• 제목/요약/키워드: simplified analytical model

검색결과 195건 처리시간 0.026초

인체 하지부 근골격계 모델 및 의자에서 일어서는 동작 시 근력 예측 (A Musculoskeletal Model of a Human Lower Extremity and Estimation of Muscle Forces while Rising from a Seated Position)

  • 조영남;유홍희
    • 한국소음진동공학회논문집
    • /
    • 제22권6호
    • /
    • pp.502-508
    • /
    • 2012
  • An analytical model for a human body is important to predict muscle and joint forces. Because it is difficult to estimate muscle or joint forces from a human body, the objective of this study is the development of a reliable analytical model for a human body to evaluate the lower extremity muscle and joint forces. The musculoskeletal system of the human lower extremity is modeled as a multibody system employing the Hill-type muscle model. Muscle forces are determined to minimize energy consumption, and we assume that motion is constrained in the sagittal plane. Muscle forces are calculated through an equilibrium analysis while rising from a seated position. The musculoskeletal model consists of four segments. Each segment is a rigid body and connected by frictionless revolute joints. Muscles of the lower extremity are simplified to seven muscles with those that are not related to the sagittal plane motion are ignored. Muscles that play a similar role are combined together. The results of the present study are compared with experimental results to validate the lower extremity model and the assumptions of the present study.

In0.8Ga0.2As HEMT 소자에서 Output-conductance가 차단 주파수에 미치는 영향에 대한 연구 (Effect of Output-conductance on Current-gain Cut-off frequency in In0.8Ga0.2As High-Electron-mobility Transistors)

  • 노태범;김대현
    • 센서학회지
    • /
    • 제29권5호
    • /
    • pp.324-327
    • /
    • 2020
  • The impact of output conductance (go) on the short-circuit current-gain cut-off frequency (fT) in In0.8Ga0.2As high-electron-mobility transistors (HEMTs) on an InP substrate was investigated. An attempted was made to extract the values of fT in a simplified small-signal model (SSM) of the HEMTs, derive an analytical formula for fT in terms of the extrinsic model parameters of the simplified SSM, which are related to the intrinsic model parameters of a general SSM, and verify its validity for devices with Lg from 260 to 25 nm. In long-channel devices, the effect of the intrinsic output conductance (goi) on fT was negligible. This was because, from the simplified SSM perspective, three model parameters, such as gm_ext, Cgs_ext and Cgd_ext, were weakly dependent on goi. However, in short-channel devices, goi was found to play a significant role in degrading fT as Lg was scaled down. The increase in goi in short-channel devices caused a considerable reduction in gm_ext and an overall increase in the total extrinsic gate capacitance, yielding a decrease in fT with goi. Finally, the results were used to infer how fT is influenced by goi in HEMTs, emphasizing that improving electrostatic integrity is also critical importance to benefit fully from scaling down Lg.

풍력발전기용 볼 베어링의 단순화 볼 모델을 이용한 해석기법 연구 (A Study on a Finite Element Analysis Method Using Simplified Ball Models of Wind Turbine Ball Bearings)

  • 김승우;송정우;홍준표;강종훈
    • 풍력에너지저널
    • /
    • 제14권4호
    • /
    • pp.21-28
    • /
    • 2023
  • This study focuses on the analysis of slewing ball bearings in wind turbines. Slewing bearings have an outer diameter of several meters, and hundreds of balls are in contact with the raceway. Due to the large number of balls and raceway contact conditions, it is difficult to accurately analyze contact stresses using general analysis techniques. To analyze the contact stress of a slewing ball bearing, the sub-modeling method is applied, which is a technique that first analyzes the displacement of the entire model and then analyzes the local stress at the point of maximum displacement. In order to reduce the displacement analysis time of the entire ball bearing, the technique of replacing the ball with a nonlinear spring is adopted. The analytical agreement of the simplified model was evaluated by comparing it with a solid mesh model of the ball for three models with different spring attachment methods. It was found that for the condition where a large turnover moment is applied to the bearing, increasing the number of spring elements gives the closest results to modeling the ball with a solid mesh.

