Low temperature hydrogen production by ethanol steam reforming over Pt-supported catalysts assisted by electric field

( Shuhei Ogo ),( Saori Sakurai ),( Naoya Tsunashima ),( Ryo Manabe ),( Yasushi Sekine ) 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

Catalytic ethanol steam reforming was investigated over Pt/CeO2 catalyst in an electric field at low temperature, and the effect of the electric field and controlling factors for the activity and selectivity were examined. With imposing the electric field, ethanol steam reforming proceeded at low temperature as 423K, at which temperature a conventional catalytic reaction hardly proceeded. Moreover, in the reaction with electric field, CH3CHO selectivity was low and CO+CO2 selectivity was higher than that in the conventional catalytic reaction, which indicated that steam reforming of acetaldehyde was promoted by imposing the electric field. The supported platinum worked as an active site and has great impact on the activity and selectivity for the ethanol steam reforming in the electric field. Conversion of ethanol and H2 yield drastically increased with imposing the electric field, and apparent activation energies for three elementary reactions (ethanol dehydrogenation, acetaldehyde decomposition, and acetaldehyde steam reforming) were lowered by the electric field. In-situ DRIFTS measurements revealed that the adsorbed ethanol forms reactive acetate species by imposing the electric field even at low temperature, which improved hydrogen selectivity. This process can produce hydrogen from bio-ethanol using less energy at low temperature, such as 423K with a high efficiency.

Effects of an alternating field in field-aided lateral crystallization process for low temperature poly-silicon

Choi, Sung-Hwa,Lee, Sung Bo,Kim, Young-Woong,Kim, Chang Kyung,Choi, Duck-Kyun Elsevier 2006 THIN SOLID FILMS - Vol.503 No.1

<P><B>Abstract</B></P> <P>The effect of the alternating field (AC voltage) instead of the static field (DC voltage) was investigated in the field-aided lateral crystallization process, which is one of the low temperature crystallization processes for the amorphous silicon films. Using a photolithography process, a 5-mm-wide bar-shaped photoresist (PR) pattern was formed on the <I>a</I>-Si. On the PR-patterned <I>a</I>-Si, a 2–3-nm-thick Cu catalyst layer was deposited by a DC sputtering, and then, the Cu layer on the PR pattern was lifted off. The silver electrodes were pasted at the opposite sides of the Cu-free bar pattern. Then, the patterned specimen was annealed at 500 °C in N<SUB>2</SUB> ambient for 5 h with the application of various AC fields (ranging from 1 to 5 V/cm) along with a DC field of 30 V/cm. As compared with the case of a DC field of 35 V/cm only, the specimen from a mixed field of 30 V/cm DC and 5 V/cm AC resulted in 1.5 times faster crystallization rate, regardless of experimental frequency values ranging from 10 Hz to 50 MHz. Presumably, the enhancement of the crystallization rate under the combined field is associated with an increase in the flux of the crucial diffusion species, Cu atoms, which govern the overall crystallization rate due to the effect by the AC field.</P>

CMOS Diodes under Cryogenic Temperature and High Magnetic Field Environment

Dongha Shim 대한전자공학회 2021 Journal of semiconductor technology and science Vol.21 No.5

This paper describes the DC characteristics of three CMOS diodes (PN junction diode, STI separated SBD (Schottky Barrier Diode) and Poly-gate separated SBD) under cryogenic temperature and high magnetic field environment. The temperature dependences of the devices were measured at the ambient temperatures of 300 K, 150 K, 77 K and 4.2 K. To understand the magnetic field dependence of the CMOS diodes at the temperatures, measurements were also performed under magnetic fields of 0 T, 2 T, 4 T and 6 T. The parameters including ideality factors, Schottky barrier heights, turn-on voltages and magnetoresistances (MR) of the diodes are analyzed under the various conditions. No abnormal behaviors are observed at the temperatures down to 4.2 K. The measured MRs vary depending on the diode current level. The maximum magnetoresistance of 35% is observed in the PN junction diode under the temperature of 4.2 K and horizontal magnetic field of 6 T. The MR quadratically increases as the magnetic field increases in the high injection region. The diodes show a higher magnetoresistance under a lower temperature and higher magnetic field. The results show the feasibility of CMOS diode circuits under the cryogenic temperature and high magnetic field environment.

