反馈型细胞神经网络稳定性研究

一个含有MN个细胞的反馈型细胞神经网络可以等效成一个非反馈连接网络;这一非反馈连接网络含有2MN个细胞、具有似镜象结构邻域和空间可变权重模板、输入权重模板为零。本文给出了反馈型细胞神经网络的稳定性定理,以及在似镜象结构邻域下的变换形式。     

Crosstalk suppression in networked resistive sensor arrays using virtual ground technique

In 2D resistive sensor arrays, the interconnections are reduced considerably by sharing rows and columns among various sensor elements in such a way that one end of each sensor is connected to a row node and other end connected to a column node. This scheme results in total N?+?M interconnections for N?×?M array of sensors. Thus, it simplifies the interconnect complexity but suffers from the crosstalk problem among its elements. We experimentally demonstrate that this problem can be overcome by putting all the row nodes at virtually equal potential using virtual ground of high gain operational amplifiers in negative feedback. Although it requires large number of opamps, it solves the crosstalk problem to a large extent. Additionally, we get the response of all the sensors lying in a column simultaneously, resulting in a faster scanning capability. By performing lock-in-amplifier based measurements on a light dependent resistor at a randomly selected location in a 4?×?4 array of otherwise fixed valued resistors, we have shown that the technique can provide 86?dB crosstalk suppression even with a simple opamp. Finally, we demonstrate the circuit implementation of this technique for a 16?×?16 imaging array of light dependent resistors.     

DOA Estimation for Multiple Sparse Sources with Arbitrarily Arranged Multiple Sensors

This paper proposes a method for estimating the direction of arrival (DOA) of multiple source signals for an underdetermined situation, where the number of sources N exceeds the number of sensors M (M < N). Some DOA estimation methods have already been proposed for underdetermined cases. However, since most of them restrict their microphone array arrangements, their DOA estimation ability is limited to a 2-dimensional plane. To deal with an underdetermined case where sources are distributed arbitrarily, we propose a method that can employ a 2- or 3-dimensional sensor array. Our new method employs the source sparseness assumption to handle an underdetermined case. Our formulation with the sensor coordinate vectors allows us to employ arbitrarily arranged sensors easily. We obtained promising experimental results for 2-dimensionally distributed sensors and sources 3×4, 3×5 (#sensors × #speech sources), and for 3-dimensional case with 4×5 in a room (reverberation time (RT) of 120 ms). We also investigate the DOA estimation performance under several reverberant conditions.     

Analysis of the structure of a terahertz-band 2D array with sensors on the edge of a superconductor transition

Film detectors on the edge of a Ti or Mo/Cu (T _c ≈ 0.4 K) superconductor transition are included in an N × M 2D array of planar polarization-separated antennas. The detectors are simultaneously sensors and absorbers of the total electric power from an antenna and bias circuits. The detectors are heat-insulated because of weak electron-phonon interaction with the substrate and because of the effect of the Andreev reflection of electrons in Nb electrodes. Readout based on the projection method necessitates only N + M channels in the case when the signal is continuously accumulated for all N × M detectors. Simulation of a 3 × 3 2D array at a frequency of 600 GHz shows that the matching band is ～30%.     

Photophysics of Molecular‐Weight‐Induced Losses in Indacenodithienothiophene‐Based Solar Cells

The photovoltaic performance and optoelectronic properties of a donor–acceptor copolymer are reported based on indacenodithienothiophene (IDTT) and 2,3‐bis(3‐(octyloxy)phenyl)quinoxaline moieties (PIDTTQ) as a function of the number‐average molecular weight (M_n). Current–voltage measurements and photoinduced charge carrier extraction by linear increasing voltage (photo‐CELIV) reveal improved charge generation and charge transport properties in these high band gap systems with increasing M_n, while polymers with low molecular weight suffer from diminished charge carrier extraction because of low mobility–lifetime (μτ) product. By combining Fourier‐transform photocurrent spectroscopy (FTPS) with electroluminscence spectroscopy, it is demonstrate that increasing M_n reduces the nonradiative recombination losses. Solar cells based on PIDTTQ with M_n = 58 kD feature a power conversion efficiency of 6.0% and a charge carrier mobility of 2.1 × 10^?4 cm² V^?1 s^?1 when doctor bladed in air, without the need for thermal treatment. This study exhibits the strong correlations between polymer fractionation and its optoelectronics characteristics, which informs the polymer design rules toward highly efficient organic solar cells.     

