分离岛式地铁车站交叉洞群施工的周边环境效应分析

为研究分离岛式车站交叉洞群的周边环境效应,以广州市某暗挖地铁车站为工程背景,采用数值模拟的分析方法,建立了正线隧道、联络通道和站台横通道的多洞室数值计算模型,同时考虑左右线隧道穿越不同岩性的地层,有限元模型地层为不均匀地层。通过数值模拟研究了隧道交叉洞群施工引起的地表沉降、围岩应力应变特征、支护变形受荷规律等,并将模拟结果与相应的现场监测数据对比分析。计算结果表明：中洞施工会引起围岩应力场位移场重分布,上覆围岩会向两侧滑动,造成洞间土体呈受压状态,侧洞会向两侧位移;支护结构最大应力值出现在隧道与联络通道的接口处,并且隧道支护结构应力值大小与距交叉段远近成负相关,离交叉段越远,支护应力值越小。研究成果为今后类似工程条件下城市地铁隧道施工提供参考。     

冰崩涌浪作用下的冰湖溃决过程试验研究

冰崩涌浪是导致冰湖溃决的一个主要的诱发因素之一。本文通过水槽模型试验,研究了在冰崩涌浪作用下,不同颗粒级配、坝高、下游坝坡坡度时冰碛坝的溃决过程,主要结论如下：（1）冰碛坝存在漫顶溃决、坝坡失稳、管涌破坏三种溃决模式;（2）根据冰崩涌浪的对坝体的侵蚀效应,结合溃口的纵向演化过程,将冰碛坝的溃决过程划分为涌浪侵蚀阶段（阶段Ⅰ）、库区小扰动溢流侵蚀阶段（阶段Ⅱ）;（3）涌浪过坝后的强水动力条件增加了坝体的侵蚀率,当溃口贯通后,涌浪已基本消散,溃决过程转为为正常的溢流溃决,并且涌浪向坝体提供了高频瞬时荷载,削减了坝体稳定性;（4）从动力学的角度提出了冰碛坝临界溃决条件的判定方法;（5）冰湖溃决洪峰流量与坝高和下游坝坡呈现正相关,与坝体中值粒径（D50）呈现负相关关系。     

喀斯特山地不同退化植被下烟管荚蒾氮同位素组成的季节变化

为探讨喀斯特灌木丛优势树种烟管荚蒾(Viburnum utile)叶片稳定氮同位素组成的季节变异特征及其影响因素,以喀斯特高原贵州省清镇市王家寨峰丛洼地小流域为例,选取流域内稀疏灌草丛、草灌丛、灌丛3种植被类型下的常绿树种烟管荚蒾为具体研究对象,分别在4月(生长初期)、7月(生长旺盛期)、9月(生长晚期)和12月(生长停滞期)对其叶片稳定氮同位素组成和N、P、K、Ca、Mg、Fe、Mn、Cu、Zn元素含量进行测定分析。结果表明:研究区烟管荚蒾叶片的δ~(15)N在不同群落间和不同坡位间均无显著差异(P0.05),群落间的变化趋势为灌丛稀疏灌草丛草灌丛,坡位间的变化趋势为中坡下坡上坡,变化范围为-3.28‰～-0.59‰,平均值为-2.22‰;烟管荚蒾叶片δ~(15)N值在不同群落中均表现出9月最负而12月最正的特征,变化趋势均为9月7月12月,但仅在草灌丛群落中的7月与12月间和9月与12月间有显著差异(P0.05),在其他群落中各月份间的差异均不显著(P0.05),同一生长期内不同群落间、不同坡位间的差异也不显著;研究区植被类型、坡位和季节对烟管荚蒾叶片δ~(15)N的交互影响均不显著,说明烟管荚蒾对生境恶劣的喀斯特环境具有特殊的适应能力;烟管荚蒾叶片的δ~(15)N与Fe、Mn含量密切相关,同时受N、P、K、Fe、Mn、Cu、Zn元素化学计量比的影响,说明其叶片δ~(15)N值的变化主要受自身氮生理代谢过程的控制;研究区9月温暖湿润和12月干旱寒冷的气候特征可能是导致烟管荚蒾叶片δ~(15)N在9月最负和12月最正的主要原因。     

基于ABAQUS强度折减法分析库水位下降对边坡稳定性影响

三峡水库自运行以来,库水下降成为滑坡复活的一个诱因.本文根据库区水位调度方案,利用ABAQUS软件模拟库水位在175～145m的下降过程,考虑饱和-非饱和渗流场与应力场耦合理论效应,并采用强度折减法分析库水下降对树坪滑坡稳定性的影响.分析结果表明:三峡水库以0.21m/d的速度由175m降至145m时,树坪滑坡前缘会产生一定的变形,滑坡后缘和中部,基本上未产生变形,目前树坪滑坡处于较稳定状态,但在库水反复变动及降雨作用下,可能会面临失稳的危险.其成果将为库区滑坡治理提供一定的理论依据.     

