共查询到18条相似文献,搜索用时 203 毫秒
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声发射检测技术是无损检测中的一种新方法,它可以提供连续的状态信息,适合于设备在线监控及早期破坏预警。通过声发射传感器采集声信号,再利用计算机信号处理系统对采集的声信号进行分析、转换、处理,以此为原理构成检测系统。该检测技术是材料试验、水利水电工程设备在线监测和安全评估的有效手段。 相似文献
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三维编织复合材料压缩损伤声发射特性分析 总被引:4,自引:2,他引:2
论述了声发射技术在三维编织复合材料压缩过程中的应用及实验方法,给出了声发射在三维编织复合材料中压缩过程的特征。结果表明,声发射参数可描述复合材料在不同情况下内部变形的损伤机制。表面编织角是影响三维编织复合材料力学性能的主要参数,编织角小于30°,三维编织复合材料具有较好的压缩性能;编织角大于40°,三维编织复合材料压缩力学性能明显降低。为分析复合材料的力学性能,改善材料复合工艺提供理论基础。 相似文献
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EFFECT OF MANNITOL TREATMENT ON ULTRASOUND EMISSION DURING TEXTURE PROFILE ANALYSIS OF POTATO AND APPLE TISSUE 总被引:2,自引:0,他引:2
An ultrasound acoustic emission (AE) signal was recorded during texture profile analysis (TPA) of potato and apple tissue with different texture. The acoustic sensor was in contact with the sample through solid medium. Texture of the tissue was controlled by soaking it in different mannitol solutions. Both TPA and AE parameters change with the texture of potato and apple samples. However, correlation coefficients of linear regression of acoustic parameters are higher than TPA parameters and all of them are significant at a higher confidence level. Critical stress and strain indicate micro‐cracking of the material and they increase with decreasing tissue turgor. The ratio of the critical stress to hardness allows an analysis of sound duration. The sound lasts longer when the tissue is more turgid as a result of the decrease of critical stress to hardness ratio. Counts of AE recorded in the whole TPA test decreased logarithmically with tissue osmolality. The article showed that contact AE can be used for texture evaluation of potato and apple tissue. 相似文献
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The biogeochemical behavior of Pt and Pd in coastal sediments has been examined in a series of microcosms, both in the presence and absence of the deposit-feeding invertebrate, Arenicola marina. When metals were introduced to the overlying water column as solutes from acidified standards, A. marina dramatically enhanced their sorption to sediment throughout the core depth (14 cm) compared with an unfaunated control by exposing a greater surface area of particles to more rapidly ventilating contaminated water. After a 10 day incubation period, the assimilation efficiency (AE) by A. marina was about 10% for Pt and 1% for Pd. Calculations based on either partition constants or operational measures of metal bioaccessibility in sediment (using the protein, BSA) suggested that both aqueous and dietary sources of metal were important When Pt and Pd were introduced to the sediment-water interface as components of ground catalytic converter particles, significant subduction was effected by A. marina, and metals were solubilized to a greater extent than in an unfaunated control. AE in these experiments was < 0.1% for Pt and about 1% for Pd, and the most important vector for assimilation appeared to be from the aqueous phase via partial solubilization of metal from catalytic material. The findings of this study improve our understanding of the availability, cycling, and fate of Pt and Pd in contaminated estuaries and coastal waters. 相似文献
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Mouse recipient cytoplasts for somatic cell nuclear transfer (SCNT) are routinely prepared by mechanical enucleation (ME), an invasive procedure that requires expensive equipment and considerable micromanipulation skills. Alternatively, oocytes can be enucleated using chemically assisted (AE) or chemically induced (IE) enucleation methods that are technically simple. In this study, we compared the reprogramming potential and developmental capacity of cloned embryos generated by ME, AE, and IE procedures and treated with the histone deacetylase inhibitor valproic acid. A rapid and almost complete deacetylation of histone H3 lysine 14 in the somatic nucleus followed by an equally rapid and complete re-acetylation after activation was observed after the injection of a cumulus cell nucleus into ME and AE cytoplasts. In contrast, histone deacetylation occurred at a much lower level in IE cytoplasts. Despite these differences, the cloned embryos generated from the three types of cytoplasts developed into blastocysts of equivalent total and inner cell mass mean cell numbers, and the rates of blastocyst formation and embryonic stem cell derivation were similar among the three groups. The cloned embryos produced from ME and AE cytoplasts showed an equivalent rate of full-term development, but no offspring could be obtained from the IE group, suggesting a lower reprogramming capacity of IE cytoplasts. Our results demonstrate the usefulness of AE in mouse SCNT procedures, as an alternative to ME. AE can facilitate oocyte enucleation and avoid the need for expensive microscope optics, or for potentially damaging Hoechst staining and u.v. irradiation, normally required in ME procedures. 相似文献
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Ishtiaque Ahmad Anjum Khalique Muhammad Junaid Muhammad Qamar Shahid Muhammad Imran Abdul Ahid Rashid 《International Journal of Food Science & Technology》2020,55(6):2580-2588
