• Communications for Statistical Applications and Methods
• /
• 제27권1호
• /
• pp.141-148
• /
• 2020

We consider estimating the proportion of true null hypotheses in multiple testing problems. A traditional multiple testing rate, family-wise error rate is too conservative and old to control type I error in multiple testing setups; however, false discovery rate (FDR) has received significant attention in many research areas such as GWAS data, FMRI data, and signal processing. Identify differentially expressed genes in microarray studies involves estimating the proportion of true null hypotheses in FDR procedures. However, we need to account for unknown dependence structures among genes in microarray data in order to estimate the proportion of true null hypothesis since the genuine dependence structure of microarray data is unknown. We compare various procedures in simulation data and real microarray data. We consider a hidden Markov model for simulated data with dependency. Cai procedure (2007) and a sliding linear model procedure (2011) have a relatively smaller bias and standard errors, being more proper for estimating the proportion of true null hypotheses in simulated data under various setups. Real data analysis shows that 5 estimation procedures among 9 procedures have almost similar values of the estimated proportion of true null hypotheses in microarray data.

• 대한기계학회논문집B
• /
• 제33권4호
• /
• pp.255-263
• /
• 2009

The most concerning issue of these days is the energy crisis caused by increasing threat of dependence on imported oil and volatile market trend. Under these circumstances, the PHEV(plug-in hybrid electric vehicle) is drawing attention for the next generation's car which could give a chance to decrease the dependence on imported oil and reduce the environmental impact of vehicle. The fueling cost of PHEV, one of the core factor of decision about buying car, should be calculated in the circumstances of Korea to make sure that PHEV has competitive power in real market. The fuel cost saving of PHEV versus CV(conventional vehicle) is simulated and discussed in the condition of increasing gasoline cost, electricity rate, and city-gas rate. In conclusion, the PHEV60-FS shows the best economic feasibility when gasoline price goes up. The PHEV20 has the most stable economic feasibility as electricity rate increases. The fuel cell cogeneration system for RPG could be an alternative for charger of PHEV in the near future.

• Progress in Superconductivity
• /
• 제6권1호
• /
• pp.13-18
• /
• 2004

High-.ate in-situ$ YBa_2$Cu$Cu_3$$O_{7-x}$ (YBCO) film growth was demonstrated by means of the electron beam co-evaporation. Even though our oxygen pressure is low, ∼$5 ${\times}$10^{-5}$ Torr, we can synthesize as-grown superconducting YBCO films at a deposition rate of around 10 nm/s. Relatively high temperatures of around 90$0^{\circ}C$ was necessary in this process so far, and it suggests that this temperature at a given oxygen activity allows a Ba-Cu-O liquid formation along with an YBCO epitaxy. Local critical current density shows a clear correlation with local resistivity. Homogeneous transport properties with a large critical current density ($4 ∼ 5 MA/\textrm{cm}^2$ at 77K, 0T) are observed in top faulted region while it is found that the bottom part carries little supercurrent with a large local resistivity. Therefore, it is possible that thickness dependence of critical current density is closely related with a topological variation of good superconducting paths and/or grains in the film bodies. The information derived from it may be useful in the characterization and optimization of superconducting films for electrical power and other applications.

• Journal of Mechanical Science and Technology
• /
• 제17권1호
• /
• pp.57-63
• /
• 2003

An eigenvalue design sensitivity formulation of a general nonsymmetric-matrix rotor-bearing system is devised. using the DDM (direct differential method). Then, investigations on the design sensitivities of critical speeds are carried out for an APU turbogenerator with a spline shaft connection. Results show that the dependence of the rate of change of the critical speed on the stiffness changes of bearing models of spline shaft connection points is negligible, and thereby their modeling uncertainty does not present any problem. And the passing critical speeds up to the 4th critical speed are not sensitive to the design stiffness coefficients of four main bearings. Further, the dependence of the rate of change of the critical speed on the shaft-element length changes shows quantitatively that the spline shaft has some limited influence on the 4th critical speed but no influence on the 1st to 3rd critical speeds. With no adverse effect from the spline shaft, the APU system achieves a critical speed separation margin of more than 40% at a rated speed of 60,000 rpm.

