• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2007년도 춘계학술발표회 초록집
• /
• pp.38-39
• /
• 2007

Chromium nitrids(Cr-N)박막은 경질박막재료이며 특히 PVD법을 제조한 CrN 박막은 다른 이원계 박막에 비해 높은 내마모성을 갖는다고 알려져 있다. 본 실험에서는 CrN박막에 Zr을 첨가하여 3원계의 CrZrN 박막을 합성하여 박막의 Zr 함량에 따른 표면경도 및 조도를 측정하고 Ball-on-disk type의 마모실험과 습도제어 하에서의 마모실험을 실시하였다. 박막의 Zr 함량이 증가함에 따라 박막의 표면경도가 증가하고 표면조도는 낮아지는 것을 알수 있었고, 그에 따라 마찰계수 값 또한 낮게 측정되었다. 습도제어하에서는 마찰계수 값은 비슷한 경향을 보였으나 습도가 매우 낮은 건조한 환경에서는 박막의 마찰계수 값이 높게 나타나는 경향을 보였다.

• 한국운동역학회지
• /
• 제15권3호
• /
• pp.161-173
• /
• 2005

Recently among several tennis techniques forehand stroke has been greatly changed in the aspect of spin, grip and stance. The most fundamental factor among the three factors is the stance which consists of open, square and closed stance. The purpose of this study was to investigate the relations between the segments of the body, the three dimensional anatomical angle according to open stance patterns during forehand stroke in tennis. For the movement analysis three dimensional cinematographical method(APAS) was used and for the calculation of the kinematic variables a self developed program was used with the LabVlEW 6.1 graphical programming(Johnson, 1999) program. By using Eular's equations the three dimensional anatomical Cardan angles of the joint and racket head angle were defined 1. In three dimensional maximum linear velocity of racket head the X axis showed $11.41{\pm}5.27m/s$ at impact, not the Y axis(horizontal direction) and the z axis(vertical direction) maximum linear velocity of racket head did not show at impact but after impact this will resulted influence upon hitting ball It could be suggest that Y axis velocity of racket head influence on ball direction and z axis velocity influence on ball spin after impact. the stance distance between right foot and left foot was mean $74.2{\pm}11.2m$. 2. The three dimensional anatomical angular displacement of shoulder joint showed most important role in forehand stroke. and is followed by wrist joints, in addition the movement of elbow joints showed least to the stroke. The three dimensional anatomical angular displacement of racket increased flexion/abduction angle until the impact. after impact, The angular displacement of racket changed motion direction as extension/adduction. 3. The three dimensional anatomical angular displacement of trunk in flexion-extension showed extension all around the forehand stroke. The angular displacement of trunk in adduction-abduction showed abduction at the backswing top and adduction around impact. while there is no significant internal-external rotation 4. The three dimensional anatomical angular displacement of hip joint and knee joint increased extension angle after minimum of knee joint angle in the forehand stroke, The three dimensional anatomical angular displacement of ankle joint showed plantar flexion, internal rotation and eversion in forehand stroke. it could be suggest that the plantar pressure of open stance during forehand stroke would be distributed more largely to the fore foot. and lateral side.

• 한국운동역학회지
• /
• 제17권2호
• /
• pp.83-91
• /
• 2007

This experiment studied the change in a human's control of his or her static posture by analyzing the stabilogram diffusion and, by using the said study, evaluated the control ability of different groups with different experiences. The postures had a rising requirement of heel-rise according to three conditions: heel-toe, ball, toe; the groups were divided into dance major student and non-dance majors. The results of the critical points according to posture did not show a direct relation with the change in postures that had a rising requirement of heel-rise. The diffusion coefficient(D) had greater stochastic activity for short-term regions that utilize open-loop controls without feedback than for long-term regions that used closed-loop controls with feedback to maintain balance. The directional results of the body undergoing disturbance showed that A/P direction's diffusion coefficient (D) was larger than that of M/L direction. Both feet's planar diffusion coefficients were a linear combination of the diffusion coefficients calculated for the x and y axis. In studying the different abilities to control posture between a dance major student and a non-dance majors, a comparison of open-loop control's diffusion coefficient(D) was effective, and dance major student had superior control ability to that of non-dance majors.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• 제5권2호
• /
• pp.175-178
• /
• 2005