Resistance Characteristics of Thin Films and Contacts in CMOS under Cryogenic Temperature and High Magnetic Field Environment

Dongha Shim,Deokgi Kim 대한전자공학회 2024 Journal of semiconductor technology and science Vol.24 No.2

This paper investigates the resistance characteristics of thin film and contact structures in a 90-nm CMOS process under cryogenic temperature and high magnetic field environment for the first time. The temperature dependences of the test structures were measured at the ambient temperatures of 300 K, 150 K, 77 K and 4.2 K, respectively. To understand the magnetic field dependence of the test structures at the temperatures, measurements were also performed under the magnetic fields of 0 T, 2 T, 4 T and 6 T, respectively. The sheet resistances and the contact resistances are analyzed along with the magnetoresistances under the various conditions. All test structures showed a decreasing sheet resistance or contact resistance as the temperature decreases. The sheet resistance of a thin films with a lower value drops faster as the temperature decreases. The metal thin film and the metal-to-n+ contact showed the maximum resistance change of 89.5% and 35%, respectively, over the temperature range. Meanwhile, negligible magnetoresistances are observed except the metal thin film, which shows a higher magnetoresistance under a lower temperature and higher magnetic field. The maximum magnetore-sistance of the metal thin film is measured to be 10.4% for the horizontal magnetic field of 6 T at 4.2 K.

하절기 도심과 외곽지의 열특성 비교 관측

정임수(Jung Im-Soo),최동호(Choi Dong-Ho),이부용(Lee Bu-Yong) 한국태양에너지학회 2009 한국태양에너지학회 학술대회논문집 Vol.2009 No.11월

This study is about heat island as one of the urban climate variation factors in urbanized modern society, which compared and observed the thermal characteristics both the downtown location and the outskirt site in summer. The diurnal air temperature range at each point is 12.6℃ in the downtown location and 14.3 ℃ in the outskirt site, so, it was found that the diurnal air temperature range in the outskirt site was l.7 ℃ higher than in the downtown location. There was 20 minutes difference to reach the highest temperature between globe temperature and air temperature in the downtown location, however, the time spent to reach the highest temperature between globe temperature and air temperature in the outskirt site was the same. When we compared the globe temperature between the downtown location and outskirt site, we found that the temperature in the outskirt site was lower than in the downtown location after sunset due to the sudden temperature drops, although the exposed time to insolation in the outskirt site is longer. The average of globe temperature difference on the sample days was 1.1℃, the average of surface temperature difference on the sample days was l.0℃, and the average of air temperature difference on the sample days was 2.0 ℃ Thus, it was found that the average of air temperature difference was higher than the average of globe temperature and the average of surface temperature. The result of this study is that the urban environment factors have more effect on the air temperature difference than globe temperature and surface temperature.

현장수준의 축산폐수처리에 있어서 계절별 농도 및 온도변화에 따른 분해반응계수 및 온도보정계수의 산정

박석환 한국환경보건학회 1996 한국환경보건학회지 Vol.22 No.2

This study was performed to calculate the degration rate coefficient, operating parameters to meet the effluent standards, and the temperature adjustment coefficients to each parameter of pollution by seasonal variation of concentration and temperature of influent in livestock wastewater treatment by sequencing batch reactor process in field scale. The followings are the conclusions that were derived from this study. 1. In the field, temperature of livestock wastewater in reactor was 20.3$\circ$C in summer and 6.0$\circ$C in winter. The ratio of BOD:TKN: T-P in influent was 100:80:7. BOD loadings in winter and spring were 0.26 and 0.43 kg $BOD/m^3$ day, respectively. Those in summer and fall were 0.25 and 0.13 kg $BOD/m^3$ day, respectively. 2. The degradation rate coefficient for TKN was larger in summer and fall in which temperature was high than that in which temperature was high than that in winter and spring in which concentration was high. On the contrary, the phosphorus uptake rate was larger in winter and spring than that in summer and fall. 3. The hydraulic retention time in winter and spring was longer than that in summer and fall. Especially, in order to meet the standard for TKN of 120 mg/l in winter in which temperature of wastewater was 6.0$\circ$C, as the MLSS concentration was increased from 4, 000 to 7, 000 mg/l, the hydraulic retention time was increased from 212 to 121 hours. But, in order to shorten that less than 121 hours for the economical wastewater treatment, countermeasure to increase temperature of wastewater in the reactor should be considered. 4. the temperature adjustment coefficients for BOD, $COD_{Mn}$, TKN and T-P were 1.0241, 1.0225, 1.0541 and 1.0495, respectively. Namely, the treatment of TKN was most sensitively affected by temperature. For the purpose of the effective removal of nitrogen and phosphorus which are sensitive to temperature, it is necessary to keep the temperature of livestock wastewater more than 20$\circ$C which is the temperature of it in summer.

