园林绿化工程苗木移植技术浅析

改善城市居住环境,在较短时间内改善城市景观,需要进行苗木移植.在苗木移植时不采用任何技术措施,种植后只按常规进行淋水管理,树木的成活率就很低.该文概述了苗木栽植原则,分析、归纳了园林建设过程中影响苗木移栽成活率的根系因素和环境因素,并提出了提高园林苗木栽植成活率的对策:(1)做好土壤处理、场地平整及把好苗木质量关等前期准备工作;(2)苗木适时假植;(3)定植前适当修剪与科学定植;(4)分级管养.上述移栽技术经过多年的工程实践证明,能保证树种的成活率在80%以上.     

Critical Systems Thinking on the Inefficiency in Post-Earthquake Relief: A Practice in Longmen Shan Fault Area

The Longmen Shan Fault area is one of the most active seismic zones in the world, has a relatively dense population and a low economic development level. Therefore, the provision of effective post-earthquake relief is very important for saving lives and restricting financial losses. However, providing urgent relief is a complex problem that requires efficient coordination between the organizations, and departments involved, and the specific environments, for the supply of urgent materials, energy and information. In practice, although there are sufficient relief supplies, because of the lack of systemic thinking, relief activities are often chaotic leading to inefficiencies and even increases in the damage and loss of life. In this study, a critical systems thinking approach is used to reflect on the system contexts, boundaries, structures and functions of the emergency relief systems. Using systems modeling we constructed simulations for different relief plans and their consequences, and a work shop of metasynthetic engineering was constructed to integrate the different views, knowledge and contexts. At the practical stage, after the model’s validity was verified from the 2008 Wenchuan earthquake data, based on the 2013 Lushan earthquake simulation results, some recommendations are made to improve future post-disaster relief operations. Finally, the significance of critical systems thinking is demonstrated to ensure effective and efficient of post-earthquake relief. Some limitations and future research also have been presented in conclusion.     

从王昌龄边塞诗看其对边塞战争的态度

王昌龄是唐代著名的边塞诗人,他对当时边塞战争的认识经历了一个不断深化的过程,从他的边塞诗中,我们可以清楚地看到其对当时边塞战争的态度。青年时代漫游边关,慷慨激昂,热情讴歌、积极支持保卫边关的战争;深入了解边塞和戍边士卒的现实情况后,他开始厌倦没完没了的开边战争;随着人生阅历的增加,他对边塞战争给人民带来的苦难有了更深的认识,到晚年他更是明确反对穷兵黩武的开边、扩边战争。     

周期性微结构的纳秒激光四光束干涉烧蚀研究

多光束干涉是一种快速制备大面积周期性微纳结构的简易方法.本文基于四光束干涉烧蚀技术,利用纳秒激光在硫化锌衬底上无掩模烧蚀制备大面积的结构阵列;并详细研究了结构形貌随曝光时间的演化规律;利用四光束干涉理论,重点研究了四光束干涉时角度误差引起的相移对于结构类型的影响;结合我们近几年的研究工作,讨论多光束干涉烧蚀面临的挑战及展望.     

Joint analysis of recurrent event data with a dependent terminal event

Recurrent event data frequently occur in many longitudinal studies, and the observation on recurrent events could be stopped by a terminal event such as death. This paper considers joint modeling and analysis of recurrent event and terminal event data through a common subject-specific frailty, in which the proportional intensity model is used for modeling the recurrent event process and the additive hazards model is used for modeling the terminal event time. Estimating equation approaches are developed for parameter estimation and asymptotic properties of the resulting estimators are established. In addition, some procedures are presented for model checking. The finite sample behavior of the proposed estimators is evaluated through simulation studies, and an application to a heart failure study is provided.     

对数线性模型的选择方法及其应用

为构造最佳对数线性模型,通过λ系数构造λ相关系数矩阵,将其作为对数线性模型中交互项选择的方法,并用于分析肺癌治疗数据。结果表明,选出的交互项可以构造最佳的模型对数据进行准确的分析,因此在应用对数线性模型分析前,先用相关系数矩阵进行探索性研究分析是很有必要的。     

Synthesis,characterization, and theoretical study of N,S-codoped nano-TiO<Subscript>2</Subscript> with photocatalytic activities

Nitrogen and sulfur doped titanium dioxide photocatalysts were prepared by the sol-gel method. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-visible diffuse reflectance spectra (DRS). Photocatalytic activities of the samples were investigated on the degradation of methyl orange (MO). The effect of the dopants on the electronic structure of TiO₂ was studied by the first-principles calculations based on the density functional theory (DFT). The orbital hybridization resulted in energy gap narrowing and electronic delocalization in the crystal of doped TiO₂. Mobile electrons of varied energetic states could offer enhanced electron transfer, together with optical absorption improvement. The results show that the doping elements of N and S play a cooperative role in the modification of electronic structure, which enhances the photocatalytic performance. The experimentally observed absorption edges of N-doped TiO₂, S-doped TiO₂, and N, S-codoped TiO₂ are 420, 413, and 429 nm, respectively, which can be explained by the theoretical calculation results.     

基于动力拟序涡模型的水波三维大涡模拟

利用大涡模拟理论数值模拟了规则波和不规则波的传播过程,采用动力拟序涡黏性亚格子应力模型进行波高及速度场的模拟.计算结果表明,模型对水波的波高及由波产生的流体速度分布模拟结果与解析值符合良好,且精度较高.对比分析了人工海绵层及Sommerfeld辐射型耦合边界条件与仅采用Sommerfeld辐射型边界条件对水波数值模拟精度的影响.结果表明动力拟序涡粘性模型可以准确地模拟水波传播特性.     

铁路货运网格数据平台关键技术研究

设计并实现了一个高扩展性、高可用性的数据网格系统RFGrid来处理海量的铁路货运数据.RFGrid提出一个虚拟化数据模型,集成全国各个铁路局所有的数据,提供全局统一的数据视图,支持灵活高效的构件化业务开发模式.RFGrid采用分布处理的模式,将任务分解到各个路局并行执行,所有处理细节对用户透明,降低了分布式数据处理的复杂性,提高了资源利用率.最后,利用真实的货运生产应用作为负载进行性能分析,结果显示RFGrid能显著提升货运数据处理的性能,提高了货运分析的效率,对提高运输组织水平有重要意义.     

Etching mechanism of barium strontium titanate （BST） thin films in CHF_3/Ar plasma

Reactive ion etching was used to etch barium strontium titanate thin films in a CHF3/Ar plasma.BST surfaces before and after etching were analyzed by X-ray photoelectron spectroscopy to investigate the reaction ion etching mechanism,and chemical reactions had occurred between the F plasma and the Ba,Sr and Ti metal species.Fluorides of these metals were formed and remained on the surface during the etching process.Ti was almost completely removed because the TiF4 by-product is volatile.Minor quantities of Ti?F could still be detected by narrow scan X-ray photoelectron spectra,and Ti?F was thought to be present in the form of a metal-oxy-fluoride.These species were investigated from O1s spectra,and a fluoride-rich surface was formed during etching.BaF2 and SrF2 residues were difficult to remove because of their high boiling point.The etching rate was limited to 12.86 nm/min.C?F polymers were not found on the surface,indicating that the removal of BaF2 and SrF2 was important for further etching.A 1-min Ar/15 plasma physical sputtering was carried out for every 4 min of surface etching,which effectively removed remaining surface residue.Sequential chemical reaction and sputtered etching is an effective etching method for barium strontium titanate films.