用数学归纳法证明离散数学的有关结论

鉴于涉及自然数,应用数学归纳法证明了离散数学有关集合中关系及其性质、树及其性质等结论。由于降低了证明过程的复杂性,使推理过程更严谨、清晰、简单。     

高职数学教学的几个问题

针对高等职业教育的特点，结合本院高职院高等数学的教学实践，从教材选取、课堂讲授和教学手段等方面探索了该课程教学的一些问题，以 地困材施教，改善教学效果。     

基于数学归纳法的空中加油辅机安排方案

针对飞机空中加油的辅机安排问题,我们讨论了如何通过最少的辅机数来实现往返运输物品的要求,利用线性规划和数学归纳法获得了主机的最远单程飞行距离与辅助发动机的数量之间的关系以及辅机的最佳组合方式,可以推广到同类问题的解决上。     

浅谈成人数学教学应着重解决的几个问题

成人教育具有特殊性,特别是数学教学,其本身的抽象性更会令学员难以接受。从教学实践上看,成人学员年龄较大,文化基础薄弱,程度参差不齐,新旧知识衔接不上,但他们学习目的明确,逻辑思维能力和分析解决问题能力比较强,这是有利的因素。针对这样的实际情况,提高成人数学教学质量,应该着重解决以下四个方面的问题。     

关于农机推广鉴定工作的几点思考

现阶段农机推广鉴定工作周期长、成本高,为适应农业农村现代化发展的需要,亟需改进农业机械推广鉴定工作模式,提高农机鉴定业务培训水平,以期为目前开展可靠性和适用性测试打开新的途径。     

关于Veljan-Korchmaros定理的推广及其应用

推广了Veljan—Korchmaros定理，并应用它推广了n维Euler不等式。     

营养学上需要修改的几个问题

随着医学科学的发展、现代营养学研究的深入，曾经一度流行的营养观点证明存在着一定的误区，本文特别针对脂肪类存在的误区提出应进行修改。     

整数和集的渐近密率

设A和B都是自然数的集合,C是它们的和。A的渐近密率为α。假定B是自然数的一个渐近基底,λ是B的渐近平均阶数。C=A B的渐近密率为γ,得到了用α和λ估计γ的几个定理。     

新型电磁感应加热辊

为满足纤维在高温条件下的牵伸定型要求,研发了电磁感应加热辊。电磁感应加热辊实现了高温加热,且升温快、加热均匀、温度控制简单、节省能源、保护环境。     

一种锯链链轴高频感应加热淬火机械装置

设计并制造了一台锯链链轴高频感应加热淬火机械装置.使用结果表明,该装置设计合理,动作可靠,经该装置处理的锯链链轴质量与国外同类锯链链轴相当.     

棉花枯萎病菌产角质酶的连续诱导

角质酶(EC3.1.1.74)是水解酶,可以降解角质产生脂肪酸,属于α/β水解酶,也可以水解甘油三酯等化合物.角质酶的应用十分广泛,但菌株对角质酶的表达量非常有限,因此提高角质酶表达量的研究具有广泛的理论与实践意义.角质酶是一种诱导酶,角质的存在能激活产该酶病菌的角质酶基因,诱导其高效转录表达.本实验经过角质诱导及诱导强度的变化,真菌的角质酶基因转录量大大增加,而未经过角质诱导的真菌角质酶基因转录量非常少.本研究中诱导棉花枯萎病菌的产酶量最高可以达到29.46U/mL,比未诱导的提高至4倍.     

水性介质中植物油氧化诱导时间的测定

开发了一种绿色环保的测定植物油氧化诱导时间的体系。对流动体系的油水体积比、流量、加入铜丝长度等条件进行了优化,以不同氧化程度的橄榄油与p H 7的磷酸缓冲溶液(PBS)混合分离的水相为测量对象,以还原氧化石墨烯修饰的玻碳电极(r GO/GCE)为工作电极,利用交流阻抗法对其阻抗进行测定。结果表明:最佳油水体积比为1∶1,最适流量为1.68 m L/min,铜丝长度40cm;交流阻抗法能够灵敏地测量橄榄油自动氧化过程中产生的易溶于水的物质所引起的水相溶液阻抗的变化;交流阻抗法与国标法得到的氧化诱导时间的相对偏差小于5%,且两种方法的测定结果无显著性差异。因此,通过建立的水相体系可以准确地对植物油的氧化诱导时间进行测定。     

磁力做功与电磁感应现象中的能量转换

根据磁力做功的特点,通过对感应电动势与磁场能量变化关系的分析,得出磁力做功是磁场能量改变的量度、电磁感应现象是能量转换的过程的结论。     

Response to lactation induction differs by season of year and breed of dairy ewes

