Synthesis of a benzoxazine with precisely two phenolic OH linkages and the properties of its high‐performance copolymers

A phenolic OH‐containing benzoxazine ( F‐ap ), which cannot be directly synthesized from the condensation of bisphenol F, aminophenol, and formaldehyde by traditional procedures, has been successfully prepared in our alternative synthetic approach. F‐ap was prepared by three steps including (a) condensation of 4‐aminophenol and 5,5'‐methylenebis(2‐hydroxybenzaldehyde) (1) , (b) reduction of the resulting imine linkage by sodium borohydride, and (c) ring closure condensation by formaldehyde. The key starting material, (1) , was prepared from 2‐hydroxybenzaldehyde and s‐trioxane in the presence of sulfuric acid. F‐ap is structurally similar to bis(3,4‐dihydro‐2H‐3‐phenyl‐1,3‐benzoxazinyl)methane ( F‐a, a commercial benzoxazine based on bisphenol F/aniline/formaldehyde) except for two phenolic OHs. The phenolic OHs can provide reaction sites with epoxy and 1,1'‐(methylenedi‐p‐phenylene)bismaleimide (BMI). The structure–property relationships between the thermosets of F‐ap /epoxy, F‐a /epoxy, F‐ap /BMI, and F‐a /BMI were discussed. Experimental data showed that thermosets based on F‐ap /epoxy and F‐ap /BMI provided much better thermal properties than those based on F‐a /epoxy and F‐a /BMI. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2686–2694     

A flip-chip packaged 80-nm In0.7Ga0.3As MHEMT for millimeter-wave low-noise applications

In this paper, we present a flip-chip 80-nm In_0.7Ga_0.3As MHEMT device on an alumina (Al₂O₃) substrate with very little decay on device RF performance up to 60 GHz. After package, the device exhibited high I_DS = 435 mA/mm at V_DS = 1.5 V, high g_m = 930 mS/mm at V_DS = 1.3 V, the measured gain was 7.5 dB and the minimum noise figure (NF_min) was 2.5 dB at 60 GHz. As compared to the bare chip, the packaged device exhibited very small degradation in performance. The result shows that with proper design of the matching circuits and packaging materials, the flip-chip technology can be used for discrete low noise FET package up to millimeter-wave range.     

A Design of Linearity Built-in Self-Test for Current-Steering DAC

In this paper, a current-mode Built-In Self-Test (BIST) scheme is proposed for on-chip estimating static non-linearity errors in current-steering digital-to-analog converters (DACs). The proposed DAC BIST scheme is designed to verify a 10-bit segmented current-steering DAC, consist of a 5-bit coarse DAC and a 5-bit fine one. This proposed BIST scheme includes a current-mode sample-and-difference circuit to increase the sampling current accuracy and control a current-controlled oscillator (ICO). In addition, only 36 measurements are required by using the selected-code method rather than 1024 measurements for the conventionally-utilized all-code method. Compared to the conventionally-utilized all-code method, about 85-% reduction of test time can be achieved.     

Characteristic of copper wire and transient analysis on wirebonding process

In the present paper, two major analyses are achieved. In the first, experimental procedures were accomplished to measure tensile mechanical properties of copper (Cu) wire (? = 1 mil) before/after electric flame-off (EFO). Characteristics of free air ball (FAB), heat affected zone (HAZ) and thermal stable zone (TSZ) in as-drawn wire have been carefully investigated by microhardness, self-design pull test fixture, nanoindentation and atomic force microscopy (AFM). A 2nd EFO real-time technique has been conducted to reduce the strength of Cu wire and increase the bonding region. Secondary, with the obtained experimental material data, a comprehensive finite element wirebonding model based on explicit time integration software ANSYS/LS-DYNA is developed to predict the overall strain/stress distributions on the aluminum (Al) bond pad. Finite element analysis (FEA) results demonstrate that plastic deformation on Al bond pad around smashed FAB can be reduced by increasing the surface roughness on FAB. A series of comprehensive parametric studies were conducted in this research.     

