A sign-function receiving scheme for sine signals enhanced by stochastic resonance

To address the problem that it is difficult to detect an intermediate frequency (IF) signal at the receiving end of a communication system under extremely low signal-to-noise ratio (SNR) conditions, we propose a stochastic resonance (SR)-enhanced sine-signal detection method based on the sign function. By analyzing the SR mechanism of the sine signal and combining it with the characteristics of a dual-sequence frequency-hopping (DSFH) receiver, a periodic stationary solution of the Fokker-Planck equation (FPE) with a time parameter is obtained. The extreme point of the sine signal is selected as the decision time, and the force law of the electromagnetic particles is analyzed. A receiving structure based on the sign function is proposed to maximize the output difference of the system, and the value condition of the sign function is determined. In order to further improve the detection performance, in combination with the central-limit theorem, the sampling points are averaged N times, and the signal-detection problem is transformed into a hypothesis-testing problem under a Gaussian distribution. The theoretical analysis and simulation experiment results confirm that when N is 100 and the SNR is greater than 20 dB, the bit-error ratio (BER) is less than 1.5×10^-2 under conditions in which the signal conforms to the optimal SR parameters.     

Phase Modulating of Cu–Ni Nanowires Enables Active and Stable Electrocatalysts for the Methanol Oxidation Reaction

The design and development of non-noble metal alternatives with superior performance and promising long-term stability that is comparable or even better than those of noble-metal-based catalysts is a significant challenge. Here, we report the thermal-induced phase engineering of non-noble-metal-based nanowires with superior electrochemical activity and stability for the methanol oxidation reaction (MOR) under alkaline conditions. The optimized Cu–Ni nanowires deliver an unprecedented mass activity of 425 mA mg⁻¹, which is 4.3 times higher than that of the untreated one. Detailed catalytic investigations show that the enhanced performance is due to the large active area, the increased number of active sites (NiOOH), and fast methanol electrooxidation kinetics. In addition, the generated hollow feature in the nanowires provides a unique void space to release the volume expansion, where the activity can be maintained for 5 h without a distinct activity decay. The present work emphasizes the importance of precisely phase modulating of nanomaterials for the design of non-noble metal electrocatalysts towards the MOR, which opens up a new pathway for the design of cost-effective electrocatalysts with promising activity and long-term stability.     

Sulfur-Containing Bent N-Heteroacenes

A series of novel sulfur-containing bent N-heteroacenes were constructed and characterized by NMR and UV/Vis spectroscopy, cyclic voltammetry, and single-crystal X-ray diffraction. By introducing sulfur-containing groups (thio, sulfinyl, and sulfonyl) into bent azaacenes, their electronic delocalization was improved and frontier energy levels were modulated. The target products displayed tunable optical and electronic properties through altering the valence of sulfur and fused length of the azaacenes. For the first time, typical products were utilized as organic field effect transistor materials, affording promising results.     

h-BN型超晶格等离子体光子晶体能带特性研究

六方氮化硼(h-BN)晶格结构是一种类六方对称复式超晶格结构。具有h-BN晶格构型的光子晶体以其宽光子带隙特点受到国内外学者的广泛关注。本文利用不同尺度低压气体放电管与Al₂O₃介质棒周期性排列，构建了新型h-BN型超晶格等离子体光子晶体，实现其空间结构和等离子体参数的动态调控。利用微波透射谱对比研究了h-BN型超晶格与简单三角晶格等离子体光子晶体禁带位置、宽度和数目。分析了放电电流、介质棒阵列数对不同频段光子带隙的影响，以及电磁波入射角度对电磁传输特性的影响。结果表明：等离子体的引入不仅能够形成新的光子带隙，而且可以选择性地使部分禁带位置发生移动；相对于简单三角晶格，h-BN型超晶格等离子体光子晶体呈现出更多光子带隙；Al₂O₃介质棒阵列数对等离子体光子晶体禁带位置、宽度和数目均具有重要影响。电磁波入射角度变化越大，电磁传输特性差别越显著，透射谱相关性越差。本文所设计的新型h-BN型超晶格等离子体光子晶体为制作可调谐光子晶体提供了新的思路，在微波和太赫兹波控制领域具有潜在应用价值。     

