适用于任意频隙数的跳频序列族产生方法研究

在现有跳频序列产生理论的基础上,从工程实现的角度研究了一种跳频序列族的构造方法。该方法利用GF(p)上的反馈移位寄存器和若干非线性逻辑运算,产生出性能较好、可用频隙数为p^k-p^m的跳频序列,并通过有限域的多项式长除法实现了系统时间TOD与跳频状态的对应,使其具有实用性。通过对各项性能进行分析仿真,证明生成的跳频序列具有分布均匀、独立性好及线性复杂度大的特点,并易于工程实现。

基于串扰感知技术的光网络频谱动态分配研究

以提升光网络通信质量为目的,研究基于串扰感知及时的光网络频谱动态分配方法,提升频谱动态分配效果。通过计算光网络串扰值,建立以最小芯间串扰为目标函数,芯间串扰产生条件约束,以及芯间串扰阈值约束等为约束条件的光网络频谱动态分配模型;在量子遗传算法内,引入混沌优化算法,得到改进量子遗传算法,避免算法陷入局部最优解;利用改进量子遗传算法,求解频谱动态分配模型,得到最小芯间串扰的光网络频谱动态分配方案。实验证明:不同光网络类型下,该方法均可有效完成光网络频谱动态分配,降低光网络的芯间串扰值,在不同网络负载时,本方法的光网络带宽阻塞率低0.17,频谱利用率超过了0.13。

多芯光纤中的自适应阈值和频谱优先算法

为了有效解决纤芯中的串扰问题并降低网络阻塞率,提出了一种自适应阈值和频谱优先(AT-SF)算法,采用纤芯分组的方式使每组中的纤芯不相邻,将典型的7芯光纤分成3组,第三组纤芯的优先级在业务到达过程中是可变的;同时,AT-SF算法引入了频隙(FS)阈值参数,将大于FS阈值的业务分配在第一、第二或者第三组纤芯上,小于等于FS阈值的业务只分配在第三组纤芯上。分别在NSFNET、USNET网络中进行了仿真实验,对比了首次匹配(FF)、三维资源分配(3D-RA)、路径优先(aW-PF)、共轭梯度频谱优先(CG-SF)算法性能。仿真结果表明,与其它算法相比,AT-SF算法在网络处于高负载状态时能获得更好的阻塞率和串扰性能。

蓝牙信道跳频序列的结构特征和均匀性质

分析了蓝牙信道跳频序列的结构特征,从理论上证明在一个远短于周期的时间间隔内序列是均匀性,给出了达到均匀的时钟条件.79跳蓝牙信道跳频序列的频隙滞留只可能出现在特定的时钟位置,23跳蓝牙信道跳频序列的频隙滞留对各码元出现的概率均为916×16.

差分跳频图案性能检验探讨

差分跳频是一种新的扩展频谱通信技术,它主要归结于一种G函数算法。本文在介绍差分跳频基本原理的基础上,将差分跳频的频率跳变过程建模成齐次马尔可夫链。分析了G函数的功能,重点讨论了差分跳频图案性能的检验方法;将常规跳频图案的一维均匀性检验进行了扩充,同时建议采用不可约性、频隙滞留检验,其中频隙滞留是本文提出应用于差分跳频图案性能的检验。

连续谱频域中高能量粒子激发的阿尔芬不稳定性

本文通过线性回旋动理学与磁流体力学(MHD)的混合模拟程序,采用(s,α)平衡模型。通过高能量粒子激发连续谱中的阿尔芬模式,研究了NSTX和MAST运行条件下连续谱中的αTAE和gap中的TAE各自特点,发现连续谱中的αTAE可存在于gap上方和gap下方,能被势阱很好的束缚。gap中的TAE可以无需势阱所束缚。还在MHD条件下,演示了环效应所引发的阿尔芬频隙,可以减小连续谱对本征模的耗散作用。

以m序列构成跳频序列族的方法研究

本文对用m序列构成跳频序列族的方法进行了研究，并以实例对有关构造方法进行了对比。

Finite-difference modeling of surface waves in poroelastic media and stress mirror conditions

During seismic wave propagation on a free surface, a strong material contrast boundary develops in response to interference by P- and S- waves to create a surface-wave phenomenon. To accurately determine the effects of this interface on surface-wave propagation, the boundary conditions must be accurately modeled. In this paper, we present a numerical approach based on the dynamic poroelasticity for a space–time-domain staggered-grid finite-difference simulation in porous media that contain a free-surface boundary. We propose a generalized stess mirror formulation of the free-surface boundary for solids and fluids in porous media for the grid mesh on which lays the free-surface plane. Its analog is that used for elastic media, which is suitable for precise and stable Rayleigh-type surface-wave modeling. The results of our analysis of first kind of Rayleigh （R1） waves obtained by this model demonstrate that the discretization of the mesh in a similar way to that for elastic media can realize stable numerical solutions with acceptable precision. We present numerical examples demonstrating the efficiency and accuracy of our proposed method.

