• Interaction and multiscale mechanics
• /
• 제1권1호
• /
• pp.83-101
• /
• 2008

A derivation is given of two-scale models that are able to describe deformation and flow in a fluid-saturated and progressively fracturing porous medium. From the micromechanics of the flow in the cavity, identities are derived that couple the local momentum and the mass balances to the governing equations for a fluid-saturated porous medium, which are assumed to hold on the macroscopic scale. By exploiting the partition-of-unity property of the finite element shape functions, the position and direction of the fractures are independent from the underlying discretization. The finite element equations are derived for this two-scale approach and integrated over time. The resulting discrete equations are nonlinear due to the cohesive crack model and the nonlinearity of the coupling terms. A consistent linearization is given for use within a Newton-Raphson iterative procedure. Finally, examples are given to show the versatility and the efficiency of the approach.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제14권4호
• /
• pp.1543-1561
• /
• 2020

Taxonomy of human brain activity is a complicated rather challenging procedure. Due to its multifaceted aspects, including experiment design, stimuli selection and presentation of images other than feature extraction and selection techniques, foster its challenging nature. Although, researchers have focused various methods to create taxonomy of human brain activity, however use of multivariate pattern analysis (MVPA) for image recognition to catalog the human brain activities is scarce. Moreover, experiment design is a complex procedure and selection of image type, color and order is challenging too. Thus, this research bridge the gap by using MVPA to create taxonomy of human brain activity for different categories of images, both colored and gray scale. In this regard, experiment is conducted through EEG testing technique, with feature extraction, selection and classification approaches to collect data from prequalified criteria of 25 graduates of University Technology PETRONAS (UTP). These participants are shown both colored and gray scale images to record accuracy and reaction time. The results showed that colored images produces better end result in terms of accuracy and response time using wavelet transform, t-test and support vector machine. This research resulted that MVPA is a better approach for the analysis of EEG data as more useful information can be extracted from the brain using colored images. This research discusses a detail behavior of human brain based on the color and gray scale images for the specific and unique task. This research contributes to further improve the decoding of human brain with increased accuracy. Besides, such experiment settings can be implemented and contribute to other areas of medical, military, business, lie detection and many others.

• 한국수자원학회논문집
• /
• 제49권12호
• /
• pp.995-1006
• /
• 2016

IPCC 제5차 평가보고서에 따르면 극한강우의 빈도 및 강도가 증가할 가능성이 매우 높을 것으로 예측되고 있다. 실제로 극한강우에 따른 침수피해가 증가하고 있으며, 이에 따라 기후변화의 영향을 반영한 미래 확률강우량 추정이 필요하다. 본 연구에서는 기후변화 RCP 8.5 시나리오로부터 도출된 미래 연 최대 일강수량 자료의 추세분석과 scale-invariance 기법을 이용하여 미래 확률강우량을 추정하였다. 먼저, 기상청 관할 60개 기상관측소의 관측 강우자료를 이용하여 관측소별로 스케일 특성을 검토한 후, 현재기후 모의자료를 이용하여 scale-invariance 기법의 적용가능성을 검증하였다. 그 후, 미래 일 강수량 시계열을 scale-invariance 특성에 따라 유도된 IDF 곡선식에 적용하여 기후변화의 영향을 반영한 지속시간별 확률강우량을 추정하였다. 대부분의 지점에서 확률강우량이 증가할 것으로 예측되었으나, 일부 지역의 경우에는 감소할 가능성도 있음을 살펴볼 수 있다.

