• Composites Research
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• 제25권5호
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• pp.154-158
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• 2012

복합시트의 구조를 변화시켜 흡 차음성에 미치는 영향을 연구하였다. 폴리프로필렌 보드의 표면과 배면에 폴리에틸렌테레프탈레이트 부직포를 핫 프레스로 융착하여 복합시트를 제조하였다. 면밀도가 $0.64kg/m^2$인 부직포를 사용하여 제조한 복합시트의 흡음률은 0.1-0.2의 값을 나타내어 폴리프로필렌 보드의 흡음률에 비해 약 100~400%의 증가를 나타내었다. 폴리프로필렌 보드의 면밀도를 증가시키거나 복합시트 위에 반구형의 홈을 포함하는 경우에 복합시트의 투과손실이 증가하였다. 평판 복합시트와 사인 파형을 가지는 복합시트의 구조를 변화시켜 만든 2가지 복합시트 구조에 따른 흡음률과 차음도의 변화를 조사하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2004년도 학술대회지
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• pp.1-6
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• 2004

We ensure a flat and regular basic surface by using part of joint waterproofing improved sheet method applying the upper slab of a concrete structure. We solve the problem of getting loose scale the general sheet by waterproofing of the sheet and improving adhesive strength of the basic concrete. Also, waterproofing sheet union to problem of joint have solved using of insertion type method so that, it improved a watertightness. It has improved in resist impact, resist abrasion and it is the effect of shortened construction period and cutting down on construction expenses. Here are the special quality and superiority of this waterproofing research. (1) Level material has the super adhesive strength so that it makes the basic surface without the gab of waterproofing sheet and waterproofing layer with the string adhesive strength. (2) We unite the sheet with the joining part between sheets by waterproofing sheet joint using of method. (3) There is the effect of shortened construction period and cutting down on construction expenses without waterproofing of protection.

• 소성∙가공
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• 제19권4호
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• pp.236-241
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• 2010

The frictional behavior of bare steel sheet highly depends on surface roughness. It was investigated that the change of surface roughness of bare steel sheet due to deformation for each forming mode. The flat type friction test was done to check the effect of surface roughness change on frictional characteristics of bare steel sheet. As increasing the deformation, the Ra value was increased at stretching forming mode and drawing forming mode, however the change of Pc showed different trends. The Pc was decreased as increasing stretch deformation but increased at compression deformation. At drawing forming mode, the friction coefficient was increased as deformation was increased after initial big drop with drawing oil. As deformation was increased, the friction coefficient was decreased with drawing oil at stretching forming mode. The results show that the deformation changes the surface roughness and frictional characteristics of steel sheet but the effect depends on the forming mode.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권5호
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• pp.289-294
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• 2002

Cellulose production by Acetobacter pasteurianus was investigated in static culture using four bioreactors with silicone rubber membrane submerged in the medium. The shape of the membrane was flat sheet, flat sack, tube and cylindrical balloon. Production rate of cellulose as well as its yield on consumed glucose by the bacteria grown on the flat type membranes was approximately ten-fold greater than those on the non-flat ones in spite of the same membrane thickness. The membrane reactor using flat sacks of silicone rubber membrane as support of bacterial pellicle can supply greater ratio of surface to volume than a conventional liquid surface culture and is promising for industrial production of bacterial cellulose in large scale.

• 한국항만학회지
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• 제10권1호
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• pp.53-61
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• 1996

This paper describes the effect of wave control using submerged flat plate by the numerical calculation and the hydraulic model test. The boundary element method is used to develop a numerical solution for the flow field caused by monochromatic oblique waves incident upon an infinitely long, sumerged flat plate situated in arbitrary water depth. The effect of wave blocking is examined according to the change of length, submerged depth of flat plate and incident angles. Numerical results show that longer length, shallower submergence of flat plate and larger incident angles enhance the effect of wave blocking. To validate numerical analysis method, hydraulic model test was conducted in 2-D wave flume with 60 cm metal sheet. Reflected waves are extracted from water surface elevation in front of the location of a submerged plate by least square method with 3 wave gages. From comparing experimental results with numerical results, efficiency of numerical analysis method by this study could be confirmed well within wide ranges of wave frequencies.