• Bulletin of the Korean Chemical Society
• /
• 제34권8호
• /
• pp.2473-2479
• /
• 2013

The kinetics of the radical-polar molecule reaction $CH_3+HBr{\rightarrow}CH_4+Br$ has been studied at temperatures between 150 and 1000 K using classical dynamics procedures. Potential energy surfaces constructed using analytical forms of inter- and intramolecular interaction energies show a shallow well and barrier in the entrance channel, which affect the collision dynamics at low temperatures. Different collision models are used to distinguish the reaction occurring at low- and high-temperature regions. The reaction proceeds rapidly via a complex-mode mechanism below room temperature showing strong negative temperature dependence, where the effects of molecular attraction, H-atom tunneling and recrossing of collision complexes are found to be important. The temperature dependence of the rate constant between 400 and 1000 K is positive, the values increasing in accordance with the increase of the mean speed of collision. The rate constant varies from $7.6{\times}10^{-12}$ at 150 K to $3.7{\times}10^{-12}$ at 1000 K via a minimum value of $2.5{\times}10^{-12}\;cm^3\;molecule^{-1}\;s^{-1}$ at 400 K.

• 한국초전도ㆍ저온공학회논문지
• /
• 제25권3호
• /
• pp.28-33
• /
• 2023

Magnetic relaxation properties of pure MgB₂ powder samples and diluted water-treated MgB₂ powder samples were investigated. The magnetic field H-dependence, m(H), and the time t-dependence, m(t), of the magnetic moment m were measured and analyzed using the PPMS-VSM magnetometer equipment, respectively. The m(t) reduction rates of pure MgB₂ powder samples and diluted water-treated MgB₂ powder samples decreased to about 0.7 ~ 1.8% and 0.6 ~ 1.0% for about 7200 s, respectively, at temperature T = 15 K. The magnetic relaxation properties of the two types of MgB₂ powders were analyzed by calculating the magnetic relaxation rate S = -dln(M_irr)/dln(t) values according to Anderson-Kim theory. The magnetic relaxation ratio S values of the two types of MgB₂ powder samples were almost similar. As a result of the quantum creep effect, the constant magnetic relaxation rate S characteristic was confirmed at a temperature range of T = 10 K or less.

• Tuberculosis and Respiratory Diseases
• /
• 제85권4호
• /
• pp.349-357
• /
• 2022

Background: The most consistently identified mortality determinants for the new coronavirus 2019 (COVID-19) infection are aging, male sex, cardiovascular/respiratory diseases, and cancer. They were determined from heterogeneous cohorts that included patients with different disease severity and previous conditions. The main goal of this study was to determine if activities of daily living (ADL) dependence measured by Barthel's index could be a predictor for COVID-19 mortality. Methods: A prospective cohort study was performed with a consecutive sample of 340 COVID-19 patients representing patients from all over the northern region of Portugal from October 2020 to March 2021. Mortality risk factors were determined after controlling for demographics, ADL dependence, admission time, comorbidities, clinical manifestations, and delay-time for diagnosis. Central tendency measures were used to analyze continuous variables and absolute numbers (proportions) for categorical variables. For univariable analysis, we used t test, chi-square test, or Fisher exact test as appropriate (α=0.05). Multivariable analysis was performed using logistic regression. IBM SPSS version 27 statistical software was used for data analysis. Results: The cohort included 340 patients (55.3% females) with a mean age of 80.6±11.0 years. The mortality rate was 19.7%. Univariate analysis revealed that aging, ADL dependence, pneumonia, and dementia were associated with mortality and that dyslipidemia and obesity were associated with survival. In multivariable analysis, dyslipidemia (odds ratio [OR], 0.35; 95% confidence interval [CI], 0.17-0.71) was independently associated with survival. Age ≥86 years (pooled OR, 2.239; 95% CI, 1.100-4.559), pneumonia (pooled OR, 3.00; 95% CI, 1.362-6.606), and ADL dependence (pooled OR, 6.296; 95% CI, 1.795-22.088) were significantly related to mortality (receiver operating characteristic area under the curve, 82.1%; p<0.001). Conclusion: ADL dependence, aging, and pneumonia are three main predictors for COVID-19 mortality in an elderly population.

