• Journal of the Korea Convergence Society
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• v.9 no.6
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• pp.203-207
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• 2018

This paper deals with the design and development of a lens system capable of imaging an infrared image of $3{\sim}5{\mu}m$ wavelength bands with a focal length of 24mm and good atmospheric transmission characteristics. The design used CodeV, a commercial design program, and the optimization is carried out with weighting to eliminate chromatic aberration, spherical aberration and distortion. The designed lens system consists of two lenses consisting of Si and Ge. Each lens has an aspherical surface on one side. And this optical system has the resolution of the characteristics that the MTF value is 0.40 at the line width of 29lp/mm and the MTF value is 0.25 at the line width of 20lp/mm. This optical system is considered to have the capability to be applied to the thermal imaging camera for MWIR using the $206{\times}156$ array infrared detector of $25{\mu}m$ pixels and the $320{\times}240$ array infrared detector of $17{\mu}m$ pixels.

• Journal of Energy Engineering
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• v.5 no.1
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• pp.8-18
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• 1996

As a part of comprehensive IGCC process simulation, the thermal performance analysis was performed for coal gas firing combined power plant. The combined cycle analyzed consisted of il Texaco gasifier and a low temperature gas cleanup system for the gasification block and a GE 7FA gas turbine, a HRSG and steam turbine for the power block. A steady state simulator called ASPEN(Advanced System for Process Engineering) code was used to simulate IGCC processes. Composed IGCC configuration included air integration between ASU and gas turbine and steam integration between gasifier, gas clean up and steam turbine. The results showed 20% increase in terms of gas turbine power output(MWe) comparing with natural gas case based on same heat input. The results were compared with other study results which Bechtel Canada Inc. performed for Nova Scotia power plant in 1991 and the consistency was identified within two studies. As a result, the analysing method used in this study is verified as a sound tool for commercial IGCC process evaluation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1980-1986
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• 2016

In this study, we studied the gamma-radiation effect of fiber Bragg gratings (FBGs) on the high temperature annealing condition after grating inscription using a KrF UV laser (248 nm). The FBGs were fabricated in a different annealing temperature using the same commercial Ge-doped silica core fiber (SMF-28e) and exposed to gamma-radiation up to a dose of 31 kGy at the dose rate of 115 Gy/min. The high temperature annealing procedure for grating stabilization was applied to change the radiation sensitivity of the FBGs. According to the experimental data and analysis results, the gratings that were stabilized at different temperatures at 100, 150 and $200^{\circ}C$ have clearly shown that exposure to higher temperatures increases their radiation sensitivity. The radiation-induced Bragg wavelength shift (BWS) was shown a difference of up to about a factor of two depending on the annealing temperature conditions of the gratings.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.9
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• pp.522-529
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• 2002

In this paper, computer simulations of the physical Phenomena occurring in the arc region before and after current zero were carried out to evaluate the thermal recovery characteristics of a Laval nozzle. A commercial CFD program "PHOENICS" is used for the simulation and the user-coded subroutines to consider the arcing phenomena were added to this program by the authors. The computed results were verified by the comparison with the test results presented by the research group of GE Co.(General Electric Company). In order to investigate the state of the arc region after current zero, the simulation was carried out with three steps. They are steady state arc simulation, transient arc simulation before current zero, and transient hot-gas flow simulation after current zero. The semi-experimental arc radiation model is adapted to consider the radiation energy transport and Prandtl's mixing length model is employed as the turbulence model. The electric field and the magnetic field were calculated with the same grid structure used for the simulation of the flow field. The post-arc current was calculated to evaluate the thermal recovery characteristics after current zero. Compared with the results obtained by GE Co., it has been found that the critical RRRV(ratio of rise of recovery voltage) will be determined previously by this study.his study.

• Investigative Magnetic Resonance Imaging
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• v.7 no.1
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• pp.12-21
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• 2003

Purpose : In order to overcome limitations in the existing conventional spectrometer, a new spectrometer with advanced functionalities is designed and implemented. Materials and Methods : We designed a spectrometer using the TMS320C6701 DSP capable of 1 giga floating point operations per second (GFLOPS). The spectrometer can generate continuously varying complicate gradient waveforms by real-time calculation, and select image plane interactively. The designed spectrometer is composed of two parts: one is DSP-based digital control part, and the other is analog part generating gradient and RF waveforms, and performing demodulation of the received RF signal. Each recover board can measure 4 channel FID signals simultaneously for parallel imaging, and provides fast reconstruction using the high speed DSP. Results : The developed spectrometer was installed on a 1.5 Tesla whole body MRI system, and performance was tested by various methods. The accurate phase control required in digital modulation and demodulation was tested, and multi-channel acquisition was examined with phase-array coil imaging. Superior image quality is obtained by the developed spectrometer compared to existing commercial spectrometer especially in the fast spin echo images. Conclusion : Interactive control of the selection planes and real-time generation of gradient waveforms are important functions required for advanced imaging such as spiral scan cardiac imaging. Multi-channel acquisition is also highly demanding for parallel imaging. In this paper a spectrometer having such functionalities is designed and developed using the TMS320C6701 DSP having 1 GFLOPS computational power. Accurate phase control was achieved by the digital modulation and demodulation techniques. Superior image qualities are obtained by the developed spectrometer for various imaging techniques including FSE, GE, and angiography compared to those obtained by the existing commercial spectrometer.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.10
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• pp.2461-2465
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• 2013

