Interaction of moiré excitons with cavity photons in two-dimensional semiconductor hetero-bilayers

Moiré materials, composed of two single-layer two-dimensional semiconductors, are important because they are good platforms for studying strongly correlated physics. Among them, moiré materials based on transition metal dichalcogenides(TMDs) have been intensively studied. The hetero-bilayer can support moiré interlayer excitons if there is a small twist angle or small lattice constant difference between the TMDs in the hetero-bilayer and form a type-II band alignment. The coupling of moiré inter...     

Review of phonons in moiré superlattices

Moiré patterns in physics are interference fringes produced when a periodic template is stacked on another similar one with different displacement and twist angles. The phonon in two-dimensional(2D) material affected by moiré patterns in the lattice shows various novel physical phenomena, such as frequency shift, different linewidth, and mediation to the superconductivity. This review gives a brief overview of phonons in 2D moiré superlattice. First, we introduce the theory of the moiréphonon mo...     

A pitch-variation moiré fringes method of temporal phase unwrapping profilometry

A method of pitch-variation moiré fringes is proposed to realize the temporal phase unwrapping for three-dimensional profilometry. On the basis of the principle of moiré pattern,we achieve variable spatial frequencies of fringes in a moiré pattern by rotating two gratings. Furthermore a five-point fitting method is used to automatically compute the central position of side-lobe spectrum of the moiré fringes. Finally,a generalized temporal phase unwrapping algorithm is intro-duced to process the three-dimensional reconstruction. The theoretical analysis and experimental results show the validity of the proposed method.     

Moiré heterostructures: highly tunable platforms for quantum simulation and future computing

<正>Moiré heterostructures, where the constituent 2D materials are stacked vertically at a small angle, feature longwavelength interference pattern at the van der Waals interfaces. One typical example is twisted bilayer graphene. In this moiré heterostructure, the emergence of moiré superlattices can effectively reconstruct the energy bands into dispersionless flat bands at a special twisted angle(so-called ‘magic angle’),     

一种采用单信号控制的新型高压高低侧功率器件

Novel high-voltage, high-side and low-side power devices, whose control circuits are referred to as the tub, are proposed and investigated to reduce chip area and improve the reliability of high-voltage integrated circuits. By using the tub circuit to control a branch circuit consisting of a PMOS and a resistor, a pulse signal is generated to control the low-side n-LDMOS after being processed by a low-voltage circuit. Thus, the high-voltage level-shifting circuit is not needed any more, and the parasitic effect of the conventional level-shifting circuit is eliminated. Moreover, the specific on-resistance of the proposed low-side device is reduced by more than 14.3% compared with the conventional one. In the meantime, integrated low-voltage power supplies for the low-voltage circuit and the tub circuit are also proposed. Simulations are performed with MEDICI and SPICE, and the results show that the expectant functions are achieved well.     

REFLECTION AND TRANSMISSION OF HARMONIC WAVES AT A PLANE INTERFACE BETWEEN LINEAR AND NONLINEAR DIELECTRICS

The laws of reflection and transmission of harmonic waves at a plane interface between a linear dielectric and a nonlinear dielectric are carefully analyzed. The exact expressions of the reflective and transmissive fields are derived. The further discussions are made to the fields at the conditions of vertical incidence and phase-matching.     

TRIPLET CIRCULAR HOUGH TRANSFORM FOR CIRCLE DETECTION

A new method,triplet circular Hough transform,is proposed for circle detection in image processing and pattern recognition.In the method,a curve in an image is first detected.Next,a sequence of three points on the curve are selected.a sequence of parameters(a,b,r)corresponding to the three points are calculated by solving the circle equation of the curve,and two 2-D accumulators A(a,b)and R(a,b)are accumulated with 1 and r,respectively,Then the parameters{(a,b,r)}of the circles fitting the curve are determined from A(a,b)and R(a,b) by searching for the local maximum over A(a,b).Because no computation loops over center(a,b) and/or radius r are needed,the method is faster than the basic and directional gradient methods It needs also much smaller memory for accumulation.     

