随机振动的描述及其试验与仿真

阐述了随机振动的描述方法,随机振动试验条件和相关参数的计算等。并结合实例,介绍了随机振动有限元仿真的流程及其工程意义,以便在深入了解随机振动原理的基础上,指导随机振动试验和有限元仿真的开展。     

Dynamic response and effect of apertures on explosion parameters of flameproof apparatus

Explosion parameters for closed flameproof apparatus are changed when apertures like gap (e.g. push button) and porous structures (breathing element) are introduced on the cover or wall of the flameproof enclosures. Similarly, an interconnecting tube between two enclosures, results in significant change in explosion parameters. It is observed that the maximum explosion pressure, maximum rate of pressure rise and severity index are higher for enclosures with apertures on cover or body than that of enclosures without apertures. In case of two interconnected identical enclosures, the explosion parameters are increased in the secondary enclosure and higher than that of primary enclosure and also of isolated enclosure.     

贵阳市秋、冬季PM_(2.5)中碳组分污染特征及来源分析

为研究贵阳市大气细粒子PM2.5中有机碳(OC)和元素碳(EC)的污染特征,于2013年10月14日至2013年12月25日,采集2个监测点位秋季和冬季的PM2.5样品,检测分析PM2.5中有机碳(OC)、元素碳(EC)的质量浓度。结果表明,秋季PM2.5中OC的平均浓度为14.9μg/m3,EC的平均浓度为2.31μg/m3;冬季PM2.5中OC的平均浓度为26.2μg/m3,EC的平均浓度为7.53μg/m3,呈冬季高、秋季低的季节变化特征。秋、冬季PM2.5中OC/EC的值均大于2,表明存在二次有机碳(SOC)的贡献;秋季SOC的值为6.89μg/m3,冬季SOC的值为8.29μg/m3。通过计算PM2.5中8个碳组分丰度,初步判断PM2.5中秋季碳的主要来源是汽车尾气、道路扬尘和生物质燃烧,冬季碳的主要来源是汽车尾气、燃煤尘和道路扬尘。     

Assessment of potential soybean cadmium excluder cultivars at different concentrations of Cd in soils

The selection of cadmium-excluding cultivars has been used to minimize the transfer of cadmium into the human food chain. In this experiment, five Chinese soybean plants were grown in three soils with different concentrations of Cd (0.15, 0.75 and 1.12 mg/kg). Variations in uptake, enrichment, and translocation of Cd among these soybean cultivars were studied. The results indicated that the concentration of Cd in seeds that grew at 1.12 mg/kg Cd in soils exceeded the permitted maximum levels in soybeans. Therefore, our results indicated that even some soybean cultivars grown on soils with permitted levels of Cd might accumulate higher concentrations of Cd in seeds that are hazardous to human health. The seeds of these five cultivars were further assessed for interactions between Cd and other mineral nutrient elements such as Ca, Cu, Fe, Mg, Mn and Zn. High Cd concentration in soil was found to inhibit the uptake of Mn. Furthermore, Fe and Zn accumulations were found to be enhanced in the seeds of all of the five soybean cultivars in response to high Cd concentration. Cultivar Tiefeng 31 was found to fit the criteria for a Cd-excluding cultivar under different concentrations of Cd in soils.     

昆山市大气 PM 2．5中无机元素污染特征研究

应用SEM－EDS结合XRF法测定了2013年8月－2014年5月昆山市7个不同地区大气PM2．5中无机元素的污染水平。研究发现,昆山地区一共可检出40种无机元素,其中主要的22种元素浓度范围在3.02～1113 ng／m3之间,合计为3784 ng／m3;PM2．5中无机元素季节变化明显,呈现春秋季高,夏冬季低的变化特点。无机元素的空间变化不大。通过富集因子的研究,Sc、Ni、Cu、Zn、As、Br、Cd、Pb、Se、Ag、Sn、Sb和Tl等13种元素EF＞10,富集程度非常高,说明人类活动对这些元素的贡献较大。     

Numerical and experimental investigations on laser melting of stainless steel 316L metal powders

This paper presents numerical and experimental investigations on laser melting of SS grade 316L powder on top of AISI 316L substrate using a pulsed Nd:YAG laser. The objectives of the present study are to understand the effect of process parameters such as laser power, scanning speed and beam size on geometry characteristics of the melt zone and ball formation. We formulated a moving heat source problem and obtained transient temperature solutions using commercial finite element solver. The geometry characteristics of the melt zone are evaluated from the temperature solutions and compared with experimental results. The effect of laser parameters on the geometry, morphology and homogeneity of single track realization was methodically analyzed by utilizing characterization tools such as laser particle size analyzer, macro and microscopic inspection, Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The results presented in this paper are beneficial to realize homogenous layer formation in additive manufacturing processes involving powder melting by laser beam.     

