基于蛙跳改进算法的无线传感器网络定位*

针对无线传感器网络（WSNs）定位过程当中传统的DV‐Hop定位算法在计算锚节点与未知节点之间的平均跳距时存在较大误差的问题,论文根据蛙跳算法（S FL A ）计算速度快,全局搜索寻优能力强的优势,结合定位的实际问题,提出了一种改进的蛙跳算法。并将其引入到DV‐Hop的算法设计中,实现节点的定位。     

基于Tourweaver的虚拟校园漫游系统

针对公共环境的引导介绍,以某校园为例,本文介绍了利用球面全景图开发网上虚拟校园的方法,对全景漫游技术进行了研究,实现了虚拟全景系统．讲述了全景拍摄时节点的调整方法,并通过规范全景设计一系列流程来完成全景图的拼接．用Tourweaver软件将全景图导入,通过添加地图、热点、雷达等元素把漫游系统制作成视频格式进行发布．漫游系统具有界面简洁、功能实用的特点,使用户一目了然．     

Miscibility behavior and coil overlap in ionic blends of phenylated polytriphenylene oxide and poly(methyl methacrylate)

Blends of sulfonated phenylated polytriphenylene oxide and poly(methyl methacrylate‐co‐4‐vinyl pyridine) were examined by dynamic mechanical, Fourier transform infrared, and NMR techniques. A high degree of miscibility was evident from a single drop in a plot of the storage modulus versus the temperature. The presence of ionic moieties due to proton transfer from sulfonic acid to 4‐vinyl pyridine was confirmed by both NMR and IR spectroscopy studies. The coils were found to be close to one another in dimethyl sulfoxide‐d₆ because the aromatic shielding effect of the phenyl rings of the phenylated polytriphenylene oxide units was observed from the upfield shift of most of the protons of poly(methyl methacrylate) in the NMR spectrum. However, the absence of cross peaks in the nuclear Overhauser and exchange spectroscopy experiments suggested that the intermolecular distance between the chains had to be larger than 4 Å. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 728–733, 2003     

一种基于分簇的3D-RSSI的定位算法

节点定位是无线传感器网络的重要支撑技术之一,本文提出了一种适用于大规模无线传感器网络的分布式分簇定位算法。相比于集中式算法而言,本文提出的分簇式算法更适用于大规模无线传感器网络,不仅算法的复杂度低,而且通信量小,鲁棒性较好。在三维空间中随机分布节点,仿真结果表明,本文所提出的算法能取得较好的定位效果。     

Molecular orientation and relaxation in poly(butylene terephthalate)/polycarbonate blends

Rheo-optical Fourier-transform infrared (FTIR) spectroscopy is based on the simultaneous acquisition of stress-strain data and FTIR spectra on-line to the mechanical treatment of polymers and is frequently applied for the characterization of transient structural changes during deformation and stress-relaxation. In the present communication, this technique has been employed in order to investigate the distribution of molecular orientation and its relaxation in uniaxially drawn solution-cast films of semicrystalline partial miscible blends of poly(butylene terephthalate) (PBT) with polycarbonate (PC) containing 10, 30 and 50 wt% PC. The uniaxial deformation of these blend films having a PBT-crystallinity degree ranging from 31 to 12%, in unstretched blends, leads to a appreciable high segmental orientation for the crystalline PBT due to a structural transformation from lamellae to microfibrils. The formation of this fibrillar structure is attributed to non-reversibility of an extended phase with all-trans conformational sequence of the aliphatic segments of PBT, occurring during elongation. The rate of relaxation of this conformational transition, however, increases with increasing amorphous content in the blends. Also it is observed that even with increasing amorphous content in the PBT/PC blends the crystalline PBT shows significant orientation. In such cases, apart from the few lamellae which transform to microfibrils, it is suggested that a stress induced transformation of PBT chains in amorphous PBT-component to irreversible all-trans extended crystalline form also contributes to PBT crystalline orientation. In contrast with this high crystalline orientation, the amorphous PBT located in the interlamellar regions inside the PBT-spherulites show a lower orientation in blends as compared in pure PBT.On the other hand, an overall segmental orientation of PC chains in blends is of lower order which is attributed mainly to low stretching temperature compared to T_g of pure PC. The results are discussed in terms of the resulting spherulitic morphology and the temporary network formed by the elongated PBT and PC chains inside the interlamellar regions, in blends.     

Diffuse reflectance fourier transform infrared spectroscopy of phospholipid adsorption onto silicic acid

Diffuse reflectance Fourier transform infrared spectroscopy was used to study the mode of adsorption of phosphatidylcholine (PC) in hexane onto silicic acid (SA). PC adsorption was mainly through the charged phosphate group with minimal binding through the ester carbonyl. When the SA surface with adsorbed PC is washed with hexane, containing a small concentration of isopropanol, the desorbed PC is recovered without structural change, i.e., there is no evidence of PC hydrolysis in the adsorption process. Adsorbent misture probably promotes PC adsorption due to the increased availability of surface water hydroxyl groups for interaction with the PC phosphate groups. Isopropanol promoted PC binding by destabilizing PC reverse miscelles in solution, thus promoting its adsorption.     

