关于使用 Pro/Engineer wildfire软件设计三维机械零件的几点技巧在教学中的探讨

本文对使用Pro/Engineer Wildfire 软件设计三维机械零件在教学中遇到的若干问题作了深入细致的分析,并提出了相应的解决技巧.     

气吸振动式排种器种盘内种群运动的离散元分

根据离散元法的基本思想,采用线性弹簧-阻尼-滑动接触力学模型,编写Matlab模拟程序,分析了气吸振动式精密排种器振动种盘内种群的三维运动规律.为了描述籽粒离散分布程度,给出了体积膨胀系数的计算公式.结果表明,种盘作小幅高频振动,种群可以产生向上抛掷运动而有效分离;膨胀系数随着振动强度的增加而增大,随种层厚度的增加而减小.分析了摩擦因数和碰撞恢复系数对不同层厚种子膨胀系数的影响.在初始层厚参数hs≈3.8、振动强度kv=5.65时,种子具有理想的运动状态,通过性能试验得到排种器的吸种率达98%.     

Numerical Analysis on Stability of Rock in Sijiaotian Tunnel

The Sijiaotian Tunnel in Yunnan Dabao Highway lies in the narrow defile landscape,and the engineering geology condition is complex,with plenty of cienega.According to the actual situation of the Sijiaotian Tunnel Project in Yunnan Dabao Highway,the stability of the surrounding rock mass is studied by using a 3-D non-linear FEM.The Drucker-Prager criterion is chosen as the failure criterion of the rock.The relatively dangerous zone and the monitoring points in the tunnel are determined.The numerical results show that the Sijiaotian Tunnel is relatively stable.The conclusion has some significance for guiding the construction of similar projects.     

Sodium bicarbonate reduces postharvest decay development on melons

Sodium bicarbonate (SBC) inhibited in vitro mycelial growth of A. alternata, Fusarium spp. and R. stolonifer. SBC action was fungistatic rather than fungicidal. Coating commercially harvested ‘Galia’ and ‘Ein-Dor’ melons with wax containing 2% SBC reduced decay incidence after storage and shelf life simulation by four to seven-fold, to a commercially acceptable level of 6–7%, compared to untreated or waxed-treated controls. This treatment also maintained the fresh and blemish-free appearance of the fruit at harvest. Higher concentrations of SBC (3%) were phytotoxic and significantly reduced general fruit appearance. A trial shipment by sea transport to Europe demonstrated that 2% SBC incorporated into a wax coating maintained the marketability of ‘Galia’ melon fruits compared to that of untreated fruit. SBC can be an alternative biocide to the fungicide imazalil, thus eliminating unwanted residues on melon fruits.     

基于三维激光扫描成像系统的树木干曲线的分形特征

树木干曲线具有分形的结构,文章应用分形方法对甘肃小陇山地区86棵不同树种的单木以及解析木干曲线进行研究,通过计算得到干曲线的分形维数介于2-3之间,研究结果表明同一树种树木干曲线的生长趋势是一致的。经过对单木干曲线和标准解析木干曲线分形维数的测定以及比较分析,可以发现同一树种不同径阶的树木干曲线具有统计意义上的自仿射分形特征,表明分形方法在对树木及其组成部分的形态上的描述作用极大。文章针对立木的测量,采用三维激光扫描成像系统,不仅获得了丰富的测树因子信息,更以此为基础对森林计测学研究进行了扩展,是一项非常有意义的工作。     

Arylsulfatase activity in soil and soil extracts using natural and artificial substrates

The arylsulfatase activity of soil and humic arylsulfatase complexes extracted from soil were measured using the substrates p-nitrophenyl sulfate and low molecular weight (500–10000) soil ester sulfate compounds. Soil samples from the Aphorizon of a Podzol from S-amended wheat plots and a Regosol from dykeland hayfield plots were investigated. Soil arylsulfatase activity (assayed with p-nitrophenyl sulfate) in the fall was significantly higher than spring samples; however, no seasonal differences were observed when humic-arylsulfatase complexes were assayed with p-nitrophenyl sulfate. The discrepancy between arylsulfatase activity in soil and soil extracts was probably due to inhibitors which were found in soil materials. These results appear to support the theory that abiotic arylsulfatase is a relatively stable and persistent component of soil. There was a marked difference in the response by humic-arylsulfatase complexes to the artificial substrate p-nitrophenyl sulfate and natural low molecular weight soil substrates. Humic-arylsulfatase complexes hydrolysed 35–80% of added low molecular weight substrates depending on the treatment. The molecular size, concentration, and chemical composition of the low molecular weight ester sulfate compounds affected hydrolysis of the low molecular weight substrates. The response by humic-arylsulfatase complexes to the chromogenic ester sulfate, p-nitrophenyl sulfate did not reflect the ability of these complexes to hydrolyse natural soil substrates. In an experiments we examined arylsulfatase activity and soil S status in relation to the total S in plant tissue and grain from wheat plants grown in the Podzol. Tissue S was more strongly associated with soil S than the wheat grain. Hydriodic acid-S, Ca(H₂PO₄)₂-extractable sulfate, and hydrolysable ester sulfates in the high molecular weight (>10000) and low molecular weight (500–10000) fractions of soil organic matter extracts were strongly positively correlated with tissue S. Arylsulfatase activity in soil and humic-arylsulfatase extracts assayed with p-nitrophenyl sulfate were also strongly correlated with tissue S, while humic-arylsulfatase activity assayed with the low molecular weight substrate was negatively correlated with tissue S.     

