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排序方式: 共有639条查询结果,搜索用时 31 毫秒
31.
This paper presents the synthesis and characterization of three new Y-based high temperature-superconducting compounds having relatively higher transition temperature T c compared with that of the Y-123, Y-124, and Y-247. The electrical resistivity measurements indicate the onset critical temperatures as high as 98 K. Atomic compositions of these new Y-Ba-Cu-O superconductors are Y2Ba3Cu5.2O x , Y2Ba5Cu9O x , and YBa4Cu5O x . The X-ray analysis has shown that they have a similar crystalline structure as Y-123 phases. 相似文献
32.
Tolga Taner Mecit Sivrioğlu Hüseyin Topal Ahmet Selim Dalkılıç Somchai Wongwises 《Sadhana》2018,43(3):42
This study presents a case study of energy management in a sugar factory in Turkey. The main idea of the study is to analyse energy consumption, the quantity of material production, and figure out a suitable energy efficiency for the case study of a sugar factory subsequently. Firstly, a material production and energy consumption audit were performed for the sugar factory. Secondly, energy efficiency was calculated from the energy data. The SPSS (Statistical Package for the Social Sciences) statistical software was used to ensure the accuracy of the data. The factory’s energy consumption was calculated as 43,590.25 toe (tons of oil equivalent) over the last year. These results were used for CUSUM (Cumulative Sum Deviation Method) graphics. This research poses the consumption of energy, cost of energy and the relationship between energy usage and material production of sugar. The unit of energy cost was 688.22 [$/toe] for the last year. This result showed that the factory decreased the unit of energy by optimisation. The results indicated that the investigated sugar factory should pay attention to the energy management issue in order to comply with the Energy Efficiency of Turkish Law and Directives. 相似文献
33.
Ugur Topal 《Journal of Superconductivity and Novel Magnetism》2012,25(5):1485-1488
In the present study, we investigate influence of HCl-etching on magnetic parameters of B2O3-doped M-type barium ferrites. Our studies have shown that magnetization parameters; the remanence magnetization M r and the specific magnetization M s at 1.5?T, increase significantly with HCl-etching. The best magnetic parameters were observed in the sample of 0.1?wt% B2O3-doped and HCl-washed one after calcination at 1000?°C (M r =34.9?emu/g, M s =0.63.3?emu/g). Increments up to 50% in magnitudes could be achieved with HCl washing. Exchange interactions between particles were also examined by Wohlfarth model. It was observed that magnetizing-like interactions between particles become stronger but ,on the other hand, demagnetizing-like interactions becomes weaker with HCl-etching. 相似文献
34.
Nanostructured thin films of lead sulfide have been synthesized by a new electrochemical approach based on the underpotential deposition (UPD) of Pb and S from the saturated solution of PbS containing excess of PbS particles as a source of Pb2+ and S2− at various temperatures.We have demonstrated that this new electrochemical route is a simple method with several advantages, including better control of the growth conditions and a one-step process to obtain the nanostructures of PbS. Scanning probe microscopy studies indicate that the growth of PbS nanofilms follows a two-dimensional layer-by-layer growth kinetics at the beginning of electrodeposition but a three-dimensional growth dominates after the formation of the first few layers. The results of morphological and structural investigations reveal that PbS nanostructures grown by this method are single-crystalline in cubic structure and have a preferential orientation along the [2 0 0] direction. The optical absorption spectra of PbS nanostructures show the blue-shift with respect to those of the bulk counterpart, which are attributed as quantum-size effect. 相似文献
35.
面向对象知识模型的构建 总被引:1,自引:0,他引:1
介绍了面向对象技术设计知识库模式的方法。强调知识模型构建的重点是在表达、验证及推导设计限制条件,而不是传统意义上的数据。设计概念仍沿用类表示,分3个部分:决策参数、表现参数及限制条件。决策参数是从限制条件中抽象出来的数据,代表设计对象的属性或状态;表现参数是对决策参数的计算和度量;限制条件规范及限制表现参数的域值,可视为类不变量,每个类对象都必需满足之。设计概念之间的相互联系则用关联来阐述。传统面向对象技术考虑的是数据在关联中的横向、纵向传递,提出关联类以捕获数据,同时增加关联的限制条件作为关联不变量。在继承和整件-部件关联的基础上,增加了特性关联。模型构建构建以汽车制造中模板设计为例加以说明。 相似文献
36.
