稀疏水声信道的常范数盲均衡高速水下通信

为解决传统的常数模盲均衡算法在高速水下通信中收敛速度慢、稳态误差大的问题,提出了一种基于稀疏水声信道的常范数盲均衡算法.基于浅海及深海汇聚区的稀疏水声特性,将水声信道能量集中的抽头用于迭代,利用常范数的特性,消除了算法计算量及收敛性能之间的影响.通过浅海实验,对比分析了常数模算法等算法4QAM信号、16QAM信号的星座图及收敛误差曲线图.结果表明:基于稀疏水声信道的常范数盲均衡算法的收敛速度优于举数模算法及常数平方和一范数算法,稳态误差降低,提升了水声通信的收敛性能,适用于浅海和深海汇聚区水声通信.

基于小样本重用的新型混合盲均衡算法研究

随着人们对通信质量和速度的要求越来越高,传统均衡技术暴露出了越来越多的缺点。混合盲均衡算法因为其高效、适应度高的特点,成为了均衡领域的一个热点。该文提出了一种基于小样本重用的新型混合盲均衡算法。算法利用小样本重用技术重新设计均衡器加权系数,提高算法收敛效率,并引入常范数盲均衡算法,通过计算机仿真验证了了新算法有效性,可以极大的降低系统的稳态误差,提高收敛效率。

Kinetics of esterification of methanol and acetic acid with mineral homogeneous acid catalyst

In this work, esterification of acetic acid and methanol to synthesize methyl acetate in a batch stirred reactor is studied in the temperature range of 305.15–333.15 K. Sulfuric acid is used as the homogeneous catalyst with concentrations ranging from 0.0633 mol·L-1to 0.3268 mol·L-1. The feed molar ratio of acetic acid to methanol is varied from 1:1 to 1:4. The influences of temperature, catalyst concentration and reactant concentration on the reaction rate are investigated. A second order kinetic rate equation is used to correlate the experimental data. The forward and backward reaction rate constants and activation energies are determined from the Arrhenius plot.The developed kinetic model is compared with the models in literature. The developed kinetic equation is useful for the simulation of reactive distillation column for the synthesis of methyl acetate.

The Coupling Constants for.an Electroweak Model with an SU（4）PS ×SU（4）EW Unification Symmetry

We introduce the sequence of spontaneous symmetry breaking of a coupling between Pati-Salam and electroweak symmetries SU（ 4 ）PS × SU（ 4 ）EW in order to establish a mathematically consistent relation among the coupling constants at grand unification energy scale. With the values of baryon minus lepton quantum numbers of known quarks and leptons, by including right-handed neutrinos, we can lind the mixing angle relations at different energy levels up to the electromagnetic U（1）EM scale.

Kinetics of the Reaction Between Boron Trifluoride Methanol Complex and Sodium Methoxide to Produce Enriched ^(10)B Methylborate

The relation of boron trifluoride concentration with conductivity in boron trifluoride methanol solution(BF_3-CH_3OH)was power exponent fitted in low concentration range. The kinetics of the reaction between boron trifluoride methanol complex and sodium methoxide to produce enriched ^(10)B methylborate was proposed based on a detailed mechanism study, and was verified by acid-base titration method and conductivity method. It was found that this reaction is first order reaction and the rate constant is 0.022 min^(-1) at 338 K(65 ℃), the activity energy is 65 k J/mol. In addition, it was found that the conductivity method is more feasible to measure the kinetic curve than acid-base titration method.

Comparative Study of the Adsorption Thermodynamic Parameters Estimated through Different Approaches

The equilibrium constant （K0）, change in free energy （△G）, enthalpy （△H） and entropy （△S） of ammonium adsorption by a Cuban natural zeolite were estimated at the temperatures of 25, 35, 45 and 55℃ using extensively used approaches. Equilibrium data were obtained in the concentration range 50-1,200 mg·L-1 of ammonium and used in the estimation of thermodynamic parameters. Freundlich＇s isotherm model was found as with the best adjustment to equilibrium data at 25, 45 and 55℃, whereas, Redlich-Peterson＇s model had a better performance at 35 ℃. A discontinuous and unusual behavior was observed on adsorption capacity of the zeolite, with an increase from 25 ℃ to 35 ℃ followed by a decrease from 35℃ to 55 ℃. K0 values presented differences that reached up to 105 from one methodology to other. Depending on the method considered, AS results indicated both increase or decrease in system degree of disorder and △G indicated both physisorption or chemisorption process, proving the poor correlation between the estimation proceedings of such important data. The results from Gaines and Thomas method were recognized as the most correlated to calorimetric studies, as well as to equilibrium data and observations related to system entropy.

Kinetic analysis of experiment data for the formation of C.I.Acid Blue 9 leuco compound

A systematic study of the synthesis of C.I.Acid Blue 9 leuco compound in water is reported.The kinetic analysis of experimental data for the condensation reaction between 2-formylbenzenesulfonic acid sodium and N-ethyl-N-(3'-sulfonic acid benzyl) aniline obtained at four different temperatures ranging between 85 and 100°C is discussed.It is shown that the reaction followed second-order rate kinetics.The overall rate constant(k) increased with the increase of temperature.On the basis of the value of k,activation energy(E_a) of the reaction was evaluated.Importantly,it is found that reactant concentration has great effect on the formation of C.I.Acid Blue 9 leuco compound,implying that it is not enough to improve the conversion of N-ethyl-N-(3'-sulfonic acid benzyl) aniline by only prolonging reaction time in the late period of the reaction.

