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排序方式: 共有1620条查询结果,搜索用时 62 毫秒
1.
Young Been Kim Sung Hyeon Jung Dong Su Kim Nishad G. Deshpande Hee Won Suh Hak Hyeon Lee Ji Hoon Choi Ho Seong Lee Hyung Koun Cho 《Advanced functional materials》2021,31(38):2102439
Antimony triselenide (Sb2Se3) nanoflake-based nitrogen dioxide (NO2) sensors exhibit a progressive bifunctional gas-sensing performance, with a rapid alarm for hazardous highly concentrated gases, and an advanced memory-type function for low-concentration (<1 ppm) monitoring repeated under potentially fatal exposure. Rectangular and cuboid shaped Sb2Se3 nanoflakes, comprising van der Waals planes with large surface areas and covalent bond planes with small areas, can rapidly detect a wide range of NO2 gas concentrations from 0.1 to 100 ppm. These Sb2Se3 nanoflakes are found to be suitable for physisorption-based gas sensing owing to their anisotropic quasi-2D crystal structure with extremely enlarged van der Waals planes, where they are humidity-insensitive and consequently exhibit an extremely stable baseline current. The Sb2Se3 nanoflake sensor exhibits a room-temperature/low-voltage operation, which is noticeable owing to its low energy consumption and rapid response even under a NO2 gas flow of only 1 ppm. As a result, the Sb2Se3 nanoflake sensor is suitable for the development of a rapid alarm system. Furthermore, the persistent gas-sensing conductivity of the sensor with a slow decaying current can enable the development of a progressive memory-type sensor that retains the previous signal under irregular gas injection at low concentrations. 相似文献
2.
Storment C.W. Borkholder D.A. Westerlind V. Suh J.W. Maluf N.I. Kovacs G.T.A. 《Journal of microelectromechanical systems》1994,3(3):90-96
We present an all-aluminum MEMS process (Al-MEMS) for the fabrication of large-gap electrostatic actuators with process steps that are compatible with the future use of underlying, pre-fabricated CMOS control circuitry. The process is purely additive above the substrate as opposed to processes that depend on etching pits into the silicon, and thereby permits a high degree of design freedom. Multilayer aluminum metallization is used with organic sacrificial layers to build up the actuator structures. Oxygen-based dry etching is used to remove the sacrificial layers. While this approach has been previously used by other investigators to fabricate optical modulators and displays, the specific process presented herein has been optimized for driving mechanical actuators with relatively large travels. The process is also intended to provide flexibility for design and future enhancements. For example, the gap height between the actuator and the underlying electrode(s) can be set using an adjustable polyimide sacrificial layer and aluminum “post” deposition step. Several Al-MEMS electrostatic structures designed for use as mechanical actuators are presented as well as some measured actuation characteristics 相似文献
3.
Biodegradable multiblock poloxamers (BMPs) with gel duration of 8 h to several weeks were prepared by varying their molecular weights from 4000 to 40 000 g mol?1. The molecular weight of the BMP was controlled by changing the poloxamer to coupling agent ratio. Assuming a micelle packing model of the BMP gel, as in the case of a poloxamer gel, the micelle properties and critical gel concentration of BMPs were investigated on the basis of the scaling concept. The findings suggest that the control of molecular weight by hydrolyzable groups can be a facile approach to optimize the gel properties for biomedical applications. Copyright © 2005 Society of Chemical Industry 相似文献
4.
The ability to utilize fully automated flexible manufacturing systems (FMS) or develop reliable computer-integrated manufacturing (CIM) systems will depend on our ability to develop reliable and reusable software for large complex systems on a timely basis. To date, software design has not gone very far beyond the ad hoc trial-and-error stage. Consequently, the development of software is slow, expensive, unreliable, and unmanageable. The purpose of this paper is to provide a scientific basis for designing software. The approach used here is that of axiomatic design, which is based on two design axioms: the Independence Axiom and the Information Axiom. The axiomatic approach is based on the recognition of the following common elements in design: the existence of independent domains (i.e. the consumer domain, the functional domain, the physical domain, and the process domain); the need to map between various domains during the design process; the decomposition of the characteristic vectors (i.e. functional requirements, design parameters, and process variables) in their respective domains; the zig-zagging required between the domains for decomposition; and the need to satisfy the design axioms during the design process. The axiomatic approach discussed in this paper provides decision making tools for software design in addition to systematic means of knowledge and data representation, synthesis and analysis of software, and the construction of the module-junction structure diagram. 相似文献
5.
HJ Lee HK Ha MH Kim YK Jeong PN Kim MG Lee JS Kim DJ Suh SG Lee YI Min YH Auh 《Canadian Metallurgical Quarterly》1997,169(2):517-520
OBJECTIVE: The purpose of this study was to evaluate ERCP and CT findings of ectopic drainage of the common bile duct into the duodenal bulb. CONCLUSION: Although rare, the diagnosis of ectopic drainage of the common bile duct into the duodenal bulb is important to prevent inadvertent damage during biliary tract or gastric surgery and to clarify the cause of chronic peptic ulcers. 相似文献
6.
This paper proposes a dynamic Monte Carlo sampling method, called the conditional minimal cut set (COMICS) algorithm, where all arcs are not simulated at each trial and all minimal cut sets need not be given in advance. The proposed algorithm repeats simulating a minimal cut set composed of the arcs which originate from the (new) source node and reducing the network on the basis of the states of simulated arcs until the s-t connectedness is confirmed. We develop the importance sampling estimator, the total hazard estimator and the hazard importance sampling estimator which are all based on the proposed algorithm, and compare the performance of these simulation estimators. It is found that these estimators can significantly reduce the variance of the raw simulation estimator and the usual importance sampling estimator. 相似文献
7.
Microllular plastics are cellular polymers characterized by cell densities greater than 109 cells/cm3 and cells smaller than 10 μm. One of the critical steps in the continuous production of microcellular plastics is the promotion of high cell nucleation rates in a flowing polymer matrix. These high nucleation rates can be achieved by first forming a polymer/gas solution followed by rapidly decreasing the solubility of gas in the polymer. Since, in the processing range of interest, the gas solubility in the polymer decreases as the pressure decreases, a rapid pressure drop element, consisting of a nozzle, has been employed as a continuous microcellular nucleation device. In this paper, the effects of the pressure drop rate on the nucleation of cells and the cell density are discussed. The experimental results indicate that both the magnitude and the cell density are discussed. The experimental results indicate that both the magnitude and the rate of pressure drop play a strong role in microcellular processing. The pressure phenomenon affects the thermodynamic instability induced in the polymer/gas solution and the competition between cell nucleation and growth. 相似文献
8.
9.
Suh K.S. Damon D. Tanaka J. 《Dielectrics and Electrical Insulation, IEEE Transactions on》1995,2(1):1-11
Measurements of thermally stimulated currents were made on ionomer/polyethylene blends. The objective of this work was to study space charge formation in these materials. Two ionomers were compared; both ionomers contained methacrylic acid, neutralized by zinc in one and by sodium in the other. A large current peak centered near 60°C was observed in all blends and associated with the motion of space charges injected into the blends during poling. All blends accumulated large negative space charge concentrations. The approach to the equilibrium space charge distribution (negative and spatially uniform in all blends) is much more rapid in the blends containing the sodium ionomer than in the blends containing the zinc ionomer 相似文献