• Bulletin of the Korean Chemical Society
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• 제19권8호
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• pp.847-851
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• 1998

13C, 15N, and 29Si NMR chemical shifts have been computed for selected X-substituted silatranes (X=Cl, F, H, CH3) using Gauge-Including Atomic Orbitals (GIAO) and Continuous Set of Gauge Transformations (CSGT) at the Hartree-Fock level of theory. The isotropic 13C chemical shifts are largely insensitive to substituent-induced structural changes. In this study, the isotropic 13C chemical shifts GIAO and CSGT calculations at the HF/6-31G and HF/6-31G* levels are sufficiently accurate to aid in experimental peak assignments. The isotropic 13C chemical shifts X-substituted silatranes at HF/6-31G* level are approximately 4 ppm different from the experimental values. In contrast, the isotropic 15N and 29Si chemical shifts and the chemical shielding tensors are quite sensitive to substituent-induced structural changes. These trends are consistent with those of the experiment. The 15N chemical shift parameters demonstrate a very clear correlation with Si-N distance, especially when we use the polarization function. Changes in anisotropy, 3a as well as in the 15N isotropic chemical shifts are due primarily to changes in the value of a.. But in case of "Si the correlations are not as clean as for the 15N chemical shift.

• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.981-985
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• 1997

13C, 15N, and 29Si NMR chemical shifts have been computed for selected X-substituted silatranes (X=Cl, F, H, CH3) using Gauge-Including Atomic Orbitals (GIAO) at the Hartree-Fock level of theory. The isotropic 13C chemical shifts are largely insensitive to substituent-induced structural changes. In this study, the isotropic 13C chemical shifts between 1-methyl- and 1-hydrogensilatranes by GIAO-SCF calculation at the HF/6-31G level are very similar. But the results of 1-chloro- and 1-fluorosilatranes are about 4 ppm different from the experimental values. In contrast, the isotropic 15N and 29Si chemical shifts and the chemical shielding tensors are quite sensitive to substituent-induced structural changes. These trends are consistent with those of the experiment. The isotropic 15N chemical shift demonstrates a very clear correlation with Si-N distance. But in case of 29Si the correlations are not as clean as for the 15N chemical shift; the calculated variation in the 29Si chemical shift is much larger.

• 한국시스템다이내믹스연구
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• 제5권1호
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• pp.127-142
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• 2004

Feedback loop dominance is a key concept to understand structural driving forces of system behavior. In this paper, we propose two kinds of shifts in dominant feedback loops: continuous shifts (CS) and discrete shifts (DS). With the help of questionnaires, we verified three hypotheses regarding cognitive biases in perceiving the shifts in dominant feedback loops: 1) failure in perceiving continuous shifts, 2) tendency of decision making based on discrete shifts, and 3) different perception on the dominant feedback loops between level variables and rate variables. We discussed the implication of these cognitive biases on time delay and timing strategy in decision-making processes.

• 임상간호연구
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• 제19권3호
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• pp.309-320
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• 2013

Purpose: This study was conducted to identify relationships among circadian types, sleep quality, and adaptation to night shifts among nurses working on two or three day night duties. Methods: The participants were 199 ward nurses from two university hospitals in Gyeongnam province. Each nurse worked on two or three day night duties. Data were collected between September 24 and October 14, 2012 and analyzed using t-test, ANOVA, $Scheff{\grave{e}}$ test, Pearson correlation, and multiple regression with SPSS/WIN 14.0 program. Results: Mean scores for sleep quality and adaptation to night shifts was $4.92{\pm}1.46$ on a 10-point scale and $2.66{\pm}0.47$ on a 5-point scale respectively. There were no significant differences in sleep quality and adaptation to night shifts according to circadian types of nurses. There were significant correlation between sleep quality and adaptation to night shifts (r=.25, p<.001). Factors affecting adaptation to night shifts were preference for night shifts, and subjective health status, which together explained about 35% of the total variance. Conclusions: Nurses working on two or three day night duties had low level of sleep quality and adaptation to night shifts. It is necessary to improve preference for night shifts and subjective health status for improving adaptation to night shifts of nurse.

• 응용통계연구
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• 제22권6호
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• pp.1191-1201
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• 2009

공정관리에서 작은 평균변화를 탐지하기 위하여 누적합 관리도를 사용하는 것이 일반적이다. 자기상관이 존재하는 공정의 경우 시계열 모형에 적합하여 구한 잔차를 관리도에 적용하는 모형기반 관리방법이 활용되고 있다. 그러나 공정에 일정한 크기의 지속적인 수준 변화가 발생하면 잔차에는 동적 평균변화의 패턴이 나타나게 되어 누적합 관리도의 탐지능력은 저하될 수 있다. 본 논문에서는 잔차에 등락을 반복하는 진동(oscillation) 특성의 동적 평균변화가 발생하는 ARMA(1,1) 모형을 대상으로, 그러한 변화를 효율적으로 탐지할 수 있는 새로운 OCUSUM 관리도를 제안하고 모의실험을 통해 최근에 소개된 기존의 CUSUM 관리도와 탐지능력을 비교하였다.

