• Clean Technology
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• v.20 no.1
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• pp.13-21
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• 2014

Because of the water scarcity caused by the increase of salinity in the underground water, seawater desalination stands out as one of the most promising solution. As there are so much energy costs in operating desalination plants, new hybrid process which is more effective should be researched. A geothermal VMD (vacuum membrane distillation) hybrid process is a competitive alternative for seawater desalination. Because geothermal energy has significant characteristics of high capacity factor to operate the power plant at full capacity for 24 hour per day, it can be a priority heat source of VMD superior to any other renewable energies such as solar and wind power. In this study, we design a geothermal VMD hybrid process, analyze it economically and finally compare the result with a case of conventional VMD process. Geothermal VMD hybrid process generates $23,822,409 of NPV (net present value) more than the conventional VMD process in case of 5% discount rate. The break-even point between these processes is 5.36 year. Sensitivity analysis indicates that steam cost is the most decisive influence variable to the economic outcome.

• Journal of the Korean Magnetics Society
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• v.17 no.4
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• pp.172-177
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• 2007

In order to detect of the magnetic property in the cell unit, we studied the GMR-SV (giant magnetoresistance-spin valves) biosensor, which was depended on the micro patterned features according to two easy directions of longitudinal and transversal axes. Here, the multi layer structure was glass/NiO/NiFe/CoFe/Cu/CoFe/NiFe. The uniaxial anisotropy direction was applied to the patterned biosensor during the deposition and vacuum post-annealing at $200^{\circ}C$ under the magnitude of 300 Oe, respectively. Considering the magnetic shape anisotropy effect, the size of micro patterned biosensor was a $2{\times}5{\mu}m^2$ after the photo lithography process. By our experimental results, we confirmed that the best condition of GMR-SV biosensor should be the same direction of the axis sensing current and the easy axis of pinned NiO/NiFe/CoFe triple layer oriented to the width direction of device, and the direction of the easy axis of free CoFe/NiFe bilayer was according to the longitudinal direction of device.

• Journal of the Korean Magnetics Society
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• v.17 no.3
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• pp.141-146
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• 2007

A new class of LC-resonator for micro magnetic sensor device was invented and fabricated by means of MEMS technique. The micro LC-resonator consists of a solenoidal micro-inductor with a bundle of soft magnetic microwire cores and a capacitor connected in parallel to the micro-inductor. The core magnetic material is a tiny glass coated $Co_{83.2}B_{3.3}Si_{5.9}Mn_{7.6}$ microwire fabricated by a glasscoated melt spinning technique. The core materials were annealed at various temperatures $150^{\circ}C,\;200^{\circ}C\;,250^{\circ}C\;,$ and $300^{\circ}C$ for 1 hour in a vacuum to improve soft magnetic properties. The solenoidal micro-inductors fabricated by MEMS technique were $500{\sim}1,000{\mu}m$ in length with $10{\sim}20$ turns. The changes of inductance as a function of external magnetic field in micro-inductors with properly annealed microwire cores were varied as much as 370%. Since the permeability of ultra soft magnetic microwire is changing rapidly as a function of external magnetic field. The inductance ratio as well as magnetoimpedance ratio (MIR) in a LC-resonator was varied drastically as a function of external magnetic field. The MIR curves can be tuned very precisely to obtain maximum sensitivity. A prototype magnetic sensor device consisting of the developed microinductors with a multivibrator circuit was test successfully.

• Korean Journal of Optics and Photonics
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• v.21 no.3
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• pp.123-128
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• 2010

Sum frequency generation was utilized to obtain a yellow laser with the wavelength of 578.4 nm for a probe laser of an Yb lattice clock. The output of an Nd:YAG laser with wavelength of 1319 nm and that of an Yb-fiber laser with wavelength of 1030 nm were passed through a waveguided periodically-poled lithium niobate (WG-PPLN) for sum frequency generation. It is required that the probe laser has a linewidth of the order of 1 Hz to fully resolve the Yb lattice clock transition. Thus, the linewidth of the probe laser was reduced by stabilizing the frequency to a super-cavity. This was made of ULE with a low thermal expansion coefficient, and was mounted on an active vibration-isolation table at the optimal point for the reduced sensitivity to vibration. Also, this was installed in a vacuum chamber, and the temperature was stabilized to 1 mK level. This system was installed in an acoustic enclosure to block acoustic noise. The finesse of the super-cavity was measured to be 380 000 from the photon life time of the cavity.

• Journal of the Korean Vacuum Society
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• v.18 no.1
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• pp.66-72
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• 2009

The detection methods are required to monitor and diagnose the abnormality on the insulation condition inside a gas-insulated switchgear (GIS). Due to a good sensitivity to the products decomposed by partial discharges (PDs) in $SF_6$ gas, the development of a SWNT gas sensor is actively in progress. However, a few numerical studies on the diffusion mechanism of the $SF_6$ decomposition products by PD have been reported. In this study, we modeled $SF_6$ decomposition process in a chamber by calculating temperature, pressure and concentration of the decomposition products by using a commercial CFD program in conjunction with experimental data. It was assumed that the mass production rate and the generation temperature of the decomposition products were $5.04{\times}10^{-10}$ [g/s] and over 773 K respectively. To calculate the concentration equation, the Schmidt number was specified to get the diffusion coefficient functioned by viscosity and density of $SF_6$ gas instead rather than setting it directly. The results showed that the drive potential is governed mainly by the gradient of the decomposition concentration. A lower concentration of the decomposition products was observed as the sensors were placed more away from the discharge region. Also, the concentration increased by increasing the discharge time. By installing multiple sensors the location of PD is expected to be identified by monitoring the response time of the sensors, and the information should be very useful for the diagnosis and maintenance of GIS.

