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排序方式: 共有624条查询结果,搜索用时 15 毫秒
101.
Kyeong Taek Jung Yong Gun Shul Masakazu Anpo Hiromi Yamashita 《Korean Journal of Chemical Engineering》1997,14(3):213-215
TS-1 zeolite film has been prepared by using nano sized TS-1 zeolite particles for the photocatalytic isomerization of cis-2-butene.
TS-1 zeolite film showed optical transparent property and the thickness of film was 0.7 μm. UV irradiation of TS-1 zeolite
film in the presence ofcis-2-butene leads to the photocatalytic isomerization ofcis-2-butene intotrans-2-butene at the temperature of 275 K. The yield oftrans- 2-butene was linearly increased with UV-irradiation time. 相似文献
102.
Gun Dae Lee Myung Jun Moon Jeong Hwan Park Seong Soo Park Seong Soo Hong 《Korean Journal of Chemical Engineering》2005,22(4):541-546
Catalytic activity, in conjunction with reaction mechanism, was studied in the methanation of CO and CO2 on three Raney Ni catalysts derived from different Ni-Al alloys using different leaching conditions. Main products were CH4 and CO2 in CO methanation, and CH4 and CO in CO2 methanation. Any other hydrocarbon products were not observed. Over all catalysts, CO methanation showed lower selectivity
to methane and higher activation energy than CO2 methanation. The catalyst derived from alloy having higher Ni content using more severe leaching conditions, namely higher
reaction temperature and longer extraction time, showed higher specific activity and higher selectivity to methane both in
CO and CO2 methanation. In CO and CO2 methanation on Raney Ni catalyst, catalytic activity was seen to have close relation with the activity to dissociate CO
This paper was presented at the 2004 Korea/Japan/Taiwan Chemical Engineering Conference held at Busan, Korea between November
3 and 4,2004. 相似文献
103.
A series of Zr(SO4)2/TiO2 catalysts were prepared by impregnation of powder TiO2 with an aqueous solution of zirconium sulfate. No diffraction line of zirconium sulfate was observed up to 30 wt%, indicating
good dispersion of Zr(SO4)2 on the surface of TiO2. The high catalytic activities of Zr(SO4)2/TiO2 for both 2-propanol dehydration and cumene dealkylation were related to the increase of acidity and acid strength due to
the addition of Zr(SO4)2. Zr(SO4)2/TiO2 containing 25% zirconium sulfate and calcined at 400 °C exhibited maximum catalytic activities for 2-propanol dehydration
and cumene dealkylation. The catalytic activities for these reactions were correlated with the acidity of catalysts measured
by the ammonia chemisorption method.
This paper is dedicated to Professor Hyun Ku Rhee on the occasion of his retirement from Seoul National University. 相似文献
104.
Direct Graphene Transfer and Its Application to Transfer Printing Using Mechanically Controlled,Large Area Graphene/Copper Freestanding Layer
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Jeongmin Seo Cheogyu Kim Boo Soo Ma Tae‐Ik Lee Jae Hoon Bong Joong Gun Oh Byung Jin Cho Taek‐Soo Kim 《Advanced functional materials》2018,28(26)
Direct graphene transfer is an attractive candidate to prevent graphene damage, which is a critical problem of the conventional wet transfer method. Direct graphene transfer can fabricate the transferred graphene film with fewer defects by using a polymeric carrier. Here a unique direct transfer method is proposed using a 300 nm thick copper carrier as a suspended film and a transfer printing process by using the polydimethylsiloxane (PDMS) stamp under controlled peeling rate and modulus. Single and multilayer graphene are transferred to flat and curved PDMS target substrate directly. With the transfer printing process, the transfer yield of a trilayer graphene with 1000 µm s?1 peeling rate is 68.6% of that with 1 µm s?1 peeling rate. It is revealed that the graphene transfer yield is highly related to the storage modulus of the PDMS stamp: graphene transfer yield decreases when the storage modulus of the PDMS stamp is lower than a specific threshold value. The relationship between the graphene transfer yield and the interfacial shear strain of the PDMS stamp is studied by finite‐element method simulation and digital image correlation. 相似文献
105.
Cyclic behaviour of post-Northridge WUF-B connections 总被引:1,自引:0,他引:1
The purpose of this study is to evaluate the cyclic behavior of post-Northridge Welded Unreinforced Flange-Bolted web (WUF-B) connections made using new notch tough welding materials and welding procedures, and a modified access hole. Since no WUF-B connection test results were found which satisfy the minimum design and detail requirements of the 2002 AISC Seismic Provisions for Structural Steel Buildings, this study made three full-scale test specimens of WUF-B connections according to the provisions. The main variable of the specimens was the ratio of the panel zone strength to the connected beam strength (panel zone strength ratio). Quasi-static cyclic testing was conducted. This study found that post-Northridge WUF-B connection specimens having a stronger panel zone experienced more significant slip between the bolted shear tab and the beam web. It was observed that the slip caused stress concentrations in and around the access hole, resulting in connection failure. The WUF-B connection specimen having the weakest panel zone did not, however, experience excessive slip between the bolted shear tab and beam web. Moreover, this WUF-B specimen could not achieve the required beam strength. This study observed that post-Northridge WUF-B connections with a panel zone strength ratio ranging from 0.9 to 1.6 provides a drift ratio exceeding 0.2. This drift ratio is required for satisfactory performance of the connections of Intermediate Moment Frames. Furthermore, this study proposed an analytical model for post Northridge WUF-B connections having different panel zone strength ratios. 相似文献
106.
