• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.10
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• pp.22-29
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• 1998

In this paper, an 10 bit current-mode CMOS A/D converter with a current predictor is designed with a CMOS process to be integrated into a portable image signal processing system. A current predictor let the number of comparator reduce to 70 percent compared with the two step flash architecture. The current magnitude of current reference is reduced to 68 percent with a modular current reference. The designed 10 bit Low-power current-mode CMOS A/D converter with a current predictor is simulated with HSPICE using 0.6$\mu\textrm{m}$ N-well single-poly triple-metal CMOS process parameters. It results in a conversion rate of 10MSamples/s. A power consumption is measured to be 94.4mW at single +5V supply voltage. The 10 bit A/D converter fabricated using the same process occupies the chip area of 1.8mm x 2.4mm.

• Applied Chemistry for Engineering
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• v.33 no.3
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• pp.279-283
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• 2022

UV-vis spectroscopy is one of the powerful tools for measuring the concentrations of reactant and products during a chemical reaction. However, there is an limitation of using the technique when the reaction undergoes in high concentration and high temperature. Color analysis using camera images can provide the identical results with UV-vis analysis with regardless of the sample concentration and temperature. The catalytic reduction reaction of resazurin to resorufin was investigated using the color analysis with the color spaces such as CIE L^*a^*b^*. Moreover, the color analysis enabled the independent analysis of two different material's concentrations without the deconvolution of overlapped wavelengths unlike the case of using UV-vis spectroscopy.

• Korean Journal of Environment and Ecology
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• v.21 no.4
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• pp.318-335
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• 2007

Floral study and present vegetation survey were conducted at a representative reclaimed wetland located behind the Rural Research Institute at Ansan, Gyeonggi-do. The importance values were calculated from the ground cover and frequency of recorded species within quadrats and detrended canonical correspondence analysis was conducted using environment variables, such as total nitrogen, electric conductivity, available phosphate, nitrate nitrogen and the distance from the inner roads. And basal areas for the trees encroaching on the reclaimed wetland were estimated to take a look at the on-going situation about the succession routes on land. As a result, 46 families and 158 species of plants were recorded and Pragmites communis was found to be a dominant species as the present vegetation. The ordination analysis results showed that species distribution was purposely explained by total nitrogen in soil and its content in nitrate nitrogen. The invasion of Robinia pseudoacacia and Pinus rigida whose basal areas were $22.3m^2$ and $1.6m^2$ respectively, into the interior areas of the reclaimed wetland was found to cause a disturbance making some parts of the wetland into land. The zoning program using water level control and migratory roads is becoming a contributing factor in destroying a wetland, so it's suggested that some adjustments should be needed to take care of it.

• Korean Journal of Materials Research
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• v.3 no.4
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• pp.336-343
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• 1993

The standard map for polyerystalline $YBa_2Cu_3O_7$-X was construeted and indexed from pressed tape sintered bulk and compressed bulk samples were drawn by the [001-110-110] stereographie quadrant map and by the ECPs from individual grains of the speeimens. The relationship between the (001) texture development and critical current density (Jc) for various samples was discussed. An (001) orintation was preferred in the pressed tape thickness was decreased. and in the compressed bulk as the compression strain was increaesed.The (001) orientation made a signifieant in crease on Jc. We conclded that an ECP technique was very useful for the analysis of the orientation distribution in small-sized $YBa_2Cu_3O_7$-X specimens such as superonducting tapes or thin films.

• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.361-368
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• 2005

This study proposes an algorithm for detection and analysis of cracks in digital image of concrete surface to automate the measurement process of crack characteristics such as width, length, and orientation based on image processing technique. The special features of algorithm are as follows: (1) application of morphology technique for shading correction, (2) improvement of detection performance based on enhanced binarization and shape analysis, (3) suggestion of calculation algorithms for width, length, and orientation. A MATLAB code was developed for the proposed algorithm, and then test was performed on crack images taken with digital camera to examine validity of the algorithm. Within the limited test in the present study, the proposed algorithm was revealed as accurately detecting and analyzing the cracks when compared to results obtained by a human and classical method.

• Journal of Korean Society of Forest Science
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• v.99 no.1
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• pp.52-56
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• 2010

Crown fuel characteristics such as crown bulk density, crown base height, and fuel moisture content of Japanese red pine were analyzed. Ten trees in Mt. Palgong at Daegu, were destructively sampled and their crown fuels were weighed separately for each fuel category. Fuel content of live and dead crown component were 53%, and 15.3%, respectively. Foliar moisture content was 56%. Needles and twigs with diameter less than 1cm diameter accounted for 16.2%, 55% of total and crown fuel load. Average crown bulk density of Japanese red pine was 0.24 kg/$m^3$, effective crown fuel bulk density was 0.1325 kg/$m^3$.

• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.653-660
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• 1996

For oxygen PSA process development, adsorbed amount of oxygen and nitrogen on various adsorbents were measured corresponding Langmuir isotherm parameters were measured. A reasonable adsorbent for oxygen process was selected based on the effective adsorbed amount. The PSA process consists of adsorption, desorption, pressurization, purging and pressure equilization steps. Adsorption pressure was about 2 atm and desorption pressure was between 120 torr to 400torr. Cycle time of 2-bed PSA process was 80 seconds and that of 3-bed oxygen PSA process was 180 seconds. In order to compare and analyze operation characteristics and economic feasibilities of 2-bed and 3-bed oxygen PSA processes, productivity, oxygen concentration and recovery were compared and the effect of purge and pressurization steps on the performance of PSA processes were analyzed. For the commercial scale oxygen PSA process, capital and electricity cost were estimated. In the range of $O_2$ production less than $700Nm^3/hr$, the 2-bed process is conformed more feasible in economic view point.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.143-143
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• 2016

알루미늄 합금은 내구성과 내식성이 우수할 뿐만 아니라 다양한 표면개질을 통해 그 표면 특성을 더욱 향상시킬 수 있다. 특히 Al-Mg계 5083-H321 Al 합금의 경우 가공성 및 용접성이 우수하여 선체 재료로 널리 이용되는데, 이는 선체중량의 경량화가 가능하여 연료비 절감과 빠른 선속 등 다양한 이점을 지니기 때문이다. 그러나 선속의 고속화에 따라 선체에 가해지는 유체충격이 증가하고 정압 저하에 기인하여 캐비테이션-침식 손상이 증가할 뿐만 아니라 해수환경 특성 상염소이온의 존재로 부식이 가속화되는 등 침식 및 부식의 시너지효과로 손상은 크게 증가한다. 이에 대한 방지대책으로 다양한 표면개질 기법이 제안되고 있으나 강한 충격압이 동반된 캐비테이션 침식-부식 복합 손상 환경에서는 표면처리만으로는 불가능할 수 있다. 따라서 본 연구에서는 양극산화된 5083-H321을 대상으로 캐비테이션 환경 하에서 일정 전위를 인가하여 침식-부식 손상이 최소화되는 최적전위를 규명하고자 한다. 이를 위해 먼저 분극 실험을 통해 재료의 전기화학적 거동을 바탕으로 임의의 전위를 선정하고 해당 전위를 인가한 상태에서 캐비테이션 실험을 실시하였다. 이때 분극실험과 캐비테이션-전기화학 복합실험 모두 $25^{\circ}C$의 해수에서 실시하였으며, 전기화학적 분극실험은 유효면적이 $3.24cm^2$인 시편에 2 mV/s의 분극속도로 0 ~ -3 V 까지 인가하였고, Ag/AgCl 기준전극과 백금대극을 사용하였다. 캐비테이션-전기화학 복합 실험은 정전위를 인가한 상태에서 $30{\mu}m$의 진폭으로 20분간 실시하였으며, 혼팁과 시험편 사이의 거리는 1 mm로 일정하게 유지하였다. 실험 후 표면 손상의 정량적 분석을 위해 인가된 전위별 전류밀도를 비교하고, 무게감소량을 측정하였으며, 손상특성 분석을 위해 3D현미경과 주사전자현미경(SEM)을 통해 표면을 분석하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.621-627
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• 2008

This paper presents a compact and miniaturized power detector utilizing low temperature co-fired ceramics(LTCC) technology for the application in wireless handset system to monitor the transmitting power at the frequency of 824-849MHz. The proposed power detector is composed of detector diode, lumped components for matching network, and LTCC stripline coupler based on LTCC substrate technology. A 20dB LTCC stripline direction coupler is designed and implemented with many bending section in order to reduce the practically occupied area for miniaturization. A zero bias schottky diode is adopted for detector design because of its high speed operation with minimized loss. The measured performances of fabricated detector agree well with the predicted results with a good linearity within the effective input RF power range.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.4
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• pp.617-624
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• 2023

Recently, miniaturization and low power consumption of electronic products and improved efficiency and power factor improvement have become a matter of great interest. In this paper, an AC-DC converter based on PWM control was designed and made. The AC-DC converter is designed with a structure in which one rectifier circuit and one output voltage control circuit are connected in series. The rectifier circuit is a diode-based single phase full-wave current circuit and the output voltage control circuit is a DC-DC conversion circuit based on PWM control. Arduino was used as the main control device for PWM control, and LCD was configured at the output stage so that the control result could be checked. The error between the output voltage displayed on the oscilloscope and LCD and the target output voltage was confirmed through repeated experiments with the test circuit, and the validity of the proposed design methodology was confirmed by showing an error rate of about 5% based on the oscilloscope measurement value.