基于普通向量的虹膜识别算法

典型的虹膜识别算法都是针对单个虹膜样本采用图像处理的方法提取虹膜特征,只强调个体信息,而忽略了虹膜样本间的联系.本文提出了一种基于普通向量的虹膜识别算法,从模式分析的角度,利用普通向量方法融合虹膜的个体特征和统计特征,并且通过高效的睫毛滤除和眼皮定位的算法,进一步提高了识别的精度和算法的稳定性.实验结果表明了该算法具有良好的性能.     

Discerning nonstationarity from nonlinearity in seizure-free and preseizure EEG recordings from epilepsy patients

A number of recent studies indicate that nonlinear electroencephalogram (EEG) analyses allow to define a state predictive of an impending epileptic seizure. In this paper, we combine a method for detecting nonlinear determinism with a novel test for stationarity to characterize EEG recordings from both the seizure-free interval and the preseizure phase. We discuss differences between these periods, particularly an increased occurrence of stationary, nonlinear segments prior to seizures. These differences seem most prominent for recording sites within the seizure-generating area and for EEG segments less than one minute's length.     

220GHz低噪声放大器研究

基于IHP锗硅BiCMOS工艺,研究和实现了两种220 GHz低噪声放大器电路,并将其应用于220 GHz太赫兹无线高速通信收发机电路。一种是220 GHz四级单端共基极低噪声放大电路,每级电路采用了共基极（Common Base, CB）电路结构,利用传输线和金属-绝缘体-金属(Metal-Insulator-Metal, MIM)电容等无源电路元器件构成输入、输出和级间匹配网络。该低噪放电源的电压为1.8 V,功耗为25 mW,在220 GHz频点处实现了16 dB的增益,3 dB带宽达到了27 GHz。另一种是220 GHz四级共射共基差分低噪声放大电路,每级都采用共射共基的电路结构,放大器利用微带传输线和MIM电容构成每级的负载、Marchand-Balun、输入、输出和级间匹配网络等。该低噪放电源的电压为3 V,功耗为234 mW,在224 GHz频点实现了22 dB的增益,3 dB带宽超过6 GHz。这两个低噪声放大器可应用于220 GHz太赫兹无线高速通信收发机电路。     

Avalanche‐Discharge‐Induced Electrical Forming in Tantalum Oxide‐Based Metal–Insulator–Metal Structures

Oxide‐based metal–insulator–metal structures are of special interest for future resistive random‐access memories. In such cells, redox processes on the nanoscale occur during resistive switching, which are initiated by the reversible movement of native donors, such as oxygen vacancies. The formation of these filaments is mainly attributed to an enhanced oxygen diffusion due to Joule heating in an electric field or due to electrical breakdown. Here, the development of a dendrite‐like structure, which is induced by an avalanche discharge between the top electrode and the Ta₂O_5‐x layer, is presented, which occurs instead of a local breakdown between top and bottom electrode. The dendrite‐like structure evolves primarily at structures with a pronounced interface adsorbate layer. Furthermore, local conductive atomic force microscopy reveals that the entire dendrite region becomes conductive. Via spectromicroscopy it is demonstrated that the subsequent switching is caused by a valence change between Ta⁴⁺ and Ta⁵⁺, which takes place over the entire former Pt/Ta₂O_5‐x interface of the dendrite‐like structure.     

Enhancing Planar Inverted Perovskite Solar Cells with Innovative Dumbbell-Shaped HTMs: A Study of Hexabenzocoronene and Pyrene-BODIPY-Triarylamine Derivatives

Dumbbell-shaped systems based on PAHs-BODIPY-triarylamine hybrids TM-(01-04) are designed as novel and highly efficient hole-transporting materials for usage in planar inverted perovskite solar cells. BODIPY is employed as a bridge between the PAH units, and the effects of the conjugated π-system's covalent attachment and size are investigated. Fluorescence quenching, 3D fluorescence heat maps, and theoretical studies support energy transfer within the moieties. The systems are extremely resistant to UVC 254 nm germicidal light sources and present remarkable thermal stability at degradation temperatures exceeding 350 °C. Integrating these systems into perovskite solar cells results in outstanding power conversion efficiency (PCE), with TM-02-based devices exhibiting a PCE of 20.26%. The devices base on TM-01, TM-03, and TM-04 achieve PCE values of 16.98%, 17.58%, and 18.80%, respectively. The long-term stability of these devices is measured for 600 h, with initial efficiency retention between 94% and 86%. The TM-04-based device presents noticeable stability of 94%, better than the reference polymer PTAA with 91%. These findings highlight the exciting potential of dumbbell-shaped systems based on PAHs-BODIPY-triarylamine derivatives for next-generation photovoltaics.     

