• 한국환경농학회지
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• 제24권1호
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• pp.17-23
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• 2005

한정된 수질자료를 이용 오염부하 산정시 집중적으로 많은 샘플을 채취한 경우에 비해 어느 정도 차이를 갖는지를 규명하는 것은 모니터링에 따른 오염부하량 산정결과의 신뢰범위 파악뿐만 아니라 경제적인 수질 샘플 채수빈도 수립에 곡 필요할 것으로 사료된다. 그 결과를 요약하면 다음과 같다. 논에서의 강-은유출시 채수 빈도가 오염부하 산정에 미치는 영향을 파악하기 위해 9개의 강우사상에 대해 2시간 간격으로 연속 수질샘플을 실시하여 분석한 결과 전체적으로 강우-유출과정 중 T-N, T-P, SS 농도는 시간별로 증 감변동을 하였으나 유량과의 상관성은 나타나지 않았다. 수질샘플 횟수에 의한 영향은 강우-유출과정 중 5회 정도 샘플을 실시하면 많은 수의 샘플을 채수한 경우에 비해 T-N ${\pm}15.2%$, T-P는 $-20.0{\sim}26.2%$, SS는 $-28.6{\sim}35.7%$ 범위안에서 오염부하를 추정할 수 있는 것으로 나타났으며, 차이범위가 ${\pm}10%$ 내에 들어가기 위한 샘플수는 일주기 조사시 T-N, T-P의 경우는 6회, SS의 경우는 단기유출시는 4회 정도 실시하면 되고, 장기 유출시에는 11회 정도 실시하면 되는 것으로 조사되었다. 유량-유하부하량 관계식에서 ${\pm}10%$내의 차이를 보일 샘플횟수는 T-N의 경우는 6회 이상, T-P와 SS는 9회 이상 정도 실시하면 되는 것으로 조사되었다.

• 대한기계학회논문집B
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• 제24권9호
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• pp.1219-1226
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• 2000

An efficient method is developed for plunger thermal cycle analysis in repeated forming process of the TV glass. The plunger undergoes temperature fluctuation during a cycle due to the repeated contact and separation from the glass, which attains a cyclic steady state having same temperature history at every cycle. Straightforward analysis of this problem brings about more than 80 cycles to get reasonable solution, and yet hard to setup stopping criteria due to extremely slow convergence. An exponential fitting method is proposed to overcome the difficulty, which finds exponential function to best approximate temperature values of 3 consecutive cycles, and new cycle is restarted with the fitted value at infinite time. Numerical implementation shows that it reduces the number of cycles dramatically to only 6-18 cycles to reach convergence within 10 accuracy. A system for the analysis is constructed, in which the thermal analysis is performed by commercial software ANSYS, and the fitting of the result is done by IMSL library. From the parametric studies, one reveals some important facts that although the plunger cooling or the glass thickness is increased, its counter part in contact is not much affected, duo to the low thermal conductance of the glass.

• 한국입자에어로졸학회지
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• 제7권4호
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• pp.113-121
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• 2011

The aerosol nanoparticles are suspected to be exposed to workers in nanomaterial manufacturing facilities. However, the exposure assessment method has not been established. One of important issues is to characterize background level of nanoparticles in workplaces. In this study, intensive aerosol measurements were made at a $TiO_2$ manufacturing laboratory for five consecutive days in May of 2010. The $TiO_2$ nanoparticles were manufactured by the thermal-condensation process in a heated tube furnace. The particle number size distribution was measured using a scanning mobility particle sizer every 5 min, in order to detect particles ranging from 14.5 to 664 nm in diameter. Total particle number concentration shows a severe diurnal variation irrespective of manufacturing process, which was governed by nanoparticles smaller than 50 nm in diameter. During the background monitoring periods, significant peak concentrations were observed between 2 p.m. and 3 p.m. due to the infiltration of secondary aerosol particles formed by photochemical smog. Although significant increase in nanoparticle concentration was also observed during the manufacturing process twice among three times, these particle peak concentrations were lower than those observed during the background measurement. It is suggested that the investigation of background particle contamination is needed prior to conducting main exposure assessment in nanomaterial manufacturing workplaces or laboratories.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.192-198
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• 2000

