• 한국전자파학회논문지
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• 제14권2호
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• pp.148-156
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• 2003

본 논문은 3 GPP 규격을 바탕으로 한 W-CDMA UE 시스템의 RF 성능관련 내용을 다루고 있으며 송수신 파라미터를 RF 성능관점에서 유출하였다. 최적의 UE성능을 얻기 위해 송신기에 대해서는 ACLR, EVM, 피크코드영역 에러, 스펙트럼 방사 마스크, 주파수 오차 안정도, 송신전력제어 범위와 같은 성능 요구사항을 고찰하였고 수신기에 대해서는 수신 감도, 블록킹 특성, 잡음지수, 인접채널 선택도, 수신 ACC 범위 등이 고려되었다. 요구된 파라미터들을 근거로 UE RF 트랜시버를 구현하였고 실제 측정 시나리오에 따라서 RF 성능평가를 수행하였다.

• 동력기계공학회지
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• 제13권4호
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• pp.11-17
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• 2009

This paper deals with the effects of pulsating flow on volumetric efficiency, which may be generated during the gas exchange procedure, due to piston motion, valve event on intake and exhaust stroke and unsteady flow of turbocharger of a three-cylinder four stroke turbo-charged diesel engine. Consequently, volumetric efficiency affects significantly the engine performance; torque characteristics, fuel economy and further to emission and noise level. As the expansion ratio became larger the engine speed varies and torque increases, the pressure pulsation in an exhaust gas pipe acts as an increasing factor of intake air charging capacity totally. The phase and amplitude of pressure pulsation in the intake system only affects volumetric efficiency favorably, if it is well matched and tuned effectively to the engine. Thus, to verify the exact phase and amplitude of the pressure variation is the ultimate solution for the air-flow ratio assessment in the intake stroke. Some experimental results of pressure diagrams in the intake pipe and gas-flow of turbine in-outlet are presented, under various kinds of operating condition.

• International Journal of Automotive Technology
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• 제2권2호
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• pp.39-45
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• 2001

Hydrogen is seen as one of the important energy vectors of the next century. Hydrogen as a renewable energy source, provides the potential for a sustainable development particularly in the transportation sector. Hydrogen driven vehicles reduce both local as well as global emissions. The laboratory of transporttechnology (University of Gent) converted a GM/Crusader V-8 engine for hydrogen use. Once the engine is optimised, it will be built in a low-floor midsize hydrogen city bus for public demonstration. For a complete control of the combustion process and to increase the resistance to backfire (explosion of the air-fuel mixture in the inlet manifold), a sequential timed multipoint injection of hydrogen and an electronic management system is chosen. The results as a function of the engine parameters (ignition timing. injection timing and duration, injection pressure) we given. Special focus is given to topics related to the use of hydrogen as a fuel: ignition characteristics (importance of electrode distance), quality of the lubricating oil (crankcase gases with high contents of hydrogen), oxygen sensors (very lean operating conditions), noise reduction (configuration and length of inlet pipes). The advantages and disadvantages of a power regulation only by the air to fuel ratio (as for diesel engines) against a throttle regulation (normal gasoline or gas regulation) are examined. Finally the goals of the development of the engine are reached: power output of 90 kW, torque of 300 Nm, extremely low emission levels and backfire-safe operation.

• 한국환경과학회지
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• 제19권7호
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• pp.807-818
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• 2010

The study is about variations in Carbonyl compounds concentration within apartment buildings according to pre-residence and residence. We consecutively investigated indoor air pollutants in 120 households in 6 cities at pre-residence and residence. Carbonyl compounds were collected using the 2,4-DNPH cartridge and were analyzed using HPLC. The carbonyls concentration of indoor air in the new apartments before occupation measured formadlehyde($76.0\;{\mu}g/m^3$), acetone($85.9\;{\mu}g/m^3$), acetaldehyde($13.8\;{\mu}g/m^3$). The carbonyls concentration of indoor air in the new apartments after occupation measured formadlehyde($233.1\;{\mu}g/m^3$), acetone($128.9\;{\mu}g/m^3$), acetaldehyde($29.8\;{\mu}g/m^3$), respectively. As a result, the mean concentration of carbonyl compounds within the pre-occupancy stage was lower than those of residence.

• KIEAE Journal
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• 제10권6호
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• pp.55-66
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• 2010

The government is enacted "Housing Performance Grading Indication System" from qualitative housing supply policy and performance of housing under the background of looking for new plan to secure good housing stock and housing performance. This system consists of 5 main performance section, 14 performance categories and 20 detailed performance items. 5 main performance parts are sound insulation related grading(Light-weight impact sound insulation, heavy-weight floor impact sound insulation, noise emission in bathroom, airborne sound insulation for wall between units), Long-life housing related grading(flexibility, remodeling & maintenance, durability), environment related grading(landscape, indoor air quality and ventilation, energy performance), Living environment related grading(common resident facilities such as playground and consideration for the socially underprivileged such as the aged), Fire fire prevention grading(fire fire prevention). The purpose of this research is to analyze characteristics and assessment results of 20 detailed performance items on "Housing Performance Grading Indication System" which was enforced 240 cases from Jan 9th, 2006 to Sep 30th, 2010. The analysis of approval condition of detailed performance items will be important comments for understanding the current domestic level and development of technology.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2427-2429
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• 2005

OLED in the spotlight of display market has advantages of low power driving, self-emission and fast response. But it has disadvantages of inefficient luminescence and high power consumption. Most of PM(passive Matrix) DC-DC converters in common use is using voltage divider. This voltage divider type has some difficulties of suitable electric device selection for voltage division and of the stabilized output due to feedback current trimming. Therefore, noise analysis and power solution in OLED are important technologies having an effect on electric characteristics. In this dissertation, we have obtained the stable output by using digital signals in multi-channel DC-DC converter, the profit of power consumption reduction of driving source and economical efficiency in the PCB board size.

