河北省玉米生产现状及主推品种分析

对河北省玉米生产现状及河北省主推玉米杂交种种质基础进行了分析,指出了河北省玉米生产中存在的主要问题,提出了解决问题的方法,以期对促进河北省玉米生产发展提供参考。     

分洪区口门流量淹没系数的研究

采用平面二维数学模型,计算分析了分洪区口门的堰流流量系数和淹没系数的变化过程。结果表明,在自由溢流时,分洪区口门的堰流流量系数和正向堰流的流量系数基本一致。在淹没溢流时,在淹没度为0.8～0.98范围内,分洪区口门堰流的淹没系数与普通水力学的正向堰流的淹没系数基本一致;对淹没度在0.98～1.0范围(正向堰流不存淹没度为0.98～1.0范围的堰流),通过数学模型的计算分析给出了淹没度在这个范围内的分洪区口门堰流的淹没系数。所得结果可以为分洪区口门的流量计算作参考。     

Racing performance following the laryngeal tie-forward procedure: a case-controlled study

REASONS FOR PERFORMING STUDY: The laryngeal tie-forward procedure (LTFP) is becoming widely used for correction of dorsal displacement of the soft palate (DDSP) despite the absence of an evidence-based assessment of its efficacy. HYPOTHESES: The LTFP returns racing performance to preoperative baseline levels and to that of matched controls; and post operative laryngohyoid position is associated with post operative performance. DESIGN AND POPULATION: Case-controlled study of racehorses undergoing a LTFP for dorsal displacement of the soft palate at Cornell University between October 2002 and June 2007. METHODS: The presence of at least one post operative start and race earnings ($) were used as outcome variables. Controls were matched by age, breed and sex from the third race prior to surgery. A novel radiographic reference system was used to determine laryngohyoid position pre- and post operatively. Data for definitively and presumptively diagnosed cases were analysed separately. RESULTS: During the study interval, 263 racehorses presented, of which 106 were included in the study; 36 had a definitive diagnosis of DDSP and 70 a presumptive diagnosis. Treated horses were equally likely to race post operatively as controls in the equivalent race. Treated horses had significantly lower earnings in the race before surgery than matched controls. The procedure moved the basihyoid bone dorsally and caudally and the larynx dorsally and rostrally. A more dorsal post operative basihyoid position and more dorsal and less rostral laryngeal position were associated with an increased probability of racing post operatively. CONCLUSIONS: Horses undergoing a LTFP are as likely to race post operatively as matched controls. The procedure restores race earnings to preoperative baseline levels and to those of matched controls. POTENTIAL RELEVANCE: This study provides strong evidence supporting the use of the LTFP in racehorses. Further work is needed to determine the relationship between laryngohyoid conformation and nasopharyngeal stability in horses.     

WalkawayVSP试射法正演方法研究

介绍了Walkaway VSP观测系统及Walkaway VSP地震波类型。结合模型的理论基础,以及射线理论,阐述了任意倾角多界面情况下,Walkaway VSP射线追踪模型的制作方法,论述了试射法原理。结合Walkaway VSP模型,使用 Fortran语言编写程序,实现了Walkaway VSP试射法正演模拟。利用Fortran编写的程序试算了3个模型,成功得到了任意倾角多界面情况下其射线追踪结果图和合成地震记录图,验证了程序算法的正确性和有效性。     

番茄收获机械手工作空间分析与仿真

采用Denavit-Hartenberg坐标系,通过齐次变换法建立了7自由度番茄收获机械手的正运动学方程,利用蒙特卡洛方法对机械手工作空间进行仿真和分析.结果表明,番茄收获机械手工作空间内部工作点密集且分布均匀,能够满足番茄采摘高效作业的要求.蒙特卡洛法求解速度快,能够简单、直观形象地描绘机械手的工作空间.     

氮肥施用前移对遮荫下棉花光合特性及产量的影响

为探讨新疆南疆地区果棉间作下棉花适宜的氮肥追施模式,设置不施氮肥(N0)、氮肥追施至初花期结束(N1)、氮肥追施至盛花期结束(N2)和正常追肥(N3)。结果表明:遮荫下氮肥追施至盛花期结束(N2)提高了棉花盛花期后主茎功能叶潜在活性(Fv/Fo)、最大光化学效率(Fv/Fm)和光化学猝灭系数(q P),有利于光合色素将捕获的光能以较快的效率及速度转化成化学能,为碳同化提供更加充足的能量;同时增加棉花花铃期PSII开放程度和光合电子传递速率(ETR),促进实际光化学效率(ΦPSII)和净光合速率的提高,降低了初花期非辐射能的耗散,可将捕获的光能更充分地进行光合生产,提高了花铃后期非辐射能的耗散,可为棉铃输送较多的光合产物,增加了单株铃数和铃重,提高了产量。     

淡水鱼头尾与腹背定向装置的设计与试验

为了给6PYL-305型剖鱼机制造一种自动喂料设备,该文设计了一种淡水鱼头尾与腹背定向装置,并以鲢鱼为定向对象,根据鲢鱼的摩擦特性,通过理论分析,分别对利用倾斜振动台面实现头尾定向和利用渐变滑道实现腹背定向过程的机理进行了探讨,并采用质量为0.75～1.0 kg的新鲜鲢鱼进行了试验研究。理论分析和试验结果均表明,该定向装置可以实现鲢鱼的头尾和腹背定向。并对影响鱼体头尾定向因素：进入振动台面的体位、电动机频率、激振力和筛面角,以及影响鱼体腹背定向因素：滑道夹角、电机频率、激振力和滑道倾斜角分别进行了试验研究,得出各因素对定位时间均具有显著的影响;头尾定向的总定位率达97.53%,定向动作可在0.65～3.75 s内完成;腹背定位的总定位率达97.5%,定向动作可在0.39～5.03 s内完成。研究结果可为淡水鱼连续化加工中定向连续喂料设备的产品开发提供技术依据。     

用滑移线法解正挤压实心件的准确方法

现有文献用滑移线法求解正挤压实心件的单位挤压力,存在一些模糊概念。对此进行了评述,指出了存在的问题,并提出了求解单位挤压力的准确方法。该法概念清晰,结果正确。     

CSAMT法在包神铁路地基勘查中的应用

CSAMT法是在MT和AMT的基础上发展起来的一种人工源频率域测深方法,勘探深度适中、分辨率高、抗干扰能力强、工效高成本低廉,在工程物探中是一种行之有效的方法。讨论了基于V8系统的CSAMT法的原理、工作方法和资料解释处理,并应用于包神铁路复线乌兰木伦段地基勘查中,成功地解释了地基采空区的位置、埋深、范围,为包神铁路复线建设提供了依据。     

油茶果采摘机械臂工作空间分析与仿真

为了强化油茶果采摘机器人工作的稳定性,以自行研制油茶果采摘机器人为研究对象,通过对采摘机械臂结构进行分析,综合运用D-H表示法和圆柱坐标表示法建立机械臂数学模型,应用MatLab求解以该模型为基础建立的机械臂正运动学方程,仿真得到油茶果采摘机械臂工作空间。