The influence of semi-rigid connections on the shakedown of elasto-plastic frames

The main structural elements of steel framed multi-storey structures are the columns, the beams and their connections. The assumption has been widely applied in the past that the connections are either rigid or pinned. The actual behaviour of the connections is however somewhere between these limits, they are semi-rigid. The aim of this paper is to analyze the effect of the semi-rigid connections on the shakedown of steel structures under multi-parameter static loading. In the analysis, to control the plastic behavior of the structure, bound on the complementary strain energy of the residual forces is applied. The formulation of the problem yields to nonlinear mathematical programming. The results of the numerical calculation show that the semi-rigid connections can influence significantly the magnitude of the shakedown parameter. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

渣油中沥青质分子颗粒尺寸及其胶粒模型研究

分别以苯和硝基苯为溶剂测定了大庆、胜利、孤岛和辽河减压渣油沥青质、胶质和芳香分的分子量；依据球形分子模型计算了这些物质的分子尺寸；构筑了渣油中沥青质胶粒（胶团）模型，并依此计算了渣油中沥青质胶粒尺寸。结果表明，以硝基苯为溶剂所测沥青质分子量更能反应沥青质化学结构的实质；就原始沥青质来说，以苯为溶剂测得的沥青质分子直径为3.8 nm～5.0 nm,以氯代苯为溶剂测得的分子直径为3.2 nm～3.7 nm,以硝基苯为溶剂测得的分子直径为2.8 nm～3.2 nm；辽河、胜利与大庆减压渣油中沥青质的胶粒直径为10.0 nm～11.0 nm，孤岛减压渣油中沥青质的胶粒直径为9.0 nm～10.0 nm。     

The main problems of the multiple coverage method of a common depth point and data processing for this method

A flaw of fundamental nature in foundations and pratical applications of efficient seismic prospecting is discussed. The authors invite the geophysical community to organize a broad discussion in the seismic literature devoted to basic problems of seismic prospecting and its applications. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 225, 1997, pp. 240–262. Translated by N. S. Zabavnikova and T. N. Surkova     

Effect of a magnetic field on MnAs0.88P0.12 below 80 K

MnAs_0.88P_0.12 has been studied by powder neutron diffraction in external magnetic fields up to 15.2 kOe and temperatures down to 4.2 K. MnAs_0.88P_0.12 takes the MnP type atomic arrangement and exists in para-, ferro- and different (essentially) helimagnetic states. The observation of a double 000^± satellite at 4.2 K < T 70 K adds further evidence to the chain of arguments for distinction between the helimagnetic states H'_a (4.2 K < T < T_S,1 ≈ 70 K) and H_a (T_S,2 ≈ 180 K < T < T_N = (243 ± 5) K). External magnetic fields at 4.2 K < T < 70 K evoke a new magnetic state, which is also characterized by a satellite doublet, and is tentatively designated H'_a,fan.     

Time distribution of γ-rays from spontaneous fission of 252Cf at short times

The gross time distribution of γ-rays from spontaneous fission of ²⁵²Cf has been measured in the time range 10^?14?10^?10 s after fission for γ-ray energies greater than 0.15 MeV. The measurements have been made by a new method based upon the solid angle aberration. From the measured correlation between half-lives and γ-ray transition energies it is concluded that the transitions are predominantly E2, single-particle transitions at high energies, and mostly vibrational and rotational transitions at lower energies. Some contribution of E1 transitions and M1-E2 mixtures cannot be excluded, however. It was found that about 30% ofthe γ-rays emitted within 12 ns with energies greater than 0.10 MeV, have half-lives shorter than 1 ps and about 52 % half-lives between 1 and 100 ps. The relative yield of γ -rays and γ-ray energy in the time range 10^?14 to 1.2 × 10^?7 s ater fission is given.     

Development of an X-ray fluorescence spectrometric method for the analysis of atmospheric aerosol samples

A simple, rapid method was developed for the analysis of aerosol samples by X-ray fluorescence spectrometry. Aerosol measurements were made using various sample supports (Whatman and Teflon filters, Prolene® foil). The calibration procedure was carried out by dripping 500 μl of a gradually diluted multi-elemental standard solution (CertiPUR® 11355) onto the top of the sample supports, which were then dried at ambient temperature. Thirteen elements, namely Na, Al, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr and Pb were calibrated and quantified. The optimal measurement parameters (excitation conditions, measuring times for each element) were determined on the basis of blank values and the amplitude of the signals. The filters were covered with Ta or Re plates to ensure infinite thickness for the penetration depth of the primary X-ray beam. It was also demonstrated that these plates served as a secondary target. The accuracy, precision and detection limits (0.01–0.18 mg/kg) were calculated. All the analytical parameters were better when Teflon filters and Prolene® foil were used than in the case of Whatman quartz fibre filters.     

Spektrophotometrische Methode zur gleichzeitigen Bestimmung von Uranium und Thorium in Wasser

A method for the simultaneous determination of the uranium and thorium content in various types of natural waters, has been worked out. The method is based on the separation of uranium from thorium, and their subsequent purification on strong basic anion exchange resin. An increased chemcial yield, precision and selectivity result in this manner. The assay of uranium and thorium is performed spectrophotometrically in the form of their Arsenazo III complex. Under the studied conditions, the spectrophotometric method can be used instead of the fluorimetric method, without the difficulties of the latter.