双泵合流技术在小方量混凝土搅拌运输车上的应用

本文针对目前小方量混凝土搅拌运输车搅拌筒的转速控制和系统节能问题,拟定了一种双泵合流控制方案,并对这种传动系统进行了分析。结果表明,双泵合流技术在小方量搅拌车上的应用可以有效地控制搅拌筒的旋转速度和方向,降低了小方量搅拌车的能量损耗,取得了良好的经济效益。     

平板载荷试验在强夯地基土承载力检测中的应用

本文介绍了地基土在强夯作用之后运用平板载荷试验方法进行地基土承载力检测的试验,通过对内蒙古某新建工程实例的平板载荷试验进行分析,利用静载荷测试分析系统JYC软件对试验数据进行处理,重点讨论了平板荷载试验的试验原理、试验要点、承载力特征值的确定等内容,进一步分析说明了平板荷载试验的适用性。     

大学生心理健康教育切入点研究

提高大学生心理健康教育实效性的关键问题是找准切入点,即从大学生感到最敏感、最脆弱、最需要、最关心、最欠缺、最容易出偏差等对心理健康影响最大的内在因素入手,选择相应的教育目标、教育内容和教育方法,只有这样才能达到促进大学生的心理成长,维护大学生心理健康的终极目的。本文从大学生心理健康教育的实践出发,基于对影响大学生心理健康教育实效性的因素分析,提出了有利于提高大学生心理健康教育实效性的五个切入点：一是以培养自信为切入点,引导大学生构建健康的自我意识;二是以阳光心态塑造为切入点,引导大学生提升情绪管理能力;三是以人格完善为切入点,引导大学生强化人际交往能力;四是以职业生涯规划为切入点,引导大学生确立合理的成才目标;五是以生命教育为切入点,引导大学生追求积极健康的人生意义。     

YT15硬质合金刀片刃口电化学钝化实验研究

刀具是切削加工工艺系统的核心部分,刀具的耐用性和可靠性直接决定加工精度、表面质量和切削效率。为了改善硬质合金刀具切削性能,常需要对刀具进行刃口钝化。由于刀具为消耗品,其钝化技术需要具有加工一致性、高效率和良好的工艺适应性。本文采用电化学加工方法进行硬质合金刀片刃口钝化,实验结果发现,电化学钝化硬质合金刀片刃口可在短时间内获得接近30μm的钝圆半径,刃口均匀性良好,钝化后的刀片几何参数具有良好的一致性,对实际生产具有指导意义。     

Early prediction of water-holding capacity in meat by multivariate vibrational spectroscopy

This study had the dual purpose of (a) investigating the feasibility of measuring fundamental vibrational information in fresh porcine meat using infrared (IR) absorption and Raman scattering, and (b) investigating if the vibrational spectra obtained within 1 h after slaughter contained information about the water-holding capacity (WHC) of the meat. Preliminary studies performed at a research slaughterhouse revealed a high correlation between WHC and both IR (r=0.89) and Raman spectra using Partial Least Squares Regressions (PLSR). The good results were confirmed under industrial conditions using FT-IR at-line spectroscopy. However, the latter experiment yielded a somewhat lower correlation (r=0.79). This result is, however, promising for the purpose of finding a method for classification of carcasses with regard to WHC at the slaughter line. The IR region 1800-900 cm(-1) contains the best predictive information according to WHC of the porcine meat. This region covers functional group frequencies of water, protein, fat and glycogen, including the carbonyl and amide groups.     

