High-frequency signal processing using magnetic layered structures

We present a review of theoretical and experimental results for tunable microwave band-stop filters, band-pass filters, phase shifters, and a signal to noise enhancer, all based on a microstrip geometry and using a variety of magnetic thin films and layered structures. These devices are compatible in size and growth process with on-chip high-frequency electronics. For devices based on metallic ferromagnetic films of Fe and Permalloy, the operational frequency ranges from 5 to 35 GHz for external fields below 5 kOe. For the band-stop filters, we observed power attenuation up to ∼100 dB/cm, and an insertion loss on the order of ∼2-3 dB, for both Permalloy and Fe-based structures. We also explore the use of thin films of hexagonal ferrites, antiferromagnets, and liquid crystals, and show that useful devices can be constructed with films less than one 1 μm in thickness.     

多层光子晶体滤波器研究

从双层结构出发研究了一种由多块不同的单周期光子晶体组合而成的多层结构的滤波器，论述了这种滤波器的工作原理，研究表明这种结构适于制作带通、窄带通过、带阻、宽带带阻、高通以及其它各种性能的滤波器。实验和理论研究的结果相一致。     

Dual-band microwave duplexer based on spiral resonators (SR) and complementary split ring resonators (CSRR)

In this work, a microstrip dual-band microwave duplexer implemented by means of a pair of dual-band branch-line hybrid couplers and a pair of dual-band band-stop filters is presented. The hybrid couplers are implemented by using complementary split ring resonators (CSRRs), etched in the ground plane, while the band-stop filters are made of spiral resonators (SRs) coupled to the host line. The measured duplexer characteristics are good and the device is compact by virtue of the small electrical size of the employed resonant elements. From this paper, it is clear that CSRRs and SRs are useful particles for the design of dual-band microwave systems requiring various microwave components.     

The Gribov Process: Soft Parton Interactions in So-Called Reggeon Field Theory

As shown in previous papers, Reggeon “Field” Theory is actually a Markov process describing the evolution of wee partons during a boost. In the present paper, the physical interpretation of scattering amplitudes and cross sections is discussed, both for the uncut (unlabelled) and cut (labelled) version. Elastic amplitudes and total cross sections, inclusive cross sections, fully diffractive events, and inelastic diffraction are all shown to have simple interpretations in the parton model. Finally, the connection with models for evolution of hard partons in QCD is discussed.     

Waveguide band-stop filters for 70 and 140 GHz

The construction of band-stop filters for 70 and 140 GHz by means of waveguide technology is described in detail including the most important dimensions. The transmission characteristic typically achieved is presented.     

紫外波段有机染料DMT掺杂SiO2薄膜的光谱特性

本文采用溶胶凝胶法合成了紫外波段有机染料DMT掺杂SiO₂薄膜和块体材料薄膜中掺杂浓度高达124×10^-2mol/L,块体材料浓度掺至15×10^-3mol/L由于SiO₂“笼”的束缚作用,在荧光光谱中未观察到荧光猝灭现象;由于SiO₂“笼”的极化作用,370nm的发射峰较其在环己烷中发生了34～44nm左右的红移;580～590nm的发射峰的量子效率比370nm的发射峰略高.     

有机染料TMQ掺杂的SiO2薄膜的光谱特性

采用溶胶 -凝胶法合成了紫外波段有机染料 TMQ掺杂的 Si O2 薄膜和块体材料。薄膜中掺杂的染料浓度高达 1.2 4× 10 -2 mol/ L,块体材料中染料浓度可掺至 1.5× 10 -3 mol/ L。由于Si O2 “笼”的束缚作用 ,在吸收光谱中未观察到二聚体的特征谱带 ,在荧光光谱中未观察到荧光猝灭现象 ;同时由于 Si O2 “笼”的极化作用 ,其吸收峰和发射峰的位置相对于其在环己烷溶液中的吸收峰和发射峰位置发生了 10 nm左右的红移。     