• 품질경영학회지
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• 제36권4호
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• pp.87-92
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• 2008

It is common to use CUSUM charts for detecting small level shifts in processes control, in which reference value(k) and decision interval(h) are the design parameters to be determined. To control process with autocorrelation, CUSUM charts could be applied to residuals obtained from fitting ARIMA models. However, constant level shifts in processes lead to varying mean shifts in residual processes and thus standard CUSUM charts may need to be modified. In this paper, we study the performance of CUSUM charts with various design parameters applied to autocorrelated processes, especially focussing on ARMA(1,1) models, and propose how they can be determined to get better performance in terms of the average run length.

• 한국응급구조학회지
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• 제25권3호
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• pp.81-92
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• 2021

Purpose: The aim of the study is to measure the quality of cardiopulmonary resuscitation (CPR) and the fatigue of rescuers wearing PPE (Level D) during a CPR session and to ultimately provide suggestions of safety standards for rescuers. Methods: 36 subjects were enrolled in the study. The subjects were divided randomly into three groups of two-members, three-members, and four-members. Each group performed CPR for 30 minutes. Blood lactate concentration, heart rate, rating of perceived exertion, chest compression depth and rate were measured before experiment and after each cycle. Results: There was a difference in the blood lactate concentration during CPR cycle by member of shifts (p=.014). The blood lactate concentration increased during CPR (p=.000). Subjective fatigue was a significant difference of chest compression in cycles 3, 4, and 5 for the member of shifts during CPR (p=.049, p=.009, p=.015). Depth and rate of chest compression were not different for the member of shifts during CPR. Conclusion: It is necessary to establish standards for the member of shifts during CPR, to reduce the fatigue of rescuers.

• Communications for Statistical Applications and Methods
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• 제19권1호
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• pp.177-182
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• 2012

A structural break in the level as well as in the innovation variance has often been exhibited in economic time series. In this paper we propose robust unit root tests based on a sign-type test statistic when a time series has a shift in its level and the corresponding volatility. The proposed tests are robust to a wide class of partially stationary processes with heavy-tailed errors, and have an exact binomial null distribution. Our tests are not affected by the size or location of the break. We set the structural break under the null and the alternative hypotheses to relieve a possible vagueness in interpreting test results in empirical work. The null hypothesis implies a unit root process with level shifts and the alternative connotes a stationary process with level shifts. The Monte Carlo simulation shows that our tests have stable size than the OLSE based tests.

• 한국산업보건학회지
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• 제22권4호
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• pp.329-336
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• 2012

Objectives: The aim of this study is to analyze main problems on occupational safety and hygiene in construction sites and to suggest some improvement methods. In order to decrease industrial accidents, I emphasize the approach paradigm shifts according to characteristics of construction workers. Methods: Pointing out the irrationality of current institutions by comparing bad outcomes of occupational safety and hygiene in construction industry and characteristics of construction workers. Results: In order to decrease industrial accidents, we need some approach paradigm shifts; the supply method of industrial safety and health fundamentals on the construction industry level, the accident rate calculation by using the actual construction workforce instead of an estimation, institutionalizing the prevention efforts themselves for industrial accidents, securing enough production costs for the precondition of occupational safety and hygiene in construction sites. Conclusions: I ascertain the need of the approach paradigm shifts for decreasing industrial accidents in the construction industry.

• Bulletin of the Korean Chemical Society
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• 제24권11호
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• pp.1649-1654
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• 2003

We have investigated substituent effect on the stabilization energies, and nucleus-independent chemical shifts of pentafulvalenes and on the electronic structures of the corresponding polypentafulvalenes to design environmentally stable semiconductive or conductive polymers. Geometrical optimizations of the molecules were carried out at the density functional level of theory with B3LYP hybrid functional and 6-311+G(d) basis set. Stabilization energies were estimated using isodesmic and homodesmotic reactions. As a criterion of aromaticity nucleus-independent chemical shifts of the molecules were computed using GIAO approach. For the polymers the geometrical parameters were optimized through AM1 band calculations and the electronic structures were obtained through modified extended Huckel band calculations. It is found that strong electronwithdrawing substituents increase isodesmic and homodesmotic stabilization energies of pentafulvalene, though it does not increase the aromaticity. Nitro-substituted pentafulvalene is estimated to have stabilization energy as much as azulene. However, substitution either with electron-donating groups or with electronwithdrawing groups does not significantly affect the electronic structures of polypentafulvalene and poly (vinylenedioxypentafulvalene).