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971.
ABSTRACT

Diffusion dialysis (DD) was proposed as a pretreatment step to reduce the acidity of real sulfate/chloride pregnant leach solutions containing cobalt(II) and nickel(II). Optimum DD conditions that enable reduction of acidity in the feed while maintaining a high rejection level of metal ions present in PLS were proposed, e.g. for 0.06 dm3/min flow of both aqueous phases H+ concentration in the dialysate reached 3.8 and 2.99 M for PLS1 and PLS2, respectively. Acid diffusion coefficients varied from 0.32 ?10 ?6 to 3.15?10?6 m/s and decreased with increasing phase flow rates. Moreover, dialysate neutralization was beneficial for the H+ reduction in the feed.  相似文献   
972.
The dependence of the fold period in poly(ethylene terephthalate) (PET) crystals on overcooling was investigated by the small-angle x-ray diffraction method, for samples crystallized at 150°C to 260°C. The equilibrium melting point Tm, determined simultaneously, was 278°C ± 2°C. Using these results, the surface free energy σe was calculated.  相似文献   
973.
This paper compares the quality and execution times of several algorithms for scheduling service based workflow applications with changeable service availability and parameters. A workflow is defined as an acyclic directed graph with nodes corresponding to tasks and edges to dependencies between tasks. For each task, one out of several available services needs to be chosen and scheduled to minimize the workflow execution time and keep the cost of service within the budget. During the execution ofa workflow, some services may become unavailable, new ones may appear, and costs and execution times may change with a certain probability. Rescheduling is needed to obtain a better schedule. A solution is proposed on how integer linear pro- gramming can be used to solve this problem to obtain optimal solutions for smaller problems or suboptimal solutions for larger ones. It is compared side-by-side with GAIN, divide-and-conquer, and genetic algorithms for various probabilities of service unavailability or change in service parameters. The algorithms are implemented and subsequently tested in a real BeesyCluster environment.  相似文献   
974.
In recent years, Facebook has become the most popular of social networking sites (SNSs). Due to its increasing popularity and rising number of its users, the phenomenon of Facebook has aroused academic interest as well. There has been a growing number of studies on this subject. The aim of this article is to present the main trends in Facebook research and to provide an overview of major empirical findings. Among the most intensively explored topics in Facebook research, studies that concentrate on personality and individual differences among users, the role of self-efficacy, and motivation for using that specific SNS were identified. There is also a growing trend in empirical studies that focuses on testing advanced theoretical models of Facebook usage determinants. Technology acceptance model, presented in this article, is one of the most often used among them. This kind of approach may serve as a suggestion for a methodological conceptualization in the future confirmatory research on Facebook.  相似文献   
975.
The rapid development and expansion of the Internet and the social–based services comprised by the common Web 2.0 idea provokes the creation of the new area of research interests, i.e. social networks on the Internet called also virtual or online communities. Social networks can be either maintained and presented by social networking sites like MySpace, LinkedIn or indirectly extracted from the data about user interaction, activities or achievements such as emails, chats, blogs, homepages connected by hyperlinks, commented photos in multimedia sharing system, etc. A social network is the set of human beings or rather their digital representations that refer to the registered users who are linked by relationships extracted from the data about their activities, common communication or direct links gathered in the internet–based systems. Both digital representations named in the paper internet identities as well as their relationships can be characterized in many different ways. Such diversity yields for building a comprehensive and coherent view onto the concept of internet–based social networks. This survey provides in–depth analysis and classification of social networks existing on the Internet together with studies on selected examples of different virtual communities.  相似文献   
976.
The scope of the paper is an algorithm reconstructing the boundary conditions (heat flux and heat transfer coefficient) in the solidification of pure metals on the grounds of temperature measurements. For the verification of the algorithm experimental data derived in the course of the solidification of aluminum were used. An example of the application of the algorithm for designating the cooling conditions in continuous casting is provided, when the values of temperature at selected points on the boundary of the casting are known.  相似文献   
977.
This paper concerns scheduling problems with the aging effect and additional resource allocation. A measurable result of the aging phenomenon is that the time required to perform a job increases whereas the additional resource allocation allows one to decrease it. As an example of a deteriorating system that can be described and optimized by the application of the models and algorithms considered, we choose the pickling process, where cleaning of metal items decreases the efficiency of the pickling (cleaning) bath (i.e., one containing an active substance), whereas heating it up can improve the efficiency. In particular, we focus on the optimization problems for such systems and model them as single-machine scheduling problems with job processing times dependent on the fatigue of a machine and on the allocation of additional resources. The objectives considered are the minimization of time criteria (the maximum completion time and the maximum lateness) under a given resource consumption as well as the minimization of the resource consumption under given time criteria. The computational complexity of the problems is determined and solution properties are proved. On the basis of these, we construct optimal polynomial time algorithms for some cases of the problems considered.  相似文献   
978.
The present article covers an influence of the impact of electromagnetic interferences on computer information systems whose purpose is to control transport supervision systems. The primary objective of transport supervision systems is to detect hazards to human life and health that occur in the process of transport: traveling of people and/or cargos. This process needs to be characterized by a high level of reliability and safety. The measure of the transport safety is the confidence that the elements of a transport process will remain intact during its realization with the exception of those changes that are the result of the natural processes of aging and wear. The railway environment is one of the most difficult environments concerning the provision of electromagnetic compatibility. Those electromagnetic interferences that are intended and not intended being generated in a rail area have an impact on the operation process of a transport supervision system.  相似文献   
979.
A new numerical Monte Carlo method based model of a hot cavity surface ionization ion source is presented in this paper. The model, intended to support the studies on ionization phenomena in a widely used class of ion sources, takes into account geometry of the ion source and extraction system, ionizer temperature and other features. The results of ion source efficiency calculations for various configurations of the extraction field are reviewed. The dominant role of the ionizer region near the extraction opening is described. Simulated dependences of ionization efficiency on the working parameters like ionizer length and temperature, ionization potential of the substance, and extraction voltage are discussed. A good agreement of the experimental data (e.g., influence of ionizer temperature, current-voltage curve) and the predictions of the model is found. It is also shown that the contribution to the ionization yield from impact of thermionic electrons accelerated by the extraction field may be significant, especially for the substances of small surface ionization coefficient. The simulation results are compared to the predictions of different theoretical models of the ion source--the obtained simulation data are in accordance both with a well-known Kirchner formula and the so called spherical ionizer model.  相似文献   
980.
The paper describes the influence of the oxidation of natural organic matter (NOM) molecules with chlorine dioxide (ClO2) on granulated activated carbon (GAC) adsorption. In order to determinate the influence of ClO2 dosage on the NOM adsorption on GAC two parallel pilot scale experiments were performed. The raw water was treated respectively with 0.2 and 0.4 mg ClO2 L(-1) followed by the adsorption on GAC filters. Experiments were total organic carbon (TOC) measurements and size exclusion chromatography (SEC) controlled. The molecular weight distribution of NOM in the filtration bed outlet demonstrates that the low molecular weight molecules are less retained than the higher molecular weight components of NOM. It is shown that low molecular weight NOM causes less ClO2 demand. The oxidation of NOM molecules and very high capacity of GAC filter bed for NOM components can be used to control high ClO2 demand.  相似文献   
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