• 한국산업보건학회지
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• 제16권3호
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• pp.254-263
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• 2006

Manganese has a role as both toxic and essential in humans. Manganese is also an essential component in the welding because it increases the hardness and strength, prevents steel from cracking of welding part and acts as a deoxidizing agent to form a stable weld. In this study, manganese generation rate and its content was determined in flux cored arc welding on stainless steel. Domestic two products and foreign four products of flux cored wires were tested in the well designed fume generation chamber as a function of input power. Welding fume was measured by gravimetric method and metal manganese was determined by inductively coupled plasma-atomic emission spectrophotometer. The outer shell of the flux cored wire tube and inner flux were analyzed by scanning electron microscopy to determine their metal compositions. Manganese generation rate($FGR_{mn}$) was increased as the input power increased. It was 16.3 mg/min at the low input power, 38.1 mg/min at the optimal input power, and up to 55.4 mg/min at the high input power. This means that $FGR_{mn}$ is increased at the work place if welder raise the current and/or voltage for the high productivity. The slope coefficient of $FGR_{mn}$ was smaller than that of the generation rate of total fume(FGR). Also, the correlation coefficient of $FGR_{mn}$ was 0.65 whereas that of FGR is 0.91. $FGR_{mn}$ was equal or higher in the domestic products than that of the foreign products although FGR was similar. From the electron microscopic analytical data, we concluded that outer shell of the wire was composed mainly of iron, chromium, nickel and less than 1.2 % of manganese. There are many metal ingredients such as iron, silica, manganese, zirconium, titanium, nickel, potassium, and aluminum in the inner flux but they were not homogeneous. It was found that both $FGR_{mn}$ and content of manganese was higher and more varied in domestic flux cored wires than those of foreign products. To reduce worker exposure to fumes and hazardous component at the source, further research is needed to develop new welding filler materials that improve the quality of flux cored wire in respect to these points. Welder should keep in mind that the FGR, $FGR_{mn}$ and probably the generation rate of other hazardous metals were increased as the input power increase for the high productivity.

• 전기전자학회논문지
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• 제14권1호
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• pp.8-16
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• 2010

본 논문에서는 CCD 이미지 처리를 위한 최대 15MS/s의 속도의 중저속 아날로그-프론트 엔드(analog-front end, AFE)에서 사용될 수 있는 연속근사 ADC(Successive Approximation ADC, SA-ADC)의 설계를 제안한다. 파이프라인 ADC와 달리 SA-ADC는 동작주파수의 변화에 따른 전력소모의 스케일링(scaling) 효과가 크므로 저속에서 중속에 이르는 넓은 범위의 가변 데이터 처리 속도의 응용에 매우 효과적이다. 제안하는 설계는 입력 신호의 샘플링 동작을 내부 DAC(sub-DAC)로부터 따로 분리한 후, 커패시터 커플링을 통해 차동 결합함으로써 신호경로에 이르는 부하를 크게 줄이는 "차동 커패시터 커플링 기법"의 도입, 연속근사의 기법적 측면에서 signed 구조를 활용하여 데이터 변환주기 이전에 홀드된 입력신호로부터 미리 MSB(sign bit)를 결정함으로써 1사이클의 변환주기를 절약하고 내부 DAC의 하드웨어를 1비트 줄이는 구조와 같은 특징을 갖고 있다. 본 설계는 3.3V $0.35{\mu}m$ CMOS 공정으로써 설계하고 Spectre 시뮬레이션을 이용하여 그 특성을 분석함으로써 CCD 아날로그 프론트-엔드에 적용될 수 있음을 입증하였다.

• 전기전자학회논문지
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• 제21권3호
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• pp.248-251
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• 2017

본 논문에서는 $360^{\circ}$ 전방위 화각을 가진 Dash Camera의 EMI 대응을 위한 보드 설계를 제안한다. 제안된 보드는 DM 및 CM 입력 노이즈 감소회로를 설계하고 능동 EMI 필터 결합회로를 적용하여 개발한다. DM 및 CM 입력 노이즈 감소회로 설계부분에서는 기생적 커패시턴스(CP)을 통해 입력 신호로 커플링된 DM 잡음을 얻기 위한 차동연산 증폭기 회로를 사용한다. 능동 EMI 필터 결합회로를 적용하여 설계하는 부분에서는 회로의 간략화를 위하여 EMI 소스의 노이즈를 분리하여 보상해 주기 위하여 노이즈 분리기를 설치하여 CM과 DM 능동필터를 동시에 보상한다. 제안된 EMI 대응을 위한 보드의 성능을 평가하기 위하여 공인 인정기관에서 실험한 결과, 각각의 주파수 대역에 따른 전자파 인증규격이 만족됨을 확인하였다.

