肉用发酵菌株的筛选及其在低盐发酵香肠中的应用

该研究以蛋白酶、脂肪酶活性和抑菌活性筛选肉用发酵菌株,通过分子生物学技术对其进行鉴定,并将其应用于低盐发酵香肠中,通过感官、理化及微生物指标分析评价其应用效果。结果表明,筛选鉴定得到两株适用于肉类发酵、安全且具有蛋白酶及抑菌活性的菌株,分别为植物乳杆菌（Lactiplantibacillus plantarum）BR-12和木糖葡萄球菌（Staphylococcus xylose）H-1,其中菌株BR-12还具有脂肪酶活性,两菌株间无拮抗作用。菌株BR-12与H-1按2∶1和1∶5的比例接种制备的低盐发酵香肠pH下降迅速,肠杆菌数与挥发性盐基氮含量较低,感官评分较高,硬度适中,弹性好,呈特有的玫瑰红色,且两菌株接种比例为2:1时,品质更好,说明菌株BR-12和H-1复配发酵有利于提高产品安全性,改善低盐发酵香肠滋气味,可用于低盐香肠发酵。     

微机相控整流式充电机的改进分析

对相控整流式充电机进行研究,从其充电方式、晶闸管移相控制原理及比例积分微分(PID)软件调节设计等方面作了详细分析。对WCD-Ⅳ型微机相控整流式充电机提出了进一步的改进措施:将单脉冲或双脉冲触发信号改进为一组宽度为120°、脉冲间隔为0.12°的脉冲列,并进行高频调制和功率放大,确保晶闸管的可靠导通;采用改进的不完全微分型PID控制算法,并引入积分分离法,通过分离法算式,实现理想调节特性,从而避免积分饱和、减小超调、加快过渡过程,得到了良好的空载稳压特性;增加了逆变放电、高精度全自动充电、温度补偿及相序自适应等功能。     

改进的主成分分析法在白洋淀水质评价中的应用

针对数据标准化信息丢失以及主成分中各系数相近造成的涵义不明确,对主成分分析法进行了改进,很好地实现了降维的效果.将其应用于河北省白洋淀水质综合分析,结果表明:在各观测断面中普遍存在富营养化现象,氨氮、总磷是水质的主要污染指标.通过对各断面的水质进行综合评比,得出各站点的污染程度排序,为白洋淀区域治理提供理论指导.     

漕河满城段综合整治规划探讨

通过大清河系漕河满城段河道综合整治工程的经验,从防洪整治的必要性,规划指导原则,河道整治方案及综合整治规划设计等方面对河道整治规划设计的一些问题进行了探讨．以期为毗邻城市河流的河道综合整治规划工作提供借鉴。     

新型固态高频焊管电源的开发

钢管的直缝焊接大多使用电子管电源,但其能耗大、电压高、电子管使用寿命短,随着电力电子技术的发展,国内外相继开发出固态高频电源。保定红星高频设备有限公司研制开发出焊接钢管用新型固态高频电源,简介了该固态高频电源的性能和特点,分析了电力电子器件在高频下的开关损耗。通过波形对比指出了电子管电源和固态焊管电源输出纹波的区别。     

某4缸乘用车柴油机冷却水套的设计优化

介绍了长城汽车研发的一款高性能"2.0VGT"柴油发动机冷却水套的设计优化过程,该发动机在进行可靠性试验过程中发现缸盖第1缸鼻梁区存在裂纹,导致冷却水渗入燃烧室发生失火。经过CFD模拟分析,采用优化垫片水孔结构,调整水孔上水量,得到优化后方案整体压力场,局部速度、对流传热系数、温度场的分布等均比优化前有明显改善。特别是优化后方案提高了缸盖第1缸鼻梁区(排气道与喷油器之间水路)冷却水的流速,避免了鼻梁区由于热负荷较大而导致的结构断裂问题。     

