一种新的变步长LMS算法在通信对消技术的应用

本文通过分析几种变步长LMS算法,结合VSS-NLMS算发和NLMS算法的优点,采用符号函数降低原有算法的计算复杂度,对变步长参数进行调整,提出了一种改进的变步长LMS算法,通过仿真验证,新提出的算法在收敛速度和稳态误差上也有一定优点,具有工程实际意义。     

Effect of sodium selenite on the activity of antioxidant enzymes (superoxide dismutase, glutathione peroxidase) during hepatocarcinogenesis

Influence of sodium selenite on functioning of the systems of intracellular generation and detoxication of active oxygen compounds in hepatocarcinogenesis induced by diethylnitrosamine has been studied in experiments on rats. It has been shown that the duration of latent period initiated by ions of Fe2+ chemiluminescence of homogenate of the liver rather objectively reflects the state of the functioning of the systems in charge of the formation and utilization of free radicals of oxygen in a cell. It is supposed that one of the mechanisms of anticarcinogenic action of selenium is connected with its antioxidant functions in the organism and consists in the increase of the activity of superoxide dismutation and selenium-dependent glutathione peroxidases, providing a reliable level of enzymatic protection of normal cells from disturbing action of "active oxygen".     

Statistical characteristics of chaoticity and incomplete chaoticity of irregular oscillations generated by a strongly nonlinear autonomous system with two degrees of freedom

The notion of the interval of nonergodicity as one of the statistical characteristics for time realizations of an irregular process is introduced. A method for determination of this factor based from the analysis of autocorrelation functions of truncated realizations is developed. The chaoticity of irregular oscillations in a strongly nonlinear autonomous system with two degrees of freedom is proved using the criterion of decomposition of time correlations. The statistical indication of the existence of incomplete chaoticity of oscillations in the case of incomplete decomposition of correlations is formulated. Conditions of weak distortions of the energy spectrum for truncated realizations are determined. Probability distribution functions for the characteristics of an irregular time process in the studied system are considered.     

Modeling of wideband slow-wave structures of coupled-cavities-chain type by the impedance design of experiments

The results of investigation on the possibility of a substantial extension of the operating-frequency band of a slow-wave structure of coupled-cavities-chain type are presented for the case of a small variation in the slowing factor of the phase velocity of a wave, including, in the case of convergence of the cavity and slot passbands. The investigation is performed with the use of regression models for electrodynamic characteristics of the slowing structure that are constructed on the basis of the results obtained by the impedance design of experiments. Variants of wideband chains of coupled cavities with differences in the phase-velocity slowing factor of ±3% and the operating width of the cavity passband of up to 35%, as well as structures with merging of the cavity and slot passbands and a resulting passband of up to 70% and a coupling impedance of 18–0.4 Ω, are obtained.     

基于物联网的图书馆管理系统

针对物联网的基本概念、起源、发展以及物联网关键技术,针对图书馆借书流程、图书快速定位、图书安全等问题与RFID技术的应用进行设计。通过介绍智能图书馆对于物联网技术的应用,提出智能图书馆的智能化和便捷化,同时也提出了发展物联网的重要意义,通过对只能图书馆的设计,让人们真切感受到物联网对人们生活的提升。     

Radiation from a Plasma Layer with a Strong Longitudinal Irregularity

The efficiency of conversion of the energy of a surface wave into radiation at longitudinal irregularities of a planar plasma layer is studied. The analysis is performed by the spectral expansion of the field in a complete set of surface and pseudosurface waves. The system of integro-differential equations for the coefficients of expansion that determine the amplitudes of the transmitted, reflected, and scattered waves as well as the radiation pattern is solved in the case of a rapid change in the plasma density. The coefficients of transformation of energy into the energy of radiation as functions of the gradient of the plasma density for different values of the electrical length of the region of plasma irregularity and the electric thickness of the plasma layer are found. Examples are demonstrated when the fraction of the energy of the surface wave transformed into radiation reaches 60–70%. Radiation patterns that proved to be highly directional and having one lobe with the maximum at an angle of a few degrees to the direction of propagation of the surface wave are calculated.     

