AZ31镁合金交流脉冲TIG焊接组织与性能研究

采用交流脉冲TIG焊对AZ31镁合金进行焊接,利用光学显微镜及扫描电镜对其焊缝组织进行观察,通过拉伸试验对焊接接头抗拉强度进行测试。结果表明:焊接电流为60A得到的焊接接头成形良好,未出现裂纹,焊缝组织均匀;焊缝主要组织为α-Mg固溶体和β-Mg_(17)Al_(12)沉淀相混合物,沉淀相呈亮白色在晶界处点状析出,分散较为均匀;焊接接头的平均抗拉强为180MPa,达到了母材强度的80%,力学性能良好,可以满足工程构件应用需要。     

浅谈HXN5机车板材矫正工艺及操作技巧

本文通过对HXn5机车板材矫正过程中一些变形原因的分析,总结出板材矫正过程中的操作经验及技巧,从而给出了一些提高产品质量及生产效率的方法。     

无孔型轧制工艺的开发和应用

本文对无孔型轧制技术的开发和应用进行了介绍。无孔型轧制具有节能、降耗、提高生产率的显著效果。     

试论冲压成型工艺在金属板材中的应用

板材成型性能的好坏会直接影响到冲压工艺过程、生产率、产品质量和生产成本.板料的冲压成型性能好,对冲压成型方法的适应性就强,就可以采用简便工艺,高生产率设备,生产出优质低成本的冲压零件.本文简要介绍了金属板材的冲压成型理论和特性,重点介绍了冲压技术的发展水平,同时说明了金属板材的冲压成型性能和未来金属板材成型行业发展的关键.     

合金元素对镁合金性能影响

镁合金具有优异的性能,随着关键应用技术的不断发展,其应用潜力巨大。本文简要说明了镁合金的分类,介绍了一些常用合金化元素,如Al、Zn、Mn、Si、Ca、Zr和RE等元素对镁合金性能的影响及机理。这些合金元素单独或共同影响着镁合金组织和性能。     

热处理对镁合金焊接接头性能的影响研究

综述了热处理对镁合金焊接接头性能的影响研究现状,热处理可以使AZ31B镁合金板的焊接接头的力学性能提高,随着退火温度的升高,AZ31B镁合金搅拌摩擦焊接接头前进侧和后退侧的分界线逐渐消失,热影响区的显微硬度略有下降。热处理可提高AZ31B镁合金板的的抗拉强度和延伸率。     

加工工艺对饲料营养价值及动物生产性能的影响

饲料是畜禽生产上开支最大的一项,在我国饲料支出约占总成本的６５％～７０％,通过恰当的加工方法可以获得较好的经济效益。饲料加工的目的正是为了充分发挥饲料营养价值的潜力,提高产品质量和饲养效果。饲料加工对动物营养的影响一直是饲料加工工艺学家和动物营养学家关心的问题,将加工工艺学和动物营养学有机结合起来能够更大提高动物生产性能。１粉碎粉碎的主要目的是增加饲料接触消化酶的表面积,以使之更易于消化,这也是饲料搅拌、制粒和接受其它处理所必需的。目前许多研究结果表明：粉碎对饲料营养价值和畜禽的生产性能有明显的…     

化工机械制造准备工艺中的辊式板材矫平技术分析

在众多品种的化工制造材料中,最重要的就是钢板。钢板的变形不仅会影响工序的尺寸精度,对其设备工作的稳定性也会造成一定的影响。而九辊板材矫直机,主要用于化工机械制造准备工艺中。本文将以九辊板材矫直机的技术应用为例,通过介绍其结构特点和工作原理,对其在板材矫平方面的应用进行技术分析,以期有一定的借鉴意义。     

热处理和变形对镁合金低频阻尼性能的影响及机理研究

基于镁合金所具备的物理属性在热处理以及形变作用下的机理变化作为探究对象,着重对纯镁、Mg-Al系、Mg-Ni系以及Mg-Si系等主要类别进行光学放大观测以及透射显微解析,通过实体面积、环境温度以及振幅频率等三个方面的集中试验,系统全面地探究在热处理以及变形作用下镁合金低频阻尼性能的变化规律、性能演变,从而为镁合金的进一步探究开发创造切实科学的理论基础。     

冷却工艺对70kg级高强钢组织性能影响分析

在相同的成分配比及轧制工艺条件下,对70kg级试验钢进行不同冷却工艺的生产试验,通过轧后钢板金相组织及性能数据结果,研究终冷温度及冷却速率对钢材组织及性能的影响,通过调整控冷工艺实现试验钢板强度及塑性的最佳匹配,确立了批量生产70kg级高强钢的控轧控冷工艺参数。     

