An algorithm for the optimal design of passive vibration controllers for flexible systems

A gradient algorithm is developed for the optimal design of discrete passive dampers in the vibration control of a class of flexible (distributed parameter) systems. A complete mathematical development is presented for slender beams in flexural vibration. The algorithm systematically seeks to make the modal damping and natural frequencies of the system reach a set of preassigned values. Single damper and the two damper control examples indicate that the proposed algorithm converges faster than the Davison method used in reference [1] for those cases.     

航空飞机计算机通信中滤波器的优化设计

航空飞机计算机通信系统进行通信的过程中,由于航空飞机上的电子设备相互之间的电磁干扰严重,导致信道中存在大量的干扰信号。提出基于小波变换算法的抗干扰滤波器设计方法。根据小波变换算法相关原理,综合航空飞机通信中特有的软阀值特点,利用自适应调整参数的方法得到高空通信中的最优小波系数阀值,使得高空噪声过滤阀值函数具有更强的适应性。利用新的阀值函数设计了新的滤波器,对行滤波模块和列滤波模块的设计进行了详细阐述。实验结果表明。利用设计的滤波器能够对航空飞机计算机通信过程中的干扰信号进行有效滤波,缩短了滤波时间,提高了高空通信系统的抗干扰能力。     

The optimal energy-efficient design of user-specific RIS-aided uplink communication system

Reconfigurable intelligent surfaces (RIS) has the potential to be an important technology for the sixth-generation (6G) communications in future. Especially, RIS can improve communication performance by extending coverage or improving the conditions for signal propagation. Most of the current work mainly focused on the reflective type RIS. In contrast, the recent emergence of user-specific reconfigurable intelligent surfaces (US-RIS) is a transmissive type. Unlike reflective RIS, which is typically deployed near the base station, US-RIS is deployed on the user side and is capable of adjusting the phase of the user’s signal. In this paper, our research focuses on energy-efficient in the context of quality of service requirements. For this purpose, we formulate a joint optimization problem. As the optimization problem is non-convex, we separate and treat these variables in several sub-problems. The sub-problems are solved separately for the variables by alternating updates, either using closed-form solutions or using the semidefinite relaxation (SDR) method. In addition, it is clear from the simulation results that US-RIS is able to improve the energy efficiency of the communication system. Furthermore, the increased number of US-RIS elements can also improve the energy efficiency of the communication system.     

Non-iterative optimal design of quantum controls

A non-iterative means for quantum control design is introduced with the aim of offering practical designs that can later be fine-tuned with laboratory closed-loop techniques. The procedure recognizes that Hamiltonians for realistic system control applications are rarely known accurately. The algorithm takes advantage of this fact by allowing for managed deviations in the equations of motion, thus removing the standard Lagrange multiplier. Suitable time-dependent cost functional weights are introduced that eliminate the traditional final time matching condition, thereby producing non-iterative design equations as an initial value problem. Removal of the final time condition also eliminates the demand that the target state be reached at any artificially imposed time. Tests on a simple molecular system indicate that the algorithm leads to well-behaved designs and that the weight functions are adequately estimated by order of magnitude analysis. Received 30 June 2000 and Received in final form 22 November 2000     

Toward a theory of evaporation processes in liquid-solid systems

A theoretical analysis is presented of isothermal evaporation of a volatile component from a solid covered by a liquid layer. Binary compounds are considered, with the covering liquid produced by thermal decomposition of the solid material. It is shown that the relaxation time of the volatile concentration profile is much shorter than the characteristic time of motion of the melting interface; i.e., the instantaneous profile of volatile concentration at any time is a linear function of the spatial coordinate. A new nonlinear Stefan-type problem of evaporation in a solid-liquid-vacuum system is formulated that involves two moving phase transition interfaces: an evaporating interface and a melting interface. Exact analytical solutions to the problem are found. It is shown that the melting interface moves faster than the evaporating interface; i.e., the thickness of the liquid layer increases with time, its growth rate increasing with evaporation rate coefficient. It is demonstrated that the concentration profile evolves self-similarly in the course of time. An increase in evaporation rate coefficient leads to a steepening of the concentration gradient across the liquid layer, changing the volatile concentration at the evaporating interface, and the evaporative flux changes accordingly.     

The evaporation of Q-balls

In extended electroweak models with scalar fields carrying lepton number, it is possible for these fields to form extended objects of the Q-ball sort. In general, these are destabilised by the Yukawa coupling of the scalar to neutrinos. This decay process takes place only on the surface of the object, not in the interior. Thus the Q-balls evaporate away. We set up the general theory of this process, find an absolute upper bound for the evaporation rate, and explicitly compute the rate in a simple case.     

