小波消噪在数字基带系统中的应用

介绍了一种基于小波消噪的数字基带系统,利用小波变换的分解与重构对接收的信号进行消噪声处理,从而大大提高了系统的性能。通过在加性高斯白噪声(AGWN)信道中的模拟仿真,其结果说明了此系统的优越性,并通过卷积编码,进一步降低了系统的误码率。     

基于LabVIEW的数字信号生成在渔船通导设备测试中的应用

渔船通导设备测试台位的建设对于研究各种类型的渔船通导设备信号生成,了解频谱特性,进行针对渔船通信导航设备的误码率测试有着重要的意义。试验结果表明:该试验平台能够很好的实现数字信号仿真,满足渔船通导设备的信令信号仿真及误码率(BER)的测试需求,进而对加入不同的背景噪声环境下的信号进行模拟。     

A hypothetical,aetiological relationship between the horse's bit,nasopharyngeal asphyxia and negative pressure pulmonary oedema

Tentative explanations for the aetiology of soft palate instability and dorsal displacement at exercise are based on the proposition that it is caused by one or more, as yet unidentified, neuromuscular or inflammatory diseases. As judged by reviews, none of the treatments based on these assumptions are entirely satisfactory. Most researchers agree that their cause is unknown. In 1999, Cook proposed that they were caused by the bit breaking what should be an airtight lip seal. The present article describes a development of this hypothesis – loss of oral compartment subatmospheric pressure. The feral horse is an obligate nose‐breather and runs with a closed mouth and no air in the oral cavity and oropharynx. Evacuation of air from these compartments is proposed as the primary mechanism, strengthened by the cohesive force of surface tension, whereby the soft palate resists the elevating force of negative pressure on inspiration. It is suggested that subatmospheric pressure in the oral compartment is generated by a single swallow before running. Poll extension supplements the rigidity of the nasopharyngeal tube and reinforces the ostium intrapharyngium seal. In the domesticated horse, the lip seal is broken by a bit and bit‐induced poll flexion, jaw and tongue movement often breaks the ostium seal. Oral atmospheric pressure is proposed as the mechanism for nasopharyngeal asphyxia. It is considered that negative pressure pulmonary oedema – currently known as exercise‐induced pulmonary haemorrhage and conventionally thought to be a separate problem – is one of its clinical signs. It is suggested that the bit is the most common cause of nasopharyngeal asphyxia and that this, in turn, results in a cascade of dynamic obstructions in the larynx and cervical trachea, leading ultimately to pulmonary oedema and ‘bleeding.’ It is concluded that these are sequelae to rules in many disciplines that mandate bit usage.     

Damage by the bit to the equine interdental space and second lower premolar

Equus caballus mandibles were surveyed in 4 museum collections and 66 domestic horse mandibles were compared with 12 feral and Przewalski mandibles. Periostitis (bone spur formation) of the interdental space (bars of the mouth) was found in not less than 62% of the domestic hemimandibles. Erosion of enamel and dentine was found in 61% of the second lower premolars (Triadan 306 or 406). Eighty‐eight percent of the domestic mandibles showed one or both lesions. The more severe the interdental periostitis, the more likely it was that the 06s were eroded. Twelve feral and Przewalski mandibles were free of both lesions. A clinical examination protocol is described for the identification of bit damage in the live horse. By recommending removal of the bit when damage is found, practitioners can test the author's prediction that the bit is a cause of certain idiopathic diseases and many behavioural problems.     

The Simulation Least-Square Channel Estimation Based on OFDM System

信道估计技术保证了信号传输的可靠性。基于导频的LS信道估计算法，通过导频子信道的响应得到整个信道的响应，能够很好地跟踪信道的变化，在复杂度不高的情况下取得较好的误差性能，具有很好的实用性。仿真结果表明采用LS信道估计后有效的降低了系统的误码率。     

Population and distribution of wolf in the world

GeneraldistributionoriginaIty,wolf(CanislUPus)distributedinmostareas2o"N(Mech1974)exceptfortropicaIrainfor-estanddesert.lnatimewolfdistributedintheEurope-AsiacontinentofthenorthernsphereandtheNoFthAmericancontinentexceptforfewisIands(in-cIudingSaudiArabiaPeninsuIaandJap'n).lnNorthAmerica,thedistributionareaofwolvese\erspreadstotheSouthofMexicoadjointotheTropicofcancer(Goldman1997).ThedistributionareasofwoIveshavedecreasedgreatIysofar,especiaIlyinWestEuropeandNorthAmerica.lntheNorth…     

挖坑机钻头升土理论的研究──关于钻头临界速度的商榷

对原苏联学者C．．勃利里关于挖坑机钻头升土临界速度进行分析后，研究了钻头螺旋面上任选土壤单元体的运动与受力情况．推导出钻头升土运动的临界转速的计算公式并进行了实例计算．     

复合涂层刀具钻削Inconel 718的磨损性能研究

高温镍基合金在汽车轻量化中应用广泛,但加工过程中刀具极易磨损.针对这一问题,利用DEFORM-3D仿真软件建立不同涂层类型的麻花钻模型,对高温镍基合金Inconel718进行钻削仿真,分别研究了TiAlN涂层、Al2O3涂层、TiAlN/Al2O3复合涂层对钻头磨损的影响,并与普通硬质合金麻花钻进行了对比.研究结果表明...