• Proceedings of the Membrane Society of Korea Conference
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• 1998.04a
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• pp.56-58
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• 1998

1. 서론 : 무한한(unbounded) 용매 속에 떠 있는 구형입자의 확산계수는 Stokes-Einstein 식에 의해 주어지며, 이를 이용하여 입자의 반지름을 결정하기도 한다. 입자가 그 크기정도(order-of-magnitude)의 공간에 제한되는 경우에는 제한하는 벽이 입자의 운동에 많은 영향을 주게 된다. 이런 제한적 이동(hidered transport)은 막이나 크로마토그래피를 이용하는 분리공정이나 촉매를 이용하는 반응공정에서 이용되고 있다. (생략)

• Membrane Journal
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• v.21 no.3
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• pp.236-246
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• 2011

In this study, we used prepared a cylindrical module consisting 100 hollow fibers of commercialized (hydrophobic) polyethylene membrane of $0.4{\mu}m$ pore size and systematically studied performance of direct contact membrane distillation (DCMD) and sweep gas membrane distillation (SGMD) in terms of variation of permeate flux and salt rejection with respect to temperature drop across the membrane, salt concentrations in feed, and flow rates of cooling water and sweep gas. SGMD was regarded as DCMD with a sweep gas layer between permeate-side membrane surface and cooling water. Sweep gas flow decreases the permeate flux from that of DCMD by providing an additional gas-layer resistance. We compared DCMD and SGMD performance by using mass balance with a fitting parameter (${\omega}$), indicating fraction of permeate flow rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3625-3634
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• 2014

This study was conducted to provide the basic data for the prevention and management of health risk of dental technicians by proposing the necessary data in the management of the health related quality of life of dental technicians. The subjects of the survey were 141 dental technicians working in 30 dental technical laboratories and corresponding companies in Daejeon area. A structured self-entry type questionnaire survey was implemented by measuring the work environment from December 20, 2011 to January 31, 2012 at the same time. The total score of health index showed a significant difference according to the working hours and smoking state as the a factor of the individual level, the physical health index showed a significant difference according to the smoking state and the exercise habits as the factor of the individual level. The mental health index showed a significant difference according to the working hours and smoking state as the factor of the individual level. The significant variable did not appear in the predictor of the group level. In conclusion, the quality of life of dental technicians in relation to health appeared to have a larger effect on the factor of the individual level than the factor of the group level.

• FLOWER RESEARCH JOURNAL
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• v.16 no.3
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• pp.153-160
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• 2008

This experiment was conducted to find out an adequate shading level (0, 55, 74, and 95%) on the shoot growth of rooted cuttings of native Hydrangea serrata for. acuminata. New shoot height (NSH), length and width of leaf, and stem diameter under 55% shading were the greatest. Net photosynthetic rate under 55% shading was the greatest, while intercellular $CO_2$ concentration was the least in this treatment. The greatest content of photosynthetic pigments (total chlorophyll, carotenoid) was observed in leaves grown under a 74%, followed by a 55% shading level. Leaf stomata were observed on the abaxial surface, but those on adaxial surface in all shading treatments were not observed. In 95% shading, decreased stomatal density and development were observed. Higher stomatal density and development, however, were observed in 55% shading. Therefore, it is concluded that a 55% shading level was the optimum for growth of new shoots of rooted cuttings of native H. serrata for. acuminata.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.2
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• pp.173-178
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• 2018

The direct metal laser sintering (DMLS) technique would be promising for the full-arch implant-supported restorations due to reduced cost and manufacturing time without potential human errors and casting defects. The aims of this case report were to describe the successful outcome of an implant-supported fixed dental prosthesis in the edentulous maxilla by using the DMLS technology and computer-aided design and computer-aided manufacturing (CAD/CAM) monolithic zirconia crowns, and to describe its clinical implications. A healthy 51-year-old Korean woman visited Seoul National University Dental Hospital and she was in need of a rehabilitation of her entire maxilla due to severe tooth mobility. In this case, all maxillary teeth were extracted and an implant-supported fixed dental prosthesis was fabricated that involved a cobalt-chromium (Co-Cr) framework with the DMLS technique and CAD/CAM monolithic zirconia crowns. Six months after delivery, no distinct mechanical and biological complications were detected and the prosthesis exhibited satisfactory esthetics and function. In this case report, with the DMLS system, the three-dimensional printed prosthesis was created without additional manual tooling and thus, reliable accuracy and passive fit were obtained.

