基于直接数字频率合成的远距离散射通信方法

远距离(LoRa)散射通信(BC)不仅成本低、功耗低,而且通信距离远。但现存散射方案的系统组成复杂,且无法应用于实际工程。为此该文提出一种新的LoRa散射通信方法,采用直接数字频率合成(DDS)技术产生频率线性变化的方波作为LoRa散射调制信号,并据此首次展示了基于MCU的LoRa散射通信系统原型样机。实验结果表明,该方法能够在相距208 m的基站和接收端之间的任意位置实现低功耗LoRa散射通信,且兼容现有的商用LoRa射频芯片组。此外,该方法还适用于专用集成电路(ASIC)设计,可使LoRa散射IC有更高的鲁棒性、更低的成本和功耗。     

现代演播室灯光 舞美系统设计要素

本文论述数字摄像设备对灯光设备的新要求,以及数字灯光设备对演播室环境及灯光吊挂系统的新要求;同时提出数字演播室灯光系统设计直具备的新观念。     

pin硅波导在1550 nm波段的光电流雪崩增强效应实验研究

The photocurrent effect in pin silicon waveguides at 1550 nm wavelength is experimentally investigated. The photocurrent is mainly attributed to surface-state absorption,defect-state absorption and/or two-photon absorption.Experimental results show that the photocurrent is enhanced by the avalanche effect.A pin silicon waveguide with an intrinsic region width of 3.4μm and a length of 2000μm achieves a responsivity of 4.6 mA/W and an avalanche multiplication factor of about five.     

一种自循迹小车循迹方案优化系统

自循迹小车沿不同特征的曲线轨道运行,运行轨迹直接决定了小车能否快捷到达目的地.本文以高清摄像头捕获小车运行坐标,再利用LabVIEW根据坐标数组绘制运行轨迹,根据背景差分法对比轨道图和实际小车运行轨迹图,实现快速获得当前曲线特征的轨道对应的PID控制参数.     

宽带数字信道化接收机算法研究与硬件实现

对宽带数字信道化接收机进行了理论研究与硬件实现。该系统模型采用多相滤波结构,使用IFFT算法简化信道化多相滤波器结构与参数,并对各个信道进行下变频产生基带信号以便后续信号识别分析处理,信道化频带划分采用均匀且相邻信道50%交叠的方式。该系统硬件采用A/D转换芯片和FPGA芯片实现,A/D转换芯片完成宽带信号采集,FPGA芯片完成相关算法软件实现。该接收机结构具有设计灵活、实现简单、计算效率高、实时处理能力强、计算量低、FPGA硬件资源少等优点。     

Engineering an Earth‐Abundant Element‐Based Bifunctional Electrocatalyst for Highly Efficient and Durable Overall Water Splitting

The simultaneous and efficient evolution of hydrogen and oxygen with earth‐abundant, highly active, and robust bifunctional electrocatalysts is a significant concern in water splitting. Herein, non‐noble metal‐based Ni–Co–S bifunctional catalysts with tunable stoichiometry and morphology are realized. The engineering of electronic structure and subsequent morphological design synergistically contributes to significantly elevated electrocatalytic performance. Stable overpotentials (η₁₀) of 243 mV (vs reversible hydrogen electrode) for oxygen evolution reaction (OER) and 80 mV for hydrogen evolution reaction (HER), as well as Tafel slopes of 54.9 mV dec^?1 for OER and 58.5 mV dec^?1 for HER, are demonstrated. In addition, density functional theory calculations are performed to determine the optimal electronic structure via the electron density differences to verify the enhanced OER activity is related to the Co top site on the (110) surface. Moreover, the tandem bifunctional NiCo₂S₄ exhibit a required voltage of 1.58 V (J = 10 mA cm^?2) for simultaneous OER and HER, and no obvious performance decay is observed after 72 h. When integrated with a GaAs solar cell, the resulting photoassisted water splitting electrolyzer shows a certified solar‐to‐hydrogen efficiency of up to 18.01%, further demonstrating the feasibility of engineering protocols and the promising potential of bifunctional NiCo₂S₄ for large‐scale overall water splitting.     

