• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.605-617
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• 2005

A sudden discharge of mass flow from the exit of a duct can generate an impulsive wave, generally leading to undesirable noise and vibration problems. The present study develops an understanding of unsteady flow physics with regard to the impulsive wave discharged from a duct, using a numerical method. A second order total variation diminishing scheme is employed to solve three-dimensional, unsteady, compressible Euler equations. Computations are performed for several exit conditions with and without ground and wall effects under a change in the Mach number of an initial shock wave from 1.1 to 1.5. The results obtained show that the directivity and magnitude of the impulsive wave discharged from the duct are significantly influenced by the initial shock Mach number and by the presence of the ground and walls.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.462-467
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• 2001

The present study addresses a computational work of the weak shock wave propagatings inside a silencer system of automobile exhaust pipe. Four different types of the silencer systems and the initial shock wave Mach number $M_s$ of $1.01\sim1.30$ are applied to investigate their effects on the noise reduction and the flow field in a silencer system. The results obtained from the present computational work are compared with the experimental results. The second order total variation diminishing (TVD) scheme is employed to solve the two dimensional, compressible, unsteady, Euler equations. The present computational results predict the experimental results with a quite good accuracy. Of the four silencer systems applied, the most desirable silencer system to reduce the peak pressure at the exit of the exhaust pipe is discussed.

• 국제학술발표논문집
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• The 8th International Conference on Construction Engineering and Project Management
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• pp.493-502
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• 2020

Traditionally, road projects are initiated based on an assessment of their economic benefit, after which the environmental, social and governance effects are addressed discretely for the project according to a set of predetermined alternatives. Sustainable road infrastructure planning is vital as issues like diminishing access to road construction supplies, water scarcity, Greenhouse Gas emissions, road-related fatalities and congestion pricing etc., have imposed severe economic, social, and environmental damages to the society. In the process of addressing these sustainability factors in the operational phase of the project, the dynamics of these factors are generally ignored. This paper argues that effective delivery of sustainable roads should consider such dynamics and highlights how different aspects of sustainability have the potential to affect project sustainability. The paper initially presents the different sustainability-assessment tools that have been developed to determine the sustainability performance of road projects and discuss the inability of these tools to model the interrelationships among sustainability-related factors. The paper then argues the need for a new assessment framework that facilitates modelling these dynamics at the macro-level (system level) and helping policymakers for sustainable infrastructure planning through evaluating regulatory policies.

• 종양간호연구
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• 제6권2호
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• pp.121-132
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• 2006

Purpose: The purpose of this study was to describe the lived experience of the patients with cancer participating in a clinical trial for the development of a new drug. Method: This study was based on a phenomenological approach. The eight patients participating in a clinical trial were selected as the participations of this study. The data were obtained through in-depth interviews from the participants and were analyzed using the Giorgi method. Results: Essential experiences of the patients with cancer under a clinical trial consisted of anticipating recovery of physical health and a social role, passing the strict criteria of a clinical trial, diminishing economic burden, satisfaction with special treatment receiving, social contribution, concerns about side effects and withdrawal from the clinical trial, conflicts as a participant, pain, limited administration of other treatments, regret for giving up other treatments, strict compliance with instructions, prevention of side effects and maintaining desirable life-style. Integrated units of meaning of these components were hope, good luck, a sense of satisfaction, fear, distress, and the will of self-control. Conclusion: The most essential meaning of the cancer patients participating in a clinical trial was hope. Hope was found to be a primary factor reinforcing the will of self-management. The results of this study can be of great help to the research nurses to understand the lived experience of the patients with cancer and to plan an effective nursing intervention for the patients.

• 한국결정성장학회지
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• 제8권4호
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• pp.555-562
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• 1998

비균일 자장이 도가니에 인가되어 있는 상황에서 정상상태의 Czochralski 유동장과 비정상상태의 산소농도장에 대한 연구가 수치해석적인 방법으로 연구되었다. 여기에서 기준 자장의 세기가 B=0.1T, 0.2T, 0.3T의 경우에 대한 연구가 수행되었다. 가열에 의한 부력의 효과와 자유표면의 표면장력에 의한 열모세관 효과에 의하여 유발되는 자오면 유동은 비균일 자장에 의하여 차등적으로 억제되고 있다. 자자의 세기가 증가하면 자오면 유동에서 발생하는 순환류의 중심은 결정으로 접근하며, 순환류의 크기도 작아진다. 결정으로 흡수되는 산소의 세기가 클수록 낮아지며 농도분포는 균일해지는 경향을 갖는다.

