• 대한물리치료과학회지
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• 제15권3호
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• pp.43-54
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• 2008

Background : We aimed to determine the effect of a mental practice on the electromyography (EMG) activity of the quadriceps femoris muscle of the affected side in a hemiplegic patient during sit-to-stand and stand-to-sit tasks. Methods : We recruited a male patient who had suffered from right hemiplegia. A single-subject experimental A-B-A design was used. The reliability of visual analysis, which was primarily employed in this study design, was supported by using the "2- standard-deviation band" method. The target motions consisted of two activities: sit-to-stand and stand-to-sit. The EMG measurements of the quadriceps femoris muscles of the affected and unaffected sides were made in 8 sessions in the baseline (A), mental-practice (B), and follow-up (A) phases. During the mental practice phase, the 10-min mental practice was performed, and the mental practice was withdrawn in the follow-up phase in order to identify the carry-over effects of the treatment. Data was calculated as the percentage of the ratio of the quadriceps EMG activity values of the affected side on unaffected side. Result : The percentage EMG-activity ratio showed a greater increase in the mental-practice phase than in the baseline, and it was maintained during the follow-up phase. Most of the data points in the mental-practice and follow-up phases were positioned above the "2-standard-deviation band." Conclusion : These findings suggest that mental practice can be used to improve the physical function of hemiplegic patients.

• 한국실내디자인학회논문집
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• 제15권6호
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• pp.77-88
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• 2006

According to critics and architects, non-linear structure is not only an organic form of space, but also a form of space detached from modem style. Accordingly, non-linear structure can be accepted as an alternative to what has remained unsolved by deconstructionist. However, they are criticized for not clarifying the interdependent relationship between non-linearity of space and cognitive structure of human being. They ended up remaining the hypothesis just an intuitive and abstract one. This research began on the basis that their hypothesis is hard to be objectified, and it needs further inquiry. The purpose of this thesis is to explore how the redundant factors constitute non-linear structures of digital media centered space design. Geometric compositions of space structure were analyzed to define what types of redundant factors are contrived in the process of visual information. This study about the visual form, researching the Information Theory, and then offer a quantitative analysis that makes those more objective. Space structure and geometric composition were analyzed to define what types of redundancy are contrived in the process of visual information. In particular, I put higher theoretical emphasis on what characteristics are ensued in the process of structuring spaces than any other subjects. Followings are the conclusion of analysis. First, as a result of examining, we can assume that NOX' space structure is not a chaotic form, but has an operating the form of its own. Second, in case of curvilinear, the structure was found redundancy on mid deviation ratio and discontinuous circular fabric. Although most of their structures appeared complex with a higher coherent constant, they were found to be stable factors because of the low deviation ratio between systems. The amount of surplus information was stable structure as well.

• 한국의류산업학회지
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• 제12권4호
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• pp.467-476
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• 2010

The purpose of this study was to develop a plausible methodology based on experimental data how to set up darts and split lines on 3D parametric body dressed with tight-fit garment. The results were as following: Through the process of making convex hull, the concave parts were straightened to make a convex hull, especially in the center part of bust, under breast part and scapular part. To figure out the optimum positions of darts and split lines, the inflection points of curve ratio were searched along the horizontal polylines of waist and bust. This procedures produced reliable results with low deviation. Using Rapidform, CATIA and Unigraphics, six patches of bodice patterns were drawn and aligned. Paired t-test results showed the outline and area between 3D surface and 2D were not significantly different, meaning this method could be adaptable when flattening 3D surfaces. The amount of waist dart measured on the pattern showed that the highest portion was allocated on 2nd dart(back), followed by 1st dart(back), 1st dart(front), 2nd dart(front)/side dart, and center back dart. A series of findings suggested that curve ration inflection point could be used as a guide to set up darts and split line on 3D parametric model with low deviation.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권1호
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• pp.35-41
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• 2003

