• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.72.1-72.1
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• 2010

Gas materials in the inner Galactic disk continuously migrate toward the Galactic center (GC) due to interactions with the bar potential, magnetic fields, stars, and other gaseous materials. In case of the Milky Way, those in forms of molecules appear to accumulate around 200 pc from the center (the central molecular zone, CMZ) to form stars there and further inside. The bar potential in the GC is thought to be responsible for such acculmulation of molecules and subsequent star formation, which is believed to have been continous throughout the lifetime of the Galaxy. We present 3-D hydrodynamic simulations of the CMZ that consider self-gravity, radiative cooling, and supernova feedback, and discuss the efficiency and role of the star formation in that region. We find that the gas accumulated in the CMZ by a bar potential of the inner bulge effectively turns into stars, supporting the idea that the stellar cusp inside the central 200 pc is a result of the sustained star formation in the CMZ. The obtained star formation rate in the CMZ, 0.03-0.1 Msun, is consistent with the recent estimate based on the mid-infrared observations by Yusef-Zadeh et al. We discuss the secular evolution of nuclear bulges in general, based on our results.

• Research in Community and Public Health Nursing
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• v.26 no.3
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• pp.230-237
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• 2015

Purpose: This study aimed to assess the prevalence of asthma, allergic rhinitis, and atopic dermatitis in elementary school students according to the body mass index. Methods: This study was conducted as cross-sectional descriptive research using a structured questionnaire. Data were collected from 6,398 students at 15 elementary schools located in Y City in Korea. The cross-sectional survey used the Korean version of International Study of Asthma and Allergies in Childhood questionnaire. Logistic regression analysis was performed to estimate the odds ratios of body mass index. Results: The symptom prevalence of asthma, allergic rhinitis, and atopic dermatitis in the last 12 months was 12.4%, 49.5%, and 24.5%, respectively. The symptom prevalence of asthma was significantly higher in the obesity group. The number of those without any asthma symptom in lifetime was significantly smaller in the overweight (OR=0.70, p=.004) and obesity (OR=0.57, p=.005) groups than in the healthy weight group. Conclusion: These results suggest that asthma, allergic rhinitis, and atopic dermatitis prevention programs for elementary school students should include weight control intervention.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.1
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• pp.303-306
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• 2015

Purpose: This study was conducted to determine risk of developing of breast cancer among Turkish women. Materials and Methods: Using a descriptive and cross-sectional approach, data were collected from 231 women. Breast cancer risk was calculated using the National Cancer Institute's on-line verson of called as the Breast Cancer Risk Assessment Tool or the Gail Risk Assesment Tool. Results: The average age of women was $45.0{\pm}8.06$ years. It was revealed that 6.1% of participants reported having first degree relatives who had had breast cancer, with only four women having more than one first-degree relative affected (1.7%). The mean five-year breast cancer risk for all women was $0.88{\pm}0.91%$, and 7.4% of women had a five-year breast cancer risk >1.66% in this study. Mean lifetime breast cancer risk up to age 90 years was $9.3{\pm}5.2%$. Conclusions: The breast cancer risk assessment tool can help in the clinical management of patient seeking advice concerning screening and prevention. Healthcare providers in Turkey can use this approach to estimate an individual's probability of developing breast cancer.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.2
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• pp.131-137
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• 2016

In reliability analysis, it is quite common for the failure of any individual or item to be attributable to more than one cause. Moreover, observed data are often censored. Recently, progressive hybrid censoring schemes have become quite popular in life-testing problems and reliability analysis. However, a limitation of the progressive hybrid censoring scheme is that it cannot be applied when few failures occur before time T. Therefore, generalized progressive hybrid censoring schemes have been introduced. In this article, we derive the likelihood inference of the unknown parameters under the assumptions that the lifetime distributions of different causes are independent and exponentially distributed. We obtain the maximum likelihood estimators of the unknown parameters in exact forms. Asymptotic confidence intervals are also proposed. Bayes estimates and credible intervals of the unknown parameters are obtained under the assumption of gamma priors on the unknown parameters. Different methods are compared using Monte Carlo simulations. One real data set is analyzed for illustrative purposes.

• Asia-Pacific Journal of Business
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• v.2 no.1
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• pp.23-48
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• 2011

Generally, higher brand equity ends up with higher market share and higher profitability. However, superior brand equity does not guarantee the success in the market. That is, consumer choice is closely related to brand equity but we need more than brand equity to explain this complex phenomenon. We adopt the customer equity concepts: value equity, brand equity, and retention equity. By incorporating value equity and retention equity into customer equity, it is possible to avoid the problems of using the brand equity only. In the paper, we apply this customer equity concepts to cellular phone and investigate the effects of antecedent variables such as exposure, knowledge, positive experience and negative experience on the components of customer equity. In addition, as surrogate measure of customer lifetime value, the weighted measure of purchase intention, consideration set inclusion, and next purchase is used as dependent variable. We estimate the effects of components of customer equity at the brand level and aggregate level using SURE model. Estimation results show that Apple has currently low market share but has high future potentials and Korean firms have currently high market share but has rather low future potentials.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.3
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• pp.17-25
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• 2014

The purpose of this paper is to present a method to estimate the storage life of propellant bag for degradation of breaking load with storage time by using gamma process model. The nitrogen compound generated by natural decomposition of propellants degrades the breaking load of propellant bag with time. The statistical distributions of condition and lifetime with time were shown from the results of accelerated life test of propellant bag cloth at $80^{\circ}C$. It was found that the use of median for life was highly appropriate and the $B_1$ or $B_5$ life should be selectively applied to the quality assurance policy.

