Performance modification of a melt-blown filter medium via an additional nano-web layer prepared by electrospinning

A poly(acrylonitrile) (PAN) nano-web was electrospun on a commercial melt-blown poly(propylene) (PP) filter medium to generate composite filter media. The performance of these media was characterized in terms of filtration efficiency and pressure drop. Quality factors calculated from these parameters were used to evaluate the overall efficacy of the filter media. Structural characterization of the composite media showed that a thin layer of nano-web could improve the overall performance by increasing filtration efficiency without significant increase of pressure drop.     

Lateral growth of a wheat dough disk under various growth conditions

Numerous studies have tried to understand and model bubble growth inside dough. Experimental studies are inconvenienced by the methods’ inability to capture the dynamic phenomena. In this paper, a versatile experimental method was developed to allow for macroscopic expansion of wheat dough. The study evaluates expansion of a dough disk under varying: moisture content (40, 41, 42, 43, and 44% wb), leavening acid concentration (30, 40, and 50% db), pressure schemas, pressurizing gas (compressed air and CO₂), and lubrication (Teflon^® film coating and Pam^® aerosol lubricant). Dough expansion increased 22.6% by increasing moisture content from 40 to 44%. Increased baking powder formulation (40% db) was used to enhance initial growth conditions and CO₂ production. ‘Pressure pulse’ and ‘pressure vacuum methods’ added pressurization alternatively with full vacuum. The former method included a rest period before vacuum application, and increased expansion by 10.8%. Teflon^® and Pam^® reduced friction between the dough and acrylic plate and increased the final expansion by 14.7% compared to no lubricant following the ‘standard pressurization method’. ‘Pressure pulse’ and ‘pressure vacuum’ experiments decreased expansion by 28.4 and 38.2%, respectively compared to ‘standard pressurization’ while using Teflon^® and Pam^®.     

反相高效液相色谱法检测香草兰豆酊、浸膏中香兰素

采用反相高效液相色谱法测定香草兰豆酊、浸膏中香兰素含量,色谱柱为C_(18)柱,甲醇/0.5%冰乙酸水溶液(20/80.v/v)为流动相,等浓度洗脱,测定波长为280 nm,外标法定量.该方法相对标准偏差分别为0.28%和0.24%.加标回收率为97.89%～100.71%.本方法具有操作简便,结果准确等优点,特别适用于香草兰豆酊、浸膏等精深加工产品中香兰素含量的检测分析.     

基于灰色关联法土壤水分垂直入渗影响因素研究

土壤水分入渗过程中主要受压力水头、土壤初始含水率、土壤容重、颗粒级配影响。基于一维垂直土柱积水入渗试验研究这些因素对入渗能力影响的主次关系,利用Green-Ampt与Philip入渗模型得到相应土壤入渗特性参数,采用灰色关联分析法研究四个因素对累积入渗量、饱和导水率、稳定入渗率、湿润锋面吸力、吸渗率的影响程度。结果表明,压力水头、土壤初始含水率、土壤容重、颗粒级配对累积入渗量、入渗率及Green-Ampt与Philip模型中物理参数有显著影响,各处理中饱和导水率与稳定入渗率间误差较小,吸渗率拟合值与利用湿润锋面吸力所得吸渗率计算值间相似程度较高,决定系数R2大于0.85;灰色关联分析结果表明,颗粒级配关联度均值r4最高为0.946 3,土壤容重、初始含水率其次,压力水头影响程度最小（r1=0.562 9）。总而言之,颗粒级配对土壤入渗特性影响起主导作用,该研究成果可为农业灌溉及水资源管理提供理论支撑。     

绿地喷灌系统常见问题分析

喷灌以其节水、节能、高效等优点,越来越被广泛的应用于园林绿化建设中。一套完美的喷灌系统不但能满足植物对水分的需求,而且在灌水同时还可以形成水动景观效果。喷灌系统应用过程中常见问题分别进行分析,并从中总结出一些实际经验。     

超高压处理对鲜切山药片质量的影响

为研究适宜的鲜切山药片的保藏方法,采用超高压处理对鲜切山药片进行保鲜。将鲜切山药片分别采用0MPa、200MPa、400MPa和600MPa加压处理10min后,在4℃条件下贮藏9d,分析超高压处理对贮藏期间鲜切山药片中细菌总数、多酚氧化酶活性、褐变指数、可溶性固形物、总酸和维生素C含量的影响。结果表明：600MPa压力处理10min后,可抑制于褐变相关的多酚氧化酶,抑制微生物生长,产品在4℃条件下贮藏9d后,仍然可具有较好的理化指标,表明该法是一种较好的鲜切山药片的保藏方法。     

A DISCUSSION ON SAFTY EVALUATION OF PRESSURE VESSELS

Based on the experience obtained in safty evaluation of pressure vessels, points for attention in the evaluation work are pointed out, problems concerning the present criterion of evaluation are discussed, and meanwhile safty evaluation is done for a pressnoe vessel in service, with satisfactory results.     

双蜗壳式离心泵内部非定常流动压力特性分析

为研究双蜗壳式离心泵内部流动特性,基于标准k-ε湍流模型和标准无滑移网格模型,应用CFX软件对其不同工况下的非定常流动进行三维数值模拟,得到了不同工况下双蜗壳式离心泵叶轮和蜗壳内部流道的压力脉动特性。计算结果表明,在小流量工况下,各监测点处的压力脉动都比较大且不均匀;在叶轮流道中,叶轮流道靠近出口边缘的压力脉动是叶轮流道其他区域压力脉动的5~8倍;在流量Q为34、110、148、160 m3/h 4个工况下叶轮分别旋转30步(90°)和90步(270°)时,压力脉动出现最大值。双蜗壳内圈流道的压力脉动强于外圈流道的压力脉动且隔舌处出现压力脉动较大值,大流量工况下双蜗壳隔舌和出口产生一定回流导致蜗壳该处附近监测点压力脉动先减小后增大。从傅里叶变换得到频域特性可知,叶频及其倍频是压力脉动的主要频率,且呈衰减趋势。     

发动机进气管中压力波动和气体运动的研究

在发火运转和不同转速，负荷下，测量了单缸柴油机进气管气流参数，并分析研究了这些参数的变化规律。此外，还得在进气马赫数Z不是转速的单值函数；在定转速而负荷不同时，它不是常数。     

高扬程填料密封结构水泵轴封水压力的调节

由于高扬程填料密封结构水泵一般是从水泵的压水室直接引取高压水对填料进行密封和润滑，使得填料密封腔内轴封水压力过高，泄漏量过大，压紧填料又增加轴(轴套)与填料的磨损，为此专门设计了调压阀，用于调节轴封水的压力。介绍了调压阀的结构、使用与调节原理，调节阀开启度与轴封水压力、流量关系的试验确定方法等。使用情况表明，使用该阀能实现对轴封水的压力、流量的自由调节，确保轴封水达到最佳的压力和流量。