지형이 복잡한 집수역의 소규모농장에 맞춘 기상서비스의 실현가능성

윤진일 ( Jin I. Yun ) 한국농림기상학회 2015 한국농림기상학회지 Vol.17 No.4

우리나라 농촌은 지형이 복잡하고 소규모 농장이 많아 농업기상서비스 개선을 위해서는 먼저 기상청 종관예보의 규모축소가 필요하다. 지형기후학에 근거한 공간정보기술을 이용하여 기상청의 기온예보자료 가운데 0600과 1500 LST자료를 선정된 집수역에 대해 30 m급의 국지규모로 상세화하고, 14개 관측소의 실측기온자료를 2013년부터 2014년까지 수집하여 비교하였다. 그 결과 0600 LST기온의 경우 집수역 가운데 고도가 낮은 곳에서, 1500 LST 기온의 경우 계곡의 서향 및 남향 사면에서 정확도가 크게 개선되는 것을 확인하였다. 상세화 한 기온실황자료를 이용하여 지역 내 소규모 농장을 대상으로 하는 시범서비스를 시작하였으며 농장 맞춤 기상정보를 제공하고 있다. 예컨대 이 서비스시스템은 기온자료를 토대로 작물의 발육단계를 추정하고, 발육단계별 최저기온에 따른 서리해 발생 관계식에 의해 내일 아침 예보기온의 서리위험 여부를 판정한다. 만약 서리위험도가 미리 설정된 기준을 넘으면 농장주의 휴대폰으로 대응지침과 함께 서리해 경보를 발송하여 피해를 예방할 수 있도록 도와준다. An adequate downscaling of synoptic forecasts is a prerequisite for improved agrometeorological service to rural areas in South Korea where complex terrains and small farms are common. In this study, geospatial schemes based on topoclimatology were used to scale down the Korea Meteorological Administration (KMA) temperature forecasts to the local scale (~30 m) across a rural catchment. Then, using these schemes, local temperatures were estimated at 14 validation sites at 0600 and 1500 LST in 2013/2014 and were compared with the observations. The estimation errors were substantially reduced for both 0600 and 1500 LST temperatures when compared against the uncorrected KMA products. The improvement was most notable at low lying locations for the 0600 temperature and at the locations on west- and south-facing slopes for the 1500 LST temperature. Using the downscaled real-time temperature data, a pilot service has started to provide the field-specific weather information tailored to meet the requirements of small-scale farms. For example, the service system makes a daily outlook on the phenology of crop species grown in a given field using the field-specific temperature data. When the temperature forecast is given for next morning, a frost risk index is calculated according to a known relationship of phenology and frost injury. If the calculated index is higher than a pre-defined threshold, a warning is issued and delivered to the grower``s cellular phone with relevant countermeasures to help protect crops against frost damage.

