Fluoride removal from water by zirconium (IV) doped chitosan bio-composite

Water containing fluoride above 1.5 mg/L leads to health and environmental harms that creates skeletal and dental fluorosis. Adsorption technique prominently removes fluoride from water and its competence is reliant on development of recyclable, environmentally benign adsorbents. Many reported sorbents for defluoridation below stringent level 1.5 mg/L, displayed low to moderate adsorption capacity at varied concentrations and pH. Besides, viable defluoridation techniques are usually unsuccessful in developing countries. In this novel, cheap and efficient porous chelating resin, chitosan doped 20% zirconium (IV) with control morphologies were synthesized for delfuoridation. This bio-composite was at par with commercial alumina to mitigate water fluoride limit up to 1 to 1.5 mg/L. Effect of parameters namely pH, adsorbent dose, contact time and initial fluoride concentration were studied in batch scale. Kinetic data showed a rapid adsorption, indicated practicable operations in packed column. Findings encourage blending with other polymers as an effective option for defluoridation on a large scale.Key words: Fluorosis, chitosan, zirconium, bio-composite, defluoridation, water

Bending of Shear Deformable Plates Resting on Winkler Foundations According to Trigonometric Plate Theory

A trigonometric plate theory is assessed for the static bending analysis of plates resting on Winkler elastic foundation. The theory considers the effects of transverse shear and normal strains. The theory accounts for realistic variation of the transverse shear stress through the thickness and satisfies the traction free conditions at the top and bottom surfaces of the plate without using shear correction factors. The governing equations of equilibrium and the associated boundary conditions of the theory are obtained using the principle of virtual work. A closed-form solution is obtained using double trigonometric series. The numerical results are obtained for flexure of simply supported plates subjected to various static loadings. The displacements and stresses are obtained for three different values of foundation modulus. The numerical results are also generated using higher order shear deformation theory of Reddy, first order shear deformation theory of Mindlin, and classical plate theory for the comparison of the present results

ANALYSIS AND DESIGN OF THREE LEGGED 400KV DOUBLE CIRCUIT STEEL TRANSMISSION LINE TOWERS

ABSTRACT Transmission line towers constitute about 28 to 42 percent of the cost of the transmission line. The increasing demand for electrical energy can be met more economically by developing different light weight configurations of transmission line towers. The present work describes the analysis and design of three legged self-supporting 400 kV double circuit steel transmission line towers models with an angle and tube sections. In this study constant loading parameters including wind forces as per IS: 802 (1995) are taken into account in both models. The efforts have been made to do 3D analysis of tower considering all the members of the space truss as primary members. STAAD. Pro program has been used to analysis and design the members of 400 kV double circuit tower have deviation angle 2 degree. The maximum sag and tension calculations of conductor and ground wire as per IS: 5613 (Part 3/ Sec 1) 1989. The comparative study is presented here with respective to axial forces, deflections, maximum sectional properties, critical loading conditions between both models of towers. The study shows that tower with tube sections are efficient and have better forceweight ratio including 20.6% saving in weight of steel with tubes against steel with angles in three legged transmission line tower

Bending and free vibration analysis of thick isotropic plates by using exponential shear deformation theory

This paper presents a variationally consistent an exponential shear deformation theory for the bi-directional bending and free vibration analysis of thick plates. The theory presented herein is built upon the classical plate theory. In this displacement-based, refined shear deformation theory, an exponential functions are used in terms of thickness co-ordinate to include the effect of transverse shear deformation and rotary inertia. The number of unknown displacement variables in the proposed theory are same as that in first order shear deformation theory. The transverse shear stress can be obtained directly from the constitutive relations satisfying the shear stress free surface conditions on the top and bottom surfaces of the plate, hence the theory does not require shear correction factor. Governing equations and boundary conditions of the theory are obtained using the dynamic version of principle of virtual work. The simply supported thick isotropic square and rectangular plates are considered for the detailed numerical studies. Results of displacements, stresses and frequencies are compared with those of other refined theories and exact theory to show the efficiency of proposed theory. Results obtained by using proposed theory are found to be agree well with the exact elasticity results. The objective of the paper is to investigate the bending and dynamic response of thick isotropic square and rectangular plates using an exponential shear deformation theory

An accurate beam theory and its first-order approximation in free vibration analysis

An infinite system of one-dimensional differential equations is derived from the two-dimensional theory of elasticity by expanding the displacement field in a series of trigonometrical functions together with a linear term. Since the trigonometrical functions are pure thickness-vibration modes of infinite plates or beams with the top and bottom surfaces being free, the differential equations and the corresponding boundary conditions serve as the basis of an accurate beam theory for vibration analysis, named Lee's beam theory (LBT). Naturally, a high-order set of the infinite system should be quite useful in the analysis of beams at high frequencies. With the objective of vibration analysis of beams, this paper focuses on the first-order approximation, which leads to a first-order shear deformation beam theory for flexural vibrations (LBT1st). The differential equations in LBT1st are equivalent to those in Timoshenko's beam theory (TBT). The most important difference between LBT1st and TBT is the different field displacements. For the assessment of the accuracy of LBT1st, the numerical results of frequencies of free vibrations, frequency spectra and mode shapes of beams with classical boundary conditions are obtained and compared with those by TBT and plane stress problem of elasticity. Considering the plane stress problem as a reference, LBT1st is slightly more accurate in describing the field shapes of beams than TBT. Therefore, LBT1st, as well as LBT, is an addition to the existing beam theories with improved accuracy for the vibration analysis of beams and their combinations