• Journal of the Semiconductor & Display Technology
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• v.10 no.1
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• pp.57-61
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• 2011

To develop high efficiency crystalline solar cells, the rear surface passivation is very important. In this paper, $Al_2O_3$ films deposited by thermal ALD(atomic layer deposition) method were studied for rear surface passivation of crystalline solar cells and their passivation properties were evaluated. After the deposition of $Al_2O_3$ films on p-type Si wafers, the lifetime was increased very much due to the reduction of interface state density and the field effects of the negative fixed charge in the films. Also, optimum annealing condition and effects of SiNx capping layer were investigated. The best lifetime was obtained when the films were annealed at $400^{\circ}C$ for 15min. And the lifetime degradation of the $Al_2O_3$ films with SiNx capping layers was improved compared to those without the capping layers.

• Journal of the Semiconductor & Display Technology
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• v.11 no.2
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• pp.7-11
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• 2012

SiNx films have been wildly used as anti-reflection coatings and passivation for crystalline silicon solar cells. In this study, the SiNx films were deposited by using high frequency (13.56MHz) PECVD and optical & passivation properties were investigated. The RF power was changed in a certain range for the film deposition. Then, the refractive index, etch rate, minority carrier lifetime and cell efficiency were measured to study the properties of the film respectively. The optimal deposition conditions for application to crystalline silicon solar cells were proposed as results of the study. Finally, the best cell efficiency of 16.98% was obtained from the solar cell with the SiNx films deposited by RF power of 550W.

• International Journal of Reliability and Applications
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• v.16 no.2
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• pp.123-133
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• 2015

In this paper, the problem of testing exponentiality against net decreasing variance residual lifetime (NDVRL) classes of life distributions is investigated. For this property a nonparametric test is presented based on kernel method. The test is presented for complete and right censored data. Furthermore, Pitman's asymptotic relative efficiency (PARE) is discussed to assess the performance of the test with respect to other tests. Selected critical values are tabulated. Some numerical simulations on the power estimates are presented for proposed test. Finally, numerical examples are presented for the purpose of illustrating our test.

• Korea journal of population studies
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• v.35 no.1
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• pp.151-179
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• 2012

This study investigates birth cohort and educational differences in the marital and fertility life course using the Hernes model. First, lifetime marriage rates remain high across birth cohorts but men in the youngest birth cohort(1965-74) experience a somewhat significant reduction in ever-marriage rates. Second, this study also finds educational differences in lifetime marriage rates across birth cohorts. The likelihood of being never married is particularly high for poorly educated men in the youngest birth cohort but women show the opposite pattern. Third, quantum changes in the fertility transition are more likely to be the changes in higher-order births, while the changes in first and second births are mainly tempo changes. Fourth, the negative association between education and fertility is significantly larger for higher-order births. Finally, marriage and fertility show the opposite pattern in their association with education. Overall, educational differences in lifetime marriage rates become stronger across birth cohorts but the association between education and higher-order births shows the opposite pattern.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.499-502
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• 2008

한정된 용량의 배터리에 의존하는 무선 Ad-hoc 네트워크(MANET)에서는 에너지 효율을 높이기 위한 다양한 클러스터링 기법과 라우팅 알고리즘이 연구되고 있다. 이러한 무선 Ad-hoc 네트워크에서는 에너지 효율이 높은 클러스터 기반의 라우팅 알고리즘이 많이 사용된다. 그러나 일반적인 클러스터 방식에 따른 라우팅 알고리즘에서는 클러스터 헤드 노드에 부하가 집중되어 에너지 소모가 많은 문제점을 가진다. 이 문제를 보완하기 위해서 클러스터 헤드 노드의 재 선출을 통해 에너지 소모를 분산하는 동적 클러스터링 방식이 사용되고 있다. 그러나 동적 클러스터링 방식 또한 높은 빈도의 클러스터 재형성 과정에서 많은 에너지를 소모하는 문제점이 있다. 즉, 지금까지 연구되어온 알고리즘은 클러스터 구성에 대한 효율적인 알고리즘을 제시하고 있지만 불필요한 에너지 소모를 최소화하는 최적의 헤드 노드 선정 방법과 클러스터 관리를 통하여 에너지 효율을 높일 수 있는 해결책을 제시하지 않았다. 따라서 본 논문에서는 위의 클러스터 문제를 해결하기 위해 TICC(Time Interval Clustering Control) 알고리즘 기법을 제안한다. 제안된 TICC은 각 노드의 에너지 속성 값에 따라 에너지 Level을 분류하고 분류된 에너지 Level에 따라 타이밍을 고려한 클러스터링 및 노드 관리방법이다. 이러한 TICC기법을 적용하여 실험을 하였고 결과적으로 클러스터 전체의 에너지 효율을 향상되고 Lifetime이 증가함을 보였다.

