• Korean Journal of Materials Research
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• v.2 no.3
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• pp.180-190
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• 1992

Some solutions to several major problems in ZMR such as agglomeration of polysilicon, slips and local substrate melting are described. Experiments are performed with varying polysilicon thickness and capping oxide thickness. The aggmeration can be eliminated when nitrogen is introduced at the capping oxide layer-to-polysilicon interface and polysilicon-to-buried oxide layer interface by annealing the SOI samples at $1100^{\circ}$ in $NH_3$ ambient for three hours. The slips and local substrate melting are removed when the back surface of silicon substrate is sandblasted to produce the back surface roughness of about $20{\mu}m$. The subboundary spacing increases with increasing polysilicon thickness and the uniformity of recrystallized SOI film thickness improves with increasing capping oxide thickness, improving the quality of recrystallized SOI film. When the polysilicon thickness is about $1.0{\mu}m$ and the capping oxide thickness is $2.5{\mu}m$, the thickness variation of the recrystallized SOI film is about ${\pm}200{\AA}$ and the subboundary spacing is about $70-120{\mu}m$.

• Transactions of the Korean hydrogen and new energy society
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• v.11 no.3
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• pp.119-125
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• 2000

To improve the photochemical energy conversion efficiency and the stability of CdS particulate film electrode which is used to produce hydrogen from the aqueous $H_2S$ solution photoelectrochemically, surface treatment of this film was carried out using $TiCl_4$ solution. CdS particles for preparation of the films were synthesized by precipitation reaction of $Cd({NO_3})_2{\cdot}9H_2O$ and $Na_2S{\cdot}4H_2O$. Then, the CdS sol was hydrothermally treated for 12hr in an autoclave with the variation of treatment temperature to control the crystalline phase of particles. CdS film electrode was thus prepared by annealing at $400^{\circ}C$ for 12hr of the wet-film cast at room temperature, and subsequently surface treated with $TiCl_4$ solution. The electrodes were characterized using XRD, SEM, and the photocurrent meter. The photocurrents of Cds film electrodes prepared with surface treatment were up to two times higher than the electrodes without surface treatment, indicating about $4.0mA/cm^2$. Hydrogen production rate in a continuous flow system using photoelectrochemical or photochemical cells prepared with surface treatment also increased in proportion to the increase of photocurrents.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.486-491
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• 2008

This paper describes a model identification method that has been applied to a commercial 12-inch RTP (rapid thermal processing) equipment with an ultimate aim to develop a high-performance advanced controller. Seven thermocouples are attached on the wafer surface and twelve tungsten-halogen lamp groups are used to heat up the wafer. To obtain a MIMO balanced state space model, multiple SIMO (single-input multiple-output) identification with highorder ARX models have been conducted and the resulting models have been combined, transformed and reduced to a MIMO balanced state space model through a balanced truncation technique. The identification experiments were designed to minimize the wafer warpage and an output linearization block has been proposed for compensation of the nonlinearity from the radiation-dominant heat transfer. As a result from the identification at around 600, 700, and $800^{\circ}C$, respectively, it was found that $y=T(K)^2$ and the state dimension of 80-100 are most desirable. With this choice the root-mean-square value of the one-step-ahead temperature prediction error was found to be in the range of 0.125-0.135 K.

• KDI Journal of Economic Policy
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• v.35 no.4
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• pp.31-61
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• 2013

