植物基因工程的展望

为了庆祝建校35周年,本文以“植物基因工程的展望”为题,进行了简单的综述。内容涉及高等植物的基因结构,植物基因工程的方法步骤,植物基因工程的新进展以及植物基因工程的未来四个部分。借以宣传有关植物基因工程方面的知识。     

高校历史性的跨越对图书馆的影响及要求

文章概述了近几年高校办学在规模、数量、质量、水平和实力等方面的跨越，分析了高校历史性的跨越给图书馆带来的正面和负面的影响，并从“硬件”和“软件”两个方面提出了对图书馆的要求。     

加强国际科技合作提高研究水平--经济作物研究所国际合作回顾与建议

通过对黑龙江省农业科学院经济作物研究所开展与俄罗斯等东欧国家科技合作里程的回顾,阐述了合作取得的成果,提出了今后合作的建议.     

高密度压捆机插草机构的动态仿真

用传统方法对多体机构运动学分析较困难,本文利用ADAMS多体系统仿真分析软件对高密度压捆机插草机构进行了动态仿真,得出了满足设计要求的各构件的最优化尺寸,为插草机构及压捆机的结构改进提供依据。     

小型牧草收获机双动切割装置设计与运动分析

为了解决小型牧草收获机单动刀工作时存在的平衡能力差、切割速度低、容易卡滞堵塞、难以适应柔性茎秆牧草的问题,进行了小型牧草收获机切割装置机构的改进设计;采用了双曲柄连杆机构带动两组刀片彼此反向切割的双动切割装置机构;通过其运动分析,得到了割刀位移、速度、加速度与曲柄转角的关系,并对动刀片结构参数和动刀间隙进行了优化设计。通过双动割刀切割速比的分析,绘制了不同切割速比下的双动割刀运动切割图,表明减少重割区和漏割区面积的最佳切割速比为K=1.6。研究结果为牧草切割装置的进一步优化设计和试验提供了参考依据。     

DC electrical resistivity CT survey of deformation and damage law of coal floor

Abstract: Based on the general laws of the floor damage caused by coal mining, the response relation between the floor rock damage and its electrical resistivity are mainly discussed. Then, the principle and method of the direct current electrical resistivity CT surveying technology are introduced. The survey plan is made according to movement characteristics of mining rock strata in floor, and the dynamic direct-current resistivity CT survey is then applied to predict the damage depth of coal floor. In the return airway of face 1028 in Huaibei Mine, two boreholes were drilled in the coal floor, with a certain number of electrodes buried in the holes, the survey profile was formed between them. With characteristics of electric fields in rock strata in different time measured according to advance of working face, and its electrical resistivity values simulated inversely, the responses of rock strata to electrical resistance during the evolution of fractures were obtained and the damage depth of coal floor in face 1028 was determined to be 17m, which provides visual and effective technical parameters for the coal mining safety. Test results show that direct current electrical resistivity CT technique can detect coal floor mining damage evolution process effectively, and illustrate the floor deformation and damage in the process of mining, which is conducive to the water-inrush forecast, prevention and control.     

3-UrSR 6自由度并联机构位置分析

提出一种采用球面2自由度五杆作为驱动装置的3 - UrSR并联机构.对该机构自由度进行了计算,对机构的位置反解进行了分析和研究,并列出了正解的约束方程组.最后用反解验证了正解的正确性,给出了该机构的位姿分析的数值仿真实例及图形.     

Undulatory fish swimming: from muscles to flow

Undulatory swimming is employed by many fish for routine swimming and extended sprints. In this biomechanical review, we address two questions: (i) how the fish's axial muscles power swimming; and (ii) how the fish's body and fins generate thrust. Fish have adapted the morphology of their axial musculature for high power output and efficiency. All but the superficial muscle fibres are arranged along curved trajectories, and the myomeres form nested cones. Two conflicting performance goals shape the fibre trajectories of the axial muscles. Maximum power output requires that all fibres contract uniformly. In a bending fish, uniform contraction in a single myomere can be ensured by curved fibre trajectories. However, uniform strain is only desirable if all muscle fibres have the same contractile properties. The fish needs several muscle‐fibre types that generate maximum power at different contraction speeds to ensure effective muscle power generation across a range of swimming speeds. Consequently, these different muscle‐fibre types are better served by non‐uniform contractions. High power output at a range of swimming speeds requires that muscle fibres with the same contractile properties contract uniformly. The ensuing helical fibre trajectories require cone‐shaped myomeres to reduce wasteful internal deformation of the entire muscle when it contracts. It can be shown that the cone‐shaped myomeres of fish can be explained by two design criteria: uniform contraction (uniform strain hypothesis) and minimal internal deformation (mechanical stability hypothesis). So far, only the latter hypothesis has found strong support. The contracting muscle causes the fish body to undulate. These body undulations interact with the surrounding water to generate thrust. The resulting flow behind the swimming fish forms vortex rings, whose arrangement reflects the fish's swimming performance. Anguilliform swimmers shed individual vortex rings during steady swimming. Carangiform swimmers shed a connected chain of vortex rings. The currently available sections through the total flow fields are often not an honest representation of the total momentum in the water – the wake of carangiform swimmers shows a net backward momentum without the fish accelerating – suggesting that our current picture of the generated flow is incomplete. To accelerate, undulatory swimmers decrease the angle of the vortex rings with the mean path of motion, which is consistent with an increased rate of backward momentum transfer. Carangiform swimmers also enlarge their vortex rings to accelerate and to swim at a higher speed, while eel, which are anguilliform swimmers, shed stronger vortex rings.     

基于MATLAB曲柄滑块机构的运动学分析

MATLAB运动仿真技术是借助计算机技术和MATLAB软件技术平台发展起来的一种分析机械运动参数的技术。以往解析法的计算主要依靠C语言或VB语言,这些语言指令繁琐,语句结构复杂,而MATLAB程序语言简洁更易操作。因此,本文就是以曲柄滑块机构为例,借助MATLAB运动仿真技术对其进行分析,试图通过其可视化功能将曲柄滑块机构的运动参数用图像的方式表达出来。