锆合金力学性能分析

本文主要通过分析Zr-4合金材料的室温拉伸性能和高温拉伸试验特点,提出利用金属材料拉伸试验方法测量Zr-4合金室温、高温拉伸性能。并通过比较分析锆合金管材在不同温度和应力下的高温拉伸性能试验数据及室温拉伸性能数据,结果表明试验所用Zr-4合金拉伸性能数据集中,误差较小。     

Site and extent of apparent magnesium absorption by lambs fed different sources of magnesium

Ten abomasally cannulated crossbred wether lambs (avg wt, 33 kg) were used in a replicated 5 x 5 latin square design to determine the site and extent of apparent absorption of Mg when fed different sources of Mg. Lambs were fed twice daily 220 g of chopped mixed grass hay and 180 g of a corn-based supplement (control; .13% mg, DM basis), or the control diet supplemented with Mg (.26% Mg, DM basis) from MgO, magnesium citrate (MgC), smectite-vermiculite (Mg-Mica) or MgOH. Lambs were maintained in metabolism stalls during each of the five experimental periods. Each period consisted of a 7-d dietary adjustment followed by a 3-d collection of abomasal samples, feces and urine. Abomasal contents were sampled four times daily during the 3-d collection period. The diet contained .5% chromium oxide as a digestion marker. Apparent absorption of Mg was .17, .55, .85, .78 and .82 g/d for lambs fed the control, MgO, MgC, Mg-Mica and MgOH diets, respectively. Apparent absorption of Mg (g/d) was similar (P greater than .05) in the lambs fed the supplemented diets and greater (P less than .05) than in those fed the control diet. Preintestinal absorption of Mg was .21, .57, 1.08, .14 and .92 g/d when the control, MgO, MgC, Mg-Mica and MgOH diets were fed. Lambs fed the control and Mg-Mica diets absorbed similar (P greater than .05) quantities of Mg in the preintestinal region and less (P less than .05) than lambs fed the MgO, MgC and MgOH diets.(ABSTRACT TRUNCATED AT 250 WORDS)     

镁的生物学功能

镁是生物机体中含量较多的一种阳离子,其含量仅次于钙、钠、钾而居第4位;镁离子在生物细胞内的含量则仅次于钾离子而居第2位。整粒的种子、未经碾磨的谷物、青叶蔬菜、豆类和坚果是日粮镁最为丰富的来源。 镁是许多酶反应的辅助因子,参与蛋白质和核酸的合成、细胞周期的调控、维持细胞和线粒体结构的完整及物质与浆膜的结合,具有稳定和保护生物膜的作用。     

膨化过程中水分含量对菜籽粕蛋白性能的影响

试验考察了挤压膨化过程中菜籽粕水分含量对其粗蛋白和17种氨基酸含量、体外蛋白质消化率及蛋白二级结构的影响。利用双螺杆挤压膨化机对调质水分含量为14.52%、16.10%、17.62%、19.10%、21.21%的菜籽粕原料进行膨化处理,测定了膨化处理前后菜籽粕的常规指标(水分含量、粗灰分、粗纤维、粗蛋白及17种氨基酸含量),体外蛋白消化率,并利用红外光谱测定了蛋白的二级结构,利用扫描电镜测定了微观结构。结果表明,经膨化处理后,菜籽粕蛋白体外消化率显著提高,且随着膨化过程中水分含量的增加,蛋白体外消化率先升高后降低;在菜籽粕蛋白的二级结构中,经膨化处理后菜籽粕蛋白中β折叠的含量减少,无规卷曲含量增加;据SEM结果,膨化处理后菜籽粕表面变为疏松多孔,该变化增强了养殖动物体内消化酶的作用。本研究探讨了菜籽蛋白在膨化处理过程中的变化,为通过膨化处理提高菜籽蛋白的营养价值提供了数据和理论支持。     