• Nuclear Engineering and Technology
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• v.50 no.1
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• pp.182-189
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• 2018

A neutron generation system was developed to induce fissile fission in a lead slowing down spectrometer (LSDS) system. The source neutron is one of the key factors for LSDS system work. The LSDS was developed to quantify the isotopic contents of fissile materials in spent nuclear fuel and recycled fuel. The source neutron is produced at a multilayered target by the (e,${\gamma}$)(${\gamma}$,n) reaction and slowed down at the lead medium. Activation analysis of the target materials is necessary to estimate the lifetime, durability, and safety of the target system. The CINDER90 code was used for the activation analysis, and it can involve three-dimensional geometry, position dependent neutron flux, and multigroup cross-section libraries. Several sensitivity calculations for a metal target with different geometries, materials, and coolants were done to achieve a high neutron generation rate and a low activation characteristic. Based on the results of the activation analysis, tantalum was chosen as a target material due to its better activation characteristics, and helium gas was suggested as a coolant. In addition, activation in a lead medium was performed. After a distance of 55 cm from the lead surface to the neutron incidence, the neutron intensity dramatically decreased; this result indicates very low activation.

• Journal of the Korea Society of Computer and Information
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• v.21 no.8
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• pp.95-103
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• 2016

Food habit forming the basis for a lifetime of food and nutrient intake is established in early childhood and has an effect to the child's growth, sociality, and obesity. A variety of nutrition screening tools exists for assessing the health and nutrition status of children such as the Growth Curve, for determining if growth is appropriate. Body mass index(BMI) as a more reliable index of overweight to prevent childhood obesity, and Nutrition Quotient(NQ) and eating behaviors questionnaire for young children and parents to estimate their nutrient intake adequate or not. Such tools are mainly used by health practitioners, such as doctor and dietitian to provide nutrition intervention services to children at risk, especially and are not easy to use for general parents, who need assessment at any time and at any place. We propose Growth Assistance System for infants and children, which is possible to assess their physical condition, nutritional status, and eating behavior integrated. To be convenient and portable, it is implemented over the smartphone as an application. The system offers the growth charts, the BMI curves, NQ and eating behavior questionnaire to take a monitoring and the functionalities operate well. We hereby expect this system support the normal growth and development of infants and young children. And also support for the health practitioner (dietitians and nutritionists) to take a role in providing nutrition counseling and education to children needing nutrition services.

• Journal of the Korean Data and Information Science Society
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• v.26 no.6
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• pp.1573-1582
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• 2015

In lifetime data analysis, it is generally known that the lifetimes of test items may not be recorded exactly. There are also situations wherein the withdrawal of items prior to failure is prearranged in order to decrease the time or cost associated with experience. Moreover, it is generally known that more than one cause or risk factor may be present at the same time. Therefore, analysis of censored competing risks data are needed. In this article, we derive the Bayes estimators for the entropy function under the exponential distribution with an unknown scale parameter based on multiply Type II censored competing risks data. The Bayes estimators of entropy function for the exponential distribution with multiply Type II censored competing risks data under the squared error loss function (SELF), precautionary loss function (PLF) and DeGroot loss function (DLF) are provided. Lindley's approximate method is used to compute these estimators.We compare the proposed Bayes estimators in the sense of the mean squared error (MSE) for various multiply Type II censored competing risks data. Finally, a real data set has been analyzed for illustrative purposes.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.6
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• pp.982-989
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• 2010

This paper shows accuracy comparison results of reliability estimation methods for one-shot systems such as ammunitions. Quantal-response data, following a binomial distribution at each sampling time, characterizes lifetimes of one-shot systems. Various quantal-response data of different sample sizes are simulated using lifetime data randomly sampled from assumed weibull distributions with different shape parameters but the identical scale parameter in this paper. Then, reliability estimation methods in open literature are applied to the simulated quantal-response data to estimate true reliability over time. Rankings in estimation accuracy for different sample sizes are determined using t-test of SSE. Furthermore, MSE at each time, including both bias and variance of estimated reliability metrics for each method are analyzed to investigate how much both bias and variance contribute the SSE. From the MSE analysis, MSE provides reliability estimation trend for each method. Parametric estimation method provides more accurate reliability estimation results than the other methods for most of sample sizes.