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排序方式: 共有249条查询结果,搜索用时 15 毫秒
1.
The graft copolymerization of methacrylic acid onto poly(ethylene terephthalate) fibers, by the aid of benzoyl peroxide, have been investigated. The graft yield increased up to 85°C, and then decreased with the further increase in temperature. The maximum graft yield was obtained at benzoyl peroxide concentration of 4.0 × 10?3 mol/L. The increase in the concentration of monomer was found to increase the graft yield. The change in the graft yield was followed by the experiments carried out using different water/solvent mixtures. Also, the change in the properties of polye (thylene terephthalate) fibers grafted with methacrylic acid such as moisture regain, density, and diameter were investigated. 相似文献
2.
Given an undirected network with positive edge costs and a positive integer , the minimum-degree constrained minimum spanning tree problem is the problem of finding a spanning tree with minimum total cost such that each non-leaf node in the tree has a degree of at least . This problem is new to the literature while the related problem with upper bound constraints on degrees is well studied. Mixed-integer programs proposed for either type of problem is composed, in general, of a tree-defining part and a degree-enforcing part. In our formulation of the minimum-degree constrained minimum spanning tree problem, the tree-defining part is based on the Miller–Tucker–Zemlin constraints while the only earlier paper available in the literature on this problem uses single and multi-commodity flow-based formulations that are well studied for the case of upper degree constraints. We propose a new set of constraints for the degree-enforcing part that lead to significantly better solution times than earlier approaches when used in conjunction with Miller–Tucker–Zemlin constraints. 相似文献
3.
Filiz Yasar Mahlicli Sacide Alsoy Altinkaya 《Journal of materials science. Materials in medicine》2013,24(2):533-546
This study intends to improve blood compatibility of polysulfone (PSF) membranes by generating a nonthrombogenic surface through heparin immobilization. To achieve this task, the support membrane prepared from a blend of PSF and sulfonated polysulfone (SPSF) was modified with layer by layer (LBL) deposition of polyethyleneimine (PEI) and alginate (ALG) and heparin blended with ALG was immobilized only on the outermost surface of the LBL assembly. The results have shown that the adsorption of human plasma proteins and platelet activation on the LBL modified membranes decreased significantly compared with the unmodified PSF and PSF-SPSF blend membranes. Furthermore, blending ALG with a small amount of heparin remarkably prolonged the APTT values of heparin free PEI/ALG coated membranes. It is envisaged that the use of a blend of HEP and ALG only in the terminating layer of the LBL assembly can be an economical and alternative modification technique to create nonthrombogenic surfaces. 相似文献
4.
Polat Cevik Ibrahim Kocaman Abdullah S. Akgul Barbaros Akca 《Journal of Intelligent and Robotic Systems》2013,70(1-4):595-608
At the last two decades, according to UAVs concepts and technological advances, there have been lots of unimagined improvements. Nowadays there are serious works and researches about the usage of UAVs in military operations at electronic warfare (EW) missions. But most of the work on UAV platforms is based upon the advantages of a single, big, expensive, and non-expendable platform. In this study, to get rid off the disadvantages of a stand alone platform a new concept is developed consisting of multiple UAVs with smaller dimensions, at a cheaper price and a wider coverage. According to clarify the study, firstly the EW and RADAR systems and then the swarm UAV concepts are explained. In this manner the current and previous works are pointed out and then the use of the swarm UAVs for EA in military operations is stated. Objectively, the swarm UAV concept’s advantages and some outstanding challenges to the intra-theater space have been put forward regarding the information mentioned above. As a result it is considered that the swarm UAV systems will be tasked important EW missions in the future operation theatres, as soon as the technical handicaps are solved. 相似文献
5.
Gulum Sumnu Filiz Koksel Serpil Sahin Arzu Basman & Venkatesh Meda 《International Journal of Food Science & Technology》2010,45(1):87-93
The objective of this study was to determine the effects of different concentrations of xanthan and guar gums and their blends on staling of gluten-free rice cakes baked in microwave-infrared combination oven (MW–IR) and to compare the cakes with conventionally baked ones. Gums were added at concentrations of 0.3% and 1.0%. For preparation of gum blend, 0.5% xanthan gum was mixed with 0.5% guar gum. In order to understand the staling behaviour of cakes, cakes were stored at 22 ± 2 °C for 120 h. Xanthan-guar gum blend decreased hardness, weight loss, retrogradation enthalpy and the change in setback viscosity values of cakes during storage for both types of ovens as compared to control formulation. It was found that oven type was a significant factor in affecting staling parameters of gluten-free cakes. 相似文献
6.