• Earthquakes and Structures
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• 제17권4호
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• pp.373-385
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• 2019

In this article, different frequently adopted modeling aspects of linear and nonlinear dynamic soil-structure interaction (SSI) are studied on a pile-supported integral abutment bridge structure using the open-source platform OpenSees (McKenna et al. 2000, Mazzoni et al. 2007, McKenna and Fenves 2008) for a 2D domain. Analyzed approaches are as follows: (i) free field input at the base of fixed base bridge; (ii) SSI input at the base of fixed base bridge; (iii) SSI model with two dimensional quadrilateral soil elements interacting with bridge and incident input motion propagating upwards at model bottom boundary (with and without considering the effect of abutment backfill response); (iv) simplified SSI model by idealizing the interaction between structural and soil elements through nonlinear springs (with and without considering the effect of abutment backfill response). Salient conclusions of this paper include: (i) free-field motions may differ significantly from those computed at the base of the bridge foundations, thus put a significant bias on the inertial component of SSI; (ii) conventional modeling of SSI through series of soil springs and dashpot system seems to stay on the safer side under dynamic conditions when one considers the seismic actions on the structure by considering a fully coupled SSI model; (iii) consideration of abutment-backfill in the SSI model positively affects the general response of the bridge, as a result of large passive resistance that may develop behind the abutments.

• 한국환경보건학회지
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• 제28권2호
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• pp.117-129
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• 2002

Concentration of welding fumes and their components is known to be hazardous to welder and adjacent worker. To determine the generation rates of metals in fumes, $CO_2$ flux cored arc welding on stainless steel was performed in well designed fume collection chamber. Variables were different products of flux cored wire(2 domestic products and 4 foreign products) and input energy(low-, optimal- , high input energy). Mass of welding fumes was determined by gravimetric method(NIOSH 0500 method), and 17 metals were analysed by inductively coupled plasm-atomic emission spectroscopy(NIOSH 7300 method). Flux cored wire tube and flux were analysed by scanning electron microscopy to determine their metal composition. 17 metals were classified by their generation rates. Generation rates of iron, manganese, potassium and sodium were all above 50mg/min at optimal input energy level. Generation rates of chromium and amorphous silica were 25~50mg/min. At 1~25mg/min level, nickel, titanium, molybdenum, and aluminum were included. Copper, zinc, calcium, lead, magnesium, lithium, and cobalt were generated below 1 mg/min. Generation rates of metal components in fumes were influenced by input energy, types of flux cored wire. Flux cored wire was consisted of outer shell tube and inner flux. Iron, chromium, and nickel were the major components of outer tube. Flux contained iron, chromium, nickel, potassium, sodium, silica, and manganese. The use of flux cored wire can increase the hazards by increasing the amounts of fumes formed relative to that of solid wire. The reason might be the direct transfer of elements from the flux, since the flux is fine power. Ratio of metals to the fume of flux cored wire was lower than that of solid wire because non-metal components of flux were transferred. Total metal content of fumes in flux cored arc welding was 47.4(24.3~57.2) percent that is much lower than that of solid wire, 75.9 percent. We found that generation rates of iron, manganese, chromium and nickel, all well known to cause work related disease to welder, increased more rapidly with increasing input energy than those of fumes. To reduce worker exposure to fumes and hazardous component at source, further research is needed to develop new welding filler materials that decrease both the amount of fumes and hazardous components.

• 터널과지하공간
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• 제31권4호
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• pp.221-242
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• 2021

