Jaegyeong Shim

This research has been performed to estimate the hunting motion hysteresis of railway passenger cars. An old and a new car with almost the same structure are chosen for analysis models. To solve a set of simultaneous equations of motion that are strongly coupled with creep relations effectively, a shooting algorithm in which the nonlinear relations are regarded as a two-point boundary value problem is adopted. The bifurcation theory is applied to the dynamic analysis to distinguish the differenc

In order to utilize a parallel mechanism as a machine tool component, it is important to estimate the errors of its end-effector due to the uncertainties in parts. This study proposes an error analysis for a new parallel device, a cubic parallel mechanism. For the parallel device, we consider two kinds of errors. One is a static error due to link stiffness and the other is a dynamic error due to clearances in the parts. In this study, we propose a stiffness model for the cubic parallel mechanism

In the in-line four-cylinder engine, it is well known that the shaking force is due to the vertical second harmonic acceleration components of the pistons. This paper proposes a kinematic conceptual design method to determine the kinematic structure of a feasible in-line four-cylinder variable compression ratio (VCR) engine and its dimensions that would yield a lower vertical second harmonic acceleration at joints. Through type and dimensional synthesis, candidate VCR engine mechanisms are chose

본고는 학문 목적 한국어 교재 내 읽기 텍스트의 다양성과 난이도를 살펴보고, 이를 현재 학문 목적 한국어 교육의 상황에 비추어 교육적 함의를 이끌어 내는 것을 목적으로 하였다. 이를 위하여, 3종의 학문 목적 한국어 교재 내의 읽기 텍스트들을 대상으로 주제, 기능, 장르의 다양성을 분석하였고, 학문 목적 한국어 읽기 텍스트 말뭉치와 일반 목적 한국어 읽기 텍스트 말뭉치를 구축하여 문장 길이, 어휘 난이도, 어미 난이도를 통해 텍스트 난이도를 산출, 그 차이를 통계적으로 검증하였다. 연구 결과, 학문 목적 한국어 읽기 텍스트는 ‘인문/사회’ 영역의 주제, 제보적 기능의 텍스트, 설명문 장르에 편중되어 있었으며, 텍스트 난이도는 일반 목적 고급 읽기 텍스트의 난이도 수준과 일치하였다. 이를 바탕으로 본 연구는 향후 학문 목적 한국어 읽기 텍스트는 현재의 학문 목적 학습자들의 일반적 등급에 맞게 최소한 중급 수준에서부터 선정되어야 할 필요성이 있으며, 텍스트의 다양성의 제고가 필요함을 제

Type synthesis of two-degrees-of-freedom (DOF) planar mechanisms has been carried out using graph theory to determine the possible kinematic structures of variable compression ratio (VCR) engine mechanisms with two to three independent loops, and has resulted in the structures of 87 mechanisms satisfying search specification. By applying evaluation criteria to the enumerated mechanisms, the kinematic structures of three mechanisms are selected as suitable VCR engine mechanisms and verified by an