Unexpected Sole Enol‐Form Emission of 2‐(2′‐Hydroxyphenyl)oxazoles for Highly Efficient Deep‐Blue‐Emitting Organic Electroluminescent Devices

Considerable efforts have been devoted to the development of highly efficient blue light‐emitting materials. However, deep‐blue fluorescence materials that can satisfy the Commission Internationale de l'Eclairage (CIE) coordinates of (0.14, 0.08) of the National Television System Committee (NTSC) standard blue and, moreover, possess a high external quantum efficiency (EQE) over 5%, remain scarce. Here, the unusual luminescence properties of triphenylamine‐bearing 2‐(2′‐hydroxyphenyl)oxazoles ( 3a–3c ) and their applications in organic light‐emitting diodes (OLEDs) are reported as highly efficient deep‐blue emitters. The 3a ‐based device exhibits a high spectral stability and an excellent color purity with a narrow full‐width at half‐maximum of 53 nm and the CIE coordinates of (0.15, 0.08), which is very close to the NTSC standard blue. The exciton utilization of the device closes to 100%, exceeding the theoretical limit of 25% in conventional fluorescent OLEDs. Experimental data and theoretical calculations demonstrate that 3a possesses a highly hybridized local and charge‐transfer excited state character. In OLEDs, 3a exhibits a maximum luminance of 9054 cd m^?2 and an EQE up to 7.1%, which is the first example of highly efficient blue OLEDs based on the sole enol‐form emission of 2‐(2′‐hydroxyphenyl)azoles.     

基于AT91X40系列的手持式触摸屏

基于当前手持式触摸屏稳定性不高,性能不可靠的状况,采用AT91X40系列微控制器作为控制芯片,由于该芯片功能强大,集成度高,处理数据能力强,稳定性高,所以基于AT91X40系列的手持式触摸屏具有体积小巧,功能强大,操作简便等特点。手持式触摸屏的显示和输入设备选用了ADS7843和SED1335两种主流触摸和LCD显示芯...     

基于Newmark法两端支座松动拉杆转子动力学分析

建立了具有两端轴承基座松动故障的拉杆转子模型(松动轴承基座质量称为松动质量块,松动轴承基座与地面连接的刚度称为松动刚度),并推导了其运动微分方程.基于分离变量法和Sturm-Liouville理论得到了有限长滑动轴承油膜力近似解析解,运用Newmark法分析了该转子系统的非线性动力学行为.首先,将无故障转子、一侧轴承基...     

SPI演算规范的建模、实现验证研究

针对安全协议安全属性是否满足,缺乏有效性能评价方法的现状,大都使用SPI演算或相近的进程代数方法进行建模。利用这种方法不仅能够有效地形式化描述安全协议,并且能够对安全协议进行多方面的系统评价,但基本上没有说明怎么样寻找设计合适的验证工具,验证其安全属性实现的正确性。本文引入基于SPI演算的验证工具SPRITE来保证建模过程正确性,并设计给出实现映射的具体方法。本方法通过对典型的WOO-LAM单向认证协议予以说明,最后SPRITE产生的具体JAVA代码,给出了安全协议的安全属性,使形式化描述的协议的安全属性是否满足更接近于人的理解而不仅只是机器的解释。     

Locally Welded Silver Nano‐Network Transparent Electrodes with High Operational Stability by a Simple Alcohol‐Based Chemical Approach

As an indispensable aspect of emerging flexible optoelectronics, flexible transparent electrodes, especially those comprised of metal nanowires, have attracted great attentions recently. Welding the nanowire junctions is an effective strategy for reducing the sheet resistance and improving the operational stability of flexible nanowire electrode in practical applications. Herein, a simple alcohol‐based solution approach is proposed to weld crossed silver nanowires by chemically growing silver “solder” at the junctions of the nanowires, forming transparent silver nano‐network electrodes with improved electrical conductivity and operational stability. Remarkably, silver nano‐networks can be rapidly formed by this simple approach under ambient condition and room temperature, requiring no assistance from heat, light, electrical current, or mechanical pressure. Furthermore, our results show that the nano‐network electrode formed from large diameter nanowires offers a better operational stability, whose trend is opposite to that of the untreated electrodes. To demonstrate the potential application of the highly stable silver nano‐network from large diameter nanowires, organic solar cells fabricated on the nano‐network electrode incorporated with silicon dioxide nanoparticles achieve comparable performance to the ITO control device. Consequently, strategy demonstrated in this work can contribute to low‐cost and highly stable transparent electrodes in emerging flexible optoelectronics.     

