5,155 research outputs found
Heterogeneous Extractive Batch Distillation of Chloroform - Methanol – Water : Feasibility and Experiments
No full textA novel heterogeneous extractive distillation process is considered for separating the azeotropic mixture chloroform – methanol in a batch rectifying column, including for the first time an experimental validation of the process. Heterogeneous heavy entrainer water is selected inducing an unstable ternary heteroazeotrope and a saddle binary heteroazeotrope with chloroform (ternary diagram class 2.1-2b). Unlike to well-known heterogeneous azeotropic distillation process and thanks to continuous water feeding at the column top, the saddle binary heteroazeotrope chloroform – water is obtained at the column top, condensed and further split into the liquid – liquid decanter where the chloroform-rich phase is drawn as distillate. First, feasibility analysis is carried out by using a simplified differential model in the extractive section for determining the proper range of the entrainer flowrate and the reflux ratio. The operating conditions and reflux policy are validated by rigorous simulation with ProSim Batch Column® where technical features of a bench scale distillation column have been described. Six reproducible experiments are run in the bench scale column matching the simulated operating conditions with two sequentially increasing reflux ratio values. Simulation and experiments agree well. With an average molar purity higher than 99%, more than 85% of recovery yield was obtained for chloroform and methanol
Practical Short Signature Batch Verification
No full textIn many applications, it is desirable to work with digital signatures that are short, and yet where many messages from different signers be verified very quickly. RSA signatures satisfy the latter condition, but are generally thousands of bits in length. Recent developments in pairing-based cryptography produced a number of “short” signatures which provide equivalent security in a fraction of the space. Unfortunately, verifying these signatures is computationally intensive due to the expensive pairing operation. Toward achieving “short and fast” signatures, Camenisch, Hohenberger and Pedersen (Eurocrypt 2007) showed how to batch verify two pairing-based schemes so that the total number of pairings was independent of the number of signatures to verify. In this work, we present both theoretical and practical contributions. On the theoretical side, we introduce new batch verifiers for a wide variety of regular, identity-based, group, ring and aggregate signature schemes. These are the first constructions for batching group signatures, which answers an open problem of Camenisch et al. On the practical side, we implement each of these algorithms and compare each batching algorithm to doing individual verifications. Our goal is to test whether batching is practical; that is, whether the benefits of removing pairings significantly outweigh the cost of the additional operations required for batching, such as group membership testing, randomness generation, and additional modular exponentiations and multiplications. We experimentally verify that the theoretical results of Camenisch et al. and this work, indeed, provide an efficient, effective approach to verifying multiple signatures from (possibly) different signers
Design of a Period Batch Control planning system for cellular manufacturing
No full textThesis 1 Introduction 2 Relationships between cells 3 Period Batch Control 4 Design factors for basic unicycle PBC systems 5 Models and methods for determining a period length P 6 Modelling the trade-off between N and P 7 Determining a configuration of the PBC system 8 Co- ordination between cells and PBC system design 9 Conclusions and further research Appendices: Short case descriptionsProduction planning Operations management
J.C. Steyn Collection index
No full textThis index describes the J. C. Steyn collection which includes background material for 3 biographies by J.C. (Jaap) Steyn namely N.P. van Wyk Louw, P.J. Cillié and MER (M.E. Rothman). Prof. J.C. Steyn (1939-) is an educationist, linguist and author. Correspondence ; clippings ; photographs ; book reviews ; articles ; speeches ; varia compiled in 23 pamphlet boxes
Product Innovation Knowledge Transfer for Developing Countries: Towards a systematic Transfer Approach