• Membrane and Water Treatment
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• 제12권2호
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• pp.59-64
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• 2021

The rejection of sodium chloride (NaCl) and calcium chloride (CaCl2) single salt solutions were carried out for commercial nanofiltration NFDK membrane. Results showed that the NFDK membrane had a negative surface charge and had a higher observed rejection of 93.65% for calcium (Ca2+) ion and 78.27% for sodium (Na+) ions. Prediction of rejection for aqueous solutions of both salts was made using Donnan Steric Pore Model based on Extended Nernst-Planck Equation in addition to concentration polarization film theory. A MATLAB program was developed to execute the model calculations. Absolute Average Relative Error (% AARE) was found below 5% for real rejection of the NFDK membrane. This research could be used successfully to assess the membrane characterization parameter using a proposed procedure which can reduce the number of experiments.

• 청정기술
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• 제22권3호
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• pp.203-207
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• 2016

Here, we report a novel fabrication technique for patchable organic lasing sheet based on non-volatile liquid organic semiconductors and freestanding polymeric film with high flexibility and patchability. For this work, we have fabricated the second-order DFB grating structure, which leads to surface emission, embedded in the freestanding polymeric film. Using an ultra-violet (UV) curable polyurethaneacrylate (PUA) mixture, the periodic DFB grating structure can be easily prepared on the freestanding polymeric film via a simple UV curing process. Due to unsaturated acrylate remained in the PUA mixture after UV curing, the freestanding PUA film provides adhesive properties, which enable mounting of the patchable organic lasing sheet onto non-flat surfaces with conformal contact. To achieve laser actions in the freestanding resonator structure, a composite material of liquid 9-(2-ethylhexyl)carbazole (EHCz) and organic laser dyes was used as the laser medium. Since the degraded active materials can be easily refreshed by a simple injection of the liquid composite, such a non-volatile liquid organic semiconducting medium has degradation-free and recyclable characteristics in addition to other strong advantages including tunable optoelectronic responses, solvent-free processing, and ultimate mechanical flexibility and uniformity. Lasing properties of the patchable organic lasing sheet were also investigated after mounting onto non-flat surfaces, showing a mechanical tunability of laser emission under variable surface curvature. It is anticipated that these results will be applied to the development of various patchable optoelectronic applications for light-emitting displays, sensors and data communications.

• 대한기계학회논문집
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• 제17권9호
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• pp.2242-2251
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• 1993

The mesh-based frictional contact model has been developed which does not rely on the spatial derivatives of the tool surface. Only points on the surface are evaluated from the description. which can then be simplified because of the relaxed demands placed on it. The surface tangents, normals, and corresponding derivatives at each finite-element node are evaluated directly from the finite-element mesh, in terms of the connecting nodal positions. The advantages accrue because there is no longer a need for a smooth tool surface to assure reasonable normals and derivatives. Furthermore, it can be shown that the equilibrium equations can only be properly written with a special normal derived from the mesh itself. The validity, accuracy, computation time, and stability of mesh-based contact model were discussed with the numerical examples of rounded flat-top and rough, flat-top rounded punch forming operations. Also, the forming process of a automobile inner panel section was simulated for testing the robustness of new contact model. In the discussion, the superiority of new model was examined, comparing with tool-based contact one.

• 대한기계학회논문집A
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• 제20권2호
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• pp.488-499
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• 1996

SMC(Sheet molding compound) is a thermosetting material reinforced with chopped fiberglass. The compression molding of SMC was analyzed based on a rigid thermo-viscoplastic approach using a three dimensional finite element program coupled with temperatures. Only the temperature analysis part was tested in this paper by solving one-dimensional heat transfer problem and comparing with the exact solutions available in the literature. Based on this comparison the program was proved to be valid and was further applied in solving compression molding of SMC between flat dies. To investigate the usefulness of a rigid thermo-viscoplastic approach in the compression molding analysis of SMC charge, compression of rectangular shaped SMC charge at plane strain and three dimensionalde formation condition was analyzed under the same condition as given in the literature. From this comparison it was found out that the rigid thermo-viscoplastic approach was useful in analyzing SMC compression molding between flat dies.

• 대한기계학회논문집B
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• 제25권1호
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• pp.71-77
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• 2001

A flow visualization study using the oil film method and the smoke-laser light sheet arrangement is carried out to investigate the three-dimensional flow pattern around the free end surface region of a finite circular cylinder (aspect ratios of 1.25 and 4.25) mounted on a flat plate. The experiment is performed for the cases of two Reynolds numbers: 5.92${\times}$10$^3$and 1.48${\times}$10(sup)5. Various kinds of singular points on the free-end surface are disclosed from the oil surface flow visualization. The smoke-laser light sheet visualization, to aid in understanding the oil streak-line patterns, clearly demonstrates that a pair of tornado-like vortices marched along the downstream together with a pair of side tip vortices. A topological sketch to characterize the surface flow and the four vortices emanating from the top surface is included.