播出系统中KII与PVS两代硬盘服务器的混合使用

目前Profile硬盘服务器的用户存在的现实问题是,在对系统进行升级改造时,在PDF和PVS系列硬盘服务器已经停产情况下,如何使KII系列与PDF或PVS系列安全高效地混合使用,温州市广播电视总台在这方面成功地解决了这个问题,通过近一年的使用,达到了预期的效果。简述KII与PVS在播出系统中的混用,希望能给Profile用户提供一些有益经验。     

Performance of Multiband Complex-Wavelet-Based MC-CDMA System with Space-Time Coding over Nakagami-m Fading Channels

Space-time coding technique and Multi-carrier CDMA (MC-CDMA) technique have received much interest due to their high frequency spectrum efficiency and high data rate transmission. On the basis of analyzing the two technique principle, utilizing the optimized multiband complex wavelet as multi-carrier basis function, we propose an MC-CDMA system based on multiband complex wavelet and space-time coding for downlink and investigate the system bit error rate (BER) performance over Nakagami-m fading channel. The system has much higher spectrum efficiency and data rate due to no need any cyclic prefix (CP) when compared to the conventional MC-CDMA system. Moreover, the application of space-time coding technique improves the ability against fading channel effectively and perfects the downlink performance further. Simulation results show that the proposed multiband complex-wavelet-based MC-CDMA (MBCW-MC-CDMA) system performs better than conventional MC-CDMA system and real wavelet-packet-based MC-CDMA system due to its superior ability against interferences. Especially, the space-time coded MBCW-MC-CDMA system has superior performance, and it outperforms single antenna MBCW-MC-CDMA and conventional MC-CDMA with space-time coding.     

CADD: connectivity-aware data dissemination using node forwarding capability estimation in partially connected VANETs

The recent development of the vehicular ad hoc networks (VANETs) has motivated an increasing interest in vehicular services and applications, such as active safety service and the infotainment service. Effective data Dissemination has become more and more important in vehicular services sharing. In this paper, the connectivity characteristics of VANETs are theoretically analyzed and implemented to show the partial connections in vehicle to vehicle communication. Hence, we propose the connectivity-aware data dissemination (CADD) in partially connected VANETs will improve the data transmission capacity. In the CADD protocol, a new metric of the node forwarding capability estimation is introduced. The metric is designed by the combination the throughput function and the active connection time estimation. And then, the high efficiency data dissemination protocol is designed by the new metric. Simulation results show that the CADD protocol outperforms existing solutions in terms of the packet delivery ratio, the transmission delay, and the protocol overhead under the condition of the intermittent network connectivity.

     

Atomic Ni Anchored Covalent Triazine Framework as High Efficient Electrocatalyst for Carbon Dioxide Conversion

Electrochemically driven carbon dioxide (CO₂) conversion is an emerging research field due to the global warming and energy crisis. Carbon monoxide (CO) is one key product during electroreduction of CO₂; however, this reduction process suffers from tardy kinetics due to low local concentration of CO₂ on a catalyst's surface and low density of active sites. Herein, presented is a combination of experimental and theoretical validation of a Ni porphyrin‐based covalent triazine framework (NiPor‐CTF) with atomically dispersed NiN₄ centers as an efficient electrocatalyst for CO₂ reduction reaction (CO₂RR). The high density and atomically distributed NiN₄ centers are confirmed by aberration‐corrected high‐angle annular dark field scanning transmission electron microscopy and extended X‐ray absorption fine structure. As a result, NiPor‐CTF exhibits high selectivity toward CO₂RR with a Faradaic efficiency of >90% over the range from ?0.6 to ?0.9 V for CO conversion and achieves a maximum Faradaic efficiency of 97% at ?0.9 V with a high current density of 52.9 mA cm^?2, as well as good long‐term stability. Further calculation by the density functional theory method reveals that the kinetic energy barriers decreasing for *CO₂ transition to *COOH on NiN₄ active sites boosts the performance.     