A wide range,high yield and good performance pHEMT switch for MMIC phase shifter

A low-cost method with high yield and good performance is presented by pHEMTs (pseudomorphic high electron mobility transistors) to be used in phase shifter switches. In this method, the capacitor in “off” mode (C_off) of transistor is reduced, without variation of the transistor structure. The transistor structure in switch mode can be optimised. This method increases the transistor isolation in turn “off” mode, while there is no change in resistance of the transistor in “on” mode (R_on). Transistor dimension is determined in turn “off” mode (V_g = ?4.5 V) and standard form of 4 × 75 μm. So, in this method, insertion loss will be reduced without a perceptible change in transistor dimension. Thus, design and fabrication capability of some circuits such as phase shifters, antenna switches, SPDT (single port double throw) – without any change in technology – are increasing. In this paper, post layout and measurement result for a sample block of phase shifter are shown.     

Multi-scroll hyperchaotic system based on colpitts model and its circuit implementation

Based on the framework of Colpitts oscillator, a four-dimensional multi-scroll hyperchaotic system is proposed, which generates (2M+1)×(2N+1)-scroll chaotic and hyperchaotic attractors. The key strategy is to increase the number of index-2 equilibrium points by introducing two unit saw-tooth functions to extend and modify the Colpitts oscillator model. By using bifurcation diagram and phase portrait, the dynamical characteristics of the multi-scroll hyperchaotic system are briefly studied. Moreover, micro-controller based circuit realization is introduced and the experimental results demonstrate that 7×5-scroll chaotic and hyperchaotic attractors can be obtained in the digital circuit.     

Large‐Size Bulk and Thin‐Film Stilbazolium‐Salt Single Crystals for Nonlinear Optics and THz Generation

We present new stilbazolium salt DSTMS (4‐N,N‐dimethylamino‐4′‐N′‐methyl‐stilbazolium 2,4,6‐trimethylbenzenesulfonate) with both high second‐order nonlinear optical properties and very favorable crystal growth characteristics. We are able to obtain very large area bulk single crystals of more than 3 × 3 × 0.2 cm³ with a high optical quality without using seed crystals by using low‐temperature solution growth. We also demonstrate the growth of single crystalline thin films of DSTMS with an area of up to 6 × 5 mm² and a thickness between 5–30 μm. Nonlinear optical measurements reveal that DSTMS possesses large nonlinear optical susceptibilities with χ₁₁₁⁽²⁾ = (430 ± 40) pm V^–1 at 1.9 μm. Highly efficient generation of broadband THz waves with THz electric field strengths of more than 4 kV cm^–1 using 160 fs laser pump pulses at a wavelength λ = 1.45 μm and DSTMS crystals has been demonstrated.     

Quantification of Grafting Densities Achieved via Modular “Grafting‐to” Approaches onto Divinylbenzene Microspheres

