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排序方式: 共有348条查询结果,搜索用时 31 毫秒
1.
Food Science and Biotechnology - MV was reported to have beneficial effects in ameliorating insulin resistance in db/db mice, but the intrinsic mechanisms for glucose homeostasis are unclear. This... 相似文献
2.
Novel floating-patch micro-electro-mechanical system (MEMS) antennas are proposed for millimetre-wave applications. The floating-patch MEMS antennas are fabricated on a high resistivity silicon (HRS) substrate using surface micromachining technology. Simulation and experimental results for reflection coefficients and radiation patterns are presented. 相似文献
3.
Measurements of non-methane hydrocarbons (NMHC) were performed at the entrance and exit of the Sangdo tunnel to estimate emission
factors (EF) of NMHC from vehicles in May 2000. About 50 species were analyzed by a combined GC/FID and GC/MS system. Ethylene
was the most abundant compound, followed by n-butane and acetylene, respectively. Based on the measurement data, the real
world vehicular EF in Seoul was estimated. The highest EF value was 89.8 mg (veh-mile)-1 for n-butane, followed by ethylene and toluene. 相似文献
4.
Sang Pyo Kim 《Gravitation and Cosmology》2014,20(3):193-196
Particle production in de Sitter space provides an interesting model for understanding the curvature effect on Schwinger pair production by a constant electric field or the Schwinger mechanism on de Sitter radiation. For that purpose, we employ the recently introduced complex analysis method in which the quantum evolution in complex time explains pair production via the geometric transition amplitude and gives the pair-production rate as a contour integral. We compare the result from the contour integral with that of the phase-integral method. 相似文献
5.
Solid extraction of caffeine and theophylline from green tea by molecular imprinted polymers 总被引:1,自引:0,他引:1
Dexian?Wang Seung?Pyo?Hong Kyung?Ho?RowEmail author 《Korean Journal of Chemical Engineering》2004,21(4):853-857
This paper involves a feasibility study on using molecular imprinted polymers as the sorbent materials in solid phase extraction
for caffeine and theophylline from green tea. Two kinds of MIPs, with caffeine-theophylline mixture and pentoxifylline-theophylline
mixture as the templates respectively, MAA as the monomer, EDMA as the crosslinker and ATBN as the initiator, were applied
to this purpose. Mixture solution of caffeine and theophylline (1 Μg/ ml in acetonitrile) was applied to the solid extraction
cartridges following a load, wash and elute procedure with acetonitrile, methanol, methanol-acetic acid (90/10, v/v) as the
solvents, respectively. This solid phase extraction protocol was applied for extraction of caffeine and theophylline from
green tea. Comparison between the results obtained with the MIPs cartridges and a traditional C18 reversed-phase cartridge was made. It showed that the MIP-based sorbent on the solid phase extraction was comparable with
that of C18 material. HPLC analysis using a C18 column (5 Μm, 250× 4.6 mm from Rstech corporation), methanol: water (60 :40, v/v) as the mobile phase at a flow rate of 0.6
ml/min was applied for the quantitative determination. 相似文献
6.
This study was conducted to investigate the effects of reaction pH condition and hardener type on the reactivity, chemical structure, and molecular mobility of urea–formaldehyde (UF) resins. Three different reaction pH conditions, such as alkaline (7.5), weak acid (4.5), and strong acid (1.0), were used to synthesize UF resins, which were cured by adding four different hardeners (ammonium chloride, ammonium sulfate, ammonium citrate, and zinc nitrate) to measure gel time as the reactivity. FTIR and 13C‐NMR spectroscopies were used to study the chemical structure of the resin prepared under three different reaction pH conditions. The gel time of UF resins decreased with an increase in the amount of ammonium chloride, ammonium sulfate, and ammonium citrate added in the resins, whereas the gel time increased when zinc nitrate was added. Both FTIR and 13C‐NMR spectroscopies showed that the strong reaction pH condition produced uronic structures in UF resin, whereas both alkaline and weak‐acid conditions produced quite similar chemical species in the resins. The proton rotating‐frame spin–lattice relaxation time (T1ρH) decreased with a decrease in the reaction pH of UF resin. This result indicates that the molecular mobility of UF resin increases with a decrease in the reaction pH used during its synthesis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2677–2687, 2003 相似文献
7.