赣杭构造带某铀矿区地下水中铀的存在形式研究北大核心CSCD

为研究铀矿区地下水化学性质对铀的存在形式的影响,本文以赣杭构造带某铀矿区地下水为研究对象,在对9个典型采样点地下水化学成分分析的基础上,采用数理统计软件SPSS 18.0和地球化学模拟软件PHREEQC及llnl.dat数据库,探究了研究区内地下水水化学特征及U的存在形式。结果表明:本研究区地下水水化学类型以HCO_(3)-Na与HCO_(3)-Na·Ca为主,U含量与Ca^(2+)和Mg^(2+)浓度体现出较强正相关性,与SO_(4)^(2-)的相关性次之;地下水中U元素主要以六价为主,几乎占100%,主要存在形式依次为UO_(2)(CO_(3))_(2)^(2-)、UO_(2)(CO_(3))_(3)^(4-)、UO_(2)CO_(3)、UO_(2)(OH)2、UO_(2)(OH)_(3)^(-)、UO_(2)OH^(+)等6种,其中UO_(2)(CO_(3))_(2)^(2-)占绝对优势,整体以碳酸铀酰形式为主,这也与研究区地下水酸碱性相对应。     

Hydrogen production through hydrolysis of sodium borohydride: Highly dispersed CoB particles immobilized in carbon nanofibers as a novel catalyst

Agglomeration of CoB catalysts is a severe problem in hydrogen generation from NaBH₄ hydrolysis. Herein, highly dispersed carbon nanofiber immobilized CoB catalysts (CoB/CN) were synthesized by a combined prereduction and carbonization method, which is used in hydrogen generation from NaBH₄ hydrolysis. Morphological evolution of carbon nanofibers, phase structure and elemental distribution of CoB/CN catalysts are explored by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Compared to Co/carbon nanofiber catalysts (Co/CN) without prereduction, CoB/CN catalysts can afford higher CoB dispersity and specific surface area because the migration rate of cobalt species during carbonization is effectively retarded by prereduction. Hence the agglomeration of magnetic CoB nanoparticles can be effectively inhibited. The hydrogen generation experiment shows that CoB/CN catalysts process higher catalytic activity and lower activation energy than Co/CN.     

PdCoNi nanoparticles supported on nitrogen-doped porous carbon nanosheets for room temperature dehydrogenation of formic acid

The development of cost-effective heterogeneous catalysts for the dehydrogenation of formic acid (FA) is the key challenge for the commercialization of FA as a hydrogen-storage medium. Herein, PdCoNi nanoparticles (NPs) with different element ratios supported on N-doped carbon nanosheets (N-CN) were designed, which exhibit excellent catalytic dehydrogenation performance for FA. Compared with PdCoNi NPs loaded on the carbon nanosheets (CN), the introduction of pyrrolic N to CN induces the formation of ultrafine, monodispersed and amorphous Pd_0.6Co_0.2Ni_0.2 NPs with a size of 1.60 nm, which significantly increases the number of active sites and the instant contact between FA and catalysts. The as-prepared Pd_0.6Co_0.2Ni_0.2/N-CN catalyst shows more than 99% conversion and 100% H₂ selectivity at room temperature, with a record-high initial turnover frequency (TOF_initial) of 1249.0 h⁻¹ among non-noble containing Pd-based catalysts, which demonstrates the high potential of Pd_0.6Co_0.2Ni_0.2/N-CN as a practical catalyst for the hydrogen generation from FA.     

The effect of solvent and ionomer on agglomeration in fuel cell catalyst inks: Simulation by the Discrete Element Method

We simulate agglomeration in different fuel cell catalyst ink solutions using Discrete Element Method. Carbon support is modelled as particles in various inks with ionomer and various solvents. The particles interact with particle-pair forces resulting in agglomerate build-up. The classical colloidal theory with van der Waals and electric double layer forces underestimates the ink stability, which motivates the development of a new model of polymer force between particles. The force is activated when there is a bridging of polymer between the carbon black particles, and the strength is dependent on the ionomer interaction with the solvent by the dielectric constant. A critical dielectric constant was defined for which ionomer form a web-like polymer network that increases the ink stability. This modification can explain the trend of the ink stability, and the model can simulate the effect of different solvents on the agglomerate size distribution with good agreement with experimental results.