The surface modification of divinylbenzene (DVB)‐based microspheres is performed via a combination of reversible addition fragmentation chain transfer (RAFT) polymerization and rapid hetero‐Diels–Alder (HDA) chemistry with the aim of quantifying the grafting densities achieved using this “grafting‐to” method. Two variants of the RAFT‐HDA concept are employed to achieve the functionalization of the microspheres. In the first approach, the microspheres are functionalized with a highly reactive diene, i.e., cyclopentadiene, and are subsequently reacted with polystyrene chains (number‐averaged molecular weight, M_n = 4200 g mol^?1; polydispersity index, PDI = 1.12.) that carry a thiocarbonyl moiety functioning as a dienophile. The functionalization of the microspheres is achieved rapidly under ambient conditions, without the aid of an external catalyst. The surface grafting densities obtained are close to 1.2 × 10²⁰ chains per gram of microspheres. In the second approach, the functionalization proceeds via the double bonds inherently available on the microspheres, which are reacted with poly(isobornyl acrylate) chains carrying a highly dienophilic thiocarbonyl functionality; two molecular weights (M_n = 6000 g mol^?1, PDI = 1.25; M_n = 26 000 g mol^?1, PDI = 1.26) are used. Due to the less reactive nature of the dienes in the second approach, functionalization is carried out at elevated temperatures (T = 60 °C) yet in the absence of a catalyst. In this case the surface grafting density is close to 7 chains nm^?2 for M_n = 6000 g mol^?1 and 4 chains nm^?2 for M_n = 26 000 g mol^?1, or 2.82 × 10¹⁹ and 1.38 × 10¹⁹ chains g^?1, respectively. The characterization of the microspheres at various functionalization stages is performed via elemental analysis for the quantification of the grafting densities and attenuated total reflectance (ATR) IR spectroscopy as well as confocal microscopy for the analysis of the surface chemistry.     

Solid‐Phase Synthesis of Molecularly Imprinted Polymer Nanoparticles with a Reusable Template–“Plastic Antibodies”

Molecularly imprinted polymers (MIPs) are generic alternatives to antibodies in sensors, diagnostics, and separations. To displace biomolecules without radical changes in infrastructure in device manufacture, MIPs should share their characteristics (solubility, size, specificity and affinity, localized binding domain) whilst maintaining the advantages of MIPs (low‐cost, short development time, and high stability) hence the interest in MIP nanoparticles. Herein, a reusable solid‐phase template approach is reported (fully compatible with automation) for the synthesis of MIP nanoparticles and their precise manufacture using a prototype automated UV photochemical reactor. Batches of nanoparticles (30–400 nm) with narrow size distributions imprinted with: melamine (d = 60 nm, K_d = 6.3 × 10^?8 M ), vancomycin (d = 250 nm, K_d = 3.4 × 10^?9 M ), a peptide (d = 350 nm, K_d = 4.8 × 10^?8 M ) and proteins have been produced. The instrument uses a column packed with glass beads, bearing the template. Process parameters are under computer control, requiring minimal manual intervention. For the first time, the reliable re‐use of molecular templates is demonstrated in the synthesis of MIPs (≥30 batches of nanoMIPs without loss of performance). NanoMIPs are produced template‐free and the solid‐phase acts both as template and affinity separation medium.     

Bifacial potential of single‐ and double‐sided collecting silicon solar cells

Bifacial applications are a promising way to increase the performance of photovoltaic systems. Two silicon solar cell concepts suitable for bifacial operation are the passivated emitter, rear totally diffused (PERT) and the both sides collecting and contacted (BOSCO) cell concepts. This work investigates the bifacial potential of these concepts by means of in‐depth numerical device simulation and experiment with a focus on the impact of varying material quality. It is shown that the PERT cell concept (representing a structure with front‐side emitter only) requires high‐minority‐carrier‐diffusion‐length substrates with L_bulk > 3 × W (with cell thickness W) to exploit its bifacial potential, while the BOSCO cell (representing a structure with double‐sided emitter) can already utilise its bifacial potential on substrates with significantly lower diffusion lengths down to L_bulk ≈ 0.5 × W. Experimentally, BOSCO cells with and without activated rear‐side emitter are compared. For rear‐side illumination, the activated rear‐side emitter is measured to increase internal quantum efficiency at wavelengths λ < 850 nm by up to 45%_abs (factor of 9) and 30%_abs (factor of 2) for cells processed on p‐type multicrystalline silicon substrates with L_bulk ≈ 0.3 × W and L_bulk ≈ 2.6 × W, respectively. For PERT cells processed on n‐type Czochralski‐grown silicon substrates, an according increase in internal quantum efficiency for rear‐side illumination of more than 20%_abs (factor of 1.3) is measured when changing from a substrate with L_bulk ≈ 3.0 to 10.0 × W. The performed simulations and experiments demonstrate that the BOSCO cell concept is a promising candidate to successfully exploit bifacial gain also on low‐ to medium‐diffusion‐length substrates such as p‐type multicrystalline silicon, while PERT cells require a high‐diffusion‐length substrate to utilise their bifacial potential. Furthermore, the BOSCO cell concept is shown to be a promising option to achieve highest output power densities, even when using lower quality and therefore possibly more cost‐effective silicon substrates. Copyright © 2016 John Wiley & Sons, Ltd.     