Ca65Mg15Zn20 bulk metallic glass (BMG) samples of dimensions 3.2 mm × 7 mm × 125 mm were prepared using a low-pressure die casting technique. These samples were ground to produce tensile test pieces in compliance with ASTM E8-04. This work is the first reported study of the tensile behaviour of Ca65Mg15Zn20 BMG in the supercooled liquid region (105–120 °C). Two deformation conditions were used for testing: (i) constant strain rate testing from 10−3 to 10−4 s−1 and (ii) constant load testing using loads of 20–50 N applied to a tensile sample during heating at a constant rate of 5 °C s−1. The maximum elongation to failure in the BMG was in excess of 850% for constant load testing although, under isothermal testing conditions, most samples failed after 200% elongation. It is concluded that large superplastic elongations (>500%) during isothermal tensile straining is difficult in this alloy due to the onset of crystallization. 相似文献
107.
A nanoscale tubular carbon structure array was demonstrated as a mold for nanoimprint lithography (NIL), in which a vertically formed and hexagonally aligned nanoscale tubular carbon array was fabricated through carbon growth inside an anodic aluminum oxide (AAO) nanotemplate, followed by controlled chemical etching of the AAO layer. High density (over 10(10)?cm(-2)) of the nanoscale carbon pillars with their controlled diameters and protruded lengths was inversely replicated onto a UV-curable resist for the first time using the imprinting lithography technique. 相似文献
108.
Z. N. Sokolova D. A. Vinokurov I. S. Tarasov N. A. Gun’ko G. G. Zegrya 《Semiconductors》1999,33(9):1007-1009
Strongly strained InxGa1−x
As/In0.53Ga0.47As/InP heterostructures with indium content x=0.69−1.0 in the active region were investigated experimentally and theoretically. Two types of structures were obtained by
vapor-phase epitaxy from metalorganic compounds: 1) with isolated compression-strained quantum wells and 2) with self-organized
nanosize InAs clusters (quantum dots). The temperature dependence of the quantum radiation efficiency of samples with quantum
wells in the temperature range 77–265 K is characterized by T
0=43 K. One reason for the low value of T
0 is electron delocalization in the active region. The maximum radiation wavelength obtained in structures with quantum dots
is 1.9 μm at 77 K.
Fiz. Tekh. Poluprovodn. 33, 1105–1107 (September 1999) 相似文献
109.
Yoon KJ Lee MH Kim GH Song SJ Seok JY Han S Yoon JH Kim KM Hwang CS 《Nanotechnology》2012,23(18):185202
A tri-stable memristive switching was demonstrated on a Pt/TiO?/Pt device and its underlying mechanism was suggested through a series of electrical measurements. Tri-stable switching could be initiated from a device in unipolar reset status. The unipolar reset status was obtained by performing an electroforming step on a pristine cell which was then followed by unipolar reset switching. It was postulated that tri-stable switching occurred at the location where the conductive filament (initially formed by the electroforming step) was ruptured by a subsequent unipolar reset process. The mechanism of the tri-stable memristive switching presented in this article was attributed to the migration of oxygen ions through the ruptured filament region and the resulting modulation of the Schottky-like interfaces. The assertion was further supported by a comparison study performed on a Pt/TiO?/TiO(2-x)/Pt cell. 相似文献
110.
Kim WJ Kim BK Kim A Huh C Ah CS Kim KH Hong J Park SH Song S Song J Sung GY 《Analytical chemistry》2010,82(23):9686-9693
Cardiac markers in human serum with concentrations less than 0.1 ng/mL were analyzed by use of a guided-mode resonance (GMR) biosensor. Cardiac troponin I (cTnI), creatine kinase MB (CK-MB), and myoglobin (MYO) were monitored in the serum of both patients and healthy controls. Dose-response curves ranging from 0.05 to 10 ng/mL for cTnI, from 0.1 to 10 ng/mL for CK-MB, and from 0.03 to 1.7 μg/mL for MYO were obtained. The limits of detection (LOD) for cTnI, CK-MB, and MYO were less than 0.05, 0.1, and 35 ng/mL, respectively. Analysis time was 30 min, which is short enough to meet clinical requirements. Antibody immobilization and the hydrophilic properties of the guided-mode resonance filter (GMRF) surface were investigated by X-ray photoelectron spectroscopy (XPS) and by monitoring the peak wavelength shift and water contact angle (CA). Both assays used to evaluate the surface density of the immobilized antibodies, a sandwich enzyme-linked immunosorbent assay (ELISA) and a sandwich immunogold assay, showed that the antibodies were successfully immobilized and sufficiently aligned to detect the low concentration of biomarkers. Our results show that the GMR biosensor will be very useful in developing low-cost portable biosensors that can screen for cardiac diseases. 相似文献