Laser melting treatment by overlapping passes of preheated nickel electrodeposited coatings on Al−Si alloy

Microstructure improvements of a nickel electrodeposited Al−Si alloy were studied after high-power laser melting treatment through a single pass or partially overlapping successive adjacent passes. In some cases, laser melting treatment was preceded by a 5-hour heating of the specimens at 500°C in argon atmosphere furnace. Microstructure observations and microhardness measurements were carried out on the specimens before and after laser melting treatment with and without preheating. Best results concerning microhardness, microstructural homogeneity, and porosity elimination, as well as adhesion of the nickel coating on the Al−Si alloy, were achieved when the specimens were first subjected to heating at 500°C in an argon atmosphere furnace for 5 hours and then submitted to a laser melting treatment through successive adjacent laser passes with an overlapping rate of 70 pct. Microstructure studies were carried out employing X-ray diffraction analysis (XRD) and energy-dispersive spectrometry (EDS). AlNi and Al₃Ni phases were detected in the diffusion area which resulted from the 5-hour heating. AlNi, Al₃Ni, and Al₃Ni₂ phases were identified in the laser melted zones (LMZs). Each one of the above phase was found to be the main phase under different conditions.     

An Adversarial Neuro-Tensorial Approach for Learning Disentangled Representations

International Journal of Computer Vision - Several factors contribute to the appearance of an object in a visual scene, including pose, illumination, and deformation, among others. Each factor...     

Exemplar queries: a new way of searching

Modern search engines employ advanced techniques that go beyond the structures that strictly satisfy the query conditions in an effort to better capture the user intentions. In this work, we introduce a novel query paradigm that considers a user query as an example of the data in which the user is interested. We call these queries exemplar queries. We provide a formal specification of their semantics and show that they are fundamentally different from notions like queries by example, approximate queries and related queries. We provide an implementation of these semantics for knowledge graphs and present an exact solution with a number of optimizations that improve performance without compromising the result quality. We study two different congruence relations, isomorphism and strong simulation, for identifying the answers to an exemplar query. We also provide an approximate solution that prunes the search space and achieves considerably better time performance with minimal or no impact on effectiveness. The effectiveness and efficiency of these solutions with synthetic and real datasets are experimentally evaluated, and the importance of exemplar queries in practice is illustrated.     

A case study on propagating and updating provenance information using the CIDOC CRM

Provenance information of digital objects maintained by digital libraries and archives is crucial for authenticity assessment, reproducibility and accountability. Such information is commonly stored on metadata placed in various Metadata Repositories (MRs) or Knowledge Bases (KBs). Nevertheless, in various settings it is prohibitive to store the provenance of each digital object due to the high storage space requirements that are needed for having complete provenance. In this paper, we introduce provenance-based inference rules as a means to complete the provenance information, to reduce the amount of provenance information that has to be stored, and to ease quality control (e.g., corrections). Roughly, we show how provenance information can be propagated by identifying a number of basic inference rules over a core conceptual model for representing provenance. The propagation of provenance concerns fundamental modelling concepts such as actors, activities, events, devices and information objects, and their associations. However, since a MR/KB is not static but changes over time due to several factors, the question that arises is how we can satisfy update requests while still supporting the aforementioned inference rules. Towards this end, we elaborate on the specification of the required add/delete operations, consider two different semantics for deletion of information, and provide the corresponding update algorithms. Finally, we report extensive comparative results for different repository policies regarding the derivation of new knowledge, in datasets containing up to one million RDF triples. The results allow us to understand the tradeoffs related to the use of inference rules on storage space and performance of queries and updates.     

Scalable entity-based summarization of web search results using MapReduce

Although Web Search Engines index and provide access to huge amounts of documents, user queries typically return only a linear list of hits. While this is often satisfactory for focalized search, it does not provide an exploration or deeper analysis of the results. One way to achieve advanced exploration facilities exploiting the availability of structured (and semantic) data in Web search, is to enrich it with entity mining over the full contents of the search results. Such services provide the users with an initial overview of the information space, allowing them to gradually restrict it until locating the desired hits, even if they are low ranked. This is especially important in areas of professional search such as medical search, patent search, etc. In this paper we consider a general scenario of providing such services as meta-services (that is, layered over systems that support keywords search) without a-priori indexing of the underlying document collection(s). To make such services feasible for large amounts of data we use the MapReduce distributed computation model on a Cloud infrastructure (Amazon EC2). Specifically, we show how the required computational tasks can be factorized and expressed as MapReduce functions. A key contribution of our work is a thorough evaluation of platform configuration and tuning, an aspect that is often disregarded and inadequately addressed in prior work, but crucial for the efficient utilization of resources. Finally we report experimental results about the achieved speedup in various settings.     

