• 대한산업공학회지
• /
• 제14권2호
• /
• pp.91-97
• /
• 1988

In accelerated life testing, a relationship is usually assumed between the stress and a parameter of the lifetime distribution. However, the true relationship is not usually known, and therefore, the experimenter may wish to provide protections against the likely departures from the assumed relationship. This paper considers an accelerated life test in which two stress levels are involved, and the lifetime of each test item at a stress level is assumed to have an independent, identical, exponential distribution. For the case where a first order relationship is assumed while the true one is quadratic, a procedure is developed for allocating test items to stress levels such that the bias and/or the variance of the estimated(log-transformed) mean lifetime at the use condition is minimized.

• 한국지구과학회지
• /
• 제40권4호
• /
• pp.392-405
• /
• 2019

Biogeochemical processes play an important role in ocean environments and can affect the entire Earth's climate system. Using an ocean-biogeochemistry model (NEMO-TOPAZ), we investigated the effects of changes in albedo and wind stress caused by phytoplankton in the equatorial Pacific. The simulated ocean temperature showed a slight decrease when the solar reflectance of the regions where phytoplankton were present increased. Phytoplankton also decreased the El $Ni{\tilde{n}}o$-Southern Oscillation (ENSO) amplitude by decreasing the influence of trade winds due to their biological enhancement of upper-ocean turbulent viscosity. Consequently, the cold sea surface temperature bias in the equatorial Pacific and overestimation of the ENSO amplitude were slightly reduced in our model simulations. Further sensitivity tests suggested the necessity of improving the phytoplankton-related equation and optimal coefficients. Our results highlight the effects of altered albedo and wind stress due to phytoplankton on the climate system.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
• /
• pp.497-497
• /
• 2013

Semiconducting amorphous InGaZnO (a-IGZO) has attracted significant research attention as improved deposition techniques have made it possible to make high-quality a-IGZO thin films. IGZO thin films have several advantages over thin film transistors (TFTs) based on other semiconducting channel layers.The electron mobility in IGZO devices is relatively high, exceeding amorphous Si (a-Si) by a factor of 10 and most organic devices by a factor of $10^2$. Moreover, in contrast to other amorphous semiconductors, highly conducting degenerate states can be obtained with IGZO through doping, yet such a state cannot be produced with a-Si. IGZO thin films are capable of mobilities greaterthan 10 $cm^2$/Vs (higher than a-Si:H), and are transparent at visible wavelengths. For oxide semiconductors, carrier concentrations can be controlled through oxygen vacancy concentration. Hence, adjusting the oxygen partial pressure during deposition and post-deposition processing provides an effective method of controlling oxygen concentration. In this study, we deposited IGZO thinfilms at optimized conditions and then analyzed the film's electrical properties, surface morphology, and crystal structure. Then, we explored how to generate IGZO thin films using DC magnetron sputtering. We also describe the construction and characteristics of a bottom-gate-type TFT, including the output and transfer curves and bias stress instability mechanism.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2010년도 하계학술대회 논문집
• /
• pp.391-391
• /
• 2010

The stability enhancement of Znic oxide thin film transistor deposited by PLD-DBD has been reported here using the bias temperature stress test. Znic oxide (ZnO) thin films were deposited on $SiO_2$/Si (100) by pulsed laser deposition method with and without dielectric barrier discharge (DBD) method. The DBD is the efficient method to adopt the nitrogen ions into the thin films. The TFT characteristics of ZnO TFTs with and without Nirogen (N) doping show similar results with $I_{on/off}$ of $10^5{\sim}10^6$. However. the bias temperature stress (BTS) test of N-doped ZnO TFT with DBD shows higher stability than that of ZnO TFT.

• Electronic Materials Letters
• /
• 제14권6호
• /
• pp.749-754
• /
• 2018

Previous studies have reported on the mechanical robustness and chemical stability of flexible amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) on plastic substrates both in flat and curved states. In this study, we investigate how the polyimide (PI) substrate affects hydrogen concentration in the a-IGZO layer, which subsequently influences the device performance and stability under bias-temperature-stress. Hydrogen increases the carrier concentration in the active layer, but it also electrically deactivates intrinsic defects depending on its concentration. The influence of hydrogen varies between the TFTs fabricated on a glass substrate to those on a PI substrate. Hydrogen concentration is 5% lower in devices on a PI substrate after annealing, which increases the hysteresis characteristics from 0.22 to 0.55 V and also the threshold voltage shift under positive bias temperature stress by 2 ${\times}$ compared to the devices on a glass substrate. Hence, the analysis and control of hydrogen flux is crucial to maintaining good device performance and stability of a-IGZO TFTs.

• 한국산학기술학회논문지
• /
• 제17권9호
• /
• pp.141-155
• /
• 2016

본 연구는 중년기 성인의 뇌졸중 관련 건강지식, 낙관적 편견 및 건강증진 생활양식 정도와 관계를 파악하고, 건강증진 생활양식에 미치는 효과를 파악하기 위한 서술적 조사연구이다. 연구기간은 2015년 7월 15일부터 8월 15일이며, 연구대상자는 40세 이상 60세 미만의 성인 191명이며, 자료 수집은 구조화된 설문지를 이용한 자가 보고식으로 이루어졌다. 자료분석은 PASW Statistics 21.0과 AMOS 21.0 프로그램을 사용하였으며, 분산분석, 상관성분석, 구조방정식 모형 분석 등을 실시하였다. 중년기 성인은 뇌졸중 위험요인으로 흡연과 고혈압을 당뇨병보다 높게 인식하였으며, 뇌졸중에 대한 낙관적 편견은 미미하였다. 뇌졸중 관련 건강지식은 낙관적 편견(r=-.143, p=.048), 건강증진 생활양식(r=.268, p=<.001)과 상관관계가 있었고, 낙관적 편견은 건강증진 생활양식의 대인관계 및 스트레스 행위(r=.177, p=.014)와 상관관계가 있었다. 또한 뇌졸중 관련 건강지식이 낙관적 편견보다 건강증진 생활양식에 더 큰 영향을 미치는 것으로 확인하였다. 결론적으로 중년기 성인의 뇌졸중에 관한 능동적인 정보획득과 건강 지식, 낙관적 편견이 뇌졸중 관련 건강증진 생황양식에 중요한 요인임을 알 수 있었다. 그러므로 중년기 성인의 뇌졸중 관련 건강증진 생활양식을 향상시키기 위한 교육 프로그램에는 뇌졸중 관련 건강지식을 높이고, 낙관적 편견을 감소시킬 수 있는 방안이 고려되어야 할 것이다.

