Laser Radar range optimization for detecting and tracking Airborne cooperative targets

A high resolution Nd-YAG pulsed Laser Radar LIDAR system is proposed for detecting and tracking Airborne cooperative retro-reflector carrying targets against noise, clutter and back-scatter sources. A previous range computation method is improved and new possibilities of coherent heterodyne detection and phase conjugate elements are discussed.The presented analysis and computation method has proved to be valuable in the feasibility and design stages of operation LIDAR detection and tracking systems.     

激光雷达回波信号的蒙特卡罗模拟研究:I.均匀薄雾的多重散射强度分布(英文)

本文简要报道了激光雷达回波信号及多重散射强度分布的蒙特卡罗模拟计算结果。激光雷达系统采用共轴设计 ,计算中采用具有一定厚度、均匀分布的球形薄雾粒子来模拟大气环境 ,研究了粒子尺寸对回波信号的影响 ,获得了不同粒子半径、不同接受视场角条件下多重散射信号强度分布的经验公式。以上两套经验公式具有良好的校正系数 ,可以直接用于激光雷达系统设计中多重散射效应的研究 ,节省大量的模拟计算时间 ,提高设计效率     

激光雷达回波信号的蒙特卡罗模拟研究:Ⅰ.均匀薄雾的多重散射强度分布

本文简要报道了激光雷达回波信号及多重散射强度分布的蒙特卡罗模拟计算结果。激光雷达系统采用共轴设计,计算中采用具有一定厚度、均匀分布的球形薄雾粒子来模拟大气环境,研究了粒子尺寸对回波信号的影响,获得了不同粒子半径、不同接受视场角条件下多重散射信号强度分布的经验公式。以上两套经验公式具有良好的校正系数,可以直接用于激光雷达系统设计中多重散射效应的研究,节省大量的模拟计算时间,提高设计效率。     

Supporting theory of a new magnetic separator and classifier. Limiting conditions: Part I – Non-magnetic particles

A new device, MAGCLA™, which is capable to separate and classify particles according to their magnetic susceptibility, was developed by the authors. In a previous article the equations of movement for non-magnetic particles in this new device were analyzed and in this paper the limiting conditions set by the different variables and equations of movement are presented for the case of the non-magnetic particles. The knowledge of these limiting conditions is important as they set the boundaries within which we may manipulate the MAGCLA™’s operating and design variables.     

Supporting theory of a new magnetic separator and classifier. Limiting conditions: Part II – Magnetic particles

A new device, MAGCLA™, which is capable to separate and classify particles according to their magnetic susceptibility, is being developed by the authors. In a previous article the equations of movement for magnetic particles in this new device were analyzed and in this paper the limiting conditions for the different variables and equations of movement are presented for the magnetic particles case. The knowledge of these limiting conditions is important as they set the boundaries within which we may manipulate the MAGCLA™’s operating and design variables.     

Monte-Carlo calculations of cloud returns for ground-based and space-based LIDARS

A Monte-Carlo model is described which has been developed for calculation of multiply scattered LIDAR returns. Results are shown for the common problem selected by the MUSCLE (MUltiple SCattering LIDAR Experiments) group for intercomparison, which represents a typical ground-based cloud-sensing scenario. This is contrasted with returns from the same cloud sensed by a space-based LIDAR, where multiple-scattering effects are much greater. The magnitude of multiple-scattering effects is seen to be largely determined by the optical depth across the receiver field of view at the cloud.     

Nonlinear-closed equations for the first and the second moments of macroscopic variables

A quantum-mechanical theory of describing systems far from equilibrium is developed. A set of time evolution equations for every moment of macroscopic variables is derived with the aid of the new idempotent operator. From this set of equations nonlinear but closed equations for the first and the second moments are obtained directly. The theory is applied to the problem of a spin interacting with its surroundings. The Bloch equation with the Landau-Lifshitz friction term is derived quantum mechanically. The relation between this method and that of system size expansion is discussed.     