주파수변조 구동에 의한 가변릴럭턴스 스텝핑모우터의 불안정 해석 (Analysis of Dynamic Instability in a Variable-reluctance Stepping Motor Operated on Frequency-modulated Supply)

  • 권용수
    • 대한전기학회:학술대회논문집
    • /
    • 대한전기학회 1994년도 하계학술대회 논문집 A
    • /
    • pp.114-118
    • /
    • 1994
  • A comprehensive analytical study of frequency-modulated supply of the dynamic instability in a variable-reluctance stepping motor, is described. It is shown that stability can be achieved by frequency modulation provided that the phase displacement between the modulating signal and the rotor velocity oscillation lies between certain limits. A simplified expression is derived. based on the assumption of high inertia. This model is used to obtain a qualitative understanding of how frequency modulation influences the dynamic stability of the variable-reluctance motor.

  • PDF

공정간 최적 완충재고 설정에 관한 연구 (A study on the Determination of Optimal Buffer Stock in Inter-Process)

  • 황규완;하정진
    • 산업경영시스템학회지
    • /
    • 제17권30호
    • /
    • pp.135-145
    • /
    • 1994
  • There has been increasing interest in modeling the effect of buffer stock in automatic flow lines such as transfer line, assembly line and process line. The purpose of this paper is to determine the optimal buffer stock for a two-stage process line of industry that minimize a expected cost considering line efficiency and buffer stock Analytical method for the simplified model is applied and computer simulation is conducted to real numerical example.

  • PDF

Plank's Equation의 변형에 의한 식품의 동결시간 예측 (Studies on the Freezing Time Prediction of Foodstuffs by Plank's Equation of Modification)

  • 정진웅;공재열
    • 한국식품과학회지
    • /
    • 제20권2호
    • /
    • pp.280-286
    • /
    • 1988
  • 이상과 같이, 기존 data의 정확도에 대한 고찰과 본 연구에서 소개한 단순한 해석적 방법에 의한 식품의 동결 시간예측 model로서, 실제 측정한 시료별 실험치와 기존 model을 비교 검토하였다. 기 발표된 lean beef등 109개의 data중, Hung & Thompson의 data는 Nagaoka 및 Pham의 model에, Cleland & Earle의 data는 Hung $ Thompson의 model에 매우 접근함을 볼 수 있으며, 시료별로 살펴볼 때, tylose등 5품목의 시료는 Nagaoka 및 Pham의 model에 잘 적용됨을 알 수 있다. 그러나 본 실험에서 사용한 pine mushroom등 4품목은 Cleland & Earle, Hung & Tompson 및 Pham의 model에 잘 부합되며, 제안된 model의 간편성과 정확도에 있어서도 단지 3가지의 실험적 매개변수와 7가지의 물성치 만으로 실험치와 비교한 결과, 공학적 최소오차 범위인 ${\pm}10%$ 이내로 나타났다.

  • PDF

푸리에 급수를 이용한 이족보행로봇의 보행 궤적 해석해 생성 (Analytic Solution for Stable Bipedal Walking Trajectory Generation Using Fourier Series)

  • 박일우;백주훈
    • 제어로봇시스템학회논문지
    • /
    • 제15권12호
    • /
    • pp.1216-1222
    • /
    • 2009
  • This article describes a simple method for generating the walking trajectory for the biped humanoid robot. The method used a simple inverted model instead of complex multi-mass model and a reasonable explanation for the model simplification is included. The problem of gait trajectory generation is to find the solution from the desired ZMP trajectory to CoG trajectory. This article presents the analytic solution for the bipedal gait generation on the bases of ZMP trajectory. The presented ZMP trajectory has Fourier series form, which has finite or infinite summation of sine and cosine functions, and ZMP trajectory can be designed by calculating the coefficients. From the designed ZMP trajectory, this article focuses on how to find the CoG trajectory with analytical way from the simplified inverted pendulum model. Time segmentation based approach is adopted for generating the trajectories. The coefficients of the function should be designed to be continuous between the segments, and the solution is found by calculating the coefficients with this connectivity conditions. This article also has the proof and the condition of solution existence.

