• Korean Journal of Metals and Materials
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• v.46 no.6
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• pp.377-381
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• 2008

Prism sheet of LCD BLU which depends on supply from Japan and U.S.A was studied by using Si anisotropic etching and injection molding technologies. First, the prism sheet was patterned on Si wafer through photolithography, and the best conditions of Si etching were determined through etching Si wafer with TMAH to obtain straight optimized zigzag patterns, and a cross pattern to provide light diffusion and concurrent focusing. The etch rate of TMAH was concluded to be constant for $25wt%-70^{\circ}C$ condition. Ni stamp of prism sheet was made by electrodeposition using patterned Si wafer, normal or fast H/C(Heating/Cooling) injections were carried out to fabricate prism sheet. It was known that fast H/C injection could fabricate prism sheet more accurately than normal injection. Zigzag patterns and the cross pattern showed higher transmissivity than the straight patterns because of light diffusion through diagonal direction. The fast H/C injection for zigzag patterns showed lower transmissivity than normal injection because there occurred more light diffusion through precise injection patterns, but the fast H/C injection for straight patterns showed only refraction without diffusion, causing lower transmissivity than normal injection.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.267-273
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• 2018

Hydrothermal liquefaction of Chlorella vulgaris feedstock containing 80% (w/w) water was conducted in a batch reactor as a function of temperature (300, 325 and $350^{\circ}C$) and reaction times (5, 10 and 30 min). The biocrude yield, elemental composition and higher heating value obtained for various reaction conditions helped to predict the optimum conditions for maximizing energy recovery. To optimize the recovery of inorganic nutrients, we further investigated the effect of reaction conditions on the ammonium ($NH_4{^+}$), phosphate ($PO_4{^{3-}}$), nitrate ($NO_3{^-}$) and nitrite ($NO_2{^-}$) concentrations in the aqueous phase. A maximum energy recovery of 78% was obtained at $350^{\circ}C$ and 5 min, with a high energy density of 34.3 MJ/kg and lower contents of oxygen. For the recovery of inorganic nutrients, shorter reaction times achieved higher phosphorus recovery, with maximum recovery being 53% at $350^{\circ}C$ and 5 min. Our results indicate that the reaction condition of $350^{\circ}C$ for 5 min was optimal for maximizing energy recovery with improved quality, at the same time achieving a high phosphorus recovery.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.2
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• pp.93-100
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• 2011

This study deals with the high frequency induction hardening (HF at $850^{\circ}C$, 120kHz & 50kW condition) SM45C steel. (1) The HF specimen, which was tempered at $150^{\circ}C$, did not show any tempering effect. A brittle fracture occurred at rounded area of the tensile specimen. AE (acoustic emission) amplitude distribution showed between 45dB and 60dB. (2) A slip and fracture occurred at the hole area of the HF specimen which was tempered at $300^{\circ}C$. As they pass the yield point, the AE energy is increased intermittently and AE amplitude distribution exists between 70dB and 85dB. In addition, after imposing the maximum tensile load, AE signals showed high amplitude and energy distribution. The AE amplitude showed between 45dB and 70dB. (3) A brittle fracture occurred at HF specimen which was tempered at $450^{\circ}C$ as if it is torn in the direction of $45^{\circ}$ on parallel area over the both sides of the tensile specimen, which lead to several peak appeared in AE energy. It was found that the AE amplitude was relatively low and the AE energy was high.

• Journal of Korea Ship Safrty Technology Authority
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• s.33
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• pp.53-62
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• 2012

Pumps are used widely in feed water, cooling & heating system and process line of industrial and construction fields. They consume nearly 20% of the each nation's total electrical energy. But The management of pump energy wasn't controlled well. Their loss of energy is huge if they have been operated at low efficiency. The first buying cost of pump is small compare to the power consumption of pump, so we can recommend the suitable replace time and best operating condition of parts and pump to measure the pump efficiency. Pump efficiency is usually measured according to the two methods which they are called thermodynamic method and traditional technique. And we measured the pump efficiency using two methods using potable pump efficiency measurement device and compared the results with the real performance curve offered from pump maker.

• Journal of the Korea Safety Management & Science
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• v.19 no.4
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• pp.317-322
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• 2017

When the heat flux on the heating surface following changing heat condition in the boiling heat transfer system exceeds critical heat flux, the critical heat flux phenomenon is going over to immediately the film boiling area and then it is occurred the physical destruction phenomenon of various heat transfer systems. In order to maximize the safe operation and performance of the heat transfer system, it is essential to improve the CHF(Critical Heat Flux) of the system. Therefore, we have analysis the effect of improving CHF and characteristics of heat transfer following the nanoparticle coating thickness. As the results, copper nanocoating time are increased to CHF, and in case of nano-coatings are increased spray-deposited coating times more than in the fure water; copper nanopowder is increased up to 6.40%. The boiling heat transfer coefficients of the pure water are increased up to 5.79% respectively. Also, the contact angle is decreased and surface roughness is increased when nano-coating time is increasingly going up.