Improving an LDMOST by variation of lateral doping on epitaxial-layer drift region

Variation of lateral doping (VLD) is applied to the epitaxial-layer drift region in LDMOSTs, resulting in non-uniform doping concentration. In addition to a decrease in on-resistance, it improves electric field distribution on the surface of drift region, and thus increases the breakdown voltage. We studied the condition of using the VLD technique, and compared it with the conventional technique of optimizing the epitaxial-layer uniform concentration. Results from TSPUREM 4 and MEDICI simulations indicate that when the epitaxial-layer doping concentration is 1.5 × 10¹⁵ cm⁻³, applying VLD to the drift region increases the breakdown voltage by as much as 34% (187-251 V), while the specific on-resistance is lowered by 55% (49-22 mΩ cm²), which are remarkable improvements. On the other hand, if the doping concentration of epitaxial-layer is already high, the improvement of applying VLD is limited.     

A Composite Formation Route to Well‐Crystalline Manganese Oxide Nanocrystals: High Catalytic Activity of Manganate–Alumina Nanocomposites

Manganese oxide nanocrystals are combined with aluminum oxide nanocrystals to improve their crystallinity via calcination without a significant increase of crystal size. A nanocomposite, consisting of two metal oxides, can be synthesized by the reaction between permanganate anions and aluminum oxyhydroxide keggin cations. The as‐prepared manganese oxide–aluminum oxide nanocomposite is X‐ray amorphous whereas heat‐treatment gives rise to the crystallization of an α‐MnO₂ phase at 600 °C and Mn₃O₄/Mn₂O₃ and γ‐Al₂O₃ phases at 800 °C. Electron microscopy and N₂ adsorption‐desorption‐isotherm analysis clearly demonstrate that the as‐prepared nanocomposite is composed of a porous assembly of monodisperse primary particles with a size of ～20 nm and a surface area of >410 m² g^?1. Of particular interest is that the small particle size of the as‐prepared nanocomposite is well‐maintained up to 600 °C, a result of the prevention of the growth of manganate grains through nanoscale mixing with alumina grains. The calcined nanocomposite shows very‐high catalytic activity for the oxidation of cyclohexene with an extremely high conversion efficiency of >95% within 15 min. The present results show that the improvement of the crystallinity without significant crystal growth is very crucial for optimizing the catalytic activity of manganese oxide nanocrystals.     

无人机载激光线扫描浅滩三维成像研究

设计了一种基于三角法线扫描的无人机载激光雷达三维成像系统。系统以520 nm线激光为光源照射目标,利用无人机扫描获取目标的三维数据。文章设计了无人机载激光线扫描系统的硬件系统,构建了线激光水下折射三维坐标解算模型,提出了水上、水面与水下激光条纹提取的图像处理方法,并利用研制的雷达系统进行了近海浅水区域无人机扫描实验。实验结果表明,系统利用IMU及GPS能够有效提升三维图像的准确性,快速获取目标区域水上及水下目标的三维数据,平均距离分辨率达到3 cm,具有速度快、精度高、成本低的优势,在近岸浅海区域的大范围高速三维成像领域具有广阔的应用前景。     

硒化锌基底8μm～12μm高效高稳定性减反射膜的研究

文中讨论了硒化锌基底上的高效高稳定性红外减反射膜的设计与制备。介绍了离子束辅助沉积该膜系的过程,给出了用该方法制备的8μm-12μm波段宽带减反射膜的实测光谱曲线,其峰值透过率高达99％以上,在设计波段范围内平均透过率大于98％,膜层附着性能好,光机性能稳定。     

An Information Hiding Algorithm Based on Bitmap Resource of Portable Executable File

An information hiding algorithm is proposed, which hides information by embedding secret data into the palette of bitmap resources of portable executable （PE） files. This algorithm has higher security than some traditional ones because of integrating secret data and bitmap resources together. Through analyzing the principle of bitmap resources parsing in an operating system and the layer of resource data in PE files, a safe and useful solution is presented to solve two problems that bitmap resources are incorrectly analyzed and other resources data are confused in the process of data embedding. The feasibility and effectiveness of the proposed algorithm are confirmed through computer experiments.