Note on disjoint blocking sets in Galois planes

In this paper, we show that there are at least cq disjoint blocking sets in PG(2,q), where c ≈ 1/3. The result also extends to some non‐Desarguesian planes of order q. © 2005 Wiley Periodicals, Inc. J Combin Designs 14: 149–158, 2006     

Suppressing Sodium Dendrites by Multifunctional Polyvinylidene Fluoride (PVDF) Interlayers with Nonthrough Pores and High Flux/Affinity of Sodium Ions toward Long Cycle Life Sodium Oxygen‐Batteries

Rechargeable sodium–oxygen (Na–O₂) batteries are of interest due to their high specific capacity, high equilibrium potential output, and the abundance of sodium resources; however, their cycle life is still very poor due to instability of electrolytes and especially the uncontrollable growth of Na dendrites. Herein, as a proof‐of‐concept experiment, a facile and low‐cost strategy is first proposed and demonstrated to effectively suppress growth of Na dendrites by using a fibrillar polyvinylidene fluoride film (f‐PVDF) with nonthrough pore as a multifunctional blocking interlayer. Unexpectedly, the f‐PVDF interlayer endows Na–O₂ battery with superior electrochemical performances, including high rate capability and long cycle life (up to 87 cycles), which is superior to those of the compact PVDF (c‐PVDF), PVDF with through pores (p‐PVDF), polyethylene oxide (PEO), and conventional polytetrafluoroethylene (PTFE) counterparts due to the following combined advantages: (1) the stronger C? F polar function groups provide a better affinity to Na ions, thus enabling a more homogeneous Na deposition than that of C? O function groups in PEO interlayer; (2) compared with c‐PVDF and p‐PVDF interlayers, f‐PVDF holds more electrolyte uptake for higher ion conductivity; (3) the good wettability of the f‐PVDF interlayer with electrolyte benefits Na dendrite suppression compared with PTFE interlayer.     

基于稀疏贝叶斯学习的时域流信号鲁棒动态压缩感知算法

块效应和未知且时变的噪声强度会降低时域流信号动态稀疏重构的性能,为解决该问题,本文基于重叠正交变换和稀疏贝叶斯学习框架,提出一种对时域流信号进行动态压缩感知的鲁棒稀疏贝叶斯学习重构算法.该算法在消除块效应的同时,能够处理噪声强度未知且时变情形下的动态稀疏重构问题,相比现有的流信号稀疏贝叶斯学习算法具有更强的抗噪鲁棒性.尽管现有的时域流信号压缩感知的有效算法并不多,但实验表明,本文算法的重构信误比和重构成功率均明显高于现有的基于稀疏贝叶斯学习的流信号重构算法和基于L1-同伦的流信号重构算法,且达到相同的重构成功率所需的观测数目少于另两种算法,计算量和运行效率则与稀疏贝叶斯学习算法相近.     

通信电台带外双频干扰预测模型与试验

当电台处于外界复杂电磁环境中,会有多种频率的干扰信号同时作用,如果信号强度足够,即便落于带外也有可能造成电台阻塞,使其接收不到有用信号而失去作战效能.带外信号造成接收机阻塞所需的能量高,利用矢量法将有用信号和干扰信号进行矢量叠加,通过推导得到相应的干扰预测模型.利用两套独立的干扰发射系统进行双频干扰试验,试验前要对试验系统进行调整,之后再分别以误码率0.1和受试电台接收不到链路测试作为临界干扰判别标准进行两次试验,试验结果表明以上模型能够预测受试设备是否达到临界干扰状态,预测误差在2dB以内,同时以上两种临界干扰标准均适用.     

Electroreduction of Molybdate Ions in Solutions Containing Ammonium Ions

An incomplete reduction of molybdate ions in solutions of pH 3.0–9.0 is shown to be accelerated by ammonium ions: a film of hydrated oxides of molybdenum in lower oxidation states forms on the cathode in their presence. Products of the incomplete reduction adsorbed at the cathode block its working surface.     

