钻孔测量系统在岩土勘探中的应用(下)

通过灌浆管钻孔可以获得有助于后期隧道建设的辅助性岩土信息。以海上勘探技术为基础发展起来的陆上钻孔测量系统(instrumenteddrillingsystem)已经通过了实地岩土勘探的检验。该系统通过在设备液压回路(hydrauliccircuits)的不同位置安装一组压力传感器,检测其分辨地层的能力。从理论上讲,随着灌浆钻孔的逐层深入,本方法可以应用于几乎所有土壤类型的生成变化的定性解析(qualitativeinterpretation)。鉴于此法的取样间隔较小,约5mm,所以能够分析为传统实地勘测方法所忽略的岩土结构局部变化。本次研究分别在伦敦的坎宁顿公园(KenningtonPark)和朱比利地铁延长线(JubileeLineEx tension)两地对上述系统进行了实地检验,并在之后对从该系统得到的分析结果与获得的岩心样本进行了比对研究。我们对钻机的零部件以及钻孔方法的选择进行了研究和标准化,以便将来获得全球适用的有意义的数据。此外,通过对几组标准化和非标准化的钻孔设备和方法进行交叉相关分析,我们还量化了不一致的钻孔设备和方法对数据质量的影响程度。     

Experimental study of heat transfer in oscillating flow

This paper describes an experimental study of heat transfer in oscillating flow inside a cylindrical tube. Profiles of temperature are taken inside the wall and in the fluid from an instrumented test rig, in different conditions of oscillating flow. Profiles obtained allow the observation of the wall effect on heat transfer. A method using the inverse heat conduction principle allows the characterization of local heat transfers at the fluid-solid interface. Finally, a comparison between global and local approaches of heat transfer shows the difficulty of defining a dimensionless heat flux density to model local heat transfer in oscillating flow.     

Asymptotic performances of a constructive algorithm

We present a numerical study of a neural tree learning algorithm, the “triolearning≓ strategy. We study the behaviour of the algorithm as a function of the size of the training set. The results show that a limited number of examples can be used to estimate both the network performance and the network complexity that would result from running the algorithm on a large data set.     

The Fermi energy and the enthalpy of mixing

In this paper we describe a new function to determine the number of electrons transferred by alloying. H_F, the new function proposed, is given by the difference of the partial enthalpies of the two constituents, i.e. H_F = h(i) - h(j) - h(i)^o and is called the Fermi enthalpy. It is retrieved from data calorimetrically measured. In some way, it describes the change in the enthalpic part of the Fermi energy on alloying. This function is determined for Pd + Ga, Pd + In, Ni + Ga, Ni + In, Pt + In, Au + Al and Ag + Al. The corresponding number of electrons transferred is calculated on stoichiometric considerations.     

Stimulating Cooperation in Self-Organizing Mobile Ad Hoc Networks

In military and rescue applications of mobile ad hoc networks, all the nodes belong to the same authority; therefore, they are motivated to cooperate in order to support the basic functions of the network. In this paper, we consider the case when each node is its own authority and tries to maximize the benefits it gets from the network. More precisely, we assume that the nodes are not willing to forward packets for the benefit of other nodes. This problem may arise in civilian applications of mobile ad hoc networks. In order to stimulate the nodes for packet forwarding, we propose a simple mechanism based on a counter in each node. We study the behavior of the proposed mechanism analytically and by means of simulations, and detail the way in which it could be protected against misuse.     

Recent developments in fluorescence—based mincroscopy applied in biomedical sciences

1.IntroductionOverthelastfourdecades,fluorescencemicroscopyhasexperiencedatremendousinnovat-ingevolutionandisnowadaysawellestablishedtechniqueinmanyareasofbiomedicalre-search.Inaddition,fluorescencemicroscopicalimaginghasprovenanessentialtoolforstudy-ingbothcellstructureanddynamicprocessestakingplacewithinonecellorbetweenneigh-bouringcells.Thepresentshortreviewwillfocusonthemostrecentdevelopmentsinthisfieldofmicroscopy.2.ConventionalfluorescencemicroscopyTheterm“fluorescence”denotestheprope…     

Hardness, Toughness, and Scratchability of Germanium–Selenium Chalcogenide Glasses

Ge–Se chalcogenide glasses are characterized by relatively low hardness (0.39–2.35 GPa) and low fracture toughness (0.1–0.28 MPa·m^1/2). Actually, the hardness of chalcogen-rich glasses is low enough so that the brittleness parameter, B = H / K _c , is lower than that of silicate glasses. Whereas hardness and Young's modulus increase with increasing germanium contents, fracture toughness follows a trend similar to that of the density and exhibits a maximum for the Ge₂₀Se₈₀ composition, which corresponds to the rigidity percolation threshold. Optical microscopy and atomic force microscopy observations suggest that the indentation deformation proceeds by a localized shear deformation phenomenon. Glasses in the chalcogen-rich region behave viscoelastically at room temperature. As a consequence, an increase of the loading time results in a decrease of hardness and toughness.     

Kinetic study of the sulfurisation of cuprous halides in hydrogen sulfide. Cuprous bromide and iodide

The sulfurisation of cuprous bromides and iodides in hydrogen sulfide, at low pressure, leads to the formation of a porous chalcosine layer, as already investigated in the case of chlorides. The step which fixes the conversion rate is the diffusion of the gaseous reagents in the pores of the sulfide formed. Experimental activation energies are 15 and 34 kcal.Mole^?1 respectively, at every step of the reaction.     

Substitution du tungstene par le tantale dans les bronzes de tungstene NaxTayW1−yO3

In order to study the modification of the transport properties of Na_xWO₃ by substitution in the WO₃ sublattice, single crystals of tantalum-substituted tungsten bronzes of formula Na_xTa_yW_1?yO₃ have been grown by electrolytic reduction of fused Na₂WO₄WO₃Ta₂O₅ mixtures. The lattice constant of their cubic perovskite like structure increases with Ta content. Electric conductivity measurements on Na_xTa_yW_1?yO₃ single crystals characterize a metal-non metal transition when x-y, i.e. the number of d electrons, decreases. This transition seems to be of Anderson type.     

Effect of Ice-Induced Cross-Polarization on Digital Earth- Space Links

Among the techniques proposed to increase the capacity of the allocated frequency bands, reuse of the same channel twice with orthogonal polarizations seems to be very promising. However, imperfect isolation between the two orthogonal channels, arising, for example, from nonspherical scatterers encountered by the transmitted waves during propagation, is likely to limit the possibilities of this frequency reuse technique. While rain-induced cross-polarization is relatively well understood, the impact of cross-polarization coupling due to ice crystals on communication systems has to be thoroughly investigated. In this paper a statistical analysis of depolarization events observed at 20 GHz from the linearly polarized beacon of ATS-6 is carried out. It shows that ice depolarization events occur as frequently and are as significant as rain depolarization events, and also that ice crystals are typically canted withinpm10degof the vertical. From the results obtained, the effect of ice cross-polarization on a dual-polarized microwave link utilizingM-ary PSK transmission is investigated. These results point out the necessity of implementing cross-polarization cancellation devices.