• The Journal of Korean Physical Therapy
• /
• 제20권4호
• /
• pp.21-28
• /
• 2008

Purpose: We measured the Oswestry Low Back Pain Disability Index (OLBPDI) and related factors in patients with low back pain. Methods: The sample consisted of 50 patients who received physical therapy at the physical therapy units of the Andong Seoul Sintong Clinic, St. Luke Clinic, and Yeongju Seoul Sintong Clinic in Andong and Yeongju city from October, 2007, to February, 2008. The OLBPDI questionnaire was administered by 5 physical therapists as a cross-sectional study. Student's t-test and analysis of variance (ANOVA/Tukey and Scheffe) were used to analyze OLBPDI score differences. We also used nonparametric statistic analysis (Wilcoxon rank sum test, Median test). Pearson correlation analysis (Spearman correlation analysis) was used to analyze the relationship between OLBPDI and the visual analogue scale (VAS). Multiple regression analysis was performed to determine the effects of independent variables on pain scores as defined by the OLBPDI. Results: The average patient age was 37.1 years (range: 18$\sim$78 years old), and time from onset was 21.7 months (1$\sim$180). OLBPD and VAS scores were 12.70 (3.0$\sim$28.0) and 5.14 (1$\sim$8), respectively. OLBPDI scores were 14.4 in patients taking medicine and 11.57 in those who did not. There was a statistically significant relationship between OLBPDI and VAS (r=0.54, p=0.0001; r=0.55, p=0.0001 by Spearman coefficient). Gender ($\beta$=6.14, p=0.0124), age ($\beta$=-2.01, p=0.0324), weight ($\beta$=0.31, p=0.0222), time from onset ($\beta$=1.54, p=0.0044), and VAS score ($\beta$=1.59, p=0.0004) were significantly associated with OLBPD by multiple regression analysis. Conclusion: Variables associated with OLBPD were gender, age, weight, time from onset, and VAS score. Collecting information on the pain index using OLBPDI was acceptable to patients with low back pain. Further research should explore the pain index by using larger sample sizes and longer follow-up periods.

• Smart Structures and Systems
• /
• 제18권5호
• /
• pp.1029-1062
• /
• 2016

In this research, the nonlinear free vibration analysis of boron-nitride micro ribbon (BNMR) on the Pasternak elastic foundation under electrical, mechanical and thermal loadings using modified strain gradient theory (MSGT) is studied. Employing the von $K{\acute{a}}rm{\acute{a}}n$ nonlinear geometry theory, the nonlinear equations of motion for the graphene micro ribbon (GMR) using Euler-Bernoulli beam model with considering attached mass and size effects based on Hamilton's principle is obtained. These equations are converted into the nonlinear ordinary differential equations by elimination of the time variable using Kantorovich time-averaging method. To determine nonlinear frequency of GMR under various boundary conditions, and considering mass effect, differential quadrature element method (DQEM) is used. Based on modified strain MSGT, the results of the current model are compared with the obtained results by classical and modified couple stress theories (CT and MCST). Furthermore, the effect of various parameters such as material length scale parameter, attached mass, temperature change, piezoelectric coefficient, two parameters of elastic foundations on the natural frequencies of BNMR is investigated. The results show that for all boundary conditions, by increasing the mass intensity in a fixed position, the linear and nonlinear natural frequency of the GMR reduces. In addition, with increasing of material length scale parameter, the frequency ratio decreases. This results can be used to design and control nano/micro devices and nano electronics to avoid resonance phenomenon.

• 천문학회보
• /
• 제43권1호
• /
• pp.53.1-53.1
• /
• 2018

During a major solar eruption, the erupting plasma is possibly out of the equilibrium ionization state because of its rapid heating or cooling. The non-equilibrium ionization process is important in a rapidly evolving system where the thermodynamical time scale is shorter than the ionization or recombination time scales. We investigate the effects of non-equilibrium ionization on EUV and X-ray observations by the Atmospheric Imaging Assembly (AIA) on board Solar Dynamic Observatory and X-ray Telescope (XRT) on board Hinode. For the investigation, first, we find the emissivities for all the lines of ions of elements using CHIANTI 8.07, and then we find the temperature responses multiplying the emissivities by the effective area for each AIA and XRT passband. Second, we obtain the ion fractions using a time-dependent ionization model (Shen et al. 2015), which uses an eigenvalue method, for all the lines of ion, as a function of temperature, and a characteristic time scale, $n_et$, where $n_e$ and t are density and time, respectively. Lastly, the ion fractions are multiplied to the temperature response for each passband, which results in a 2D grid for each combination of temperature and the characteristic time scale. This is the set of passband responses for plasma that is rapidly ionized in a current sheet or a shock. We investigate an observed event which has a relatively large uncertainty in an analysis using a differential emission measure method assuming equilibrium ionization state. We verify whether the observed coronal plasmas are in non-equilibrium or equilibrium ionization state using the passband responses.

