Seismic Influence on Subsea Pipeline Stresses

  • Choi, Byoung-Yeol;Lee, Sang-Gil;Kim, Jin-Kwang;Oh, Jin-Soo
    • Journal of Advanced Research in Ocean Engineering
    • /
    • v.3 no.1
    • /
    • pp.1-14
    • /
    • 2017
  • The safety analysis of an earthquake is carried out during the operation of a subsea pipeline and an onshore pipeline. Several cases are proposed for consideration. In the case of a buried pipeline, permanent ground deformation by the earthquake and an increase of internal pressure by the acceleration of the earthquake should be considered. In the case of a subsea pipeline, a bending moment is caused by liquefaction of the backfill material on a trenched seabed, etc., which results in a high bending moment of the buried pipeline. The bending moment causes the collapse of the subsea pipeline or a leak of crude oil or gas, which results in economic loss due to enormous environmental contamination and social economic loss owing to operation functional failure. Thus, in order to prevent economic loss and operation loss, structurally sensitive design with regard to seismic characteristics must be performed in the buried pipeline in advance, and the negative impact on the buried pipeline must be minimized by conducting a thorough analysis on the seabed and backfilling material selection. Moreover, it is proposed to consider the selection of material properties for the buried pipeline. A more economical review is also required for detailed study.

Development of accelerated life test method for the wind turbine Gearbox using cumulative damage theory (누적손상이론을 이용한 풍력증속기의 가속수명시험법 개발)

  • Son, Ki-Su;Kwak, Hee-Sung;Kang, Change-Hoon;Cho, Jun-Haeng
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2005.11a
    • /
    • pp.693-697
    • /
    • 2005
  • This study was performed to develop accelerated life test method of the wind-turbine gearbox using accumulated damage theory that used to model the fatigue of parts that receive variable load. The accumulated damage theory was introduced, and the estimation of life and calculation of accelerated life test time was illustrated. As the actual application example, accelerated life test method of the gearbox was described. Life distribution of the wind-turbine gearbox was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 140,600 hours and 99% reliability for one test sample According to the accumulated damage theory, because test time can shorten in case increase test load, test time could be reduced by 1.2 years when we put the load 1.2 times of rated load than 0.93 times of rated load that is equivalent load calculated by load spectrum of the wind turbine. This time, acceleration coefficient was 21.3. This accelerated test method was used to develop accelerated test method of gear reducer, gear and bearing as well as the industrial gearbox and it is considered to be applied comprehensively to mechanical parts the fatigue of which is happened by load or pressure etc.

  • PDF

Measurement Criteria for Drag-Sled Type Slip Resistance Tester Based on Human Gait and Slip (인간의 보행 및 미끄러짐 특성에 기반한 끌기형 미끄러짐 저항 측정 조건)

  • Park, Jae-Suk;Kwon, Hyuck-Myun;Oh, Whan-Sup
    • Journal of the Korean Society of Safety
    • /
    • v.27 no.5
    • /
    • pp.179-184
    • /
    • 2012
  • This study was performed to find out the measurement criteria of slip resistance from analysis of human gait and slips. Many kinds of slip resistance testers were developed based on mechanical friction testers. But, there are, as yet, no unambiguous slip resistance measurement methodologies and generally accepted safety criteria or safety thresholds for estimating slipping hazard exposures. Also, there are variety of measuring conditions between those testers. The measurement criteria should be tested within the range of human slipping conditions observed in biomechanical studies. It's results should clearly consider whether the devices reflect the human slipping conditions. In this study a dragsled type friction tester, which was constructed in accordance with ISO 15133 basically, was used. Test conditions were set in order to determine the range of measurement criteria. It is shown that drag velocity should be more than 1 m/s, acceleration be more than 10 $m/s^2$, contact time be less than 0.1sec, and contact pressure be within 350~400 kPa.