Electrical and interface state properties of the borontrifluoride doped poly(3‐aminoacetophenone)/p‐Si junction have been investigated by current‐voltage and impedance spectroscopy methods. Al/p‐Si/P3APBF3/Aldiode indicates a nonideal behavior with electrical parameters (n = 3.53, ?B = 0.82 eV, and Rs = 1.48 kΩ), which result from the interfacial layer, series resistance, and resistance of the organic semiconductor. The obtained barrier height value of the Al/p‐Si/P3APBF3/Aldiode is higher than that of the conventional Al/p‐Si (?B = 0.58 eV) Schottky diode. The interface state density of the diode was of the order of 1.05× 1012 eV?1 cm?2. It is evaluated that the barrier height and interface state density values of the diode are modified using the boron trifluoride doped poly (3‐aminoacetophenone) organic semiconductor. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers 相似文献
7.
Although ohmic heating is used as an alternative heating method for liquid egg products commercially, there is a lack of information
on the change of rheological properties and fluid dynamics characteristics of ohmically heated liquid whole egg in the literature.
The change of rheological behaviour of the ohmically heated liquid whole egg, across a temperature range of 4–60 °C, was determined
by using a concentric rotational viscometer. The ohmic heating was conducted by applying the voltage gradient (20 V/cm) at
50 Hz. The temperature dependency of the electrical conductivity of liquid egg was linear (R
2 = 0.999). The rheological behaviour was found to be shear thinning since power law model had higher regression coefficient
and lower χ
2 and root mean square error values than Newtonian model. Ohmically heated liquid whole egg exhibited higher degree of thixotropic
index indicating the occurrence of the protein denaturation at 60 °C. The flow behaviour of liquid whole egg in the continuous
ohmic heating system was predicted as laminar (GRe range of 87.59–538.87) for the mass flow rate range of 0.0056–0.0166 kg/s.
The friction factors and pressure losses in the system in those mass flow rates were also assessed. The result of this study
will give necessary information on flow characteristics of liquid whole egg for the modelling, designing and the scaling up
of the continuous ohmic heating systems for pasteurisation of liquid egg products. 相似文献
8.
This paper deals with the performance evaluation of ohmic cooking process by applying exergy analysis. Cylindrically shaped ground beef samples with different fat contents (2%, 9% and 15%) were used as the test material being cooked. The cooking process was conducted at three different voltage gradients (20, 30 or 40 V/cm) up to 80 °C. The effects of voltage gradient applied and the initial fat content of sample on the energy efficiency, exergy efficiency, exergy loss and improvement potential were investigated. The energy and exergy efficiency values for ohmic cooking process at the voltage gradients between 20 and 40 V/cm were found to be in the range of 0.69–0.91% and 63.2–89.2%, respectively. It was determined that the system should have been improved energetically especially for samples having high initial fat contents cooked at the low voltage gradients, since improvement potential values predicted were highest at this conditions. 相似文献
9.
In this work, the multiplayer perceptron (MLP) and radial basis function (RBF) neural networks in their simplest forms are employed in function approximation for highly nonlinear and complex analysis and synthesis of the most commonly used planar RF/microwave transmission lines, that is, microstrip lines, coupled microstrip lines, and basic and shielded coplanar‐waveguides. Since the analysis and synthesis processes for these systems have “one‐to‐one mapping” relations with each other, a forward model is defined for the analysis process for all these types of the planar transmission lines; on the other hand, a reverse model is also considered for the synthesis of the same lines. This reverse model is realized by swapping some of the inputs/outputs in the analysis model, and training the neural networks accordingly. Both MLP and RBF types of neural models are applied to the four widely used anisotropic and isotropic dielectric materials: PTFE/microstrip glass, RT/Duroid 6006, alumina and gallium arsenide. The results are shown to agree very well with the targets. A low‐pass filter with 30‐dB attenuation frequency at 3.5 GHz on an alumina substrate is designed by the use of a neural‐network synthesis and its resulting performance agrees well with the one using analytical formulas for the synthesis. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. 相似文献
10.
Metin Ergeneman Turgut
zakta Filiz Karaosmano lu H. Ertu rul Arslan 《Petroleum Science and Technology》1997,15(7):667-683
Vegetable oils have chances to be used in Diesel engines as alternative fuels contributing to the solution of some agricultural, environmental and economical problems. Direct use of them has some technical problem yet but as blended fuels with diesel fuel or esters they have places on the application area. In this paper the effect of the compression ratio on ignition delay is investigated in an ASTM-CER engine working with four different types of vegetable oil of Turkish origin (sunflower, corn, soybean, and olive oil) blended with grade No.2-D diesel fuel at a ratio of 20/80 (v/v) and the results are compared with baseline diesel fuel. Longer ignition delay periods have generally been obtained for blend fuels ranking from olive oil to sunflower oil as compared to diesel fuel. 相似文献