3D Graphene Films Enable Simultaneously High Sensitivity and Large Stretchability for Strain Sensors

Integration of 2D membranes into 3D macroscopic structures is essential to overcome the intrinsically low stretchability of graphene for the applications in flexible and wearable electronics. Herein, the synthesis of 3D graphene films (3D‐GFs) using chemical vapor deposition (CVD) is reported, in which a porous copper foil (PCF) is chosen as a template in the atmospheric‐pressure CVD preparation. When the 3D‐GF prepared at 1000 °C (noted as 3D‐GF‐1000) is transferred onto a polydimethylsiloxane (PDMS) membrane, the obtained 3D‐GF‐1000/PDMS hybrid film shows an electrical conductivity of 11.6 S cm^?1 with good flexibility, indicated by small relative resistance changes (ΔR/R₀) of 2.67 and 0.36 under a tensile strain of 50% and a bending radius of 1.6 mm, respectively. When the CVD temperature is reduced to 900 °C (generating a sample noted as 3D‐GF‐900), the 3D‐GF‐900/PDMS hybrid film exhibits an excellent strain‐sensing performance with a workable strain range of up to 187% and simultaneously a gauge factor of up to ≈1500. The 3D‐GF‐900/PDMS also shows a remarkable durability in resistance in repeated 5000 stretching‐releasing cycles. Kinetics studies show that the response of ΔR/R₀ upon strain is related to the graphitization and conductivity of 3D‐GF which are sensitive to the CVD preparation temperature.     

Analysis of an MMI-Based Six-Port Circulator by Using 3-D Magneto-Optical Beam Propagation Method

An MMI-based six-port circulator is analyzed by 3-D magneto-optical (MO) beam propagation method (BPM). Since opposite nonreciprocal 4pi/3-phase shifts are introduced into the two sided interferometric arms of 3 times 3 mirror-image MMI coupler, light travels through this device in a nonreciprocal fashion and obeys the sequential order. After using the Ce:YIG/SOI bonding waveguide to construct the proposed circulator, the 3-D MO BPM formula are validated for the first time to simulate nonreciprocal device with external magnetization perpendicular to the light propagation direction. Simulation shows that this device features in easy fabrication, good operation bandwidth, ability to reduce the port count number.     

Next-generation optical storage area networks: the light-trails approach

Multiple architectures, technologies, and standards have been proposed for storage area networks, typically in the WAN environment. The transport aspect of storage signifies that optical communications is the key underlying technology. The contemporary SAN over optical network concept uses the optical layer for pure transport with minimal intelligence. This leads to high cost and overprovisioning. Future optical networks, however, can be expected to play a role in optimizing SAN extension into the WAN. An essential characteristic of SAN systems is tight coupling between nodes in a SAN network. Nodes in a SAN system have two critical functions that are presently emulated by data layers and can be offloaded to the optical layer. First, nodes need to signal among each other to achieve tasks such as synchronous and asynchronous storage. Second, to benefit from an optimized network, nodes need to allocate bandwidth dynamically in real time. In this article we show how the optical layer can be furthered from just pure transport to creating opportunities in provisioning as well as providing the mirroring function of SAN systems (multicasting) and consequently lead to reduction in cost. We demonstrate that the light-trail model is one way of efficiently utilizing the optical layer for SAN.     

A Coding and Automatic Error-Correction Circuit Based on the Five-Particle Entangled State

In this paper, we discuss the concepts of quantum coding and error correction for a five-particle entangled state. Error correction can correct bit-reverse or phase-flip errors of one and two quantum states and is no longer limited to only one quantum state. We encode a single quantum state into a five-particle entangled state before being transferred to the sender. We designed an automatic error-correction circuit to correct errors caused by noise. We also simplify the design process for a multiple quantum error-correction circuit. We compare error-correction schemes for five and three entangled particles in terms of efficiency and capabilities. The results show that error-correction efficiency and fidelity are im- proved.