This paper investigates the influence of hydrogen loading process on the radiation sensitivity of fiber Bragg gratings (FBG). We made the FBG inscribed in the same commercial Ge-doped fiber with different hydrogen loading periods. We measured the Bragg wavelength shift (BWS) of the FBG exposed to gamma-radiation up to a dose of 18 kGy, and evaluated the change of full width at half maximum (FWHM) and the FBG temperature sensitivity coefficient after irradiation. Varying hydrogen loading parameter led to BWS differences up to nearly a factor of two.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.3 no.2
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• pp.91-97
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• 2017

$^{18}F-THK-5351$ is a PET radiotracer to image the hyperphosphorylated tau fibrillar aggregates in human brain. This protocol describes the optimized radiosynthesis of $^{18}F-THK-5351$ using a commercial GE $TRACERlab^{TM}$ $FX_{FN}$ radiosynthesis module. $^{18}F-THK-5351$ was prepared by nucleophilic [$^{18}F$]fluorination from its protected tosylate precursors, (S)-(2-(2-methylaminopyrid-5-yl)-6-[[2-(tetrahydro-2H-pyran-2-yloxy)-3-tosyloxy]propoxy] quinolone(THK-5352), at $110^{\circ}C$ for 10 min in dimethyl sulfoxide, followed by deprotection with 1 N HCl. The average radiochemical yield of $^{18}F-THK-5351$ was $31.9{\pm}6.7%$(decay-corrected, n = 10), with molar activity of $198.1{\pm}33.9GBq/{\mu}mol$($5.4{\pm}0.9Ci/{\mu}mol$, n = 10). The radiochemical purity was determined to be above 98%. The overall production time including HPLC purification is approximately 70 min. This fully-automated protocol is validated for clinical use.

• Journal of Mechanical Science and Technology
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• v.17 no.11
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• pp.1746-1755
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• 2003

Operating characteristics of a triple pressure reheat HRSG are analyzed using a commercial software package (Gate Cycle by GE Enter Software). The calculation routine determines all the design parameters including configuration and area of each heat exchanger. The off-design calculation part has the capability of simulating the effect of any operating parameters such as power load, process requirements, and operating mode, etc., on the transient performance of the plant. The arrangement of high-temperature and intermediate-temperature components of the HRSG is changed, and its effect on the steam turbine performance and HRSG characteristics is examined. It is shown that there could be a significant difference in HRSG sizes even though thermal performance is not in great deviation. From the viewpoint of both economics and steam turbine performance, it should be carefully reviewed whether the optimum design point could exist. Off-design performance could be one of the main factors in arranging components of the HRSG because power plants operate at various off-design conditions such as ambient temperature and gas turbine load, etc. It is shown that different heat exchanger configurations lead to different performances with ambient temperature, even though they have almost the same performances at design points.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.5
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• pp.215-222
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• 2009

Many concepts of external magnetic field applications in crystal growth processes have been developed to control melt convection, impurity content and growing interface shape. Especially, travelling magnetic fields (TMF) are of certain advantages. However, strong shielding effects appear when the TMF coils are placed outside the growth vessel. To achieve a solution of industrial relevance within the framework of the $KRISTMAG^{(R)}$ project inner heater-magnet modules(HMM) for simultaneous generation of temperature and magnetic field have been developed. At the same time, as the temperature is controlled as usual, e.g. by DC, the characteristics of the magnetic field can be adjusted via frequency, phase shift of the alternating current (AC) and by changing the amplitude via the AC/DC ratio. Global modelling and dummy measurements were used to optimize and validate the HMM configuration and process parameters. GaAs and Ge single crystals with improved parameters were grown in HMM-equipped industrial liquid encapsulated Czochralski (LEC) puller and commercial vertical gradient freeze (VGF) furnace, respectively. The vapour pressure controlled Czochralski (VCz) variant without boric oxide encapsulation was used to study the movement of floating particles by the TMF-driven vortices.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.10
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• pp.9-15
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• 2009

In this paper, we invented a new structure of fast ATC(Automatic Threshold Control) circuit. Using the structure we made a new burst-mode limiting amplifier with fast ATC function using commercial $0.8{\mu}m$ BiCMOS technology. It's ATC function worked so fast that even the first bit of burst-data could be detected, which confirmed that the new structure was useful for fast ATC. However, in the beginning of a burst, distortions in duty-cycle occurred and increased up to 59% of duty-cycle as amplitude of input signal increased. But we confirmed that after 10 cycles passed, duty-cycles was staying below 52% of duty-cycle for any magnitude of input signal.