• Bulletin of the Korean Chemical Society
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• v.21 no.6
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• pp.577-582
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• 2000

Interdiffusion process at interfaces of chemically identical polymers (e.g., deuterated-nondeuterated pairs) with different molecular weights or polymers with similar physical properties, is studied here by varying the diffusion time. Considering the vacancy flux ($J_v$) and adopting the Cahn-Hilliard interracial energy in describing this system, we can see that the variation of the interfacial composition profile with time is asymetric and the interface moves towards the polymer with the lower molecular weight as interdiffusion progresses. Furthermore, interface shift $\Delta\chi$, which characterizes the interdiffusion between polymers, agrees well with the behaviors of the existing experimental data. We can also obtain the interface shift factor C, which can be converted into values of $D_s$ (self-diffusion coefficient of the smaller molecules), from the slopes of the linear fits to the data of the interface shift.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.14-14
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• 2011

Graphene is known to possess excellent thermal properties, including high thermal conductivity, that make it a prime candidate material for heat management in ultra large scale integrated circuits. For device applications, the key parameters are the thermal expansion coefficient and the thermal conductivity. There has been no reliable experimental determination on the thermal expansion coefficient of graphene whereas the estimates of the thermal conductivity vary widely. In this work, we estimate the thermal expansion coefficient of graphene on silicon dioxide by measuring the temperature dependence of the Raman spectrum. The shift of the Raman peaks due to heating or cooling results from both the intrinsic temperature dependence of the Raman spectrum of graphene and the strain on the graphene film due to the thermal expansion mismatch with silicon dioxide. By carefully comparing the experimental data against theoretical calculations, it is possible to determine the thermal expansion coefficient. The thermal conductivity is measured by estimating the thermal profile of a graphene film suspended over a circular hole of the substrate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.194-199
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• 2003

In this paper, elastic deformations of several gear teeth are analyzed. The contact between a gear and pinion is modeled as a contact problem. The deformation overlap, which is defined as the interference due to deformation of gear teeth, is defined to represent the deformation characteristics of profile shifted spur sear system. The calculated deformation overlap shows teeth interference in the deformed state of a Rear system.

• Journal of Biosystems Engineering
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• v.41 no.1
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• pp.1-11
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• 2016

Purpose: The gear strength of a new mechanical transmission designed to increase the loading weight of small 4.8 kW tracked agricultural transporters was analyzed. Design improvements to increase the gear strength and reduce the gear weight were proposed after examining the parameters. Methods: Sixteen operators from three regions were surveyed to obtain the usage profile of small 4.8 kW transporters. Gear strength was evaluated by calculating contact stress and tooth root stress using commercial software following ISO 6336. Results: From the strength calculation for each gear pair, contact stress smaller than tooth root stresses were produced in all gear pairs. The safety factors in most cases exceeded 1.0, except in the case of gear pair II in group II. The design life of the transporter using gear pair II in group II was 42% under harsh conditions-thus, this design life needs improvement. A robust design was proposed by examining the relevant parameters (face width and profile shift coefficient) to increase the design life of the transporter. In addition, a lightweight design for gear pair I in group II that was considered overdesigned was proposed by examining the face width to reduce the weight of the drive gear by 42% and that of the driven gear by 30%. Conclusions: The Safety factor for the design life was examined through a gear strength analysis. After examining the relevant parameters, conditions for strength improvement were proposed to increase design life or adjust overdesigned gear. However, load conditions differ depending on the working conditions or user's preferences; therefore, it is necessary to conduct further studies in various regions.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.5
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• pp.88-98
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• 1999

A refractive index modulated (RIM) DFB laser, in which the refractive index of a center region of the upper cladding layer comprising the grating region is different from that of side regions, is proposed to obtain and effective ${\lambda}$/4 phase shift in the center region. Since the coupling coefficient of a center region in a RIM-DFB laser is larger than that of side regions, a RIM-DFB laser has the effect of a distributed coupling coefficient. Simulation results show that RIM-DFB lasers have better operation characteristics - more uniform photon density profile, less SHB effect, and better single mode operation at high injection currents - compared to those of ${\lambda}$/4 phase-shifted DFB lasers and CPM-DFB lasers. In addition, the effect of the center region on the above threshold characteristics of a RIM-DFB laser is investigated.

• Korean Chemical Engineering Research
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• v.43 no.3
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• pp.360-365
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• 2005

SMB (simulated moving bed) is a continuous chromatographic process by shifting periodically port position. Binary of mixture, Blue dextran and Orange G, was separated by SMB. These components have unique color individually, that is, Blue dextran is blue and Orange G is orange. It is easy to understand SMB process by observing the shift of color changes in SMB. These components was not adsorbed to stationary phase and isolated by difference of size exclusion factor. Mass transfer coefficient was determined by single pulse test under several flow rate conditions. Operation condition was obtained by standing wave theory and optimized for high purities in extract and raffinate streams. Experiment was performed in open loop 4 zone (2-2-2-2) SMB. There are several advantages in open loop SMB, where extract is product for high purity. It is also easy to control flow rate and monitor experimental state during operation. Experimental, extract and raffinate history is well fitted with simulation results, however, column concentration profile is a little different from simulation results. Purities were 99.5％ for extract and 98.9％ for raffinate and extract and raffinate yields were obtained as 98.9％ and 99.4％ respectively.

• Korean Journal of Occupational Health Nursing
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• v.9 no.2
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• pp.94-109
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• 2000

The chances of disease pattern increased the importance of Health-promoting Lifestyle and a large part of the Health-promoting Lifestyle is associated with individual's habit. Health-promoting Lifestyle among nurses is very important because nurses could be a role model of patients and possibly influence many patients. The purpose of this study was oat on1y to assess how hospital nurses practice their Health-promoting Lifestyle but also to identify those affecting determinants. The subjects were 392 nurses working at 3 different hospital in Seoul. These data were collected by self administered questionnaire from April 27 to May 20, 2000. This study examined Health-promoting Lifestyle using In Sook Park's model, individual characteristics. Behavior-specific Cognitions and Affect factors using Pender's model and tried to fine out their relationships. The instruments used in this study were Health-promoting Lifestyle Profile developed by In Sock Park(1995). Likert's four-point scale was used also in this research. The percentage, mean standard deviation, AVNOVA, Pearson's correlation coefficient and multiple regression in the SAS package were used to analyze the data. The results of this study were as follows; 1. 52.3% of sample were aged between 25 and 29, 67.1% were single, 55.6% were university graduates, 51.8% earned 1.5 to 2.0 million won, 57.9% slept for d to 8 hours, 74.5% stated they were healthy. 2. 32.7% of sample worked in surgical gird department, 82.4% worked in 3 shift, 26.3% have been working as nurses for 5 to 7 years. Average score of Perceived self-efficacy was 3.63, Perceived benefits of action was 3.25, Social support was 2.75, and Perceived barriers to action was 1.87 which was the lowest score. 3. The average score if the performance in Health-promoting Lifestyle variable was 2.45 which was lower than previous study. The sanitary life Was 3.18 which was the highest score, harmonious relationship 3.13, emotional support 2.90. The variable with the highest degree of performance was the sanitary life, whereas the one with the west degree was the health diet. 4. There were no significant difference in perceived benefits of action with individual's a character, but in Perceived bait his of action there were significant differences with age(p<.01), marital status(p<.05), housing(p<.05), and Perceived health status(p<.05). In Perceived self-efficacy, there were significant differences with educational level(p<05), sleeping hours(p<.05), and BMI(p<.05). In Social support here were significant difference with housing and sleeping hours.