• 대한방사선기술학회지:방사선기술과학
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• 제45권5호
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• pp.423-431
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• 2022

The purpose of this study is to present objective information in applying 3D printing technology for PET/CT (Positron Emission Tomography/Computed Tomography) performance evaluation and use it as a basic research that can be applied to various purposes in the future. Phantoms were manufactured with step wedge of ABS(Acrylonitrile Butadiene Styrene) and ACR(Acrylic acid) material. The counts for each ROI(Region of Interest) were analyzed through image acquisition in PET/CT. And the variation rate of counts and CNR(Contrast Noise Ratio) was evaluated. In the counts analysis, the effect of thickness occurred. In addition, in the variation rate analysis, the thickness setting of steps wedge 4 to 5 levels should be considered first. These results minimize quantitative and qualitative changes in the phantom manufactured based on 3D printing, and enable more stable PET/CT performance evaluation. Based on 3D printing in PET/CT, various phantoms are expected to be produced in the future. If the characteristics of each material are considered and applied through the basic research such as this research, the result of the phantom manufactured through 3D printing can be more meaningful and will be used in a wide range.

• Communications for Statistical Applications and Methods
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• 제29권6호
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• pp.709-719
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• 2022

Recently, as the importance of environmental protection has emerged, interest in new and renewable energy is also increasing worldwide. In particular, the solar energy sector accounts for the highest production rate among new and renewable energy in Korea due to its infinite resources, easy installation and maintenance, and eco-friendly characteristics such as low noise emission levels and less pollutants during power generation. However, although climate prediction is essential since solar power is affected by weather and climate change, solar radiation, which is closely related to solar power, is not currently forecasted by the Korea Meteorological Administration. Solar radiation prediction can be the basis for establishing a reasonable new and renewable energy operation plan, and it is very important because it can be used not only in solar power but also in other fields such as power consumption prediction. Therefore, this study was conducted for the purpose of improving the accuracy of solar radiation. Solar radiation was predicted by a total of three weather variables, temperature, humidity, and cloudiness, and solar radiation outside the atmosphere, and the results were compared using various models. The CatBoost model was best obtained by fitting and comparing the Boosting series (XGB, CatBoost) and RNN series (Simple RNN, LSTM, GRU) models. In addition, the results were further improved through Time series cross-validation.

• 대한기계학회논문집B
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• 제36권2호
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• pp.211-216
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• 2012

화석 에너지 고갈에 따라 에너지의 합리적 이용이 요구되면서 가용 에너지를 고려한 열에너지의 계단식 활용이 적극적으로 검토되고 있다. 이와 같은 배경에서 1 kW 급의 스털링 엔진을 기반으로 한 열병합발전 시스템이 분산 에너지 시스템을 구축하는 단위로서 제안되었다. 1 kW 의 용량은 가정용에 적합하며, 가정에서 활용하기 위해서는 공간을 작게 차지하도록 하면서도 소음과 유해가스의 배출을 철저하게 차단해야 한다. 이러한 조건들을 충족시키며 효율이 높은 시스템을 개발하기 위하여 슬롯 형태의 예혼합 버너를 제안하였고 버너의 연소 특성을 파악하기 위하여 일련의 실험을 수행하였다. 본 연구에서는 화염의 형상을 촬영하여 연소부하 및 공기비에 따른 연소 모드를 관찰하였고 배가스를 분석하여 연소 모드에 따른 배기 특성을 연구하였다.

• 재활복지공학회논문지
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• 제10권4호
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• pp.273-278
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• 2016

청각선별에서 반응 역치는 검사 환경 잡음, 청각기관 생리적 특성, 과도한 음원 노출 등에 따라 다르게 나타난다. 이 연구 목적은 청각선별을 통과한 소아의 주파수별 가청역치에 대한 정보를 획득하는데 있다. 연구 대상은 언어치료센터와 지역아동센터에 다니는 3.3세부터 16.3세($9.01{\pm}2.52$) 사이의 110명으로 하였고, 이들의 소아 청각 선별 결과를 후향적으로 분석하였다. 청각선별은 고막운동성계측(Tympanometry), 등골근반사(acoustic reflex threshold), 자동화 이음향방사(automated otoacoustic emission), 순음청각선별(pure tone screening)을 시행하였다. 대상자들은 모두 청각선별 정상 기준에 포함되었다. 주파수별 가청역치 차이는 반복측정 분산분석 하였다. 결과: 가청역치 평균은 500, 1,000, 2,000, 4,000 Hz의 순서로 우측 귀 $16{\pm}6.49$, $11.5{\pm}4.79$, $6.86{\pm}4.99$, $5.95{\pm}6.65$ dB HL, 좌측 귀 $15.68{\pm}6.01$, $9.95{\pm}5.24$, $5.72{\pm}5.21$, $5.63{\pm}7.04$ dB HL로 각각 관찰되었다. 주파수 사이에는 500Hz와 1,000, 2,000, 4,000 Hz(p=.000), 1,000과 2,000, 4,000 Hz(p=.000)로 유의한 차이가 있었다.