对不定积分的两类换元积分法的对比研究

换元积分法是求解不定积分问题比较常用的方法。而换元积分法有两类。两类换元法有什么区别,分别适用于什么样的情形,一些初学者往往搞不清楚这些问题。本文对两类换元积分法做了对比研究。     

不定积分中两种积分方法的区别与联系

本文针对不定积分中积分方法选择这一教学难点,从定义入手,分析了第一换元积分法和分部积分法的特征。根据题目选择合适的积分方法提供了思路。最后,通过例题对两种积分方法的选择进行了举例说明。     

关于第一类换元积分法的教学探讨

不定积分是高等数学中的一个重点内容,而第一类换元积分法又是不定积分中的难点知识。文章针对《高等数学》教材中第一类换元积分法,提出了一种简明有效的教学方法,帮助学生迅速地凑出微分解题,为进一步的学习奠定基础。     

浅谈定积分与二重积分中的统一解题技巧

积分学是高等数学的主要分支。定积分与二重积分的概念和计算是积分学的重要组成部分,其在在几何、物理、概率统计等方面有着重要应用。二重积分作为定积分的推广,其二者有着共同的解题技巧,包括利用几何意义、对称性、换元法来简化定积分与二重积分的计算。     

广安实施生猪换种工程的探索

1 推进生猪换种工程的措施 1.1 以积极的扶持政策激励换种 2002年以来,广安市共兑现生猪换种补助资金2734万元.从2005年开始,市上又出台了对省、市确定的贫困村贫困户改扩建圈舍补助政策,补助50元/m2.两年全市有1025户贫困户,改造及扩建圈舍28773 m2,补助金额15243万元.     

再议重积分计算中积分限的确定

在高等数学教学中,重积分的计算是教学重点亦是难点。而在重积分的计算中积分限的确定是关键,文中结合笔者的教学体会讨论重积分计算中积分限的确定问题。鉴于初学者易将积分限为变数的情形误当做积分限为常数的情况,文中重点讨论了积分区域为何种形状时,二次或者三次积分的各积分限才能都取常数。文中所做讨论的结果若为初学者借鉴,可有效避免在重积分的计算中出错。     

Matlab在三重积分计算的教学设计中的可视化应用

三重积分的计算是高等数学中的难点之一,针对三重积分的计算问题,笔者在教学设计环节上狠下功夫,借助一只土豆,从理论上形象化的讲述了计算三重积分的投影法和截面法,接着对于具体的实例我们借助Matlab强大的绘图功能实现三重积分积分区域的图形绘制,同时运用Matlab强大的符号计算功能实现积分的快速计算,使积分的计算不再晦涩难懂,使学生不再对积分的计算望而生畏,提高学生学习高等数学的兴趣。     

巧用口诀解决分部积分法

本文主要归纳总结分部积分法计算不定积分的三种类型,并对每一种类型总结出简单易记的口诀方便选定u(x)和v(x)计算。     

影响奶牛饲养效益的几个指标

1效益的计算收入部分。1头优质奶牛日产25千克鲜奶,按现在市场价格每千克1.9元计算,每天收入47.5元。1头奶牛每年产奶期按300天计算,收入就是47.5×300=14 250元。按每两年产1公1母计算,公犊牛每头300元,母犊牛4 000元,平均每年收入为2 150元。两项合计,总收入为14 250+2 150=16 400元。     

Rogowski线圈电流测量系统中数字式积分的设计

介绍了外积分Rogowski线圈的数字积分方法,分析了模拟和数字两种积分器各自的性能,用MATLAB软件对以上各参数进行了仿真计算,设计了用于工频暂态大电流测量的数字式Rogowski线圈测量系统,并在暂态电流下进行了试验,结果表明用数字积分方法比模拟积分方法更好。     