Stability and transport properties of La<Subscript>2</Subscript>Mo<Subscript>2</Subscript>O<Subscript>9</Subscript>

La₂Mo₂O₉ samples were prepared from freeze-dried powder precursors and characterized by XRD, TG/DTA, SEM, electrical and electrochemical measurements. Pellets with different density were obtained by sintering at temperatures between 900 and 1100 °C to obtain nearly dense samples with grain sizes in the range 1–8 m. The electrical conductivity was measured using impedance spectroscopy. The capacitance and relaxation frequencies of the main contributions to the spectra were used to ascribe the contributions of grain interiors and internal interfaces, and their temperature dependence. A coulometric titration technique was used to evaluate the change of oxygen stoichiometry under moderately reducing conditions, and to estimate the stability limits under strongly reducing conditions. An ion-blocking method was used to evaluate the onset of n-type conductivity, and a combination of these results with total conductivity measurements was used to obtain the ionic transport number. A combination of oxygen stoichiometry changes and ion-blocking results was used to obtain estimates of mobility.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003     

Synthesis of 5-(3-Tert-Butylamino-2-Hydroxy) Propoxy-3,4-Dihydrocarbostyril

5-(3-tert-Butylamino-2-hydroxy) propoxy-3, 4-dihydrocarbostyril ( 1 , carteolol) was prepared by an acid-catalyzed cyclization of the N-pivaloylamino-ester ( 5 ), which was obtained by using organolithiation of m-pivaloylanisidine, followed by Wittig and catalytic hydrogenation reactions. The total yield of 1 obtained from m-anisidine ( 2 ) is 21%.     

Efficient PVO-based reversible data hiding using multistage blocking and prediction accuracy matrix

In recent years, pixel value ordering based reversible data hiding has become a hot research topic for its high-fidelity. In this approach, only the maximum and minimum of pixel block are predicted and modified to embed data and the preservation of pixel values order guarantees the reversibility. So far, the optimal block size can only be exhaustively searched until Wang et al. propose the dynamic blocking strategy which enables the combination of two various-sized blocks. By further dividing flat block into four sub-blocks to retain larger embedding capacity, dynamic blocking can employ less high complexity blocks for a given embedding capacity. However, the lack of host image dependent automatic block classification mechanism still exposes the fact that their work is far from efficient and comprehensive. In this paper, to address this drawback and to better exploit image redundancy, a really efficient and more comprehensive blocking strategy namely multistage blocking is proposed. High efficiency lies in prediction accuracy matrix based thresholds determination, which enables infinitely extended multistage blocking in theory. The superiority of the proposed scheme is also experimentally verified.     

Preparation and Electrochemical Characterization of Carbonaceous Thin Layer

Current research is largely focused on the preparation of carbon complexes for eventual applications in electrochemical energy storage systems. A carbonaceous thin layer (CT) was synthesized on a fluorine‐doped tin oxide (FTO) substrate by the carbonization of glucose. The morphological image from scanning electron microscopy showed the high uniformity of CT with full coverage on the FTO substrate. The carbon content increased from 40 % in glucose to 62 % in CT by the carbonization process. Furthermore, when CT was thermally treated under a constant flow of nitrogen gas (400 °C for 9 h, CT‐9), the carbon content increased from 62 to 79 %. The proficient interaction of CT on the FTO substrate was suitable for the electrochemical characterization and application. The CT on FTO was suitable to be used as a blocking layer for the electrochemical reaction. On the other hand, the CT‐9 showed completely different electrochemical behaviors. CT‐9 showed the significantly enhanced capacitive behavior resulted from the higher porosity of CT‐9, which was electrochemically interrogated by a redox reaction of FcMeOH/FcMeOH⁺.     

建筑电气设计中的电磁兼容问题

根据作者多年来从事建筑电气设计的体会说明了建筑电气设计中电磁兼容问题的重要性,电磁污染的各种可能途径及设计中必须采取的相应措施。