No full textThe transfer of knowledge on product innovation to small- and medium-sized enterprises and local knowledge institutions in developing countries is expected to be one of the key drivers for competiveness and economical growth, and a part of the solution to environmental and social challenge. In that respect, this PhD study focuses on how the process of the current knowledge transfer takes place and how it can be improved. A combination of literature review and empirical research has resulted into a conceptual framework to describe the complex and dynamic process of product innovation knowledge transfer to developing countries. In order to improve this process, a systematic approach has been developed and operationalized by a needs assessment tool and a design manual: The UNEP Design for Sustainability for Developing Economies (D4S-DE) Manual (www.d4s-de.org). Both tools have been tested in practice by practitioners and have been evaluated by an academic review board.Design EngineeringIndustrial Design Engineerin
Parameters influencing calcium phosphate precipitation in granular sludge sequencing batch reactor
No full textParameters influencing calcium phosphate precipitation in Calcium phosphate precipitation inside microbial granules cultivated in a granular sequenced batch reactor (GSBR) has been demonstrated to contribute to phosphorus removal during wastewater treatment. Whereas hydroxyapatite (HAP) is proven to accumulate in the granule, the main calcium phosphate precursors that form prior to HAP are here investigated. A separate batch reactor was used to distinguish reactions involving biological phosphate removal from physicochemical reactions involving phosphateprecipitation in order to establish the kinetics and stoichiometry of calcium phosphate formation. Experiments and simulations with PHREEQC and AQUASIM software support the assumption that amorphous calciumphosphate (ACP) is the intermediary in HAP crystallization. The results provide the kinetic rate constants and thermodynamic constants of ACP. The formation of bioliths inside biological aggregates as well as the main parameters that drive their formations are discussed here. Finally, the influence of pH and calcium and phosphate concentrations in the influent was also assessed, in order to determine the contribution of precipitation in the different operating conditions
Where do we draw lines: professional relationship boundaries and the child and youth care practitioner
No full textThe question of professional relationship boundaries is a poignant one, in light of the many boundary grey-zones that are created by the variety of young people’s needs, practice settings and professional relationship contexts within the field of child and youth care. In order to support practitioners’ development of critical thought and awareness of professional boundaries, this paper applies a professional relationship boundaries conceptual framework to child and youth care work, and the literature is consulted to explore the impacts of boundary violations, influences on individual’s boundaries, cues to indicate blurring boundaries, and key strategies to maintain balanced boundaries
Adsorptive iron removal from groundwater
No full text Iron is commonly present in groundwater worldwide. The presence of iron in the water supply is not harmful to human health, however it is undesirable. Bad taste, discoloration, staining, deposition in the distribution system leading to aftergrowth, and incidences of high turbidity are some of the aesthetic and operational problems associated with iron in water supplies. Iron removal from groundwater is, therefore, a major concern for water supply companies using groundwater sources. The WHO recommended guideline value of iron in drinking water is 0.3 mg/l and the EC directive has set a parametric value of 0.2 mg/1. In the Netherlands, the guideline value of iron in drinking water is≤0.05mg/1 and several Dutch water supply companies are aiming at iron concentrations below 0.03 mg/1 to minimise distribution network maintenance costs. Of the different methods available to control iron in water supplies (oxidation-filtration, ion exchange, lime softening, sub-surface iron removal, and sequestration), aeration followed by rapid sand filtration is the most commonly used. Different mechanisms (physical, chemical, and biological) may contribute to the removal of iron in filters and the dominant mechanism depends on water quality and process conditions applied. Fig. 8. 1 summarises the different mechanisms of iron removal in filters and the steps involved. Under anoxic conditions, adsorption is the only mechanism of iron removal from groundwater. In the presence of oxygen, iron removal can take place via three different mechanisms, namely i) oxidation-floe formation (floe filtration), ii) biological oxidation, and iii) adsorption-oxidation (adsorptive filtration). Under the commonly applied treatment conditions in iron removal plants, the oxidation-floe formation mechanism is commonly believed to be dominant. The adsorptionoxidation mechanism (adsorptive iron removal), however, has several potential advantages over the oxidation-floe formation mechanism, namely longer filter run, shorter filter ripening time, and less backwash water use and sludge production.</p
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