PCM语音编解码系统中抗混叠滤波器的设计

PCM（脉冲编码调制）是一种编码方式,它可以将语音信号转换成数字信号。我们知道在音频系统中经常会出现信号混叠,基于这个原因,本文介绍了一种在PCM语音编解码系统所使用的抗混叠滤波。它是一个有源的、低通三阶巴特沃兹滤波器。     

WO3/TiO2 nanocomposites: Salt–ultrasonic assisted hydrothermal synthesis and enhanced photocatalytic activity

A series of WO₃/TiO₂ composite photocatalysts were fabricated via a facile salt–ultrasonic assisted hydrothermal process. The obtained samples were characterized by X-ray diffraction, scanning eletron microscopy, energy dispersive X-ray spectroscopy and UV–vis diffused reflectance spectroscopy. It was confirmed that anatase TiO₂ and monoclinic WO₃ coexisted in the composites. The photocatalytic activity of as-prepared WO₃/TiO₂ composites for degradation of Rhodamin B (RhB) under visible light irradiation was investigated. The results showed that WO₃/TiO₂ composites have a higher photocatalytic activity than those of pure TiO₂ and pure WO₃. First-principle calculations based on density functional theory were performed to explore the electronic structure and illustrate the photocatalytic mechanism of WO₃/TiO₂. The calculated energy gap was 2.53 eV, which was close to the experimental observation (2.58 eV). Due to the combination of WO₃/TiO₂, the photoinduced electrons and holes transfer between the WO₃ and TiO₂ in opposite directions, thus providing sufficient charge separation, which contributed to the photocatalytic activity enhancement.     

无线双模数字对讲机的设计与实现

传统模拟对讲机由于频谱利用率低、抗干扰性能差、频道开放、不具有保密性等原因已经很难满足需求。文章介绍的无线双模对讲机用于改善传统模拟对讲机抗干扰及保密性差的缺点,所提双模对讲机设计方案综合了集群和无中心两种工作模式功能,具有灵活设置与抗干扰性强的优点。文中重点设计了对讲机的软硬件结构,还对音频编解码进行了讨论分析。     

煤矿井下防爆型无主机语音通信系统设计

针对煤矿井下语音通信速率低,带宽小,音质差,噪声大等缺点,设计了一种煤矿井下防爆型低功耗无主机语音通信系统。该系统的语音编解码采用高压缩率算法RALCWI的CMX618,系统控制采用低功耗STM32F103RE控制器,语音的远距离通信采用CAN总线方式。试验结果表明,语音的压缩速率模式2 400 b/s时,音质较好,通信稳定可靠,满足煤矿井下语音通信带宽要求,语音质量,系统稳定与可靠性高的要求,易于在煤矿系统中推广。     

昭通市电视台3+1讯道高清卫星车系统设计

昭通市电视台3+1讯道高清卫星车系统是按照国家新闻出版广电总局安全播出实施细则要求设计,即主要(单溃点)、关键设备要求冗余设计.对3+1讯道高清卫星车系统的主要视频设备和卫星传输设备性能和选择进行了详细介绍,特别是卫星传输部分的功放性能、工作方式、功放输出增益进行了详细介绍,该系统通过多次直播运行,设备安全稳定.     

自由空间基于激光编码调制技术语音通讯机的系统设计

基于自由空间光通讯(FSO)技术和OCDMA编码调制技术实现了自由空间语音异地通讯,具有高速高效、抗干扰能力强、保密性好等优点。系统设计采用双CPU结构,主控CPU单元主要实现语音采集、信号编码、数字调制等功能,辅单片机则为FSO关键技术ATP伺服系统的控制核心,论述了设计要点,并给出了测试结果。     

DX-600发射机并机网络备份冷却控制线路的设计

加装国产变频器作为发射机阻隔风机的备用控制器,对风机控制器的电源通路和故障检测信号通路增设应急处理,同时采用内部编程和温控取样变送输出两套方案来控制变频器的输出,彻底解决了因发射机风机控制器故障而造成的发射机停机故障,增强了发射机运行的安全稳定。     

Precisely Controlled Microsphere Design via Visible‐Light Cross‐Linking of Functional Prepolymers

A new strategy for particle synthesis is enabled by utilizing modern synthetic, polymer, and photochemical techniques to facilitate the synthesis of highly narrow–disperse multifunctional microspheres from visible‐light induced crosslinking of prepolymers in both a single and dual polymer system. The approach requires no stabilizers, bases, or initiators, and proceeds at ambient temperature to yield microspheres with a tunable size range (0.25–5 µm) in less than 4 h, depending largely on solvent composition, but also polymer concentration (2–10 mg mL^?1), ratio, and irradiation intensity (3–20 W). Critically, the visible‐light induced dimerization reaction exploited herein enables simple functional particle syntheses via a single polymer system. Underpinned by an in‐depth kinetic analysis of the particle formation as well as a detailed small molecule study, the mechanism for particle formation is also elucidated. Importantly, inherent advantages of the system are exploited for surface functionalization of residual acrylate and hydroxyl groups (generating inherently fluorescent particles).     

Nanoscale Metal‐Organic Frameworks: Synthesis,Biocompatibility, Imaging Applications,and Thermal and Dynamic Therapy of Tumors

Nanoscale metal‐organic frameworks (NMOFs) have attracted increasing attention for biomedical applications due to their large specific surface area, good biocompatibility, adjustable structures, and diverse functions. By choosing appropriate metal ions and ligands, NMOFs can be synthesized and regulated to assist the diagnosis and treatment of cancer, acting as imaging agents, drug carriers, and cancer therapeutic agents. This review summarizes the recent advances of NMOFs in synthesis, biocompatibility, imaging, and applications in cancer therapies. Among these, the term “biocompatibility” is used to outline their various biological characteristics, and it is mainly discussed from the aspects of size and surface properties of NMOFs. The imaging section mainly emphasizes the application advantages of NMOFs as imaging agents in magnetic resonance, computed tomography, and fluorescence imaging. The applications of NMOFs in four cancer therapies, including phototherapy, radiotherapy, microwave therapy, and ultrasonic therapy, are addressed, especially for thermal and dynamic therapy. Finally, the prospects and challenges of NMOFs in imaging and cancer therapies are also discussed.