An approach to enhance the receiver sensitivity with SOA for optical communication systems

In this paper, we investigate an SOA (semiconductor optical amplifier) preamplifier structure by optimizing the carrier lifetime in order to reduce the amplified spontaneous emission (ASE) noise and crosstalk, with adequate gain increase. This proposed SOA optical preamplifier has no need of optical alignment and antireflection coating. This structure of SOA eliminates the need of optical filter, and exhibits large tolerance to the input light wavelength. The receiver sensitivity is investigated for single and multi channel transmission links. The received power of − 50.34 dBm is observed at bit error rate (BER) 10^− 12 for 10 Gb/s with PIN receiver. Further, the impact of gain, amplified spontaneous emission power and gain variation for different carrier lifetime with input power for OOK system is illustrated. The proposed SOA has constant gain of 30.06 dB up to gain saturation for carrier lifetime 0.18 ns. It is predicted that low value of carrier lifetime suffers less from ASE noise.     

Design sensitivity analysis for sequential structural-acoustic problems

A design sensitivity analysis of a sequential structural-acoustic problem is presented in which structural and acoustic behaviors are de-coupled. A frequency-response analysis is used to obtain the dynamic behavior of an automotive structure, while the boundary element method is used to solve the pressure response of an interior, acoustic domain. For the purposes of design sensitivity analysis, a direct differentiation method and an adjoint variable method are presented. In the adjoint variable method, an adjoint load is obtained from the acoustic boundary element re-analysis, while the adjoint solution is calculated from the structural dynamic re-analysis. The evaluation of pressure sensitivity only involves a numerical integration process for the structural part. The proposed sensitivity results are compared to finite difference sensitivity results with excellent agreement.     

MEMS accelerometer embedded in a self-mixing displacement sensor for parasitic vibration compensation

A self-mixing (SM) laser displacement sensor coupled with a microelectromechanical system (MEMS) accelerometer is presented that enables reliable displacement measurements even in the case of a nonstationary laser head. The proposed technique allows the use of SM-based sensors for embedded applications. The system resolution is currently limited to approximately 300?nm due to the noise characteristics of the currently used accelerometer. It is shown that this resolution can be greatly improved by the use of a low noise accelerometer.     

An approach based on tool mode control for surface roughness reduction in high-frequency vibration cutting

The presented research work, aimed at deeper understanding of vibrational process during high-frequency vibration cutting, is accomplished by treating cutting tool as an elastic structure which is characterized by several modes of natural vibrations. An approach for surface quality improvement is proposed in this paper by taking into account that quality of machined surface is related to the intensity of tool-tip (cutting edge) vibrations. It is based on the excitation of a particular higher vibration mode of a turning tool, which leads to the reduction of deleterious vibrations in the machine-tool-workpiece system through intensification of internal energy dissipation in the tool material. The combined application of numerical analysis with accurate finite element model as well as different experimental methods during investigation of the vibration turning process allowed to determine that the most favorable is the second flexural vibration mode of the tool in the direction of vertical cutting force component. This mode is excited by means of piezoelectric transducer vibrating in axial tool direction at the corresponding natural frequency, thereby enabling minimization of surface roughness and tool wear.     

Structural surface intensity: An alternative approach in vibration analysis and diagnosis

The physical meaning of structure-borne sound intensity is discussed. The relationships which express the intensity on a free surface are evaluated in terms of measurable physical quantities. Five such independent quantities, three strains and two velocities, have to be simultaneously detected and processed in an appropriate way in order to get intensity readings. Formulae are presented for both the active and the reactive intensities, and for the intensity spectra. A technique is proposed, based on use of conventional transducers, which can be applied to practical surface intensity measurements. The accuracy of such a technique is discussed, and various possibilities for expressing the measurement readings are examined. A particular measurement is described and the results given of the surface intensity distribution obtained by conventional equipment at several points of an elevator drive mechanism.     

An efficient approach to optimize the vibration mode of bar-type ultrasonic motors

The electromechanical coupled dynamic model of the stator of the bar-type ultrasonic motor is derived based on the finite element method. The dynamical behavior of the stator is analyzed via this model and the theoretical result agrees with the experimental result of the stator of the prototype motor very well. Both the structural design principles and the approaches to meet the requirements for the mode of the stator are discussed. Based on the pattern search algorithm, an optimal model to meet the design requirements is established. The numerical simulation results show that this optimal model is effective for the structural design of the stator.     

