• Journal of the Society of Naval Architects of Korea
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• v.29 no.4
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• pp.7-17
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• 1992

Developments in the emerging field of Computational Fluid Dynamics(CFD), which is made possible by the supercomputer technologies, introduce a new problem of analysing the massive amount of output produced. This problem is common to fields of computational science and engineering. Scientific visualization is to solve this problem by applying advanced technologies of computer graphics. Methods of scientific visualization are studded to visualize calculated flow fields. Different methods of scientific visualization has been surveyed, analysed and compared to select one method, iso-surface. Methods of constructing iso-surfaces from a 3-D data set have been studied. A new algorithm for constructing iso-surfaces has been developed. The algorithm can be classified as one of surface tiling methods. To develope a portable visualization system the international standard PHIGS PLUS and its implementation on X-Window system, PEX, have been selected as the development environment. A prototype of visualization system has been developed. The developed visualization system has been tried to visualize several well-known flow fields.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.285-285
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• 2011

EUVL (Extreme Ultra Violet Lithography) is one of competitive lithographic technologies for sub-30nm fabrication of nano-scale Si devices that can possibly replace the conventional photolithography used to make today's microcircuits. Among the core EUVL technologies, mask fabrication is of considerable importance since the use of new reflective optics having a completely different configuration compared to those of conventional photolithography. Therefore new materials and new mask fabrication process are required for high performance EUVL mask fabrication. This study investigated the etching properties of SnO2 (Tin Oxide) as a new absorber material for EUVL binary mask. The EUVL mask structure used for etching is SnO2 (absorber layer) / Ru (capping / etch stop layer) / Mo-Si multilayer (reflective layer) / Si (substrate). Since the Ru etch stop layer should not be etched, infinitely high selectivity of SnO2 layer to Ru ESL is required. To obtain infinitely high etch selectivity and very low LER (line edge roughness) values, etch parameters of gas flow ratio, top electrode power, dc self - bias voltage (Vdc), and etch time were varied in inductively coupled Cl2/Ar plasmas. For certain process window, infinitely high etch selectivity of SnO2 to Ru ESL could be obtained by optimizing the process parameters. Etch characteristics were measured by on scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses. Detailed mechanisms for ultra-high etch selectivity will be discussed.

• The Journal of Korean Academic Society of Nursing Education
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• v.7 no.2
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• pp.298-307
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• 2001

The purpose of this study was to test the effect of the health education on college students. The content of the health education was consisted of significance of health, smoking, alcohol use and sexuality, birth control, exercise and nutrition, chronic illness, contagious disease, stress management. Two groups non-equivalent to pre and post test quasi-experimental research design were used in this study. The total number of subjects were 174 college students who did not have a health related major. The experimental group attended this health education program for 16 weeks and the control group attended other liberal arts and science classes for 16 weeks. Data were analysed with the SPSS window program. The homogeneity between the experimental and the control group pretest data was tested by $X^2$ test and t-test. The differences in stress, self-esteem, general self-efficacy, locus of control and health promoting behaviors after the health education were tested with the repeated measure ANOVA. The results were as follows: 1. There was no significant difference in general characteristics, stress, self- esteem, general self-efficacy, locus of control and health promoting behaviors between the two groups before the health education. 2. There was a significant difference in stress(p= .000) and health promoting behavior (p= .000) between the two groups after the health education. 3. There was no significant difference in self-esteem(p= .531), self-efficacy(p= .110) and locus of control between the two groups after the health education. From the results above, it can be concluded that this health education for the college students was effective to relieve stress and improve health promoting behaviors. The above results suggest that repeated studies are needed for another college students and various health education programs should be developed to promote the health of the populace considering many health related concepts.

• The Journal of Korean Academic Society of Nursing Education
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• v.8 no.1
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• pp.61-71
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• 2002

purpose : The purpose of this study was to find out the influencing factors of smoking-cessation behavior of patients with coronary heart disease and to suggest the model of smoking-cessation behavior which was based on the relationship between influencing factors and then to test its fitness empirically. method : This study was based on the Theory of Reasoned Action and a hypothetical model was constructed with fifteen paths in consideration of main predictive factors of smoking-cessation behavior such as biological factor, disease-related characteristics, self-efficacy, supportive factor, environmental factor, disease-related perception factor, intention-to-quit, and psychological factor. The validity of a smoking- cessation model was tested to 264 patients with coronary heart disease by using SPSS 8.0 and Window LISREL 8.12a. results : 1. Seven of the 15 paths of smoking-cessation behavior proved to be significant. 2. The final model excluded three paths in the hypothetical model was demonstrated to be improved by $x^2$=44.31 (df=38, p=.22), Goodness of Fit Index (GFI)=.98, Adjusted Goodness of Fit Index (AGFI)=.96, Non-Normed Fit Index(NNFI)=1.00, Normed Fit Index(NFI)=1.00, and Root Mean Square Residual(RMR)=.24. 3.The smoking-cessation behavior was influenced directly by biological factor, self-efficacy, supportive factor, environmental factor, intention-to-quit, and psychological factor. The smoking-cessation behavior was accounted for 82% of variance by these factors. conclusion : although the adolescents' smoking behavior can be predicted by only smoking intention, it is hard to predict the adults' smoking-cessation behavior by only this factor. Therefore, intention-to-quit, self-efficacy, supportive factor should be improved because these are promotive factors for smoking-cessation behavior. Biological factor, environmental factor, and psychological factor are inhibitive factors, so nicotine replacement therapy is helpful to the high nicotine-dependents, and ex-smokers avoid other smokers in their environment and also patients should learn and practice the stress coping-skills.