The architecture of a specific chip for RNA secondary structure prediction

The architecture of a BioAccel (internal code) chip for RNA secondary structure prediction is described in the letter. The system is based on a BioBus (internal code), whose distinguishing features are: Two separated control and data channels, and a slave-associated arbitration scheme. Two reference systems based on the AMBA AHB bus and Coreconnect bus are introduced to evaluate the performance of the system. The simulation results are attractive.The average communication bandwidth of the chip is increased at severalfold, and the read and write latencies are reduced about 40 percent.     

Numerical simulation of shock wave phenomena in hydrodynamic model of semiconductor devices

We propose a finite element method to investigate the phenomena of shock wave and to simulate the hydrodynamic model in semiconductor devices . An introduction of this model is discussed first. Then some scaling factors and a relationship between the changing variables are discussed. And then, we use a finite element method (P1-iso-P2 element) to discrete the equations. Some boundary conditions are also discussed. Finally,a sub-micron n+-n-n+ silicon diode and Si MESFET device are simulated and the results are analyzed. Numerical results show that electronic fluids are transonic under some conditions.     

Security, Controllability, Manageability and Survivability in Trustworthy Network

The Internet plays increasingly important roles in everyone’s life; however, the existence of a mismatch between the basic architectural idea beneath the Internet and the emerging requirements for it is becoming more and more obvious. Although the Internet community came up with a consensus that the future network should be trustworthy, the concept of "trustworthy networks" and the ways leading us to a trustworthy network are not yet clear. This research insists that the security, controllability, manageability, and survivability should be basic properties of a trustworthy network. The key ideas and techniques involved in these properties are studied, and recent developments and progresses are surveyed. At the same time, the technical trends and challenges are briefly discussed. The network trustworthiness could and should be eventually achieved.     

Transmission capacity for inhomogeneous overlaid wireless Ad-hoc networks

In the analysis of overlaid wireless Ad-hoc networks, the underlying node distributions are commonly assumed to be two independent homogeneous Poisson point processes. In this paper, by using stochastic geometry tools, a new inhomogeneous overlaid wireless Ad-hoc network model is studied and the outage probability are analyzed. By assuming that primary （PR） network nodes are distributed as a Poisson point process （PPP） and secondary （SR） network nodes are distributed as a Matern cluster processes, an upper and a lower bounds for the transmission capacity of the primary network and that of the secondary network are presented. Simulation results show that the transmission capacity of the PR and SR network will both have a small increment due to the inhomogeneity of the SR network.     

Inversion of roughness profile of heterogeneous fractal surface using Gaussian beam incidence at low grazing angle

As a Gaussian beam is incident upon a rough surface at low grazing angle, the Helmholts scalar wave equation may be replaced by the parabolic approximate equation. As the incident field is known, the scattered field and surface current give the Volterra integral equation. Surface roughness profile can be formulated by the integral equation of the surface currents. These two coupled equations are applied to invert the roughness profile of heterogeneous fractal surface. Using Monte Carlo method, the fractal rough surfaces with a band-limited Weistrass-Manderbrot function are numerically simulated and the scattered fields along a line parallel to the mean surface are solved. The Gaussian beam incidence and scattered fields are used to progressively invert the surface roughness profile. Reconstructed profile and its inverted fractal dimension, roughness variance and correlation length are well matched with the simulated surfaces.     

CONDITIONS FOR FOURTH-ORDER STATIONARITY AND ERGODICITY OF A HARMONIC RANDOM PROCESS

The finite data estimates of the complex fourth-order moments of a signal consisting of random harmonics are analyzed. Conditions for the fourth-order stationarity and ergodicity are obtained. Explicit formulas for the estimation error and its variance, as well as their limiting large sample values are derived. Finally, a special case relevant to cubic phase coupling is considered, and these results are stated for this case, the variance is shown to comprise an ergodic and a nonergodic part.     

PHASE THEORY OF RADIATION PATTERN

The conventional requirements on the antenna are reviewed.The importance of the phase patternof the antenna in modern science and technology is pointed out.Under such a background,the prob-lems concerning the phase characteristic of the radiation pattern and the current distribution of theantenna aperture are attempted to be systematized on the basis of previous works,namely,the phasereference point,the transformation of the radiation patterns corresponding to different phase referencepoints of an antenna,the null level and the phase difference between the adjacent lobes,and the resolu-tion of current distribution of a linear source,are summarized and discussed.The general conditionof the equiphase lobe and the condition of the symmetric lobe of a linear source are proposed andproved theoretically.Some theorems are proposed by induction from the above and the overalldiscussion is termed the phase theory of radiation pattern.     

