The relationship between enhanced dielectric property and structural distortion in Ca doped Ba2NaNb5O15 tungsten bronze ceramics

The relationship between enhanced dielectric property and structural distortion in tungsten bronze structure ceramics was discussed in this work. The ceramics with the composition of (Ba_1-xCa_x)₂NaNb₅O₁₅ (x = 0, 0.1, 0.2, 0.3, 0.4) were fabricated via conventional solid-state method. All ceramics were pure without secondary phase and the distinct lattice distortion in structure was testified by Rietveld XRD refinement. Compared with the un-doped composition, the maximum polarization and energy storage density were strongly enhanced according to the ferroelectric property measurements, which were contributed to the distortion of NbO₆ octahedron induced by the variation of ionic radius. The actually pulsed charge-discharge property of x = 0.3 ceramic was tested, whist excellent power density (P_D = 35.106 MV/cm³) and discharge energy density (W_d = 0.29 J/cm³) were obtained at 100 °C under 120 kV/cm, revealing the potential for application of Ba₂NaNb₅O₁₅ system-based ceramics in harsh environment.     

Structural hierarchy developed in injection molding of nylon 6/clay/carbon black nanocomposites

The influence of platelet-type clay nanoparticle (nanoplatelet) on the structural evolution in injection-molded nylon 6)/carbon composites was investigated. In the absence of nanoplatelets, the nylon 6/CB systems were found to exhibit unoriented structure with nylon 6 crystalline regions exhibiting exclusively α crystal form throughout the thickness of the samples. However, inclusion of nanoplatelets induces substantial local orientation of the nylon 6 chains in the molded parts in all processing conditions and compositions. In these clay/nylon 6/CB ternary nano systems, nylon 6 matrix was found to be exclusively in γ crystal form at the skin regions and α crystal form fraction increases towards the core of the molded parts as a result of decrease in cooling rate with depth during the solidification stage. Two nanoplatelet orientation behaviors were identified: (i) in the absence of irregular shaped CB, the nanoplatelets align parallel with one another following the local flow patterns. The latter behavior also causes enhanced orientation of the nylon 6 chains undergoing substantial shear amplification trapped in between the nanoplatelets (ii) in the CB-enriched regions, nanoplatelets though still remaining parallel to one another, are randomized by following the local contours of irregular shaped CB aggregates. These CB aggregates themselves were found to organize to form trains in larger scale as a result of flow alignment.     

基于神经网络的机械结构系统优化问题的分解算法

基于前馈神经网络的权重分析，针对优化问题提出了一种分解算法，探讨了神经网络在桁架结构系统优化中的应用。实例分析表明此方法是可行和有效的。     

3-PRUR三平移并联机构位置计算

根据并联机器人机构结构综合理论,构造出一种新型的具有三平移的3自由度并联机器人机构。建立了运动学模型,分析了该机构的运动特性和运动学正反解。简单的运动学反解模型为该机构作进一步的运动学动力学及优化设计研究打下了基础。     

计算区带油气聚散量的物质平衡方法

区带油气聚散是一个多因素的、极为复杂的地质历史过程,油气的最终聚集量更是人们极为关注的问题。本文提出一整套实用的油气聚集、散失量计算方法:区带供油气计算;油在运载层中残留量计算;气在运载层中被岩石吸附量计算;气在储集层中扩散量计算。通过对比供油气量、油气总散失量及圈闭容积三者的关系,建立起计算区带油气聚集量平衡方程,从而为盆地数值模拟的软件设计及油气资源评价提供一条切实可行的途径。     

An experimental study on the concrete hydration process using Fabry–Perot fiber optic temperature sensors

This paper describes the contribution of Fabry–Perot (FP) fiber optic temperature sensor to investigate the effects of concrete hydration process. The FP temperature sensor was easily fabricated by controllable chemical etching and adjustable fusion splicing. Detailed optical properties of the sensor were theoretically analyzed and temperature calibration experiments were performed. A sensor with a 90 μm cavity length was demonstrated to have a temperature sensitivity of 0.01 nm/°C and the linearity coefficient of 0.99. Furthermore, the FP sensor was embedded in the concrete structure for sensing the temperature change during the early age of hydration. During the concrete hydration experiments, the measured peak temperatures of the concrete specimens with different water-to-cement (w/c) ratios of 0.4, 0.5 and 0.6 were 51.42 °C, 52.88 °C, and 55.08 °C, respectively, corresponding to final setting times of 13.52 h (w/c = 0.4), 14.16 h (w/c = 0.5) and 15.2 h (w/c = 0.6) after concrete casting. Temperature profiles will be used for concrete hydration heat study, which will help us to have a better understanding of cement hydration behavior.     

脉冲载荷下柱壳结构响应实验研究

利用电子束及化爆对柱壳模拟结构进行脉冲加载，通过试验研究结构响应规律及结构破坏阈值，对壳体结构响应的基本理论进行了论述和分析；根据电子束及化爆加载实验结果，重点分析了不同结构的破坏阈值；提出了提高柱壳壳体抗脉冲载荷能力的技术途径。     

辽河和胜利焦化蜡油组成的初步研究

研究了辽河、胜利焦化蜡油的组成，考察了硫、氮、残炭在焦化蜡油中的分布，采用改进的Ｂ－Ｌ法、ｎ－ｄ－Ｍ法计算了辽河、胜利焦化蜡油的结构参数，并与大庆焦化蜡油文献数据进行了比较，讨论了焦化蜡油中氮对掺炼的影响。     

Lower bounds on sample size in structural equation modeling

Computationally intensive structural equation modeling (SEM) approaches have been in development over much of the 20th century, initiated by the seminal work of Sewall Wright. To this day, sample size requirements remain a vexing question in SEM based studies. Complexities which increase information demands in structural model estimation increase with the number of potential combinations of latent variables; while the information supplied for estimation increases with the number of measured parameters times the number of observations in the sample size – both are non-linear. This alone would imply that requisite sample size is not a linear function solely of indicator count, even though such heuristics are widely invoked in justifying SEM sample size. This paper develops two lower bounds on sample size in SEM, the first as a function of the ratio of indicator variables to latent variables, and the second as a function of minimum effect, power and significance. The algorithm is applied to a meta-study of a set of research published in five of the top MIS journals. The study shows a systematic bias towards choosing sample sizes that are significantly too small. Actual sample sizes averaged only 50% of the minimum needed to draw the conclusions the studies claimed. Overall, 80% of the research articles in the meta-study drew conclusions from insufficient samples. Lacking accurate sample size information, researchers are inclined to economize on sample collection with inadequate samples that hurt the credibility of research conclusions. Guidelines are provided for applying the algorithms developed in this study, and companion software encapsulating the paper’s formulae is made available for download.     

网络管理信息系统安全对策探索

网络管理信息系统的应用越来越广泛，这时网络管理信息的安全提出了更高的要求，本文针对网络管理信息系统的特点，提出了一个网络管理信息系统的安全结构模型，分析了相应的安全对策。