On intensities of perturbed random measures on Hausdorff spaces

Abstract

This article studies classes of random measures on topological spaces perturbed by stochastic processes (a.k.a. modulated random measures). We render a rigorous construction of the stochastic integral of functions of two variables and showed that such an integral is a random measure. We establish a new Campbell-type formula that, along with a rigorous construction of modulation, leads to the intensity of a modulated random measure. Mathematical formalism of integral-driven random measures and their stochastic intensities find numerous applications in stochastic models, physics, astrophysics, and finance that we discuss throughout the article.     

Direct modulation and optical confinement factor modulation of semiconductor lasers

Abstract

A method for modulation of semiconductor lasers is demonstrated. The method is based on the modulation of the optical confinement factor. Using this method an enhanced—3-dB bandwidth is observed in agreement with the small signal rate equation analysis. A modulation response that drops at high frequencies slower than the conventional direct current modulation response is achieved. This supports the theoretical predictions, showing an intrinsic 1/f decay rate for the optical confinement factor modulation scheme versus an intrinsic 1/f² decay for direct modulation.     

A Novel Approach to All-Optical Generation of Ultra-Wideband Signals

Abstract

The generation of ultra-wideband signals in the optical domain is highly desirable for ultra-wideband-over-fiber systems, which has recently become a topic of interest. In this article, a novel and simple approach to achieve all-optical generation of ultra-wideband signals is proposed, which is based on delaying and superimposing optical Gaussian pulses with opposite polarities. The proposed system is capable of generating both ultra-wideband monocycle and doublet pulses, and the polarity of the generated ultra-wideband monocycle pulses can be fast-switched to implement pulse polarity modulation with the required bit pattern. A model to describe the proposed system is developed, and the generation of ultra-wideband signals is demonstrated with simulations and a proof-of-concept experiment.     

Die Modulationsübertragungsfunktion von 3″ - und 5″-Kollimator-Detektor-Systemen beim Scanner

Nach Erläuterung der Modulationsüvbertragugsfunktion, einer wichtigen Kenngröβe eines szintigraphischen. Der Übertragungssystems, wird mit ihrer Hilfe ds Auflösungsvermögen von 3″ - und 5″ -Kollimator-Detektor-Systemen verglichen. Die Übertragungsfunktionen werden aus Linienverbreiterungsfunktionen ermittelt. Es wird der Verlauf der Modulationsübertragungs funktionen einzelner Kollimatoren der 3″ - und 5″-Systeme in Abhängigkeit vom Quellen-Kollimator-Abstand diskutiert. Ferner wird die λ/2-Regel benutzt, um Aussagen über die darstellbaren Detailgröβen zu machen, und schlieβlich wird die äquivalente Bandbreite für die einzelnen Modulationsübertragungsfunktionen angegeben.     

Phenol-triggered supramolecular transformation of titanium–oxo cluster based coordination capsules

Supramolecular transformations of coordination cage or capsule have received much attention recently,which help elucidate this natural self-assembly behavior in biological systems.The current study describes the first supramolecular transformation of titanium-o rganic coordination capsule triggered by phenol(and H_3 PO_3).The structural alterations are accompanied by the reconstruction of 5-coordinated Ti centers to 6-coordinated ones.Meanwhile,different amounts of encapsulated phenol guest molecules can be identified,dependent on the sizes of the obtained cavities.In addition,they display much better visible light absorption and air stability than the isopropanol stabilized ones.     

A new class of conformable spectral observers for signal reconstruction

In this work, the design of spectral observers for signal reconstruction based on Kalman filters is performed and evaluated. The conformable derivative and the beta‐derivative were used to design the Kalman filters. Both derivatives satisfy the same formulas of the classical derivation, eg, the chain rule. The derivative order, the Ricatti equation parameters, and the observers tuning parameters were optimized using an optimization algorithm based on the bat's echolocation behavior (Bat algorithm). The simulation results showed the advantages of using the proposed observers for the signal reconstruction.