• Journal of Technologic Dentistry
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• v.37 no.4
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• pp.253-259
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• 2015

Purpose: The purpose of the study is to investigate the need for the retirement attitude of korean dental technicians. Retirement attitude is important in the study of retirement planning. Methods: A total of 778 dental technicians were selected by proportional stratified by region compared to extraction sampling from a list of korea dental technician association in 2012. The final sample size was 386. Questionnaires consisted of 10 questions general characteristics, 9 questions for the current life satisfaction and retirement preparation, and 4 questions about retirement attitudes on a Likert 5 scale. Cronbach's alpha was 0.812 in the study. All statistical analyzed were performed using SPSS 14.0(Statistical Packages for Social Science Ver. 14.0. Chicago, IL, USA). Results: An average of $3.01{\pm}0.8$ dental technicians were retirement attitude. To affect retirement attitude marital status, age, subjective health status, assets satisfaction, job type, job satisfaction and the economic outlook was living after retirement (p <0.05). Conclusion: This study suggested that retirement attitude of korean dental technicians was very important and the preparation must be connected with the social welfare policy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.11
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• pp.689-695
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• 2016

The performance of proton exchange membrane fuel cells (PEMFC) is strongly related to the water flow and accumulation in the gas diffusion layer (GDL) and catalyst layer. Understanding the behavior of fluid from the characteristics of the media is crucial for the improvement of the performance and design of the GDL. In this paper, a numerical method is proposed to calculate the design parameters of the GDL, i.e., permeability, tortuosity, and effective diffusivity. The fluid flow in a channel filled with randomly packed hard spheres is simulated to validate the method. The flow simulation was performed by lattice Boltzmann method with bounce back condition for the solid volume fraction in the porous media, with different values of porosities. Permeability, which affects the flow, was calculated from the average pressure drop and the velocity in the porous media. Tortuosity, calculated by the ratio the average path length of the randomly injected massless particles to the thickness of the porous media, and the resultant effective diffusivity were in good agreement with the theoretical model. The suggested method can be used to calculate the parameters of real GDL accurately without any modification.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.948-954
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• 2002

Porous reaction bonded SiC with high fracture strength was developed using Si melt infiltration method for use of the support layer in high temperature gas filter that is essential to develop the next generation power system such as integrated gasification combined cycle system. The porosity and pore size of porous RBSC developed in this study were in the range of 32∼36% and 37∼90 ${\mu}m$ respectively and the maximum fracture strength of porous RBSC fabricated was 120 MPa. The fracture strength and thermal shock resistance of porous RBSC fabricated by Si melt infiltration were much improved compared to those of commercially available porous clay bonded SiC due to the formation of the strong SiC/Si interface between SiC particles. The characteristics of pore structure of porous RBSC was varied depending on the amounts of residual Si as Well as the size of SiC particle used in green body.

• Journal of Technologic Dentistry
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• v.23 no.2
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• pp.75-93
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• 2002

This research was preformed for the purpose of preparing the items of standard model of the national dental technician test base on the duty analysis of the dental technician. The results of the duty analysis for the dental technician follows. 1. The dental technician is a profession to make the oral function smooth through the dental supplement and equipment in a scientific method and the skilled technique. 2. The duty of the dental technician are determined as A. preparation for manufacture B. manufacture C. management of the place of the dental technology D. self-development. A. The field of "the preparation for manufacture" are determined as 1. to confirm work authorization 2. To confirm the working model, B. The field of "In manufacture" are determined as 1. to manufacture the temporary crown 2. to manufacture the inlay and crown & bridge prosthesis 3. to manufacture the porcelain fused metal crown prosthesis 4. to manufacture the all ceramic crown prosthesis 5. to manufacture the temporary denture prosthesis 6. to manufacture the partial denture prosthesis 7. to manufacture the complete denture prosthesis 8. to manufacture the attachment prosthesis 9. to manufacture implant prosthesis 10. to manufacture the removable orthodontic device, 11. to manufacture the fixed orthodontic device, 12. to manufacture the orthodontic study cast C. The field of "in management of the dental lab." are determined as 1. management 2. to control the dental lab. D. The field of "In the self-development" are determined as 1. to improve the professionalism 2. self-control. 3. The developing items selected under the duty evaluation of the dental technician are l7s in the manufacture preparation, 1,011s in the manufacture, 7s in the management for the dental technology, 5s in self-development, and in all together 1,040s

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.6
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• pp.559-565
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• 2004

Two different methods were used for the scattering analysis of side-drilled holes(SDH). The scattering models include an explicit model based on the Kirchhoff approximation and the solution of the exact separation of variables. The far-field scattering amplitude was calculated and their time-domain results were compared for the case of shear vertical wave. The exact solution predicts the existence of the creeping wave. The Kirchhoff approximation agreed to the exact solution, except the case of the creeping wave. Two measurement models were introduced to predict the response from the SDHs for the case of immersion, pulse-echo testing. The received voltage was calculated for the case of the shear vertical waves with the incident angle of $45^{\circ}$ to the SDH with the diameter of 1mm, and compared with the experimental results.