抗衰落调制技术

本文着重论述衰落信道中几种有效的抗衰落调制技术的基本原理

Design of Anti-Collision Integrated Security Mechanism Based on Chaotic Sequence in UHF RFID System

Collision and security issues are considered as barriers to RFID applications.In this paper,a parallelizable anti-collision based on chaotic sequence combined dynamic frame slotted aloha to build a high-efficiency RFID system is proposed.In the tags parallelizable identification,we design a Discrete Markov process to analyze the success identification rate.Then a mutual authentication security protocol merging chaotic anti-collision is presented.The theoretical analysis and simulation results show that the proposed identification scheme has less than 45.1%of the identification time slots compared with the OVSF-system when the length of the chaos sequence is 31.The success identification rate of the proposed chaotic anti-collision can achieve 63%when the number of the tag is100.We test the energy consumption of the presented authentication protocol,which can simultaneously solve the anti-collision and security of the UHF RFID system.

Frequency in Middle of Magnon Band Gap in a Layered Ferromagnetic Superlattice

The frequency in middle of magnon energy band in a five-layer ferromagnetic superlattice is studied by using the linear spin-wave approach and Green＇s function technique. It is found that four energy gaps and corresponding four frequencie in middle of energy gaps exist in the magnon band along Kx direction perpendicular to the superlattice plane. The spin quantum numbers and the interlayer exchange couplings all affect the four frequencies in middle of the energy gaps. When all interlayer exchange couplings are same, the effect of spin quantum numbers on the frequency wg1 in middle of the energy gap Δw12 is complicated, and the frequency wg1 depends on the match of spin quantum numbers in each layer. Meanwhile, the frequencies wg2, wg3, and wg4 in middle of other energy gaps increase monotonously with increasing spin quantum numbers. When the spin quantum numbers in each layer are same, the frequencies wg1, wg2, wg3, and wg4 all increase monotonously with increasing interlayer exchange couplings.

A patchy-saturated rock physics model for tight sandstone based on microscopic pore structures

The wave-induced local fluid flow mechanism is relevant to the complex heterogeneity of pore structures in rocks.The analysis of the local fluid flow mechanism is useful for accurately describing the wave propagation characteristics in reservoir rocks.In the exploration and production of hydrocarbon reservoirs,the real stratum may be partially saturated with a multi-phase fluid mixture in general.Therefore,it is of great significance to investigate the wave velocity dispersion and attenuation features in relation to pore structures and fluids.In this work,the characteristics of fabric microstructures are obtained on the basis of pressure dependency of dry rock moduli using the effective medium theory.A novel anelasticity theoretical model for the wave propagation in a partially-saturated medium is presented by combining the extended Gurevich squirt-flow model and White patchysaturation theory.Numerical simulations are used to analyze wave propagation characteristics that depend on water saturation,external patchy diameter,and viscosity.We consider a tight sandstone from the Qingyang area of the Ordos Basin in west China and perform ultrasonic measurements under partial saturation states and different confining pressures,where the basic properties of the rock are obtained at the full gas saturation.The comparison of experimental data and theoretical modeling results shows a fairly good agreement,indicating that the new theory is effective.

Effects of axial static stress on stress wave propagation in rock considering porosity compaction and damage evolution

A wave equation of rock under axial static stress is established using the equivalent medium method by modifying the Kelvin-Voigt model.The analytical formulas of longitudinal velocity,space and time attenuation coefficients and response frequency are obtained by solving the equation using the harmonic method.A series of experiments on stress wave propagation through rock under different axial static stresses have been conducted.The proposed models of stress wave propagation are then verified by comparing experimental results with theoretical solutions.Based on the verified theoretical models,the influences of axial static stress on longitudinal velocity,space and time attenuation coefficients and response frequency are investigated by detailed parametric studies.The results show that the proposed theoretical models can be used to effectively investigate the effects of axial static stress on the stress wave propagation in rock.The axial static stress influences stress wave propagation characteristics of porous rock by varying the level of rock porosity and damage.Moreover,the initial porosity,initial elastic modulus of the rock voids and skeleton,viscous coefficient and vibration frequency have significant effects on the P-wave velocity,attenuation characteristics and response frequency of the stress wave in porous rock under axial static stress.

Compact wideband cavity-backed slot antenna

A wideband cavity-backed slot antenna operated in the ultra-high frequency （UHF） band is introduced. The antenna has a compact structure and low profile with the size ratio of the ground plane to the slot only 1.6：1. The measured impedance bandwidth of VSWR≤3 achieves 85.3%, covering a frequency range from 390 MHz to 970 MHz. The measured gain is about 5.5-7.5 dB.