• 한국정밀공학회지
• /
• 제9권1호
• /
• pp.106-117
• /
• 1992

In this study, the propagation behaviour and the closure phenomena of physically small surface cracks were investigated by the techinque of the Kikukawa-unloading elastic compliance method using a back face strain gage. The surface cracks initiated and propagated from notched specimens under constant amplitude bending load. The crack shape (aspect ratio) with approximately semi-circular at the early stage was changed to semi-elliptical as the cracks grew larger. The crack depth (a) could be expressed uniquenly by the crack length (c). The dependence of the crack propagation rate on the stress ratio R was strongly related in the lower ${\Delta}K$ range. The deceleration of the surface crack propagation rate was prominent in lower R during the crack length was small. When the propagation rate was rearranged with the effective stress intensity factor range ${\Delta}$K_{eff} the dependence of the crack propagation rate on the stress ratio R was found to be diminshed. These were caused by the crack closure phenomena that was most prominent at the lower propagation rate. The mechanism of crack closure phenomena was dominated by the plasticity-induced mechanism.

• 한국보건간호학회지
• /
• 제13권1호
• /
• pp.97-113
• /
• 1999

To investigate the actual condition of the adult-smoking in Chinan County. I used self-reporting questionnaires among 923 residents living in nine districts selected at random among the sites of eleven eup-myons from December 28. 1998 to January 6. 1999. collected data and analyized using SPSS. The smoking rate of adults in Chinan County was $36.9\%$. There was a significant difference in smoking rate according to the age. gender, education and job among general characteristics. The smoking rate in group of above 40s was about $40\%$ and that of the male took $55.5\%$ which was higher than that of female and the smoking rate of the people having high-school education was the highest$(46.2\%)$. With regard to the career. the smoking rate of the farmers ranked first$(46.1\%)$. Therefore anti-smoking business for smokers should be focused on above 40 years old, males. people having high school education and farmers. As the result of the survey of smoking habits of 340 people who smoke currently, the average smoking begining age was 21.8 and $81.5\%$ among them was between 16-25 years old. $4.4\%$ was under 15. during around the elementary school. Most motives to smoke were as followed; curiosity or taste$(33.6\%)$, relief of stress $(31.2\%)$, peer presure$(26.5\%)$ And considering the amount of the cigarette which is smoked per day, the case which is less than a pack of cigarettes was highest as $75.5\%$ and the people who smoke over one pack of cigarettes took $24.5\%$. As for the kind of tobacco which is smoked, how to smoke and the desire for the smoking, most case was toxin was moderate$(47.8\%)$ or mild$(46.9\%)$. shallowly$(49.0\%)$ or deeply$(46.3\%)$ and under stress$(33.4\%)$. after meals$(27.8\%)$, during drink$(15.7\%)$ and so on. The highest point marked among the factors of smoking motives was 'the reduce of negative emotion' $(3.27\pm1.00)$. followed by 'uncomfortable habits' $(2.87\pm1.02)$, 'addiction' $(2.84\pm1.06)$. 'habit' $(2.74\pm1.12)$. 'pleasure' $(2.70\pm1.04)$. 'stimulus' $(2.59\pm.90)$, 'sensation-exercise satisfaction' $(2.42\pm.97)$. Smokers smoke to reduce the negative emotions when angry in most common case. depressed. anxious. uncomfortable. lone. ashamed or embarrased. and intend to solve the certain problem. etc. Other motives are uncomfortable habit. addiction. habit. pleasure and the pursuit of stimulus. The level of nicotine dependence of adults m Chinan County was 10.57 which amount to 'high' wholly. As the resulf of the level of nicotine dependence score. the people who are low in the level of nicotine was $33.5\%$. the people who are high was $48.2\%$. very high was $18.4\%$. The approach for anti-smoking for smokers should be conducted differently according to the level of the nicotine. For the people who are in low level of nicotin dependence the prohibition of the smoking should be guided through the approach to foster strong will. for those who are in 'high' by acquiring proper method for the prohibition of smoking. and for those who are 'very high' the anti-smoking should be induced by providing proper program because of the possibility of the suffer from abstinence syndrome. The difference of the level of nicotine with the general characteristics of the objects had not statistically significant difference. The difference of the level of nicotine dependence accompanied by smoking habit had statistically significant difference according to the amount of smoke, the kind of tobacos. smoke inhale habit. In other words, the group of heavy smokers had higher level of the nicotine dependence than that of the light smokers relatively and the group which smoke strong taboaco has higher level of nicotine than that of which smoke mild or moderate. And the group of smokers who smoke deeply has higher level of nicotine than that who smoke shallowly or nonswallow. Aa a result of the analysis of the correlation between smoking motive factors and the level of nicotine, there was the indication that people who smoke for the decrease of the negative emotion. habit, pleasure. stimulus. sensation-exercise satisfaction had high level of the nicotine dependence. As the result of the anti-smoking will of smokers. $65.0\%$ of them had prohibition of smoking will. $29.3\%$ had no will to quit smoke. The most important reason for anti-smoking was health. $67.9\%$ had experience to try to quit smoke and the biggest reason to fail to quit smoking was the lack of the will power to keep anti-smoking. $52.8\%$ of them were advised to stop smoking from their spouses or children. only $2.8\%$ were by medical. The people who have the opinion to need anti-smoking education were $69.6\%$. Therefore when the business for the hygine of the mouth for adult is set. it should be centered on the people who have intention of prohibition of the smoking and help to quit smoking by way of other affirmative counter-program not smoking under stress.

