热流体喷射变形机理与喷嘴结构

高速短程纺技术能生产三维卷曲短纤维,该技术的关键之一是热流体喷射装置。本文介绍了热流体喷射装置的演变与特点及它的加工机理和某些已应用的实际装置。     

Improvement of Air-Distributing System of the Pneumatic Impact Machines for Trenchless Technologies

The process of actuation is considered for the inertial element in the improved air-distributing system of pneumatic puncher whose dimensionless parameters are determined.     

Solids Extraction of Cod Frame and Effects on Ultrafiltration of the Aqueous Extract

Grinding, pH adjustment, heat treatment and centrifugation were studied to recover solids from ground cod frames and to apply ultrafiltration (UF) to the resulting aqueous phase. Early heat treatment (90°C/20 min) dissolved collagen into aqueous phase resulting in a very low UF flux. A pH adjustment to 4.5 after grinding (～0.32 cm die), with no heat resulted in efficient separation after centrifuging. UF of the aqueous phase showed an increase in initial flux (23 L/hr m²). However, when the same aqueous material was heated and then centrifuged (1–2% solids removed), UF flux was further increased to 46 L/hr m²and this process gave highest solids recovery (90%).     

Effects of storage time and chemical preservatives on the total volatile basic nitrogen content in chilean mackerel (Trachurus murphy) prior to fish meal production

Total volatile basic nitrogen (TVB-N) as a measure of protein degradation and total microbial counts or stored raw mackerel (Trachurus murphy), which had been treated with chemical preservatives, were compared with the TVB-N and microbial counts of untreated fish. In unpreserved fish, decomposition of fish protein was rapid. Treatment of mackerel with acetic (1000-5000 μg kg^?1), which was the most effective of the parameters studied, approximately halved the rate of increase in TVB-N compared with the untreated samples. Changes in the total microbial counts presented a similar trend.     

加入WTO对我国水利科技工作的影响及对策

加入WTO后，对我国水利科技发展的影响主要表现在：研究开发活动、技术标准和知识产权保护方面，为适应WTO的各项规则，履行我国政府所作出的承诺，必须调整水利科技政策和发展战略，促进我国水利科技事业的健康发展。     

A Method of Combined SHPB Technique and BP Neural Network to Study Impact Response of Materials

Abstract:  A new method combining the split Hopkinson pressure bar (SHPB) technique with the back-propagation (BP) neural network program is proposed. By this method, the treated strain wave signals become smooth with less noises induced by the transverse inertia. Moreover, the dynamic rate-dependent constitutive behaviour of materials can be identified, without any pre-assumption of a constitutive model. It is found that by taking the experimentally measured data of strain, strain rate and time as 'input' and the corresponding data of stress as 'output' of the BP neural network, the dynamic constitutive behaviour with internal damage or phase transformation evolution is easy to be identified, where the time could represent either the internal damage evolution or phase transformation process accompanied with the deformation process. It is emphasised that the data learnt by the BP neural network must include both loading and unloading processes, if the whole loading and unloading response is to be correctly predicted. The comparisons between the predictions and experimental results are in good agreement for both polyamide (PA) polymer (as an example of nonlinear viscoelastic materials) and Ti–Ni alloy (as an example of superelastic materials with stress-induced phase transformation).     

硬粒子对聚合物材料表面的冲击摩擦研究

冲击摩擦为接触面切向与法向冲量之比。用聚合物材料试件与弹簧钢片组成振动测试系统 ,硬粒子以一定入射角冲击试件水平面引起系统振动 ,接触冲量通过振幅反映出来 ,记录初始振幅值而计算出一个冲击过程的冲击摩擦因数。结果表明 ,当入射角α在 2 5°-60°变化时 ,冲击摩擦因数f从 0 .5降至 0 .2左右。文章同时分析讨论了摩擦对聚合物表面接触强度的影响。     

电视节目制作中的压缩格式

电视节目制作系统中存在着几种格式的压缩问题 ,对几种压缩方式及其优缺点进行了分析。     

European intercomparison on electron spin resonance identification of irradiated foodstuffs

The results of a co-trial organized by the Community Bureau of Reference on the use of Electron Spin Resonance spectroscopy for the identification of irradiated food in 21 laboratories are presented. The trial was qualitative on beef and trout bones, sardine scales, pistachio nut shells, dried grapes, and papaya, and quantitative on poultry bones. There was no difficulty in identifying irradiated meat bones, dried grapes, and papaya. In the case of fish bones there is a need for further kinetic study on different species. Identification of irradiation in pistachio nuts is more complicated and additional research is needed before further trials. All laboratories were able to distinguish between chicken bones irradiated at 1 to 3 kGy or 7 to 10 kGy although there was a partial overlap between the results.     

Comparison of six methylation methods for analysis of the fatty acid composition of albacore lipid

Six methods widely used to produce methyl esters for the gas chromatographic determination of the fatty acid composition of a marine lipid were compared. Four acid-catalyzed methods (1% H₂SO₄: CH₃OH; 5% HCl: CH₃OH; 7% and 14% BF₃: CH₃OH) and two base-catalyzed methods [0.5M NaOCH₃: CH₃OH; (1:4) tetramethylguanidine: CH₃OH] were used.
The use of BF₃: CH₃OH (7% and 14%) gave a lower content of 18:1 n9 than the other methods and produced an artefact (2.7–3.2% of total fatty acid content) eluting between the 20:5 and 24:1 fatty acid methyl esters. No significant differences were obtained between the other four methods.
Accordingly the use of BF₃: CH₃OH for transmethylation of marine lipids is not recommended. Results obtained in the other four methods showed that all are comparable.