245 GHz接收机芯片片外测试与实验

为了实现太赫兹气体频谱分析传感器,对245 GHz次谐波接收机芯片的片外测试展开研究。建立了245 GHz次谐波接收机片外测试系统以及基于245 GHz接收机芯片及发射机芯片的气体频谱分析传感器片外展示测试系统,对245 GHz次谐波接收机芯片转换增益和带宽进行测试。片外测试系统得到15 dB转换增益和15 GHz带宽;片外展示测试系统得到9 dB转换增益和16 GHz带宽。片外测试系统和片外展示测试系统结果基本吻合。在片外展示测试系统中加入气腔,即构成气体频谱分析传感器。与现有同类型传感器相比,本文的次谐波接收机具有高增益、高带宽、集成本地振荡信号、低功耗等优势,非常适用于消费电子领域小体积的智能气体频谱分析传感器。     

Functionalized Graphene as Extracellular Matrix Mimics: Toward Well‐Defined 2D Nanomaterials for Multivalent Virus Interactions

Polysulfated nanomaterials that mimic the extracellular cell matrix are of great interest for their potential to modulate cellular responses and to bind and neutralize pathogens. However, control over the density of active functional groups on such biomimetics is essential for efficient interactions, and this remains a challenge. In this regard, producing polysulfated graphene derivatives with control over their functionality is an intriguing accomplishment in order to obtain highly effective 2D platforms for pathogen interactions. Here, a facile and efficient method for the controlled attachment of a heparin sulfate mimic on the surface of graphene is reported. Dichlorotriazine groups are conjugated to the surface of graphene by a one‐pot [2+1] nitrene cycloaddition reaction at ambient conditions, providing derivatives with defined functionality. Consecutive step by step conjugation of hyperbranched polyglycerol to the dichlorotriazine groups and eventual conversion to the polyglycerol sulfate result in the graphene based heparin biomimetics. Scanning force microscopy, cryo‐transmission electron microscopy, and in vitro bioassays reveal strong interactions between the functionalized graphene (thoroughly covered by a sulfated polymer) and vesicular stomatitis virus. Infection experiments with highly sulfated versions of graphene drastically promote the infection process, leading to higher viral titers compared to nonsulfated analogues.     

An integrated 8-12 GHz fractional-N frequency synthesizer in SiGe BiCMOS for satellite communications

We present an integrated fractional-N low-noise frequency synthesizer for satellite applications. By using two integrated VCOs and combining digital and analog tuning techniques, a PLL lock range from 8 to 12 GHz is achieved. Due to a small VCO fine tuning gain and optimized charge pump output biasing, the phase noise is low and almost constant over the tuning range. All 16 sub-bands show a tuning range above 900 MHz each, allowing temperature compensation without sub-band switching. This makes the synthesizer robust against variations of the device parameters with process, supply voltage, temperature and aging. The measured phase noise is ?87 dBc/Hz and ?106 dBc/Hz at 10 kHz and 1 MHz offset, respectively. In integer-N mode, phase noise values down to ?98 dBc/Hz at 10 kHz and ?111 dBc/Hz at 1 MHz offset, respectively, were measured.     

A Low Temperature Route toward Hierarchically Structured Titania Films for Thin Hybrid Solar Cells

The requirement of high‐temperature calcination for titanium dioxide in (solid‐state) dye‐sensitized solar cells (DSSCs) implies challenges with respect to reduced energy consumption and the potential for flexible photovoltaic devices. Moreover, the use of dye molecules increases production costs and leads to problems related with dye bleaching. Therefore, fabrication of dye‐free hybrid solar cells at low temperature is a promising alternative for current DSSC technology. In this work the authors fabricate hierarchically structured titania thin films by combining a polystyrene‐block‐polyethylene oxide template assisted sol–gel synthesis with nano‐imprint lithography at low temperatures. The achieved films are filled with poly(3‐hexylthiophene) to form the active layer of hybrid solar cells. The surface morphology is probed via scanning electron microscopy and atomic force microscopy, and the bulk film morphology is examined with grazing incidence X‐ray scattering. Good light absorption by the active layer is proven by UV–vis spectroscopy. An enhancement in light absorption is observed and ascribed to light scattering in mesoporous titania films with imprinted superstructures. Accordingly a better photovoltaic performance is found for nano‐imprinted solar cells at various angles of light incidence.