A longitudinal study of Salmonella shedding and antimicrobial resistance patterns in North Dakota feedlot cattle

Salmonella is one of the most frequent causes of foodborne illness worldwide, and transmission involves foods of animal origin such as beef. The objective of this study was to monitor the prevalence of Salmonella fecal shedding in feedlot cattle during the finishing period and to assess the antimicrobial resistance patterns of the isolated salmonellae. On arrival at the feedlot, 1 (0.7%) of the 144 steers was shedding Salmonella in its feces. After 28 days on feed, shedding was detected in 8 (5.6%) of the 144 steers. At the third sampling, 19 (13%) of 143 steers were shedding, and the number of shedders continued to increase to 89 (62%) of 143 at the last sampling. Salmonella shedding was significantly influenced (P < 0.0001) by sampling time but not by herd of origin. All Salmonella isolates identified belonged to serotype Typhimurium serovar Copenhagen, a type commonly isolated from Salmonella infections in humans. Antimicrobial resistance testing of the isolates revealed five multidrug resistance patterns, two of which accounted for 104 (95.4%) of 109 of the isolates. All the isolates were susceptible to ceftiofur, and all were resistant to spectinomycin, sulfathiazole, tiamulin, florfenicol, ampicillin, penicillin, chlortetracycline, oxytetracycline, and clindamycin. Data from this study indicate that a high prevalence of antimicrobial-resistant Salmonella strains can sometimes be found in feedlot cattle in North Dakota. These data will contribute to risk assessment of Salmonella shedding by cattle in feedlots and highlight the need to continue preharvest monitoring for this organism.     

超级微波消解—电感耦合等离子体质谱法测定豆奶粉中镍的含量

目的：为市售豆奶粉中镍污染风险防控提供技术支撑。方法：以浓硝酸为消解液,利用超级微波消解进行前处理,以铑元素作为内标物消除基质干扰,在动能甄别模式(KED)下利用电感耦合等离子体质谱法测定豆奶粉中镍元素的含量,并对超级微波消解条件与ICP-MS工作条件进行了优化。结果：该方法的标准曲线在0~10 μg/L的质量浓度范围内线性关系良好,相关系数为0.999 9,检出限为0.002 mg/kg,加标回收率为94.5%~100.6%,相对标准偏差为1.8%~2.3%;用豆奶粉中镍质控样(ZKQC5210)对该方法进行准确性验证,结果在证书标定范围内。结论：该方法准确可靠,适用于豆奶粉中镍含量的测定。     

Effects of diet and injection of bovine somatotropin on prepubertal growth and first-lactation milk yields of Holstein cows

To determine effects of rapid prepubertal growth on first-lactation milk production, Holstein heifers were randomly assigned to one of three treatments. Thirty-five heifers were fed a standard diet to meet NRC recommendations and produce 0.8 kg of body weight (BW) gain/d (standard). Thirty-five heifers were fed a diet with higher energy (2.8 Mcal of metabolizable energy/kg) and protein (19.7% crude protein; high diet) to produce 1.2 kg of BW gain/d (high). Thirty-five heifers were fed the high diet and injected daily with bovine somatotropin (bST) (25 microg/kg of BW; high-bST). Diets were fed and bST was injected from 135 kg of BW until pregnancy was confirmed. Heifers were inseminated after BW exceeded 363 kg. Pregnant heifers were commingled and fed similar diets through gestation, parturition, and lactation. High and high-bST heifers had greater prebreeding average BW gains than standard heifers. Conversely, standard heifers had a greater average BW gain during gestation than high and high-bST heifers. High and high-bST heifers were approximately 90 d younger than standard heifers at first insemination and first parturition. Postpartum BW, body condition scores, and withers heights at parturition, and calving ease scores were not different among treatments. Standard heifers produced 14% more milk than high heifers but not more than high-bST heifers. The high-protein, high-energy diet decreased age at first parturition and first-lactation milk production, but did not affect reproduction. Injection of bST during the prepubertal growth period combined with the high diet decreased age at first parturition without reducing milk production.     

聚氨酯/SiO2涂料结构的表征

利用UV-2501PC型紫外分光光度仪、傅立叶变换红外光谱仪、OCAH200视频高速接触测量仪和SPA-400型原子力显微镜,研究了聚氨酯/SiO2材料性能.结果表明其红外吸收有明显变化;纳米SiO2涂膜的紫外屏蔽增强,耐老化性能提高.乳液的表面张力几乎无变化,接触角增大25°左右.纳米SiO2在涂膜中的分布比较均匀,其直径在50～150nm之间.