• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.456-456
• /
• 2009

Boron doping on an n-type Si wafer is requisite process for IBC (Interdigitated Back Contact) solar cells. Fiber laser annealing is one of boron doping methods. For the boron doping, uniformly coated or deposited film is highly required. Plasma enhanced chemical vapor deposition (PECVD) method provides a uniform dopant film or layer which can facilitate doping. Because amorphous silicon layer absorption range for the wavelength of fiber laser does not match well for the direct annealing. In this study, to enhance thermal affection on the existing p-a-Si:H layer, a ${\mu}c$-Si:H intrinsic layer was deposited on the p-a-Si:H layer additionally by PECVD. To improve heat transfer rate to the amorphous silicon layer, and as heating both sides and protecting boron eliminating from the amorphous silicon layer. For p-a-Si:H layer with the ratio of $SiH_4$ : $B_2H_6$ : $H_2$ = 30 : 30 : 120, at $200^{\circ}C$, 50 W, 0.2 Torr for 30 minutes, and for ${\mu}c$-Si:H intrinsic layer, $SiH_4$ : $H_2$ = 10 : 300, at $200^{\circ}C$, 30 W, 0.5 Torr for 60 minutes, 2 cm $\times$ 2 cm size wafers were used. In consequence of comparing the results of lifetime measurement and sheet resistance relation, the laser condition set of 20 ~ 27 % of power, 150 ~ 160 kHz, 20 ~ 50 mm/s of marking speed, and $10\;{\sim}\;50 {\mu}m$ spacing with continuous wave mode of scanner lens showed the correlation between lifetime and sheet resistance as $100\;{\Omega}/sq$ and $11.8\;{\mu}s$ vs. $17\;{\Omega}/sq$ and $8.2\;{\mu}s$. Comparing to the singly deposited p-a-Si:H layer case, the additional ${\mu}c$-Si:H layer for doping resulted in no trade-offs, but showed slight improvement of both lifetime and sheet resistance, however sheet resistance might be confined by the additional intrinsic layer. This might come from the ineffective crystallization of amorphous silicon layer. For the additional layer case, lifetime and sheet resistance were measured as $84.8\;{\Omega}/sq$ and $11.09\;{\mu}s$ vs. $79.8\;{\Omega}/sq$ and $11.93\;{\mu}s$. The co-existence of $n^+$layeronthesamesurfaceandeliminating the laser damage should be taken into account for an IBC solar cell structure. Heavily doped uniform boron layer by fiber laser brings not only basic and essential conditions for the beginning step of IBC solar cell fabrication processes, but also the controllable doping concentration and depth that can be established according to the deposition conditions of layers.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.7 no.4
• /
• pp.665-672
• /
• 1997

We applied mechanical alloying process by ball milling to produce molybdenum silicides $MoSi_2$ and $Mo_5Si_3$ using a mixture of elemental molybdenum and silicon powders at room temperature. The intermetallic compound MoSi$_3$ have been obtained by ball milling of $Mo_{33}Si_{67}$ mixture powders for 100 h, which is transformed to single $MoSi_2$ phase by subsequent heat treatment up to $725^{\circ}C$. The grain size of the $MoSi_2$ powders thus obtained was 19 nm, being approximately four times smaller than that of the commercial alloy. The intermetallic compound $MoSi_2$ with grain size of 30 nm have been also obtained by ball milling of $Mo_{62}Si_{38}$ mixture powders for 500 h, which is transformed to single $MoSi_2$ phase by heating up to $1000^{\circ}C$. We believe that the retarded ball milling time for the formation of $MoSi_2$ phase is attributed to its complicated crystal structure and large unit cell. The finer grain size in the ball-milled molybdenum silicides powders is expected to improve room-temperature mechanical properties for high-temperature structural materials.

• Korean Journal of Construction Engineering and Management
• /
• v.13 no.3
• /
• pp.25-33
• /
• 2012

The purpose of this study is an analysis of importance and requirement factors in the aspect of facility manager for correctional facility. For this study, It limited ranges of study in 11 correctional facilities that have been completed after 2000 years. It had survey and interview with managers of correctional facilities that are selected for study and then it derived the requirement factors of correctional facilities. Based on those requirement factors, Importance analysis is performed by using AHP method. The result of this study are as follows: 1) The fields are divided into architecture, building finishing, machinery, electricity fields and it derives details of each field. 2) The results of importance on requirements of managers in correctional facilities are as follows. Planing of building arrangement (10.9%) in architecture, secure plan for soundproof partition (14.1%) in building finishing, isolation lining of heating and cooling system(11.9%) in machinery, and improvement of control system(12.2%) in electricity.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.36 no.11
• /
• pp.1444-1450
• /
• 2007