基于字符注意力的自然场景文本识别

自然场景文本识别中采用固定大小的卷积核提取视觉特征,后仅进行字符分类的方法,其全局建模能力弱且忽视了文本语义建模的重要性,因此,本文提出一种基于字符注意力的自然场景文本识别方法。首先构建不同于卷积网络的多级efficient Swin Transformer提取特征,其可使不同窗口的特征进行信息交互;其次设计了字符注意力模块(character attention module, CAM),使网络专注于字符区域的特征,以提取识别度更高的视觉特征;并设计语义推理模块(semantic reasoning module, SRM),根据字符的上下文信息对文本序列进行建模,获得语义特征来纠正不易区分或模糊的字符;最后融合视觉和语义特征,分类得到字符识别结果。实验结果表明,在规则文本数据集IC13上识别准确率达到了95.2%,在不规则的弯曲文本数据集CUTE上达到了85.8%,通过消融及对比实验证明了本文提出的方法可行。     

Ta2O5及Nb2O5掺杂NdAlO3-CaTiO3陶瓷的介电性能研究

采用固相反应法制备0.3NdAlO3-0.7CaTiO3(CTNA)介质陶瓷。研究了Ta2O5及Nb2O5掺杂对所制CTNA陶瓷性能的影响。结果表明：Nb2O5和Ta2O5掺杂后,CTNA陶瓷的氧空位缺陷减少,显微结构改善,介电常数提高、介质损耗降低。同时加入质量分数w(Nb2O5)为0.1％,w(Ta2O5)为0.8...     

选区激光熔化成型悬垂面质量的影响因素分析

悬垂结构是选区激光熔化成型存在的固有几何限制,其容易导致成型件形状与尺寸精度变差。为了掌握悬垂面成型出现缺陷的原因,在自主研发的选区激光熔化成型设备上,采用316L不锈钢粉末,进行了高速与低速条件下成型不同倾斜角度和不同扫描线长度的悬垂结构实验。结果表明,倾斜角越小和扫描速度越小,翘曲变形越严重,理论分析了最小成型角度与可靠成型角度分别与高速扫描、低速扫描的实验结果吻合。高速扫描可成型具有最小成型角度的悬垂面,而低速扫描下只能成型可靠成型角度的悬垂面。悬垂面沿着长线扫描方向更容易发生翘曲变形。通过对悬垂面进行局部成型参量控制,可以明显改善成型质量。本研究从工艺与设计的角度为选区激光熔化技术成型悬垂面提供了依据,并给出了初步解决方法。     

Dynamic Control Over Electronic Transport in 3D Bulk Nanographene via Interfacial Charging

Electrochemical surface charge‐induced variation of physical properties in interface‐dominated bulk materials is a rapidly emerging field in material science. The recently developed three‐dimensional bulk nanographene (3D‐BNG) macro‐assemblies with ultra‐high surface area and chemical inertness offer new opportunities in this area. Here, the electronic transport in centimeter‐sized 3D‐BNG monoliths can be dynamically controlled via electrochemically induced surface charge density. Specifically, a fully reversible variation in macroscopic conductance up to several hundred percent is observed with ≤1 V applied gate potential. The observed conductivity change can be explained in the light of the electrochemically‐induced accumulation or depletion of charge carriers in combination with a large variation in the carrier mobility; the latter, being highly affected by the defect density modulations resulting from the interfacial charge injection, sharply decreases with an increase in defect concentrations. The phenomenon presented in this study is believed to open the door to novel applications of bulk graphene materials such as, for example, low voltage and high power tunable resistors.     

Design of a high-order single-loop Σ△ ADC followed by a decimator in 0.18μm CMOS technology

This work presents an oversampled high-order single-loop single-bit sigma–delta analog-to-digital converter followed by a multi-stage decimation filter.Design details and measurement results for the whole chip are presented for a TSMC 0.18μm CMOS implementation to achieve virtually ideal 16-b performance over a baseband of 640 kHz.The modulator in this work is a fully differential circuit that operates from a single 1.8 V power supply. With an oversampling ratio of 64 and a clock rate of 81.92 MHz,the modulator achieves a 94 dB dynamic range. The decimator achieves a pass-band ripple of less than 0.01 dB,a stop-band attenuation of 80 dB and a transition band from 640 to 740 kHz.The whole chip consumes only 56 mW for a 1.28 MHz output rate and occupies a die area of 1×2 mm^2.