水稻种绳捻制机的研制与试验

介绍了一种水稻种绳捻制机,该机主要由排种机构、捻绳机构和卷绳机构3部分组成。它将稻种按照要求的穴距和每穴粒数卷在2cm宽的(无纺布)纸带内,制成种绳,并将种绳卷成盘后待播。直播时,将卷好稻种的种绳盘挂在研制的种绳播放器两侧,将绳的端部固定在地头,然后人工拉动种绳播放器前进,1次完成开沟、放种绳、覆土等作业。试验结果表明,加工种绳的平均穴距为2.5cm,空穴率为1.5%,平均每穴粒数为1.48,种绳绕劲个数为43个/m,基本上达到了设计要求。但卷绳速度为0.8m/s,有待提高。水稻种绳直播技术的突出特点是实现了种绳捻制作业的工厂化和田间播种作业的轻型化。     

水稻直播机船底板下流体的数值模拟

利用有限元分析软件ANSYS中的计算流体动力学模块(FLOTRANCFD),对船底板下的流体进行模拟和分析,讨论在考虑形状损失和摩擦损失时,船底板下流体的流线和流动情况。通过对流体的仿真得出:船底板横挡板的前倾角对船底板下流体的流线和流量有较大的影响,并得出在倾角30o和60o时有较好的流动情况。     

用于直流传动控制系统的串行通讯

介绍了用Visual Basic提供的串行通讯控件，通过编程实现了PC机与应用单片机触发电路的直流传动系统的通信。     

水稻机械直播技术的试验研究

1993年，浙江省杭州市萧山区开始在不同镇乡、不同土壤性质的地块对引进的直播机进行可行性作业试验。经多年试用，对机器进行了选型和改进，在水稻直播的整地、种子处理、播种到排水、除草、肥水管理以及病虫害防治等整个生产过程，采用了相应的机械和措施。为此，针对水稻机械直播技术，揭示了机直播增产机理、技术特性及优越性．展望了该技术推广应用的发展前景。     

外开式汽油喷油器喷雾特性研究

在定容弹内,采用纹影和激光Mie散射技术研究了外开式压电晶体汽油喷油器使用汽油、正丁醇和乙醇时的喷雾特性。结果表明,外开式喷油器喷油形成的空心圆锥状喷雾结构由线状油束组成。喷油背压对喷雾的宏观形态影响较大。随着喷油背压的升高,喷雾中油线间隙减小并最终消失,同时喷雾贯穿度与面积均大幅减小,但喷雾锥角基本不随背压、燃料种类和时间的变化而变化。此外,随着背压的升高,喷雾横向贯穿度的减小程度大于轴向贯穿度,但是横向贯穿度始终大于轴向贯穿度。粘度较大的乙醇和正丁醇的轴向贯穿度大于汽油。横向贯穿度与喷油产生的涡流有关。涡流尺度越大,则横向贯穿度也越大。     

Electric Vehicle of Direct Torque Control System Based on TMS320LF2407 Controller

A fully digitized electric vehicle direct torque control system with DSPTMS320LF2407 controller is described. The system hardware and software structures are presented. The performance of the direct torque control system is studied by simulation with MATLAB. Based on the simulation of the induction motor, waveform of current, speed, torque and flux are obtained. The testing results are also presented. Experimental results show that the design is feasible.     

Recommendations on Shrinkage and Temperature Reinforcements in Concrete Slabs

The mechanism of shrinkage cracking is discussed with a simple member, which is fully restrained and subjected only to an axial restraining force caused by shrinkage, while a simple procedure is presented for the determination of the number and spacing of the cracks and the average crack width. With the simple model, some examples are shown to compare the provisions for minimum shrinkage and temperature reinforcement in GB 50010-2002 Code, ACI 318-02 Code and AS 3600-1988 Code. The results show that the provisions in GB 50010-2002 Code are too weak in comparison with the others. Finally, some recommendations are proposed.     

Comparison of DC Pollution Flashover Performance of Various Types of Long String Insulators

With the development of EHV/UHV DC transmission projects, it is inevitable to study DC pollution flashover performance of long insulator strings. The DC artificial pollution tests of five types of porcelain and glass insulators have been carried out in the artificial climate chamber. The paper analyzes the relationship between 50% flashover voltage U50 and string length, the relationship between U50 and salt deposit density, flashover voltage gradients and valid creepage distances of DC polluted insulators. Based on the test results of insulator strings of 5 - 23 units, there are linear relationship between the 50% DC flashover voltages and string length. The experimental results show that the pollution flashover performances of various types of insulators are different, and that the pollution degree exponents of polluted insulators are affected ainsulator materials and shapes, whose values are 0.3 to 0.36. Under the same pollution degree, the pollution performances of glass insulators have advantage of those of porcelain insulators with the same configuration and the flashover voltage gradient along creepage distance and valid creepage distances of glass insulators are higher than those of porcelain insulators.     

STATE VARIABLE METHOD FOR DYNAMIC SIMULATION OF HVDC SYSTEMS

A flexible mathematical model used for dynamic simulation studies of HVDC systems which is based on the stale variable method is presented, and the correspongding computer program has been implemented. Generality, easy to use, and suitable to run on microcomputers are the main features of the model and the computer program. Therefore the model is easy to be extended for application. An example is given in the paper to verily the coneclness of the model and the program.