Wigner-Ville分布及其在脉压雷达信号检测中的应用

本文在分析Wigner Ville分布及其在瞬时频率提取中的应用的基础上,结合脉冲压缩雷达信号的特点,提出了基于中频数字化接收机,采用Wigner Ville分布检测脉冲压缩雷达信号的思路。最后分别针对模拟信号与实际信号进行了计算机仿真实验。     

Surface morphology of [110] a-plane GaN growth by MOCVD on [1■02] r-plane sapphire

Nonpolar a-plane [110] GaN has been grown on r-plane [1■02] sapphire by MOCVD, and investigated by high resolution X-ray diffraction and atomic force microscopy. As opposed to the c-direction, this particular orientation is non-polar, and it avoids polarization charge, the associated screening charge and the consequent band bending. Both low-temperature GaN buffer and high-temperature AlN buffer are used for a-plane GaN growth on r-plane sapphire, and the triangular pits and pleat morphology come forth with different buffers, the possible reasons for which are discussed. The triangular and pleat direction are also investigated. A novel modulate buffer is used for a-plane GaN growth on r-plane sapphire, and with this technique, the crystal quality has been greatly improved.     

Field-Induced Multiscale Polarization Configuration Transitions of Mesentropic Lead-Free Piezoceramics Achieving Giant Energy Harvesting Performance

The development of high-performance (K,Na)NbO₃ (KNN)-based lead-free piezoceramics for next-generation electronic devices is crucial for achieving environmentally sustainable society. However, despite recent improvements in piezoelectric coefficients, correlating their properties to underlying multiscale structures remains a key issue for high-performance KNN-based ceramics with complex phase boundaries. Here, this study proposes a medium-entropy strategy to design “local polymorphic distortion” in conjunction with the construction of uniformly oversize grains in the newly developed KNN solid-solution, resulting in a novel large-size hierarchical domain architecture (≈0.7 µm wide). Such a structure not only facilitates polarization rotation but also ensures a large residual polarization, which significantly improves the piezoelectricity (≈3.2 times) and obtains a giant energy harvesting performance (W_out = 2.44 mW, P_D = 35.32 µW mm⁻³, outperforming most lead-free piezoceramics). This study confirms the coexistence of multiphase through the atomic-resolution polarization features and analyzes the domain/phase transition mechanisms using in situ electric field structural characterizations, revealing that the electric field induces highly effective multiscale polarization configuration transitions based on T–O–R sequential phase transitions. This study demonstrates a new strategy for designing high-performance piezoceramics and facilitates the development of lead-free piezoceramic materials in energy harvesting applications.     

An improved /spl rho/DFIIt structure for digital filters with minimum roundoff noise

In this brief, a new efficient digital filter structure with minimum roundoff noise is derived. This structure can be block-diagrammed as the recently proposed direct-form II transposed (DFIIt) structure in /spl rho/-operator, denoted as /spl rho/DFIIt, in which the first-order /spl rho/ operators are replaced with a set of second-order operators. The corresponding expression for the roundoff noise gain is obtained. The problem of how to choose these second-order operators is investigated in terms of minimizing the roundoff noise gain. Two design examples are given to illustrate the excellent performance of the proposed structure and to confirm the theoretical analysis.     

待熔光子晶体光纤中的热传导特性

在光子晶体光纤(PCF)的熔接过程中,由于包层空气孔结构的存在,同在熔接过程中存在着潜在的空气孔形变,使得加热过程更为复杂.对待熔的光子晶体光纤的热传导特性进行了研究,以二氧化碳激光作为熔接热源,根据传热学及能量守恒定律建立三维对称的热传导模型,进而对光子晶体光纤熔接的瞬态传热过程进行仿真分析和实验研究.分析表明,该模型可以很好地确定影响光子晶体光纤熔接过程中热传导特性的各个主要因素,为最终确定最佳熔接条件建立理论基础.