Iterative approach for the eigenvalue problems

An approximation method based on the iterative technique is developed within the framework of linear delta expansion (LDE) technique for the eigenvalues and eigenfunctions of the one-dimensional and three-dimensional realistic physical problems. This technique allows us to obtain the coefficient in the perturbation series for the eigenfunctions and the eigenvalues directly by knowing the eigenfunctions and the eigenvalues of the unperturbed problems in quantum mechanics. Examples are presented to support this. Hence, the LDE technique can be used for nonperturbative as well as perturbative systems to find approximate solutions of eigenvalue problems.     

A small-parameter approach for few-body problems

A procedure to solve few-body problems is developed which is based on an expansion over a small parameter. The parameter is the ratio of potential energy to kinetic energy for states having not small hyperspherical quantum numbers, K>K ₀. Dynamic equations are reduced perturbatively to equations in the finite-dimension subspace with K ⩽ K ₀. Contributions from states with K>K ₀ are taken into account in a closed form, i.e., without an expansion over basis functions. Estimates concerning the efficiency of the approach are presented. The text was submitted by the author in English.     

Decoupled networks: An approach to low symmetry vibrational problems

By considering the condition for lowest order decoupling of the vibrations of local atomic configurations of continuous bonded covalent systems, we arrive at an approximation which we call a decoupled network (DCN). The DCN them serves as a basis for a method of relating vibrational and configurational data in low symmetry systems. This method applied to amorphous, crystalline and molten As₂S₃ yields significant insight into the relationship between the features of the vibrational spectra and the local order.     

Friction-induced vibration: Quantifying sensitivity and uncertainty

The limited success of predictive models of friction-induced vibration can, in part, be attributed to the inherent sensitivity of friction-coupled systems to variations, often uncontrolled, in parameter values such as the friction coefficient. This paper explores the sensitivity and uncertainty of predictions from a modal point of view, using models of a realistic complexity. A method for efficiently estimating prediction error bounds is presented and validated using representative parametric uncertainties. Measurement uncertainties are quantified providing an input for the error-bound analysis. Taken together, this forms the foundation for a direct comparison of predictions with experimental results from sliding contact tests.     

An optimization approach to multi-dimensional time domain acoustic inverse problems

An optimization approach to a multi-dimensional acoustic inverse problem in the time domain is considered. The density and/or the sound speed are reconstructed by minimizing an objective functional. By introducing dual functions and using the Gauss divergence theorem, the gradient of the objective functional is found as an explicit expression. The parameters are then reconstructed by an iterative algorithm (the conjugate gradient method). The reconstruction algorithm is tested with noisy data, and these tests indicate that the algorithm is stable and robust. The computation time for the reconstruction is greatly improved when the analytic gradient is used.     

A reduction method for problems of vibration of orthotropic plates

It is shown that the problem of vibration of an orthotropic plate can be reduced to that of another orthotropic plate by a simple co-ordinate transformation, and reduction formulae are obtained. To justify the reduction formulae, fundamental natural frequencies of orthotropic rectangular plates with various boundary conditions and of a clamped orthotropic elliptical plate are discussed. As an example, an exact natural frequency of a simply supported generally orthotropic skew plate with special flexural rigidities is obtained from that of a simply supported isotropic rectangular plate.     

An embedded design for monitoring and controlling temperature

Each and every part of human life is somehow linked with the embedded products. Embedded systems are product of hardware and software co design. It is becoming an integral part of engineering design process for efficient analysis of data acquisition. Data acquisition implies the gathering of information about a system or process. It is the process of collecting data in an automated way from analog and digital sources of measurement, such as sensors and devices under test. The present paper describes the design of an embedded system for the control of temperature and light intensity in a single system using sensors, microcontroller and Liquid Crystal Display (LCD). It describes the controlling action incorporated in the hardware to control any device connected when specific conditions are met.     

A numerical approach for flow-induced vibration of pipe structures

A structural impedance approach is extended for the dynamic analysis of pipe structures conveying fluid flow. The method is efficient in computation and convenient for studying transient responses. Thus, it is possible to study the transition from a stable condition to an unstable condition of the pipe structure as the flow speed increases. The structure may also exhibit different modes of instability. The present approach predicts the mode without prior assumption. Numerical examples are given for a hanging cantilever and a simply supported pipe. The critical speed associated with the dynamic stability is calculated and compared with available analytical and experimental results.     