左手材料的色散和等倾干涉

研究了左手材料棱镜的色散特性和左手材料平行平板的等倾干涉特性。对于左手材料棱镜而言,其色散时出射光偏离原来的传播方向与右手材料棱镜的色散规律恰好相反,且对于同一种单色光而言,当入射角相同时,左手材料棱镜的色散偏向角大于右手材料棱镜的色散偏向角。在研究左手材料平行平板的等倾干涉特性时,推导了反射光和透射光焦平面上的光强分布公式,分析了等倾干涉条纹的级数与亮、暗条纹的关系,讨论了光程差的影响因素及影响规律,推导了存在半波损失情况下的等倾圆环的亮环半径公式和暗环宽度公式。研究发现:对于左手材料平行平板的等倾干涉条纹而言,等倾干涉圆环中心处的干涉级数较小;偏离圆环中心越远,干涉条纹的级数越大。这一规律和右手材料平行平板的等倾干涉条纹规律不同。     

Simulation of the absorption of a femtosecond laser pulse in crystalline silicon

The effect of the nonlinearity of the absorptivity and absorption coefficient on the process of the intense photoexcitation of silicon is studied on the basis of a model of the two-photon excitation of a semiconductor with consideration for external emission. Correlation between the results of simulation of the absorption of a femtosecond laser pulse in single-crystal silicon and experimental data under conditions of the femtosecond excitation of surface plasmon polaritons makes it possible to refine the mechanism of changes in the absorptivity and to make an inference regarding the necessity of considering these changes when assessing the conditions of the laser treatment of semiconductors. Avenues for further improvement of the theoretical model are discussed.     

Elimination of cyclic phase slips of single-frequency kinematic GNSS observations

The results of development of a new method for the estimation and elimination of cyclic phase slips of single-frequency kinematic GNSS observations have been presented. The investigations and verification of the proposed method were performed using simulations and real GPS observations. Conditions of the continuity restoration of phase observations were determined; the specified conditions ensure a reliable elimination of cyclic phase slips under conditions of the partial and total loss of observations on intervals of up to 30 s. The possibilities of enhancing the reliability of elimination of phase slips were investigated using a group of increments of observations obtained under the free running and differential modes of coordinate determinations. It was shown that the reliability of solving the problem in question was critically dependent on the use of smoothed code observations. The smoothing of code observations makes it possible to achieve a much larger effect as compared with an attempt of increasing the number of satellites in the current constellation.     

Prospects of a slotline utilization as the excitation element of a quasi-optical hemispherical resonator for the problems of liquids dielectrometry

Inthis article we propose the utilization of a quasi-optical resonator in the form of the resonant cavity of hemispherical shape in the metal as a measurement cell of a dielectrometer for the investigation of electrophysical properties of liquids. We have carried out the investigations of electromagnetic characteristics of the utilized resonator in the case of the air filling and of the partial filling by the analyzed liquids (benzene, butanol, ethanol, methanol). The possibility of effective excitation of whispering gallery modes using the slot line has been demonstrated. We have determined the possibilities of the utilized investigation technique of the electrophysical properties of different liquids and of their identification based on the variations of electromagnetic characteristics of the proposed measurement cell. It has been shown that in the case of a small perturbation of the resonance fields by samples of liquids (with volume up to 3 ml) this technique for the proposed resonator possesses a high sensitivity and resolution capability for the identification of liquids with a relatively small difference of the electrophysical parameters.     

