射流式拔桩器动态特性分析

射流式拔桩器工作时受射流和地层冲击荷载的作用及起吊机械上下往复的作用,工作时容易出现水管扭转和拔桩器振动现象,水管扭转严重时影响射流造孔工作.采用有限元软件ANSYS分别对单独拔桩用拔桩器和沉拔桩用拔桩器进行建模,并进行了前5阶动态特性分析,结果表明:两种结构拔桩器的固有频率都远离激励频率,不会产生共振,水管扭转变形主要由拔桩器箱体结构、喷嘴射流不平衡和地层地质不均匀引起的.     

Effects of differential supplementation of fatty acids during the peripartum and breeding periods of Holstein cows: I. Uterine and metabolic responses, reproduction, and lactation

The objectives were to evaluate the effects of differential timing of supplementation of different Ca salts (CS) of fatty acids (FA) on FA profiles of cotyledonary-caruncular tissues, metabolic status, uterine health, pregnancy, pregnancy losses after 2 artificial inseminations (AI), and milk yield. Holstein cows (n = 1,380) were assigned randomly to be fed either CS of palm oil (PO) or safflower oil (SO) from 30 d prepartum until 30 d postpartum (dpp) and further randomized to receive either CS of PO or fish oil (FO) from 30 to 160 dpp. Supplementation of CS of FA was at 1.5% of dietary dry matter. Tissues (n = 23) and blood (n = 32) were collected from a subsample of cows. Blood was collected daily from parturition to 10 dpp and three times weekly thereafter until 30 dpp for analyses of PGF_2α metabolite, nonesterified FA, β-hydroxybutyric acid, blood urea nitrogen, and glucose. Cows were evaluated once between 8 to 10 dpp for cervical discharge type. At 43 dpp, cows received 2 injections of PGF_2α 14 d apart, followed 14 d later by injections of GnRH at 7 d before and 56 h after an injection of PGF_2α with AI at 16 h after the second GnRH injection. All cows received intravaginally a controlled internal drug-releasing device, containing 1.38 g of progesterone, at 18 d after the first AI followed 7 d later by removal of the device and injection of GnRH. Nonpregnant cows at 32 d after AI were injected with PGF_2α, followed 56 h later with a GnRH injection and second AI 16 h thereafter. Cows diagnosed pregnant after both AI were re-examined at 60 d of pregnancy to determine pregnancy losses. Milk weights were recorded monthly for all cows. Caruncular n-6:n-3 FA ratio was greater in cows fed SO. Plasma concentrations of metabolites and frequency of cervical discharge type did not differ between PO- and SO-fed cows. Plasma PGF_2α metabolite was greater in SO-fed cows at 4 and 7 dpp. Pregnancy per AI at 32 and 60 d post first AI was not affected by diets, but pregnancy loss was less in FO-fed cows. At second AI, pregnancy was greater in FO-fed cows at 32 d and in SO-FO-fed cows at 60 d post AI. Pregnancy loss after second AI was not affected by diets. Overall pregnancy per AI was greater in cows fed SO followed by FO at 60 d of pregnancy and pregnancy loss was reduced in FO-fed cows. Monthly milk yield was greater (0.7 kg/d) in SO-fed cows. In conclusion, strategic feeding of CS of FA during transition and breeding periods can benefit fertility and milk production of lactating dairy cows.     

纺织品中2,4-滴和2,4,5-涕残留量的测定

纺织品试样用酸性丙酮水溶液提取，提取液经二氯甲烷液-液分配提取后，再用甲醇-三氟化硼乙醚溶液甲酯化，经正己烷提取，用配有质量选择检测器的气相色谱仪（GC／MSD）测定，外标法定量，采用选择离子检测进行阳性确证。该方法回收率为88，8％～97．3％，相对标准偏差为2．41％～8．91％。     

使用增白剂后纸张色差与PH值的关系

目前双面胶版纸、有光纸、书写纸的用户都倾向于高白度,而生产这些纸张的原料大部分是用草浆和参配一定比例的木浆或破布浆。例如生产书写纸的原料为麦草浆,漂白方式为一段漂,白度最高76度(兰光法测定,以下均同);木浆系进口漂白硫酸盐或亚硫酸盐木浆,白度在87～88度;填料为滑石粉,白度在90度以上。在上述条件下,要生产较高白度的纸张就必须借助于增白剂。例如生产特号书写纸,木浆和麦草浆的配比     

当前我国果树生产发展上的现代化问题

我国地大物博,果树资源十分丰富,长期以来,由于封建反动统治,产量日益低落,果树生产濒于垂危。建国后,毛主席、周总理非常重视果树生产发展,制订了发展规划,周总理提出用柑橘绿化长江三峡,王震副总理要求发展果、药、桑、羊。但林彪、“四人帮”的干扰破坏,无政府主义横行,生产科研遭受严重摧残,果树生产陷于     