利用超相对论量子分子动力学模型研究交变梯度同步加速器能区Au+Au碰撞中的核阻止效应

运用修正的超相对论量子分子动力学模型研究了交变梯度同步加速器(AGS)能区Au+Au碰撞中的核阻止效应. 该模型考虑了形成和"预形成"粒子的平均场势、核子-核子弹性散射反应截面的介质修正和碎块形成的判断条件. 研究发现: 在AGS能区, 核阻止效应受到形成和“预形成”粒子的平均场势和核子-核子弹性散射反应截面介质修正的影响; 在中心快度区自由质子的产额偏大, 考虑新的碎块形成判断条件后, 此模型的理论计算结果与自由质子的实验结果符合得很好. 关键词： 超相对论量子分子动力学模型 交变梯度同步加速器能区 Au+Au碰撞 核阻止效应     

Spectral lines in hot dense matter

An algorithm is presented for the computation of photoabsorption cross sections at arbitrary temperature and matter density. The “average atom” model is refined to give an approximaate account for the different ionization stages. The broadening of spectral lines is accounted for in a simple approximation. Calculations are presented for the beryllium and germanium plasmas in the frequency region of spectral lines.     

Transmission line model for extraction of transmission characteristics in photonic crystal waveguides with stubs: optical filter design

A simple and efficient transmission line model is proposed here to study how the transmission characteristics of photonic crystal waveguides are tailored by introduction of stubs patterned in the photonic crystal lattice. It is shown that band-pass and band-stop optical filters can be easily designed and optimized when stubs of appropriate length are brought in. Since the lengths of the designed stubs are not necessarily integer multiples of the photonic crystal lattice constant, a geometric shift in a portion of the photonic crystal structure is shown to be essential. The proposed model is verified by using a rigorous numerical method. An excellent agreement is observed between the numerical results and the transmission characteristics as extracted by the proposed model.     

A spurious frequencies suppression method for optical frequency comb based microwave photonic filter

The traditional optical frequency comb (OFC) based microwave photonic filters (MPFs) are rigidly restricted to be operated in a single “Nyquist zone”, as varieties of spurious frequencies signals coexist in the output. Here, a method for spurious frequencies suppression in the OFC‐based MPF is proposed and experimentally demonstrated. The method is achieved by applying group velocity dispersion on the carrier combs to separate the filter transfer functions of the spurious frequencies from that of the input radio frequency signal. It is fairly simple and effective, and has no effect on the filter characteristic. With this method, the filter pass band can be freely tuned without the limitation of the “Nyquist zone”. It can be considered as a step forward for the practical application of the OFC‐based MPF.     

Effects of collisions on linear and non-linear spectroscopic line shapes

A fundamental physical problem is the determination of atom-atom, atom-molecule and molecule-molecule differential and total scattering cross sections. In this work, a technique for studying atomic and molecular collisions using spectroscopic line shape analysis is discussed. Collisions occuring within an atomic or molecular sample influence the sample's absorptive or emissive properties. Consequently the line shapes associated with the linear or non-linear absorption of external fields by an atomic system reflect the collisional processes occuring in the gas. Explicit line shape expressions are derived characterizing linear or saturated absorption by two- or three-level “active” atoms which are undergoing collisions with perturber atoms. The line shapes may be broadened, shifted, narrowed, or distorted as a result of collisions which may be “phase-interrupting” or “velocity-changing” in nature. Systematic line shape studies can be used to obtain information on both the differential and total active atom-perturber scattering cross sections.     

Infrared and mass regularization in AF field theories (I). φ63

In the framework of asymptotically free (AF) field theories we determine the correction terms in the renormalization group (RG) approach to deep inelastic (DI) scattering and to the Drell-Yan (DY) process. This leads us to an order g² analysis of the DI/DY parton cross sections. Some of their contributions reveal ultraviolet (UV), infrared (IR) and mass (M) divergences which, after regularization, are removed by renormalization, IR and (partially) M cancellation. The initial-state M divergences, persisting in both processes, are removed by M factorization. Consistent IR and M regularization is constrained by the double-cut rule: its meaning and implications are explained. The calculations are performed in φ₆³ theory which is AF, IR finite and technically simple. We use “on-shell”, “off-shell” and “massless” (n-dimensional) mass assignments and demonstrate explicitly the regularization independence of the correction term.     