Temperature Field and Cooling Rate of Laser Cladding with Wire Feeding

Kim, Jae-Do,Peng, Yun The Korean Society of Mechanical Engineers 2000 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.14 No.8

Temperature field and cooling rate are important parameters to influence the properties of clad layer and the heat affected zone. In this paper the temperature field and cooling rate of laser cladding are studied by a two-dimensional time-dependent finite element model. Experiment has been carried out by Nd:YAG laser cladding with wire feeding. Research results indicate that at the beginning of cladding, the width and depth of melt pool increase with cladding time. The cooling rate is related to position, cladding time, cladding speed, and preheating temperature. The temperature near melt pool changes rapidly while the temperature far from melt pool changes slowly. With the increase of cladding time, cooling rate decreases. The further the distance from the melt pool, the lower the temperature and the slower the cooling rate. The faster the cladding speed, the faster the cooling rate. The higher the preheating temperature, the slower the cooling rate. The FEM results coincide well with the experiment results.

Temperature-Dependent Opacity of the Gate Field Inside MoS₂ Field-Effect Transistors

Ji, Hyunjin,Ghimire, Mohan Kumar,Lee, Gwanmu,Yi, Hojoon,Sakong, Wonkil,Gul, Hamza Zad,Yun, Yoojoo,Jiang, Jinbao,Kim, Joonggyu,Joo, Min-Kyu,Suh, Dongseok,Lim, Seong Chu American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.32

<P>The transport behaviors of MoS<SUB>2</SUB> field-effect transistors (FETs) with various channel thicknesses are studied. In a 12 nm thick MoS<SUB>2</SUB> FET, a typical switching behavior is observed with an <I>I</I><SUB>on</SUB>/<I>I</I><SUB>off</SUB> ratio of 10<SUP>6</SUP>. However, in 70 nm thick MoS<SUB>2</SUB> FETs, the gating effect weakens with a large off-current, resulting from the screening of the gate field by the carriers formed through the ionization of S vacancies at 300 K. Hence, when the latter is dual-gated, two independent conductions develop with different threshold voltage (<I>V</I><SUB>TH</SUB>) and field-effect mobility (μ<SUB>FE</SUB>) values. When the temperature is lowered for the latter, both the ionization of S vacancies and the gate-field screening reduce, which revives the strong <I>I</I><SUB>on</SUB>/<I>I</I><SUB>off</SUB> ratio and merges the two separate channels into one. Thus, only one each of <I>V</I><SUB>TH</SUB> and μ<SUB>FE</SUB> are seen from the thick MoS<SUB>2</SUB> FET when the temperature is less than 80 K. The change of the number of conduction channels is attributed to the ionization of S vacancies, which leads to a temperature-dependent intra- and interlayer conductance and the attenuation of the electrostatic gate field. The defect-related transport behavior of thick MoS<SUB>2</SUB> enables us to propose a new device structure that can be further developed to a vertical inverter inside a single MoS<SUB>2</SUB> flake.</P> [FIG OMISSION]</BR>

Field Mapping and Automated Shimming of an HTS Magnet by “Internal” Active Shim Coils Located in the Bore of the Magnet

Min Cheol Ahn,Jeongwoo Jang,Seungyong Hahn,Young-Gyun Kim,Haigun Lee Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3

<P>In order to obtain the target field homogeneity of a nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) magnet, commonly used are active shim coils, i.e., axial and radial, that typically locate radially outside of the magnet. In a high-temperature superconducting (HTS) magnet, however, we reported a “strong” hysteresis in the field-to-current ratio of an external (placed radially outside the HTS magnet) active shim coil by the screening-current-induced fields (SCFs). This nonlinear behavior of an external active shim due to the SCF is one of the major technical challenges to achieve the target field homogeneity of an HTS NMR or MRI magnet. In this paper, we constructed and operated active shim coils, i.e., two axial ( Z1 and Z2) and two radial (X and Y) , that were installed inside of an HTS magnet to investigate effectiveness of internal shim coils. The HTS magnet, wound with GdBCO coated conductors, consists of ten double pancakes. With the active shim coils, a customized field mapping and shimming system was constructed, which consists of a 3-D field mapper, a field analysis software package, and a set of power supplies to control the shim coils. A pre-shim field error of 953 ppm at a 10-mm-diameter cylinder was improved to 464 ppm after iterative automated shimming using the internal shim coils. The results demonstrate that the internal shim coils are effective to eliminate the SCF-oriented field errors, both radial and axial, which was practically impossible for the external shim coils.</P>