Parameter estimation of sediment in the Yellow River based on the porous medium acoustic theory

Presently,the use of sub-bottom profiler sonar signals is limited to inversing the physical parameters of the sediment in the surface layer(first layer).In this study,based on the acoustic theory of porous medium,the acoustic inversion of the physical parameters of the lower layer(second layer)sediment is studied.When acoustic waves propagate in water and sediment media,interlayer reflection and transmission,intralayer attenuation,and other processes change the energy.The reflection and transmission coefficients of acoustic waves incident perpendicularly to the water–sediment and sediment–sediment interfaces are derived,and the effects of the reflection and transmission process of acoustic waves on the amplitude are quantified.The relationship between the frequency shift and relaxation time of the transmitted signal in different particle size sediments is established to estimate the corresponding attenuation coefficient using the frequency shift of each layer signal.On this basis,combined with the diffusion process of acoustic waves,the equation for extracting the acoustic wave reflection and transmission coefficients of each layer at the interface is derived from the measured sonar signal.Further calculations show that the sediment parameters have a greater influence on the reflection coefficient,and the feasibility of calculating the physical parameters of the lower sediment using the reflection coefficient has been proved.Under the premise of obtaining the physical parameters of surface sediment,this study provides specific methods and steps for inverting the physical parameters of the lower sediment.The on-site detection in the Xiaolangdi reservoir area of the Yellow River,combined with the sediment sampling test results,proved that the proposed method of inversion of the lower sediment parameters based on the porous medium acoustic theory is feasible.

Controllable Absorption and Dispersion Properties of an RF-driven Five-Level Atom in a Double-Band Photonic-Band-Gap Material

The probe absorption-dispersion spectra of a radio-frequency （RF）-driven five-level atom embedded in a photonic crystal are investigated by considering the isotropic double-band photonic-bandogap （PBG） reservoir. In the model used, the two transitions are, respectively, coupled by leading to some curious phenomena. Numerical simulations the upper and lower bands in such a PBG material, thus are performed for the optical spectra. It is found that when one transition frequency is inside the band gap and the other is outside the gap, there emerge three peaks in the absorption spectra. However, for the case that two transition frequencies lie inside or outside the band gap, the spectra display four absorption profiles. Especially, there appear two sharp peaks in the spectra when both transition frequencies exist inside the band gap. The influences of the intensity and frequency of the RF-driven field on the absorptive and dispersive response are analyzed under different band-edge positions. It is found that a transparency window appears in the absorption spectra and is accompanied by a very steep variation of the dispersion profile by adjusting system parameters. These results show that the absorption-dispersion properties of the system depend strongly on the RF-induced quantum interference and the density of states （DOS） of the PBG reservoir.

Field observations of debris-flow initiation processes on sediment deposits in a previous deep-seated landslide site

Although information regarding the initiation processes of debris flows is important for the development of mitigation measures,field data regarding these processes are scarce.We conducted field observations of debris-flow initiation processes in the upper Ichinosawa catchment of the Ohya landslide,central Japan.On 19 June 2012,our videocamera monitoring systems recorded the moment of debris-flow initiation on channel deposits(nine surges) and talus slopes(eight surges).The initiation mechanisms of these surges were classified into three types by analyzing the video images: erosion by the surface flow,movement of deposits as a mass,and upward development of the fluid area.The first type was associated with the progress of surface flow from the upper stream on unsaturated channel deposits.The second type was likely caused by an increase in the pore water pressure associated with the rising in the groundwater level in channel deposits;a continuous water supply from the upper stream by the surface flow might have induced this saturation.The third type was associated with changes in the downstream topography caused by erosion.The flow velocity of most surges was less than 3 m s^(-1) and they usually stopped within 100 m from the initiation point.Surges with abundant pore fluid had a higher flow velocity(about 3- 5 m s^(-1)) and could travel for alonger duration.Our observations indicate that the surface flow plays an important role in the initiation of debris flows on channel deposits and talus slopes.

Design of a fast-transient and high-stabilized GPS low dropout regulator

A high stabilized low dropout(LDO) voltage regulator fabricated for GPS radio frequency(RF) chip in SMIC 0.18μm CMOS technology is presented.The LDO mainly consists of bandgap reference,error amplifier,resistive feedback network and AC current path.A fast current path is added to improve the performance of LDO's transient response.Equivalent series resistance(ESR)compensation and internal Miller compensation are used to constitute the frequency compensation.The measurement results of the transient response of the output voltage show that it can recover within 2μs with less than 120 mV ripple when the load current is changed from 0 to 100 mA.The total quiescent current of LDO and bandgap reference(without load) is 260 μA.

Ag4Hg（SeO3）2（SeO4）: a novel SHG material created in mixed valent selenium oxides by in situ synthesis

Explorations of new second harmonic generation materials in Ag^+-Hg^2+/Bi^3+-selenites systems afforded three new silver selenium oxides, namely, Ag4 Hg(SeO3)2(SeO4)(1), Ag2Bi2(SeO3)3(SeO4)(2) and Ag5 Bi(SeO3)4(3). They exhibit flexible crystal chemistry. Compounds 1 and 2 are mixed valence selenium oxides containing Se(IV) and Se(VI) cations simultaneously. Compounds 1 and 3 exhibit a 3 D open framework with 4-, 6-and 8-member polyhedral ring tunnels along a, b and c axes. Compound 1 crystallized in a polar space group and could display a subtle frequency doubling efficiency about 35% of the commercial KH2PO4(KDP). UV-vis-NIR spectra reveal that compounds 1–3 are wide-band semiconductors with the optical bandgaps of 3.11, 3.65, 3.58 e V respectively. Theoretical calculations disclose that compounds2 and 3 are indirect band gap structures and their bandgaps are determined by Ag, Bi, Se and O atoms together.