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排序方式: 共有475条查询结果,搜索用时 281 毫秒
1.
M. Kroon E. Andreasson E. Persson Jutemar V. Petersson L. Persson M. Dorn P.A.T. Olsson 《Experimental Mechanics》2018,58(1):75-86
Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters. 相似文献
2.
We consider a two-echelon inventory system with a number of non-identical, independent ‘retailers’ at the lower echelon and a single ‘supplier’ at the upper echelon. Each retailer experiences Poisson demand and operates a base stock policy with backorders. The supplier manufactures to order and holds no stock. Orders are produced, in first-come first-served sequence, with a fixed production time. The supplier therefore functions as an M/D/1 queue. We are interested in the performance characteristics (average inventory, average backorder level) at each retailer. By finding the distribution of order lead time and hence the distribution of demand during order lead time, we find the steady state inventory and backorder levels based on the assumption that order lead times are independent of demand during order lead time at a retailer. We also propose two alternative approximation procedures based on assumed forms for the order lead time distribution. Finally we provide a derivation of the steady state inventory and backorder levels which will be exact as long as there is no transportation time on orders between the supplier and retailers. A numerical comparison is made between the exact and approximate measures. We conclude by recommending an approach which is intuitive and computationally straightforward. 相似文献
3.
4.
R. T. Olsson H. E. Bair V. Kuck A. Hale 《Journal of Thermal Analysis and Calorimetry》2004,76(2):367-377
Thin films of 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexane carboxylate were UV irradiated (1.1 J cm-2) under isothermal conditions ranging from 0 to 50°C. Under these conditions the polymerization advanced quickly but only
to a conversion level of less than 10% before the reaction rate slowed by more than an order of magnitude. This drop off in
rate was not caused by the glass transition temperature, T
g, reaching or exceeding the reaction temperature, T
rxn, since the epoxide's T
g remained at least 40°C below T
rxn. Raising the sample temperature above 60°C caused a sharp increase in the conversion level. At 100°C conversion exceeds 80%
and the ultimate T
g approaches 190°C. The addition of 10 mass% 1,6-hexanediol, HD, to the epoxy caused the conversion at room temperature to
quintuple over the level obtained without the alcohol present. The heat liberated from this alcohol epoxy blend during cure
on a UV conveyor belt system caused the sample's temperature to increase by about 100°C above ambient whereas the epoxy alone
under these conditions only experienced a modest temperature rise of about 26°C. If the amount of HD in the blend is increased
above 10% the heat of reaction at 23°C decreases due to HD being trapped in a nonreactive crystalline phase. Boosting reaction
temperatures above 50°C melts the HD crystals and yields significantly improved conversion ratios. As the level of alcohol
blended with the epoxy is raised its ultimate T
g is lowered and when the concentration of alcohol in the blend nears 30 mass%T
g drops below room temperature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
An immobiline DryStrip application method enabling high-capacity two-dimensional gel electrophoresis 总被引:5,自引:0,他引:5
Sabounchi-Schütt F Aström J Olsson I Eklund A Grunewald J Bjellqvist B 《Electrophoresis》2000,21(17):3649-3656
In the field of proteomics the need to detect low-abundance cellular components, such as regulatory proteins, is of critical importance. Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) is one of the most commonly used separation tools for these biological investigations. In this paper we report an alternative micropreparative 2-D PAGE sample application method, called the "paper bridge loading" method. This method makes it possible to apply a larger sample volume to commercially available immobilized pH gradient (IPG) strips. The Vh products required for focusing are only marginally longer than those used in analytical experiments. The method was compared to traditional cup loading and in-gel rehydration. With 18 cm long narrow-range Immobiline DryStrip pH 4.5-5.5, the "paper bridge" method allowed the application of 10 mg human plasma proteins compared to 3 mg with traditional loading methods. The corresponding figures using Escherichia coli sample was found to be 6 mg and less than 2 mg, respectively. The paper bridge method also showed the best results in terms of spot resolution and separation of high molecular weight proteins. 相似文献
6.
Bo Olsson György Marko-Varga Lo Gorton Roger Appelqvist Gillis Johansson 《Analytica chimica acta》1988
A selective and sensitive flow-injection system for the determination of myo-inositol (hexahydroxycyclohexane) is described. Inositol dehydrogenase, IDH, lactate dehydrogenase, LDH, and lactate oxidase, LOD, are co-immobilized on porous glass and used in a packed-bed enzyme reactor. myo-Inositol reacts to produce an equivalent amount of hydrogen peroxide, which oxidizes hexacyanoferrate(II) to hexacyanoferrate(III) in a second reactor containing immobilized peroxidase. The hexacyanoferrate(III) is then detected amperometrically at 0 mV vs. SCE in a flow-through detector. The system responds linearly to injected samples of myo-inositol (25 μl) in the concentration range 1–300 μM. The maximum throughput was 90 samples per hour. The IDH/LDH/LOD reactor was stable for at least 5 weeks. 相似文献
7.
8.
Background
Phosphatidylethanol (PEth) is an abnormal phospholipid formed slowly in cell membranes by a transphosphatidylation reaction from phosphatidylcholine in the presence of ethanol and catalyzed by the enzyme phospholipase D. PEth in blood is a promising new marker of ethanol abuse depending on the high specificity and sensitivity of this marker. None of the biological markers used in clinical routine at the present time are sensitive and specific enough for the diagnosis of alcohol abuse. 相似文献9.
The conformations and dynamic processes in two bicyclophanes have been analysed on the basis of temperature-dependent 1H NMR spectra. Both bicyclophanes are suggested to have a lowest-energy conformation of D3 symmetry in which the substituents at all ethylene bridges are gauche+ (or gauche?) oriented. The interconversion of the mirror image conformers of each bicyclophane equilibrates the two hydrogens in each methylene group, the barriers being ca 36 and 37 kJ mol?1, respectively, as determined by line-shape analysis. 相似文献
10.