中小山水城市绿地系统塑造城市特色的途径和方法

绿地是形成城市特色的重要组成部分,城市绿地系统与城市自然人文环境相结合是城市特色构建的一个重要方面。中小山水城市绿地系统规划在塑造城市特色方面具有独特的代表性。文章总结了中小山水城市的特色,提出绿地系统塑造城市特色的手法,并且以泾县为例来分析绿地系统塑造中小山水城市特色的手法。首先分析整理城市特色资源,对主要的关键词进行抽取比较,得到主要的城市特色;然后从整体出发为绿地系统定位,通过城市绿地系统结构布局强化城市山水环境;通过绿道体系的构建打造城市特色的展示体系;最后从树种规划的角度出发塑造城市的宣纸之都的城市特色.     

Chance-constrained model predictive control for spacecraft rendezvous with disturbance estimation

A robust Model Predictive Controller (MPC) is used to solve the problem of spacecraft rendezvous, using the Hill-Clohessy-Wiltshire model with additive disturbances and line-of-sight constraints. Since a standard (non-robust) MPC is not able to cope with disturbances, a robust MPC is designed using a chance-constrained approach for robust satisfaction of constraints in a probabilistic sense. Disturbances are modeled as Gaussian allowing for an explicit transformation of the probabilistic constraints into simple algebraic constraints. To estimate the distribution parameters a predictor of disturbances is proposed. Both robust and non-robust MPC control laws are compared using the Monte Carlo method, which shows the superiority of the robust MPC.     

Structure quantitative map in application for AB2X4 system

Structure maps are constructed for AB₂X₄ (A = metal, B = three-valency element and X = O, S, Se, Te) system (>490 compounds). A way to improve the resolution of the maps is proposed. Crystal structure characteristic (symmetry) is represented on a quantitative scale (coordinate axe Z). The 3D structure diagram with approximating integral plane is constructed and a field of high symmetry compounds is specified with ion radii ratio R(A)/R(X) ≈ 0.60–0.85 and R(B)/R(X) ≈ 0.55–0.70.     

Numerical simulation of hypervelocity impact on CFRP/Al HC SP spacecraft structures causing penetration and fragment ejection

A representative carbon fiber reinforced plastic/aluminum honeycomb sandwich panel (CFRP/Al HC SP) spacecraft structure has been modeled in the hydrocode AUTODYN using the state-of-the-art ADAMMO material model [Riedel W, Harwick W, White D, Clegg R. Advanced material damage models for numerical simulation codes. ESA CR(P) 4397, 2003] to study the performance of the structure during impact events that cause perforation and fragment ejection. A new procedure combining a series of existing theoretical methods has been developed and applied to derive a full set of coarse material data. The data set has been implemented in AUTODYN, and the results of the numerical simulation have been compared to experimental impact test data. For impact tests performed near the structural ballistic limit, quantitatively accurate results were obtained over a range of impact velocities and angles. A further increase in the projectile size resulted in significant destruction of the sandwich panel front face-sheet and diversion from the experimental damage measurements. Inspection of the numerical model has shown non-localized propagation of inter-laminar delaminations, possibly caused by an under-prediction of the laminate dynamic inter-laminar tensile strength. The effects of the delamination propagation occur over an extended time scale and were not found to affect the state and trends of the fragment cloud ejected into the satellite interior. Accordingly, experimental trends of fragment cloud dispersion have been qualitatively reproduced.     

A study of hypervelocity impact on cryogenic materials

This paper reports a result of hypervelocity impact experiments on cryogenically cooled aluminum alloys and a composite material. Experiments are carried out on a target palate at 122 K. Aluminum spheres at 1.95 km/s in 50 kPa air were impinged against the target plate at cryogenic temperature and the result was compared with room temperature target plates. Hypervelocity impact (HVI) processes were visualized with shadowgraph arrangement and recorded with high-speed video camera and to ensure the temperature dependence we compared HVI tests with metal target plates with AUTODYN 2D and SPH numerical simulations. We found that cryogenic impacts created slight differences of impact damage from room temperature ones, i.e., the shape and averaged diameters of HVI crater holes were less at cryogenic impacts.     

基于XC164CS微处理器的正弦脉宽调制信号的实现

把电压空间矢量的概念引入到正弦脉宽调制波形产生中,介绍了16位微处理器在正弦脉宽调制中的应用,并基于具体硬件结构利用双极性调制方法实现了正弦脉宽调制波形的生成。试验证明:本方案具有计算速度快、效率高的优点,在工程实践中切实可行。     

空间相机桁架结构模态相关性分析

为有效地预示空间相机桁架结构的动态特性，需要对其进行模态相关性分析，目的在于检验分析结果的有效性和准确度，发现结构中的薄弱部位，但由于桁架结构是一复杂的杆板组合结构，计算结果中存在着大量次模态，从而无法与试验结果进行对比。基于上述问题，提出一种利用模态应变能比值来定量区分的方法，从密集的计算模态群中识别出桁架结构的主模态。主模态经模态向量缩减后与试验结果进行比较，鉴定它们之间的总体相关程度，若误差超过规定的界限，则通过调整模型参数、修改模型构型来寻找可能的误差源，反复这一过程，直到有限元模型能够很好地模拟实际结构的主要动态特性为止。分析结果预示了较好的试验和计算模态相关性，验证了有限元模型的有效性，为进一步的响应分析和振动控制设计提供了依据。     

基于GIS的道路事故黑点聚类应用研究

由于地理信息系统中数据的多样性和空间复杂性,在GIS数据空间挖掘时原有的挖掘算法会遇到一些新问题。本文针对城市道路网中交通事故黑点发掘问题,对基于密度的DBSCAN算法进行改进,使改进后的算法能够确保聚类仅在连通空间内进行。最后以某市交通事故数据为例对该方法进行验证,实验结果表明此方法是有效的。     

IEEE802.16接收机检测模块的FPGA实现

提出了一种采用现场可编程门阵列器件FPGA实现802.16接收端MIMO(多输入多输出)2×2检测的方案。在C语言平台对基于并行干扰消除的最小均方误差的算法进行研究和仿真后,使用Verilog硬件描述语言对MIMO检测各模块分别设计;均通过了综合和验证;这样本文提出了对系统起重要作用的接收端的MIMO检测芯片的实现方法。     

室温直流反应磁控溅射制备透明导电In2O3:Mo薄膜

在室温条件下采用直流反应磁控溅射法制备了新型透明导电In2O3:Mo薄膜.研究了溅射压强中氧气百分含量[P(O2)]为8.0%～18.0%时对薄膜光电特性以及表面形貌结构的影响.结果表明,薄膜的光电性能对溅射压强中P(O2)非常敏感.分析显示P(O2)决定了薄膜中的氧空位含量和载流子浓度,从而影响了薄膜的光电特性.原子力显微镜观察表明,适量的P(O2)条件下可以获得平均粗糙度为0.3 nm、颗粒均匀、表面平整的薄膜.室温制备的IMO薄膜在可见光区域的平均透射率(含玻璃基底)高达82.1%,电阻率低至5.9×10-4 Ω·cm.