Effect and mechanism of on-chip electrostatic discharge protection circuit under fast rising time electromagnetic pulse

The electrostatic discharge(ESD)protection circuit widely exists in the input and output ports of CMOS digital circuits,and fast rising time electromagnetic pulse(FREMP)coupled into the device not only interacts with the CMOS circuit,but also acts on the protection circuit.This paper establishes a model of on-chip CMOS electrostatic discharge protection circuit and selects square pulse as the FREMP signals.Based on multiple physical parameter models,it depicts the distribution of the lattice temperature,current density,and electric field intensity inside the device.At the same time,this paper explores the changes of the internal devices in the circuit under the injection of fast rising time electromagnetic pulse and describes the relationship between the damage amplitude threshold and the pulse width.The results show that the ESD protection circuit has potential damage risk,and the injection of FREMP leads to irreversible heat loss inside the circuit.In addition,pulse signals with different attributes will change the damage threshold of the circuit.These results provide an important reference for further evaluation of the influence of electromagnetic environment on the chip,which is helpful to carry out the reliability enhancement research of ESD protection circuit.

Performance of Lateral 4H-SiC Photoconductive Semiconductor Switches by Extrinsic Backside Trigger

Photoconductive semiconductor switch(PCSS)can be applied in pulsed high power systems and microwave techniques.However,reducing the damage and increasing the lifetime of silicon carbide(SiC)PCSS are still faced severe challenges.In this study,PCSSs with various structures were prepared on 4-inch diameter,500μm thick high-purity semi-insulating 4H-SiC substrates and their on-state resistance and damage mechanisms were investigated.It was found that the PCSS of an Au/TiW/Ni electrode system annealed at 950℃had a minimum on-state resistance of 6.0Ωat 1 kV bias voltage with a 532 nm and 170 mJ pulsed laser by backside illumination single trigger.The backside illumination single trigger could reduce on-state resistance and alleviate the damage of PCSS compared to the frontside trigger when the diameter of the laser spot was larger than the channel length of PCSS.For the 200 s trigger test by a 10 Hz laser,the black branch-like ablation on Au/TiW/Ni PCSS was mainly caused by thermal stress owing to hot carriers.Replacing metal Ni with boron gallium co-doped zinc oxide(BGZO)thin films annealed at 400℃,black branch-like ablation was alleviated while concentric arc damage was obvious at the anode.The major causes of concentric arc are both pulsed laser diffraction and thermal effect.

基于组合虚拟力的传感器网络三维空间重部署算法研究

无线传感器网络(Wireless sensor networks,WSNs)的重部署问题是提高无线传感器网络覆盖性能的一个重要问题,实用化的重部署算法需要充分考虑传感器资源的有限性和实际布撒情况.本文设计了基于组合虚拟力的分布式算法,该算法定义了传感器受到的邻居节点间的基于库仑力的斥力、目标覆盖区域的基于胡克定律的中心吸引力和边界斥力,综合这些力的合力以及单位能耗因素求得传感器节点每次移动的目标位置.本文算法还给出了调整的终止条件以保证传感器能够重部署至合理位置.理论论证和仿真实验表明,提出的基于组合虚拟力的重部署算法能使所有随机布撒的传感器节点在低能耗的情况下,进入目标覆盖区域并在该区域内自组织成一个具有高覆盖性和重连通性的网络拓扑.本文算法还解决了覆盖区域中存在障碍物的复杂情况.

微波二极管变频器的频域分析

本文采用频域延拓交调波平衡法(FDCIBM)分析微波二极管变频器,讨论了本振(LO)和中频(IF)(或LO和射频(RF))输入均为大信号时的变频器分析,推导了上、下变频器统一的频域交调波平衡方程,并给出了一个微波巴伦二极管上变频器的分析和测量结果.

Multi-Omics and Its Clinical Application in Hepatocellular Carcinoma:Current Progress and Future Opportunities

Hepatocellular carcinoma(HCC)is the sixth most common malignancy and the fourth leading cause of cancer related death worldwide.China covers over half of cases,leading HCC to be a vital threaten to public health.Despite advances in diagnosis and treatments,high recurrence rate remains a major obstacle in HCC management.Multi-omics currently facilitates surveillance,precise diagnosis,and personalized treatment decision making in clinical setting.Non-invasive radiomics utilizes preoperative radiological imaging to reflect subtle pixel-level pattern changes that correlate to specific clinical outcomes.Radiomics has been widely used in histopathological diagnosis prediction,treatment response evaluation,and prognosis prediction.High-throughput sequencing and gene expression profiling enabled genomics and proteomics to identify distinct transcriptomic subclasses and recurrent genetic alterations in HCC,which would reveal the complex multistep process of the pathophysiology.The accumulation of big medical data and the development of artificial intelligence techniques are providing new insights for our better understanding of the mechanism of HCC via multi-omics,and show potential to convert surgical/intervention treatment into an antitumorigenic one,which would greatly advance precision medicine in HCC management.