• Journal of Sensor Science and Technology
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• v.6 no.4
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• pp.328-336
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• 1997

The CdSe thin films were grown on the Si(100) wafers by a hot wall epitaxy method (HWE). The source and substrate temperature are $600^{\circ}C$ and $430^{\circ}C$ respectively. The crystalline structure of epilayers was investigated by double crystal X-ray diffraction(DCXD). Hall effect on the sample was measured by the van der Pauw method and studied on the carrier density and mobility dependence on temperature. From Hall data, the mobility was increased in the temperature range 30K to 150K by impurity scattering and decreased in the temperature range 150k to 293k by the lattice scattering. In order to explore the applicability as a photoconductive cell, we measured the sensitivity(${\gamma}$), the ratio of photocurrent to darkcurrent(pc/dc), maximum allowable power dissipation(MAPD), spectral response and response time. The results indicated that the photoconductive characteristic were the best for the samples annealed in Cu vapor compare with in Cd, Se, air and vacuum vapour. Then we obtained the sensitivity of 0.99, the value of pc/dc of $1.39{\times}10^{7}$, the MAPD of 335mW, and the rise and decay time of 10ms and 9.5ms, respectively.

• Journal of radiological science and technology
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• v.26 no.4
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• pp.39-46
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• 2003

Digital radiographic systems based on solid-state detectors, commonly referred to as flat-panel detectors, are gaining popularity in clinical practice. Large area, flat panel solid state detectors are being investigated for digital radiography. The purpose of this work was to evaluate the active matrix flat panel digital x-ray detectors in terms of their modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). In this paper, development and evaluation of a selenium-based flat-panel digital x-ray detector are described. The prototype detector has a pixel pitch of $139\;{\mu}m$ and a total active imaging area of $14{\times}8.5\;inch^2$, giving a total 3.9 million pixels. This detector include a x-ray imaging layer of amorphous selenium as a photoconductor which is evaporated in vacuum state on a TFT flat panel, to make signals in proportion to incident x-ray. The film thickness was about $500\;{\mu}m$. To evaluate the imaging performance of the digital radiography(DR) system developed in our group, sensitivity, linearity, the modulation transfer function(MTF), noise power spectrum (NPS) and detective quantum efficiency(DQE) of detector was measured. The measured sensitivity was $4.16{\times}10^6\;ehp/pixel{\cdot}mR$ at the bias field of $10\;V/{\mu}m$ : The beam condition was 41.9\;KeV. Measured MTF at 2.5\;lp/mm was 52%, and the DQE at 1.5\;lp/mm was 75%. And the excellent linearity was showed where the coefficient of determination ($r^2$) is 0.9693.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.191-191
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• 2017

Hydroxy fatty acid (HFA) is an important industrial resource that known to be extracted from seeds of Castor or Lesquerella. However, mass production of HFA from those crops are difficult because of their behavior or life cycle. In this study, we applied HFA synthesis related gene FAH12, RcPDAT1, RcLPCAT, RcDGAT2, and RcPDCT on bioenergy crop Camelina sativa. Furthermore, we determined NaCl or cold stress tolerance changes of transgenic Camelina. RcFAH12, RcPDAT1, RcLPCAT, RcDGAT2, and RcPDCT genes were cloned into multigene expression vector which is engineered with seed specific promoter of FAE1 or Napin. Combination of HFA genes multi-expression vector constructs were divided into Set3 (RcFAH12, RcPDAT1-2, RcLPCAT), Set4 (RcFAH12, RcDGAT2, RCPDAT1-2, RcLPCAT), and Set5 (RcFAH12, RcDGAT2, RCPDAT1-2, RcLPCAT, RcPDCT). Transgenic HFA synthesis Camelina plants were generated using agrobacterium-mediated vacuum infiltration system. Results of fatty acid composition of T1 transgenic Camelina seeds analyzed by GC-MS showed 9.5, 9.0, and 13.6 % of HFA contents in Set3#6, Set4#8, and Set5#10, respectively. Therefore, seeds of T2 generation were harvest from Set5#10 which is shown highest HFA contents, and, 17.7, 8.1 and 10.5 % of HFA contents were determined in Set5#10-5, Set5#10-8, and Set#10-10, respectively. However, 7.7% of C18:2 and 22.3 % of C18:3 among unsaturated fatty acids were decreased in Set5#10-5 than WT. Meanwhile, we confirmed abiotic stress responses in T2 transgenic Camelina Set5#10-5 and Set5#10-10 under 0, 100, 150, and 200 mM NaCl or 25, 15, and $10^{\circ}C$ temperature for 5 weeks. Both Set5#10-5 and Set5#10-10 showed lower growth in height than WT in control and NaCl condition. Growth of leaf length and width were similar in WT and Set5#10-10 but lower in Set5#10-5 under NaCl stress. Number of opened flowers showed that both transgenic Camelina were lower than WT under normal condition. But, WT and Set5#10-10 showed similar opened flower number in 100 and 200 mM NaCl. In cold stress, 15 and $10^{\circ}C$ treatment for 5 weeks did not showed significant changes in between WT and both transgenic lines even they showed different growth rate in control condition. Taken together, growth and development are delayed by expression of exogenous HFA related genes in transgenic lines but relative abiotic stress sensitivity is similar with WT. In conclusion, reduced C18:2 or C18:3 fatty acid composition of seed by HFA synthesis is resulted from lack of resource supplement for development at seedling stage but it is not affect NaCl and cold stress tolerance.