Lower bound estimation of load-carrying capacity of thin-walled structures with intermediate stiffeners

The design of thin structures must take into account the overall instability and the instability of component plates in the form of local buckling. This investigation is concerned with the interactive buckling of thin-walled structures with central intermediate stiffeners under axial compression and/or a constant bending moment. The structures are assumed to be simply supported at the ends. The lower bound estimation of load-carrying capacity on the basis of the post-buckling behaviour of thin-walled structures with imperfections is studied when the distortional deformations are taken into account. The asymptotic expansion established by Byskov and Hutchinson (AIAA J. 15 (1977) 941) is employed in the numerical calculations performed using the transition matrix method. The present paper is a continuation of previous work by the authors (Int. J. Solids Struct. 32 (1995) 1501; 33 (1996) 315; 37 (2000) 3323), where the interactive buckling of thin-walled beam-columns with central intermediate stiffeners in the first- and the second-order approximation were considered. In the solution obtained, the transformation of buckling modes with an increase in the load up to the ultimate load, the effect of cross-sectional distortions and the shear lag phenomenon are included. The results obtained are compared with data reported by other authors.     

Guided self-assembly of nanostructured titanium oxide

A series of nanostructured titanium oxide particles were synthesized by a simple wet chemical method and characterized by means of small-angle x-ray scattering (SAXS)/wide-angle x-ray scattering (WAXS), atomic force microscope (AFM), scanning electron microscope (SEM), transmission electron microscope (TEM), thermal analysis, and rheometry. Tetrabutyl titanate (TBT) and ethylene glycol (EG) can be combined to form either TiO(x) nanowires or smooth nanorods, and the molar ratio of TBT:EG determines which of these is obtained. Therefore, TiO(x) nanorods with a highly rough surface can be obtained by hydrolysis of TBT with the addition of cetyl-trimethyl-ammonium bromide (CTAB) as surfactant in an EG solution. Furthermore, TiO(x) nanorods with two sharp ends can be obtained by hydrolysis of TBT with the addition of salt (LiCl) in an EG solution. The AFM results show that the TiO(x) nanorods with rough surfaces are formed by the self-assembly of TiO(x) nanospheres. The electrorheological (ER) effect was investigated using a suspension of titanium oxide nanowires or nanorods dispersed in silicone oil. Oil suspensions of titanium oxide nanowires or nanorods exhibit a dramatic reorganization when submitted to a strong DC electric field and the particles aggregate to form chain-like structures along the direction of applied electric field. Two-dimensional SAXS images from chains of anisotropically shaped particles exhibit a marked asymmetry in the SAXS patterns, reflecting the preferential self-assembly of the particles in the field. The suspension of rough TiO(x) nanorods shows stronger ER properties than that of the other nanostructured TiO(x) particles. We find that the particle surface roughness plays an important role in modification of the dielectric properties and in the enhancement of the ER effect.     

Kinoform apodization

Abstract

A new apodization principle is introduced, according to which the amplitude function is realized as a varying diffraction efficiency of the multistep phase diffractive element. A proper modification of the phase-step heights within the apodization region allows one to redirect light from the main diffraction order into its conjugate, simultaneously avoiding the presence of light in the two nearest neighbouring orders. The analysis is confirmed by the simulation results.     

Influence of Statistical Errors on Size Distributions Obtained from Dynamic Light Scattering Data: Simulation of Experimental Noise in the Intensity Autocorrelation Function

Abstract

In this paper, the statistical error courses in the intensity autocorrelation function are simulated and the influence of these errors on size distribution reproducibility is checked. As a numerical method, the constrained regularization method with the Contin program was used and autocorrelation functions were calculated on the basis of the monomodal Schulz distribution. The influence of the regularization parameter α on the recalculated size distributions has also been checked. It has been found that the reproducibility of original size distributions can be lost because of the existence of slow-frequency components in noisy data.     