商会自治的基石——商会自治规范研究

在现代法律秩序中,商会自治规范是制定法的基础和必要的补充,甚至在某些方面替代了制定法;商会自治规范主要包括商会组织规范、行为规范、惩罚规范以及争端解决规范等;其效力仅及于其内部成员;商会自治规范和制定法之间存在冲突,但也存在整合的基础。     

癸氧喹酯干混悬剂含量测定的改进

采用高效液相色谱法测定癸氧喹酯干混悬剂的含量,在2-250μg/mL范围内,峰面积的常用对数与进样量浓度的常用对数呈良好的线性关系,R^2=1(n=5),平均回收率为99.24%~99.51%,RSD在0.05%~0.28%。此方法分析时间短,样品前处理简便、定量结果准确,重现性好,结果满意,为其质量控制提供了依据。     

猪毛色遗传的研究进展

本文概述了猪的毛色类型、猪的毛色遗传模式,着重综述了猪毛色基因分子基础的研究进展,指出存在问题并就未来发展方向做了思考。     

Comparison of 2 methods of centesis of the bursa of the biceps brachii tendon of horses

REASONS FOR PERFORMING STUDY: Centesis of the bicipital bursa using an 8.9 cm long spinal needle has been reported but the alternative of employing a 3.8 cm long hypodermic needle requires validation. OBJECTIVE: To compare the efficacy of 2 different methods of centesis of the bicipital bursa and to evaluate the usefulness of ultrasonographic imaging to determine the location of solution administered when centesis of the bursa is attempted. METHODS: For Trial 1, 6 clinicians, who had no previous experience of centesis of the bicipital bursa, attempted to inject a solution composed of an aqueous radiopaque contrast medium and physiological saline solution (PSS) into the bicipital bursae of 2/12 horses using the previously described distal approach to inject one bursa and a proximal approach to inject the contralateral bursa. The bicipital tendon and bursa were examined ultrasonographically before and after injection; and both shoulders were examined radiographically to identify the location of the medium. In Trial 2, another 6 clinicians, also with no previous experience of centesis, repeated Trial 1, using 6 horses, but the radiopaque contrast medium was mixed with air instead of PSS. RESULTS: Accuracy of centesis using the proximal approach was 39% and that of the distal approach 28%. Ultrasonographic examination of the shoulder allowed the location of solution and air to be accurately predicted in all 12 shoulders examined. CONCLUSIONS: Clinicians who have had no previous experience performing centesis of the bicipital bursa are unlikely to be successful in centesis using either approach. Radiographic examination after injecting a radiopaque contrast medium may be necessary to assess the success of centesis especially if bursal fluid is not obtained during centesis. Injecting air along with the radiopaque contrast medium provides more accurate ultrasonographic confirmation of centesis and better radiographic definition than does injection without air.     

不同样本商品蜂蜜中硒含量的测定

用硝酸和高氯酸消化蜂蜜,使硒游离出来,在微酸性环境下,硒和2,3-二氨基萘(DAN)生成有较强荧光的物质,用环己烷萃取,在激发波长378nm,荧光波长518nm处测定其荧光强度。蜂蜜中硒含量范围:0.10～0.82μg/g。表明:蜂蜜应视为天然富硒营养品。     

乳酸杆菌益生作用机制的研究进展

乳酸杆菌作为益生菌广泛用于人和动物。本文综述了乳酸杆菌改善宿主健康的机制。乳酸杆菌可通过产生抗菌物质如乳酸、过氧化氢、细菌素,或者通过竞争营养或肠道黏附位点来抑制致病菌;通过诱导黏附素的分泌或阻止细胞凋亡而增强肠道的屏障功能,从而保护肠道。文章重点讨论了乳酸杆菌表面成分（表面蛋白、脂磷壁酸和肽聚糖）与肠道受体（Ｃ型凝集素受体、Ｔｏｌｌ样受体和 Ｎｏｄ样受体）,阐述了他们结合后启动免疫调节信号,调控肠道免疫功能以发挥改善健康作用的机制。     