• 산업경영시스템학회지
• /
• 제18권34호
• /
• pp.139-146
• /
• 1995

This study is concerned with cost analysis in periodic maintenance policy. Generally periodic maintenance policy in which item is repaired periodic interval times. And in the article minimal repair is considered. Minimal repair means that if a unit fails, unit is instantaneously restored to same hazard rate curve as before failure. In the paper periodic maintenance policy with minimal repair is as follows; Operating unit is periodically replaced in periodic maintenance time, if a failure occurs between minimal repair and periodic maintenance time, unit is replaced by a spate until the periodic time comes. Also unit undergoes minimal repair at failures in minimal-repair-for-failure interval. Then total expected cost per unit time is calculated according to maintenance period and scale parameter of failure distribution. Total cost factors ate included operating, fixed, minimal repair, periodic maintenance and replacement cost Numerical example is shown in which failure time of system has erlang distribution.

• 산업경영시스템학회지
• /
• 제18권36호
• /
• pp.287-295
• /
• 1995

This paper is concerned with cost analysis model in periodic maintenance policy. Generally periodic maintenance policy in which item is repaired periodic interval times. And in the article minimal repair is considered. Mimimal repair means that if a unit fails, unit is instantaneously restored to same hazard rate curve as before failure. In the paper periodic maintenance policy with minimal repair is as follows; Operating unit is periodically replaced in periodic maintenance time, if a failure occurs between minimal repair and periodic maintenance time, unit is replaced by a new item until tile periodic maintenance time comes. Also unit undergoes minimal repair at failures in minimal-repair-for-failure interval. Then total expected cost per unit time is calculated according to scale parameter of failure distribution. Maintenance cost factors are included operating, fixed, minimal repair, periodic maintenance and new item replacement cost. Numerical example is shown in which failure time of system has weibull distribution.

• 한국생활과학회지
• /
• 제16권6호
• /
• pp.1107-1118
• /
• 2007

This study explored the consistency of bullying, victimization and aggressive victimization, the relationships between bullying, victimization and aggressive victimization and overt/relational aggression, and the relationships between bullying groups and overt/relational aggression with gender. The subjects were 4th grade children and 2 years later they were contacted again. Instruments were the Bully-Behavior Scale, the Peer-Victimization Scale and the Peer Nomination Instrument. Bullying, victimization and aggressive victimization were decreased while there were consistencies in overt and relational aggression from 4th to 6th grade. In the correlation analysis, male victims at Time 1 were negatively related to overt and relational aggression at both Time 1 and Time 2. Female bullies were positively related to relational aggression at both Time 1 and Time 2. In the cross-sectional relations of overt aggression with bullying groups, there was a gender difference. In the relational aggression with bullying groups, only bullying groups had a significant difference. In the longitudinal relations of overt aggression with bullying groups, only gender had a significant difference. Males appeared to be more overtly aggressive than females. In the relational aggression, bullying groups, gender, and the interaction between bullying groups and gender had significant differences. Female bullies were more likely to be relationally aggressive than other groups.

• Journal of Mechanical Science and Technology
• /
• 제20권11호
• /
• pp.1961-1971
• /
• 2006

A soft recovery system (SRS) is a device that stops a high speed projectile without damaging the projectile. The SRS is necessary to verify the shock resistant requirements of microelectronics and electro-optic sensors in smart munitions, where the projectiles experience over 20,000 g acceleration inside the barrel. In this study, a computer code for the performance evaluation of a SRS based on ballistic compression decelerator concept has been developed. It consists of a time accurate compressible one-dimensional Euler code with use of deforming grid and a projectile motion analysis code. The Euler code employs Roe's approximate Riemann solver with a total variation diminishing (TVD) method. A fully implicit dual time stepping method is used to advance the solution in time. In addition, the geometric conservation law (GCL) is applied to predict the solutions accurately on the deforming mesh. The equation of motion for the projectile is solved with the four-stage Runge-Kutta time integration method. A small scale SRS to catch a 20 mm bullet fired at 500 m/s within 1,600 g-limit has been designed with the proposed method.