• Journal of the Korean Solar Energy Society
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• v.34 no.3
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• pp.49-56
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• 2014

A fiat-plate or vacuum tube solar collector have been mainly used for hot water supply of house because of some being difficult to get uniform energy density, so little applied into industrial field. This study is to apply the PTC(parabolic trough collector) solar collector into industrial field such as sludge dewatering system for energy reduction. The real scale system which composed of PTC Solar Collector and Thermal Dewatering (TDW) is established. PTC solar collector is designed to produce a hot water with $80^{\circ}C$ of temperature. And size of TDW is $630{\times}630mm$. Hot water produced from PTC solar collector is supplied into heating plate of TDW, and sludge like waterworks or wastewater is dewatered. PTC solar collector with $10m^2$ of area produce energy of average 5,618 kcal. As according to results from real scale performance, solar collector takes charge 94 % of the amount that TDW consume energy which is so large part if compare with boiler. It means that PTC solar collector is useful to apply industrial field under the condition of sufficient solar radiation. And it is analyzed that TDW by PTC solar collector has an economical validity.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.10
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• pp.969-976
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• 2004

Building energy saving is one of the most important issues in these days. Energy saving control strategies should be developed properly to achieve the saving. One of such area we could apply is the HVAC (Heating, Ventilation and Air-Conditioning) system. Through the optimal control algorithm for building energy management system (EMS), you can not only save the cost of building energy, but also protect HVAC system components against the unexpected condition. In order to verify the effectiveness of building energy saving, field test was accomplished for several months at 'A' building. And to get the measured data, remote control was used. If the remote control is used in BAS (Building Automation System), control and monitoring can be done for all of the building systems, such as HVAC, power, lighting, security and fire-alarm etc. anywhere any time. Using the remote control, Control and monitoring is possible for the testing system without going there. As the results of field test, we could reduce $5{\sim}10\%$ of the building energy cost.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.903-908
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• 2006

Building energy simulation has become a useful tool for predicting cooling, heating and air-conditioning loads for facilities. It is important to provide building energy performances feed back to the mechanical and electrical system operator and engineer for energy conservation and maintenance of building. From this research, we set up the typical weather data of location, basic description of building, geometric modelling data and the specification of Installed primary HVAC system for establishing the simulation model about energy consuming that take place in multipurpose building complex. The simulation tool of building energy - EnergyPlus (DOE and BLAST based simulation S/W), it has been used and accomplished calculations and analyses for evaluating the effect of the system types and operating condition of central HVAC plant on the building energy consumption. In this paper, we offer comparison and simultaneous results those involve electricity consumption pattern and amount between actual operation versus EnergyPlus simulation to the object building during summer season.

• Journal of Climate Change Research
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• v.8 no.2
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• pp.163-169
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• 2017

In this study, Non-$CO_2$ emission factors were estimated for the coal briquette boiler, which is the Korean heating system. As a result, the $CH_4$ and $N_2O$ emission factors of the coal briquette boiler were estimated to be $11.76gCH_4/TJ$ and $7.44kgN_2O/TJ$, respectively. The results showed that $CH_4$ emission factor was 12 times and $N_2O$ emission factor was 5 times higher than IPCC default value. Also the emission factors developed in this study were compared with a precedent study. The results indicated that were similar to open the air inlet of coal briquette stove because the combustion condition of this study was similar to that of coal briquette stove.

• Food Engineering Progress
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• v.15 no.3
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• pp.262-268
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• 2011

The effects of pellet moisture content on physical properties (expansion ratio, density and breaking strength) of vacuum-puffed Yukwa (non-oil puffed Yukwa) were investigated in this study. The Yukwa was made from the waxy rice steeped at 25 and $30^{\circ}C$ for 3, 5 and 10 days with pellet drying times (6, 8 and 10.5 hr). As the drying time increased from 6 to 10.5 hr at $50^{\circ}C$, the highest value of pellet moisture content (29.4%) was found in the samples made from the steeped waxy rice at $25^{\circ}C$ for 5 days after 6 hr drying, while the lowest value (16.3%) was found at $25^{\circ}C$ for 3 days after 10.5 hr drying. Both redness and yellowness values of vacuum-puffed Yukwa increased as the drying time increased. The expansion ratio of Yukwa was greatly affected by drying time, ranging from 2.07 (26.8% pellet moisture content) to 7.01 (24.0% pellet moisture content). From the data, it can be concluded that the pellet moisture content had a significant influence on the physical characteristics of vacuum-puffed Yukwa. With vacuum puffing condition of 3 min heating and 2 min puffing, the pellets with about 25% moisture content showed higher expansion ratio, and lower density and breaking strength.