• Korean Journal of Materials Research
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• v.28 no.5
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• pp.301-307
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• 2018

A boron-doped diamond(BDD) electrode is attractive for many electrochemical applications due to its distinctive properties: an extremely wide potential window in aqueous and non-aqueous electrolytes, a very low and stable background current and a high resistance to surface fouling. An Ar gas mixture of $H_2$, $CH_4$ and trimethylboron (TMB, 0.1 % $C_3H_9B$ in $H_2$) is used in a hot filament chemical vapor deposition(HFCVD) reactor. The effect of argon addition on quality, structure and electrochemical property is investigated by scanning electron microscope(SEM), X-ray diffraction(XRD) and cyclic voltammetry(CV). In this study, BDD electrodes are manufactured using different $Ar/CH_4$ ratios ($Ar/CH_4$ = 0, 1, 2 and 4). The results of this study show that the diamond grain size decreases with increasing $Ar/CH_4$ ratios. On the other hand, the samples with an $Ar/CH_4$ ratio above 5 fail to produce a BDD electrode. In addition, the BDD electrodes manufactured by introducing different $Ar/CH_4$ ratios result in the most inclined to (111) preferential growth when the $Ar/CH_4$ ratio is 2. It is also noted that the electrochemical properties of the BDD electrode improve with the process of adding argon.

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.282-286
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• 2011

The artificial increase in the solar intensity incident on solar cells using lenses or mirrors can allow solar cells to generate equivalent power with a lower cost. In application areas of Fresnel lenses as solar concentrators, several variations of design were devised and tested. Some PV systems still use commercially available flat Fresnel lenses as concentrators. In this study, we designed and optimized flat Fresnel lens and the 'light pipe' to develop 500X concentrated solar PV system. We performed rigorous ray tracing simulation of the flat Fresnel lens and light-pipe. The light-pipe can play imporatant roles of redistributing solar energy at the solar cell and increase the mechanical tolerance so that it can increase the lifetime of the high-concentration solar PV system and decrease the cost of manufacturing. To investigate the sensitivity of the solar power generated by the concentrated solar PV according to the performance of lens and light pipe, we performed raytracing and executed a simulation of electrical performance of the solar cell when it is exposed to the non-uniform illumination. We could conclude that we can generate 95 % or more energy compared with the energy that can be generated by perfectly uniform illumination once the total energy is given the same.

• Child Health Nursing Research
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• v.18 no.3
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• pp.150-156
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• 2012

Purpose: The main purposes of this study were to assess maternal-fetal attachment (MFA) of the expectant mothers of a fetus with a prenatal diagnosis of congenital heart disease (CHD) and to identify factors associated with MFA. Methods: The methodology was a cross sectional survey study using a self-administered questionnaire. Thirty pregnant women carrying a fetus with a prenatal diagnosis of CHD and 30 pregnant women with a normal fetus were enrolled in this study. The MFA Scale and PPS (The Prenatal Psychosocial Profile) were used to collect data. Data were analyzed using SPSS 20.0 Window version. Descriptive statistics, $X^2$-test and t-test were used to compare the two groups. The factors associated with MFA were identified by multiple regression analysis. Results: There was no significant difference between the two groups in MFA and social support from spouse was the only variable showing a significant difference. The model from the multiple regression analysis explained 33.8% of MFA for both groups. Conclusion: MFA of expectant mothers with a prenatal diagnosis of CHD and of mothers with a normal fetus were not significantly different. It is important that health care providers encourage expectant fathers to support the expectant mothers to increase MFA.