35kJ高温超导储能磁体的优化设计

介绍了35kJ高温超导储能磁体的设计步骤。为了减少常规寻优方法的计算量,将加权粒子群优化算法(WPSO)引入到高温超导储能磁体的优化设计中,给出了用B i-2223超导线材进行35kJ储能磁体设计的优化结果,分析了高温超导线材的各向异性对磁体临界电流的影响,并比较了两种不同的单螺线管磁体结构在不同优化目标的情况下,超导线材用量和杂散磁场的分布的变化。     

The Bayes' optimal receiver for digital fibre optic communication systems

A rigorous treatment of the optimal receiver for digital fibre optic systems is presented. Starting from physical and theoretical considerations, a signal-plus-noise model is obtained for the input stage of an optical receiver. The model is used to set up a hypothesis-testing problem for a transmitted sequence of binary independent and identically distributed information symbols. The Bayes optimal receiver is next derived using the Karhunen-Loève expansion, and upper bounds of the Chernoff type are obtained for its performance. The derived formulae are applied to a typical system and numerical results are obtained which show an improvement of at least 4 db in favour of the optimal receiver when compared to its conventional counterpart at a 10^–9 error rate.     

Robust locally optimal servo control systems

Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 96–99, September, 1995.     

Time optimal quantum control of two-qubit systems

We study the optimal quantum control of heteronuclear two-qubit systems described by a Hamiltonian containing both nonlocal internal drift and local control terms.We derive an explicit formula to compute the minimum time required to steer the system from an initial state to a specified final state.As applications the minimal time to implement Controlled-NOT gate,SWAP gate and Controlled-U gate is calculated in detail.The experimental realizations of these quantum gates are explicitly presented.     

Time optimal control of two-level quantum systems

The objective of time-optimal control that helps to minimize relaxation losses, is the evolution of a quantum state from a given initial mixed state to a final target mixed state in minimum time. In this paper, we study a time-optimal control problem of the dynamic of a pure two-level system with unbounded control using Pontryagin's minimum principle and obtain the minimal time for some initial and final states. The results will apply to basically all qubit systems that one can consider such as NMR spectroscopy, trapped ions, superconducting qubits, etc. We also show that these results hold for pure states, and only the direction $\hat{n}$ is important in the evolution of a quantum state. In this work, the problem of computing minimum time to produce any unitary transformation $U_f\in SU(2)$ is reduced to finding the minimum time to steer the system from an initial to a final state.     

MgB2超导储能磁体可行性研究及结构优化

MgB2作为超导材料中的一颗新星,可以很好的应用于超导磁体。文中对比分析了作为超导磁体应用材料MgB2的超导特性,之后进行了MgB2磁体电磁设计。并通过与已有的Bi系超导磁体的对比,论证了MgB2在超导储能磁体应用中的可行性。针对MgB2超导特性进行磁体结构优化设计,得到两种新思路的螺管型磁体模型,都能够达到更好的经济性。     

300MJ环状高温超导储能磁体的优化设计

介绍了300M J环状高温超导储能磁体优化设计的步骤。为了提高优化设计的效率,减少常规寻优方法的计算量,将改进的粒子群优化算法引入到高温超导储能磁体的优化设计中,给出了用B i-2223超导线材进行300M J环状储能磁体设计的优化结果,并采用商用电磁场有限元分析软件ANSYS对本文关于环状螺线管系统磁场、能量计算方法的正确性进行了验证。     

A low loss thin-film optical waveguide for integrated optics made by vacuum evaporation

We report the fabrication of low-loss thin film waveguides made by electron beam evaporation of a special glass on fused quartz substrates. The losses are as low as (1.2 ± 0.1) dB/cm at a wavelenght of λ = 676.4 nm and 4.3 dB/cm at λ = 476.2 nm. The dispersion of the waveguide material in the spectral range of 470 nm to 670 nm and the measurement setup used are discussed.     

Study of preparation of Au-LiF-Au and Al-LiF-Au systems by vacuum evaporation

The structure of thin LiF film has been investigated with regard to its continuity in Au-LiF-Au, Al-LiF-Au systems. The samples have been evaporated on unheated glass substrates at 5×10^?5 torr without breaking vacuum. The number of short-circuited samples was evaluated in dependence on the angle of evaporation and thickness of the LiF film. It appears that the angle of evaporation of the value about ofω=20° already increases the number of short circuits in the case of Au-LiF-Au, meanwhile in the case of Al-LiF-Au it has no influence. Explanation is given by means of shadow effects which take place in thin LiF film in the system Au-LiF-Au. Replicas of LiF on Au and LiF on Al show in the first case that the layer consists of larger crystals and is less homogeneous. Difference between systems mentioned above can be seen also from the dependence of the number of short-circuited samples on the thickness of thin LiF film at the angle of evaporationω=0°. It is possible to draw boundary thicknesses of thin LiF film for obtaining non-short-circuited samples. In the case of Al-LiF-Au it is about 250 Å and in the case of Au-LiF-Au about 500 Å.     

The optimal design for weak optical feedback semiconductor laser with frequency modulation

In this paper the frequency modulation characteristics the semiconductor laserwith weak optical feedback are presented,considering both the frequency deviation and thespurious intensity modulation.The frequency modulation can be realized without spurious in-tensity modulation under proper feedback conditions.There is an optimal feedback intensity tomaximize the frequency deviation.