• Geomechanics and Engineering
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• 제36권6호
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• pp.601-618
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• 2024

The joint probability distribution of uncertain geomechanical parameters of geotechnical strata is a crucial aspect in constructing the reliability functional function for roof structures. However, due to the limited number of on-site exploration and test data samples, it is challenging to conduct a scientifically reliable analysis of roof geotechnical strata. This study proposes a Copula method based on small sample exploration and test data to construct the intensity characteristics of roof geotechnical strata. Firstly, the theory of multidimensional copula is systematically introduced, especially the construction of four-dimensional Gaussian copula. Secondly, data from measurements of 176 groups of geomechanical parameters of roof geotechnical strata in 31 coal mines in China are collected. The goodness of fit and simulation error of the four-dimensional Gaussian Copula constructed using the Pearson method, Kendall method, and Spearman methods are analyzed. Finally, the fitting effects of positive and negative correlation coefficients under different copula functions are discussed respectively. The results demonstrate that the established multidimensional Gaussian Copula joint distribution model can scientifically represent the uncertainty of geomechanical parameters in roof geotechnical strata. It provides an important theoretical basis for the study of reliability functional functions for roof structures. Different construction methods for multidimensional Gaussian Copula yield varying simulation effects. The Kendall method exhibits the best fit in constructing correlations of geotechnical parameters. For the bivariate Copula fitting ability of uncertain parameters in roof geotechnical strata, when the correlation is strong, Gaussian Copula demonstrates the best fit, and other Copula functions also show remarkable fitting ability in the region of fixed correlation parameters. The research results can offer valuable reference for the stability analysis of roof geotechnical engineering.

• 전기학회논문지P
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• 제63권3호
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• pp.183-188
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• 2014

Power conversion systems used in large gas turbine power plant can be divided into two main part. Because of the initial start-up characteristic of the gas turbine combustor, the gas turbine must be accelerated by starting device(LCI : Load Commutated Inverter) up to 10%~20% of rated speed to ignite it. In addition, the ECS(Excitation Control system) is used to control the rotor field current and reactive power in grid-connected synchronous generator. These two large power conversion systems are located in the same space(container) because of coordination control. Recently, many manufactures develop high speed controller based on function block available in the LCI and ECS with the newest power semiconductor. We also developed high speed controller based on function block to be using these two system and it meets the international standard IEC61131 as using real-time OS(VxWorks) and ISaGRAF. In order to install easily these systems at power plant, main controller, special module and IO module are used with high speed communication line other than electric wire line. Before initial product is installed on the site, prototype is produced and tests are conducted for it. The performance results of Integrated controller and application program(SFC, ECS) were described in this paper. The test results will be considered as the important resources for the application in future.

• 한국임상수의학회지
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• 제32권4호
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• pp.324-329
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• 2015

The primary aim of this study was to investigate biosecurity practices in pig farms and to determine the major risk factors associated with PCV2 infection for a sampled swine population in Korea. To this end, we analyzed data from a cross-sectional study of 296 farrow-to-finish farms, which was conducted between March and September 2014 to explore the prevalence of swine disease at farm level. Face-to-face interviews by on-site visit of trained veterinarians were conducted with the farm owners or managers using a standardized questionnaires with information about basic demographical data and management practices. Farms were classified as negative or positive through the use of infection profiles that combined data on serological testing including PCR antigen test result, antibody titer and sero-conversion pattern at each age category taking into account vaccination status. Data were analyzed using multivariate ordinal logistic regression. Results from this study indicated that biosecurity level of the farms was considered not good given low compliance of the biosecurity programs and facilities in the farm: off-site removal of dead stocks (7%), off-site location of storage facility for incoming feeds (12.6%), off-site pick-up location for finishers (19.3%), restrictions on feed supplier vehicles for farm entrance (19.6%), restriction of finisher trucks entering the farm (22.4%), and restriction on manure disposal trucks entering the farm (26.4%). In the final model (n = 255), allowance of finisher truck driver to the pig unit had increased risk of infection (OR = 2.4, 95% CI 1.22-4.67) whereas farms with a sign forbidding the entrance had decreased risk of infection (OR = 0.19, 95% CI 0.10-0.58). Further comprehensive research with larger sample size is required to better understand the multifactorial characteristic that some predisposing risk factors that were not available in this study. To the best knowledge of the authors, this was the first study to use empirical data to report risk factors associated with PCV2 infection in the Korean pig farms. Results from the current study could be used to decide optimal biosecurity measures to reduce the impact of PCV2 infection to farmers and policy makers.