Transformation Approach to Model Online Gaming Traffic

  • Shin, Kwang-Sik;Kim, Jin-Hyuk;Sohn, Kang-Min;Park, Chang-Joon;Choi, Sang-Bang
    • ETRI Journal
    • /
    • 제33권2호
    • /
    • pp.219-229
    • /
    • 2011
  • In this paper, we propose a transformation scheme used to analyze online gaming traffic properties and develop a traffic model. We analyze the packet size and the inter departure time distributions of a popular first-person shooter game (Left 4 Dead) and a massively multiplayer online role-playing game (World of Warcraft) in order to compare them to the existing scheme. Recent online gaming traffic is erratically distributed, so it is very difficult to analyze. Therefore, our research focuses on a transformation scheme to obtain new smooth patterns from a messy dataset. It extracts relatively heavy-weighted density data and then transforms them into a corresponding dataset domain to obtain a simplified graph. We compare the analytical model histogram, the chi-square statistic, and the quantile-quantile plot of the proposed scheme to an existing scheme. The results show that the proposed scheme demonstrates a good fit in all parts. The chi-square statistic of our scheme for the Left 4 Dead packet size distribution is less than one ninth of the existing one when dealing with erratic traffic.

Component method model for predicting the moment resistance, stiffness and rotation capacity of minor axis composite seat and web site plate joints

  • Kozlowski, Aleksander
    • Steel and Composite Structures
    • /
    • 제20권3호
    • /
    • pp.469-486
    • /
    • 2016
  • Codes EN 1993 and EN 1994 require to take into account actual joint characteristics in the global analysis. In order to implement the semi-rigid connection effects in frame design, knowledge of joint rotation characteristics ($M-{\phi}$ relationship), or at least three basic joint properties, namely the moment resistance $M_R$, the rotational stiffness $S_j$ and rotation capacity, is required. To avoid expensive experimental tests many methods for predicting joint parameters were developed. The paper presents a comprehensive analytical model that has been developed for predicting the moment resistance $M_R$, initial stiffness $S_{j.ini}$ and rotation capacity of the minor axis, composite, semi-rigid joint. This model is based on so-called component method included in EN 1993 and EN 1994. Comparison with experimental test results shows that a quite good agreement was achieved. A computer program POWZ containing proposed procedure were created. Based on the numerical simulation made with the use of this program and applying regression analysis, simplified equations for main joint properties were also developed.

The effect of foundation soil behavior on seismic response of long bridges

  • Hoseini, Shima Sadat;Ghanbari, Ali;Davoodi, Mohammad;Kamal, Milad
    • Geomechanics and Engineering
    • /
    • 제17권6호
    • /
    • pp.583-595
    • /
    • 2019
  • In this paper, a comprehensive investigation of the dynamic response of a long-bridge subjected to spatially varying earthquake ground motions (SVEGM) is performed based on a proposed analytical model which includes the effect of soil-structure interaction (SSI). The spatial variability of ground motions is simulated by the powerful record generator, SIMQKE II. Modeling of the SSI in the system is simplified by replacing the pile foundations and soil with sets of independent equivalent linear springs and dashpots along the pile groups. One of the most fundamental objectives of this study is to examine how well the proposed model simulates the dynamic response of a bridge system. For this purpose, the baseline data required for the evaluation process is derived from analyzing a 3D numerical model of the bridge system which is validated in this paper. To emphasize the importance of the SVEGM and SSI, bridge responses are also determined for the uniform ground motion and fixed base cases. This study proposing a compatible analytical model concerns the relative importance of the SSI and SVEGM and shows that these effects cannot be neglected in the seismic analysis of long-bridges.