• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.4 s.304
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• pp.45-50
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• 2005

In digital hearing aid system, one of the main problems is acoustic feedback which is known as howling because of miniaturization md high-gain amplification. In this paper, we proposed a feedback cancellation algorithm for hearing aid using time delay and time-varying decorrelation filter. The proposed algorithm has a kind of adaptive filter structure, which is combined with time delay and time-varying decorrelation filter to improve feedback cancellation. An all pass filter was implemented as the time-varying decorrelation filter using low frequency modulator. From the result of computer simulation, it is verified that the proposed algorithm has good ability to cancel feedback.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.4
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• pp.25-32
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• 2011

A control system has been developed by korean engineers for 500MW korean standard type fossil power plant with the advent of retrofit of old control system. The developed control system is required to verify in terms of function and reliability prior to application to a power plant because a power plant is a very important facility in the industry. It is difficult to secure the enough period for installing the control system and commissioning due to the gradual increase of power demand and competitive power market environment. It is essential to verify the control system in order to reduce trial and error cases during overhaul period for application of control system to the power plant. This paper shows the case study of a functional test of a station of control system for power plant.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.4
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• pp.80-85
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• 2011

A time-pickoff circuit used for time measurement suffers from a timing error due to the dependence of the generation time of a timing pulse on the size of the input signal, i.e., time walk. In this study, a time-pickoff method, which employs an automatic gain control (AGC) circuit, is proposed for reducing the timing error. The AGC circuit is added to the input of the comparator, and it renders the sizes of input signals of the comparator relatively uniform. The performance of the proposed time-pickoff method is analyzed using the SPICE simulation, and experiments are performed to confirm the analytical results. The measured time walk is reduced to 2.000 ns by 65% for input signals with a dynamic range of 20 dB as compared to a typical leading-edge discriminator.

• Journal of Korea Water Resources Association
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• v.35 no.4 s.129
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• pp.411-423
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• 2002

Accurate and real time forecasting of runoff has a high priority in the drainage basins prone to short, high intensity rainfall events causing flash floods. To take into account the resolution of hydrological variables within a drainage basin, use of distributed system models is preferred. The Landsat Thematic Mapper(TM) observations enable detailed information on distribution of land cover and other related factors within a drainage basin and permit the use of distributed system models. This paper describes monitoring technique of rainfall excess by SCS curve number method. The time series maps of rainfall excess were generated for all the storm events to show the spatiotemporal distribution of rainfall excess within study basin. A combination of the time series maps of rainfall excess with a flow routing technique would simulate the flow hydrograph at the drainage basin outlet.

• The Korean Journal of Mycology
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• v.22 no.3
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• pp.247-253
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• 1994

This study was carried out to isolate and characterize $A{\alpha}$ mating locus controlling fruiting body formation directly in the Basidiomycete Schzophyllum commune growing in the North America. Total numbers of genomic library of S. commune UVM1-34 was about $2{\times}10^4$ cells. About 90% library was appeared to have about 35 kb inserted genome DNA in cosmid pTC20 vector. 6 clones were proved to have positive signal to probes within Z and Y region in colony and southern hybridization. In the mating activity test, all the 6 positive clones were appeared to have $A{\alpha}3$ mating activity although they had two different restriction patterns. pSC13 containing 5.7 Kb PstI-fragment of UVM 1-34 $A{\alpha}3$ allele showed about 50% clamp cell formation indicating mating activity when cotransformation was done together with cosmid pTC20.