THE LARGE-SIGNAL DESIGN FOR FET FUNDAMENTAL AND HARMONIC OSCILLATORS

A Large-signal model for GaAs FET is derived based on its small-signal S parame-ters and DC characteristics. The harmonic balance algorithm is applied to analyze and optimizethe FET fundamental and harmonic oscillators, and the values of steady current are obtained.In the solving process, a simplified CAD approach is used to obtain the parameters of matchingnetwork when the output power is maximum. Finally, a fundamental oscillator and a harmonicoscillator of Q-band are fabricated. The measurements show that the theoretical analysis andexperimental results are in good agreement.     

Measurement of air pollutants by differential optical absorption spectroscopy using a Cassegrain telescope with fibers

A differential optical absorption spectroscopy (DOAS) method is presented and used for the air pollutant detection. The novel measurement frame employs a Cassegrain telescope and a combined fiber bundle. The emitting and receiving fibers are bundled together at one port. The common port is placed at the focus of the Cassegrain telescope. The total length of the prototype is reduced to about 1/2 of the traditional one. Air pollutants of SO2, NO2 and O3 are monitored by the prototype, and the concentrations are inverted. Results show that the correlation coefficients are 0.9490, 0.9614 and 0.9301, respectively. And there is a good consistency between the measured results and the reference data.     

Routing and wavelength assignment algorithms based on equivalent networks

In this paper, a Wavelength Division Multiplexing （WDM） network model based on the equivalent networks is described, and wavelength-dependent equivalent arc, equivalent networks, equivalent multicast tree and some other terms are presented. Based on this model and relevant Routing and Wavelength Assignment （RWA） strategy, a unicast RWA algorithm and a multicast RWA algorithm are presented. The wavelength-dependent equivalent arc expresses the schedule of local RWA and the equivalent network expresses the whole topology of WDM optical networks, so the two algorithms are of the flexibility in RWA and the optimization of the whole problem. The theoretic analysis and simulation results show the two algorithms are of the stronger capability and the lower complexity than the other existing algorithms for RWA problem, and the complexity of the two algorithms are only related to the scale of the equivalent networks. Finally, we prove the two algorithms＇ feasibility and the one-by-one corresponding relation between the equivalent multicast tree and original multicast tree, and point out the superiorities and drawbacks of the two algorithms respectively.     

Optical-fiber distributed temperature sensor: design and realization

Through analyzing theoretically the temperature effect of the optical-fiber Raman backscattering, a distributed temperature sensor is designed based on the single-mode fiber. Demodulation methods of temperature transduction are compared, and then the demodulation method using the ratio of the anti-Stokes and the Stokes Raman backscattering intensity is adopted. Both the hardware composition and the software realization of the system are introduced in detail. The experiment shows that the distinguishing ability of the temperature and that of the space are 1℃ and 2 m, respectively, and that the system response time is about 180 s with a sensing range of 5 km and with a temperature measurement range of 0-100℃.     

Experimental Study on Near-IR Nonlinear Optical Waveguide Sensor for Refractive Index of Liquids

To determine the refractive index of liquids in near infrared（lR）, a method is presented by measuring the output angle of the visible Cerenkov-radiation-mode when liquids are placed as the cover on a planar lithium niobate waveguide. The system configuration and the principle of the method are analyzed and some experimental results are given out. Both the experimental result and simulation show that this method is simple, rapid and of sufficient precision.     

Optical-fiber distributed temperature sensor： design and realization

Through analyzing theoretically the temperature effect of the optical-fiber Raman backscattering,a distributed temperature sensor is designed based on the single-mode fiber. Demodulation methods of temperature transduction are compared,and then the demodulation method using the ratio of the anti-Stokes and the Stokes Raman backscattering intensity is adopted. Both the hardware composition and the software realization of the system are introduced in detail. The experiment shows that the distinguishing ability of the temperature and that of the space are 1℃ and 2m,respectively,and that the system response time is about 180 s with a sensing range of 5km and with a temperature measurement range of 0-100℃.