Mullite for Structural, Electronic, and Optical Applications

Mullite (3Al₂O₃·2SiO₂) is becoming increasingly important in electronic, optical, and high-temperature structural applications. This paper reviews the current state of mullite-related research at a fundamental level, within the framework of phase equilibria, crystal structure, synthesis, processing, and properties. Phase equilibria are discussed in terms of the problems associated with the nucleation kinetics of mullite and the large variations observed in the solid-solution range. The incongruent melting behavior of mullite is now widely accepted. Large variations in the solid solubility from 58 to 76 mol% alumina are related to the ordering/disordering of oxygen vacancies and are strongly coupled with the method of synthesis used to form mullite. Similarly, reaction sequences which lead to the formation of mullite upon heating depend on the spatial scale at which the components are mixed. Mixing at the atomic level is useful for low-temperature (<1000°C) synthesis of mullite but not for low-temperature sintering. In contrast, precursors that are segregated are better suited for low-temperature (1250° to 1500°C) densification through viscous deformation. Flexural strength and creep resistance at elevated temperatures are significantly affected by the presence of glassy boundary inclusions; in the absence of glassy inclusions, polycrystalline mullite retains >90% of its room-temperature strength to 1500°C and displays very high creep resistance. Because of its low dielectric constant, mullite has now emerged as a substrate material in high-performance packaging applications. Interest in optical applications mainly centers on its applicability as a window material within the mid-infrared range.     

Fatty acid composition of spanish shortenings with special emphasis on <Emphasis Type="Italic">trans</Emphasis> unsaturation content as determined by fourier transform infrared spectroscopy and gas chromatography

A Fourier transform infrared spectroscopic procedure was used to analyze 34 edible fats (22 shortenings and 12 vegetable margarines) as neat fats (IR_NF) to determine their total trans fatty acid (TFA) content. The sloping baseline was corrected with a reference spectrum based on a nonprocessed olive oil. The calibration was done using seven partially hydrogenated fats with an individual TFA content previously determined by the combination of gas chromatography (GC) with argentation thin-layer chromatography. Taking into account the different absorptivities of various trans isomers, different correction factors were calculated using the calibration standards (0.83 and 1.71 for single trans bonds in both diethylene and triethylene and for trans, trans-diethylene fatty acids, respectively) and applied to calculate the total TFA of samples. Moreover, the samples were converted to their methyl esters and reanalyzed following the same procedure (IR_FAME). Differences in TFA content of fats were not found when a t-test was used to compare the results obtained by IR_NF vs. either IR_FAME or GC, suggesting that IR of neat fats could be used, thus avoiding the need to prepare sample solutions in organic solvents and to prepare fatty acid methyl esters. The mean TFA content (determined by IR_NF) of a representative group of Spanish shortenings (22 samples) that varied widely in terms of fat sources, processes, and purposes (bakery, sandwiches, ice cream, coatings, chocolate coverings) was 6.55±11.40%, although more than 54% contained <3% of TFA. Fatty acid composition of shortenings by direct GC using a 100-m polar cyanopolysiloxane capillary column indicated that the mean trans-18∶2 isomer content was 0.58%, ranging from 0.9 to 3.4%. Small amounts of trans-18∶3 isomers (<0.3%) were observed in 18 of the 22 shortenings studied; the maximal value was <2%. The mean value of the fraction saturated+TFA of shortenings was high (59.95±12.73%), including two values higher than 83%.     

基于红外偏振的入射角确定

提出基于红外光的偏振度来确定透明物体形状检测中的入射角的方法。在可见光域,偏振度是入射角的二阶函数,即在布儒斯特角两侧各有一个入射角,不能唯一确定入射角。而在红外域,偏振度与入射角之间是一一对应关系,可以对可见光域的两个入射角做出区分,得到正确的入射角。这种方法提高了透明物体形状检测的精度,还可用于复杂形状的物体检测。     

大跨度钢桁拱桥节点疲劳性能试验研究

重庆朝天门大桥是当今世界第一大跨度拱桥,其下弦节点直接承受公路荷载与轻轨荷载的双重作用,下弦节点连接处应力幅大,目前大跨度钢桥中未曾有类似的设计及试验,因此,该文对其下弦节点连接进行了高周疲劳试验以确定其连接的可靠性。首先通过相关规范及朝天门大桥的交通量确定出模型的试验荷载,并完成从实桥节点到模型的转换,然后对模型进行正常设计荷载下的200万次疲劳试验,该试验验证了设计寿命期内朝天门大桥节点连接的安全性,并用空间有限元分析结果验证了试验数据的真实性。最后进行了该模型的疲劳破坏试验,得出了这类节点的疲劳破坏规律,为该类桥梁以后的设计及监测提供了数据及参考意见。