In the present paper, we observe a relation between fuzzy norms and induced crisp norms on a linear space. We first prove that if $\rho_1,\;\rho_2$ are equivalent fuzzy norms on a linear space, then for every $\varepsilon\in(0.1)$, the induced crisp norms $P_\varepsilon^1,\;and\;P_\varepsilon^2$, respectively are equivalent. Since the converse does not hold, we prove it under some strict conditions. And consider the following theorem proved in [8]: Let $\rho$ be a lower semicontinuous fuzzy norm on a normed linear space X, and have the bounded support. Then $\rho$ is equivalent to the fuzzy norm $\chi_B$ where B is the closed unit ball of X. The lower semi-continuity of $\rho$ is an essential condition which guarantees the continuity of $P_\varepsilon$, where 0 < e < 1. As the last result, we prove that : if $\rho$ is a fuzzy norm on a finite dimensional vector space, then $\rho$ is equivalent to $\chi_B$ if and only if the support of $\rho$ is bounded.

• 한국세라믹학회지
• /
• 제34권10호
• /
• pp.1027-1036
• /
• 1997

The reology and several physical properties of cements are studied by varying the different mineral composition and particle size distribution(PSD) of cements with closed circuit ball mill for high workability, low heat of hydration, and high strength. In this study, we found that the workability of concretes is related to the viscosity of cement, and affects to strength. Here, this workability is affected by mineral composition (C3A) and the PSD. Especially, rosin-rammer index and 44${\mu}{\textrm}{m}$ residue in the PSD of cements are affected to water demand, casting property, slump loss, strength of cements. From the above results, the conditions of cement for high workability, low heat of hydration and high strength are to use low C3A clinker, 5-10% slag addition, and to grind cement below 0.7 rosin-rammer index, above 3.5-4.5% 44 ${\mu}{\textrm}{m}$ residue, 4000$\pm$100 $\textrm{cm}^2$/g blaine. Such cements are, therefore, supurior to super low heat cement and slag-blended cement in comparing the physical properties of strength, slump, slump-flow, adiabetic temperature, etc.

• 한국응용과학기술학회지
• /
• 제20권2호
• /
• pp.130-140
• /
• 2003

In order to improve the lithium ion battery's performance, the carbon nanofibers were introduced to the anode electrode fabricated with natural graphite particles. The influence of structural adjustment of the particles by the introduction method of carbon nanofibers and the content of carbon nanofibers on the electrical property and charge/discharge characteristics of the electrode were investigated. The electrode fabricated with the mixture of 10 wt% of carbon nanofibers grown separately and 90 wt% of graphite particles showed an excellent discharge capacity of 400 mAh/g and the improved cycle performance. The improved performance could be explained by that the carbon nanofibers shortened and uniformly distributed on the surface of graphite particles by ball milling increased the stability for the intercalation/deintercalation of lithium ion and increased the electrical conductivity due to the closed packing between graphite particles.

• Journal of Power Electronics
• /
• 제9권1호
• /
• pp.74-84
• /
• 2009

The design and implementation of a high performance PID (Proportional Integral & Differential) style controller with zero-phase error tracking property is considered in this article. Unlike a ball screw driven system, the controller in a direct drive system should provide a high level of tracking performance while avoiding the problems due to the absence of the gear system. The stiff mechanical element in a direct drive system allows high precise positioning capability, but relatively high tracking ability with minimal position error is required. In this work, a feasible position controller named 'Unified PID controller' is presented. It will be shown that the function of the closed position loop can be designed into unity gain system in continuous time domain to provide minimal position error. The focus of this work is in two areas. First, easy gain tunable PID position controller without speed control loop is designed in order to construct feasible high performance drive system. Second, a simple but powerful zero phase error tracking strategy using the pre-designed function of the main control loop is presented for minimal tracking error in all operating conditions. Experimental results with a s-curve based position pattern commonly used in industrial field demonstrate the feasibility and effective performance of the approach.

