摘要：Due to their high capacity,the P2-type layered oxide cathodes containing oxygen redox reaction processes have attracted wide attention for sodium-ion ***,these materials usually exhibit poor electro-chemical properties,resulting from irreversible oxygen redox reactions and phase transition processes at high voltages,and thus hinder their large-scale *** work reveals the mechanism for the significantly improved cycle stability and rate performance of Co/Ni-free Na_(0.7)5Li_(0.25-2/3x)CuxMn_(0.75-1/3x)O_(2)via Cu ***-situ XPS demonstrates that Cu doping reduces the amount of Mn^(3+)that triggers the Jahn-Teller effect during the *** addition,the electron enrichment of oxygen around Cu can alleviate the irreversible oxidation of oxygen,and thus suppressing the phase transition originates from the rapid weakening of the electrostatic repulsion between ***,in-situ XRD results verify that the Na_(0.7)5Li_(0.19)Cu_(0.09)Mn_(0.7)2O_(2)maintains the P2 phase structure during charging and discharging,resulting in a near-zero strain characteristic of 1.9%.Therefore,the optimized cathode delivers a high reversible capacity of 194.9 mAh g−1 at 0.1 C and excellent capacity retention of 88.6%after 100 cycles at 5 *** full cell paired with commercial hard carbon anode delivers energy density of 240 Wh kg−*** research provides an idea for designing a new type of intercalated cathode for sodium-ion batteries with low cost and high energy density.

摘要：设计了一款用于无线通信射频系统的新型双平衡混频器芯片,该混频器的输出信号中不存在与射频输入信号相关的二次非理想项,具有高线性度.该混频器基于新型乘法器结构,在两个工作于线性区的对称金属氧化物半导体(MOS)晶体管的源、漏两极加入差分射频信号,在其栅极加入差分本振信号,从而以低复杂度方式实现射频信号与本振信号的双平衡混频或相乘;采用差分推挽放大器及源随器作为芯片的输出缓冲接口,改善了芯片与片外电路之间的隔离度,提高了功率增益和输出匹配性能.芯片采用0.18μm射频(RF)互补金属氧化物半导体(CMOS)工艺流片,实现超宽频带范围内的信号混频或相乘,1dB压缩点2.9dBm,三阶交调16 dBm,总功耗25 mW,芯片性能良好,可以满足高性能、超宽带、高速无线通信系统的要求.

摘要：Oxygen electrocatalysis,exemplified by the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),is central to energy storage and conversion technologies such as fuel cells,metal-air batteries,and water ***,highly effective and inexpensive earth-abundant materials are sought after to replace the noble metal-based electrocatalysts currently in ***,metal-organic frameworks(MOFs)and carbon-based MOF derivatives have attracted considerable attention as efficient catalysts due to their exceedingly tunable morphologies,structures,compositions,and ***,we report two-dimensional(2D)MOF/MOF derivative coupled arrays on nickel foam as binder-free bifunctional ORR/OER catalysts with enhanced electrocatalytic activity and *** remarkable electrochemical properties are primarily attributed to fully exposed active sites and facilitated charge-transfer *** coupled and hierarchical nanosheet arrays produced via our growth-pyrolysis-regrowth strategy offer promise in the development of highly active electrodes for energy-related electrochemical devices.

摘要：设计端射天线阵时,使用汉森伍德条件会提高方向性。如果阵列单元数目较少,则单元间距根据汉森伍德条件也相应较小。但较小的单元间距在实际天线阵设计中会增大天线单元之间的耦合,降低了天线阵的整体性能。重新推导了天线阵方向图公式,提出了一种新馈电相位关系的端射阵。既满足端射阵的相位要求,形成增强方向性端射,又拉大了间距降低单元之间的互耦,比普通端射阵提高了阵列的方向性。

摘要：为了缩短姿控飞轮控制系统的设计周期和快速验证设计方案的可行性及有效性,在分析姿控飞轮电机本体数学模型的基础上,结合该姿控飞轮控制系统所采用的加速控制、制动控制、换相控制,建立了姿控飞轮控制系统模型。针对姿控飞轮的共性问题:飞轮过零响应问题,以速度模式下的指令响应为例分析了调压调速控制方式与调压调速结合反接制动方式下的飞轮速度、电流、端电压以及力矩响应。分析结果表明:在0.025 Hz的速度指令下,调压调速结合反接制动方式具有更好的过零响应。

摘要：为解决目前高级综合方法在处理滑动窗口程序时存在的存储系统设计瓶颈问题,提出了参数化存储体系结构模型.采用三级存储层次,充分开发内层循环、外层循环的数据重用;采用寄存器平移策略,简化硬件设计.与相关工作相比,这种体系结构模型使用相对较少的存储资源,将程序执行速度提高了2.13倍～3.8倍,将执行频率由相关工作的69MHZ提升到了238.7MHZ.

摘要：基于裂缝谐振环结构的降频技术,首先设计了一种电尺寸较小的左手介质微带线单元,并根据电磁波在微带线上的传输和反射数据,分别计算了左手介质的有效介电常数和有效磁导率.之后针对左手介质八元阵列进行三维电磁仿真实验,结果表明该八元阵列在左手介质频段上具有独特的后向波效应,从而证实了该左手介质频段的存在.与传统的左手介质微带单元相比,阐述的左手介质单元的电尺寸减小了60%,而且结构简单,便于加工,适用于平面电路器件的小型化等应用研究工作.

摘要：当前的网络舆情事件中,公众的表达存在态度不友善、言语不客观等问题。这与网络舆情表达主体和客体存在某些伦理失范有关。网络舆情表达主体包括个体表达、群体表达、整体表达和全体表达。网络舆情的表达伦理问题主要体现在动机代替是非、态度甚于事实、关系超越道理以及表达主体的不平衡现象。认识表达伦理存在的问题,有利于规范网络舆论,使表达主体的言论自由而负责。

摘要：通过对异向介质激发机理的深入分析,最终设计出了一种结构新颖的小单元、宽频带异向介质。其绝对带宽达到2.6GHz,远远优于传统异向介质。文中对这种异向介质的后向波特性和负折射特性进行了数值仿真,结果表明,在异向介质工作频段内观测到明显的后向波效应和负折射效应,从而使该异向介质的存在性得到有力证明。本研究成果为基于异向介质的新型微波、毫米波器件在空间通信技术中的应用奠定了坚实的基础。

摘要：粒子群优化算法作为优秀的群体智能算法之一,已经被广泛应用于电磁优化问题中.通过与时域有限差分(FDTD)算法相结合,粒子群优化算法被运用于频率选择表面的优化设计.在此过程中,通过使用图形处理器(GPU)加速技术将FDTD算法速度提高近100倍,配合FDTD的宽频特性显著加速了优化过程.在此基础上,针对给定单元结构以及未知单元结构两种频率选择表面设计情况,分别采用带惯性权重的粒子群优化算法以及二进制离散粒子群优化算法进行优化.提出的两种优化流程在算例中得到验证与分析,证明了其可行性及高效性.