类正弦VMSK调制的扩频技术

介绍了一种类正弦VMSK调制的扩频技术,利用直扩系统在抗噪方面的优势,从而大大提高了系统的性能。通过比较类正弦VMSK信号与MSK信号的功率谱密度,论证类正弦VMSK调制的超窄带性。最后在加性高斯白噪声(AWGN)信道中的模拟仿真,其结果说明了此技术的优越性。     

Bit‐induced asphyxia in the racehorse as a cause of sudden death

The prevention of sudden death requires removal of its cause and this is unknown. The author's hypothesis is that bit‐induced asphyxia, partial or complete, is a cause of sudden death. Antemortem data on bit‐induced asphyxia were compared with post mortem data on sudden deaths to explore a possible cause‐and‐effect relationship. Causal categories from sudden death necropsy data were reclassified. Those causing a horse to fall (cardiopulmonary failures) were considered primary effects and those resulting from a fall (CNS trauma and haemorrhagic shock) secondary effects. Cardiac failure from negative pressure pulmonary oedema caused by bit‐induced obstruction of the nasopharynx was consistent with the hypothesis. In 1988, asphyxia from recurrent laryngeal neuropathy was posited as a cause of exercise‐induced pulmonary haemorrhage (EIPH). It is now suggested that the bit is another cause of asphyxia; EIPH is a sign of negative pressure pulmonary oedema which, in turn, causes cardiac failure and sudden death. By breaking the airtight lip‐seal at exercise, a bit dissipates negative pressure in the oral compartments, destabilises the soft palate and obstructs the nasopharynx. Bitted rein pressure, kinking the airway and rendering parts of it flaccid, is a further cause of asphyxia. The data comparison supports a unifying hypothesis on 4 problems currently considered idiopathic; that the bit is an ultimate cause of palatal instability, dynamic collapse of the upper respiratory tract, EIPH and sudden death. Bitless training and racing trials are recommended as a means of demonstrating that bitless racing is possible, preferable and predicted to reduce the prevalence of all 4 problems.     

Torsional Vibration Simulation Analysis of Drilling String and Rock Bit

In this paper,the method of establishing the torsional vibration model of drilling string and rock bit and the process of simulation analysis are introduced.The interaction between bit and rock and elastic deformation of drilling string in the process of petroleum drilling which caused the torsional vibration of the drilling string and rock bit is main considered in establishing the model.The torsional model is solved by difference method.Based on the models,the simulation analysis software of drilling string and rock bit is designed,and simulation calculation and analysis of the tortional vibration of drilling string and rock bit under different conditions are computed,and the dynamic behavior and kinetics regularity of drilling string and rock bit in drilling are obtained.     

连续单粒式谷物在线水分测定仪的设计与试验

为了提高谷物干燥设备自动化水平和干燥后谷物品质,提出一种基于电阻法检测原理,测量稻谷、小麦和大麦的连续单粒式谷物在线水分测定仪。其主要由谷物取样机构、谷物采样机构和信号采集电路等部分组成。通过测量谷物单粒外形尺寸统计出谷物等效粒径。运用谷物等效粒径和谷物与金属表面的静滑动摩擦角,计算确定谷物取样机构中不锈钢制异向正弦螺旋杆的中径和螺距分别为16和9 mm。由螺旋杆与分粒拨刀组成的谷物取样机构,在剔除杂物和多余谷物的同时,使谷物以连续单粒的形式进入进料口。选定模数为0.4 mm斜纹表面滚花形式碾压辊作为碾压电极,测量10%~35%含水率范围内稻谷、小麦和大麦单粒电阻值。构建稻谷、小麦和大麦的单粒阻值-含水率对应关系曲线并回归出水分计算函数(稻谷R~2=0.998;小麦R~2=0.999;大麦R2=0.999)。设计多路复用比例检测电路、二阶压控有源低通滤波器和50Hz陷波等信号处理电路。采用基于ARM Cortex TM-M3核的低功耗32位微处理器硬件和软件平台完成谷物水分数据的采样、处理和计算。现场水分在线检测与烘干法对比试验表明,在循环式谷物烘干机烘干过程-5~55℃的谷物温度和10%~35%含水率范围内,单粒式在线水分测定仪的在线水分测量绝对误差≤±0.4%,一次100粒谷物测量平均时间≤55s,水分测量重复误差≤±0.3%,研究结果为实现谷物烘干过程水分在线检测提供参考。     

Bit Allocation Algorithm OFDM Systems Based for Low Voltage Network Transmitted Efficiency

Selfadaptation OFDM is suitable for the low voltage network.To satisfy the request of high speed communication in low voltage network,this paper studies a bit allocation algorithm for low voltage network OFDM systems based transmitted efficiency.And compared with the fix modulate OFDM and fix power OFDM,this algorithm can allocate the power and modulate flexibly and increase the speed.It is very appropriate for the low voltage network application.     

An Experimental Study of the Optimal Jet Position on Water Jet Assisted Drag Bit During Rock Cutting

The tests for the effects of jet position on drag bit cutting process were described. The influence of jet position on rock chips formed ahead of bit was analyzed. And the effects of cutting depth,bit velocity on bit force reductions were discussed. One of the most interesting results is that the water jet has the largest effect on drag bit forces when it is directed towards the center beneath drag bit.     

玉米杂交制种花期方案的研究

通过3年,时间对玉米杂交制种花期调节方案“母等父”与“父略早于母”进行了对比研究,结果表明,用“父略早于母”的花期调节方案比用传统的“母等父”产量有较大的提高。