Three dimensional thermal cycle analysis of the plunger is carried out in repeated forming process of the TV glass, which is continued work of two dimensional analysis where an efficient method has been proposed. The plunger undergoes temperature fluctuation during a cycle due to the repeated contact and separation from the glass, which attains a cyclic steady state having same temperature history at every cycle. Straightforward analysis of this problem brings about more than 90 cycles to get reasonable solution. An exponential function fitting method is proposed, which finds exponential function to best approximate temperature values of 3 consecutive cycles, and new cycle is restarted with the fitted value at infinite time. Number of cases are analyzed using the proposed method and compared to the result of straightforward repetition, from which one finds that the method always reaches nearly convergent solution within $9{\sim}12$ cycles, but turns around afterwards without further convergence. Two step use is found most efficient, in which the exponential fitting is carried out fer the first 12 cycles, followed by simple repetition, which shows fast convergence expending only 6 additional cycles to get the accuracy within 2 error. This reduces the computation cycle remarkably from 90 to 18, which is 80% reduction. From the parametric studies, one reveals that the overall thermal behavior of the plunger in terms of cooling parameters and time is similar to that of 2 dimensional analysis.

• 전기전자학회논문지
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• 제24권2호
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• pp.468-474
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• 2020

IoT, 무선 센서 네트워크와 같이 제한된 자원을 갖는 응용분야의 보안에 적합하도록 개발된 경량 블록 암호 알고리듬 SPECK의 하드웨어 구현에 관해 기술한다. 블록 암호 SPECK 크립토 코어는 8가지의 블록/키 크기를 지원하며, 회로 경량화를 위해 내부 데이터 패스는 16-비트로 설계되었다. 키 초기화 과정을 통해 복호화에 사용될 최종 라운드 키가 미리 생성되어 초기 키와 함께 저장되며, 이를 통해 연속 블록에 대한 암호화/복호화 처리가 가능하도록 하였다. 또한 처리율을 높이기 위해 라운드 연산과 키 스케줄링이 독립적으로 연산되도록 설계하였다. 설계된 SPECK 크립토 코어를 FPGA 검증을 통해 하드웨어 동작을 확인하였으며, Virtex-5 FPGA 디바이스에서 1,503 슬라이스로 구현되었고, 최대 동작 주파수는 98 MHz로 추정되었다. 180 nm 공정으로 합성하는 경우, 최대 동작 주파수는 163 MHz로 추정되었으며, 블록/키 크기에 따라 154 Mbps ~ 238 Mbps의 처리량을 갖는다.

• 한국전기전자재료학회논문지
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• 제29권5호
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• pp.268-273
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• 2016

In this study, we observed current-voltage characteristics of the MIM (metal-insulator-metal) structure. The $WO_x$ material was used between metal electrodes as the oxide insulator. The structure of the $Al/WO_x/TiN$ shows bipolar resistive switching and the operating direction of the resistive switching is clockwise, which means set at negative voltage and reset at positive voltage. The set process from HRS (high resistance state) to LRS (low resistance state) occurred at -2.6V. The reset process from LRS to HRS occurred at 2.78V. The on/off current ratio was about 10 and resistive switching was performed for 5 cycles in the endurance characteristics. With consecutive switching cycles, the stable $V_{set}$ and $V_{reset}$ were observed. The electrical transport mechanism of the device was based on the migration of oxygen ions and the current-voltage curve is following (Ohm's Law ${\rightarrow}$ Trap-Controlled Space Charge Limited Current ${\rightarrow}$ Ohm's Law) process in the positive voltage region.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.523-523
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• 2012

As the wafer geometric requirements continuously complicated and minutes in tens of nanometers, the expectation of real-time add-on sensors for in-situ plasma process monitoring is rapidly increasing. Various industry applications, utilizing plasma impedance monitor (PIM) and optical emission spectroscopy (OES), on etch end point detection, etch chemistry investigation, health monitoring, fault detection and classification, and advanced process control are good examples. However, process monitoring in semiconductor manufacturing industry requires non-invasiveness. The hypothesis behind the optical monitoring of plasma induced ion current is for the monitoring of plasma induced charging damage in non-invasive optical way. In plasma dielectric via etching, the bombardment of reactive ions on exposed conductor patterns may induce electrical current. Induced electrical charge can further flow down to device level, and accumulated charges in the consecutive plasma processes during back-end metallization can create plasma induced charging damage to shift the threshold voltage of device. As a preliminary research for the hypothesis, we performed two phases experiment to measure the plasma induced current in etch environmental condition. We fabricated electrical test circuits to convert induced current to flickering frequency of LED output, and the flickering frequency was measured by high speed optical plasma monitoring system (OPMS) in 10 kHz. Current-frequency calibration was done in offline by applying stepwise current increase while LED flickering was measured. Once the performance of the test circuits was evaluated, a metal pad for collecting ion bombardment during plasma etch condition was placed inside etch chamber, and the LED output frequency was measured in real-time. It was successful to acquire high speed optical emission data acquisition in 10 kHz. Offline measurement with the test circuitry was satisfactory, and we are continuously investigating the potential of real-time in-situ plasma induce current measurement via OPMS.

