An optimal equivalent subchannel algorithm for low voltage power line communication system

According to the low voltage power line channel features,combined with adaptive bit loading and power allocation algorithm,an optimal equivalent subchannel algorithm is proposed.Under the condition of fixed amount of transmitted bits and the minimum transmitted power model,impact of optimal equivalent subchannel on the system performance is studied.The optimization algorithm sorts subchannels with similar transmission features into groups,thus the signaling load can be reduced,and the spectrum can be better used.The simulation results show that system can get lower bit error rate(BER) by adopting optimal equivalent subchannel algorithm.     

不同疏花留果方式对红梨果实品质的影响

[目的]研究红梨（92-2）果实生产过程中的最佳疏花留果的方法。[方法]以红梨（95-2）为试材,采用不同果实序位的留果方式以及不同疏花疏果的方法,在开花期、结果期以及果实成熟期开展相关研究。[结果]一花枝上2、3和4号果位的平均单果重、果面果锈面积与对照间均存在0.01水平显著差异,且器官发育完善、授精结实后不易形成生理落果,果型较正;同时,一花枝上同时保留2、3和4号果位的花朵,每朵花序保留2个果,平均单果重、平均果实纵径以及平均果实横径分别超出未疏花蔬果的处理127.34g、25.59mm和35.77mm。[结论]在实际生产过程中,对梨树进行合理的果位留果具有重要意义。     

一种岩石可钻性评价新模型

目前确定地层岩石可钻性的方法主要是基于室内微钻头实验测算岩心抗钻能力,这种方法需要大量的岩心,费用高,周期长,且常常滞后于实际钻进。通过分析实钻参数与钻头破岩的体积功密度之间的关系,从能量耗散的角度建立了应用岩石破碎比功评价岩石可钻性的模型,通过现场实际应用证明该模型能动态的反映实钻条件下的岩石可钻性,有利于实现随钻随测,弥补了传统可钻性评价方法的不足,为优快钻井技术中实时钻头优选和钻井设计提供了理论依据。     

Effect of the helix angle of router bits on chip formation and energy consumption during milling of solid wood

The effect of the helix angle of a router bit on chip formation and electric energy per volume (specific energy) under different feed speeds and cutting depths during the milling of maple and China fir by a computer numerically controlled (CNC) router was investigated. The peripheral cutting edge of router bits were custom-made at helix angles of 0°, 2°, 4°, 6°, and 8°. The feed speed varied from 600 to 4800mm/min, and the depths of cut were set at 1,2,3,4, and 6mm. The chips were classified by sieving into a flake type, a splinter type (5 and 10 mesh), a flow type (20 and 40 mesh), and a granule type (< 40 mesh). As the feed speed and the cutting depth increased for the five router bits, more chips of the flake type and the splinter type were produced. However, the number of granule-type chips under the larger helix angle was reduced. The energy per volume removed (specific energy) increased with the feed speed and the depth of cut while milling maple and China fir. More specific energy per cubic centimeter was consumed under the lower feed speeds and the smaller depth of cut. The specific energy can be expressed as a negative power function of the feed speed or the cutting depth for maple and China fir.     

RAPD标记在松口蘑菌丝体鉴定中的应用

利用筛选的分离培养基从4个长白山松口蘑菌褶中各自分离了菌丝体,应用RAPD标记对其真伪进行了鉴定.结果表明：分离的菌丝体是其来源松口蘑子实体的纯培养物;所选培养基可用于松口蘑菌丝体的分离;长白山松口蘑子实体之间遗传差异较大.     

Application of a Dual Force Sensor System to Characterize the Intrinsic Operation of Horse Bridles and Bits

An equine bridle tension system, with electronic force gauges in both the line of the reins and that of the cheekpiece (CP) on one side of the horse, is used to study the dynamic response of the CP tension to rein tension in the ridden horse. The objective is to quantify so-called “poll pressure.” Bits designed to give strong poll pressure using simple pulley or lever principles show a much attenuated transfer of the rein tension through the bit to the poll. The attenuation is readily understood when the equine mouth is recognized as a “floating” fulcrum degrading the otherwise required fixed pivot point of an ideal lever. Furthermore, any use of a curb chain diverts higher rein-induced CP tension to the chin rather than to the poll. Unexpectedly, however, a simple loose ring bit is found to give modest poll pressure, transferring rein tension through a pulley-like action. Finally, the curb bit of a double bridle is examined, and physical interference between the curb and bridoon mouthpieces is found. Standard, yet powerful computational signal processing of the dynamic time series tension data reveals that the poll pressure produced by the curb bit is predominantly due to tension in the bridoon reins and not the curb reins. Physical overlaying of the bridoon on the curb mouthpiece is implicated.     

新型整体硬质合金三刃麻花钻切削性能的试验研究

本文简要介绍了新型整体硬质合金三刃麻花钻的结构特点,对这种新型钻头的切削性能、加工效率、钻削力、孔的加工精度和表面粗糙度、断屑性能等进行了试验,并与普通高速钢麻花钻进行了对比,试验结果表明,新型整体硬质合金三刃麻花钻的切削性能明显优于普通高速钢麻花钻,是一种性能优良的新的硬质合金钻型.     

新型高速钢强力切削麻花钻切削性能的试验研究

In this paper, the structural properties of new HSS heavy cut twist drills are simply explained. Several experiments have been done to investigate the axial thrust force,the cutting moment of torque,the machining efficiency, the precision and the surface     

石质山地手提式挖坑机钻头的研制

本文通过对研制的几种手提式挖坑机钻头的结构特点、参数选择、刀片及钻尖的型式、材料及热处理工艺等所进行的理论分析及生产试验,证明了所研制的钻头在含石砾量40％～60％的陡坡石质山地的挖坑整地作业中,具有良好的适应性,钻头入土快、生产效率高、成本低、劳动强度低、各项指标达到林业技术要求。     

基于误码检测机制的滴灌系统红外光雨水传感器的设计

降雨使作物生长土壤中的水分含量增加而营养成分含量降低,智能化滴灌系统必须感知降雨的开始和结束,并对灌溉系统中的水分与营养成分进行相应调整与控制,既节水节能又保持作物良好生长环境。雨水水流对红外发射器和接收器间光通信产生散射干扰,并造成误码。该文设计一种基于误码检测机制的红外光雨水传感器,它由集雨器、导流管、红外光发射器和接收器组成,微控制器检测通信误码感知降雨,解决了传统雨水传感器在滴灌系统应用中只能监测降雨的开始而不能监测降雨结束的弊端。该文提出降雨时通信误码率最大,无降雨时通信误码率最小的数据码选择方法,该方法表明,数据码"1"码数目对通信误码率影响显著。试验结果表明,检测降雨最优码是255。该传感器对连续水流检测的误码率大于0.9983,对离散水滴检测的误比特率是0.7742至0.8307,该传感器对雨水的感知性能优于传统雨水传感器。