STRENGTH CRITERION FOR PLAIN CONCRETE UNDER MULTIAXIAL STRESS BASED ON DAMAGE POISSON''S RATIO

A new unified strength criterion in the principal stress space has been proposed for use with normal strength concrete (NC) and high strength concrete (HSC) in compressioncompression-tension, compression-tension-tension, triaxial tension, and biaxial stress states. The study covers concrete with strengths ranging from 20 to 130 Mpa. The conception of damage Poisson's ratio is defined and the expression for damage Poisson's ratio is determined basically.The failure mechanism of concrete is illustrated, which points out that damage Poisson's ratio is the key to determining the failure of concrete. Furthermore, for the concrete under biaxial stress conditions, the unified strength criterion is simplified and a simplified strength criterion in the form of curves is also proposed. The strength criterion is physically meaningful and easy to calculate, which can be applied to analytic solution and numerical solution of concrete structures.     

OPTIONS FOR THE REGULATION OF MEDITERRANEAN DEMERSAL FISHERIES

Research and management actions are reviewed with respect to demersal fisheries of the Mediterranean since the Second World War, as reflected in the activities of the General Fisheries Council for the Mediterranean, (GFCM). The scientific background to the priority concern expressed for minimum size limits in the 1960's and 1970's is discussed, and in particular, the mesh selectivity experiments that formed the basis for yield per recruit calculations, with respect to the trawl fishery. More recent considerations, changing our perception of the appropriateness of size at first capture of demersal fish as a management tool in trawl fisheries, are reviewed. It is concluded that for multispecies fisheries where the first priority for fishing effort control is not respected, size limits based on size at maturity, rather than yield per recruit criteria, are more feasible, but that changes in mesh size need to take into account subsequent changes in equity between inshore and offshore fleets, and changes in species composition and areas of distribution during the life history. They also need to consider the high landed value of small fish in many Mediterranean fisheries. Alternative, or supplementary, measures to mesh size regulation that affect capture of small fish are also reviewed, including seasonal closures, closed areas, bans on trawling inshore, and regulations on minimum size at sale. A range of problems to be considered prior to deciding on an increase in mesh size are reviewed, including changes in total effort exerted, changes in increases in fishing power (and especially the impacts on the spawning stock), changes in discard rate, “meshing” of small fish, and indirect mortality during fishing. A strategy for introducing new mesh sizes is suggested, with emphasis, where possible, on the experimental approach, and on supplementary measures to control fishing effort. The paper concludes by considering an alternative paradigm to minimum size regulation for demersal fisheries management; namely, the exploitation of juvenile fish, with provision for escapement of a small proportion of large, mature fish offshore, for which exploitation rate declines and remains low. It is suggested that this strategy may be, de facto, the one prevailing in the small mesh size inshore trawl fishery prior to development of offshore fisheries. The implications of this possibility have to be considered seriously if high effort levels are to be maintained while effective size limits are raised.     

数理统计方法研究大气污染与癌病的关系

用数理统计方法以某市近 6年期间发现的 2 2 90个肿瘤病例为依据 ,定量地解决了 SO2 、香烟销售量、COD、T· S· P对肺癌等 7种癌病的影响大小 ,从而解决了不同污染区 ,不同癌病有目标地重点解决大气污染治理投资问题     

Concentration self-quenching in solid solutions of complex organic molecules under intense excitation

A theoretical study was carried out to investigate concentration self-quenching which is nonlinear in intensity in a molecular system caused by nonradiative electronic excitation energy transfer to relatively long-lived acceptors that are formed in a solution and whose function is performed by molecules that have acquired the triplet state. It is shown that at ratios of constants of radiative and nonradiative transitions typical of complex molecules at concentrations of ∼10⁻³–10⁻² mole/liter substantial (2- to 10-fold) fluorescence takes place at intensities of excitation of ∼10⁴–10³ of the intensity of saturation for a singlet subsystem. Polarization characteristics of the system are analyzed. Belarusian State University, 4, F. Skorina Ave., 220050, Minsk, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 729–733, November–December, 1997.     

Spectral-Luminescent Properties of Cationic Indotricarbocyanine Dyes in Cancerous Cells and Solutions

The spectral-luminescent properties of symmetrical indotricarbocyanine dyes with the same cation and different anions (Br^–, BF₄ ^–) in cancerous HeLa cells, an isotonic solution of NaCl, and organic solvents have been investigated. It is shown that when these dyes are present in cells in nontoxic concentrations, they are in a monomeric state, they are localized in the region with a low dielectric permeability, bonded to biological macromolecules, and do not make contact with an aqueous medium. It has been established for the first time that the molecules of the polymeric dyes are present in cells predominantly in the form of contact ion pairs, and in a dye with the Br^– anion the presence of free cations or solvately separated ionic pairs is revealed. It is shown that the shift of the ion equilibrium toward contact ion pairs for the dyes in the cells (as compared to the low-polarity organic solvents) can be due to the fairly high concentration of salts in the biosystem.     

Quantum Electroluminescence Yield of EuGa2S4 Single Crystals

The quantum yield of the electroluminescence of EuGa₂S₄:Nd single crystals for the dependence of the mean free path of the electron on its kinetic energy and the kinetic energy square are calculated, as well as the impact excitation cross section of Nd³⁺ in the single crystals indicated. The mechanism of electron scattering is considered.     

A quasi‐static boundary value problem in multi‐surface elastoplasticity: part 2—numerical solution

Multi‐yield elastoplasticity models a material with more than one plastic state and hence allows for refined approximation of irreversible deformations. Aspects of the mathematical modelling and a proof of unique existence of weak solutions can be found in part I of this paper (Math. Models Methods Appl. Sci. 2004). In this part II we establish a canonical time–space discretization of the evolution problem and present various algorithms for the solving really discrete problems. Based on a global Newton–Raphson solver, we carefully study and solve elementwise inner iterations. Numerical examples illustrate the model and its flexibility to allow for refined hysteresis curves. Copyright © 2005 John Wiley & Sons, Ltd.     

低丘红壤区茶园施用茶叶专用肥的效果

研究了在低丘红壤区施用不同有机质含量的专用有机无机复合肥料对茶叶的产量和品质的影响．结果表明：在总养分含量相同的情况下，茶叶品质和产量随着专用肥料中有机质量含量的增加有一定的提高，其中，茶叶产量提高达显著水平，增产幅度高达29.94％；茶叶品质有显著改善；经济效益有较大提高，投入产出比达1：24．52．     

Stabilité du front d'un tunnel en milieu frottant : un nouveau mécanisme de rupture 3DTunnel face stability in frictional material: a new 3D failure mechanism

Within the framework of the kinematic approach of yield design theory, a new three-dimensional mechanism is proposed for the stability analysis of the tunnel face in cohesive-frictional material. The geometry of the mechanisms considered are based on logarithmic-spirals and depends on two parameters. The optimization leads to a critical mechanism which compares remarkably well with experimental and numerical observations. The kinematic bound of the critical face pressure is better than existing approaches, and is very close to value obtained by 3D numerical computations. To cite this article: D. Subrin, H. Wong, C. R. Mecanique 330 (2002) 513–519.