• Membrane and Water Treatment
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• 제8권4호
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• pp.311-321
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• 2017

Hydrophilic and high modulus PPTA molecules were incorporated into PVDF matrix via the in situ polymerization of PPD and TPC in PVDF solution. PPTA/PVDF/NWF blend membrane was prepared through the immersion precipitation phase inversion method and nonwoven coating technique. The membrane integrated technology including PPTA/PVDF/NWF blend membrane and reverse osmosis (RO) membrane was employed to treat the polyester/viscose spunlace nonwoven process wastewater. During the consecutive running of six months, the effects of membrane integrated technology on the COD, ammonia nitrogen, suspended substance and pH value of water were studied. The results showed that the removal rate of COD, ammonia nitrogen and suspended substance filtered by PPTA/PVDF blend membrane was kept above 90%. The pH value of the permeate water was about 7.1 and the relative water flux of blend membrane remained above 90%. After the deep treatment of RO membrane, the permeate water quality can meet the water circulation requirement of spunlace process.

• 대한핵의학회지
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• 제31권3호
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• pp.330-338
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• 1997

기저와 부하 뇌관류 SPECT를 순차적으로 촬영하여 2차영상에서 1차영상을 감산하여 부하 영상을 얻으면 신호가 줄어들고 잡음은 더해지므로 영상의 질이 나빠졌다. 촬영시간과 주사량에 대해 비례적인 계수와 촬영행위와 상관있는 배후방사능을 고려하여 기저영상과 감산영상의 신호 잡음 비가 최대가 되도록 하는 주사량과 촬영시간의 짝을 찾았다. 순차 촬영 시간을 30분으로 하고 주사총량이 1850MBq(50mCi)이며 아세타졸아미드의 부하에 의해 뇌의 주사량대비 섭취가 1.2배일 때 기저영상과 감산영상의 신호 잡음 비가 최대인 조건은 1차 주사량/촬영시간이 15mCi/17분, 2차 주사량/촬영시간이 35mCi/13분이었다.

• 한국식품과학회지
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• 제42권3호
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• pp.281-286
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• 2010

본 연구는 자동화된 상업용 배추김치 제조공정 중에서 원료와 공정별로 미생물의 변화를 조사하고자 수행하였다. 김치제조에 사용되는 여러가지 재료별로 미생물 분포를 조사한 결과, 마늘, 생강, 고추가루에서 많은 수의 호기성 박테리아, 젖산균, Leuconostoc, 그리고 효모가 검출되었으며, 이로써 위 부원료들이 김치에 존재하는 미생물들의 주요 공급원임을 알 수 있었다. 김치를 제조하는 공정 별로 미생물 변화를 모니터링 한 결과, 배추절임 공정에서 총 균수가 증가하였고 그 이후 세척공정에서는 단지 미생물수를 1 log CFU/g 줄이는데 그쳐 미생물 수 감소효과는 적은 것으로 판명되었다. 효모 또한 다양한 부재료와 최종 김치에서 검출되었다. 따라서, 김치 제품에 최종적으로 존재하는 미생물 수를 줄이고자 한다면 위의 원료 중에서는 위의 부재료에 대해, 그리고 제조공정에서는 절임에 사용되는 천일염과 절임탱크에 대해 적절한 살균대책이 강구되어야 하겠다. 또한 차염소산 살균 공정은 절임과 세척공정 사이에 위치해야만 가장 큰 효과를 기대할 수 있을 것으로 판단되었다. 또한 검출된 효모에 대한 저해 수단으로 적절한 저해제의 첨가도 고려되어야 하겠다. 본 연구의 결과는 공장김치의 HACCP 구축과 개선에 활용될 것으로 기대된다.