http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Aggregate Effects on γ-ray Shielding Characteristic and Compressive Strength of Concrete
Jeong-Hwan Oh,Young-Bum Mun,Jae-Hyung Lee,Hyun-Kook Choi,Sooseok Choi 한국방사성폐기물학회 2016 방사성폐기물학회지 Vol.14 No.4
일반골재인 자갈, 모래와 중량골재인 산화 슬래그 및 자철광을 이용하여 5 종류의 콘크리트를 제작하여 감마선 차폐특성과압축강도를 살펴보았다. 골재는 평균적인 크기에 따라 비교적 작은 크기의 잔 골재와 큰 크기의 굵은 골재로 구분하여 사용하였다. 실험 결과 산화 슬래그 잔 골재와 굵은 골재를 사용한 콘크리트가 일반 골재만을 이용하여 배합한 콘크리트 시편보다 137Cs 감마선에 대해 2% 향상된 감쇠계수인 0.371 cm-1을 기록하였다. 각 시편들의 단위중량을 측정한 결과 자철광잔 골재와 산화 슬래그 굵은 골재로 배합한 조건의 단위중량이 가장 높은 3,175 kg·m-3이었다. 산화슬래그를 잔 골재와 굵은 골재로 배합한 조건의 단위중량은 3,052 kg·m-3으로 최대 단위중량 조건보다 123 kg·m-3 낮았지만 감쇠계수는 오히려0.012 cm-1 향상되었다. 골재들의 화학성분 분석결과 산화 슬래그는 자철광에 비해 마그네슘의 비율은 낮고 칼슘의 비율은높아 구성에 있어서 차이를 보였다. 따라서 산화슬래그 만을 골재로 사용한 경우 자철광을 잔 골재로 사용한 경우보다 단위중량은 낮았지만 마그네슘과 비교하여 원자번호가 큰 칼슘의 비율이 높아서 감마선 차폐성능이 향상된 것으로 생각된다. 중량골재가 배합된 모든 시편들은 일반 골재를 이용한 콘크리트보다 압축강도가 높았고, 산화슬래그와 자철광의 잔 골재만을사용한 경우 4주 양생 후 압축강도가 일반 콘크리트에 비해 45% 향상된 50.2 MPa을 기록하였다. We observed the γ-ray shielding characteristics and compressive strength of five types of concrete using general aggregates and high-weight aggregates. The aggregates were classified into fine aggregate and coarse aggregate according to the average size. The experimental results obtained an attenuation coefficient of 0.371 cm-1 from a concrete with the oxidizing slag sand (OSS) and oxidizing slag gravel (OSG) for a γ-ray of 137Cs, which is improved by 2% compared with a concrete with typical aggregates of sand and gravel. In the unit weight measurement, a concrete prepared by iron ore sand (IOS) and OSG had the highest value of 3,175 kg·m-3. Although the unit weight of the concrete with OSS and OSG was 3,052 kg·m-3, which was lower than the maximum unit weight condition by 123 kg·m-3, its attenuation coefficient was improved by 0.012 cm-1. The results of chemical analysis of aggregates revealed that the magnesium content in oxidizing slag was lower than that in iron ore, while the calcium content was higher. The concrete with oxidizing slag aggregates demonstrated enhanced γ-ray shielding performance due to a relatively high calcium content compared with the concrete with OSS and OSG in spite of a low unit weight. All sample concretes mixed with high-weight aggregates had higher compressive strength than the concrete with typical sand and gravel. When OSS and IOS were used, the highest compressive strength was 50.2 MPa, which was an improvement by 45% over general concrete, which was achieved after four weeks of curing.
Hyeokjun Kang,Jeong-Hwan Oh,Daeun Choi,Hidemasa Takana,Sooseok Choi 한국진공학회(ASCT) 2021 Applied Science and Convergence Technology Vol.30 No.6
Presently, the use of bituminous coals as a heating source in the cement industry has led to an increase in carbon dioxide emissions. In this study, the thermal flow characteristics inside a waste combustion chamber constituting multiple thermal plasma jets was numerically analyzed. The waste combustion process was applied as a heating source to produce the raw materials of cement. The design and operation of the waste combustion process were optimized through numerical analysis using the magnetohydrodynamics and computational fluid dynamics code. The thermal flow characteristics inside the waste combustion chamber were numerically analyzed in accordance with adjusting the chamber width, injection angle of the torch, and combustion air temperature. As a result, the temperature in the range of 1,600–2,200 K was widely distributed at the center of the chamber. The optimized conditions are as follows: 400 mm chamber width, 20° injection angle, and 1,000 K combustion air temperature. The waste combustion chamber constituting multiple thermal plasma jets was constructed based on the numerical results. It was concluded that plasma jets generate a sufficient temperature to treat waste plastics.