Electrochemical study of aluminium ion reduction in acidic AlCl3-n-butyl-pyridinium chloride melts

Electrochemical reduction of AlCl₃ dissolved in acidic AlCl₃-n-butyl-pyridinium chloride melt was studied by linear sweep voltammetry and chronopotentiometry at tungsten and platinum electrodes, in the Al₂Cl ₇ ^? concentration range 0.3 to 0.5 M between 30 and 60°C. Al₂Cl ₇ ^? bulk reduction was preceded by a nucleation (tungsten) or alloy formation phenomenon (platinum). The overall results agree rather well with the mechanism: $$\begin{gathered} 2AlCl_4^ - \rightleftarrows Al_2 Cl_7^ - + Cl^ - \hfill \\ 4Al_2 Cl_7^ - + 3e \rightleftarrows Al + 7AlCl_4^ - \hfill \\ \end{gathered} $$ The electrochemical reaction appeared quasi-reversible. Calculated values of the product of the transfer coefficient by the number of the electron exchanged in the rate determining step were in the range 0.45 to 0.7. Diffusion coefficients for Al₂Cl ₇ ^? were calculated.     

A Robot Application for Marine Vessel Inspection

Seagoing vessels have to undergo regular inspections, which are currently performed manually by ship surveyors. The main cost factor in a ship inspection is to provide access to the different areas of the ship, since the surveyor has to be close to the inspected parts, usually within arm's reach, either to perform a visual analysis or to take thickness measurements. The access to the structural elements in cargo holds, e.g., bulkheads, is normally provided by staging or by “cherry‐picking” cranes. To make ship inspections safer and more cost‐efficient, we have introduced new inspection methods, tools, and systems, which have been evaluated in field trials, particularly focusing on cargo holds. More precisely, two magnetic climbing robots and a micro‐aerial vehicle, which are able to assist the surveyor during the inspection, are introduced. Since localization of inspection data is mandatory for the surveyor, we also introduce an external localization system that has been verified in field trials, using a climbing inspection robot. Furthermore, the inspection data collected by the robotic systems are organized and handled by a spatial content management system that enables us to compare the inspection data of one survey with those from another, as well as to document the ship inspection when the robot team is used. Image‐based defect detection is addressed by proposing an integrated solution for detecting corrosion and cracks. The systems' performance is reported, as well as conclusions on their usability, all in accordance with the output of field trials performed onboard two different vessels under real inspection conditions.     

Particle swarm optimization with expanding neighborhood topology for the permutation flowshop scheduling problem

This paper introduces a new algorithmic nature-inspired approach that uses particle swarm optimization (PSO) with different neighborhood topologies, for successfully solving one of the most computationally complex problems, the permutation flowshop scheduling problem (PFSP). The PFSP belongs to the class of combinatorial optimization problems characterized as NP-hard and, thus, heuristic and metaheuristic techniques have been used in order to find high quality solutions in reasonable computational time. The proposed algorithm for the solution of the PFSP, the PSO with expanding neighborhood topology, combines a PSO algorithm, the variable neighborhood search strategy and a path relinking strategy. As, in general, the structure of the social network affects strongly a PSO algorithm, the proposed method using an expanding neighborhood topology manages to increase the performance of the algorithm. As the algorithm starts from a small size neighborhood and by increasing (expanding) in each iteration the size of the neighborhood, it ends to a neighborhood that includes all the swarm, and it manages to take advantage of the exploration abilities of a global neighborhood structure and of the exploitation abilities of a local neighborhood structure. In order to test the effectiveness and the efficiency of the proposed method, we use a set of benchmark instances of different sizes and compare the proposed method with a number of other PSO algorithms and other algorithms from the literature.     

A TQM-Based Approach to QoS Management

Total Quality Management (TQM) is one of the most interesting and effective concepts of management. Although, as of today, it has been extensively applied to manufacturing and industrial sectors, TQM principles have not received wide acceptance in the area of Telecommunications Network and Service Management. Application of those principles in Telecommunications can be facilitated by employing pertinent techniques and tools. This paper focuses on aspects of the performance management of Telecommunications Networks and Services. As basic quality control mechanisms, two versions of a Dynamic Scaling Service (DSS) are used to regulate the end-user perceived quality: a Crisp DSS and a Fuzzy Logic DSS. A quality-oriented user behavior model is built and a comparative study between the different quality control schemes is presented. Concluding, the paper delineates the scope of TQM with respect to QoS management in telecommunications.     

Digital library information-technology infrastructures

This paper charts a research agenda on systems-oriented issues in digital libraries. It focuses on the most central and generic system issues, including system architecture, user-level functionality, and the overall operational environment. With respect to user-level functionality, in particular, it abstracts the overall information lifecycle in digital libraries to five major stages and identifies key research problems that require solution in each stage. Finally, it recommends an explicit set of activities that would help achieve the research goals outlined and identifies several dimensions along which progress of the digital library field can be evaluated.