922 research outputs found
Removal of Arsenic (III) from groundwater applying a reusable Mg-Fe-Cl layered double hydroxide
BACKGROUND:
Layered double hydroxide compounds (LDHs) have been applied for the removal of oxyanions including arsenate (As(V)). However, the aim of this present research is to develop a LDH to treat arsenite (As(III)). Both batch and column sorption studies were conducted to assess the effect of LDH dosage, contact time, solution pH and initial As(III) concentrations on the As(III) removal performance. The potential re-use of this sorbent was also investigated.<p></p>
RESULTS: For 2âgâLâ1 of Mg-Fe-Cl LDH, As(III) in test solution can be reduced from 400â”gâLâ1 to <10â”gâLâ1 after a contact time of 2âh. High As(III) concentration in Bangladesh groundwater can be reduced to meet the national drinking water standards (<50â”gâLâ1). The maximum adsorption capacity of As(III) by Mg-Fe-Cl LDH is 14.6âmgâgâ1-LDH. Further, reusability of this sorbent was at least 20 cycles of regeneration with effective As(III) removal between 93.0 and 98.5%. Moreover, As(III) removal was unaffected by the solution pH but affected by the co-existing competing anions and concentration of As(III). Finally, the main mechanism of As(III) removal by Mg-Fe-Cl LDH was suggested to be chemical sorption together with anion and ligand exchange with interlayer Clâ and OHâ ions.<p></p>
CONCLUSION: High efficiency of sorption of As(III) by the developed Mg-Fe-Cl LDH was demonstrated in this study which is generally not the case for most other sorbent materials. Pilot-scale trials are needed to explore the suitability of full application of the developed Mg-Fe-Cl LDH for the removal of As(III).<p></p>
Basis risk and property derivative hedging in the UK : implications of the 2007 IPF Study of tracking error
Thesis (S.M.)--Massachusetts Institute of Technology, Program in Real Estate Development in Conjunction with the Center for Real Estate, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 65).This thesis examines how the basis risk affects property derivative hedging in the UK market, based on the tracking error (basis risk) report from the Investment Property Forum study in 2007 (the IPF Study). The thesis first analyzes the risks relevant to hedging and defines the basis risk. Considering hedgers with different objectives measure hedging efficiency differently, this thesis divides the hedging users into two major categories: ÎČ-Avoidance hedgers and a-Usage hedgers. Each of these has two sub-ordinate groups. In order to quantify the basis-risk influences on hedging, a Monte Carlo simulation designed for short contract of the swap is used. Basis risks of portfolios with different sizes are selected from the IPF Study. To shed light on different hedging uses, three scenarios are tested based on different assumptions on the expected alpha and leverage. Other relevant elements are also studied, such as the price of the debt and the swap. The analysis results in a useful reference for investors who are interested in eliminating portfolio risks with hedging strategies. In the end, the thesis suggests avenues for the further study.by Jia Ma.S.M
A General Approach for the Exact Solution of the Schrodinger Equation
The Schr\"{o}dinger equation is solved exactly for some well known
potentials. Solutions are obtained reducing the Schr\"{o}dinger equation into a
second order differential equation by using an appropriate coordinate
transformation. The Nikiforov-Uvarov method is used in the calculations to get
energy eigenvalues and the corresponding wave functions.Comment: 20 page
Low rank decompositions for sum of squares optimization
Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2006.Includes bibliographical references (leaves 77-79).In this thesis, we investigate theoretical and numerical advantages of a novel representation for Sum of Squares (SOS) decomposition of univariate and multivariate polynomials. This representation formulates a SOS problem by interpolating a polynomial at a finite set of sampling points. As compared to the conventional coefficient method of SOS, the formulation has a low rank property in its constraints. The low rank property is desirable as it improves computation speed for calculations of barrier gradient and Hessian assembling in many semidefinite programming (SDP) solvers. Currently, SDPT3 solver has a function to store low rank constraints to explore its numerical advantages. Some SOS examples are constructed and tested on SDPT3 to a great extent. The experimental results demonstrate that the computation time decreases significantly. Moreover, the solutions of the interpolation method are verified to be numerically more stable and accurate than the solutions yielded from the coefficient method.by Jia Li Sun.S.M
Bound state solutions of the Dirac-Rosen-Morse potential with spin and pseudospin symmetry
The energy spectra and the corresponding two- component spinor wavefunctions
of the Dirac equation for the Rosen-Morse potential with spin and pseudospin
symmetry are obtained. The wave ( state) solutions for this
problem are obtained by using the basic concept of the supersymmetric quantum
mechanics approach and function analysis (standard approach) in the
calculations. Under the spin symmetry and pseudospin symmetry, the energy
equation and the corresponding two-component spinor wavefunctions for this
potential and other special types of this potential are obtained. Extension of
this result to state is suggested.Comment: 18 page
Efeito do ensacamento dos frutos no controle de pragas e doenças e na qualidade e maturação de maçãs âFuji Supremaâ.
O objetivo deste trabalho foi avaliar a eficiĂȘncia de embalagens de diferentes materiais para a proteção contra pragas e doenças e seu efeito sobre a qualidade fĂsico-quĂmica, maturação e teor de cĂĄlcio (Ca) em maçãs âFuji Supremaâ. O experimento foi desenvolvido nas safras de 2007/2008 e 2008/2009, em pomar manejado sob o sistema orgĂąnico, localizado na regiĂŁo de SĂŁo Joaquim (SC). O pomar era composto por plantas de dez anos de idade da cultivar Fuji Suprema, sobre porta-enxerto âMarubakaidoâ, com interenxerto âEM-9â. Depois do raleio manual, aproximadamente 40 dias apĂłs a plena floração, os frutos foram ensacados com embalagens plĂĄsticas transparentes microperfuradas ou de tecido nĂŁo texturizado (TNT). Os frutos foram mantidos ensacados atĂ© a colheita. A testemunha foi constituĂda por frutos nĂŁo ensacados. Na colheita, os frutos foram avaliados quanto aos danos provocados por mosca-das-frutas (Anastrepha fraterculus), mariposa oriental (Grapholita molesta) e lagarta enroladeira (Bonagota salubricola). As doenças foram avaliadas pela incidĂȘncia de sarna da macieira (Venturia inaequalis), podridĂŁo amarga (Colletotrichum gloeosporioides) e podridĂŁo carpelar (Alternaria sp., Fusarium sp.). TambĂ©m foi avaliada a incidĂȘncia de distĂșrbios fisiolĂłgicos ârussetingâ e âbitter pitâ, atributos fĂsico-quĂmicos de maturação e qualidade e o teor de Ca nos frutos. Independentemente do tipo de embalagem verificou-se que o ensacamento Ă© prĂĄtica eficaz na proteção contra o ataque de insetos, mas nĂŁo reduz a incidĂȘncia e o desenvolvimento de doenças nos frutos. Na safra de 2008/2009, o ensacamento dos frutos aumentou o teor de Ca e reduziu a incidĂȘncia de âbitter pitâ, e aumentou a incidĂȘncia do ârussetingâ. O ensacamento dos frutos antecipou a maturação, especialmente com embalagem plĂĄstica transparente microperfurada, e reduziu a coloração vermelha, especialmente com embalagem TNT
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