牛蛙皮肤显微结构与组织化学研究

运用HE染色和3种组织化学方法—改良甲苯胺蓝、阿利新蓝-PAS和多巴氧化酶法染色对牛蛙皮肤显微结构和特性进行了研究。结果表明,牛蛙皮肤由表皮和真皮组成,表皮由角质层、颗粒层和生发层组成,表皮内无黑色素分布,微血管较少。真皮比表皮厚,分为疏松层和致密层。真皮疏松层内有大量团块状、致密的黑色素,微血管较多。真皮疏松层中分布着黏液腺和颗粒腺,黏液腺多于颗粒腺。牛蛙皮肤肥大细胞主要分布于真皮疏松层和皮下层,且多为长条形。真皮致密层呈阿利新蓝-PAS染色强阳性,表皮与真皮交界处以及真皮疏松层和致密层交界处也有强阳性带。多巴氧化酶法染色结果表明,无黑色素分布的表皮层有许多弥散、细小的阳性棕黑色颗粒状色素,而有大块天然黑色素分布的真皮疏松层阳性颗粒色素较少。结果提示,牛蛙皮肤可通过腺体、肥大细胞和黑色素发挥重要的免疫防御和保护作用。     

Effect of dietary potassium on absorption of magnesium and other macroelements in sheep fed different levels of magnesium

Two metabolism trials were conducted with 24 crossbred wether lambs. Two levels of Mg (.1 and .2%) and four levels of K (.6, 1.2, 2.4 and 4.8%) were fed in a 2 x 4 factorial arrangement of treatments. Each trial consisted of a 10-d preliminary period followed by a 10-d collection of feed, feces and urine. Increasing levels of dietary K resulted in a linear increase in fecal Mg excretion and a linear decrease in Mg absorption. A large depression in Mg absorption occurred when K was increased from 1.2 to 2.4% with a further decrease when K was increased to 4.8%. Lambs fed the high level of Mg (.2%) absorbed and retained more (P less than .05) total Mg (g/d, but not percentage of intake) compared with the low magnesium level (.1%). Dietary Mg did not affect the amount of K excreted, absorbed or retained. Increasing the level of dietary K resulted in a linear increase in urinary, fecal and total K excreted, absorbed and retained (P less than .05).     

粉碎机锤片的研究

锤片式粉碎机,由于其结构简单,被广泛采用。它是饲料厂电耗较高的机械,一般占粉料生产总能量的2/3,占颗粒料生产总能量的1/3多。因而如何使它增效节能,是饲料机械中的重要研究课题。不少人为此付出了大量的心血,推导了不少公式,做了不少实验。锤片是粉碎机中的核心工作部件,饲料粉碎全靠它。它对粉碎机效率影响最大,因而人们对锤片也做过专题研究。     

Effect of supplemented magnesium from magnesium oxide or dolomitic limestone upon digestion and absorption of minerals in sheep

Three metabolism trials were conducted with six lambs fitted with abomasal and ileal cannulae to determine the site of supplemental Mg absorption when supplied as dolomitic limestone or magnesium oxide. Magnesium intake was 1.09 g/d for the lambs fed the control diet and 2.21 and 2.10 g for those fed the dolomitic limestone and magnesium oxide supplemented diets, respectively. Irrespective of its source, the major site of Mg absorption was the preintestinal region. Magnesium was secreted in the small intestine in lambs fed all three diets. Magnesium supplementation resulted in an increase (P less than .05) in preintestinal Mg absorption, with magnesium oxide having the highest value. Supplementation had no effect (P greater than .05) on secretion or absorption of Mg from the small and large intestines or total retention of Mg. With all three diets, the major site of Ca absorption was the stomach region with additional absorption taking place in the large intestine. Calcium was secreted in the small intestine of lambs fed all treatments. Generally, K, Na and P were secreted in the preintestinal region and absorbed from the small and large intestines. The major site of K and P absorption appeared to be the small intestine and for Na, the large intestine. Serum minerals were unchanged (P greater than .05) due to treatment, but the levels of Mg, K and inorganic P tended to be higher in lambs supplemented with either of the Mg sources. It appears that the greater utilization of Mg from magnesium oxide vs dolomitic limestone is due to greater absorption of Mg from the forestomach region.     

比格犬甲状腺显微与超微结构的观察

应用光镜和透射电镜技术，观察了3～6月龄比格犬甲状腺的显微和超微结构。结果表明，比格犬甲状腺实质由滤泡和滤泡旁细胞构成。滤泡呈圆形或椭圆形，直径20．22～220．00μm，平均90.80μm；由单层立方上皮细胞围成，细胞高度3．04～7.11μm，平均5.18μm，电镜下可见功能状态不同的两型滤泡上皮细胞；滤泡旁细胞很多，直径4．40～8．82μm，平均6．23μm，位于滤泡之间或镶嵌于滤泡上皮细胞之间，也可聚集在一起形成滤泡样结构，胞质内含有大量的分泌颗粒，电镜下也可见两种类型的滤泡旁细胞。