• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.2
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• pp.194-201
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• 2004

In the present study, the improvement of absorption characteristics on combined heat and mass transfer process in a falling film of a vertical absorber by change of geometric parameters were studied experimentally and analytically. The energy and diffusion equations are solved simultaneously to give the temperature and concentration variations at the liquid solution-refrigerant vapor interface and at the wall. Absorption behaviors of heat and mass transfer were analyzed through falling film of the LiBr aqueous solution contacted by refrigerant vapor in the absorber. Effects of film Reynolds number, geometric parameters by insert device (spring) and flow pattern on heat and mass transfer performances have been also investigated. Especially, effects of the flow pattern by geometric parameters have been considered to observe the total heat and mass transfer rates through falling film along the absorber. As a numerical and experimental result, maximum absorption rate was shown at the wave-flow by insert device (spring). The error ranges between experiment and analysis were from 5.8 to 12％ at Re$_{f}$ > 100.0.

• International Journal of Air-Conditioning and Refrigeration
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• v.14 no.2
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• pp.41-48
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• 2006

Absorption performance at the vertical interface between refrigerant vapor and liquid solution of $LiBr-H_{2}O$ solution was enhanced by the waves formed due to the interfacial shear stress. The present study investigated experimentally and analytically the improvements of absorption performance in a falling film by wavy film flow. The dynamic parameter was the film Reynolds numbers ranged from 50 to 150. The energy and diffusion equations were solved simultaneously to find the temperature and concentration profiles at the interface of liquid solution and refrigerant vapor. Absorption characteristics due to heat and mass transfer were analyzed for the falling film of the LiBr aqueous solution contacted by refrigerant vapor in the absorber. Absorption performance showed a peak value at the solution flow rate of $Re_{f}>100$. Absorption performance for the wavy film flow was found to be greater by approximately 10% than that for uniform film flow. Based on numerical and experimental results, the maximum absorption rate was obtained for the wavy flow caused by spring insert. The difference between the measured and the predicted results were ranged from 5.8 to 12%.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.289-293
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• 2010

To investigate the corrosion behavior of tools steel surface in various coating film, the surface of hard coated Ti-Zr-N film on the tool steel by using magnetron-sputtering methods was researched using various experimental methods. STD 61 steels were manufactured by using vacuum furnace and solutionized for 1hr at $1050^{\circ}C$. Steel surface was coated with Ti-Zr-N film at $150^{\circ}C$ and 100W for 1h by using DC-sputtering equipment. Surface characteristics of Ti-Zr-N film coated specimens were investigated by OM, XRD, FE-SEM and nano-scratch tester. And corrosion behaviors of the coated specimen were investigated by polarization test and electrochemical impedance spectroscopy(EG&G Co, PARSTAT 2273. USA). It was found that Ti-Zr-N film coated sample had a thick coated layer and showed a good wear resistance and corrosion resistance of surface compared with ZrN and TiN coated sample. The corrosion resistance and mechanical property of Ti-Zr-N film coated STD 61 alloy increased as sputtering time increased.

• Korean Journal of Materials Research
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• v.29 no.9
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• pp.547-552
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• 2019

In the present study, the thermal conductivity of a silicon nitride($Si_3N_4$) thin-film is evaluated using the dual-wavelength pump-probe technique. A 100-nm thick $Si_3N_4$ film is deposited on a silicon (100) wafer using the radio frequency plasma enhanced chemical vapor deposition technique and film structural characteristics are observed using the X-ray reflectivity technique. The film's thermal conductivity is measured using a pump-probe setup powered by a femtosecond laser system of which pump-beam wavelength is frequency-doubled using a beta barium borate crystal. A multilayer transient heat conduction equation is numerically solved to quantify the film property. A finite difference method based on the Crank-Nicolson scheme is employed for the computation so that the experimental data can be curve-fitted. Results show that the thermal conductivity value of the film is lower than that of its bulk status by an order of magnitude. This investigation offers an effective way to evaluate thermophysical properties of nanoscale ceramic and dielectric materials with high temporal and spatial resolutions.