An efficient and lightweight multi‐scroll chaos‐based hardware solution for protecting fingerprint biometric templates

This paper presents a new efficient and lightweight approach for enhancing the security of biometric models, namely, fingerprint templates, against possible attacks. The proposed design is based on Vernam stream cipher in which the key generator is designed in the hardware manner. The designed cryptosystem consists of using multi‐scroll chaotic system that is characterized by a large key space and can be generated N×N grid multi‐scroll attractors, with a good behavior of chaotic dynamic. The hardware approach is carried out through describing Euler method by VHDL. Field‐programmable gate array (FPGA) experimental results validate the developed architecture while still providing a good compromise between hardware resources and performance. Indeed, security analysis also shows that the designed encryption algorithm is robust against statistical, brute force, and entropy attacks. Therefore, it can be considered as a lightweight security solution, which could be very useful in many embedded applications namely securing biometric authentication systems.     

Zn-doping in OMVPE Grown lnP:Zn/lnGaAs/lnPp-i-n double heterojunctlons with lnGaAs:Zn contacting layers

We report on the control of zinc in organometallic vapor phase epitaxial (OMVPE) grown InP:Zn/InGaAs/InPp- i- n double heterojunctions with InGaAs:Zn contacting layers. As a function of diethylzinc (DEZn) flow, we measure net acceptor concentrations for the InP:Zn p-layer in the range 2 × 10¹⁷≤N _a−N _d≤ 9 × 10¹⁷ cm⁻³. A 435°C post-growth anneal for 300 sec increases the net acceptor concentrations by a factor of 3.6 − to 6 × 10¹⁷≤N _a−N _d≤ 3 × 10¹⁸ cm⁻³. When the annealed value ofN _a − N_din the InP:Zn layer is 6 × 10¹⁷ cm⁻³ , secondary ion mass spectrometry (SIMS) measurements show abrupt Zn-doping transitions at the heterojunction interfaces. In contrast, when the annealed value ofN _a − N_din the InP:Zn layer is near the saturation value of 3 × 10¹⁸ cm⁻³, SIMS measurements show significant movement of Zn into the nominally undoped InGaAs instrinsic layer. Increasedp-i-n diode capacitance is associated with the Zn movement.     

Design and fabrication of the GaAs integrated optical chip for fiber optical gyroscope

An integrated optical chip for fiber optical gyroscope (FOG) is designed and fabricated on GaAs. To achieve a high modulation efficiency and a small chip size, a deeply etched waveguide structure is employed, and accordingly a multimode interference (MMI) coupler is used as the 1 × 2 power splitter. The size of the chip is about 8.5 mm × 0.5 mm, which is much smaller than that of LiNbO₃-based chips. The experimental results show that the extinction ratio (ER) of the TE mode to the TM mode is over 26 dB and the value of V _π·L of the phase modulators is 18 V · cm. The method to further lower V _π is discussed.     