In this paper, a new analytical method for solving stable crack propagation problems in a ductile panel with a row of cracks, is presented. The main purpose of the present study is to estimate the maximum load carrying capacity of such panels accurately. The so called Elastic Plastic Finite Element Alternating Method (Pyo et al. (1994) was extended to account for the propagating cracks. The crack propagation algorithm utilizes the analytic crack solution to release the stresses ahead the crack tip. The T
inf
sup*
integral is employed as the crack extension criterion. This integral parameter accounts for the near tip stress-strain singularity and its critical values for crack propagation can be extracted from the P-a curve of single cracked specimen case. The present method can be applied to the problems of the fuselage skin of aging airplanes, in which a row of cracks develop (MSD; Multiple Site Damage) from rivet holes. The load carrying capacity of such damaged structure reduces by a considerable amount. In order to predict the behavior near the critical load, one must account for plastic deformation, if the material is ductile. Furthermore, the maximum load carried by the structure is often reached after some amount of crack propagation. In this paper, a series of analyses have been conducted and their results compare with the available experimental data. 相似文献
8.
An elastic-plastic finite element alternating method for analyzing wide-spread fatigue damage in aircraft structures 总被引:2,自引:0,他引:2
In this paper, a new analytical technique to study the effect of wide-spread fatigue damage in ductile panels is presented. The main purpose of the study is to develop an efficient methodology to predict the maximum load carrying capacity of panels with cracks. The problem arises especially in the fuselage skin of aging airplanes, in which cracks initiate from a row of rivet holes. This problem is known as Multi Site Damage (MSD) in aging aircraft. It is very important to estimate the load carrying capacity. Usually, the approach based on elastic fracture mechanics may overestimate the load capacity. It is very important for the aircraft structure with MSD to estimate the load carrying capacity of such damaged structures. Approaches based on elastic fracture mechanics often lead to a considerable error. In this paper, the Elastic Finite Element Alternating Method (EFEAM) has been extended to the case of elastic-plastic fracture of panels with MSD cracks. In EFEAM, analytical solutions to crack problems in an infinite plate are employed. In this study, we adopted an analytical solution for a row of cracks in an infinite panel. Furthermore, the plastic deformation is accounted for, by using the initial stress algorithm. The T
inf
sup*
integral is employed for the fracture criterion. The methodology developed in the present study can be called as Elastic-Plastic Finite Element Alternating Method (EPFEAM) for MSD problems. A series of studies on the maximum load capacity of panels with a row of cracks has been conducted.The support of this work by the Federal Aviation Administration through a grant to the Center of Excellence for Computational Modeling of Aircraft Structures, at the Georgia Institute of Technology, is sincerely appreciated. 相似文献
9.
Continuous generation of hydrogel beads and encapsulation of biological materials using a microfluidic droplet-merging channel 总被引:1,自引:0,他引:1
In this paper, we describe a method for encapsulation of biomaterials in hydrogel beads using a microfluidic droplet-merging
channel. We devised a double T-junction in a microfluidic channel for alternate injection of aqueous fluids inside a droplet
unit carried within immiscible oil. With this device, hydrogel beads with diameter <100 μm are produced, and various solutions
containing cells, proteins and reagents for gelation could merge with the gel droplets with high efficiency in the broad range
of flow rates. Mixing of reagents and reactions inside the hydrogel beads are continuously observed in a microchannel through
a microscope. By enabling serial injection of each liquid with the dispersed gel droplets after they are produced from the
oil-focusing channel, the device simplifies the sample preparation process, and gel-bead fabrication can be coupled with further
assay continuously in a single channel. Instantaneous reactions of enzyme inside hydrogel and in-situ formation of cell-containing
beads with high viability are demonstrated in this report. 相似文献
10.
The effect of Pd on the growth rate of metal-induced lateral crystallization (MILC) from Ni seed and the electrical properties of thin-film transistors (TFTs) fabricated on the films crystallized by MILC were investigated. When the Pd metal is placed on the amorphous-silicon/Ni-seed layer, the MILC growth rate is two to three times faster than that of conventional Ni-MILC, without any degradation of TFTs. These results were explained by a stress that is generated by the formation of Pd2Si 相似文献