基于泵吸效应的电磁驱动配气机构温升抑制方案研究

根据动圈式电磁驱动配气机构的结构特点和工作原理提出了一种温升抑制方案:利用动圈的泵吸效应,以环形切片作为开关阀片,在无需额外动力源驱动的前提下能够提升动圈与永磁体之间气隙内的气体流量与速度,从而有效强化气隙表面的对流传热效果。通过建立流动区域的数值模型,仿真分析了电磁驱动配气机构工作循环中阀片的响应规律以及气体流动状态,据此对方案结构进行了改进,通过更换材质减轻了阀片的质量并优化了阀片行程。最后开展了配气机构长时间工作下的温升测试试验,结果表明,改进后的方案对执行器温升抑制效果明显,在测量工况下各测量点中最高温升下降12.1℃。     

Interfering with regular meiotic behaviour in Avena sativa as a method of incorporating the gene for mildew resistance from A. barbata

Summary The regular meiotic behaviour of the cultivated oat Avena sativa (2n=6x=42) is genetically controlled. The factors which control the diploid-like meiotic behaviour also restrict the amount of pairing that occurs between alien chromosomes and their homoeologues in A.sativa, and hence increases the difficulties of introducing desirable variation from wild species into the cultivated oat. A genotype of the diploid species A.longiglumis which interferes with the regular meiotic behaviour of A. sativa can be used to induce pairing between alien chromosomes and their corresponding chromosomes in A. sativa. Using this procedure the dominant gene conferring mildew resistance has been transferred from the tetraploid weed species A. barbata into the cultivated oat.     

基于经验模式滤波与循环神经网络的水锤压力信号预测

为准确预测水锤信号变化规律,实现对水锤冲击强度和能量等特性的提前预判,针对水锤冲击信号提出了一种基于经验模式分解(empirical mode decomposition, EMD)和循环神经网络(recurrent neural network, RNN)的模型预测方法.首先,通过EMD获取具有不同频率的IMF分量,根据水锤信号的频域特性剔除高频噪声分量并重构信号以实现滤波,滤波后信号能量损失不足0.1%;进而,建立了基于RNN模型的时间序列预测模型,搭建试验平台获取水锤冲击信号,完成了RNN模型的训练和参数调节;随后,对不同流速下水锤冲击信号进行序列预测,在测试集与训练集流速不同条件下,得到了准确的预测结果,表现出一定泛化能力.对比分析预测水锤信号与实际信号,得到R²系数大于0.990 0,幅值和能量损失不足1%,验证了所提出方法的正确性,主要结论和建模方法可为各类输水系统的风险评估、管路监测和健康管理提供理论指导和技术手段.     

高校课堂自主学习法的理论与实践

针对目前高校课堂教学指导思想、手段、效果等存在的问题，本从“学”的角度出发，综合考虑学生的心理、生理特点，提出使学生从传统课堂的被动学习过程，变为在教师引导下合理、有序的自主学习过程，做到因材施教，有的放矢。实现一种被广大学生所接受的“自愿、自主、自理”的课堂教学方法，该方法以激发学生学习兴趣、活跃课堂气氛为表现形式，以牢固掌握所学知识，自觉向深度和广度扩展为最终目标。     

基于迁移学习和Mask R-CNN的稻飞虱图像分类方法

针对当前稻飞虱图像识别研究中自动化程度较低、识别精度不高的问题,提出了一种基于迁移学习和Mask R-CNN的稻飞虱图像分类方法。首先,根据稻飞虱的生物特性,采用本团队自主研发的野外昆虫图像采集装置,自动获取稻田稻飞虱及其他昆虫图像;采用VIA为数据集制作标签,将数据集分为稻飞虱和非稻飞虱两类,并通过迁移学习在Res Net50框架上训练数据;最后,基于Mask R-CNN分别对稻飞虱、非稻飞虱、存在干扰以及存在黏连和重合的昆虫图像进行分类实验,并与传统图像分类算法(SVM、BP神经网络)和Faster R-CNN算法进行对比。实验结果表明,在相同样本条件下,基于迁移学习和Mask R-CNN的稻飞虱图像分类算法能够快速、有效识别稻飞虱与非稻飞虱,平均识别精度达到0. 923,本研究可为稻飞虱的防治预警提供信息支持。     

LAMP法鉴定奶牛早期胚胎性别的效果研究

本试验利用Lamp法对28枚鲜胚进行了性别鉴定,将其中13枚雌性胚和3枚雄性胚胎给受体牛移植,妊娠率达45.5%,性别鉴定的准确率为100%。说明Lamp法用于奶牛早期胚胎性别鉴定是切实可行的。     

A new alternative for embryo transfer and artificial insemination in mares: ultrasound-guided intrauterine injection

A transvaginal ultrasound-guided intrauterine injection (IUI) technique was developed for embryo transfer and for injection of small quantities of sperm in mares. The target area of a horn was positioned by transrectal manipulation against the wall of the vaginal fornix over the face of a transvaginal transducer. A needle with a catheter containing the embryo or semen was inserted through the needle guide of the transducer into the uterine lumen. The tips of the needle and catheter, the movement of the catheter in the uterine lumen, and the ejection of fluid was monitored on the ultrasound screen. Pregnancy rate 15 days after ovulation for the IUI embryo transfer technique (30/39, 77%) was similar to the pregnancy rate for transcervical (TC) embryo transfer (30/38, 79%). The pregnancy rate for IUI insemination of 20 × 10⁶ progressively motile sperm into the tip of the uterine horn ipsilateral to ovulation was 5/10 (50%). Results indicated that the IUI approach is a viable alternative for embryo transfer. Results also supported the potential of IUI for insemination of low numbers of sperm, but more extensive studies with various doses of sperm are needed.     

我国农村土地流转制度的现实困境与改革创新

首先阐释了农村土地流转的含义及促进农村土地流转制度发展的意义,然后重点分析我国农村土地流转制度现实困境并提出相关改革创新的对策。     

Effects of heat stress on the endometrial epidermal growth factor profile and fertility in dairy cows

The endometrial epidermal growth factor (EGF) profile is an indicator of uterine function and fertility in cattle. The present study aimed to investigate the effects of heat stress on the endometrial EGF profile and fertility in lactating Holstein cows. The endometrial EGF profiles of 365 cows in the Hokkaido and Kyushu regions were examined between June and September (heat stress period, n = 211) and between October and January (control period, n = 154). EGF profiles were investigated using uterine endometrial tissues obtained by biopsy 3 days after estrus (Day 3). The proportion of cows with an altered EGF profile was higher between June and September than between October and January (41.2 vs. 16.2%, P < 0.05). The effects of rectal temperature on Days 0 and 3 on the endometrial EGF profile were also assessed in cows (n = 79) between June and September in the Kyushu region. A single embryo was transferred to cow on Day 7 to evaluate fertility (n = 67). Regardless of the rectal temperature on Day 3, the proportion of cows with an altered EGF profile was higher (64.1 vs. 30.0%, P < 0.05) and the pregnancy rate after embryo transfer (ET) was lower (26.7 vs. 51.4%, P < 0.05) in cows with a rectal temperature ≥ 39.5°C on Day 0 than in cows with a rectal temperature < 39.5°C on Day 0. The present results indicate that alterations in the endometrial EGF profile induced by an elevated body temperature on Day 0 contributed to reductions in fertility in lactating dairy cows during the heat stress period.