The objective of this study was to evaluate the effect of apple peel polyphenol extract (APPE) on the microbiological and physicochemical properties of yoghurt ice cream stored at −20 °C for 90 days. Five level of APPE were added in yoghurt ice cream as: CTL (control without APPE); AE1 (1% APPE); AE2 (2% APPE); AE3 (3% APPE); AE4 (4% APPE); and AE5 (5% APPE). Samples with APPE had viable counts of Lactobacillus acidophilus and Bifidobacterium lactis of ≥8 log cfu g−1 and >7 log cfu g−1, respectively, during 90 days storage except the control sample. The highest viability of probiotics was obtained in the sample fortified with 5% APPE. The presence of APPE increased the acidity, decreased the melting rate and enhanced the overrun. Compared with the control sample, the hardness of the experimental samples increased with the fortification of APPE. The addition of APPE significantly increased sensory attributes. 相似文献
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An adaptive control optimization system was developed to produce a desired surface finish roughness by automatic control of the work-piece feed-rate in circular sawing. The system developed in this study consists of the interconnection of an adaptive controller with a numerically controlled circular saw. The AE signals and cutting forces were measured to monitor the machining process continuously in this system. The signals were provided to the adaptive controller to evaluate the surface finish roughness and adjust the workpiece feed-rate automatically in the machining process. Sensing of AE signals and of cutting forces was compared to determine which technique is more convenient. Experiments were carried out with a carbide-tipped circular saw. Cross cutting was done with counter-cutting during the experiments. The cutting parameters controlled were workpiece feed-rates and cutting speeds. Japanese beech (Fagus crenata Blume) and Yezo spruce (Picea jezoensis Carr.) were used as the workpiece. Experimental results indicated that adaptive control optimization took place in the system developed for circular sawing. The desired surface finish roughness was produced by automatic control of the workpiece feed-rate using the sensing technique of AE signals as well as that of cutting force. However, the system using AE signals is more convenient than taht using cutting force. 相似文献
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Nonlinear sorption of three alcohol ethoxylates to marine sediment: a combined Langmuir and linear sorption process? 总被引:1,自引:0,他引:1
Alcohol ethoxylates (AE) are nonionic surfactants mainly used in laundry cleaning products. The relation between particle bound and freely dissolved concentrations is an important entity in risk assessment. The mechanistic understanding of AE sorption is still poor, hampering extrapolations from laboratory studies to the field. We studied the sorption of three AE with 8 EO units but with increasing alkyl chains (C10, C12, and C14) to a marine sediment. Solid-phase microextraction, using polyacrylate as the extraction phase, was applied to measure freely dissolved concentrations in pore water. A model that combines a Langmuir and a linear sorption term fitted the nonlinear sorption data to sediment well. At low aqueous concentrations, adsorption dominates over absorption leading to higher distribution coefficients for AE at low field concentrations. This dual-mode model offers the possibility to extrapolate to other AE homologues and other marine sediments and also from high to low field concentrations. 相似文献
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论述了声发射技术在三维编织复合材料拉伸和弯曲过程中的应用以及试验方法,描述了三维编织复合材料拉伸与弯曲过程中声发射的特征。拉伸试验结果表明:编织角小的试件,其应力应变曲线基本为直线,损伤为脆性特征;编织角大的试件,应力应变曲线表现出双线性,各自呈现出脆性破坏特征。弯曲试验表明:小编织角复合材料的载荷挠度曲线保持线性关系;大编织角复合材料的载荷挠度曲线是非线性关系。 相似文献
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Wentao Xu Zhihong Liang Yang Rong Yunbo Luo Fangfang Zhang Yanfang Yuan Kunlun Huang 《Journal of the science of food and agriculture》2009,89(3):494-503
BACKGROUND: With the development of genetically modified organisms (GMOs), event‐specific qualitative and quantitative polymerase chain reaction (PCR) detection methods have become the internationally agreed standard. RESULTS: The flanking regions of DAS‐59122‐7 maize were characterized by inverse PCR (I‐PCR). In the qualitative PCR assay, a duplex PCR was established with the event‐specific and taxon‐specific primers, and the limit of detection (LOD) was 1 g kg?1 (approximates to 38 haploid genome copies). In the quantitative TaqMan® real‐time PCR assay, a plasmidic reference material was constructed by recombinant PCR and standard curves were set up. By using the plasmidic reference material, we obtained standard curves with good linearity and relatively high efficiency. The results indicated the usability of the plasmid as standard material. CONCLUSION: From above results, we believe that the developed event‐specific qualitative and quantitative PCR systems for DAS‐59122‐7 maize in this study are acceptable and suitable for DAS‐59122‐7 maize detection. Copyright © 2008 Society of Chemical Industry 相似文献