The purpose of this study is to calculate the economic value of transport demand forecasting risks in the road PPP project. Under the assumption that volatility of the road PPP project value occurs only in regard with uncertainty of traffic volume forecasting, this study calculates the economic value of the traffic forecasting risks in the case of the road PPP project. To that end, forecasted traffic volume is assumed to be a stochastic variable and to follow the Geometric Brownian motion as time passes. In particular, this study attempts to differentiate itself from existing studies that simply use an arbitrary assumption by presenting the application of different traffic volume growth volatility and the rates before and after the ramp-up period. Analysis of the case projects reveals that the risk premium related to traffic volume forecast of the project turns out as 7.39~8.30%, without considering option value-such as minimum revenue guarantee-while the project value volatility caused by transport demand forecasting risks is 17.11%. As the discount rate grows higher, the project value volatility tends to decrease and volatility in project value is always suggested to be larger than that in transport volume influenced by leverage effect due to fixed expenditure. The market value of transport demand forecasting risk-calculated using the project value volatility and risk premium-is analyzed to be between 0.42~0.50, implying that a 1% increase or decrease in the transport amount volatility would lead to a 0.42~0.50% increase or decrease in risk premium of the project.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.4
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• pp.39-47
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• 1982

Geotextile effects as reinforcement and vertical drain materials are studied through the laboratory model embankments on weak clays. The experiments are carried out in four stages; no woven fabrics between clay-crushed stone boundary, fabrics between boundary with no initial pretensioning of fabrics, and fabrics between boundary with two different initial pretensionings of fabrics. In all stages, vertical drains utilizing non-woven fabrics are installed in the clay layer in square pattern to accelarate the consolidation. The experimental model has plane dimensions of $32cm{\times}330cm$. The height for the clay container is 60 cm. The 47 cm height of crushed stone embankment is constructed over the 50 cm deep clay layer. The time dependent pore pressures are measured utilizing the 8 piezometers installed symmetrically on both sides of the wall at different heights. The time dependent deformations are measured utilizing the LED indicating lamp matrix inserted in the crushed stone embankment and the dialgauges put on top of the clay layer where the crushed stones are not laid. The measurements are carried out for 10 days which is equivalent to the time required for the primary consolidation. Through the experimental study, an analytical procedure is developed to predict the time dependent embankment settlement even if the top of the clay layer is reinforced with woven fabrics. This can be done through measuring the maximum pore pressures developed in the clay layer and comparing with the theoretical maximum pore pressures when no reinforcing fabrics are employed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.65-72
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• 2011

When an expressway intersects another expressway, a unique connector needs to be designed between the two consecutive exit ramps. In such a case, it is important to design a connector such that there is enough distance for drivers to find their way safely. A current design manual in Korea prescribes the minimum length of the connector as 240 m. In this research, we have suggested a method for calculating the minimum length of a connector in order to check the feasibility of the currently prescribed length. For this purpose, we have attempted to determine the total perception-reaction time and lane-changing time required by a driver. For determining the driver's perception-reaction time, we have used the driver's decision time in addition to the conventional 2.5 s of perception-reaction time for stopping sight distances. We have considered both the design speed and the average travel speed for the calculation of the length. To evaluate the accuracy of the new method, we have chosen four sites on expressways for which relatively high accident rates were recorded. As a result, we could verify that the current limit (240 m) was sufficient for drivers to be able to change lanes in the given specific geometry. However, the prescribed limit should be revised in case the drivers' decision time is considered to be their perception-reaction time. All new approaches for calculating the ideal length of a connector have been carried out by taking into account the design speed as well as the average travel speed. Owing to the characteristics of the specific geometry for two consecutive exit ramps and the large difference between the design speed and the average travel speed in the objective areas, it is more realistic to use the proposed method by keeping the decision time equal to a driver's perception-reaction time, in order to determine the ideal distance that should be maintained between two consecutive exit ramps.