To prevent the deterioration of jujube wine quality due to commercial heating process for sterilization, hydrostatic pressure (500 MPa, 5 min) or freezing (frozen at $-20^{\circ}C$ for 3 days, followed by thawing at room temperature for 4 hr) treatment was applied. Their microbial count, physicochemical property and sensory quality were investigated in comparison to heat-treated jujube wine ($63^{\circ}C$, 10 min) and commercial wine. Pressure-treated and commercial jujube wine were completely sterilized and heat-treated wine was decreased to <10 CFU/mL while freezing-treated jujube wine was partially sterilized $(30{\sim}60%)$. Hydrostatic pressure and freezing, and heat treatment had no influence on chemical compositions such as pH, acidity, amino acidity, reducing sugar and ethanol content, but significantly induced the changes of instrumental color. While sensory quality of heat-treated jujube wine was significantly deteriorated, reducing sour and burning taste, that of pressure and freezing-treated jujube wine was maintained fresh without decrease in sour and burning taste.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.1
• /
• pp.19-26
• /
• 2010

A PEMFC(proton exchange membrane fuel cell) is a good candidate for residential power generation to be coped with the shortage of fossil fuel and green house gas emission. The attractive benefit of the PEMFC is to produce electric power as well as hot water for home usage. The thermal management of PEMFC for RPG is to utilize the heat of PEMFC so that the PEMFC can be operated at its optimal efficiency. In this study, thermal management system of PEMFC stack is modeled to understand the dynamic response during load change. The thermal management system of PEMFC for RPGFC is composed of two cooling circuits, one for controling the fuel cell temperature and the other for heating up the water for home usage. The different operating strategy is applied for each cooling circuit considering the duty of those two circuits. Even though the capacity of PEMFC system (1kW) is enough to supply hot domestic water for residence, heat-up of reservior takes some hours. Therefore, in this study, time schedule of the simulation reflects the heat-up process. Dynamic responses and operating strategies of the PEMFC system are investigated during load changes.

• Journal of Energy Engineering
• /
• v.8 no.2
• /
• pp.224-232
• /
• 1999

Latent heat storage system using micro-encapsuled phase change material is effective method for floor heating of house and building. The temperature profile in capsule block and flow rate of hot water are important parameters for the development of heat storage system. In the present study, a mathematical model based on 3-D, non-steady state, Navier-Stokes equations, scalar conservation equations and turbulence model ($\kappa$-$\varepsilon$), is used to predict the temperature profiles in capsule and the velocity vectors in hot water pipe. The multi-block grids and fine grids embedding are used to join the circle in hot water pipe and square in capsule block. The phase change process of the capsule is quite complex not only because the size of phase change material is very small, but also because phase change material is mixed with the cement to form thermal storage block. In calculation, it's assumed that the phenomena of phase change is limited only the thermal properties of phase change material and the change of boundary is not happened in capsule. The purpose of this study is to calculate the temperature profiles in capsule block and velocity vectors in hot water pipe using the numerical calculation. Two kinds of thermal boundary condition were considered, the first (case 1) is the adiabatic condition for the both outside surfaces of the wall, the second (case 2) is the case in which one surface is natural convection with atmosphere and another surface is adaibatic. Calculation results are shown that the temperature profile in capsule block for case 1 is higher than that for case 2 due to less heat loss in adaibatic surface. Specially, in the domain of near Y=0, the difference of temperature is greater in case 1 than in case 2. The detailed experimental data of capsule block on the temperature profile and the thermal properties such as specific heat and coefficient of heat transfer with the various temperature are required to predict more exact phenomena of heat transfer.

• The Korean Journal of Food And Nutrition
• /
• v.19 no.1
• /
• pp.22-27
• /
• 2006

This study was carried out to determine the optimum conditions for making soybean curd(or tofu) from defatted soybean flour.. Heating soymilk above $80^{\circ}C$ for at least $5{\sim}10\;min$ was necessary for soybean protein to form aggregates during subsequent coagulation process with glucono-${\delta}$-lactone(GDL). For maximum yield of tofu, with water content of approximately 80%, extra addition of 20 g of oil and 5 g of GDL per 425 g of soybean flour was needed. Maintaining soymilk temperature around $75^{\circ}C$ for 5 min was necessary when GDL was used as the coagulant.