In this paper statistics on the radiation field waveforms produced by stepped leaders just prior to lightning return strokes were described. As a parameter of stepped leader pulse characteristics, the time interval between the final leader pulse and return stroke peak, the pause time between stepped leaders, the ratio of the final leader peak to the return stroke peak and the stepped leader pulse width at half maximum were examined. The average time intervals between the final leader pulse and return stroke peak were about 16.2 and 14.8$mutextrm{s}$ for the positive and negative polarities, respectively. When the stepped leader approaches closely to ground, the time interval between leader steps was decreased and the mean value was about 17$mutextrm{s}$, and the present results were in reasonable agreement with the data observed in Florida and Japan. The large fraction of the ratios of the final stepped leader pulse to the lightning return stroke peak were distributed over the range from 5 to 35% and in average the ratio of the final leader pulse to the return stroke peak was 17.4$\pm$11.9% for the positive and 18.5$\pm$9.4% for the negative electric field waveforms. In addition, the mean pulse widths at half maximum of the stepped leaders are 1.4Us with a standard deviation of 0.9 for the positive Polarity and 2.2us with a standard deviation of 1.2 for the negative polarity, respectively.

• Steel and Composite Structures
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• 제46권3호
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• pp.385-401
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• 2023

Steel is becoming increasingly popular due to its high strength, excellent ductility, great assembly performance, and recyclability. In reality, steel structures serving for a long time in atmospheric, industrial, and marine environments inevitably suffer from corrosion, which significantly decreases the durability and the service life with the exposure time. For the mechanical properties of corroded steel, experimental studies are mainly conducted. The existing numerical analyses only evaluate the mechanical properties based on corroded morphology at the isolated time-in-point, ignoring that this morphology varies continuously with corrosion time. To solve this problem, the relationships between pit depth expectation, standard deviation, and corrosion time are initially constructed based on a large amount of wet-dry cyclic accelerated test data. Successively, based on that, an in-situ pitting evolution method for evaluating the residual tensile strength of corroded steel is proposed. To verify the method, 20 repeated simulations of mass loss rates and mechanical properties are adopted against the test results. Then, numerical analyses are conducted on 135 models of corrosion pits with different aspect ratios and uneven corrosion degree on two corroded surfaces. Results show that the power function with exponents of 1.483 and 1.091 can well describe the increase in pit depth expectation and standard deviation with corrosion time, respectively. The effect of the commonly used pit aspect ratios of 0.10-0.25 on yield strength and ultimate strength is negligible. Besides, pit number ratio α equating to 0.6 is the critical value for the strength degradation. When α is less than 0.6, the pit number increases with α, accelerating the degradation of strength. Otherwise, the strength degradation is weakened. In addition, a power function model is adopted to characterize the degradation of yield strength and ultimate strength with corrosion time, which is revised by initial steel plate thickness.

• 재활복지공학회논문지
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• 제8권1호
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• pp.41-46
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• 2014

본 논문에서는 잡음 상황에서 강인한 음성 특성을 나타내는 TE (teager energy) 기반의 특징벡터를 이용한 음성 검출 알고리즘을 제안하였다. 입력 신호에 TEO (teager energy operator)를 적용하고, 이를 이용하여 음성 검출 알고리즘에서 우수한 성능을 보여주는 파워 스펙트럼 편차를 구하였다. 또한, 제안된 음성 검출 알고리즘의 성능 향상을 위하여 통계적 모델 기반의 우도비를 TE 기반의 파워 스펙트럼 편차의 가중치 요소로 적용하였다. 제안된 알고리즘의 성능 검증을 위해서 전체 오차율, ROC (receiver operating characteristics), PESQ (perceptual evaluation of speech quality)와 같은 객관적 실험을 수행하였다. 실험결과 5dB SNR 이하의 낮은 SNR을 갖는 비 정상 잡음 환경에서 제안한 음성 검출 알고리즘이 약 2.6%의 전체 오차율 감소와 약 0.053의 PESQ 점수 향상을 나타내었다.