• 지역사회간호학회지
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• 제22권2호
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• pp.121-130
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• 2011

Purpose: The purpose of this study is to understand the effects of a program to improve self-esteem and smoking cessation self-efficiency on smoking high school students' self-esteem, smoking cessation self-efficiency, amount of smoking, cotinine in urine, and carbon monoxide while exhalation. Methods: This research was conducted as a quasi-experimental pretest and posttest control and experimental group methodological comparison study. The subjects were 45 smoking high school students (Exp.=22, Cont.=23) in U City. Data were collected from October 19 to December 7, 2010, and analyzed using the SPSS/WIN 12.0 program by frequency, Mann-Whitney test, means, standard deviations, and Willcoxon signed rank test. Results: After the treatment, those belonging to the experimental group showed significantly increased self-esteem and smoking cessation self-efficacy and also showed decreased amount of smoking, cotinine in urine, and carbon monoxide while exhalation compared to the control group. Conclusion: The self-esteem and smoking cessation self-efficacy improvement program was effective in improving self-esteem and smoking cessation self-efficacy and in diminishing the amount of smoking, cotinine in urine and carbon monoxide while exhalation. Therefore, this program is recommended as a smoking cessation strategy for smoking adolescents.

• Fibers and Polymers
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• 제5권1호
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• pp.75-81
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• 2004

To obtain high molecular weight (HMW) poly(methyl methacrylate) (PMMA) with high conversion, methyl methacrylate (MMA) was polymerized in suspension using a room temperature initiator, 2,2'-azobis(2,4-dimethylvaleronitrile) (ADMVN), and the effects of polymerization conditions on the polymerization behavior of MMA and the molecular parameters of PMMA were investigated. On the whole, the experimental results well corresponded to the theoretically predicted tendencies. These effects could be explained by a kinetic order of ADMVN concentration calculated by an initial rate method and an activation energy difference of polymerization obtained from the Arrhenius plot. Suspension polymerization at 25℃ by adopting ADMVN proved to be successful in obtaining PMMA of HMW (number-average degree of polymerization (P/sub n/): 30,900-36,100) and of high yield (ultimate conversion of MMA into PMMA: 83-93 %) with diminishing heat generated during polymerization. The P/sub n/ and lightness were higher and polydispersity index was lower with PMMA polymerized at lower temperatures.

• 대한간호학회지
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• 제37권7호
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• pp.1073-1079
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• 2007

Purpose: The purpose of this study was to identify the effects of a smoking cessation program on the amount of smoking and nicotine dependence and the self-efficacy of smoking cessation for smoking workers. Methods: The total number of subjects was 38 smokers and was divided into two: 16 smokers were placed in the experimental group and 22 in the control group. A nonequivalent control group pretest-posttest design was used. The smoking cessation program consisted of two sessions and was implemented for two hours daily for five days. Data was analyzed by using the SPSS/WIN 11.0 program with $X^2-test$, t-test or Mann-Whitney U and ANCOVA. Results: After the treatment, those belonging to the experimental group showed a significantly decreased amount of smoking, a decreased nicotine dependency and increased self-efficacy compared to the control group. Conclusion: The smoking cessation program was effective for diminishing the amount of smoking, decreasing nicotine dependence and improving self-efficacy. Therefore, this program is recommended as a smoking cessation strategy for adult smokers.

• 한국항공우주학회지
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• 제35권11호
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• pp.1022-1027
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• 2007

베어링 지지부가 터보펌프용 인듀서의 성능에 미치는 영향에 대하여 실험적 및 계산적 연구가 수행되었다. 양정, 효율, 인듀서 슈라우드 압력 분포 등을 측정하였으며 유동해석 계산결과와 비교하였다. 유동해석결과는 실험결과와 비교하여 전체적으로 잘 일치하는 결과를 얻었다. 그러나 입구의 역류가 심해지는 저유량 작동조건에서는 계산값과 시험값이 다소의 차이를 보였다. 역류가 심해지는 저유량에서 베어링 지지부가 역류의 발달을 방해하여 인듀서의 수력성능을 향상시키는 것을 관찰하였으며, 베어링 지지부의 설치는 흡입성능에 큰 영향을 미치지 못함을 확인하였다.

• 대한소아치과학회지
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• 제25권3호
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• pp.569-575
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• 1998

The purpose of this study was to evaluate the remineralization effects of fluoride-containing sealant on the artificially created enamel carious lesions. The fluoride release from the specimen of fluoride-containing sealants, the effect on enamel acid solubility and micro-hardness from the experimental sealants when applied to carious enamel surfaces were investigated. The obtained results were as follows; 1. Fluoride was a rapid rate of release during the first day, with the amount diminishing with time. The amount of fluoride released from Fuji Ionomer type III was higher than that from Teethmate-F and Helioseal-F during the 28 days of immersion(P<0.05). 2. The enamel solubility of carious enamel surface was higher than that in the Teethmate-F, Helioseal-F, and Fuji Ionomer type III (P<0.05), and there was no significant difference with Teethmate-A and Helioseal(P>0.05). 3. The microhardness value of carious enamel surface was lowest. However, there was no significant difference between the other sealants with respect to their effects on enamel hardness(P>0.05).