Inserting a Mn-doped TiO2 layer for improving performance of pentacene organic thin-film transistors

Device performance of pentacene organic thin-film transistors (OTFTs) was significantly improved via inserting a Mn-doped TiO₂ layer between pentacene semiconductor and the source–drain electrodes. In comparison with the OTFTs with only-Au electrodes, the introduction of a thin Mn-doped TiO₂ layer leads to saturation current increasing from 31.9 μA to 0.22 mA, effective field-effect mobility improving from 0.24 to 1.13 cm²/V s, and threshold voltage downshifting from −11 to −2 V. These performance enhancements are ascribed to the significant reduction of contact resistance and smoothed surface of pentacene layer. This work may provide an effective approach to improve the performance of the pentacene based OTFTs by inserting a Mn-doped TiO₂ layer.     

The nonlinear dynamic response of microbeam of MEMS capacitive switch under mechanical shock

The microelectromechanical system (MEMS) capacitive switch based on clamped?Cclamped microbeam has garnered significant attention due to their geometric simplicity and broad applicability, and the accurate model which describes the multiphysical effects of MEMS capacitive switch should be developed to predict the nonlinear dynamic response of clamped?Cclamped microbeam. A improved macromodel of the clamped?Cclamped microbeam-based MEMS capacitive switch is presented to investigate the nonlinear dynamic response of clamped?Cclamped microbeam of MEMS capacitive switch under different mechanical shock in this article, the macromodel provides an effective and accurate design tool for this class of MEMS devices because of taking account into some effects simultaneously including midplane stretching effect, residual stress and different mechanical shock loads. A numerical analytical method based on multimode Galerkin discretization is presented to investigate the nonlinear response of clamped?Cclamped microbeam of MEMS capacitive switch under the different mechanical shock loads. The results show that using five or more modes can be sufficient to capture the nonlinear dynamic response of clamped?Cclamped microbeam, and the microbeam experiences a mechanical shock load as a quasi-static load or a dynamic load depending on the ration between the natural periods of the structure and the period or frequency of mechanical shock load. The proposed method gives the identical results to other numerical methods in the literature. Moreover, this method is straightforward to implement and could save computation efforts while not losing accuracy.     

电信运营企业综合竞争力比较研究——中国联通视角评价分析

经济全球化以及世界信息产业的持续增长决定了电信市场正走向全球竞争.本文基于竞争力相关理论,采用定性与定量分析相结合,围绕财务运作能力、客户发掘能力、资源利用能力、企业成长能力等4个维度,利用3层架构建立30个具体指标来衡量电信运营企业竞争力水平.相互比较中研究中国联通与国内外著名电信运营企业的经营状况.探讨中国联通竞争力提高途径和策略,为电信运营企业管理实践提供了有效的操作思路.     

Radio Resource Allocation in Multi-User Cooperative Relaying Networks with Resource Block Pairing and Fairness Constraints

In this paper we address the problem of radio resource allocation in cooperative relaying networks. We focus on the resource block and power allocations for the downlink of OFDM-based relaying multi-user network. The resource allocation is investigated for both amplify and forward and decode and forward protocols under the constraints of power, resource block pairing and data rate fairness. To reduce complexity, the optimization problem is solved in two steps. In the first step, resource block pairing and allocation are conducted jointly with equal transmission power for both the base station and the relay. In the second step, transmission power is further optimized to maximize the system throughput. Our analysis is focused on the total achievable system throughput and the achievable individual throughput for each user.     

High‐Performance Organic Transistor Memory Elements with Steep Flanks of Hysteresis

High‐performance organic transistor memory elements with donor‐polymer blends as buffer layers are presented. These organic memory transistors have steep flanks of hysteresis with an ON/OFF memory ratio of up to 2 × 10⁴, and a retention time in excess of 24 h. Inexpensive materials such as poly(methyl methacrylate), ferrocene and copper phthalocyanine are used for the device fabrication, providing a convenient approach of producing organic memory transistors at low cost and high efficiency.     