Microbial mineralization of atrazine and 2,4-dichlorophenoxyacetic acid in riparian pasture and forest soils

Microbial biomass and mineralization of atrazine [2-chloro-4(ethylamino)-6(isopropylamino)s-triazine] and 2,4-D (2,4-dichlorphenoxyacetic acid) were examined in the top 10 cm of riparian pasture soils and in the litter layer and top 10 cm of mineral soils of riparian forest ecosystems. The riparian forest litter had higher levels of active and total fungal biomass than forest or pasture mineral soils in winter, spring, and fall. Active bacterial biomass was higher in forest litter than in forest and pasture mineral soils in spring and autumn, and higher in forest mineral soils than in pasture soils in summer. Total bacterial biomass was higher in forest mineral soils than in pasture soils during all seasons. In spring, it was also higher in forest litter than in pasture soils. Atrazie and 2,4-D mineralization in pasture soils was exceeded by that in forest litter in spring and autumn and by that in forest mineral soils in summer and autumn. There was no correlation between either active or total fungal and bacterial biomass with pesticide degradation.     

运用多隔层根箱研究玉米幼苗根际微域中芘的降解

采用多隔层根箱,通过尼龙撩网插片的控制,实现根室土(S0)、离根室0～2mm(S1)、2～4mm(S2)、4～6mm(S3)及6mm(S4)各室层土壤的分离采集,分析离根系表面不同距离土壤芘的根际降解,并借助脂肪酸甲酯(fattyacidmethylester,FAME)分析土壤微生物群落结构的空间响应机制。结果表明:种植玉米处理的各室层内土壤可提取态芘含量存在显著的不同,其大小顺序为S4S3S0S2S1;各室层微生物群落结构存在显著的变化,其中微生物生物量和丛枝菌根真菌特征脂肪酸含量表现出与土壤可提取态芘含量变化相反的变化趋势。未种植玉米处理的各室层土壤可提取态芘含量和微生物群落结构没有差异。土壤可提取态芘含量与微生物生物量和丛枝菌根真菌的特征脂肪酸呈显著负相关(p0.01)。     

傅立叶变换近红外光谱法检测白酒总酸和总酯

该文研究白酒总酸和总酯的快速检测技术，通过解析不同白酒样品的近红外光谱图，对光谱数据进行不同的处理，结果表明：用一阶导数预处理光谱，谱区选择6102～5446 cm^-1，利用人工神经网络与傅立叶变换近红外光谱相结合,采用内部交叉验证法建立模型，效果较好。其中，总酸模型的决定系数为96.73%，内部交叉验证均方根差为0.048 g/L；总酯模型的决定系数为99.58%，内部交叉验证均方根差为0.085 g/L；进一步对总酸和总酯的模型进行验证和评价，结果表明总酸模型验证集的相关系数为99.2%,预测标准偏差为0.074 g/L；总酯模型验证集的相关为99.7%,预测标准偏差为0.134 g/L，表明建立的模型可靠，预测效果好,能满足白酒生产中总酸和总酯的快速检测要求。     

Terrestrial Ecotoxicity of Eight Chemicals in a Systematic Approach (7 pp)

Background and Objective   Terrestrial ecotoxicity data are required for many research purposes. The data are derived either from the literature or elaborated by own investigations. As the terrestrial toxicity tests are usually time-consuming and labour intensive, the experiments are performed with a limited number of test organisms and soils. In the context of a project sponsored by CEFIC-LRI (European Chemical Industry Council – Long-Range Research Initiative), EC50-values were systematically elaborated for eight chemicals with a wide range of logKow-values (CdCl2, Trinitrotoluene, 3,4-dichloroaniline, 2,4-dichlorophenol, Tributyltinchloride, Pentachlorophenol, Benzo(a)pyrene, p,p-dichloro-2,2-diphenyl-1,1,1-trichloroethane). The substances were selected covering a broad range of physico-chemical and ecotoxicological properties. As toxicity endpoints, microbial activities, plant germination and growth as well as reproduction of earthworms and collembola were determined. As such systematic investigations are rarely performed and for some substances no data existed, the data pool is made available to the scientific community.Methods   All toxicity tests were conducted on three different soil types (sandy soil, silty soil, loamy soil), according to ISO and OECD guidelines Results, Discussion, Conclusion and Outlook   The different toxicities of the chemicals, the influence of soil properties on bioavailability as well as different sensitivities of test organisms and test parameters are reflected by the EC50-values. The results showed that the EC50-values calculated on the basis of nominal concentrations can significantly vary from EC50-values derived from analytical concentrations for some substances. To avoid false conclusions, this has to be considered especially when concentrations determined in the field are compared with toxicity data obtained from the literature or calculated on the basis of nominal concentrations. Moreover, the results indicate that terrestrial ecotoxicological tests should be accompanied by chemical analyses, to be sure to derive sound EC50-values. As the tests were performed according to international guidelines, the comprehensive data pool relevant for the terrestrial ecotoxicity of eight chemicals is considered to be of great value for further research and discussions dealing with the habitat function of soils.