Vehicle routing problem (VRP) is an important and well-known combinatorial optimization problem encountered in many transport logistics and distribution systems. The VRP has several variants depending on tasks performed and on some restrictions, such as time windows, multiple vehicles, backhauls, simultaneous delivery and pick-up, etc. In this paper, we consider vehicle routing problem with simultaneous pickup and delivery (VRPSPD). The VRPSPD deals with optimally integrating goods distribution and collection when there are no precedence restrictions on the order in which the operations must be performed. Since the VRPSPD is an NP-hard problem, we present a heuristic solution approach based on particle swarm optimization (PSO) in which a local search is performed by variable neighborhood descent algorithm (VND). Moreover, it implements an annealing-like strategy to preserve the swarm diversity. The effectiveness of the proposed PSO is investigated by an experiment conducted on benchmark problem instances available in the literature. The computational results indicate that the proposed algorithm competes with the heuristic approaches in the literature and improves several best known solutions. 相似文献
37.
Insulation applications of nonwovens has become increasingly important in the construction and automotive industries since the late 1990s. Besides, recycling and reusing fibrous waste becomes one of the most important raw materials of nonwovens to promote effective use of resources recently. On the other hand, metals are now being increasingly replaced by thermoplastics for housing commercial equipment, due to flexibility, light weight, and low cost for electromagnetic shielding purposes. In this study, we design nonwoven insulation panels containing copper wires with different intensity and length to provide electromagnetic wave protection by using recycled textiles. The method is simple, the material is cheaper, and more importantly, the whole material can be produced by using only waste materials. The electromagnetic shielding characteristics of the panels were measured and discussed. The experimental results indicated that the variation in wire length and amount affects the electromagnetic (EM) shielding property. With this method, the products with electromagnetic shielding effect in certain areas can be developed. In particular, there is a big potential for electromagnetic shielding applications in wide bandwidth, such as 1125–2925 MHz. 相似文献
38.
Homogenous, crack free iron oxide films are prepared by the sol–gel spin coating technique from a solution of iron iso-propoxide and isopropanol. The films were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-visible (UV–Vis) spectroscopy and cyclic voltammetry (CV). XRD of the films showed that they had an amorphous structure. The optical constants refractive index (n) and extinction coefficient (k) were measured by scanning spectrometer in the wavelength range of 390–990 nm. The n and k values were found n =2.3±0.01 and k =0.2±0.002 at 650 nm. The electrochemical behavior investigated in 0.5 M LiClO4 propylene carbonate (PC) electrolyte-CV examinations showed good rechargeability of the Li+/e− insertion extraction process beyond 300 cycles. Spectroelectrochemistry showed that these films exhibit weak cathodic coloration in the spectral range of 350–800 nm. 相似文献
39.
Smart structures and their applications on active vibration control: Studies in the Department of Aerospace Engineering, METU 总被引:1,自引:0,他引:1
Melin Sahin Fatih Mutlu Karadal Yavuz Yaman Omer Faruk Kircali Volkan Nalbantoglu Fatma Demet Ulker Tarkan Caliskan 《Journal of Electroceramics》2008,20(3-4):167-174
This work presents the theoretical and experimental studies conducted in Aerospace Engineering Department of Middle East Technical
University on smart structures with particular attention given to the structural modelling characteristics and active suppression
of in-vacuo vibrations. The smart structures considered in these analyses are finite and flat aluminium cantilever beam-like
(called as smart beam) and plate-like (called as smart fin) structures with surface bonded lead–zirconate–titanate patches.
Finite element models of smart beam and smart fin are obtained. Then the experimental studies regarding open loop behaviour
of the structures are performed by using strain gauges and laser displacement sensor to determine the system models. Further
studies are carried out to obtain H
∞ and μ-synthesis controllers which are intended to be used in the suppression of free and forced vibrations of the smart structures.
It is observed that satisfactory attenuation levels are achieved and robust performance of the systems in the presence of
uncertainties is ensured. In that respect a comparative study involving H
∞ and sliding mode controls is also conducted. Recently, the studies involving aerodynamic loading are also gathering pace. 相似文献
40.
Electrospun nylon 6,6 nanofibers functionalized with cyclodextrins for removal of toluene vapor
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Functional nylon 6,6 nanofibers incorporating cyclodextrins (CD) were developed via electrospinning. Enhanced thermal stability of the nylon 6,6/CD nanofibers was observed due to interaction between CD and nylon 6,6. X‐ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy studies indicated the existence of some CD molecules on the surface of the nanofibers. Electrospun nylon 6,6 nanofibers without having CD were ineffective for entrapment of toluene vapor from the environment, whereas nylon 6,6/CD nanofibrous membranes can effectively entrap toluene vapor from the surrounding by taking advantage of the high surface‐volume ratio of nanofibers with the added advantage of inclusion complexation capability of CD presenting on the nanofiber surface. The modeling studies for formation of inclusion complex between CD and toluene were also performed by using ab initio techniques. Our results suggest that nylon 6,6/CD nanofibrous membranes may have potential to be used as air filters for the removal of organic vapor waste from surroundings. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41941. 相似文献