• 한국전자파학회논문지
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• 제26권10호
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• pp.895-906
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• 2015

본 논문에서는 모바일 충전회로를 대상으로 IEC 규격의 EFT/B(Electric Fast Transient and Burst) 내성 시험을 수행할 때 전달되는 신호를 예측할 수 있는 방법론 및 모델을 제안한다. EFT/B 신호는 모바일 충전회로가 충전 중인 상태에서 전달되기 때문에 교류전원 단에서 부터 부하 단까지의 신호전달특성을, 모바일 충전회로에 교류전원이 연결된 상태에서 알아야할 필요가 있다. 이를 위하여 간단한 CDN(Coupling-Decoupling Network)을 설계 제작하였으며, 이것을 이용하여 교류전원이 연결되어 있을 때와 연결되어 있지 않을 때의 두 가지 경우에 대해서 모바일 충전회로의 S-parameter를 VNA(Vector Network Analyzer)를 이용하여 측정하였다. 그 결과, 측정된 모바일 충전회로의 S-parameter 특성은 전원의 연결 유무와 거의 무관하였으며, 이것을 근거로 하여 모바일 충전회로만의 전달특성을, 전원이 연결되지 않은 상태에서, 적절한 인터페이스를 제작하여 측정하였다. 실제 EFT/B 신호 입출력의 전달함수를 구하여 S-parameter 측정의 정확성을 검증하였다. 이렇게 측정된 특성을 이용하여 모바일 충전회로의 EFT/B 신호가 전달되는 특성을 효과적으로 예측할 수 있었음을 보였다.

• 공업화학
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• 제21권6호
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• pp.610-615
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• 2010

본 논문에서는 실험실적 규모의 반응기에서 수용액상 bis(2-chloroethyl) ether (BCEE)의 오존산화반응에 대한 연구를 수행하였다. 오존산화반응은 BCEE 용액이 포함되어 있는 반응기 바닥에 오존 기체를 주입하여 진행하였으며 $50{\pm}10mg/L$의 오존 농도로 80 min 반응시켜 완결하였다. BCEE의 오존산화처리 효율을 $BOD_5$, $COD_{Cr}$, 그리고 TOC의 변화로 측정하였다. BCEE의 오존산화반응결과 $COD_{Cr}$가 62.79%, TOC의 57.25% 감소된 것은 생분해 가능한 중간체가 생성되었음을 알 수 있다($BOD_5/COD_{Cr}$ = 0.39). 본 연구의 결과는 BCEE와 같은 비생분해성 물질을 포함하는 폐수가 오존산화처리 후에 생물학적 처리를 함으로써 성공적으로 처리될 수 있다는 것을 보여주었다. $30^{\circ}C$에서 유사 1차 반응속도 상수는 $2.00{\times}10^{-4}sec^{-1}$, 활성화 에너지는 $10.02kcal{\cdot}mol^{-1}$로 나타났다.

• 대한기계학회논문집A
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• 제26권12호
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• pp.2565-2573
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• 2002

A basic research was performed to ensure the usefulness of Small Punch-creep(SP-creep) test for residual life evaluation of heat resistant components effectively. This paper presents analytical results of initial stress and strain distributions in SP specimen caused by constant loading for SP-creep test and its experimental correlations with uniaxial creep(Ten-creep) test on 9Cr1MoVNb steel. It was shown that the initial maximum equivalent stress, ${\sigma}_{eq{\cdot}max}$ from FE analysis was correlated with steady-state equivalent creep strain rate, ${\epsilon}_{qf-ss'}$ rupture time, $t_r$, activation energy, Q and Larson-Miller Parameter, LMP during SP-creep deformation. The simple correlation laws, ${\sigma}_{sp}-{\sigma}_{TEN}$, $P_{sp}-{\sigma}_{TEN}\; and\; Q_{sp}-Q_{TEN}$ adopted to established a quantitative correlation between SP-creep and Ten-creep test data. Especially, the activation energy obtained from SP-creep test is linearly related to that from Ten-creep test at $650^{\circ}C$ as follows : $Q_{SP-P}\;{\risingdotseq}\;1.37 \;Q_{TEN},\; Q_{SP-{\sigma}}{\risingdotseq}1.53\; Q_{TEN}$.