• Korean Journal of Materials Research
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• v.12 no.1
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• pp.36-43
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• 2002

In this study, the nanosized ZnS thin films that can be used for fabrication of blue light-emitting diodes, electro-optic modulators, and n-window layers of solar cells were grown by the solution growth technique (SGT), and their surface morphology and film thickness and grain size dependence on the growth conditions were examined. Based on these results, the quantum size effects of ZnS were systematically investigated. Governing factors related to the growth condition were the concentration of precursor solution, growth temperature, concentration of aq. ammonia, and growth duration. X-ray diffraction patterns showed that the ZnS thin film obtained in this study had the cubic structure ($\beta$-ZnS). With decreasing growth temperature and decreasing concentration of precursor solution, the surface morphology of film was found to be improved. Also, the film thickness depends largely on the ammonia concentration. In particular, this is the first time that the surface morphology dependence of ZnS film grown by SGT on the ammonia concentration is reported. The energy band gaps of samples were determined from the optical transmittance values, and were shown to vary from 3.69 eV to 3.91 eV. These values were substantially higher than 3.65 eV of bulk ZnS. It was also shown that the quantum size effect of SGT grown ZnS is larger than that of the ZnS films grown by most other growth techniques.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.229.2-229.2
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• 2013

Yttrium oxide (Y2O3)는 band gap이 5.5 eV 정도로 상대적으로 넓고, 굴절상수가 1.8, 유전율이 10~15, Silicon 과의 격자 불일치가 작은 특성을 가지고 있다. 또한 녹는점이 높아 열적으로 안정하기 때문에 전자소자 및 광학소자에 다양하게 응용되는 물질이다. Y2O3 박막은 다양한 방법으로 증착할 수 있는데, 그 방법에는 e-beam evaporation, laser ablation, sputtering, thermal oxidation, metal-organic chemical vapor deposition, and atomic layer deposition (ALD) 등이 있다. ALD는 기판 표면에 흡착된 원자들의 자기 제한적 반응에 의하여 박막이 증착되기 때문에 박막 두께조절이 용이하고 step coverage와 uniformity 측면에서 큰 장점이 있다. 이전에는 Y(thd)3 and Y(CH3Cp)3 와 같은 금속 전구체를 이용하여 ALD를 진행하여, 증착 속도가 낮고 defect이 많아 non-stoichiometric한 조성의 박막이 증착되는 문제점이 있었다. 이번 연구에서는, (iPrCp)2Y(iPr-amd)와 탈이온수를 사용하여 Y2O3 박막을 증착하였다. Y2O3 박막 증착에 사용한 Y 전구체는 상온에서 액체이고 $192^{\circ}C$ 에서 1 Torr의 높은 증기압을 갖는다. Y2O3 박막 증착을 위하여 Y 전구체는 $150^{\circ}C$ 로 가열하여 N2 gas를 이용하여 bubbling 방식으로 공정 챔버 내로 공급하였다. Y2O3 박막의 ALD window는 $250{\sim}350^{\circ}C$ 였으며, Y 전구체의 공급시간이 5초에 다다르자 더 이상 증착 두께가 증가하지 않는 자기 제한적 반응을 확인할 수 있었다. 그리고 증착된 Y2O3 박막의 특성 분석을 위해 Atomic force microscopy (AFM)과 X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) 를 진행하였다. 박막의 Surface morphology 는 매끄럽고 uniform 하였으며, 특히 고체 금속 전구체를 사용했을 때와 비교하여 수산화물이 거의 없는 박막을 얻을 수 있었다. 그리고 조성 분석을 통해 증착된 Y2O3 박막이 stoichiometric하다는 것을 알수 있었다. 또한 metal-insulator-metal (MIM) 구조 (Ru/Y2O3/Ru) 의 resistor 소자를 형성하여 저항 스위칭 특성을 확인하였다.

• Journal of Korean Society for Quality Management
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• v.47 no.3
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• pp.497-508
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• 2019

Purpose: The purpose of this study is to overcome limitations of conventional studies that to predict Baltic Dry Index (BDI). The study proposed applications of Artificial Neural Network (ANN) named Long Short-Term Memory (LSTM) to predict BDI. Methods: The BDI time-series prediction was carried out through eight variables related to the dry bulk market. The prediction was conducted in two steps. First, identifying the goodness of fitness for the BDI time-series of specific ANN models and determining the network structures to be used in the next step. While using ANN's generalization capability, the structures determined in the previous steps were used in the empirical prediction step, and the sliding-window method was applied to make a daily (one-day ahead) prediction. Results: At the empirical prediction step, it was possible to predict variable y(BDI time series) at point of time t by 8 variables (related to the dry bulk market) of x at point of time (t-1). LSTM, known to be good at learning over a long period of time, showed the best performance with higher predictive accuracy compared to Multi-Layer Perceptron (MLP) and Recurrent Neural Network (RNN). Conclusion: Applying this study to real business would require long-term predictions by applying more detailed forecasting techniques. I hope that the research can provide a point of reference in the dry bulk market, and furthermore in the decision-making and investment in the future of the shipping business as a whole.