Multifunctional Fluorene‐Based Oligomers with Novel Spiro‐Annulated Triarylamine: Efficient,Stable Deep‐Blue Electroluminescence,Good Hole Injection,and Transporting Materials with Very High Tg

A series of fluorene‐based oligomers with novel spiro‐annulated triarylamine structures, namely DFSTPA, TFSTPA, and TFSDTC, are synthesized by a Suzuki cross‐coupling reaction. The spiro‐configuration molecular structures lead to very high glass transition temperatures (197–253 °C) and weak intermolecular interactions, and consequently the structures retain good morphological stability and high fluorescence quantum efficiencies(0.69–0.98). This molecular design simultaneously solves the spectral stability problems and hole‐injection and transport issues for fluorene‐based blue‐light‐emitting materials. Simple double‐layer electroluminescence (EL) devices with a configuration of ITO/TFSTPA (device A) or TFSDTC (device B)/ TPBI/LiF/Al, where TFSTPA and TFSDTC serve as hole‐transporting blue‐light‐emitting materials, show a deep‐blue emission with a peak around 432 nm, and CIE coordinates of (0.17, 0.12) for TFSTPA and (0.16, 0.07) for TFSDTC, respectively, which are very close to the National Television System Committee (NTSC) standard for blue (0.15, 0.07). The maximum current efficiency/external quantum efficiencies are 1.63 cd A^?1/1.6% for device A and 1.91 cd A^?1/2.7% for device B, respectively. In addition, a device with the structure ITO/DFSTPA/Alq₃/LiF/Al, where DFSTPA acts as both the hole‐injection and ‐transporting material, is shown to achieve a good performance, with a maximum luminance of 14 047 cd m^?2, and a maximum current efficiency of 5.56 cd A^?1. These values are significantly higher than those of devices based on commonly usedN,N′‐di(1‐naphthyl)‐N,N′‐diphenyl‐[1,1′‐biphenyl]‐4,4′‐diamine (NPB) as the hole‐transporting layer (11 738 cd m^?2 and 3.97 cd A^?1) under identical device conditions.     

温室大棚环境监测及控制系统的设计

我国是农业种植大国,针对传统温室大棚人工成本高、管理效率低下的问题,本文设计了一种温室大棚环境监测及控制系统,实现了对温室大棚内环境的实时监测和远程管理。该系统以STM32L4为主控芯片,通过NB-IOT无线通信模块入网,设备对接华为OceanConnect物联网开发平台,管理人员通过登录平台实现对监测终端的远程管理。测试表明,该系统系统工作稳定、可靠性较强、性价比优势更为明显,对农作物的信息化种植提供了较好的参考。     

Oligotriphenylene Nanofiber Sensors for Detection of Nitro‐Based Explosives

Blue light‐emitting oligotriphenylene nanofibers are synthesized by oxidizing triphenylene using ferric chloride. By adjusting the monomer concentration, the acid used, and the temperature employed, the average diameter and length of the nanofibers can be readily tuned from 50 to 200 nm and 0.5 to 5 μm, respectively. Structural characterization, electrical conductivity, thermal stability, and fluorescence of oligotriphenylene, along with a proposed nanofiber formation mechanism, are presented. Both oligotriphenylene nanofiber dispersions and oligotriphenylene/polysulfone composite films are developed as fluorescent sensors for detecting traces of nitro‐based explosives including nitromethane, nitrobenzene, and 2,4,6‐trinitrophenol, as well as an electron‐deficient metal ion, Fe(III). The sensors exhibit much better selectivity and sensitivity compared to conventional sensors, with detection limits down to 1.0 nm with a detection range covering ～4 orders of magnitude. The detection mechanism of the fluorescent sensors is also disscussed.     

An instant-switching ?–Σ fractional-N frequency synthesizer with adjustable duty cycles

A Phase-Locked Loop (PLL)-based frequency synthesizer (FS) with adjustable duty cycle is presented. By employing digital processing circuitry and the ??C?? fractional-N technique, the FS is capable of generating arbitrary frequencies in a wide frequency range, and capable of adjusting the clock duty cycles. In addition, the switching between different frequencies is instant except when a very fine frequency resolution is required. The adjustable duty cycle and instant switching are desired features in applications such as time-interleaved Analog-to-Digital-Converters (ADCs), switched-capacitor circuits, and DC?CDC converters. The design was fabricated using a 0.13???m CMOS process. This paper gives the theories, analysis, implementation, and measurement results of this FS.