Integrated Front-End Radar Receivers at Ka-Band

This paper describes the Integrated Finline Front-end Radar Receivers at Ka-Band. The Front-receivers developed for Radar applications include combining of finline components on a single MIC substrate with various planar transmission lines. The integrated systems so developed have better noise figure and control over phase and gain imbalances as compared to discrete component systems. Two types of Integrated Front-ends Radar receivers are described here. The developed systems are highly compact and reliable.     

Including inputs and control within equation-free architectures for complex systems

The increasing ubiquity of complex systems that require control is a challenge for existing methodologies in characterization and controller design when the system is high-dimensional, nonlinear, and without physics-based governing equations. We review standard model reduction techniques such as Proper Orthogonal Decomposition (POD) with Galerkin projection and Balanced POD (BPOD). Further, we discuss the link between these equation-based methods and recently developed equation-free methods such as the Dynamic Mode Decomposition and Koopman operator theory. These data-driven methods can mitigate the challenge of not having a well-characterized set of governing equations. We illustrate that this equation-free approach that is being applied to measurement data from complex systems can be extended to include inputs and control. Three specific research examples are presented that extend current equation-free architectures toward the characterization and control of complex systems. These examples motivate a potentially revolutionary shift in the characterization of complex systems and subsequent design of objective-based controllers for data-driven models.     

Eye-safe compact scanning LIDAR technology

A 1.5-μm eye-safe, 3-D scanning, and compact Mie LIght Detection and Ranging (LIDAR) is presented. The transmitter of the LIDAR is based on a KTA optical parameter oscillator (OPO) resonator. For detecting return signals, an InGaAs APD is used. The all solid-state OPO laser transmitter has the feature of small volume and lightweight, which allows a 165-lb compact eye-safe scanning LIDAR to be constructed. A system simulation using our own model was conducted to direct the system development. A method to solve the problem with small active area APD detectors was developed and described. The preliminary field-test measurement results indicated that the LIDAR has the capability to detect aerosols and clouds in lower atmospheres up to three dimensions.     

Stability of the critical behavior of weakly disordered systems against replica symmetry breaking

A field-theoretical approach is used to describe the critical behavior of weakly disordered systems with a p-component order parameter. Renormalization group (RG) analysis of the effective replica Hamiltonian of a model with replica-unsymmetrical interaction potential is carried out in a two-loop approximation directly for three-dimensional systems. The Padé-Borel summation technique is used to determine fixed points of the RG equations for the case of a single-step replica symmetry breaking (RSB). Analysis of their stability showed that the type of stable critical behavior of the disordered systems against the RSB effects remains as before.     

一种简单的双折射光交错复用滤波器设计方法

针对双折射光交错滤波器的设计,在傅里叶级数对比正向搜索法的基础上,发展了一种基于傅里叶级数的Cesaro方法的设计方法.利用该方法设计了三级级联的双折射光交错滤波器,计算方法更加简单,所获得的结构参量可以满足较高设计要求.     

A generalised mathematical model and analysis for integrated multi-channel vibration structure-control interaction systems

A generalised mathematical model and analysis for integrated multi-channel vibration control-structure interaction systems are developed. The governing equations describing the interactions between a generalised elastic structure and a multi-channel electromagnetic excitation and control system are derived. Based on these equations, the stability and dynamic response of the system are analysed. The introduction of an additional dynamic impedance matrix between structure and control system allows vibration structure-control interaction mechanisms to be investigated. The generalised theory provides a basis to measure exactly the dynamic parameters of the structure negating any influence of the excitation and control system. It also allows the design of a more effective control system taking into account the interactions of the control system with structural motions and vice versa. To illustrate the general formulations developed and their applications, simple one- and two-channel systems are investigated using non-dimensional parameters.     

