交叉隧道在不同夹层土体厚度下的地震响应分析

基于FLAC3D软件,采用数值模拟的方法,对在不同夹层土体厚度及不同峰值加速度情况下,交叉隧道的地震动力响应进行研究,得出了交叉隧道结构的地震动力响应规律。结果表明:上层隧道的相对水平位移差明显大于下层隧道的相对水平位移差。上层隧道地震应力反应大于下层隧道的地震应力反应。随着夹层土体厚度的增大,衬砌结构的加速度、位移和应力略有变化但总体变化不大,并得出0.5 D～2 D(D为隧道外径)的厚度为较理想的夹层土体厚度,此时加速度、位移和应力总体较其它偏于安全。此结论为穿越既有隧道的交叉隧道工程选线和穿越深度提供重要的理论参考依据。     

Endosulfan acute toxicity and histomorphological alterations in Jenynsia multidentata (Anablepidae,Cyprinodontiformes)

Toxicity tests using adult specimens of Jenynsia multidentata were carried out during 96 hours in order to determine the lethal concentration (LC50) of endosulfan. Histological alterations were determined in gills and liver. Gill damage was quantified as secondary lamellae thickness. The 96 hr LC50 values were significantly different between males (0.719 μ g.L^{? 1}) and females (1.317 μg.L^{? 1}). The sex difference was attributed to the dimorphism in the lipid content in females (2.16%) and males (1.79%). Histological alterations in gills included hypertrophy and lifting of the epithelium of the secondary lamellae and aneurisms. These alterations caused a significant increase of the secondary lamellae thickness in treatment versus control fish. Finally, reversible histological alterations (such as hydropic degeneration and dilation of sinusoids) were observed in the liver of exposed fish as well as an irreversible change such as necrosis at the highest concentrations.     

Bottomfast Ice Mapping and the Measurement of Ice Thickness on Tundra Lakes Using C‐Band Synthetic Aperture Radar Remote Sensing1

Abstract: Industrial activity in Canada’s north is increasing, placing demands on the use of water from lakes to build ice roads. Winter water withdrawal from these lakes has the potential to impact overwintering fish. Removal of water from small lakes can decrease oxygen and habitat available to fish. To address this issue, a protocol has been developed by the Department of Fisheries and Oceans outlining water withdrawal thresholds. Bathymetric surveys are the traditional method to determine lake depth, but are costly given the remoteness of northern lakes. This paper investigates the use of satellite C‐band synthetic aperture radar (SAR) remote sensing technology as a potential alternative or complement to traditional survey methods. Previous research has shown that a SAR can detect the transition from grounded to floating ice on lakes, or if a lake is completely frozen. Grounded ice has a dark signature while floating ice appears very bright in contrast. Similar results were observed for the datasets acquired in the study area. This suggests that lakes that freeze completely to the bottom can be identified using SAR. Such water bodies would not be viable fish overwintering habitat and can therefore be used as water sources without thresholds necessary. However, attempts to accurately calculate the depth of the ice at the grounded‐floating ice boundary using bathymetric profiles acquired in the summer and lake ice thickness measurements from a reference lake near Inuvik proved to be unreliable.     

Ultrasonographic scanning of placental thickness and the prenatal diagnosis of homozygous alpha-thalassaemia 1 in the second trimester

In order to evaluate the association between placental thickness (PT) and fetal homozygous alpha-thalassaemia 1 before the appearance of classic ultrasound findings of haemoglobin (Hb) Bart's hydrops fetalis, a total of 473 pregnancies were collected. The control group included 422 normal pregnancies with a gestational age from 14 to 23 weeks and the study group included 51 affected fetuses in the same gestational period. Fetal biparietal diameter (BPD) and PT were measured by high-resolution ultrasound. PT was evaluated against BPD. In the control group, the PT generally increased in parallel with the advancement of gestational age. All PT measurements in the study group were above the mean PT of their respective gestational week in the control group. Forty-six (90 per cent) of the pregnancies in the study group had PT larger than the mean plus two standard deviations of the control group. This study suggests that ultrasound measurement of PT may be a useful aid in the prenatal diagnosis of Hb Bart's hydrops fetalis before its classic findings become apparent in the late second trimester or third trimester.     

Minimum propagation diameter and thickness of high explosives

The critical diameter and critical thickness of two heterogeneous explosives were measured experimentally. By comparing these experimentally determined values of critical diameter and critical thickness, the role of front curvature in the failure of the detonation can be investigated. Current theories of detonation based on front curvature would predict the critical diameter should be twice the critical thickness. Experimentally, the expected two-to-one ratio was only validated for the case of a heterogeneous explosive with very fine scale heterogeneities. The ratios of critical diameter to critical thickness (for the two selected explosives) are also compared to previously measured values for homogeneous (liquid) explosives in order to contrast the dominant failure mechanism in these different explosives.     

ICAROS: An Integrated Computational Environment for the Assimilation of Environmental Data and Models for Urban and Regional Air Quality

Integrated environmental management in urban areas is nowadaysconsidered a sine qua non objective of Community and nationalenvironmental and development policies. A large amount ofscientific information on the state of the environment is nowavailable from a large pool of data sources. This work presentsan innovative method for integration of these data sources andeffective coupling of environmental information with appropriatemodels and decision-support tools. State-of-the-art Earthobservation techniques, ground-based air quality measurements,atmospheric transport and chemical modelling, and multi-criteriadecision-aid systems are used in an integrated information fusionenvironment in support of environmental and health impactassessment and decision-making at the urban and regional scales. Results of the pilot application of the method in the area ofLombardy in Northern Italy demonstrate the validity andusefulness of this novel approach.     

The Assessment of Atmospheric Pollution using Satellite Remote Sensing Technology in Large Cities in the Vicinity of Airports

This paper investigates the potential of usingsatellite remotely sensed imagery for assessing atmosphericpollution. A novel approach, which comprised radiativetransfer calculations and pseudo-invariant targets fordetermining aerosol optical thickness has been developed.The key parameter for assessing atmospheric pollution inphotochemical air pollution studies is the aerosol opticalthickness. The need for identifying suitable pseudo-invariantobjects in satellite images of urban areas is of great interest for increasing the potential of earthobservation for monitoring air pollution in such areas. Theidentification of large water bodies and concrete apronsthat can serve as suitable dark and bright targetsrespectively in different geographical areas wasdemonstrated in this study. This study added evidence onthe correlation found between the visibility valuesmeasured at Heathrow Airport area during satellite overpassand aerosol optical thickness derived from Landsat-5 TMband 1 images.     

三级以上海况海面油膜厚度测定装置的研制

本文描述了３级以上海况（３￣５级）海面油膜厚度测定的非光学装置，该装置由敝开一封闭式油膜采样器和降集增厚器组成。为适应恶劣海况情况下采集油膜，保证数据的可靠性，该装置增加了防止油膜外溢的机构及原始平行样采样管，海上现场试验分别以零号轻柴油、海军燃料油、混合油为对象，测定厚度为１００￣１０００μｍ的油膜。并对多次采样的测定值进行了数理统计。该装置现场测定的相对误差≤±２４．５％。     

聚丙烯酰胺(PAM)在水厂排泥水处理中的应用研究

介绍了水厂排泥水处理浓缩污泥投加ＰＡＭ的重要性、ＰＡＭ絮凝机理，实验室ＰＡＭ筛选及ＰＡＭ在水厂排泥水处理中应用效果。