• Applied Chemistry for Engineering
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• v.28 no.3
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• pp.318-325
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• 2017

Wastewater including ethanolamine used in the second generation of nuclear power plants is filtered out in the ion exchange resin of the condensate polishing plant. In the regeneration process of ion exchange resin, a strong acidic wastewater containing ethanolamine and a lager amount of ionic substances are released. In this study, the process involving UV oxidation part with or without absorbents was developed for treating wastewater released from the ionic exchange resin. The effect of adsorbents on the wastewater treatment was investigated by using UV oxidation system developed by us. As a result, the COD removal efficiency of UV/GAC process with the granular activated carbon (GAC) as an adsorbent was 71.3% at pH 12.8. The removal efficiency was 21.8% higher than that of the wastewater treated using UV oxidation process without any adsorbents at the same condition. The removal of T-N was 88.6% at pH 12.8 when using UV oxidation with the GAC absorbent, which was 18.0% higher than that of using the UV oxidation process without any absorbents. It is thought that ethanolamine adsorbed on the absorbent improved the efficiency of UV oxidation process. Therefore, the UV/GAC adsorption oxidation process can be more effective in treating wastewater containing ethanolamine than that of using the process without any absorbents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.117-124
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• 2017

A Smart Grid is a system that can efficiently use energy by exchanging real-time information in both directions between a consumer and a power supplier using ICT technology on an existing power network. DR(Demand response) is an arrangement in which electricity users can sell the electricity they save to the electricity market when the price of electricity is high or the power system is crisis. In this study, we developed a power meter data transmission device and power IT system that measure the demand information in real-time using a smart meter and transmit it to a cloud server. The power meter data transmission device developed in this study uses alight sensor connected to a Raspberry Pi 3 to measure the number of blinking lamps on the KEPCO meter per unit of power, in order to provide reliable data without any measurement errors with respect to the KEPCO power data. The power measurement data transmission device uses the standard communication protocol, OpenADR 2.0b. The measured data is transmitted to the power IT system, which consists of the VEN, VTN, and calculation program, via the LTE WiFi communication network and stored in its MySQL DB. The developed power measurement data transmission device issues a power supply instruction and performs a peak reduction DR when a power system crisis occurs. The developed power meter data transmission device has the advantage of allowing the user to adjust it every 1 minute, where as the existing smart metering time is fixed at once every 15 minutes.

• Journal of Advanced Navigation Technology
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• v.18 no.1
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• pp.35-43
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• 2014

In this paper, it is about to non-contact wireless power transmission according to various conditions of self induction principle between the two planar coils at a transmission unit and a receiving unit based on the theory of wireless power transmission. The experiments are occurred in order to power transfer of noncontact method from designed wireless circuits in the primely coil and secondary coil, and the applying to Half Bridge Resonant converter transmission unit and receiving unit. and that were able to prepared circumstance to calculate of the output voltage and power source. The main power of the inductive coupling the resonant converter at the transmission unit is converted electrical energy using the solar cell module and artificial light source (halogen lamp) as a replace light and received 24 V power supply from solar power was used a input power source for the wireless power transmission device. Experimental results, to received of power is used to illuminate the lighting and to charge the battery in receiving circuit.And the wireless power transmission efficiency measured at the output side of the transmission unit is obtained about 70% to 89% compared to input power of receiving unit.In addition, efficiency were tested through ID verification method and comparing the phase difference between the voltage when foreign substances interfere with wireless power transmission.

• KSBB Journal
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• v.20 no.6
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• pp.413-417
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• 2005

The purple sulfur phototrophic bacterium, Thiocapsa roseopersicina NCIB 8347 has been studied on hydrogen production and cell growth under different culture conditions, such as light source, light intensity, and growth temperature. T. roseopersicina showed maximum cell growth of 1.38 and 1.42 g-DCW/L under 7.5-10 klux of halogen and fluorescent light, respectively, and produced maximum amount of hydrogen with values of 0.90 and 0.48 $mL-H_2/mg$-DCW under the irradiation of 10 klux of halogen and fluorescent light, respectively. The optimum growth temperature for hydrogen production was $26^{\circ}C$, and hydrogen production rate was lowered over $30^{\circ}C$. When T. roseopersicina was grown photoheterotrophically under irradiation of 8-9 klux of halogen lamp, the generation time was 4.2 hr. The strains started producing hydrgen from the middle of the logarithmic growth phase and continued until succinate concentration leveled out.