Search results for "Sol"
showing 10 items of 23782 documents
Stabilized branch-and-price algorithms for vector packing problems
2018
Abstract This paper considers packing and cutting problems in which a packing/cutting pattern is constrained independently in two or more dimensions. Examples are restrictions with respect to weight, length, and value. We present branch-and-price algorithms to solve these vector packing problems (VPPs) exactly. The underlying column-generation procedure uses an extended master program that is stabilized by (deep) dual-optimal inequalities. While some inequalities are added to the master program right from the beginning (static version), other violated dual-optimal inequalities are added dynamically. The column-generation subproblem is a multidimensional knapsack problem, either binary, boun…
Best proximity point theorems for proximal cyclic contractions
2017
The purpose of this article is to compute a global minimizer of the function $$x\longrightarrow d(x, Tx)$$ , where T is a proximal cyclic contraction in the framework of a best proximally complete space, thereby ensuring the existence of an optimal approximate solution, called a best proximity point, to the equation $$Tx=x$$ when T is not necessarily a self-mapping.
Metakaolin geopolymer characterization and application for ammonium removal from model solutions and landfill leachate
2016
Abstract Geopolymers are aluminosilicate compounds that are amorphous analogues of zeolites, and thus possess similar cation-exchange properties. Geopolymers have been successfully applied to remove toxic metals and organic dyes from aqueous solutions. In this study, geopolymer was synthesized from metakaolin and applied to remove ammonium (NH 4 + ) from model solutions and landfill leachate. Geopolymerization increased the ammonium removal capacity, surface area and average pore width and changed the chemical structure of metakaolin. The maximum NH 4 + removal capacity of the geopolymer was 21.07 mg g − 1 which was 46% higher than the capacity of the reference clinoptilolite–heulandite zeo…
Kinetic, isotherm and thermodynamic studies of the adsorption of methylene blue dye onto agro-based cellulosic materials
2015
AbstractThe purpose of this work is to establish the optimal experimental conditions for the removal of methylene blue (MB-as model basic dye) from aqueous solution by adsorption onto four agro-based materials, namely, cedar sawdust, pine sawdust, wheat straw, and Provence cane Arundo donax. Results show that an increase in acidity or ionic strength of the medium has generally a negative effect on the discoloration yield. From the data of pH effect, there is no need to change the initial pH of the MB solution to be treated. Equilibrium was reached after 20−30 min of agitation when cedar sawdust, pine sawdust, and Provence cane are used as adsorbents. However, in the case of wheat straw, an …
Strategies of Identification of a Base-Isolated Hospital Building by Coupled Quasi-Static and Snap-Back Tests
2020
In this paper, the description of a series of quasi-static pushing tests and dynamic snap-back tests is proposed, involving the base-isolated emergency building of the Palermo university hospital. The base isolation system is characterized by a set of double-curved friction pendulum isolators placed on the top of the columns of the underground level, characteristics that cannot be found in the experimental studies available in the literature. The aim of the work was to investigate the static and dynamic properties of the building in question and comparing the in-situ results with the characteristics assigned during the design process and to assess the level of agreement. Static lateral push…
Young People and Political Activism in Moldova
2020
The election of a Socialist and pro-Russian candidate in December 2016 as president of Moldova marks a new turn in Moldovan politics. This is in contrast with the pro-Western attitudes of the previous government. Political instability and changing international orientations, as emphasized by this article, are partly due to political alternative victories of parties supported by different social groups. Focusing on young people's activism, the article underlines the differentiation between the political success made possible by street protests in April 2009 and the political failure in December 2016. The findings may add a new explanation to Moldova's permanent instability.
Removal of Hexavalent Chromium from Aqueous Solutions Using Biopolymers
2018
AbstractTwo biopolymers were prepared by reaction of chestnut and quebracho tannins with gelatin extracted from untanned hide wastes. Obtained biopolymers were evaluated as adsorbents for removing ...
A method for reclaiming nutrients from aquacultural waste for use in soilless growth systems
2020
Abstract The aim of this work was to develop a method that allows the recovery of nutrients from aquaculture sludge, not only to alleviate the disposal problem, but also to address the future scarcity of non-renewable fertilizers. This method includes two steps: Nutrient mobilization using aerobic digestion followed by solids precipitation using chitosan as the flocculant. The aerobic digestion experiments were conducted in aerated batch reactors, while a jar test apparatus was used to assess the capacity of chitosan to remove total suspended solids (TSS) and turbidity. During aerobic digestion, the concentration of soluble N (sum of NH4-N, NO2-N, NO3-N) increased from 181 mg/L at the start…
Characterization of the porous structure of Chilean volcanic soils by nitrogen adsorption and mercury porosimetry
2004
Pore volume, specific surface area (SSA), and total intragranular porosity (TIP) of Chilean soils derived from volcanic materials were studied. Soil samples involving the 0-15 and 15-30 cm depth of virgin and cultivated Collipulli (Ultisol) and Diguillin (Andisol) soils at two particle size fractions (<1 mm and <2 µm) were considered. From mercury porosimetry and N2 adsorption, mainly mesopores (pore diameter, dpore, about 10 nm) were determined for <1 mm Collipulli samples. Diguillin <1 mm soil shows macroporosity with dpore from 70 nm to 7000 nm. The clay fraction of Collipulli has macropores (dpore from 2000 nm to 40000 nm) and mesopores (dpore from 3 nm to 23 nm), while for Diguillin cl…
Seismic behavior of structures equipped with variable friction dissipative (VFD) systems
2021
Usually, to mitigate the stresses in framed structures, different strategies are used. Among them, base isolation, viscous/friction/metallic yielding dampers and tuned mass dumpers have been widely investigated. Fluid Viscous Dampers (FVD) probably result the most diffused for the simplicity in the applications. However, these type of dampers request limited interstorey drifts to avoid dangerous effects. Further, they have an elevate cost. On the contrary, friction dampers are not so expensive but request high interstorey drifts to give a significant contribute in the dissipation of energy during an earthquake. In this paper an approach for the energy dissipation by friction, modified with …