Lactation artificially induced (ART) by steroid hormones and natural lactation (NAT) after lambing were compared in 2 dairy sheep breeds (Manchega and Lacaune) in 2 experiments conducted during winter and spring. In experiment 1, ART ewes (14 Manchega and 9 Lacaune) were induced into lactation in winter by the standard protocol, which consisted of s.c. injections of estradiol and progesterone administered in 2 portions daily from d 1 to 7. Hydrocortisone acetate was injected s.c. daily on d 18 to 20. Milking was initiated on d 21 and continued for 13 wk. A similar group of NAT ewes was selected for the contemporary comparison of NAT vs. ART lactation. All Lacaune ewes, but only 3 of the 14 Manchega ewes (21%), were successfully induced into lactation. Despite the successful induction of lactation in Lacaune ewes, milk yield was much lower than that obtained in NAT lactation (1.23 ± 0.14 vs. 2.51 ± 0.15 L/ d). Milk composition from wk 5 to 13 did not differ between groups, except for whey protein, which was greater in ART than in NAT ewes (1.47 vs. 1.25%). In experiment 2, 19 Manchega ewes were divided into 2 groups and induced into lactation in spring by using the standard induction protocol, similar to that used in experiment 1 (control, n = 9), or the standard protocol modified with bovine somatotropin (bST, 250 mg/ewe on d 11; n = 10). Manchega ewes had an improved response to the standard protocol of lactation induction in spring compared with winter. Milk yield in bST-treated Manchega ewes was 98% greater than that in control ewes (402 ± 85 vs. 203 ± 86 mL/d). The use of bST during mammogenesis did not affect milk composition. In conclusion, marked differences between Manchega and Lacaune dairy ewes were observed in their response to lactation induction when using the standard protocol during different photoperiod conditions. The Manchega ewes were unable to establish lactation in winter but were able to do so in spring. The response to lactation induction in dairy ewes seems to be related to their endogenous levels of prolactin and growth hormone, the use of which should be explored more deeply in future research.     

钢丝感应加热炉的设计

钢丝感应加热是电、磁、热、相变相互作用的复杂动态过程,感应加热炉的设计应在满足加热工艺要求的前提下,使整个系统效率最高、损耗最低。通过对感应加热时电流趋肤效应的分析,指出加热钢丝直径与透入电流深度之比在3～6比较合适,针对钢丝等磁性材料在加热过程中随温度的增加相对导磁率减小的特点,说明钢丝加热在居里温度点以下选用较低的频率,在居里温度点以上用较高频率,可以提高感应加热炉的效率。给出感应加热时不同直径钢丝在不同温度时的最佳频率,设计出处理Φ7.1～12.6mm钢棒的感应加热生产线,生产线采用长而紧凑的感应器以减少端部磁场泄漏,并严格控制钢丝与感应器的同心度和空气间隙。     

The influence of different single dietary sources on moult induction in laying hens

An investigation was carried out to assess the possibility of using single dietary sources as alternatives to feed deprivation for the induction of moult in commercial laying hens. The study involved six dietary groups of 29 laying hens: unmoulted, dried tomato pomace, alfalfa meal, rice bran, cumin seed meal and feed withdrawal. The birds received the above diets during the moulting period (11 days), and body weight loss and ovary weight regression were measured. Post‐moult production parameters (number of eggs produced per hen per day, egg weight, shell weight, yolk colour and Haugh unit) were measured for 12 weeks. Results showed that all dietary sources were as effective as feed withdrawal in causing ovary weight regression in birds. Birds provided with tomato pomace or alfalfa showed lower weight losses than feed‐deprived birds at the end of the moulting period. Hens moulted by tomato pomace or alfalfa exhibited post‐moult levels of egg production over a 12 week period that were superior to those of hens moulted by feed withdrawal. Post‐moult eggs laid by hens moulted by all dietary sources were of comparable quality to eggs from feed‐deprived hens and superior to those from unmoulted hens. As fibrous feeds with low metabolisable energy and an appreciable amount of protein, dried tomato pomace and alfalfa meal may be fed to hens on an ad libitum basis for effective moult induction while reducing the stress of severe starvation and retaining comparable egg quality and production. Copyright © 2007 Society of Chemical Industry     

基于粗糙集的ID3决策树算法改进

针对ID3等传统的决策树算法通常采用单个属性作为分枝判断依据,导致生成树的规模大、形成的规则较难理解的问题,提出了一种以多变量作为结点属性判断条件的算法。该算法利用粗糙集中属性依赖的特性,选择信息系统中条件属性相对决策属性的核属性作为多变量结点属性,使用相对泛化的概念辅助分枝过程,进而生成多变量决策树。通过实例分析与传统的ID3算法进行比较,证明了改进算法的高效性。