米酵菌酸对小鼠肝和心肌细胞毒性作用的超微结构研究

目的：观察米酵菌酸对小鼠肝、心肌细胞毒性作用的超微结构改变，探讨米酵菌酸中毒的机理，方法：小鼠腹腔注射不同剂量的米酵菌酸，2h后取其肝和心肌组织，通过电镜观察其细胞超微结构的改变，结果：电镜下可见肝细胞和心肌细胞的线粒肿胀，内嵴断裂，模糊或消失，基质局部或全部空亮，呈囊泡样变，偶见其中含髓样小体，上述线粒体内嵴和膜结构的病变随米酵菌酸剂量的增加而加重，结论：米酵菌酸对小鼠肝、心肌细胞毒性作用以线粒体的损伤较为突出，因此我们认为，线粒体内膜的破坏造成线粒体的功能障碍，影响细胞呼吸，使细胞缺氧导致小鼠中毒死亡。     

The cyclotron resonance of holes in InGaAs/GaAs heterostructures with quantum wells in quantizing magnetic fields

The spectra of the cyclotron resonance of holes in the InGaAs/GaAs selectively doped heterostructures with quantum wells are studied in pulsed magnetic fields as high as 50 T at 4.2 K. The previously observed effect of the inverted (compared with the results of the single-particle calculation of the Landau levels) ratio of the spectral weight of two split components of the line of the cyclotron resonance, which is attributed to the effects of the exchange interaction of holes, is confirmed. It is found that the ratios of intensities of the components of the line of the cyclotron resonance profoundly differ on the ascending and descending branches of the magnetic field pulse, which may be associated with a long time of the spin relaxation of holes between the two lowest Landau levels, which constitute tens of milliseconds.     

激光选区熔化纯铜成形件尺寸精度的研究

为了研究工艺参量对激光选区熔化纯铜粉末成形件尺寸精度的影响,采用正交实验对纯铜粉末进行了激光选区熔化成形研究。分析了铺粉厚度为0.05mm时,工艺参量对成形件尺寸绝对误差的影响规律及各因素对尺寸精度的影响机理,确定了各工艺参量对尺寸绝对误差影响的主次顺序为扫描间距>扫描速率>激光功率>扫描路径,得到最优的工艺参量组合为激光功率360W,扫描速率1050mm/s,扫描间距0.08mm,扫描方式是spiral。结果表明,成形件尺寸绝对误差随激光功率的增大而增大,随扫描速率、扫描间距的增大而减小;不同扫描路径对尺寸绝对误差的影响差别较小;在因素水平范围内,尺寸绝对误差随体能量密度的增加而增大。该研究为激光烧结纯铜粉末时的参量选择提供了一定依据。     

Distortions of the ultrawideband signals of deep-sensing radars in an irregular ionosphere

Propagation of the ultrawideband signals of deep-sensing radars in the ionosphere is studied in the presence of small-scale random fluctuations of the plasma density. Simulation of the signal distortions caused by the joint influence of phase distortions in a regular layered dispersive medium and scattering of radio waves by the small-scale random irregularities of the ionospheric plasma is performed. The influence of scattering by the small-scale irregularities on operation of the algorithms for correction of the phase distortions of signals in a regular ionosphere is investigated. Stability of operation of the studied correction algorithms under the conditions of signal scattering by the irregularities of the ionospheric plasma is demonstrated.     

A vector model of wave propagation through an interface of dissipative media

The possibility of solution of the problem of wave propagation through an interface of two dissipative media with the help of a trigonometric vector model is shown. Two invariants independent of the dissipation of these media are revealed: (i) the sum of projections of vectors of reflected and transmitted waves onto the polar axis, which is equal to the projection of the vector of the incident wave onto the same axis, and (ii) the sum of projections of vectors of these waves onto the normal to the polar axis, which is equal to zero.     

Increase of accuracy of definition of coordinates by multi-position passive complexes on a basis of difference-distance measuring method and the problem solution in redundancy conditions

It is proposed a method of definition of coordinates of radiation sources (RS) using difference-distance measuring method and the problem solution in condition of redundant information about target space location. It is considered mathematical tool for the problem solution in condition of redundancy, it is represented a validation of considered method of RS coordinates definition. It is carried out simulation of RS coordinates definition, and on a basis of statistic characteristics of simulation results it is shown increase of the accuracy of RS coordinates in case of application of given method in the system of passive radio location.     