• Korean Journal of Food Science and Technology
• /
• v.33 no.4
• /
• pp.461-468
• /
• 2001

The effectiveness and safety of Enzyme Food, a group of dietary supplements designated by Korean Food Law, were evaluated and the possibility of HACCP (Hazard Analysis Critical Control Point) application was investigated. Chemical composition, enzyme activities and the degree of bacterial contamination in 12 samples of different brands sold in Korean market were measured. The chemical composition of the selected products varied and inconsistent to those claimed in the label description. It is known that effectiveness of Enzyme Food depends on enzyme activity, but enzyme activities of ${\alpha}-amylase$ varied from $1,793\;{\mu}g/min$ g to $159\;{\mu}g/min$ g and those of ${\beta}-amylase$ ranged from $171\;{\mu}g/min$ g to $11\;{\mu}g/min$ g. The protease activities varied from $27.57\;{\mu}g/min$ g to $0.18\;{\mu}g/min$ g. In coli-form bacterial test, positive reactions were appeared in the 50 % of the samples. Numbers of bacteria ranged from $1.3\;{\times}\;10^5\;to\;1.2\;{\times}\;10^9$. Five CCPs were identified; heating, inoculation, cultivation, drying and granulation. Consideration of HACCP system indicated that the pretreatment of raw material, checking of bacterial contamination and stability of enzyme activity during fermentation process were important factors for the quality of Enzyme Foods.

• Journal of the Korean Society of Radiology
• /
• v.4 no.4
• /
• pp.5-10
• /
• 2010

The $Ca_2SiO_4$ phosphors doped by La with 0.1 wt%, 0.3 wt%, 0.5 wt%, and 1.0 wt% concentration were prepared by sintering at $1000^{\circ}C$ for 90 minutes in N2 atmosphere. The phosphors were ground in powdered form and were grouped in $100{\mu}m$ size, then the samples had been exposed to low energy X-ray and UV light. The TL glow curves were measured by heating the phosphors at $10^{\circ}C/s$ rate. There was no significantly meaningful correlation between the TL intensity and the doping level. The intensities of the TL peak measured from X-ray irradiated samples doped with 0.1 wt% were relatively strong. The activation energy and the frequency factor were 0.434 ~ 0.516 eV and 0.5 ~ 0.56, respectively. The intensities of the TL peak measured from UV irradiated samples doped with 0.3 wt% were relatively strong. The activation energy and frequency factor were 0.415 ~ 0.477 eV and 0.5 ~ 0.53, respectively. The TL process were found to be the 2nd order for both X-ray and UV irradiation. The TL intensity was increased linearly with the increase of the radiation dose. In summary, the $Ca_2SiO_4 phosphors developed in this study showed good TL characteristics at low energy X-ray and UV light. We believe they will be used as TLDs in near future for personal and environmental radiation detection dosimetry.

• Journal of Soil and Groundwater Environment
• /
• v.17 no.2
• /
• pp.54-61
• /
• 2012

In this study, the adsorption of $Cu^{2+}$ from aqueous solution by the biochar derived from woody biomass at different pyrolysis temperatures has been investigated. The woody biomass wastes used in this study were branch of willow ($Salix$ $koreensis$ $Andersson$) and bark of chestnut ($Castanea$ $crenata$ $var.$ $dulcis$). Three biochar samples prepared by heating each biomass at temperature of $300^{\circ}C$, $500^{\circ}C$, and $700^{\circ}C$were tested for the adsorption capacity of Cu. Also the physicochemical properties of the developed biochars were studied using different characterization techniques such as FT-IR, SEM, BET surface area, and cation exchange capacity (CEC). The adsorption of Cu could be well described by Langmuir model for both willow and chestnut biochars with $R^2{\geq}0.98$. The maximum adsorption capacities of the biochar produced at $700^{\circ}C$ from the Langmuir equation were found to be 12.5 mg $g^{-1}$ and 16.9 mg $g^{-1}$ for willow and chestnut, respectively. Chestnut biochar was found to interact more effectively with the active sites available for Cu, resulting higher removal of Cu(II) than wiloow biochar. Ion exchange and surface complexation found to be the main mechanisms involved in the adsorption process. This study demonstrated the feasibility of the biochars derived from woody biomass to be as a low-cost potential adsorbent for heavy metals as Cu(II) removal in aquatic system.