• 열처리공학회지
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• 제13권6호
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• pp.383-390
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• 2000

The static creep behaviour of AlSl 420F stainless steel was investigated over the temperature range of $540{\sim}585^{\circ}C$ and the stress range of $13{\sim}19kg/mm^2$ (127.4~186.2MPa). Constant stress creep tests were carried out in the experiment. Measured stress exponent, n, for the creep deformation of the alloy under the given conditions was found to vary at the range of 9.59, 9.15, 8.78, and 8.53 for the temperature of 540, 555, 570, and $585^{\circ}C$ respectively. The activation energy, Qc, for the creep deformation was 106.42, 102.58,97.81, and 94.58 kcal/mole for the stress of 13, 15, 17, and $19kg/mm^2$, respectively. Lason-Miller parameter, P, for the crept specimens for AlSl 420F stainless steel was measured as $P=T(log\;t_T+21)$. The empirical static creep rate obtained by the regression analysis was as follows. $${\varepsilon}={\exp}[(3.79{\times}10^{-2}{\sigma}+2.722)T-3.0747{\sigma}+28.109]{\times}{\sigma}^{(-2.367{\times}10^{-2}T+22.33)}{\exp}\left[-\frac{(-2.015{\sigma}+132.580){\times}10^3}{RT}\right]$$ The failure plane were observed, intergranular fracture was dominated by r (round) type crack over the experimental range.

• Physical Therapy Rehabilitation Science
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• 제9권2호
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• pp.74-81
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• 2020

Objective: To prevent low back pain, an objective evaluation tool to evaluate pelvic mobility and exercise to improve the flexibility of the lumbar region is needed. The purpose of this study was to compare the results of pelvic mobility measurements using the Wii Balance Board (WBB) and Sensbalance Therapy Cushion (STC), evaluate the usefulness of the STC as a tool for measuring pelvic mobility. Design: Cross-sectional study. Methods: Fifty healthy subjects participated in this study. The subjects performed pelvic mobility range, proprioception, reaction time and reach of the arm using the STC. The pelvic movement parameter was measured two times to determine the intra-rater reliability. To measure the correlation between lumbar muscle tension and pelvic mobility, Myovision was used to measure tension of L4, L5 level erector spinae muscle. Correlations between measured variables were checked to determine the validity of the pelvic mobility assessment tool. Results: STC showed high test-retest reliability in pelvic tilt measurement and reaching task [intraclass correlation coefficients (3,1)=0.804-0.915]. The relationship between WBB and STC showed a significant positive correlation with the pelvic tilt and reaching task (p<0.05). Posterior tilt and erector spinae activation (Lt. L5) showed a significant negative correlation (p<0.05). Left, right tilt and erector spinae activation (L5) showed a significant negative correlation (p<0.05). Conclusions: This study confirmed the advantages of the STC and found efficiency as an objective measuring device of pelvic mobility.

• 한국전기전자재료학회논문지
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• 제12권1호
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• pp.44-49
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• 1999

In this study, microstructure and electrical conductivity of {(G $d_2$ $O_3$)$_{0.75}$( $Y_2$ $O_3$)$_{0.25}$}$_{x}$ (Ce $O_2$)$_{1-x}$ (0.01$\leq$x$\leq$0.25) was investigated as a function of composition x. GYO addition(x) increased the bulk density and G $d_2$ $O_3$ was found to be monoclinic at x>0.15. From the change of the lattice parameter with the addition(x), GYO solution limit for ceria was exceeded in the range of x=0.05 to 0.09. Thermal expansion coefficient(15~17$\times$10$^{-6}$ $^{\circ}C$) of GYC samples at x=0.01 to 0.07 was higher in value than that of 8YSZ(10.8$\times$10$^{-6}$ $^{\circ}C$). The electrical conductivity of GYC samples at x=0.05 showed the maximum(0.01S/cm) in value at 1073K which was 2 times higher than that of 8YSZ. The activation energy for the electrical conduction was determined to be 0.60eV in the temperature range of 1073K.3K..3K.

• Journal of Ceramic Processing Research
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• 제20권1호
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• pp.63-68
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• 2019

We investigated the effects of Al2O3 addition on (1-x)Li2B4O7-xAl2O3 (LBAO; x = 0, 0.005, 0.01, 0.05, 0.07, and 0.1) glasses. The glasses were synthesized by a conventional melt-quench method. Structural transformations of the LBAO glasses were assessed via X-ray diffraction analysis. Estimations of ΔT, KGS = (Tc-Tg)/(Tm-Tc), activation energy, and the Avrami parameter were performed using differential thermal analysis and differential scanning calorimetry. An interpretation of non-isothermal kinetics of the crystallization process is presented using the modified Ozawa equation. The activation energy E increased from 3.3 to 3.5 eV for the LBAO (x < 0.01) glasses whereas those of the LBAO (x > 0.05) glasses slightly increased from 3.75 to 4.05 eV. The exponent n was estimated to be 3.9 ± 0.1 for the LBAO (x < 0.01) glasses and 3.2 ± 0.02 for the LBAO (x > 0.05) glasses. Microstructural characterization of the glassy and crystalline phases using atomic force microscopy was investigated. The effects of Al2O3 on the LBAO glasses include a decreased nucleation rate in the crystallization process and a significantly reduced crystal size.