北京市密云水库上游金矿区土壤稀土元素的地球化学特征

采集了密云水库上游金矿区的34个土壤表层样品,用电感耦合等离子体质谱法(ICP-MS)测定了土壤稀土元素含量,研究了土壤不同粒级中稀土元素的分布特征,并对土壤稀土元素含量分布的影响因素、累积效应、配分模式及分馏特征进行了分析和探讨。结果表明:金矿区土壤稀土元素总量∑REE略高于中国大陆土壤∑REE背景值。随着颗粒粒径的减少,稀土元素及总有机碳(TOC)含量均逐渐增加。相关性分析表明,各稀土元素均表现出相似的相关性,与全量元素Li、V、Co、Ga、Rb、Cs呈正相关,与Cu、Cd、Pb及pH呈负相关,与TOC呈显著正相关;土壤pH、有机质和矿物质成分与稀土元素含量分布密切相关。累积因子(AF)分析表明,稀土元素在粘粒级(0~2μm)、粉砂粒级(2~50μm)中表现出显著的累积效应,这是由于微细颗粒比表面积较大,次生矿物及有机质含量较高。经球粒陨石标准化后,各粒级稀土元素总体配分曲线相近,均表现为Ce无异常,Eu明显亏损,50μm的粗粒级Eu亏损较细粒级更为严重。土壤轻重稀土分馏程度关系为:砂粒级(50~350μm)粉砂粒级(2~50μm)粘粒级(0~2μm)。该研究结论将为选取稀土元素作为示踪剂提供科学依据,并为不同粒级中稀土元素的进一步研究提供一定的参考价值。     

An investigation of cellular distribution of manganese in hyperaccumlator plant Phytolacca acinosa Roxb. using SRXRF analysis

Phytolacca acinosa Roxb. （P acinosa） is a recently discovered manganese hyperaccumulator plant from southern China. It is a good candidate for phytoremediation of manganese（Mn） polluted soil for its high biomass and fast growth. Knowledge of the tissue localization and identification of heavy metals can provide essential information on metal toxicity and bioaccumulation mechanisms. Synchrotron radiation X-ray fluorescence spectroscopy （SRXRF） microprobe was used in this study to investigate the cellular distributions of Mn and other elements in root, stem, leaf, petiole and midrib of P. acinosa. The highest Mn content was found in the vascular tissues of root, stem, petiole and midrib. Cortex in root played a key role in Mn absorption and Mn was limited in the vascular bundle during the process of transportation in stem. Moreover, Mn content in leaf epidermis was higher than that in mesophyll, which suggested that the sequestration of Mn in leaf epidermis might be one of the detoxification mechanisms of P. acinosa. The significance of other elemental （such as P, S, K, Ca, Fe, Zn and Cu） distribution patterns and the correlation with Mn were also discussed.     

钢筋混凝土梁在火侵袭下的反应分析

结构物在大火侵袭下，结构内部温度和结构挠度、内力将随时间发生不断变化，这种变化极为复杂。本文在试验研究的基础上，采用非线性有限元法，着重研究钢筋混凝土梁在火侵袭作用下其温度和挠度的反应，提出了一种理论分析方法，编制了计算机程序，对钢筋混凝土梁的温度、挠度和内力的反应进行了计算，并得到试验结果的验证。     

贵州南部河谷热带性植物资源及开发利用

贵州南部河谷热带性植物共计464种、2变种。主要构成3种植被类型:大型羽状复叶林、稀树草坡灌丛与肉质多刺灌丛。可分为11类经济用途:药用(139种)、纤维(38种)、野果(21种)、观赏(21种)、鞣料(18种)、饲料(13种)、油脂(13种)、淀粉(12种)、紫胶虫寄主(11种)、芳香(6种)、染料(5种)。资源流失与环境变化,使现存资源的保护与深层次利用成为当前的主要问题。