• Korean Journal of Health Education and Promotion
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• v.28 no.2
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• pp.109-123
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• 2011

Objectives: The purpose of the present study was to explore the relationships between views on suicide, death, and life and lifetime suicidal attempts in the Korean context. Methods: Multiple logistic regression model was tested using data from Korean General Social Survey of 2009. We utilized the nationally representative survey data obtained via multistage stratified area probability sampling design from 1,599 respondents aged ${\geq}18$ years. Results: The proportion of lifetime suicidal attempts was 12.1% of entire sample in Korea. Some components of views on suicide and death influenced significantly on lifetime suicidal attempts after adjusting for demographic and health-related factors. The positive view on suicide(OR=0.76, 95% CI: 0.62-0.94), the naturalistic view on afterlife(OR=0.37, 95% CI: 0.67-0.99) and death concern(OR=0.67, 95% CI: 0.55-0.83) were risk factors of lifetime suicidal attempts. In contrast, the social responsibility view on suicide(OR=1.17, 95% CI: 1.00-1.37) and the transcendental view on afterlife(OR=1.25, 95% CI: 1.02-1.54) lowered the risk. Conclusions: Practical implications of the findings were discussed exploring policy evidences to screen high risk groups out and to reframe educational programs for suicide prevention. Strategic health messages need to be developed and transmitted for prevention of suicide.

• Communications for Statistical Applications and Methods
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• v.23 no.4
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• pp.269-285
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• 2016

In this paper, a simple step-stress accelerated life test (ALT) under progressive type-II censoring is considered. Progressive type-II censoring and accelerated life testing are provided to decrease the lifetime of testing and lower test expenses. The cumulative exposure model is assumed when the lifetime of test units follows an extension of the exponential distribution. Maximum likelihood estimates (MLEs) and Bayes estimates (BEs) of the model parameters are also obtained. In addition, a real dataset is analyzed to illustrate the proposed procedures. Approximate, bootstrap and credible confidence intervals (CIs) of the estimators are then derived. Finally, the accuracy of the MLEs and BEs for the model parameters is investigated through simulation studies.

• Journal of the Semiconductor & Display Technology
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• v.13 no.4
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• pp.21-25
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• 2014

The silicon nitride ($SiN_x$) film for surface passivation and anti-reflection coating of crystalline silicon solar cell is very important and it is generally deposited by plasma enhanced chemical vapor deposition (PECVD). PECVD can be divided into low and high frequency method. In this paper, the $SiN_x$ film deposited by low and high frequency PECVD method was studied. First, to optimize the $SiN_x$ film deposited by low frequency PECVD method, the refractive index was measured by varying the process conditions like $SiH_4$, $NH_3$, $N_2$ gas rate, and RF power. When $SiH_4$ gas rate was increased and $NH_3$ gas rate was decreased, the refractive index was increased. The refractive index was also increased with RF power decline. Second, to compare the characteristics of the low and high frequency PECVD $SiN_x$ film, the refractive index was measured by varying $NH_3/SiH_4$ gas ratio and RF power and the minority carrier lifetime of before and after high temperature treatment process was also measured. The refractive index of both low and high frequency PECVD $SiN_x$ film was decreased with increase in $NH_3/SiH_4$ gas ratio and RF power. After high temperature treatment process, the minority carrier lifetime of both low and high frequency PECVD $SiN_x$ film was increased and increased degree was similar. The minority carrier lifetime of low frequency PECVD $SiN_x$ was increased from $11.03{\mu}m$ to $28.24{\mu}m$ and that of high frequency PECVD $SiN_x$ was increased from $11.60{\mu}m$ to $27.10{\mu}m$.

• 한국디지털정책학회:학술대회논문집
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• 2004.11a
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• pp.283-294
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• 2004

Within the rapidly changing environment of global economics, the environment of higher education in the universities & companies, also, has been, encountering various changes. Popularization on higher education related to lifetime education system, putting emphasis on the productivity of education services and the acquisition of competitiveness through the market of open education, the breakdown of the ivory tower and the Multiversitization of universities & companies, importance of obtaining information in the universities & companies, and cooperation between domestic and oversea universities, industry and educational system must be acquired. Therefore, in order to adequately cope with these kinds of rapid changes in the education environment, operating E-Learning Education & company by utilizing various information technologies and its fixations such as Internet, E-mail. CD-ROMs. Interactive Video Networks (Video Conferencing, Video on Demand), CableTV etc., which has no time or location limitation, is needed.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.8
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• pp.3741-3745
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• 2016

Background: This study was carried out to examine breast cancer risk and its fertility predictors in women aged ${\geq}35$. Materials and Methods: This cross-sectional study was conducted on 560 healthy women referred to health centers of Tabriz-Iran, 2013-2014. Five-year and lifetime risk of developing breast cancer were determined using the Gail model. General linear modeling was applied to determine breast cancer predictors. Results: The mean age of the subjects was 42.7 (SD: 7.7) years. Mean 5-year and lifetime risks of developing breast cancer were determined to be 0.6% (SD: 0.2%) and 8.9% (SD: 2.5%), respectively. Variables of family history of breast cancer, age, age at menarche, parity, age at first childbirth, breastfeeding history, frequency of breastfeeding, method of contraception, marital status and education were all found to be predictors of breast cancer risk. Conclusions: According to the results of this study, screening programs based on the Gail model should be implemented for Iranian people who have a high risk for breast cancer in order to facilitate early detection and better plan for possible malignancies.