• 한국응용과학기술학회지
• /
• 제38권2호
• /
• pp.532-542
• /
• 2021

본 연구의 목적은 골프 스윙 시 3가지 스탠스에서 클럽헤드 스피드와 볼의 정확성을 유지하기 위한 신체 전략을 하지의 운동학적 변인과 지면반력 변인을 통하여 알아보고자 하였다. 연구의 대상은 공식 핸디캡이 2인 남자골프선수 10명으로 하였다. 모든 대상자들은 스탠스 조건(스퀘어, 오픈, 클로즈드)에 따라 어드레스 자세를 유지한 후 스윙을 수행하였다. 3차원 동작분석 시스템과 지면반력기를 이용하여 각 스탠스에 따라 7번 아이언 풀스윙을 수행한 결과를 산출하였다. 연구결과로 신체중심의 변위, 고관절 각변위, 무릎관절 각변위는 차이가 나타나지 않았다. 발목관절 각변위는 어드레스부터 다운스윙까지 왼쪽에서 오픈 스탠스가 저측굴곡이 크게 수행되었고, 오른쪽에서 클로즈드 스탠스에서 저측굴곡이 크게 수행되었다. 지면반력에서 전후, 수직은 차이가 없었지만, 어드레스부터 테이크백까지 왼발은 오른쪽 방향, 오른발은 왼쪽 방향의 힘이 오픈이 클로즈드 스탠스보다 크게 나타났다. 결론적으로 다양한 스탠스에도 불구하고, 임팩트 시 동일한 자세를 유지하는 것이 클럽헤드 스피드와 볼의 방향에 긍정적으로 작용되는 것으로 판단된다.

• 대한물리의학회지
• /
• 제8권3호
• /
• pp.295-302
• /
• 2013

PURPOSE: The purpose of this study was to investigate the effect of short-term lumbar stabilization exercise to patients suffering from chronic low back pain(CLBP) on the strength of their lumbar flexor and extensor and the postural balance of them and to suggest effective treatment duration for them. METHODS: Study subjects were 20 patients with CLBP who's been reported the pain for more than 12 weeks. For these subjects, muscle strength of both extensor and flexor of lumbar and the balancing ability were measured before and after the intervention. Lumbar stabilization exercise was composed of matt, ball and sling exercise. The intervention was applied for total 12 sessions for 4 weeks (3 times a week) and each session was for 40 minutes. RESULT: For muscle strength of both extensor and flexor of lumbar, there was significant differences after the application of lumbar stabilization exercise(p<.05). For balancing ability, stabilization shows significant differences in all of the positions except PC(eyes closed on pillows)(p<.05). Distribution of weight shows no significant differences but it was generally distributed within normal range after the exercise and Fall index shows significant differences between before and after the exercise(p<.05). CONCLUSION: These results could have positive effect on deciding different periods of therapeutic intervention.

• 한국과학교육학회지
• /
• 제24권2호
• /
• pp.226-233
• /
• 2004

이 연구의 목적은 뇌 신경세포 활동의 비동기화 정도는 두피에서 측정된 뇌파의 전극전위간의 상관계수와 관련이 있을 것이라는 가설을 검증하고 그 가설을 이용하여 과학적인 사고과정에서 나타나는 뇌파의 특성을 기술하는 것이다. 초등학교 6학년과 중학교 1, 2학년을 대상으로 실험 설계, 인지갈등, 연계, 초인지등의 4단계의 과학적인 사고과정으로 이루어진 구슬굴리기 과제를 수행하는 과정에서 나타나는 뇌파와 안정상태의 뇌파를 19개의 두피전극에서 측정하였다. 연구결과, 전극전위간 상관계수가 작아질수록 뇌 신경세포의 비동기화 정도가 커졌으며, 안정상태에 비해 과학적인 사고과정에서 전전두엽과 전두엽의 전극전위간 상관계수가 감소하였다. 또한, 과학적인 사고과정에서 전전두엽과 전두엽의 뇌세포가 가장 많이 활성화되었다. 뇌파를 이용한 과학적 사고과정의 연구에서 뇌파의 주파수 특성뿐만 아니라 전극전위간 상관계수를 분석함으로써 좀 더 의미있는 결과를 얻을 수 있다고 생각한다.