硝酸、硫酸对三硝基均苯三酚热分解特性的影响

三硝基均苯三酚（TNPG）在硝化过程中不可避免地会接触到酸根离子。为了探究硝酸、硫酸作用下TNPG的热分解特性,采用差示扫描量热仪（DSC）对合适酸含量的样品在不同升温速率条件下进行测试,并进行动力学分析与预测。DSC测试结果表明,TNPG的起始分解温度为198.35 ℃,硝酸和硫酸都能促进其热分解过程,随着酸含量的增加,起始分解温度降低。无模型法计算得到TNPG的活化能变化范围为97~103 kJ/mol,而酸作用下的TNPG较不稳定,活化能为20~94 kJ/mol（硝酸作用）和135~224 kJ/mol(硫酸作用)。等温预测结果说明,各样品具有自催化分解特性;绝热预测结果表明,每个样品的T_D24分别为137.6 ℃（TNPG）、111.3 ℃（硝酸作用）和140.4 ℃（硫酸作用）。若在合成过程中发生热失控,采取控制措施的时间余量较大;需要将物质在阴凉、干燥、无酸根离子的环境中储存,避免外部火灾的发生。     

长余辉发光材料Sr4Al14O25:Eu2+,Dy3+的制备

采用化学沉淀法制备了Sr4Al14O25:Eu2 ,Dy3 蓝绿色长余辉发光粉.通过XRD分析表明:经1100℃和1200℃煅烧制得的发光粉均为单一的Sr4Al14O25晶相,不含其它任何杂相,同时研究了硼酸的加入量对发光粉的物相变化和发射光谱的影响,通过场发射扫描电子显微镜分析了粉体的形貌和粒径.     

变风量空调系统用非线性模型预测控制方法研究

在工业HVAC系统中,为了提高在大扰量下的控制精度,模型预测控制(MPC)被广泛应用。本文提出一种用于变风量(VAV)系统的非线性MPC。该非线性MPC采用具有外部输入的非线性自回归网络(NARX)和粒子群优化算法(PSO)。NARX模型旨在预测VAV系统的受控参数(室温),PSO作为优化器,来获得VAV系统的最优控制变量。通过为成本函数的目标分配不同的权值,本文提出的非线性MPC能权衡VAV系统的控制精度和节能需求,以达到不同的控制效果。不同权值的两种方案在实验室的VAV系统中得到了验证,其中方案1仅考虑控制精度,方案2同时考虑了控制精度和节能性。分别将实验得到的两种方案的MPC的控制效果与基于PI控制器的定静压方法进行对比,实验结果表明:基于MPC的方案1可以实现室温稳定在设定值±0. 5℃的控制精度范围;基于MPC的方案2显示出更好的节能特性,与定静压方法对比,节能率达到23. 7%。     

一种采用相位补偿的线谱相干检测器

分析了加窗和实信号情况下相干线谱检测器的检测性能。从频谱泄漏现象出发,通过对实信号做加窗处理,有效地降低了信号傅里叶变换后频谱泄漏的旁瓣级,提升了弱信号的探测能力;针对分段处理时同一频率不同数据段出现的相位差,采用相位补偿的方法,实现了各段数据的相干叠加。理论分析和计算机仿真表明,相比于平均功率谱检测器(Average Power Processor,AVGPR),加窗相位补偿检测器(Window Phase-Compensated Processor,WPCPR)有10 lg L(L为分段数)信噪比的提高,从而拓宽了相干线谱检测的适用范围。此外,还从频域波束形成的角度,给出了WPCPR能提高信噪比的一种物理解释,并指出了仿真中信噪比增益与理论值存在差异的原因。     

基于订阅推送的NDN实时通信机制

研究了代表未来互联网体系结构发展方向的命名数据网络(NDN)的实时通信机制。研究发现,NDN用户通过发送请求包(Interest)获得对应数据(Data),而对于实时通信类应用(如即时聊天、物联网监控等),由于数据源的数据产生存在突发性和随机性,而且存在数据接收时延,传统NDN用户驱动的"拉"模式数据获取方式,难以实现用户请求速率与数据产生速率的同步,无法满足实时通信应用需求。从减小数据接收延迟出发,在不改变原NDN路由缓存机制的基础上提出了一种基于订阅推送的NDN实时通信机制,该机制通过提前在路由器中添加订阅信息,实现实时数据源的即时推送。相关理论分析和仿真实验表明,该机制在实时数据接收延迟上明显优于传统NDN方法。     

端羧基分散剂对PS/纳米CaCO_3复合材料性能的影响

以巯基乙酸为链转移剂制备了不同分子量的含端羧基聚丙烯酸丁酯(PBACOOH)低聚物分散剂,并将其用于聚苯乙烯(PS)/纳米CaCO3复合材料的分散改性。通过动态流变仪、电子拉力机及差示扫描量热仪对复合材料性能进行表征。结果表明,PBACOOH可提高PS/纳米CaCO3复合材料的拉伸强度及缺口冲击强度,缺口冲击强度的增幅最高可达54%。含量为纳米粒子用量1%(质量分数)的PBACOOH分散剂使复合材料熔体储能模量、损耗模量及黏度下降,G′与G″的交点频率向高频方向移动。随分子量降低及端羧基含量增加,物理老化试样在Tg转变区的解缠结热焓增大。     

Spectral Method for Thermal Conductivity Calculations

We discuss several post-processing issues in molecular dynamics (MD) calculation of lattice thermal conductivity using the Green–Kubo formula. For crystals with high thermal conductivity such as SiC, converting the MD raw data on heat current fluctuations into thermal conductivity result is non-trivial. One can accelerate the process using Fast Fourier Transform and the spectral method. A few mathematical subtleties are cleared up. Due to finite data length, integration of the correlation function must be terminated before noise takes over; two termination criteria are proposed which give reasonable results for crystalline β-SiC. A simple solvable model that illustrates the above points and can be used for code-checking is presented.     

