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Laser ablative shaping of plastic optical components for phase control   总被引:1,自引:0,他引:1  
A new scheme for phase control of optical components with laser ablation has been developed. One can ablate the surface shape of optical plastic material coated on a glass plate by using 193-nm laser light to control the transmission wave front. The surface shape is monitored in situ and corrected to attain the desired aberration level. The irradiation fluence is approximately 40 mJ/cm(2), and the ablation depth/pulse is approximately 0.01 mum/pulse for UV-cured resin. A wave-front aberration of 3.0 lambda is reduced to 0.17 lambda for flat surface shaping. For spherical surface generation, an aberration of 2.5 lambda is reduced to 0.2 lambda. The increase in surface roughness is kept within acceptable levels.  相似文献   

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A thermoformed, microwavable container made from a polypropylene/Saran®/polypropylene coextruded material was selected as the test container. Samples of the specimen were microwaved in sealed glass vials for periods ranging from 3 to 7 min. After heating, the head space of the vials was sampled and analysed. The microwaving process was carried out in an Amana Radarange® microwave oven on full power. Sample surface temperature as a function of microwaving time and the quantitative identification of volatile compounds released by the polymer during microwaving were determined. Five major components were detected and quantified in the head space of the vial using gas chromatography. The quantity of each component increased with increased microwaving time. Using mass spectrometry, the five components were identified; four were hydrocarbons and the fifth was butylated hydroxytoluene (BHT). Release of organic components during brief microwaving of polymers may be a near-the-surface phenomenon.  相似文献   

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Plastics materials are increasingly used in the packaging of foods, and migrational behaviour has attracted considerable legislative attention. It was not clear whether vibration occurring in transport could influence the migration of plastics components from package to food, and this study examined this effect. Global migration from PVC was found to be affected, and a study of specific migration is now in progress.  相似文献   

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The recycling of a particular internal car component with a multilayer structure such as the dashboard has been extensively investigated. On this item, based on polyolefins, a thermal, spectroscopic, mechanical and morphological analysis has been performed. The recycled material showed a strong worsening in the mechanical and impact properties due to the occurrence of thermo-oxidative and thermo-mechanical degradation phenomena taking place during processing. A limited improvement in the mechanical behaviour has been obtained by adding, during the recycling, a suitable antioxidant and stabiliser additive. A more significant enhancement has been achieved in terms of deformation at break, impact toughness and overall morphology when an ethylene-propylene copolymer and virgin polypropylene were added to the formulation during the recycling process. By this procedure materials with properties suitable to be reused for the same or for similar applications within the car have been obtained.  相似文献   

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《中国工程学刊》2012,35(1):45-50
In this study, rice starch-filled linear low-density polyethylene (LLDPE) was prepared by twin screw extrusion. The rice starch was blended in a virgin grade LLDPE and two kinds of recycled LLDPE using citric acid as a compatibilizer. It was found that the maximum content of rice starch blended into LLDPEs could not be more than 3?wt%. The ratios of starch to citric acid were 1?:?1 for extruded samples. The starch increased the melt flow index (MFI) of LLDPE, but tended to decrease the MFI of recycled LLDPE. Tensile strength and elongation at break of the LLDPE (common recycle grade) when blended with starch at 1?wt% were less by 8.2% and 9% than those of neat recycled LLDPE, respectively. Tensile strength and elongation at break of the deinked-recycled LLDPE when blended with starch at 1?wt% were less by 9.5% and 26% than those of neat deinked-recycled LLDPE, respectively.  相似文献   

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《Zeolites》1988,8(1):88
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Solar power is the most abundant renewable resource on our planet. In spite of this abundance, only 0.04% of the basic power used by humans comes directly from solar sources because harvesting solar energy using a photovoltaic (PV) panel costs more than burning fossil fuels. Solution-processable organic materials have recently been intensively studied for PV applications, not because they show a possibility for harvesting the sun’s power more efficiently, but because power generation from organic photovoltaic (OPV) materials will cost considerably less than other PV technologies. The cost/Watt savings comes from the possibility of using flexible substrates, using printable organic inks for the active layers, light-weight transport, low temperature and ambient pressure fabrication, and reduced materials costs. The ability to use solution processes for deposition is particularly exciting because products such as automobiles, freight containers, and building materials could be painted with photovoltaic coatings. This article gives an overview of the current state-of-the-art for OPV technology and discusses scientific issues that need to be addressed to facilitate scale-up of OPV.  相似文献   

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Serrated plastic flow   总被引:1,自引:0,他引:1  
This paper attempts an assessment of the current understanding of the phenomenon of “serrated plastic flow”, which manifests itself as serrations, load drops, jerkiness or other discontinuities in the stress-strain curves obtained in constant extension rate tensile tests, and as sudden bursts of strain in constant loading rate tests and in constant load (stress) creep tests (the so called staircase creep). Though one can identify at least seven physical processes that can cause serrations, the discussion here is restricted mainly to serrated yielding in tension tests originating from dynamic strain ageing (dsa). The characteristics of the five types of serrations that have been identified so far and the experimental conditions under which they occur are discussed. The various models of serrated flow that have been put forward are reviewed critically. Some recent results on 316 stainless steel are presented to illustrate the effects of grain size, temperature and strain rate on serrated flow. Manifestations ofdsa other than serrations such as a negative strain rate sensitivity, positive temperature dependence for flow stress and work hardening, and the ductility minimum are also discussed. Finally the various issues to be resolved are enumerated.  相似文献   

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An idea of fine blanking is put forward where negative clearance affects plastic shearing and the plastic state of material in the shearing zone is examined under the condition of negative clearance. By analyzing of blanking force and stress, the paper brings forward a method of setting up the three-directions pressed stress. The method determines if the material of deformation field enters the plasticity regime. Some parameters that control when the material of blanked zone enters into the plastic state are given. The analysis indicates that the material stays in the plastic regime, when the specific energy of elastic deformation for common carbon steel Q235 reaches 8.34 MPa. The status of plastic flowing in the shearing zone is simulated.  相似文献   

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We propose a method aimed at the evaluation of the amplitude of singularity and dimensionless angular distributions of the second terms in the expansions of stresses, strains, and displacements in the plastic zone in the vicinity of the crack tip. The method is based on the combination the Hutchinson-Rice-Rosengren-type analytic solution and a numerical solution obtained by using a modified method of boundary layer. The presented results enable us to analyze the effects of constraints in broad ranges of conditions of biaxial loading. __________ Translated from Problemy Prochnosti, No. 3, pp. 43–59, May–June, 2006.  相似文献   

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降解塑料的开发进展   总被引:10,自引:0,他引:10  
本文介绍了降解塑料的研究开发和生产现状 ,探讨了其中存在问题 ,并且对市场前景进行了分析  相似文献   

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