• Journal of Information Display
• /
• 제12권4호
• /
• pp.209-212
• /
• 2011

The threshold voltage shift (${\Delta}V_{th}$) under positive-voltage bias stress (PBS) of InGaZnO (IGZO) thin-film transistors (TFTs) annealed at different temperatures in air was investigated. The dramatic degradation of the electrical performance was observed at the sample that was annealed at $700^{\circ}C$. The degradation of the saturation mobility (${\mu}_{sat}$) resulted from the diffusion of indium atoms into the interface of the IGZO/gate insulator after crystallization, and the degradation of the subthreshold slope (S-factor) was due to the increase in the interfacial and bulk trap density. In spite of the degradation of the electrical performance of the sample that was annealed at $700^{\circ}C$, it showed a smaller ${\Delta}V_{th}$ under PBS conditions for $10^4$ s than the samples that were annealed at $500^{\circ}C$, which is attributed to the nanocrystal-embedded structure. The sample that was annealed at $600^{\circ}C$ showed the best performance and the smallest ${\Delta}V_{th}$ among the fabricated samples with a ${\mu}_{sat}$ of $9.38cm^2/V$ s, an S-factor of 0.46V/decade, and a ${\Delta}V_{th}$ of 0.009V, which is due to the passivation of the defects by high thermal annealing without structural change.

• 한국전기전자재료학회논문지
• /
• 제25권1호
• /
• pp.24-28
• /
• 2012

In this study, we fabricated an amorphous InGaZnO pseudo-MOS transistor (a-IGZO ${\Psi}$-MOSFET) with a stacked $Si_3N_4/SiO_2$ (NO) gate dielectric and evaluated reliability of the devices with various thicknesses of a $SiO_2$ buffer layer. The roles of a $SiO_2$ buffer layer are improving the interface states and preventing degradation caused by the injection of photo-created holes because of a small valance band offset of amorphous IGZO and $Si_3N_4$. Meanwhile, excellent electrical properties were obtained for a device with 10-nm-thick $SiO_2$ buffer layer of a NO stacked dielectric. The threshold voltage shift of a device, however, was drastically increased because of its thin $SiO_2$ buffer layer which highlighted bias and light-induced hole trapping into the $Si_3N_4$ layer. As a results, the pseudo-MOS transistor with a 20-nm-thick $SiO_2$ buffer layer exhibited improved electrical characteristics and device reliability; field effective mobility(${\mu}_{FE}$) of 12.3 $cm^2/V{\cdot}s$, subthreshold slope (SS) of 148 mV/dec, trap density ($N_t$) of $4.52{\times}1011\;cm^{-2}$, negative bias illumination stress (NBIS) ${\Delta}V_{th}$ of 1.23 V, and negative bias temperature illumination stress (NBTIS) ${\Delta}V_{th}$ of 2.06 V.

• 가정간호학회지
• /
• 제28권3호
• /
• pp.266-275
• /
• 2021

Purpose: This study was conducted to explore the mediating effect of menopausal symptoms in the relationship between occupational stress and quality of Life in middle-aged working women Method: Data collection was conducted from May 2019 to July 2019. A sample of 130 middle-aged working women was recruited from three cities in Korea. The collected data were analyzed using descriptive statistics, t-tset, ANOVA, Scheffé test, pearson correlation, and a three step regression analysis. The mediating effect was analyzed using PROCESS macro with a 95.0% bias corrected bootstrap confidence interval (5,000 bootstraps resampling). Results: Quality of life had a negative correlation with occupational stress and menopausal symptoms, while there was a positive correlation between occupational stress and menopausal symptoms. Menopausal symptoms showed a direct effect on quality of life through occupational stress as a mediating variable. Conclusion: These results suggest that menopausal symptoms should be considered when developing interventions to improve quality of life through occupational stress control of middle-aged working women

• 동의신경정신과학회지
• /
• 제28권3호
• /
• pp.165-182
• /
• 2017

Objectives: The purpose of this systematic review was to understand clinical usefulness of Emotional Freedom Techniques (EFT) on students' mental health. Methods: Ten databases were included to extract clinical studies on effects of EFT intervention with students. Characteristics of selected studies were described, and biases were assessed with Risk of Bias (RoB) or Risk of Bias Assessment for Non-Randomized Studies (RoBANS). Results: A total of 14 clinical trials were extracted for analysis. There were 8 randomized-controlled trials (RCTs), 2 non-randomized-controlled trials (nRCTs), and 4 before-after studies. EFT have significant clinical usefulness in public speaking anxiety, test anxiety, stress, depression, learning related emotions, adolescent anxiety, and eating issues. The risk of selection bias in most studies was high or uncertain. Conclusions: EFT is an effective clinical technique for managing students' mental health issues. However, the included studies have been conducted with relatively poor quality and small sample size. Clinical trials with high quality study design and well-designed EFT education programs are needed to generalize clinical usefulness.