• Asian Pacific Journal of Cancer Prevention
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• 제14권9호
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• pp.5043-5047
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• 2013

Background: This is a part of a larger effort to characterize the effects on socio-economic factors (SEFs) on cancer outcome. Surveillance, Epidemiology and End Result (SEER) bone and joint sarcoma (BJS) data were used to identify potential disparities in cause specific survival (CSS). Materials and Methods: This study analyzed SEFs in conjunction with biologic and treatment factors. Absolute BJS specific risks were calculated and the areas under the receiver operating characteristic (ROC) curve were computed for predictors. Actuarial survival analysis was performed with Kaplan-Meier method. Kolmogorov-Smirnov's 2-sample test was used to for comparing two survival curves. Cox proportional hazard model was used for multivariate analysis. Results: There were 13501 patients diagnosed BJS from 1973 to 2009. The mean follow up time (SD) was 75.6 (90.1) months. Staging was the highest predictive factor of outcome (ROC area of 0.68). SEER stage, histology, primary site and sex were highly significant pre-treatment predictors of CSS. Under multivariate analysis, patients living in low income neighborhoods and rural areas had a 2% and 5% disadvantage in cause specific survival respectively. Conclusions: This study has found 2-5% decrement of CSS of BJS due to SEFs. These data may be used to generate testable hypothesis for future clinical trials to eliminate BJS outcome disparities.

• 경영과정보연구
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• 제21권
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• pp.131-154
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• 2007

The purpose of this study is to understand a information technology acceptance model and to test empirically using field survey. In order to achieve this purpose, first of all, I examined literature reviews about the theory of reasoned action(TRA), the theory of planned behavior(TPB), and the theories of technology acceptance model(TAM). Based on literature reviews, I proposed a technology acceptance model and empirically verified it through using field survey. As a result of, this study was designed to predict and to explain the factors of affecting reuses of a website. The data that were surveyed 193 users of internet were analyzed with SPSS 12.0 and AMOS 4.0. The major results of this study as follows : First, the perceived complexity is influenced by the skill & experience and the quality of system. Second, the quality of system affects the perceived usefulness. Third, the perceived complexity affects the perceived usefulness and the perceived playfulness. Fourth, reuses of a web site are influenced by the perceived usefulness and the perceived playfulness. Finally, the quality of system affects the perceived usefulness and the skill & experience affect the perceived playfulness.

• 한국기계가공학회지
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• 제18권6호
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• pp.9-18
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• 2019

This study derives load characteristics and analyzes the safety of plowshares operating in dry fields. We mounted a three-blade, reversible plow on a 23.7 kW tractor and measured the plow's tractive force as well as the torque from the engine output shaft on the rear axle under various working speeds (L4, M1, M2, M3). We chose a Korean test site of Seomyeon, Chuncheon with sandy soil texture, as determined using the USDA method. We constructed the load spectrum for torque and tractive force using measured data and derived the fatigue life of the plowshare from a stress-cycle (S-N) curve of the plow material. Our results show that the M3 gear maximizes the driving shaft torque loads and, applying the tractive force load spectrum, creates a cumulative damage sum of $4.14{\times}10^{-5}$. Considering sampling time, we estimate a fatigue life of 805 hours while using the M3 gear. When using the other working speeds, however, all of the stress levels fell within the endurance limits and, therefore, our model predicts infinite plowshare lifetimes. For this analysis, we used a yield strength of 1,079 MPa for the plowshare and static safety factors, analyzed using the maximum stress, between 6.83 and 8.63 under each working speed.

• 보건교육건강증진학회지
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• 제21권3호
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• pp.101-116
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• 2004

Korea has the highest traffic accident occurrence rate in the world. It means that we are forced to face a tremendous amount of economic loses and great cost of life. Even though this phenomenon consistently has arose as a public issue every year and many researchers have emphasized the importance of safety education as the fundamental solution, we are still trying to make a long-lasting and effective traffic safety education programs for children and adolescents. The purpose of this study was to test the effectiveness of web-based learning for traffic safety in Korea middle school. For this purpose, the instructive model was constructed based on the ASSURE model and a special web-site of education was developed on behalf of practical use of multi-media learning materials for the traffic safety. The research subject was represented by 259 students from second grade in 2 middle schools located in Seoul Korea. The traffic safety education program using web-site was preceded to the 136 students as a case group for 45 minutes total 3 times. Other 126 students are control group those who did not get with this program. The survey was conducted before and after the education. The results of this study were as follow: 1. The knowledge analysis from the comparison between before and after of the lesson showed case group and control group scored average at 11.25 points and 10.97 points. However, after they attended programs, case group scored 13.57 points and control group scored 10.85 points. The difference from the result of the case group was statistically significant(p<0.001). 2. The attitude analysis from the comparison between before and after of the lesson showed case group and control group scored averages at 29.59 points and 28.21 points. However, after they attended program, case group scored 37.23 points and control group scored 32.71 points. The difference from the result of the case group was statistically significant(p<0.05). 3. Regarding the domain analysis by means of web-based traffic safety education, only the case group had a statistically significant score in the case of knowledge 'safe utilization of bicycle' and 'The Characteristic of Automobile and Safer Mode of Walking for Pedestrian'(p<0.01, p< 0.001), and in the case of attitude 'safe walking and crossing' 'The Characteristic of Automobile and Safer Mode of Walking for Pedestrian'(p<0.01, p<0.001). 4. Web based instruction for traffic safety was effective in terms of improving students' knowledge and attitude for traffic safety.