• The Journal of Korean Physical Therapy
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• 제34권6호
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• pp.298-303
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• 2022

Purpose: The purpose of this study was to figure out how PAP (Post-Activation Potentiation) phenomenon affects short-term performance efficiently. Methods: This study was conducted with 18 Taekwondo athletes and 16 healthy adults. By using isokinetic dynamometer, two different intervention, TDP (Top-down program) and BUP (Bottom-up program), were performed to measure isokinetic parameter; (peak torque: PT, total work: TW, average power: AP, and average torque: AT) of knee extensor for intragroup, intergroup comparison and two-way ANOVA. Results: The Taekwondo athletes group showed statistically significant differences in all isokinetic parameters PT, TW, AP, and AT after TDP (p<0.05). However, in the healthy adult group, the difference in isokinetic parameters according to the exercise sequence was not statistically significant. (p>0.05). PT and TW at TDP were statistically significant (p<0.05) when the rate of change in TDP and BUP was compared and analyzed considering the difference in physical ability between the Taekwondo athlete group and the healthy adult group. However, AP and AT were not statistically significant. Finally, when examining the interaction between the two groups and two exercise sequence according to isokinetic parameters, only TW (p<0.05) showed a statistically significant interaction, while PT (P=0.099), AP (P=0.103), and AT (P=0.096) did not. This study suggests that short-term performance can be improved through the PAP phenomenon when TDP is applied to the Taekwondo group. Conclusion: According to our result, for Taekwondo athletes, if the goal is to improve short-term performance just before the main game, we suggest a training program through TDP.

• 한국산학기술학회논문지
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• 제21권2호
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• pp.189-194
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• 2020

본 논문에서는 신경망을 학습하는 데 가장 많이 사용되고 있는 경사하강법에 대해 분석하였다. 학습이란 손실함수가 최소값이 되도록 매개변수를 갱신하는 것이다. 손실함수는 실제값과 예측값의 차이를 수치화 해주는 함수이다. 경사하강법은 오차가 최소화되도록 매개변수를 갱신하는데 손실함수의 기울기를 사용하는 것으로 현재 최고의 딥러닝 학습알고리즘을 제공하는 라이브러리에서 사용되고 있다. 그러나 이 알고리즘들은 블랙박스형태로 제공되고 있어서 다양한 경사하강법들의 장단점을 파악하는 것이 쉽지 않다. 경사하강법에서 현재 대표적으로 사용되고 있는 확률적 경사하강법(Stochastic Gradient Descent method), 모멘텀법(Momentum method), AdaGrad법 그리고 Adadelta법의 특성에 대하여 분석하였다. 실험 데이터는 신경망을 검증하는 데 널리 사용되는 MNIST 데이터 셋을 사용하였다. 은닉층은 2개의 층으로 첫 번째 층은 500개 그리고 두 번째 층은 300개의 뉴런으로 구성하였다. 출력 층의 활성화함수는 소프트 맥스함수이고 나머지 입력 층과 은닉 층의 활성화함수는 ReLu함수를 사용하였다. 그리고 손실함수는 교차 엔트로피 오차를 사용하였다.

• 폴리머
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• 제25권6호
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• pp.866-875
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• 2001

본 연구에서는 고온 산화분위기 하에서 탄소/탄소 복합재료의 열적 향상을 위해 사용된 tetraethylorthosilicate(TEOS)의 첨가량에 따른 복합재료의 kinetic parameter에 기초한 열분해 메카니즘 및 열안정성을 열중량분석기(TGA)를 사용하여 고찰하였다 TEOS를 함유한 탄소/탄소 복합재료의 kinetic parameter, 즉 열분해 활성화 에너지 ($E_d$), 반응차수(n), 지수앞 인자 (A)는 각각 136 kJ/mol, 0차, 및 2.3$\times$$10^9s^{-1}$을 나타내었으며, 특히 IPDT 및 $E_d$로부터 살펴본 복합재료의 열안정성은 탄소/탄소 복합재료에 TEOS가 첨가되면 크게 향상되었는데, 이는 산소에 대한 산화방지막, 즉 $SiO_2$의 형성으로 인한 복합재료 표면에서의 카본 활성종에 산소의 침투를 방해하여 TEOS를 함유한 복합재료가 이를 함유하지 않은 것에 비하여 표면 산화 속도가 감소되어 열안정성이 증가하였다고 사료된다.