• Transactions on Electrical and Electronic Materials
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• v.4 no.6
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• pp.17-20
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• 2003

This paper describes the effect of halogenic gettering during oxide passivation of commercial solar cell with the $N^{+}$-P-$N^{+}$ structure. In order to study the effect of halogenic gettering on $N^{+}$-P-$N^{+}$ structure mono-crystalline silicon solar cell, we performed conventional POCl$_3$ diffusion for emitter formation and oxide passivation in the presence of HCl vapors. The $N^{+}$-P-$N^{+}$ structure based silicon solar cells were found to have higher short circuit current and minority carrier lifetime. Their performance was also found to be superior than the conventional $N^{+}$-P-$N^{+}$ structure based mono-crystalline silicon solar cell. The cell parameters of the $n^{+}$-p-$p^{+}$ and $n^{+}$-p-$n^{+}$ structure based cells, passivated by HCl assisted oxidation were measured. The improvement in $I_{sc}$ was attributed to the effect of the increased diffusion length of minority carriers, which came from the halogenic gettering effect during the growth of passivating oxide. The presence of chlorine caused gettering of the cells by removing the heavy metals, if any. The other advantage of the presence of chlorine was the removal of the diffusion induced (in oxygen environment) stacking faults and line defects from the surfaces of the silicon wafers. All these effects caused the improvement of the minority carrier lifetime, which in-turn helped to improve the quality of the solar cells.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.221-226
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• 2006

Around 2002, the United States Coast Guard (USCG) identified a need to re-capitalize their Reference Station (RS) and Integrity Monitor (IM) equipment used in the Nationwide Differential Global Position System (NDGPS). Commercially available off-the-shelf differential RS and IM equipment lacked the open architecture required to support long-term goals that include future system improvements such as use of new civil frequencies on L2 and L5 and realization of a higher rate NDGPS beacon data channel intended to support RTK. The first step in preparing for this future NDGPS was to port current RTCM SC-104 compatible RS and IM functionality onto an open architecture PC-based platform. Trimble's product Charisma is a PC-based RS and IM software designed to meet these USCG goals. In fact USCG engineers provided key designs and design insights throughout the development. We cannot overstate the contribution of the USCG engineers. Fundamental requirements for this effort were that it be sufficiently flexible in hardware and software design to support fluid growth and exploitation of new signals and technologies as they become available, yet remain backward compatible with legacy user receivers and existing site hardware and system architecture. These fundamental goals placed an implicit adaptability requirement on the design of the replacement RS and IM. Additionally, project engineers were to remain focused on sustaining the high level of differential GPS service that 1.5 million legacy users have come to depend on. This paper will present new hardware and software (i.e., Trimble's Charisma software) architecture for the next generation NDGPS RS and IM. This innovative approach to engineering on an open architecture PC-based platform allows the system to continue to fulfill legacy NDGPS system requirements and allows the USCG and others to pursue a scalable hardware re-capitalization strategy. We will use the USCG's recapitalization project to explain the essential role of the Charisma software.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.110-113
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• 1992

$n^{+}$-p homojunction InP diodes were fabricated using thermal diffusion of Sulfur into p-type InP substrates(Zn doped, LEC grown, p=2.3${\times}$10$^{16}$c $m^{-3}$). The Sulfur diffusion was carried out at 550$^{\circ}C$, 600$^{\circ}C$, 700$^{\circ}C$ for 4 hours in a sealed quartz ampule(～2ml in volume) containing 5mg I $n_2$ $S_3$ and Img of red phosphorus. The formed junction depth was below 0.5$\mu\textrm{m}$. After the removal of diffused layer on the rear surface of the wafer, the beak ohmic contacts to the p-side were made with a vacuum evaporation of An-Zn(2%) followed by an annealing at 450$^{\circ}C$ for 5 minutes in flowing Ar gas. The front contacts were made with a vacuum evaporation of Au-Ge(12%) followed by an annealing at 500$^{\circ}C$ for 3 minutes in flowing Ar gas. The remarkable sprctral response of the cells obtained at the region of 6000-8000${\AA}$ region. The open circuit voltage $V_{oc}$ , short circuit current density $J_{sc}$ , fill factor and conversion efficiency η of the fabricated pattern solar cells(diffusion condition : at 700$^{\circ}C$ for 4 hours) were 0.660V, 14.04㎃/$\textrm{cm}^2$, 0.6536 and 10.09%, respectively.y.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.196.2-196.2
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• 2013