• 재무관리연구
• /
• 제23권1호
• /
• pp.193-225
• /
• 2006

본 연구는 EVT-Copula모형을 이용하여 아시아지역 8개국 외환시장 간 극단적 사건의 동조화 정도를 측정하였다. 본 연구의 분석대상은 대만, 말레이시아, 싱가포르, 인도네시아, 일본, 태국, 필리핀, 한국의 일별 현물환율이며 분석기간은 1997년 1월 1일부터 2005년 4월 13일까지이다. 주요 연구결과를 요약하면 다음과 같다. 첫째, AIC기준에 따라 의존구조를 모형화 하는데 있어 Gumbel Copula가 Galambos Copula에 비해 더 적합한 모형으로 나타났다. 둘째, 동남아시아 외환위기국 간의 극단적 동조성은 외환위기 기간에 비하여 그 이후에 낮아진 것으로 확인되었다. 넷째, 아시아 국가들은 동남아시아 외환시장의 거점인 싱가포르와 상대적으로 높은 극단적 의존성을 가지는 것이 확인되었다. 넷째, 인도네시아, 말레이시아, 태국, 필리핀 간 아시아 외환위기 동안의 꼬리의존성이 표본전체기간과 외환위기 이후기간에 비해 높게 나타났다. 특히 말레이시아의 경우 외환위기 기간에 필리핀, 인도네시아, 태국과의 꼬리의존성이 현저히 높았다. 지역적으로 인접한 국가들에서 단기간에 꼬리의존성이 급증하는 사실은 아시아 외환위기에 있어 시장간 극단적 의존성이 금융위기의 전파에 중요한 역할을 했다는 것을 의미한다. 다섯 째, 외환위기 동안 한국과 인도네시아, 말레이시아, 태국, 필리핀간의 극단적 의존관계는 증가하지 않았음으로 한국의 금융위기가 외부 요인으로 인한 것이 아니라는 주장을 지지하였다.