变质量力学问题动力学方程的简明讲法

本文对变质量力学方程提出简单引入法,给出利于记忆的方程形式,并对文献[1]和[2]所提问题重新求解,指出其不足。     

声学悬浮泥沙浓度估计

讨论了声学悬浮泥沙浓度估计方法,获得了两种泥沙浓度估计的方法.第1种是曲线拟合法,根据声反向散射原理,提出声学方法得到的浓度M(r)和6点法得到的浓度M₀(r)间的拟合因子K₁(r)是距离r的高次幂函数,采用最小二乘法,使M(r)与M₀(r)在整个水深上的差值最小,确定出高次幂曲线中的待定系数.方法对水中悬浮物引起的声吸收系数未加任何限制.第2种方法是递推拟合法,采用6点法的M₀(r)作为初始条件和判定条件,对递推过程加了合理的约束条件,递推过程稳定.大量试验数据分析表明,第1种方法的误差小于第2种方法,但是第2种方法不但可得到泥沙浓度估计,还可得到声波的吸收系数.两种方法均已取得良好的应用成果.     

Acoustic estimation of suspended sediment concentration

In this paper, the acoustic estimation of suspended sediment concentration is discussed and two estimation methods of suspended sediment concentration are presented. The first method is curve fitting method, in which, according to the acoustic backscattering theory we assume that the fitting factor K₁ (r) between the concentration M(r) obtained by acoustic observation and the concentration M₀ ( r) obtained by sampling water is a high order power function of distancer. Using least-square algorithm, we can determine the coefficients of the high order power function by minimizing the difference betweenM( r) and M₀ ( r) in the whole water profile. To the absorption coefficient of sound due to the suspension in water we do not give constraint in the first method. The second method is recursive fitting method, in which we take M₀ ( r) as the conditions of initialization and decision and give rational constraints to some parameters. The recursive process is stable. We analyzed the two methods with a lot of experimental data. The analytical results show that the estimate error of the first method is less than that of the second method and the latter can not only estimate the concentration of suspended sediment but also give the absorption coefficient of sound. Good results have been obtained with the two methods.     

茶与化学

饮茶在我国有数千年历史 ,且经久不衰 ,现在几乎普及至世界所有国家和地区 ,这是基于茶叶中含有 6 0 0多种化学成分 ,其中大多数成分对人体有营养保健作用以及对许多疾病有预防和治疗功效。     

水声高速图像传输信号处理方法

研究了水声图像高速传输信号处理方法,它包括两个方面,一方面是水声相干通信信号处理方法,其中:(1)多普勒频移补偿,在数据包的前后两端插入已知线性调频(Chirp)信号,拷贝相关后求互相关,估计相对多普勒平均频移。在自适应判决反馈均衡器中加上自适应相位补偿器,采用快速自优化最小均方(LMS)算法,与其对应的速度容限优于常用的二阶锁相环相位补偿器的。两种补偿方法联合工作时,性能优良。(2)带有分集合并器的自适应判决反馈均衡器的算法是快速自优化的LMS算法,计算量小,性能优良。(3)自适应判决反馈均衡器与Turbo-网格编码调制(TCM)译码器级连、迭代算法。研究了基于软输出维特比(SOVA)方法的新型的比特-符号转换器,用它时误比特率(BER)比常规编码、映射方法的近似小2个数量级。另一方面是抗误码的图像压缩方法。本文基于数字小波变换和定长编码方法,研究了声图像的压缩。它包括:(1)选用CDF9/7小波进行小波变换。(2)对小波系数子带能量进行统计分析,三层小波分解是合适的。(3)对不同能量的子带采用不同的量化步长。(4)采用定长编码算法。结果表明声图像压缩比特率为0.85。当BER小于10~(-3)时,图像质量完好。当BER小于10~(-2)时,图像中出现少量小黑白点。在上述基础上研制了水声通信机,频带为(7.5～12.5)kHz,接收声呐阵为8基元等距线阵,信号为QPSK和8PSK。在中国千岛湖进行了湖试,采用SOVA硬迭代算法,达到了低BER。传输一幅256×256×8的声图需时约7s。传输距离与传输速率之积为55 km kbps。     

辣根过氧化物酶在分析化学中的应用

辣根过氧化物酶是一种重要的分析化学试剂,对过氧化氢底物特异性强。广泛用于临床化学、环境化学和食品工业等领域。本文评述了近十年来辣根过氧化物酶在分析化学中的应用进展。包括光度法、荧光法、化学发光法、电化学传感器和光导纤维传感器法测定过氛氢及相关物质,及辣根过氧化物酶在其他无机、有机及生物物质分析中的应用。引用参考文献６０篇。     

Extraction of characteristic roots on Bessel-Neumann's mixed equations

This paper discusses the problem of the extraction of characteristic roots {λ_t}(λ₀<λ₁<λ₂…) on Bessel-Neumann’s mixed equations. It gives the expressions and the evaluation of the minimum root. The advantage of the method has no use for the table of the multi-figure number Bessel function and it does not need computer but can calculate all the characteristic roots {λ_t}. The precision of these roots is still high.     

Linear theory of beam–wave interaction in double-slot coupled cavity travelling wave tube

A three-dimensional model of the double-slot coupled cavity slow-wave structure(CCSWS) with a solid round electron beam for the beam–wave interaction is presented. Based on the "cold" dispersion, the "hot" dispersion equation is derived with the Maxwell equations by using the variable separation method and the field-matching method. Through numerical calculations, the effects of the electron beam parameters and the staggered angle between adjacent walls on the linear gain are analyzed.     

肌骨超声对类风湿关节炎疾病分期的评估价值及血清SOD、PCSK9表达的关联性

本研究探讨肌骨超声对类风湿关节炎疾病分期的评估价值及类风湿关节炎与血清超氧化物歧化酶(SOD)、前蛋白转化酶枯草溶菌素9(PCSK9)表达的关系.选取类风湿关节炎患者140例作为观察组,同时选取体检健康者100例作为对照组,检测两组血清SOD、PCSK9的表达水平,给予肌骨超声检查.结果 显示:观察组血清SOD的表达水...     

可见光促进的苯及衍生物去芳构化反应

总结了近年来可见光促进苯及其衍生物去芳构化反应的研究进展,主要分为基态与激发态化学两方面,并对该领域的发展前景进行了展望.