Evolution of a Magnetoresonance Line Near to a Limit of Percolation in Dilute Magnetics

In paper the results of numerical modeling of a magnetic resonance in dilute magnetics near to a threshold of a percolation are discussed. The classical equation of motion of magnetic moments is used in view of an exchange interaction such as RKKI and imitation of spin-phonon interaction by Monte-Carlo method. It is shown, that cluster structure of a magnetic and threshold of percolation are determined by critical distance, on which there is a change of a sign of an exchange interaction. In an examination of percolation phase transition the jump change of breadth of a line of a magnetic resonance is set, that can form the basis for experimental definition of a threshold percolation and parameters of an exchange interaction by methods of a radiospectroscopy.     

Estimation of the Initial Phase of Narrowband Radio Signal with Unknown Amplitude and Duration

The quasi-likelihood and maximum likelihood algorithms for estimating the initial phase of radio signal with arbitrary shaped envelope and unknown duration and amplitude have been synthesized. Schematic block diagrams of initial phase meters are proposed. Characteristics of the synthesized algorithms were determined, and errors of the initial phase estimates were compared. The structure of quasi-likelihood estimate of the initial phase is shown to be invariant with respect to the lack of knowledge of radio signal amplitude. However, a mismatch between the expected value of signal duration and its true value can lead to a marked increase of dispersion of the initial phase quasi-likelihood estimate. The loss in accuracy of the initial phase estimate due to a priori lack of knowledge of signal duration has been determined. Analytical expressions for statistical characteristics of maximum likelihood estimate of initial phase at large signal-to-noise ratios are shown to coincide asymptotically with the characteristics of maximum likelihood estimate of the initial phase of radio signal with a priori known amplitude and duration. Therefore, a priori unknown signal duration (asymptotically with an increase of signal-to-noise ratio) does not affect the accuracy of the maximum likelihood estimate of initial phase. The computer methods of statistical simulation were used to determine the applicability limits of asymptotic expressions for characteristics of the maximum likelihood estimate in respect of signals with linear and exponential envelopes.     

Emission spectra of InGaN/AlGaN/GaN quantum well heterostructures: Model of the two-dimensional joint density of states

The luminescence spectra of light emitting diodes based on InGaN/AlGaN/GaN heterostructures with multiple quantum wells are analyzed in the context of a model of the two-dimensional density of states in the active region. The model accounts for the potential fluctuations, the statistics of occupation of the wells with charge carriers, and specific features of the extraction of radiation from the structure. The model describes the position of the maxima of the spectra and the exponential decline of the emission intensity in the short-and long-wavelength regions as well as the modification of the spectra under variations in the current. The problems of limitations of the model and the physical meaning of the parameters are discussed. The examples of approximation of the spectra of blue light emitting diodes based on InGaN/AlGaN/GaN heterostructures show the necessity of determining the temperature in the active region independently and taking into account the interference in the planar structure. The differences of the shape of the spectra from that obtained in the simple model depend not only on the properties of the quantum wells but also on the nonuniformities in the distribution of In in InGaN.     

A millimeter-band planar lens based on an inhomogeneous medium with forced refraction

A millimeter-band planar lens designed on the basis of an inhomogeneous medium with forced refraction, which is formed by a periodic grating of metal strips placed on the surfaces of a dielectric plate, is considered. The possibility of application of this lens as the basis for the design of a multibeam receiving antenna for a radio imaging system is analyzed. The structure of an antenna consisting of a planar lens and a multichannel feed is proposed. The results of the design of a planar lens based on an inhomogeneous medium with forced refraction are presented. A multichannel feed in the form of an array of E-plane horns is analyzed and the results of simulation of this feed with the help of an approximate technique and numerical solution of an electromagnetic problem are given. The design of the multibeam antenna and its experimental characteristics are presented. The possibility of computer correction of radiation patterns of the multibeam antenna is considered.