2D Model of Guide Vane for Low Head Hydraulic Turbine： Analytical and Numerical Solution of Inverse Problem

Low-head hydraulic turbines are the subjects to individual approach of design. This comes from the fact that hydrological conditions are not of a standard character. Therefore, the design method of the hydraulic turbine stage has a great importance for those who may be interested in such an investment. As a first task in a design procedure the guide vane is considered. The proposed method is based on the solution of the inverse problem within the flame of 2D model. By the inverse problem authors mean a design of the blade shapes for given flow conditions. In the paper analytical solution for the simple cylindrical shape of a guide vane is presented. For the more realistic cases numerical solutions according to the axis-symmetrical model of the flow are also presented. The influence of such parameters as the inclination of trailing edge, the blockage factor due to blade thickness, the influence of loss due to dissipation are shown for the chosen simple geometrical example.     

Current Philosophy of Sustainability in Civil Engineering

This paper describes the current status of sustainable development in civil engineering. The discussion covers economy along with “global village” needs, and is supported by information about technology standards combined with notions of ethics, environment, aesthetics, and heritage—the philosophical understanding of the cultural landscape of the society. It is recognized that “true development” cannot be limited to purely technical problems; “human ecology” should be taken into account. The concepts of sustainable development require input from all mankind, but civil engineering professionals can play a particular role here; their spiritual motivation can often be a decisive argument for their material handling. This means that “true development,” referred to as the dignity of man, must be based on the priority of spirit versus matter, of person versus object, of ethics versus technology.     

A comparative study of chelating and cationic ion exchange resins for the removal of palladium(II) complexes from acidic chloride media

The increasing demand for palladium for technological application requires the development of ion exchange chromatography. Recently ion exchange chromatography has developed largely as a result of new types of ion exchangers available on the market of which two types are widely applied. One of them are selective (chelating) and modified ion exchangers and the other one are liquid exchangers. Two types of ion exchange resins such as chelating (Lewatit TP 214, Purolite S 920) and cationic (Chelite S, Duolite GT 73) ion exchangers are used for the recovery of palladium(II) complexes from chloride media (0.1-2.0M HCl-1.0M NaCl-0.0011 M Pd(II); 0.1-2.0M HCl-2.0M NaCl-0.0011M Pd(II)). The influence of concentration of hydrochloric acid, sodium chloride as well as the phase contact time on the degree of recovery of palladium(II) complexes was studied. Moreover, the amount of palladium(II) chlorocomplexes sorbed onto ion exchangers, the working ion exchange capacities and the weight and bed distribution coefficients were calculated in order to judge which of two types of resins possesses the best performance towards palladium(II) complexes.     

The influence of distribution of titanium alloyed into carbon ceramics by the intense plasma pulses on their surface wettability with liquid copper

The paper presents an analysis of wettability and structural properties of the near surface layer of carbon ceramics into which titanium atoms were alloyed using a new method based on the use of high intensity pulsed plasma beams. The influence of various parameters of ceramic pre-treatment process on their wettability with liquid copper is presented and discussed. The information obtained can be useful in designing the ceramic–metal joints and composites.     

Inhomogeneous structure of near-surface layers in the ion-implanted NiTi alloy

This paper reports the application of nitrogen ion implantation for modification of a shape memory alloy. It is known that the problem of creating a protective surface coating for the shape memory alloy is the most acute for potential applications of this material. Thus, the problem of increasing surface protective properties and, at the same time, simultaneous preservation of functional properties of shape memory materials is a subject of research and development [Pelletier H, Muller D, Mille P, Grob J. Surf Coat Technol 2002;158:309.]. The surface characterization of nitrogen implanted (fluence 10¹⁸ cm^?2 and energy 50 keV) equiatomic commercial NiTi alloy samples was performed with the assistance of high resolution transmission electron microscopy (HTEM) techniques and modifications of phase composition before and after irradiation are studied at room and martensitic transformation temperatures by X-ray diffraction methods. Differential scanning calorimetry (DSC, TA Instruments) was used to characterize the transformation sequence and transformation temperatures for the initial and surface-modified materials. Experimental results of an inhomogeneous structure of near-surface layers in the ion-implanted NiTi alloy are discussed in this paper.     

Evaluating the Impact of Mine Groundwater on the Environment

Efficient monitoring of mine groundwater conducted with a standard methodology makes the evaluation of the influence of mine water on the environment easier. The paper examines problems of monitoring and proposes a groundwater monitoring system for existing and flooded abandoned mines. The final effect of mine waters monitoring enables ecochemical and economical evaluation. It also makes it possible to select and use the appropriate proecological technologies for mine waters.