• 한국화재소방학회논문지
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• 제23권3호
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• pp.11-16
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• 2009

본 논문은 전기설비에서 사고 발생 징후를 검출하기 위한 방법을 기술하고 있다. 실험을 위해 전기설비의 부하는 백열전구로 구성하였고, 사고는 전기설비의 일부에 KS C IEC(Korea Standard C International Electrostatic Commission) 60112에 따른 내트래킹 시험장치를 연결하여 모의되었다. 모의사고는 정상상태에서 방전진전과 탄화형성 과정을 거쳐 트래킹파괴에 이르게 된다. 전기설비로부터 사고 징후 검출을 위해 전류 모니터를 이용하여 전기설비 전체의 전류를 측정하고 이를 분석하였다. 그 결과, 전류 파형의 특정 영역에서 사고의 진행 정도가 클수록 전류 펄스의 크기가 커지고, 발생 빈도도 증가하였다. 특히 전류파형에 대한 표준편차와 확률분포는 부하의 수와 무관하게 사고단계별로 뚜렷한 차이를 보였다.

• Advances in aircraft and spacecraft science
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• 제3권4호
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• pp.471-502
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• 2016

This paper presents the dynamic instability analysis of un-damped elastically supported piezoelectric functionally graded (FG) beams subjected to in-plane static and dynamic periodic thermomechanical loadings with uncertain system properties. The elastic foundation model is assumed as one parameter Pasternak foundation with Winkler cubic nonlinearity. The piezoelectric FG beam is subjected to non-uniform temperature distribution with temperature dependent material properties. The Young's modulus and Poison's ratio of ceramic, metal and piezoelectric, density of respective ceramic and metal, volume fraction exponent and foundation parameters are taken as uncertain system properties. The basic nonlinear formulation of the beam is based on higher order shear deformation theory (HSDT) with von-Karman strain kinematics. The governing deterministic static and dynamic random instability equation and regions is solved by Bolotin's approach with Newmark's time integration method combined with first order perturbation technique (FOPT). Typical numerical results in terms of the mean and standard deviation of dynamic instability analysis are presented to examine the effect of slenderness ratios, volume fraction exponents, foundation parameters, amplitude ratios, temperature increments and position of piezoelectric layers by changing the random system properties. The correctness of the present stochastic model is examined by comparing the results with direct Monte Caro simulation (MCS).

• 설비공학논문집
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• 제16권6호
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• pp.522-529
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• 2004

In this study, external condensation heat transfer coefficients (HTCs) of flammable refrigerants of propylene, propane, isobutane, butane, DME, and HFC32 were measured on a horizontal plain tube, 26 fpi low fin tube, and Turbo-C tube. All data were taken at the temperature of 39$^{\circ}C$ with a wall subcooling of 3∼8$^{\circ}C$. Test results showed a typical trend that condensation HTCs of flammable refrigerants decrease with increasing wall subcooling. HFC32 had the highest HTCs among the tested refrigerants showing 44% higher HTCs than those of HCFC22 while DME showed 28% higher HTCs than those of HCFC22. HTCs of propylene and butane were similar to those of HCFC22 while those of propane and isobutane were similar to those of HFC134a. Based upon the tested data, Nusselt's equation is modified to predict the plain tube data within a deviation of 3%. For 26 fpi low fin tube, Beatty and Katz equation predicted the data within a deviation of 7.3% for all flammable refrigerants tested. The heat transfer enhancement factors for the 26 fpi low fin and Turbo-C tubes were 4.6∼5.7 and 4.7∼6.9 respectively for the refrigerants tested indicating that the performance of Turbo-C tube is the best among the tubes tested.

• 응용통계연구
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• 제28권3호
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• pp.385-392
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• 2015

주성분분석은 차원축소를 위한 대표적 기법이다. 주성분분석에서 변수들이 측정단위가 다르거나 분산의 불균형이 심할 경우 흔히 변수를 표준화한 다음 분석할 것이 권장된다. 표준화 변환은 표준편차를 나누어주는 변환인데, 측정단위에 무관하게 만들기 위해서라면 평균을 나누어주는 변환도 고려해볼 수 있다. 표준화 변환을 한 다음 주성분분석하는 것은 상관행렬로 주성분분석하는 것과 같은데, 평균을 나누어주는 변환을 한 후 주성분분석하는 것은 변동계수와 관련된 행렬로 주성분분석하는 것과 같음을 보이고, 그렇게 변환을 한 다음 주성분분석을 실시하는 것이 왜 필요한가를 설명하였다.