Design of Next Generation Amplifiers Using Nanowire FETs
Sotoudeh Hamedi-Hagh,Sooseok Oh,Ahmet Bindal,Dae-Hee Park 대한전기학회 2008 Journal of Electrical Engineering & Technology Vol.3 No.4
Vertical nanowire SGFETs (Surrounding Gate Field Effect Transistors) provide full gate control over the channel to eliminate short channel effects. This paper presents design and characterization of a differential pair amplifier using NMOS and PMOS SGFETs with a 10㎚ channel length and a 2㎚ channel radius. The amplifier dissipates 5㎼ power and provides 5㎔ bandwidth with a voltage gain of 16, a linear output voltage swing of 0.5V, and a distortion better than 3% from a 1.8V power supply and a 20aF capacitive load. The 2nd and 3rd order harmonic distortions of the amplifier are -40㏈m and -52㏈m, respectively, and the 3rd order intermodulation is -24㏈m for a two-tone input signal with 10㎷ amplitude and 10㎓ frequency spacing. All these parameters indicate that vertical nanowire surrounding gate transistors are promising candidates for the next generation high speed analog and VLSI technologies.
Design of a High Performance Patch Antenna for GPS Communication Systems
Sotoudeh Hamedi-Hagh,Joseph Chung,Sooseok Oh,Ju-Ung Jo,Noh-Joon Park,Dae-Hee Park 대한전기학회 2009 Journal of Electrical Engineering & Technology Vol.4 No.2
This paper presents the design of a patch antenna for GPS portable devices. The antenna is designed to operate at L1 band on an FR4 PCB with a thickness of 1.6㎜, a dielectric constant of 3.8 and two metallization layers. The antenna has a dimension of 49㎜×36㎜ and operates at 1.5754㎓ with a return loss of |-36|㏈ and a measured bandwidth of 250㎒.
Thermal Plasma Synthesis of Ceramic Nanomaterials
Tae-Hee Kim,Jeong-Hwan Oh,Minseok Kim,Seung-Hyun Hong,Sooseok Choi 한국진공학회(ASCT) 2020 Applied Science and Convergence Technology Vol.29 No.5
Many studies have been conducted on thermal plasma synthesis of ceramic nanomaterials by direct current and radio frequency thermal plasma. Furthermore, numerous researchers have attempted to develop processes to commercialize the thermal plasma process for practical applications. These processes can continuously fabricate beneficial high-value ceramic nanomaterials in a high enthalpy environment. In this review, several thermal plasma synthetic processes are described for different plasma sources and precursor types. Current understanding of the formation process of nanomaterials is also explained. In addition, the research trend for ceramic nanomaterials produced by thermal plasma is described and the limitations and challenges are also discussed.
Hye Young Ko,Jeong-Hwan Oh,Subin Yang,Sooseok Choi 한국진공학회(ASCT) 2022 Applied Science and Convergence Technology Vol.31 No.1
We performed a synthesis of metal-boride nanoparticles, which can shield both gamma rays and neutrons, and investigated the radiation shielding performance of the material. Titanium and nickel boride nanoparticles were synthesized in a triple thermal plasma jet system using titanium (Ti), nickel (Ni), and amorphous boron (a-B). The average sizes of the titanium boride and nickel boride were 46.3 and 31.4 nm, respectively. In the titanium boride, the TiB₂ phase was the major crystal structure with TiB as a minor phase, and the peak of the starting materials could not be observed. On the other hand, the nickel boride indicated a major crystal structure of NiB with an Ni peak observed from X-ray diffraction graphs. The synthesized powders were applied as a coating material to shield the radiation. The shielding performance of the coating material made with synthesized powder was analyzed using <SUP>137</SUP>Cs source (662 keV). The attenuation coefficient of the nickel boride and titanium boride was 0.246 and 0.197 cm<SUP>-1</SUP>, respectively. Boron-rich boride is stable when confronting neutron and other types of radiation. Therefore, synthesized metal-boride nanoparticles can be used as substitutes for heavy metals, which become radioactive on account of neutron exposure.
Design of UHF CMOS Front-ends for Near-field Communications
Sotoudeh Hamedi-Hagh,Maryam Tabesh,Sooseok Oh,Noh-Joon Park,Dae-Hee Park 대한전기학회 2011 Journal of Electrical Engineering & Technology Vol.6 No.6
This paper introduces an efficient voltage multiplier circuit for improved voltage gain and power efficiency of radio frequency identification (RFID) tags. The multiplier is fully integratable and takes advantage of both passive and active circuits to reduce the required input power while yielding the desired DC voltage. A six-stage voltage multiplier and an ultralow power voltage regulator are designed in a 0.13 μm complementary metal-oxide semiconductor process for 2.45 GHz RFID applications. The minimum required input power for a 1.2 V supply voltage in the case of a 50 Ω antenna is -20.45 dBm. The efficiency is 15.95% for a 1 MΩ load. The regulator consumes 129 nW DC power and maintains the reference voltage in a 1.1% range with V<sub>dd</sub> varying from 0.8 to 2 V. The power supply noise rejection of the regulator is 42 dB near a 2.45 GHz frequency and performs better than -32 dB from 100 Hz to 10 GHz frequencies.