Influence of Temperature and Frequency on Microwave Dielectric Properties of Lunar Regolith Simulant

The dielectric constant of the lunar regolith can directly influence the reflection coefficient and the trans-mission coefficient of the Moon′s surface, and plays an important role in the Moon research. In order to study the di-electric properties of the lunar regolith, the lunar regolith simulant was made according to the making procedure of the CAS-1 simulant made by Chinese Academy of Sciences. Then the dielectric constants of the lunar regolith simulant were measured with 85070E Aiglent Microwave Network Analyzer in the frequency ranging from 0.2 GHz to 20.0 GHz and at temperature of 25.1℃, 17.7℃, 13.1℃, 11.5℃, 9.6℃, 8.0℃, 4.1℃, -0.3℃, -4.7℃, -9.5℃, -18.7℃, -27.7℃, and -32.6℃, respectively. The Odelevsky model was employed to remove the influence of water in the air on the final effective dielectric constants. The results indicate that frequency and temperature have apparent influences on the dielectric constants of the lunar regolith simulant. The real parts of the dielectric constants increase fast over the range of 0.2 GHz to 3.0 GHz, but decrease slowly over the range of 4.0 GHz to 20.0 GHz. The opposite phenomenon occurs in the imaginary parts. The influences of the frequency and temperature on the brightness temperature were also estimated based on the radiative transfer equation. The result shows that the variation of the frequency and temperature results in great changes of the microwave brightness temperature emitting from the lunar regolith.

Polarons in Bi12.47Al0.53O19.5

Electrical conductivity and dielectric properties of bismuth aluminate, Bi12.47Al0.53O19.5 （BAO）, were investigated in the frequency range from 1 Hz to 1 MHz in the temperature range from 420 K to 5 K. In the temperature range from 360 K to 220 K the real part of the complex ac electrical conductivity and dielectric constant follow the universal dielectric response （UDR）, being typical for hopping or tunneling of localized charge carriers. A detailed analysis of the temperature dependence of the UDR parameter s in terms of the theoretical model for tunneling of small polarons revealed that below 360 K this mechanism governs the charge transport in this material. The characteristic parameters for polarons, W∞, ιo, and ι0 were determined.

Hydrolysis Kinetics of 2-Pyridinecarboxamide, 3-Pyridinecarboxamide and 4-Pyridinecarboxamide in High-Temperature Water

A kinetic study is reported here on hydrolysis of three pyridinecarboxamides in high-temperature water in the temperature range of 190-250℃ at 8 MPa. 2-Pyridinecarboxamide, 3-pyridinecarboxamide and 4-pyridinecarboxamide hydrolyze to corresponding picolinic acids. 2-Picolinic acid is further decarboxylated to pyridine. Experiments at different temperatures show that the first-order rate constants display an Arrhenius behavior with activation energies of （110.9 ±2.3）, （70.4 ± 2.1） and （61.4 ± 1.8）kJ.mo1-1 for 2- pyridinecarboxamide, 3-pyridinecarboxamide and 4-pyridinecarboxamide, respectively. These kinetic parameters for pyridinecarboxamide hydrolysis are more reliable and accurate than those from the consecutive hydrolysis of cyanopyridines.

Laser-induced Fluorescence Spectroscopy of NiCl in 12900-15000 cm-1

Laser-induced fluorescence excitation spectra of jet-cooled NiC1 molecules were recorded in the energy range of 12900-15000 cm-1. Six vibronic bands with rotational structure have been observed and assigned to the [13.0]2II3/2（v＇=0-5）-X2II3/2（v＂=0） transition progression. The relevant rotational constants, significant isotopic shifts, and （equilibrium） molecular parameters have been determined. In addition, the lifetimes of the observed bands have also been measured.

Theoretical study of mechanism and kinetics for the addition of hydroxyl radical to phenol

The reaction mechanism and kinetics for the addition of hydroxyl radical （OH） to phenol have been investigated using the hybrid density functional （B3LYP） method with the 6-31＋＋G（2dp, 2dr） basis set and the complete basis set （CBS） method using APNO basis sets, respectively. The equilibrium geometries, energies, and thermodynamics properties of all the stationary points along the addition reaction pathway are calculated. The rate constants and the branching ratios of each channel are evaluated using classical transition state theory （TST） in the temperature range of 210 to 360 K, to simulate temperatures in all parts of the troposphere. The ortho addition pathway is dominant and accounts for 99.8%-96.7% of the overall adduct products from 210 to 360 K. The calculated rate constants are in good agreement with existing experimental values. The addition reaction is irreversible.

Negative refraction with absorption suppressed by electromagnetically induced transparency in a left-handed atomic system

This paper intends to realize negative refraction with absorption suppressed by the electromagnetically induced transparency (EIT) in a dense four-level atomic system.Without the two equal transition frequencies responding to the probe field,the atomic system displays a negative refraction with the simultaneously negative permittivity and negative permeability (left-handedness).The response of the probe field is amplified and propagates transparency in some frequency extents.Therefore,our aim for searching the low-loss negative refraction can be achieved in the scheme,given the main applied limitation of the negative refractive materials is the large amount of dissipation and absorption.However,an excessive signal field intensity would increase the absorption near the resonance in our scheme.

Analysis of influence factors of negative refraction phenomenon in particulate composite

The effective optical constants that describe the interaction between electromagnetic wave and particulate composite are calculated based on effective medium theory and Mie theory.The negative refractive phenomenon is compared between the Ge-particle-dispersed LiTaO 3 composites and Ag-particle-dispersed LiTaO 3 composites.It is indicated that the negative refraction phenomenon for semiconductor Ge particulate composite occurs in higher frequency range than that of noble Ag particulate composite.By take the Ge particulate composite as an example,the influence of size and number density of spherical particles on the negative refraction phenomenon is analyzed.It is indicated that the frequency range where negative refraction phenomenon occurs can be shifted to higher frequency by adjusting these two influencing factors.