Adsorption of malachite green onto bentonite: Equilibrium and kinetic studies and process design

The adsorption of malachite green onto bentonite in a batch adsorber has been studied. The effects of contact time, initial pH and initial dye concentration on the malachite green adsorption by the bentonite have been studied. Malachite green removal was seen to increase with increasing contact time until equilibrium and initial dye concentration, and the adsorption capacity of bentonite was independent of initial pH in the range 3–11. Four kinetic models, the pseudo first- and second-order equations, the Elovich equation and the intraparticle diffusion equation, were selected to follow the adsorption process. Kinetic parameters; rate constants, equilibrium adsorption capacities and correlation coefficients, for each kinetic equation were calculated and discussed. It was shown that the adsorption of malachite green onto bentonite could be described by the pseudo second-order equation. The experimental isotherm data were analyzed using the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich equations. Adsorption of malachite green onto bentonite followed the Langmuir isotherm. The thermodynamic parameters, such as ΔH, ΔS and ΔG, were also determined and evaluated. A single stage batch adsorber was designed for different adsorbent mass/treated effluent volume ratios using the Langmuir isotherm.     

Comparison of particle size distribution of celestite mineral by machine vision ΣVolume approach and mechanical sieving

A reliable and accurate measurement of particle size and particle size distribution (PSD) is central to characterization of particulate minerals. Using mineral celestite (SrSO₄) as the test material, an inexpensive machine vision approach as an alternative to standard mechanical sieving was proposed and results were compared. The machine vision approach used a user-coded ImageJ plugin that processed the digital image in a sieveless manner and automated the PSD analysis. A new approach of employing sum of volumes (ΣVolume) as weighting factor was developed and utilized in the ASABE standard PSD analysis. The plugin also evaluated 22 significant dimensions characterizing samples and 21 PSD parameters. According to Folk and Ward's classification, the PSD of ball-milled celestite was “very finely skewed” and “leptokurtic”. The PSD of celestite followed a lognormal distribution, and the plot against particle size exhibited almost a linear trend for both machine vision and mechanical sieving methods. The cumulative undersize PSD characteristics of both methods matched closely when the width-based mechanical sieving results were transformed to lengths by applying the shape factor (width/length). Based on the study, this machine vision approach can be utilized for PSD analysis of particulate minerals and similar products.     

Union leadership and member attitudes: A multi-level analysis.

Analyses of union leadership roles show that union presidents should have both a within-union focus and an external focus. The authors combined multi-level survey data from 3,871 union members in 248 local teachers' unions with archival and field staff data to examine relationships between leadership and members' perceptions of union instrumentality and justice, union commitment, and participation. The results showed significant union-level effects on members' beliefs about, and attitudes toward, their unions, attributable to the presidents' internal and external leadership, wage outcomes, and union characteristics. Relationships between internally focused leadership and members' loyalty and willingness to work for the union were partially mediated by perceptions of union instrumentality and justice. These perceptions fully mediated the relationship between externally focused leadership and union loyalty. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Allocating resources to research and development projects in a competitive environment

Firms who are involved in R&D activities are often “racing” against competitors to become the lirst to attain the desired breakthrough. The goal might indeed be to "beat" the competitors in as many such R&D races as possible. However, when resources are limited, and competitors' budget allocation to these R&D activities unknown, the challenge becomes to devise a method of allocating R&D budgets to activites in a strategically “optimal” way. We model the decision problem of a firm wishing to allocate a fixed budget among several activities, so as to maximize the expected profit from the activities it captures. The probability of capturing an activity is an increasing function of one's allocation to it, and a decreasing function of the competitor's allocation. For a specific plausible capture-probability function, we find the optimal allocation between two activities conditional on the competitor's allocation (the “reaction curve”). Nash and Stackelberg equilibria for that model are then characterized. Wc also briefly explore the implications of more general, or different, capture-probability functions.     

A Natural Language-Based Interface for Querying a Video Database

The authors developed a video database system called BilVideo that provides integrated support for spatiotemporal, semantic, and low-level feature queries. As a further development for this system, the authors present a natural language processing-based interface that lets users formulate queries in English and discuss the advantage of using such an interface     

Response of rough and acute surfaces of pyrite with 3-D approach to the flotation

This study presents a new 3-D approach to determine the morphological properties of pyrite particles by Brunauer — Emmett — Teller (BET) nitrogen gas adsorption and Permaran methods. The obtained parameters, which are surface roughness and acuteness, were correlated with the floatability of those mineral particles. The flotation performances of the pyrite particles ground in different mills were also evaluated by a Hallimond tube. The results showed that lower roughness and acuteness values caused higher flotation recoveries for the pyrite particles considered. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 95–104, July–August, 2006     

Application of a hybrid model of mushy zone to macrosegregation in alloy solidification

Solidification of an aqueous ammonium chloride (NH₄Cl-H₂O) solution inside a two-dimensional cavity is numerically investigated using a continuum mixture mathematical model. The mushy region where solid and liquid phases co-exist is considered a non-Newtonian fluid below a critical solid fraction, and a porous medium thereafter. This critical solid fraction is chosen as that corresponding to the coherency point, where a solid skeleton begins to form. The numerical results show that the solidification of a hypereutectic NH₄Cl-H₂O solution is mainly characterized by the rejection of solute at the mushy region and double diffusive convection induced by the opposing solutal and thermal buoyancy forces. The mathematical model agrees satisfactorily with the available experimental and numerical data.     

新疆地区密点麻蜥不同亚种体与尾中14种元素分析比较

用原子吸收分光光度计测定了新疆地区密点麻蜥不同亚种体与尾中14种元素的含量，发现其K、Ca、Mg、Fe、Zn等元素的含量都比较丰富；有毒元素Pb含量均较低：仅在叶城亚种体中含有Cd，且含量极低；密点麻蜥不含有Co、Ni，并讨论了这些元素与其药用机理的关系，为密点麻蜥的进一步开发利用提供一定的科学依据。