Modulating lamb wave band gaps using an elastic metamaterial plate

Modulating band gaps (extending the bandwidths or shifting into a lower frequency range) is a challenging task in phononic crystals. In this paper, elastic metamaterial plates composed of a square array of “hard” stubs or “soft” stubs on both sides of a 2D binary locally resonant plate are proposed, and their band structures are studied. The dispersion relationships and the displacement fields of the eigenmodes are calculated using finite element methods. Numerical results show that the band gaps are shifted to lower frequencies and the bandwidths are enlarged compared to classic elastic metamaterial plates. A conceptual “analogousrigid mode” that includes an “out-of-plane analogous-rigid mode” and an “in-plane analogous-rigid mode” is developed to explain these phenomena. The “out-of-plane analogous-rigid mode” mainly adjusts the band gaps into the lower frequency range, and the “in-plane analogous-rigid mode” mainly enlarges the bandwidth. Furthermore, the band gap effects of composite “hard” stubs and “soft” stubs are investigated. The results show that the location of the band gaps can be modulated into a relatively lower frequency and the bandwidth can be extended by the use of different composite stubs. These elastic wave properties in the proposed structure can be used to optimize band gaps and possibly produce low-frequency filters and waveguides.     

Quadratic corrections to three‐point functions

Following the recent progress on the calculation of three‐point correlators with two “heavy” (with large quantum numbers) and one “light” states at strong coupling, we compute the logarithmic divergent terms of leading bosonic quantum corrections to correlation functions with “heavy” operators corresponding to simple string solutions in AdS₅ × S⁵. The “light” operator is chosen to be the dilaton. An important relation connecting the corrections to both the dimensions of “heavy” states, and the structure constants is recovered.     

Search for the neutrino magnetic moment in the elastic νe scattering

The possibility of detecting the anomalous neutrino magnetic moment from comparison of the “electromagnetic” and “electroweak” contributions to the differential and total cross sections of neutrino-electron scattering is considered. The results of quantitative analysis and a graphical image of the cross sections are presented for the case of scattering of beryllium solar neutrinos by an electronic target.     

手征材料构成的简立方光子晶体光子带结构计算——平面波法

发展了适于计算由手征材料组成的光子晶体的光子带结构的平面波法。在此基础上，研究了由手征材料组成的简立方光子晶体的光子带结构。计算表明：手征材料“球形原子”在电介质中排列所组成的科立方光子晶体和电介质“球形原子”在手征材料中排列所组成的简立方光子晶体，不仅都存在光子带隙，而且存在截止频率，在该频率以下的区域无传播模存在，本语文认了这种光子晶体的潜在应用。     

Low Level Laser Therapy: laser radiation absorption in biological tissues

We theoretically show that a polarization-independent optical band-stop filter operation can be performed by a two-dimensional sub-wavelength array of symmetric cross-shaped plasmonic nanoantennas. The proposed filter’s optical properties can be controlled by varying the size and periodicity of the plasmonic nanoantennas. So, this can be used to design filters in many frequency ranges of interest. In addition, the filter is simply constructed as a coating with only 30-nm thickness, which is much thinner than the operation wavelength, and thus facilitates the fabrication and further large-scale optical integration.     

Big entropy fluctuations in statistical equilibrium: The macroscopic kinetics

Large entropy fluctuations in the equilibrium steady state of classical mechanics are studied in extensive numerical experiments in a simple strongly chaotic Hamiltonian model with two degrees of freedom described by the modified Arnold cat map. The rise and fall of a large separated fluctuation is shown to be described by the (regular and stable) “macroscopic” kinetics, both fast (ballistic) and slow (diffusive). We abandon a vague problem of the “appropriate” initial conditions by observing (in a long run) a spontaneous birth and death of arbitrarily big fluctuations for any initial state of our dynamical model. Statistics of the infinite chain of fluctuations similar to the Poincaré recurrences is shown to be Poissonian. A simple empirical relationship for the mean period between the fluctuations (the Poincaré “cycle”) is found and confirmed in numerical experiments. We propose a new representation of the entropy via the variance of only a few trajectories (“particles”) that greatly facilitates the computation and at the same time is sufficiently accurate for big fluctuations. The relation of our results to long-standing debates over the statistical “irreversibility” and the “time arrow” is briefly discussed.