基于局部保持投影的M-QAM调制信号识别

针对基于统计的QAM信号识别算法,忽略了信号的局部特性,导致算法性能不好等问题,提出了一种基于流形学习的16QAM、32QAM、64QAM信号识别算法。该算法利用高阶累计量特征描述信号,在此基础上利用邻接图描述特征的内在几何属性,较好地刻画了数据的相似性几何属性,最后利用最近邻分类器算法进行分类。实验结果表明,该算法具有好的识别率,尤其在低信噪比下,算法性能比较突出。

Physical Properties of Si_(2)Ge and SiGe_(2) in Hexagonal Symmetry:First-Principles Calculations

We predict two novel group 14 element alloys Si_(2)Ge and SiGe_(2) in P6_(2)22 phase in this work through first-principles calculations.The structures,stability,elastic anisotropy,electronic and thermodynamic properties of these two proposed alloys are investigated systematically.The proposed P6_(2)22-Si_(2)Ge and P6_(2)22-SiGe_(2) have a hexagonal symmetry structure,and the phonon dispersion spectra and elastic constants indicate that these two alloys are dynamically and mechanically stable at ambient pressure.The elastic anisotropy properties of P6_(2)22-Si_(2)Ge and P6_(2)22-SiGe_(2) are examined elaborately by illustrating the surface constructions of Young’s modulus,the contour surfaces of shear modulus,and the directional dependence of Poisson’s ratio;the differences with their corresponding group 14 element allotropes P6_(2)22-Si_(3) and P6_(2)22-Ge_(3) are also discussed and compared.Moreover,the Debye temperature and sound velocities are analyzed to study the thermodynamic properties of the proposed P6_(2)22-Si_(2)Ge and P6_(2)22-SiGe_(2).

Tunable and stable localized surface plasmon resonance in SrMoO_(4) for enhanced visible light driven nitrogen reduction

Photocatalytic nitrogen reduction for the green synthesis of ammonia at ambient conditions has been slowed by the narrow light harvesting range,low activity and high charge recombination of photocatalysts.Plasmonic semiconducting nanomaterials are becoming the promising candidates for nitrogen photofixation because of the broad absorption spectrum,rich defects and hot carriers.In the present study,plasmonic SrMoO_(4) is developed by regulating the concentration of oxygen vacancies that are accompanied in the reduction process from Mo^(6+) to Mo^(5+).The stable and tunable localized surface plasmon resonance(LSPR)absorption in visible and near infrared light range makes the wide bandgap SrMoO_(4) utilize the solar energy more efficiently.Energetic electrons from both the intrinsic band excitation and the LSPR excitation enable the reduction of dinitrogen molecules thermodynamically in ultrapure water to ammonia.This work provides a unique clue to design efficient photocatalysts for nitrogen fixation.

Enhanced visible-light-driven photocatalytic activities of 0D/1D heterojunction carbon quantum dot modified CdS nanowires

Zero‐dimensional carbon dots(0D C‐dots)and one‐dimensional sulfide cadmium nanowires(1D CdS NWs)were prepared by microwave and solvothermal methods,respectively.A series of heterogeneous photocatalysts that consisted of 1D CdS NWs that were modified with 0D C‐dots(C‐dots/CdS NWs)were synthesized using chemical deposition methods.The mass fraction of C‐dots to CdS NWs in these photocatalysts was varied.The photocatalysts were characterized using X‐ray diffraction,scanning electron microscopy,transmission electron microscopy,X‐ray photoelectron spectroscopy,and ultraviolet‐visible spectroscopy.Their photocatalytic performance for the spitting of water and the degradation of rhodamine B(RhB)under visible light irradiation were investigated.The photocatalytic performance of the C‐dots/CdS NWs was enhanced when compared with that of the pure CdS NWs,with the 0.4%C‐dots/CdS NWs exhibiting the highest photocatalytic activity for the splitting of water and the degradation of RhB.The enhanced photocatalytic activity was attributed to a higher carrier density because of the heterojunction between the C‐dots and CdS NWs.This heterojunction improved the electronic transmission capacity and promoted efficient separation of photogenerated electrons and holes.

C2-Si:a Novel Silicon Allotrope in Monoclinic Phase

Based on density functional theory(DFT),a new silicon allotrope C2-Si is proposed in this work.The mechanical stability and dynamic stability of C2-Si are examined based on the elastic constants and phonon spectrum.According to the ratio of bulk modulus and shear modulus,C2-Si has ductility under ambient pressure;compared with Si_(64),Si_(96),I4/mmm and h-Si6,C2-Si is less brittle.Within the Heyd-Scuseria-Ernzerhof(HSE06)hybrid functional,C2-Si is an indirect narrow band gap semiconductor,and the band gap of C2-Si is only 0.716 eV,which is approximately two-thirds of c-Si.The ratios of the maximum and minimum values of the Young’s modulus,shear modulus and Poisson’s ratio in their 3D spatial distributions for C2-Si are determined to characterize the anisotropy.In addition,the anisotropy in different crystal planes is also investigated via 2D representations of the Young’s modulus,shear modulus,and Poisson’s ratio.Among more than ten silicon allotropes,C2-Si has the strongest absorption ability for visible light.