• 한국대기환경학회지
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• 제27권3호
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• pp.291-302
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• 2011

[ $PM_{10}$ ]measurements were made at two coastal sites, i.e., Taean and Gangneung, for summer to examine the characterization of water-soluble organic carbon (WSOC) and inorganic ionic species, and to investigate their difference between the sites. The fractions of three major inorganic water-soluble components ($NO_3^-$, $SO_4^{2-}$, and $NH_4^+$) at Taean and Gangneung sites were 30.6% (16.2~62.0%) and 25.6% (13.0~52.5%) of the $PM_{10}$, respectively. $SO_4^{2-}$ is the most dominant species of water-soluble ions at both sites, accounting for up to 20.5% (9.1~44.9%) and 16.3% (5.5~34.2%) of their respective PM10 mass concentrations. Using the paired T-test, $PM_{10}$ (p<0.01), $NO_3^-$ (p<0.05), $SO_4^{2-}$ (p<0.01), $NH_4^+$ (p<0.001), and WSOC (p<0.05) concentrations exhibited strong fluctuations on a daily basis between Taean and Gangneung sites. Relationship between the concentrations of $SO_x$ ($SO_4^{2-}+SO_2$) and CO indicates that the slopes of $SO_x$ /CO were 0.007 and 0.019 in the Taean and Gangneung sites, respectively. The smaller $SO_x$/CO slope in the Taean site could be related to the aged air with wet scavenging of $SO_x$ during transport. The correlation between the concentrations of CO and WSOC suggests that WSOC observed in the Gangneung ($R^2$=0.82) be transported from combustion-related sources, while the WSOC at the Taean site could be formed through atmospheric processing of primary volatile organic species during transport.

• 한국지반공학회논문집
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• 제28권9호
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• pp.23-30
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• 2012

본 논문은 토석류 발생사면에서 불포화토의 침투해석을 연계 수행한 사면안정해석 연구결과이다. 2006년 강원도 인제군과 2010년 경기도 양평군에 위치한 2개소의 토석류 발생사면에 대하여 현장조사를 수행하고 붕괴발생부에서 채취한 시료로 tempe pressure cell을 이용한 함수특성곡선과 새로이 개발된 불포화토 직접전단시험기를 사용하여 불포화토의 전단강도 정수를 구하였다. 실험을 통해 획득한 물성과 토석류 발생 당시의 강우자료를 바탕으로 상용프로그램 SEEP/W를 사용하여 불포화토 침투 해석을 실시하고 그 결과와 연동하여 사면안정해석 프로그램 SLOPE/W를 사용하여 사면활동을 분석하였다. 본 연구 결과 집중강우에 의한 불포화토 지반에 강우침투의 영향으로 지하수위의 상승과 포화도의 증가로 사면안전율이 감소하여 사면활동이 발생한 것으로 나타났다. 이러한 연구 방법을 통하여 실제 강우특성을 고려한 불포화토의 사면안정해석을 실시하는 것이 토석류 발생사면의 거동특성 중 특히 발생시점을 확인할 수 있는 합리적인 방법이라 판단된다.

• 전기학회논문지
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• 제64권2호
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• pp.304-309
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• 2015

Applicable range of Photoplethysmography (PPG) becomes wider as a non-invasive physiological measurement technique. However, PPG waveform is easy to be distorted by ambient light or vascular variation from temperature changes. Especially, irregular variation of PPG waveform caused by ambient temperature not only severely distorts the PPG, but also leads miss interpretation in clinical applications. Therefore, the investigation of between temperature and PPG waveform is quite important in using PPG. The purpose of this research is to quantify the PPG waveform characteristic and to investigate the waveform variation following the temperature change on measuring site. To quantify the fluctuation of PPG waveform, we use two techniques; detrended fluctuation analysis (DFA) and AC/DC analysis of PPG. We record PPG under temperature stress, which applied by medical use heat pack ($40^{\circ}C$) and ice pack ($0^{\circ}C$). Ten participants were applied to the experiment, and the result was evaluated to approve the temperature effect with statistical method, Wilcoxon signed rank test. The result shows that the AC component (p<0.05) and perfusion index DFS scale exponent (p<0.01) of PPG have the significance to temperature stress except for a DC component of PPG.