An identity for 4-spacetimes embedded intoE 5

We show that if a 4-spacetimeV ₄ can be embedded intoE ₅ then, ifb _ijis the second fundamental form tensor associated withV ₄, the quantity (traceb)·b _ij ^/−1 depends only on intrinsic geometric properties of the spacetime. Such fact is used to obtain a necessary condition for the embedding of aV ₄ intoE ₅.     

Nonlocal vibration of coupled DLGS systems embedded on Visco-Pasternak foundation

In this paper, vibration analysis of the coupled system of double-layered graphene sheets (CS-DLGSs) embedded in a Visco-Pasternak foundation is carried out using the nonlocal elasticity theory of orthotropic plate. The two DLGSs are coupled by an enclosing viscoelastic medium which is simulated as a Visco-Pasternak foundation. Considering the Von Kármán nonlinear strain-displacement-relations, the motion equations are derived using the Hamilton's principle. Differential quadrature method (DQM) is applied to obtain the frequency ratio for various boundary conditions. The detailed parametric study is conducted, focusing on the combined effects of the nonlocal parameter, aspect ratio, graphene sheet's size, boundary conditions and the elastic and viscoelastic medium coefficients on the frequency ratio of CS-DLGSs. In this coupled system, two case of DLGSs vibration are investigated and compared with each other: (1) In-phase vibration (2) Out-of-phase vibration. The results indicate that the frequency ratio of the CS-DLGSs is more than the single-layered graphene sheet (SLGS). The results are in good agreement with the previous researches.     

A numerical model for calculating vibration from a railway tunnel embedded in a full-space

Vibration generated by underground railways transmits to nearby buildings causing annoyance to inhabitants and malfunctioning to sensitive equipment. Vibration can be isolated through countermeasures by reducing the stiffness of railpads, using floating-slab tracks and/or supporting buildings on springs. Modelling of vibration from underground railways has recently gained more importance on account of the need to evaluate accurately the performance of vibration countermeasures before these are implemented.This paper develops an existing model, reported by Forrest and Hunt, for calculating vibration from underground railways. The model, known as the Pipe-in-Pipe model, has been developed in this paper to account for anti-symmetrical inputs and therefore to model tangential forces at the tunnel wall. Moreover, three different arrangements of supports are considered for floating-slab tracks, one which can be used to model directly-fixed slabs. The paper also investigates the wave-guided solution of the track, the tunnel, the surrounding soil and the coupled system. It is shown that the dynamics of the track have significant effect on the results calculated in the wavenumber-frequency domain and therefore an important role on controlling vibration from underground railways.     

超声波显像管振动清洗机的研制

本文介绍一种无需任何清洗液且有别于常规超声波清洗机理的超声波显像管振动清洗机。从理论上分析说明超声波干振动清洗的机理和方法，阐明各超声参量的选取标准和超声振动系统中应注意的问题。     

Encryption test of pseudo-aleatory messages embedded on chaotic laser signals: An information theory approach

In this Letter, we make use of two information-theory based indicators to measure the goodness of two encryption schemes commonly used within the context of chaotic communications. In particular, we have shown that the computation of the normalized Shannon entropy and the MPR-Statistical Complexity measure [M.T. Martín, A. Plastino, O.A. Rosso, Phys. Lett. A 311 (2003) 126, P.W. Lamberti, M.T. Martín, A. Plastino, O.A. Rosso, Physica A 334 (2004) 119] for different chaotic laser signals can lead to statistically significant criteria to assess the quality of several encryption techniques. The proposed measures allow, in some cases, to detect the presence of a message embedded within a chaotic carrier. They also reveal that the Chaos Modulation scheme is more reliable from the statistical point of view, when compared with the Chaos Shift Keying.     

Application of hysteresis functions in vibration problems

In the paper, the notion of the hysteresis function introduced by the author is developed further and applied in some vibration problems for hysteretic materials. The stress–strain relation is built on the basis of well-known extended Masing's rules in which the scaled backbone curve used in the second rule is replaced by a more general function called the hysteresis function. This modification allows us to regulate the dependence of the damping ratio on the strain amplitude in the process of cycle deforming of a material with further extending to arbitrary deformation processes. The three cases of hysteretic systems are considered: the system with limited stress when strain increases without bound, the system with linear backbone curve, and the system with the backbone curve having increasing stiffness for increasing strain. For a number of dynamic examples, a comparison of different hysteresis functions is carried out.