본 연구에서는 분자선 에피택시 (MBE)법으로 성장된 InAs submonolayer quantum dot (SML-QD)을 태양전지에 응용하여 광학 및 전기적 특성을 평가하였다. 본 연구에서 사용된 양자점 태양전지(quantum dot solar cell, QDSC)의 구조는 n+-GaAs 기판 위에 n+-GaAs buffer와 n-GaAs base layer를 차례로 성장 한 후, 활성영역에 InAs/InGaAs SML-QD와 n-GaAs spacer layer를 8주기 형성하였다. 그 위에 p+-GaAs emitter, p+-AlGaAs window layer를 성장하고 ohmic contact을 위하여 p+-GaAs 를 성장하였다. SML-QD 구조의 두께는 0.3 ML 이며, 이때 SML-QD의 적층수를 4 stacks 으로 고정하였다. SML-QD 와의 비교를 위하여 2.0 ML크기의 InAs자발 형성 양자점 태양전지(SK-QDSC)과 GaAs 단일 접합 태양전지 (reference-SC)를 동일한 성장조건에서 제작하였다. PL 측정 결과, 300 K에서 SML-QD의 발광 피크는 SK-QD 보다 고에너지에서 나타나는데(1.349 eV), 이것은 SML-QD가 SK-QD보다 작은 크기를 가지기 때문으로 사료된다. SML-QD는 single peak를 보이는 반면, SK-QD는 dual peaks (1.112 / 1.056 eV)을 확인하였다. SML-QD의 반치폭(full width at half maximum, FWHM)이 SK-QD에 비하여 작은 것으로 보아 SML-QD가 SK-QD보다 양자점 크기 분포의 균일도가 높은 것으로 해석된다. Illumination I-V 측정 결과, SML-QDSC의 개방 전압(VOC) 과 단락전류밀도(JSC)는 SK-QDSC의 값과 비교해 보면, 각각 47 mV와 0.88 mA/cm2만큼 증가하였다. 이는 SK-QD보다 상대적으로 작은 크기를 가진 SML-QD로 인해 VOC가 증가되었으며, SML-QD가 SK-QD 보다 태양광을 흡수할 수 있는 영역이 비교적 적지만, QD내에 존재하는 energy level에서 탈출 할 수 있는 확률이 더 높음으로써 JSC가 증가한 것으로 분석 된다.

• Bulletin of the Korean Chemical Society
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• v.21 no.7
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• pp.720-726
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• 2000

The analytic gradient method for the equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) energy has been extended to employ a reduced molecular orbital (MO) space. Not only the innermost core MOs but also some of the outermost virtua l MOs can be dropped in the reduced MO space, and a substantial amount of computation time can be reduced without deteriorating the results. In order to study the magnitudes and trends of the effects of the dropped MOs, the geometries and vibrational properties of the ground and excited states of BF, CO, CN, N2, AlCl, SiS, P2, BCl, AIF, CS, SiO, PN and GeSe are calculated with different sizes of molecular orbital space. The 6-31 G* and the aug-cc-pVTZ basis sets are employed for all molecules except GeSc for which the 6-311 G* and the TZV+f basis sets are used. It is shown that the magnitudes of the drop-MO effects are about $0.005\AA$ in bond lengths and about 1% on harmonic frequencies and IR intensities provided that the dropped MOs correspond to (1s), (1s,2s,2p), an (1s,2s,2p,3s,3p) atomic orbitals of the first, the second, and the third row atoms, respectively. The geometries and vibrational properties of the first and the second excited states of HCN and HNC are calculated by using a drastically reduced virtual MO space as well as with the well defined frozen core MO space. The results suggest the possibility of using a very smalI MO space for qualitative study of valence excited states.