Zur theorie polarer multikomponentsysteme

A fluid mixture consisting of molecules with permanent electric dipole moment and scalar polarizability is described by means of correlation functions. To analyse the two-particle correlation functions we extend the graph-theoretical conception developed by Wertheim in the case of multicomponent systems by using graphs with colored points. In order to carry out a topological reduction of these sets of colored graphs the corresponding functions are found to be matrices or tensors. By the aid of a new connecting formalism the tensor notation preserves the structure of the equations in the analysis of correlation functions. These functions can be separated with respect to the range of interactions involved. Then, in applying the results to the case of a polar multicomponent mixture we can derive equations for the dielectric constant of systems consisting of both rigid and polarizable dipoles. These equations involve a correlation factor matrix which is the multicomponent equivalence of the Kirkwood factor. The dielectric expressions are used to obtain dipolar contributions to the Helmholtz free energy of mixing.     

Sensing of semi-rough targets embedded in atmospheric turbulence by means of stochastic electromagnetic beams

An active bistatic LIDAR system operating through atmospheric turbulence is considered. Illumination field is assumed to be an electromagnetic Gaussian-Schell model beam. Target surface is modeled as a combination of isotropic phase screen governed by Gaussian statistics, to account for its roughness, and a Gaussian lens to account for its size and radius of curvature. With the help of a recently developed tensor method for propagation of stochastic electromagnetic beams through ABCD systems and random media we examine the evolution of states of coherence and polarization of the beam. In the case of unresolved flat (planar) target we show that by comparing coherence and polarization properties of the illumination beam and of the return beam it is possible to predict the typical roughness of the target surface.     

Efficient model order reduction for dynamic systems with local nonlinearities

In the nonlinear structural analysis, the nonlinear effects are commonly localized and the rest of the structure behaves in a linear manner. Considering this fact, this research work proposes a harmonic balance solution in order to determine the nonlinear response of the structures. The solution is simplified by using an exact dynamic reduction along with the modal expansion technique. This novel approach, which is applicable to both discrete and continuous systems, converts the system equations of motion in each harmonic to a small set of nonlinear algebraic equations. The full set of system equations is reduced to a discrete system with a few generalized degrees of freedom (DOFs) confined to the localized nonlinear regions. The resultant reduced order model is shown to be accurate enough for determining the periodic response. To demonstrate the capability of the proposed method, numerical case studies for continuous and discrete systems, including systems with internal resonance, have been studied and the outcomes are validated with benchmark studies. In addition, the method is applied in the identification process of an experimental test setup with unknown frictional support parameters, and the results are presented and discussed.     

Prediction of averaged energy for moderately damped systems with strong coupling

In this paper, the prediction of averaged energy of damped structural-acoustic systems is investigated. A simplified energy finite element method, referred to as EFEM⁰, is developed based on the energy flow analysis (EFA) equations and implemented using the finite volume method. The resulting formulations can be incorporated into statistical energy analysis (SEA) software and extends SEA application to moderately damped systems with strong coupling. The formulations are verified against analytical solutions for a single beam and coupled beams with both strong and weak coupling. A hybrid technique consisting of the EFEM⁰ approximation superimposed on a direct field is used to model moderately damped plates. For lightly damped systems, both methods produce acceptable results. For moderately damped two-dimensional systems, the EFEM⁰ method augmented with the direct field component produces significantly improved results.     

激光雷达辅助驾驶道路参数计算方法研究

针对特定场景辅助驾驶的需求,构建道路场景车载激光雷达三维扫描系统,并设计基于三维激光点云的道路参数提取与计算方法,包括路面宽度、横杆或桥梁或隧道限高、拐弯半径等等,为辅助判断道路的可通过性提供决策依据。测试和对比实验表明,所设计算法效果稳定、精度良好,在效率和自动化程度上有一定优势,可为辅助驾驶提供非常有益的决策参数。     

Design for high precision and off-axis compact collimation system

An off-axis reflective collimation system design for application in Radar systems is presented. The cross-section of the system has a round configuration for compactness. Based on the spatial analytic geometry and the reflection law (in vector form), space propagation rules for laser beam are derived. The optical design is simulated and optimized using MATLAB. The highly collimated results are presented.