三角胶带的计算机辅助设计

本文利用电子计算机对三角胶带设计中的有关图、表进行了数据的曲线拟合,得出了七种型号三角胶带设计中包角系数k_α、传动比系数k_i、长度系数k_L、单根三角胶带传递的功率P_0的计算公式.其计算结果与经验数据吻合,适用于三角胶带的计算机辅助设计,具有一定的理论及实用价值.     

AutoCAD与Word软件在建筑类文档中的应用

用三种方法介绍如何在Word文档中插入AutoCAD图形.     

智能仪表设计中非线性输入信号处理方法

文中以热电偶测温为例，介绍了智能仪表设计中应用二次插值理论进行非线性输入信号线性化处理的方法。此法可以提高线性化处理精度，也可节省数据表格存储量。     

内插松弛扭带波节管的流动与传热特性的数值模拟

采用RNG k-ε数值模拟方法研究一种新型内插松弛扭带波节管（CLT）的流动与传热特性。将数值模拟结果与自建实验台的实验结果进行了对比验证;比较了CLT和内插松弛扭带光管（SLT）的传热性能差异;考察了CLT中扭率和余隙比对流动和传热特性的影响规律。研究结果表明CLT相比于传统的SLT,传热性能最多提高1.17倍,综合传热性能的绝对数值最多增加0.15。CLT的综合传热性能随着扭率的增加而增加,而增加的幅度却逐渐减小,高Reynolds数时减小的程度更加显著。同时,综合传热性能随着余隙比的增大而降低并且降低的幅度也逐渐减小,在低Reynolds数时明显降低,而在高Reynolds数时略微降低。综合考虑,低Reynolds数时应该选择余隙比低的扭带,而高Reynolds数时则应选择余隙比高的扭带。     

长兴县夹浦镇CATV网插入村级广播的技术方案

针对村镇目前的不同情况,采用不同的方案插入村级广播,使村民不但能听到上级的有线广播,而且能及时听到本村的信息,为新农村建设做好宣传舆论工作。     

电机机座压铸模设计

通过对电机机座薄壁压铸件成型工艺的分析 ,针对该类产品散热片薄而多、内孔包芯力较大 ,脱模难、生产率低、模具寿命短的难点 ,提出一种新型模具结构 ,详细介绍了该模具的浇注系统 ,内浇口截面积的计算及油冷温控系统的设计 ,对于薄壁型压铸模的设计有一定的参考价值。     

CVD金刚石涂层硬质合金刀片的基体预处理方法进展

全面概述了 CVD金刚石涂层硬质合金刀具的开发现状、存在的主要问题 ,重点对硬质合金刀具表面预处理方法的研究现状进行了综述     

某医疗器械带金属嵌件塑件的注塑模具设计

以某医疗器械带金属嵌件塑件为研究对象,运用注塑成型技术进行注塑模具设计。针对产品的多规格及系列化特点,创新设计了浇注系统,可以根据需求成型不同规格产品。通过分析塑件的结构特征,设计了组合式型芯、哈夫机构、推出机构,实现嵌件刀片的精准定位,完成塑件成型和自动脱模。将立式注塑机工作台,由一个工位改造成两个工位,既能方便地取出成型塑件,又能安全地将嵌件装入型芯。模具经生产验证,产品质量稳定,外观和形状尺寸精度能满足客户要求。     

Supplementation of progesterone via controlled internal drug release inserts during ovulation synchronization protocols in lactating dairy cows

Our objective was to determine the effect of exogenous progesterone (P4) during a timed artificial insemination (TAI) protocol on pregnancies per AI (P/AI) in dairy cows not previously detected in estrus. Lactating cows (n = 3,248) from 7 commercial dairy herds were submitted to a presynchronization protocol (2 injections of PGF_2α 14 d apart; Presynch), and cows in estrus after the second PGF_2α received AI (EDAI; n = 1,583). Cows not inseminated by 12 to 14 d after the second PGF_2α injection were submitted to a TAI protocol (GnRH on d 0, PGF_2α on d 7, and GnRH + TAI 72 h after PGF_2α). At onset of the TAI protocol, cows were balanced by parity and days in milk and assigned randomly to receive no exogenous P4 (control, n = 803) or a controlled internal drug release (CIDR) insert containing 1.38 g of P4 from d 0 to 7 (CIDR, n = 862). Blood samples were collected at the second PGF_2α injection of the Presynch and on the day of the first GnRH injection of the TAI protocol for P4 determination. When P4 in both samples was <1 ng/mL, cows were classified as anovular, whereas cows having at least 1 sample ≥1 ng/mL were classified as cyclic. Concentration of P4 at 11 to 14 d after AI was determined in a subgroup of cows (n = 453) from 2 herds. Pregnancy was diagnosed at 40 ± 5 and 65 ± 5 d after AI. Proportion of cows inseminated on estrus after the second PGF_2α injection of the Presynch protocol differed among herds (range = 26.7 to 59.8%). Overall P/AI for EDAI cows at 40 ± 5 and 65 ± 5 d were 36.2 and 33.7%, respectively, and pregnancy loss was 8.8%. Proportion of cyclic cows at the onset of the TAI protocol differed among herds (range from 66.5 to 86.3%), but did not differ between treatments (control = 72.4%, CIDR = 74.1%). Treatment affected P/AI at 40 ± 5 (control = 33.3%, CIDR = 38.1%) and 65 ± 5 (control = 30.0%, CIDR = 35.1%) d after AI but did not affect pregnancy loss (8.6%). Cyclic cows had greater P/AI at 40 ± 5 (38.2 vs. 29.3%) and 65 ± 5 d (35.1 vs. 26.1%) after AI, but cyclic status had no effect on pregnancy loss. Treatment affected P4 concentration after AI, with more CIDR cows having P4 ≥1 ng/mL (94.4 vs. 86.9%) and P4 ≥3.2 ng/mL (81.8 vs. 68.0%) at 11 to 14 d after AI compared with control cows. Treatment of cows not previously detected in estrus with a CIDR insert during a TAI protocol increased proportion of cows with functional CL after AI and P/AI.     

Heat transfer performance evaluation for turbulent flow through a tube with twisted wire brush inserts

In the present study, the heat transfer performance and friction factor characteristics in a circular tube fitted with twisted wire brush inserts were investigated experimentally. The twisted wire brush inserts were fabricated with four different twisted wire densities of 100, 150, 200, and 250 wires per centimeter by winding a 1 mm diameter of the copper wire over a 5 mm diameter of two twisted iron core-rods. Heat transfer and friction factor data in tubes were examined for Reynolds number ranging from 7,200 to 50,200. The results indicated that the presence of twisted wire brush inserts led to a large effect on the enhancement of heat transfer with corresponding increase in friction factor over the plain tube. The Nusselt number and friction factor of using the twisted wire brush inserts were found to be increased up to 2.15 and 2.0 times, respectively, than those over the plain tube values. Furthermore, the heat transfer performance was evaluated to assess the real benefits of using those type of inserts and the performance was achieved 1.85 times higher compared to the plain tube based on the constant blower power. Finally, correlations were developed based on the data generated from this work to predict the heat transfer, friction factor, and thermal performance factor for turbulent flow through a circular tube fitted with the twisted wire brush inserts in terms of wire density (y), Reynolds number (Re), and Prandtl number (Pr).