说话人辨认中有效参数的研究

说话人辨认技术是语音识别中的一项重要应用，在我们研究的系统中，LPC参数并不是都很有效，我们用统计分析方法对12个预测系数、12个部分相关系数、12个对数面积比系数、12个倒谱系数、12个相关系数、短时能量、短时平均过零率及基音共63个参数，进行方差比检验，用10名男青年的三个元音的发音，在半年内采集97种语音作为试验材料，选出15个方差比比较大的作为识别参数，识别率为89.19%，采用样本刷新技术后，识别率达到97.3%。     

单延迟三阶,四阶相关函数确定超短光脉冲形状

本文提出用单延迟三阶、四阶相关函数,经傅里叶交换获得脉冲形状的方法.在实验上用克尔快门测量了YAG被动锁模激光脉冲的三阶和四阶相关函数,并用该方法获得脉冲形状.文中还讨论了脉冲对称性对恢复脉冲的影响.     

对于2002年高考数学第21题的一点思考

原题　 ( )给出两块面积相同的正三角形纸片 ,要求用其中一块剪拼成一个正三棱锥模型 ,另一块拼成一个正三棱柱模型 ,使它们的全面积都与原三角形的面积相等 ,请设计一种剪拼方法 ,分别用虚线标示在图中并作简要说明 .( )试比较你剪拼的正三棱锥与正三棱柱的体积的大小 .( ) (略 )标准答案是一种解法 ,摘要如下 :解　 ( )剪法如图 1、图 2所示图 1　　　　　　图 2( )设给出正三角形的边长为 2 ,则V锥 - V柱 =( 13h锥 - h柱 ) . 34=( 69- 36 ) . 34<0 .所以 V柱 >V锥 .这道题另一种迥然不同的剪法 (如图 3) ,先把正三角形拼成一个长…     

被动调Q自拉曼Nd∶GdVO4激光器

对激光二极管(LD)抽运的自拉曼Nd∶GdVO4被动调Q激光器进行了详细的理论和实验研究。实验中采用Nd∶GdVO4晶体同时作为激光介质和拉曼晶体,分别用了两块不同初始透射率的Cr4 ∶YAG晶体,得到并比较了采用不同初始透射率的Cr4 ∶YAG晶体时被动调Q自拉曼激光器的性能。测量了平均输出功率、脉冲宽度和脉冲重复率随抽运功率的变化关系。当Cr4 ∶YAG的初始透射率为0.91,输入功率是5.7 W时,得到的拉曼光的最高功率为244.6 mW,相应的转换效率为4.3%。通过数值求解基频光和拉曼光空间分布的速率方程并应用到被动调Q自拉曼Nd∶GdVO4激光器。获得的理论结果与实验结果大致相符。     

A compact electro-absorption modulator based on graphene photonic crystal fiber

A compact electro-absorption modulator based on graphene photonic crystal fiber is proposed. To enhance the graphene–light interaction efficiency, the innermost six air-holes of photonic crystal fiber are replaced by two large semicircular holes, and monolayer graphene is deposited on the two large semicircular holes. By optimizing the structure parameters, a strong graphene–light interaction is obtained. Moreover, the switch on–off point of the modulator is unchangeable,which is only related to the frequency of the incident light. The influence factors of this composite structure have been analyzed. The proposed modulator is compared with other graphene-based modulators, and the results show that it is filled without dielectric spacer. There are some excellent performances, such as an extinction ratio 7 dB of y-polarization mode,3-dB modulation bandwidth of 70 GHz with small footprint of 205 μm, and a consumption of energy per bit 59 pJ/bit.     

915 nm单频Nd∶YAG晶体衍生光纤激光器

报道了一种基于Nd∶YAG晶体衍生光纤(NYDF)的915 nm单频光纤激光器.使用掺杂原子数分数为2.5％的Nd∶ YAG晶体作为纤芯材料,高纯度石英管作为包层材料,利用熔芯法制备Nd∶ YAG晶体衍生光纤,其传输损耗为8 dB/m,在915 nm处其增益系数为1.16 dB/cm.基于Nd∶YAG晶体衍生光纤,实现...     

Dislocation formation and twinning from the crack tip in Ni3Al: molecular dynamics simulations

The mechanism of low-temperature deformation in a fracture process of L12 Ni3Al is studied by molecular dynamic simulations.Owing to the unstable stacking energy,the [01ˉ1] superdislocation is dissociated into partial dislocations separated by a stacking fault.The simulation results show that when the crack speed is larger than a critical speed,the Shockley partial dislocations will break forth from both the crack tip and the vicinity of the crack tip;subsequently the super intrinsic stacking faults are formed in adjacent {111} planes,meanwhile the super extrinsic stacking faults and twinning also occur.Our simulation results suggest that at low temperatures the ductile fracture in L12 Ni3Al is accompanied by twinning,which is produced by super-intrinsic stacking faults formed in adjacent {111} planes.     

非晶态RE—TM(RE=Nd,Pr,TM=Fe,Co,Ni)薄膜的磁性和Pr的变价行为

本文通过对非晶态轻稀土Pr,Nd和过渡族金属Fe,Co,Ni薄膜合金的低温磁性研究,分别得到了(Pr,Nd)_x-(Fe,Co,Ni)_1-x合金中Pr,Nd和Fe,Co,Ni金属磁矩随成份x的变化,并且通过对磁矩的研究得到Pr离子的4f电子可能有退局域化的结论。 关键词：     

Tl系1223相超导体的不可逆线

研究了(Tl_(0.5)Pb_(0.5))(Sr_(0.8)Ba_(0.2))_2Ca_2Cu_3O_y超导体的不可逆场H~*(T),并与Y系、Bi系和Tl1212相超导体作了比较。实验表明,在77K下Tl 1223相的不可逆场高达5T。证明了该材料在高温下的磁通钉扎比Bi系超导体和Tl 1212相超导体强得多,并对此作了讨论,由磁滞回线估计的磁化电流密度J_c在77K和2T磁场下大于10~4A/cm~2。