• Journal of Korea Multimedia Society
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• v.21 no.10
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• pp.1211-1220
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• 2018

Maya Deren is well known as the 'mother' of the American avant-garde films by her first short, Meshes of the Afternoon (1943). One of the major contributions of Maya Deren's theoretical body of work to the visibility was the invention of a new vocabulary for independent film-making such as 'film-poems', and 'choreo-cinema'. To create experimental film forms, she chose poetry, dance, architecture and music as a metaphor to describe her images. On the top of these arts, Maya uses camera works and editing system to achieve an 'artificial reality' whose character is miraculous in that living whole, in order to help the audience to experience a protagonist's psychological journey.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.816-818
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• 1998

In this paper Polyimide(PI) thin film are fabricated by vapor deposition polymerization(VDP) of dry process which are easy to control the film's thickness and hard to pollute due to volatile solvent. The FT-IR spectrum show that PAA thin films fabricated by VDP are changed to PI thin film by thermal curing. From AFM(Atomic Force Microscopy) experimental as the higher curing temperature. the thin film thickness decreases and roughness decresse.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.686-689
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• 2003

Many technologies are applied to the measurement of elastohydrodynamic lubrication (EHL) film thickness. In particular, optical in-situ interferometric method has many advantages in making the actual contact behaviors realized with the experimental apparatus. Careful selection of incident lights greatly enhances the fringe resolution up to nanometer scale by using image processing technology. In this work, it is found that dichromatic incident light can provide much finer resolution of EHL film thickness than monochromatic incident light, because it has much more variables of color components to be discriminated among the wavelengths of colors according the variations of EHL film thickness. Some simulated interferometric images are shown how the film thickness is resolutionized in nanometer scale

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.4
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• pp.512-518
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• 2000

A wall fuel-film flow model is developed to predict the effect of a wall-fuel-film on air-fuel ratio in an SI engine in transient conditions. Fuel redistribution in the intake port resulting from charge backflow and a simple liquid fuel behavior in the cylinder are included in this model. Liquid fuel film flow is calculated of every crank angle degree using the instantaneous air flow rate. The model is validated by comparing the calculated results and corresponding engine experiment results of a commercial 4 cylinder DOHC engine. The predicted results match well with the experimental results. To maintain the constant air-fuel ratio during transient operation. the fuel injection rate control can be obtained from the simulation result.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.135-141
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• 2003

MEMS structures generally have been fabricated using surface-machining method, but the interface failure between silicon substrate and evaporated thin film frequently takes place due to the residual stress inducing by the applied the various loads. And the very important physical property in the heated environment is the linear coefficient of thermal expansion. Therefore this paper studied the residual stress caused the thermal loads in the thin film and introduced the simple method to measure the trend of the residual stress by the indentation. Specimens were made of materials such as Al, Au and Cu and thermal load was applied repeatedly. The residual stress was measured by nano-indentation using AFM and FEA. The existence of the residual stress due to thermal load was verified by the experimental results. The indentation length of the thermal loaded specimens increased minimum 11.8％ comparing with the virgin thin film caused by tensile residual stress. The finite element analysis results are similar to indentation test.

• Journal of the Korean Society for Heat Treatment
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• v.3 no.1
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• pp.17-24
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• 1990

In this study, TiN film was deposited onto steel by R.F.-PACVD in order to investigate the influence of parameters on the adhesion strength between film and substrate. Experimental results showed that adhesion strength by SAT is different from by optical microscopy. Adhesion strength is increased when the deposition temperature increases and is influenced by R.F. power and electrode distance. Especially heat treatment on the substrate has influenced over the adhesion strength, so it showed the 22 Newtons in adhesion strength by SAT and adhesion strength is decreased when deposition thickeness is thick and hardness is high. Also if the film is thick and high hardness simultaneous, the film was delaminated seriously.