中华人民共和国农业部公告 第267号

为贯彻落实《兽药生产质量管理规范》(简称《兽药GMP》),进一步推动兽药GMP实施进程,我部制定了《兽药生产质量管理规范检查验收办法》,现予公告。本公告自2003年6月1日起施行。附件:兽药生产质量管理规范检查验收办法二○○三年四月十日第一章 总则 第一条 为推动《兽药生产质量管理规范》(以下简称兽药GMP)的实施,规范兽药GMP检查验收工作,制定本办法。 第二条 农业部负责全国兽药GMP管理和检查验收工作;负责制修订兽药GMP检查验收管理规定;负责兽药GMP检查员队伍建设和监督管理工作,负责国际兽药贸易中GMP互认工作。 …     

鸡败血支原体垂直传播模式及其阻断方法

以国际标准强毒Ｒ株人工感染非免疫产蛋鸡,定时扑杀,分别从鼻窦、眶下孔、气管、肺、气囊、卵巢和输卵管分离ＭＧ,并收集感染鸡所产蛋分离ＭＧ。结果表明,人工感染４８小时后上、下呼吸道及肺已被全面感染,９６小时气囊已被感染,１２０小时输卵管已能分离到ＭＧ,卵巢始终分离不到ＭＧ。人工感染鸡自１４４小时便能在其所产蛋中分离出ＭＧ。药物治疗能在７２小时内消除感染,油乳剂苗则需２４天后逐渐降低蛋内ＭＧ分离率,药物卵内注射、种蛋药浴、高温处理均能杀死卵内ＭＧ,但以研制的种蛋浸泡剂药浴效果为最好。     

Effects of size of ingestively masticated fragments of plant tissues on kinetics of digestion of NDF

Ingestively masticated fragments were collected and sized via sieving. Different sizes of esophageal masticate and ruminal digesta fragments, and ground fragments of larger masticated pieces were incubated in vitro, and undigested NDF remaining at intervals of up to 168 h of incubation was determined. The ruminal age-dependent time delay (tau) for onset of digestion of NDF was positively correlated (P < 0.004) with the mean sieve aperture estimated to retain 50% of the fragments between successive sieve apertures (MRA). Degradation rate of potentially degradable NDF (PDF) and level of indigestible NDF were not related (P > 0.10) to MRA of masticated and ground fragments. Estimates of tau were positively related to MRA, with slopes of bermudagrass < corn silage < ruminal fragments of corn silage. It was concluded that fragment size-, and consequently, ruminal age-dependent onset of PDF degradation of a mixture of different fragment sizes results in an age-dependent rate of degradation of the more rapidly degrading of two subentities of PDF. Models are proposed that assume a tau before onset of simultaneous degradation of PDF from two pools characterized as having gamma-modeled age-dependency and age-constant rates. The ruminal age-dependent pool seems to be associated with the faster-degrading pool, and its rate parameter increases with range in MRA in the population of fragments. Conceptually, the ruminal age-dependent rate parameter for PDF degradation seems to represent a composite of several effects: 1) effects of the size-dependent tau; 2) range in MRA of the population of ingestively masticated fragments; and 3) subentities of PDF that degrade via more rapid age-dependent rates compared with subentities of PDF that degrade via age-constant rates. The estimated fractional rates of ruminative comminution of ingestively masticated fragments (0.060 to 0.075/h) were of a magnitude similar to the mean fractional rates of PDF digestion (0.030 to 0.085/h), which implies that ruminative comminution may be first-limiting to fractional rate of PDF digestion. The in vivo roles of ingestive and ruminative mastication of fragments on PDF degradation must be considered in any kinetic system for estimating PDF digestion in the rumen. These results and others in the literature suggest that the rate of surface area exposure rather than intrinsic chemical attributes of PDF may be first-limiting to degradation rate of PDF in vivo.