A biofilm model for flowing systems in the food industry

When bacteria attach to the walls of pipelines, they can form biofilms, which can cause the recontamination of food products. In order to quantify such recontamination, a one-dimensional biofilm model was developed taking into account adsorption, desorption, and the growth of cells. The model consisted of two mass balances describing increases in biofilm formation at the wall and the accumulation of cells in the liquid phase. The necessary parameters for the model were obtained in laboratory biofilm experiments. These experiments involved a flowing system and the use of Staphylococcus aureus as a model pathogen and silicon tubing as a testing material. S. aureus was inoculated into the system for 2 h, and then the system was changed to a sterile medium. Both biofilm formation and the release of cells into the flowing liquid were measured until steady-state conditions were reached (for up to 9 days). The experiments were performed in duplicate for different flow conditions (i.e., for Reynolds numbers of 3.2, 32, and 170). It was shown that at higher Reynolds numbers, the biofilm developed faster, probably owing to an increase in the transfer of nutrients to the surface. The proposed biofilm model was capable of describing the data obtained for the three different flow conditions with the use of the specific growth rate in the biofilm and the desorption coefficient as fit parameters. The specific growth rates were 0.16, 0.27, and 0.49 h(-1) for Reynolds numbers of 3.2, 32, and 170, respectively, and the desorption coefficients were about 1% of these values.     

干燥器法测定甲醛浓度——GB／T 17657与日本标准的比较

本文叙述了GB／T 17657《人造板及饰面人造板理化性能试验方法》中干燥器法制定的背景，分析了乙酰丙酮定量法测试条件的影响。试验结果表明：采用GB／T 17657中干燥器法与日本JAS中干燥器法测定甲醛浓度，其结果是相同的。     

磨粉方式对大米粉团性质的影响及硬化防止实验研究(二)

１．３．７磨粉方式对粒度分布的影响按１．３．１描述的方法制备大米粉，作为实验原料，按１．３．４中描述的方法测定粒度，研究磨粉方式对粒度分布的影响。１．３．８磨粉方式对水分含量、溶出率及硬度的影响按１．３．２的方法制备粉团，１．３．３的方法测定水分，按１．３．５的方法测定溶出率，按１．３．６的方法测定硬度。１．３．９粉团不同部位水分含量及溶出率的变化称取洗后干磨的籼米粉和粳米粉各２００g，按１．３．２的方法分别制成粉团，再各分成２０g、４０g、６０g、８０g共４份，依此顺序从内向外包成四层的粉团，各层…     

Estimation of intracellular phosphate content in plant cell cultures using an extended Kalman filter

Phosphate is an essential nutrient that is usually taken up by plant cells rapidly and stored intracellularly. Currently, there is no convenient means for on-line sensing of the intracellular phosphate content in cultured plant cells. In this study, a state estimator for this important parameter in batch plant cell cultures was developed using extended Kalman filter (EKF) methodology. A non-linear kinetic model was constructed to describe the dynamics of intracellular phosphate uptake and utilization. For intracellular phosphate estimation, this model was found to be most sensitive to three parameters: the maximum specific growth rate (mu(max)), the maximum phosphate uptake rate (nu(max)), and the yield coefficient on oxygen (y(o)). The EKF algorithm coupled with the kinetic model and on-line oxygen uptake rate (r(o)) measurement was used successfully to track the intracellular phosphate content under different initial phosphate concentrations. The state estimator could also accurately predict the biomass concentration. When mu(max), nu(max), and y(o) were included in the state vector, tracking of intracellular phosphate was only slightly affected. The estimation system was found very stable as long as the measurement errors of the initial states, the r(o) measurement error, and the system error were respectively within 30%, 30%, and 50%. With a r(o) measurement interval as long as 12 h, accurate tracking of the intracellular phosphate content could still be attained using a discrete EKF. Apparently, the slow r(o) dynamics in plant cell cultures allows the use of a long measurement interval. Considering the difficulties encountered in the on-line sensing of intracellular phosphate using the chemical or nuclear magnetic resonance (NMR) methods, the EKF method coupled with simple on-line oxygen uptake rate measurement provides a promising means for sensing this important culture parameter on-line.     

大豆11S和7S球蛋白对Alcalase凝固大豆蛋白性质的影响

通过对不同比例的11S与7S大豆蛋白在被碱性蛋白酶(Alcalalse)凝固过程中分子量和TPA参数的测定,表明在Alcalase凝固大豆蛋白过程中,11S球蛋白是形成凝胶的主要物质。