Semi-supervised Long-tail Endoscopic Image Classification

Objective To explore the semi-supervised learning(SSL) algorithm for long-tail endoscopic image classification with limited annotations.Method We explored semi-supervised long-tail endoscopic image classification in HyperKvasir,the largest gastrointestinal public dataset with 23 diverse classes.Semi-supervised learning algorithm FixMatch was applied based on consistency regularization and pseudo-labeling.After splitting the training dataset and the test dataset at a ratio of 4:1,we sampled 20%,50%,and 100% labeled training data to test the classification with limited annotations.Results The classification performance was evaluated by micro-average and macro-average evaluation metrics,with the Mathews correlation coefficient(MCC) as the overall evaluation.SSL algorithm improved the classification performance,with MCC increasing from 0.8761 to 0.8850,from 0.8983 to 0.8994,and from 0.9075 to 0.9095 with 20%,50%,and 100% ratio of labeled training data,respectively.With a 20% ratio of labeled training data,SSL improved both the micro-average and macro-average classification performance;while for the ratio of 50% and 100%,SSL improved the micro-average performance but hurt macro-average performance.Through analyzing the confusion matrix and labeling bias in each class,we found that the pseudo-based SSL algorithm exacerbated the classifier’ s preference for the head class,resulting in improved performance in the head class and degenerated performance in the tail class.Conclusion SSL can improve the classification performance for semi-supervised long-tail endoscopic image classification,especially when the labeled data is extremely limited,which may benefit the building of assisted diagnosis systems for low-volume hospitals.However,the pseudo-labeling strategy may amplify the effect of class imbalance,which hurts the classification performance for the tail class.

陕西战略性新兴产业发展研究

战略性新兴产业是指关系到国民经济社会发展和产业结构优化升级，具有全局性、长远性、导向性和动态性特征的新兴产业。本文介绍了我国以及陕西省战略性新兴产业发展现状，并为其发展提供了建议。

IEEE802.11MAC协议中一种改进的退避解决算法

IEEE802.11无线局域网,在共享信道中经历碰撞的网络节点需要随机退避一段时间,这段时间是从竞争窗口中均匀选取,竞争窗口大小由BEB机制动态控制,一些文献研究表明,BEB机制在重负载的情况下,突现出公平性问题和低的吞吐量,本文基于MILD退避机制,提出一种适用于分布式协调功能改进算法。该算法通过修改802.11的MAC层中的DCF(DistributedCoordinationFunction)子协议,改善了IEEE802.11无线局域网在拥塞情况下的性能,提高了网络吞吐量。

m×n排序问题在实际中的应用

本文对某工厂生产实际中的一个零件加工顺序问题(m=12,n=45)建立了两个模型,并应用在计算机上易实现的一个排序问题的算法进行了计算,两个模型都使该厂每年的生产时间缩短至少100天,模型二还大大增加了生产量,从而提高了生产效率。

Mutual coupling reduction of multiple antenna systems

A multi-band multi-antenna system has become an important trend in the development of mobile communication systems.However,strong mutual coupling tends to occur between antenna elements with a small space,distorting array antennas’performance.Therefore,in the multiple-input multiple-output(MIMO)antenna system,high isolation based on miniaturization of the antenna array has been pursued.We study in depth the methods of decoupling between antenna elements.Reasons for the existence of mutual coupling and advantages of mutual coupling reduction are analyzed.Then the decoupling methods proposed in recent works are compared and analyzed.Finally,we propose a metasurface consisting of double-layer short wires,which can be applied to improve the port isolation of antennas arranged along the H-plane and E-plane.Results show that the proposed metasurface has good decoupling effect on a closely placed antenna array.

A look at field manipulation and antenna design using 3D transformation electromagnetics and 2D surface electromagnetics

While many techniques have been developed for the design of different types of antennas,such as wire antenna,patch antenna,lenses,and reflectors,these cannot be said general-purpose strategies for the synthesis and design of antennas to achieve the performance characteristics specified by users.Recently,there has been an increasing need for the development of antenna design techniques because of the advent of 5 G and a variety of space,defense,biological,and similar applications,for which a robust and general-purpose design tool is not to be developed.The main objective of this study is to take a look at antenna design from the field manipulation point of view,which has the potential to partially fulfill this need.We review the existing field manipulation techniques,including field transformation methods based on Maxwell’s and wave equations,point out some limitations of these techniques,and then present ways to improve the performance of these methods.Next,we introduce an alternative approach for field manipulation based on two-dimensional(2 D)metasurfaces,and present laws of the generalized reflection and refraction that are based on 2 D surface electromagnetics.Then,we explore how to overcome the limitations of conventional reflection and refraction processes that are strictly bounded by the critical angle.Finally,we provide some application examples of field manipulation methods in the antenna design,with a view on developing a general-purpose strategy for antenna design for future communication.