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A frequency synthesizer is a key component of radars and plays an important role in radar radio frequency transceiver systems. In this study, a digital twin (DT) model of the virtual entity of a frequency synthesizer is proposed to perform thermal analysis. First, the virtual entity of the DT model is established according to the physical entity of the frequency synthesizer. Then, based on the designed DT model of the virtual entity of the frequency synthesizer, the temperature distribution of the model and cooling channel is analyzed, and the temperature distribution of the key components is obtained. Finally, using the results from the DT virtual entity model, a frequency synthesizer temperature prediction method based on a stochastic configuration network (SCN) algorithm is proposed. In the test phase, the characteristic and virtual temperature vectors are used as the input and output of the SCN training set, respectively. Then, 10 different sets of inputs are selected to obtain 10 sets of simulated temperatures and SCN predicted temperatures. The results indicate that the SCN algorithm based on the DT frequency synthesizer can accurately predict the temperature of the physical frequency synthesizer. The thermal analysis of the frequency synthesizer based on the DT provides accurate solutions and reduces the time required by physical components to adjust to high temperatures. [ABSTRACT FROM AUTHOR]

This paper develops and analyzes a theoretical model for flexural vibrations of microbeams in flow with clamped–clamped ends. Based on a modified couple stress theory and the Hamilton’s principle, the governing equations for three-dimensional vibration of a curved microbeam are derived with the consideration of the fluid force induced by external flow. Meanwhile, as a special case, the reduced equation for a straight microbeam in flow is obtained. This new theoretical model contains a material length scale parameter that can capture the size effect. The differential quadrature method (DQM) is introduced to formulate the discrete forms of the governing equations. Based on the numerical calculations, the effects of several system parameters, i.e. the open angle, the characteristic size of the microbeam and the flow velocity, on the natural frequencies and stability of the system are discussed. The results show that, with a sufficiently high flow velocity, the static buckling instability may occur for both curved and straight microbeams in flow, which should be considered in the design and applications. Furthermore, the size effect on the vibration properties is significant when the characteristic size of the microbeam is comparable to the internal material length scale parameter. [ABSTRACT FROM AUTHOR]

In this paper, a nonlinear theoretical model for three-dimensional vibration analysis of curved microtubes conveying fluid with clamped-clamped ends is developed and analyzed based on a modified couple stress theory and the Hamilton's principle. This new theoretical model contains a material length scale parameter that can capture the size effect. In-plane and out-of-plane bending motions, axial motion and twist angle of the microtube are considered in the proposed model. The Lagrange nonlinear axial strain is adopted to obtain the static deformation induced by internal fluid flow. The derived equations of motion are discretized through the Galerkin method. Linearized equations around the static deformation are obtained from the discretized equations, and then the evolution of in-plane and out-of-plane natural frequencies for the curved microtube with various values of flow velocity and material length scale parameter is investigated. The results show that size effect on the vibration properties is significant when the characteristic size of the microtube is comparable to the internal material length scale parameter, and no instabilities are possible for curved microtubes if the nonlinear axial deformation is considered. Therefore, both the size effect and the axial nonlinearity have to be incorporated in the design of curved microscale beam/tube devices and systems. [ABSTRACT FROM AUTHOR]

Abstract: This study considers probabilistic fuzzy systems constructed using Mamdani probabilistic fuzzy rules. As a generalisation of deterministic fuzzy systems, Mamdani probabilistic fuzzy systems better model practical complex systems involving uncertainty because they combine the interpretability of fuzzy systems with the statistical properties of probabilistic systems. Using probabilistic fuzzy rules, both probabilistic uncertainty and linguistic ambiguity are handled simultaneously with a single framework. Considering that the information available often consists of a training set of input–output data pairs, a general method for generating Mamdani probabilistic fuzzy rule bases from numerical data pairs is presented. A fuzzy reasoning method is used on the generated probabilistic fuzzy rule base to derive a map leading from the input space to the output space, and a probabilistic fuzzy system is constructed. We use this probabilistic fuzzy modelling method for nonlinear regression analysis. The effectiveness of the proposed method is demonstrated by a comparison with similar regression techniques. [Copyright &y& Elsevier]

It is well known that Fuglede's conjecture gives a connection between the spectrality and geometrical tiling property. In this paper, we consider a class of planar self-affine sets T , where T is generated by an expanding matrix M ∈ M 2 (Z) with | det (M) | = 4 and D = { (0 , 0) t , (1 , 0) t , (0 , 1) t , (− 1 , − 1) t }. We show that T is a spectral set if and only if T is a translational tile. In particular, if T is a spectral set, then Z 2 is the unique spectrum of T that contains 0 , so it is a tiling set of T by dual criteria. [ABSTRACT FROM AUTHOR]

Reports on the initiative of Zhang Xiaojian, Vice Minister of Labor and Social Security in creating of job opportunities for unemployed people in China. Reemployment of laid-off workers; Diversion of rural surplus laborers to non-agricultural sector; Importance of job training to promote employment and reemployment. INSET: Eight Factors Affect Employment..

In order to provide adequate protection for astronautic memory against single event upsets, a constructing rule of parity check matrix of SEC-DED-DAEC (Single Error Correction Double Error Detection and Double Adjacent Error Correction) codes by improving and optimizing conventional SEC-DED (Single Error Correction-Double Error Detection) codes is proposed in this paper. Through both properly increasing the weights of column vectors and changing the order of column vectors, new SEC-DED-DAEC codes with low error code rate are proposed. The experiment results reveal that redundancy overhead of the proposed scheme is the same as that of conventional SEC-DED codes while its error code rate is lower than the best known SEC-DED-DAEC codes. [ABSTRACT FROM AUTHOR]