Effect of the thickness and number of layers on the optical and electrical properties of Cu/ZnO:Ga periodic structures

The optical and electrical properties of multilayered Cu/ZnO:Ga periodic structures with different numbers of periods N are studied in relation to the thickness of the metal and oxide layers. It is established that, as the number of periods is increased, the integrated transmittance of the (Cu/ZnO:Ga) × N structure, in which the thickness of each Cu layer is 9 nm, decreases more slowly than the transmittance of a similar structure, in which the thickness of each metal layer is 5 nm. At the same time, (Cu/ZnO:Ga) × N periodic structures with N = 2?5 exhibit a rather low surface resistivity (5?C2 ??/??).     

光束的二阶矩矩阵和M2因子

基于4×4二阶矩矩阵,对一般光束的M2因子和本征像散a作了研究,得出复杂像散光束、旋转简单像散光束、准直简单像散光束和无像散光束等一些典型光束的M2因子和本征像散的解析公式,并作了分析。研究表明,一般而言,扭曲会引起本征像散的增加,但却不会影响M2因子。     

Spectral efficiency improvement with SISO and SIMO in M‐QAM over millimeter‐wave links

This paper proposes a spectral efficiency improvement technique for millimeter wave (mmWave) links. The proposed technique provides an efficient utilization of the mmWave link capacity. This technique is applied in three cases the single‐input single‐output (SISO), single‐input multiple‐output (SIMO) with the maximal ratio combining and with the equal gain combining. The M‐ary quadrature amplitude modulation scheme is used in our work. The power series expansion is used for deriving closed‐form expressions for bit error rate (BER) performances in all studied cases. The BER closed‐form expressions are confirmed by the numerical solution of the integral equations. The simulation results show that a high spectral efficiency can be accomplished by the proposed technique. As well as the derived expressions closely match with the numerical solution of integration expressions at different values of modulations order the Rician factor. For instance, the spectral efficiency gain achievement is 8 at signal‐to‐noise ratio (SNR) equals 34 dB in the case of SISO system whereas in the case of SIMO system, the same gain is achieved at SNR equals 24 dB. As well as the BER performance is enhanced from 1.188 × 10^?4, 7.112 × 10^?4, 4.164 × 10^?3, and 3.286 × 10^?2 to 8.717 × 10^?16, 1.119 × 10^?12, 1.308 × 10^?9, and 4.905 × 10^?6 for M = 4, 16, 64, and 256, respectively, at SNR equals 30 dB.     

A Magnetoresistance Induced by a Nonzero Berry Phase in GeTe/Sb2Te3 Chalcogenide Superlattices

The chalcogenide alloy Ge–Sb–Te (GST) has not only been used in rewritable digital versatile discs, but also in nonvolatile electrical phase change memory as a key recording material. Although GST has been believed for a long time not to show magnetic properties unless doped with magnetic impurities, it has recently been reported that superlattices (SLs) with the structure [(GeTe)_L(Sb₂Te₃)_M]_N (where L, M, and N are usually integers) have a large magnetoresistance at room temperature for particular combinations of L and M. Here it is reported that when [(GeTe)_L(Sb₂Te₃)_M]_N chalcogenide SL films are thermally annealed at 470 K and cooled down to room temperature under an external magnetic field accompanied by current pulse injections, a large magnetoresistance change (>2500 Ω) is induced. This study shows that the phenomenon has a strong correlation with the GeTe thickness and the periodic structure of the SL films, and that it is induced by the structural phase transition between electrically nonpolar and polar phases in the GeTe layers in the SLs. This study proposes that the relationship between the polar (ferroelectric) phase and the Berry curvature in the SLs is responsible for the magnetoresistance change.     

Teleportation of an arbitrary unknown N -qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers（M 〈 N） is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home- Zeilinger （GHZ） state and N-M non-maximally entangled Einstein-Podolsky-Rosen （EPR） pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.