H2、O2与Pd反应的平衡压力研究

基于电子与核振动近似方法,应用密度泛函B3P86方法和相对论有效核势SDD计算,结合统计热力学方法, 研究了100K～1000K温度范围内Pd与H2、O2反应的标准生成热力学函数以及反应平衡压力与温度的关系. 结果表明：Pd与H2、O2反应是放热反应,Pd原子吸附H2的放热量大于吸附O2的放热量,温度升高不利于吸附反应进行;Pd对O2的自发吸附温度很低,室温下几乎不能进行,而对H2的自发吸附温度可高达500K以上;在100K~284.394K可自发吸附O2和H2的温度范围内,O2的反应平衡压力比H2的平衡压力高出9~18个数量级. 因此,O2作为杂质气体对目标反应Pd-H2的影响非常有限.     

嵌入式Linux在S3C2440上的移植

本文描述了将Linux移植到基于S3C2440处理器的目标板上的方法与过程。首先介绍了如何搭建嵌入式交叉编译环境,然后着重讨论了在该开发板上bootloader的设计实现以及Linux内核的移植的方法。     

漠阳江水环境质量现状分析

为保护漠阳江水环境和保护饮用水源,对漠阳江水质基本情况展开调查,摸清漠阳江及其主要支流水环境质量现状。调查发现,漠阳江源头水质较好,但随着漠阳江经阳春城区和阳江城区后,水质有所恶化。分析原因,漠阳江目前最主要的污染源为生活污水。针对该情况,本文提出了漠阳江整治的相应建议。     

Seasonal variations and environmental controls on stalagmite calcite crystal growth in Heshang Cave,central China

Stalagmite growth rates are usually considered to reflect changes in paleoclimate and paleoenvironment. However, how exactly growth rates are affected by climate and environment is still unclear. We launched a monitoring and modeling program that lasted approximately 4 years on two active drip sites in Heshang Cave, central China. We collected comprehensive quantitative data on growth rates, cave temperature, CO₂ concentration, drip rate and drip-water chemistry to better understand the relationship between stalagmite growth and cave environment. By laying out glass substrates, we successfully grew stalagmite calcite crystals with rhombic characteristics, and quantified growth rates by measuring the long and short axes of calcite crystals under a microscope. Combined with coeval environmental data, we explicitly examined the roles of cave temperature, drip rate and drip-water chemistry in controlling the micro-scale growth of stalagmite calcite. Results show that growth of stalagmite calcite crystals at two drip sites exhibited similar seasonal variations − generally faster in the summer months, at ∼3 μm d⁻¹, and slower during the late winter to early spring, at ∼1.5 μm d⁻¹. Variations in calcite growth rates were mainly determined by changes in cave temperature, with the growth rate increasing by 8.1%/°C and 6.6%/°C at the two locations. This indicates the potential use of stalagmite growth rates as a seasonal-resolution paleo-temperature proxy in some ventilated caves. On the other hand, the effect of drip rate and drip-water Ca²⁺ and SIC values on growth rates were not significant.     

PtCO分子结构与解析势能函数

用密度泛函理论的B3P86方法,对铂原子采用LANL2DZ收缩价基函数,碳原子和氧原子采用6-311G* 基组,对PtC,PtO和PtCO体系的结构进行优化,计算表明：PtC分子基态为1+态,键长为Re=0.16844nm,离解能为6.23725eV. PtO分子基态的平衡核间距为0.17486nm,其电子态为3-,离解能为3.84565eV,拟合得到Murrell-Sorbie势能函数;PtCO分子有两个线性稳定构型,其中一个构型为Pt-C≡O (C∞v),电子态为1+,平衡核间距为RPtC=0.17672nm,RCO=0.11464nm,离解能为14.46769 eV,另一个为Pt-O≡C (C∞v),电子态是1+,平衡核间距为RCO=0.11243nm,RPtO=0.21886nm,离解能为11.26729eV. 由微观过程的可逆性原理分析了分子的可能的离解极限,并用多体展式理论导出基态PtCO分子的势能函数,其等势面图准确地再现了PtCO分子的结构特征和离解能,由此讨论了Pt+CO, PtC+O, PtO+C分子反应的势能面静态特征.     

Near-field coupling and SERS effects of palladium nanoparticle dimers

The linear optical properties and the surface-enhanced Raman scattering (SERS) effect of spherical palladium nanoparticle dimers are analyzed theoretically using generalized Mie theory. The calculation results demonstrate that the near-field coupling effect greatly influences the absorption, scattering and extinction spectra of nanoparticle dimers. The surface plasmon resonance wavelength red-shifts dramatically as the separation between nanoparticles decreases. Because of the near-field coupling between nanoparticles and the size effect, the maximum SERS enhancement factor at the ‘hot spot’ between palladium nanoparticle dimers is as high as 10⁷–10⁸, while the averaged SERS enhancement factor over the entire nanoparticle surface is in the range of 10⁵–10⁶. The deviation between the position of the peak in the extinction spectrum and the wavelength for maximum surface-averaged enhancement for the Pd nanoparticle dimers indicates that localized surface plasmon resonance has different influences on the far and near fields. These theoretical results may help to reveal the relationship between the far and near fields, as well as understand the mechanism of electromagnetic enhancement in the surface-enhanced scattering of transition metals.