基于EMD与谱峭度的滚动轴承故障检测改进包络谱分析

针对滚动轴承故障振动信号的调制特征和传统包络分析法的缺陷,提出一种基于经验模式分解(Empirical Mode Decomposition,简称EMD)和谱峭度(Spectrum Kurtosis,简称SK)的改进包络谱滚动轴承故障诊断方法。该方法首先对滚动轴承故障振动信号进行经验模式分解,将其分解为多个固有模式函数(Intrinsic Mode Function,简称IMF)之和,然后对各IMF分量傅里叶变换后取其绝对值,并计算其谱绝对值平方包络,在此基础上再计算不同频带IMF分量谱平方包络的峭度,最后利用谱峭度的滤波器作用,选取由轴承缺陷所引起的共振频率所在频带的IMF分量,自动构建最佳包络来进行故障诊断。将该方法应用到滚动轴承内圈缺陷的仿真故障数据和实际数据中,分析结果表明了该方法的有效性。     

纳米二氧化钛的光致发光

利用改进的溶胶－凝胶法制备了锐钛矿型二氧化钛的纳米粉末（４～１５ｎｍ）,测量了ＴｉＯ２的漫反射光谱（ＤＲＳ）和光致发光谱（ＰＬ）。结果表明,ＴｉＯ２纳米微粒的光学禁带宽度为３８４ｎｍ,在２５０～４００ｎｍ的紫外光范围内有强吸收;纳米二氧化钛在波长为４２０,４６１,４８５,５３０,５７３和６０９ｎｍ有强发光带,这些发光带分别为自由激子发光、束缚激子发光以及缺陷能级和表面态引起的发光。     

Generation of transient vibrations on aluminum honeycomb sandwich panels subjected to hypervelocity impacts

This paper presents the results of a set of experiments aimed at discovering the main features of impact-induced vibrations on all-aluminum honeycomb sandwich panels, representative of the GOCE satellite's top floor, which is exposed to the orbital debris environment. The activity focused on the characterization of the vibrations induced in the vicinity of internal payloads by hypervelocity impacts occurring on the vehicle's external shell. More than 30 tests were realized by launching 0.8–2.3 mm aluminum projectiles in the velocity range 4–5.5 km/s on targets with tri-axial accelerometer assemblies mounted on both the front and rear face of the panel, at a nominal distance of 150 mm from the impact point. It was found that a hypervelocity impact produces in both the front and rear side of the sandwich panel a vibration environment which can be described through the shock response spectrum (SRS) of three different types of waves that can be distinguished on the basis of the acceleration direction: out-of-plane, in-plane longitudinal and in-plane shear. The influence of projectile mass and velocity on SRS appeared to vary with frequency, with the most significant difference in the range between ∼10³ and ∼10⁴ Hz. The results of whole experimental set were used to derive an interpolation law through standard techniques of nonlinear fit. The empirical equation obtained makes it possible to predict the near-field vibration environment produced by hypervelocity impacts with debris having given size and velocity, reproducing all the test data with an average uncertainty of ±6 dB.     

Degradation behaviour of sputtered Co–Al coatings on superalloy

Degradation behaviour of sputtered Co–Al coatings on Superni-718 substrate has been investigated. Cyclic high temperature oxidation tests were conducted on uncoated and coated samples at peak temperatures of 900 °C for up to 100 thermal cycles between the peak and room temperatures. The results showed that a dense scale formed on the coated samples during thermal cycling at the peak temperature of 900 °C. The external scale exhibited good spallation resistance during cyclic oxidation testing at both temperatures. The improvement in oxide scale spallation resistance is believed to be related to the fine-grained structure of the coating. Nanostructured Co–Al coatings on Superni-718 substrate were deposited by DC/RF magnetron sputtering. FE-SEM/EDS, AFM, and XRD were used to characterize the morphology and formation of different phases in the coatings, respectively. The Co–Al coating on superalloy substrate showed better performance of cyclic high temperature oxidation resistance due to its possession of β-CoAl phase as Al reservoir and the formation of Al₂O₃ and spinel phases such as CoCr₂O₄ and CoAl₂O₄ in scale. The oxidation results confirmed an improved oxidation resistance of the Co–Al coating on superalloy as compare to bare substrate in air at 900 °C temperature up to 100 cycles.     

全光通信网络节点功能结构研究

密集波分复用（DWDM）技术在提高传输能力的同时,还具有无可比拟的联网优势,使用光滤波器件或光开关就可构成重构性的具有联网功能的光分插复用器（OADM）,OADM和DWDM技术的结合构成了最佳的全光城域网解决方案,本文描述了全光通信网络节点功能结构,研究了以光转发器OUT和OADM为基础的各种全光网节点结构。     

硬件友好的3GPP-LTE Turbo交织器设计

研究了第三代合作伙伴计划长期演进技术(3GPP-LTE)中的二次置换多项式(QPP)交织器的硬件设计优化,提出了一种零延时、低复杂度的QPP交织器设计方案。该方案从算法层面出发简化了QPP交织器中定义的复杂运算。得益于算法优化的结果,优化后的QPP交织器能够以较低的代价映射到硬件电路上。结果表明:与一些传统方案相比,该方案设计的QPP交织器大大降低了硬件实现的复杂度,在SMIC 40nm工艺下,交织器的面积只有0.040mm~2。另外,所设计的QPP交织器具有零时延的特点,能够有效提高Turbo译码的译码效率。基于该交织器所设计的Turbo译码器能够稳定工作在400MHz下,译码速率达到572.85Mbps(10次半迭代),而译码器面积仅有0.82mm~2。