Low-loss chip-scale programmable silicon photonic processor

Chip-scale programmable optical signal processors are often used to flexibly manipulate the optical signals for satisfying the demands in various applications, such as lidar, radar, and artificial intelligence. Silicon photonics has unique advantages of ultra-high integration density as well as CMOS compatibility, and thus makes it possible to develop large-scale programmable optical signal processors. The challenge is the high silicon waveguides propagation losses and the high calibration complexity for all tuning elements due to the random phase errors. In this paper, we propose and demonstrate a programmable silicon photonic processor for the first time by introducing low-loss multimode photonic waveguide spirals and low-random-phase-error Mach-Zehnder switches. The present chip-scale programmable silicon photonic processor comprises a 1×4 variable power splitter based on cascaded Mach-Zehnder couplers (MZCs), four Ge/Si photodetectors, four channels of thermally-tunable optical delaylines. Each channel consists of a continuously-tuning phase shifter based on a waveguide spiral with a micro-heater and a digitally-tuning delayline realized with cascaded waveguide-spiral delaylines and MZSs for 5.68 ps time-delay step. Particularly, these waveguide spirals used here are designed to be as wide as 2 µm, enabling an ultralow propagation loss of 0.28 dB/cm. Meanwhile, these MZCs and MZSs are designed with 2-µm-wide arm waveguides, and thus the random phase errors in the MZC/MZS arms are negligible, in which case the calibration for these MZSs/MZCs becomes easy and furthermore the power consumption for compensating the phase errors can be reduced greatly. Finally, this programmable silicon photonic processor is demonstrated successfully to verify a number of distinctively different functionalities, including tunable time-delay, microwave photonic beamforming, arbitrary optical signal filtering, and arbitrary waveform generation

Artificial intelligence : A powerful paradigm for scientific research

Y Artificial intelligence (AI) coupled with promising machine learning (ML) techniques well known from computer science is broadly affecting many aspects of various fields including science and technology, industry, and even our day-to-day life. The ML techniques have been developed to analyze high-throughput data with a view to obtaining useful insights, categorizing, predicting, and making evidence-based decisions in novel ways, which will promote the growth of novel applications and fuel the sustainable booming of AI. This paper undertakes a comprehensive survey on the development and application of AI in different aspects of fundamental sciences, including information science, mathematics, medical science, materials science, geoscience, life science, physics, and chemistry. The challenges that each discipline of science meets, and the potentials of AI techniques to handle these challenges, are discussed in detail. Moreover, we shed light on new research trends entailing the integration of AI into each scientific discipline. The aim of this paper is to provide a broad research guideline on fundamental sciences with potential infusion of AI, to help motivate researchers to deeply understand the state-of-the-art applications of AI-based fundamental sciences, and thereby to help promote the continuous development of these fundamental sciences.Peer reviewe

Lyapunov Direct Method for Nonlinear Hadamard-Type Fractional Order Systems

In this paper, a rigorous Lyapunov direct method (LDM) is proposed to analyze the stability of fractional non-linear systems involving Hadamard or Caputo–Hadamard derivatives. Based on the characteristics of Hadamard-type calculus, several new inequalities are derived for different definitions. By means of the developed inequalities and modified Laplace transform, the sufficient conditions can be derived to guarantee the Hadamard–Mittag–Leffler (HML) stability of the systems. Lastly, two illustrative examples are given to show the effectiveness of our proposed results

Synchronization of generalized fractional complex networks with partial subchannel losses

This article focuses on the synchronization problem for two classes of complex networks with subchannel losses and generalized fractional derivatives. Initially, a new stability theorem for generalized fractional nonlinear system is formulated using the properties of generalized fractional calculus and the generalized Laplace transform. This result is also true for classical fractional cases. Subsequently, synchronization criteria for the generalized fractional complex networks are attained by the proposed stability theorem and the state layered method. Lastly, two numerical examples with some new kernel functions are given to validate the synchronization results

NONLINEAR BEHAVIOR OF A DISC-SHAFT ROTATING SYSTEM WITH A TRANSVERSE CRACK

ABSTRACT This research intends to investigate the nonlinear behavior of a rotating system with a cracked shaft mounted with a disc. Effects of the geometric nonlinearity, the masses of the shaft and disc and the viscoelastic supports of the rotating system on the motion of the system are studied. The characteristics of the system, such as bifurcations, periodic, quasiperiodic and chaotic behavior are evaluated. Effects of crack depth and rotating speed on the nonlinear behavior of the system are also investigated

Evaluation of electrode-sample contact impedance under different curing humidity conditions during measurement of AC impedance of cement-based materials

Abstract In this study, a simple method was proposed to calculate electrode-sample contact impedance in the cases of two-point and four-point measurements. The results indicated that when using the saturated calcium hydroxide solution (SCH) as conductive medium, the contact impedance in the four-point measurement is negligible for the impedance range of cement-based materials. The SCH can be used as a reference for correction of the contact impedance. A reasonable combination of curing humidity and different conductive media is recommended for the two-point measurement, which is suitable for testing the ACIS of cement-based materials. In a case of contact impedance not being precisely known, it is highly recommended that a four-point measurement with two different ratios of the length of the sample and the center spacing of the voltage electrodes (L/a) should be conducted to evaluate the effect of the contact impedance following the procedure proposed in this study

Nonlinear behavior and characterization of a piezoelectric laminated microbeam system

Fujian Provincial Education Department [JK2010054]; Xiamen Department of Science and Technology [3502Z20103042]; Xiamen University of Technology [YKJ10038R]; Natural Sciences and Engineering Research Council of Canada (NSERC); National Natural Science Foundation of China [11272270]A methodology of analyzing and characterizing the responses of a piezoelectric laminated microbeam system actuated by AC and DC voltages is developed in this research. The present development is based on the piezoelectric theory, Euler-Bernoulli hypothesis, and a newly developed periodicity-ratio (P-R) approach. The electric excitation loading on the beam is considered to be generated by AC and DC interactions. The control voltage of the piezoelectric layer and the geometric nonlinearity of the beam are also taken into account. The analysis of the nonlinear motion trend of the beam system with multiple parameters is carried out with the employment of the P-R criterion. The findings of the research are significant for the design of microbeam systems and micro-structures. (C) 2012 Elsevier B.V. All rights reserved

Random dynamic responses of solar array under thermal-structural coupling based on the isogeometric analysis

The spacecraft experiences changes of light region periodically and will be seriously affected by the thermal stress caused by the solar radiation. Based on the isogeometric analysis, the random dynamic responses of solar array with random field parameters under thermal-structural coupling are addressed. Firstly, the heat conduction differential equation and vibration differential equation of the solar array are obtained based on the geometric model constructed with non-uniform rational B-spline. The differential equations under thermal-structural coupling are then solved by using Newmark-β method to obtain the structural temperature field and the random dynamic responses. Finally, the influences of different random field parameters on structural dynamic response are investigated. [Figure not available: see fulltext.