기존의 한국형 기준 처분시스템의 처분 효율을 높인 향상된 한국형 기준 처분시스템(Improved Korean Reference Disposal System, KRS⁺)의 열-수리-역학적 복합거동 성능평가를 위해 TOUGH2-MP/FLAC3D를 이용한 수치모델링 연구가 수행되었다. 사용후핵연료 처분 이후 방사성 붕괴열에 의해 처분시스템의 온도가 상승하고, 방사성 붕괴열이 빠르게 감소함에 따라 온도가 감소하여 최대 온도가 설계기준 온도인 100℃를 넘지 않는 것으로 나타났다. 완충재의 초기 포화도는 온도 상승으로 인한 공극수의 증발로 인해 감소하였다가 주변 암반으로부터 지하수가 유입되어 처분 약 250년 후 포화 상태에 이르렀다. 암반에서는 완충재와 암반의 흡입력의 차이로 인해 암반에서 완충재로 지하수가 유입되어 처분 직후 포화도가 감소하다가 이후 원계 암반으로부터 지하수가 유입되어 포화 상태에 도달했다. 처분시스템 내 열응력과 팽윤압 발생에 의한 주변 암반의 파괴 가능성을 평가하고자 모어-쿨롱 파괴기준식과 스폴링 강도를 사용하였다. KRS⁺ 처분시스템의 처분공의 간격을 감소시키면서 처분시스템의 열적 거동 변화를 확인하였는데, 처분공 간격이 5.5 m 이하에서는 완충재의 설계 기준 온도를 초과하게 된다. 다만, 벤토나이트 완충재 부피의 56.1%의 온도는 90℃ 이하로 유지되었다. 본 연구에서 사용한 수치해석 기법은 향후 응력 모델, 지온 경사 및 입력 물성을 변화시킨 다양한 조건에서의 처분시스템의 THM 복합거동 성능평가에 활용할 수 있을 것으로 판단된다.

• International Journal of Automotive Technology
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• 제4권1호
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• pp.47-55
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• 2003

The Center for Transportation Research at the Argonne National Laboratory (ANL) supports the DOE by evaluating advanced automotive technologies in a systems context. ha has developed a unique set of compatible simulation tools and test equipment to perform an integrated systems analysis project from modeling through hardware testing and validation. This project utilized these capabilities to demonstrate the trade-off in fuel economy and Oxides of Nitrogen (NOx) emissions in a so-called ‘pre-transmission’ parallel hybrid powertrain. The powertrain configuration (in simulation and on the dynamometer) consists of a Compression Ignition Direct Ignition (CIDI) engine, a Continuously Variable Transmission (CVT) and an electric drive motor coupled to the CVT input shaft. The trade-off is studied in a simulated environment using PSAT with different controllers (fuzzy logic and rule based) and engine models (neural network and steady state models developed from ANL data).

• 대한전자공학회논문지
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• 제5권1호
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• pp.13-25
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• 1968

고주파용 transistor를 이용한 광대역증폭기를 hybrid-π 등가회로를 이용하여 상세하게 분석하였다. 저주파와 고주파의 경우에 관한 해석을 하였고 이득과 대역폭및 입력 impedance와 출력 impedance를 주는 식을 유도하였다. 직렬궤환증폭기는 전압원으로 구동하여야하며 저저항부하로 동작시켜야 하고 병렬궤환증폭기는 전류원으로 구동하여야 하며 고저항부하로 동작시켜야 하는 것을 표시하였고 이 두가지 증폭단은 완충증폭단이나 변압기결합을 하지않고 결합시킬 수 있음을 표시하였다.

• 제어로봇시스템학회논문지
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• 제11권9호
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• pp.761-767
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• 2005

There exists a structural limit of 2WS cars that drivers would not like simultaneously to follow the desired path and attenuate moments resulting from disturbances because lateral acceleration and yaw rate are coupled inherently. In order to overcome the limit, the 4WS cars that have rear wheel steering as an additional input have been introduced. But the 4WS cars have disadvantages that much cost is required due to structural alteration, it is difficult to be used to the driving circumstances and tire performances are not efficient in nonlinear or large lateral acceleration ranges. Therefore, it is proposed that, in this paper, a robust controller is easy to apply to 2WS cars by using direct yaw moment, decouples lateral acceleration from yaw motion and is robust against disturbances and uncertainties of system parameters, and thus the proposed control method has the advantages of 4WS cars which can be achieved in 2WS cars.

• 한국초전도ㆍ저온공학회논문지
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• 제20권1호
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• pp.23-27
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• 2018

As the wireless power transfer (WPT) technology based on strongly resonance coupled method realizes large power charging without any wires through the air, there are advantages compared with the wired counterparts, such as convenient, safety and fearless transmission of power. From this reason, the WPT systems have started to be applied to the wireless charging for various power applications such as train, underwater ship, electric vehicle. This study aims for the effect and characteristics of different inserted resonance coil between Tx and Rx coils for charging system of superconducting magnetic levitation (MAGLEV) train. The transfer efficiency and effect are evaluated with helix type, rectangular type copper resonance coil, and HTS resonance coil under bulb and HTS magnet load, respectively. The input power is adapted with radio frequency (RF) power of 370 kHz below 500 W.