14,879 research outputs found

    MESURE Tool to benchmark Java Card platforms

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    The advent of the Java Card standard has been a major turning point in smart card technology. With the growing acceptance of this standard, understanding the performance behavior of these platforms is becoming crucial. To meet this need, we present in this paper a novel benchmarking framework to test and evaluate the performance of Java Card platforms. MESURE tool is the first framework which accuracy and effectiveness are independent from the particular Java Card platform tested and CAD used.Comment: International Journal of Computer Science Issues, Volume 1, pp49-57, August 200

    Sparse Automatic Differentiation for Large-Scale Computations Using Abstract Elementary Algebra

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    Most numerical solvers and libraries nowadays are implemented to use mathematical models created with language-specific built-in data types (e.g. real in Fortran or double in C) and their respective elementary algebra implementations. However, built-in elementary algebra typically has limited functionality and often restricts flexibility of mathematical models and analysis types that can be applied to those models. To overcome this limitation, a number of domain-specific languages with more feature-rich built-in data types have been proposed. In this paper, we argue that if numerical libraries and solvers are designed to use abstract elementary algebra rather than language-specific built-in algebra, modern mainstream languages can be as effective as any domain-specific language. We illustrate our ideas using the example of sparse Jacobian matrix computation. We implement an automatic differentiation method that takes advantage of sparse system structures and is straightforward to parallelize in MPI setting. Furthermore, we show that the computational cost scales linearly with the size of the system.Comment: Submitted to ACM Transactions on Mathematical Softwar

    Port-City Development: The Spanish Case

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    [Abstract]: The objective of this paper is to try to evaluate the port-city relationship from its onset, taking into account the challenges of port 4.0. Indicators such as the percentage of employees participating in training programs, the percentage of female employees in Galician ports, the percentage of merchandise moved by private operators and the percentage of companies with quality certification in Galician ports are evaluated. The fourth revolution is based on the transition from current fossil fuel-based energy models to alternative energy sources, changes in the logistics and transport parameters and finally, on the elimination of intermediation. The key component of the third pillar of new Economy 4.0 is complete digitalization. The optimum port-city solution must address the need of both the urban planner and the port manager to evaluate potential measures that would alleviate the pressure of dedicated port facilities on the city and vice versa to the greatest extent possible

    An evaluation of Nigerian ports post-concession performance

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    Purpose: The quest for efficiency is claimed to be the major objective of port privatisation and this has led many ports in Africa to undertake port reforms. Based on this, Nigerian ports were concessioned and operations were handed over in one scoop to private operators between 2006 and 2007. This paper is looking to investigate in the reform that took place in a very short period of time improved the performance of Nigerian ports. This paper is also looking to provide a model for future evaluation. Research Approach: A window based DEA model with panel data will be employed to measure pre- and post concession Nigerian ports' performance to determine efficiency gains from port reform. Secondly, to demonstrate how concession influence efficiency, a DEA based Malmquist productivity Insex will be used to determine the sources of (in)efficiency by decomposing the efficiency into frontier shift effects and catch-up effects. Findings and Originality: The results revealed that none of the ports is hundred percent efficient before and after concession but rather a tremendous increase in throughput and ship traffic after the reform in most of the ports. Apapa port is the most efficient while Calabar and Warri are inefficient although there were fluctuations in efficiency in all the ports. The research is inconclusive because it is still ongoing Although some studies have investigated the relationship between port efficiency and privatisation however several gaps still exist as the studies are skewed in favour of container ports in the developed world, mainly in Europe. Therefore, the need arises to critically look at the overall efficiency of national port system to enhance the efficiency of global transport chain. Research Impact: The study will contribute to existing literature on port performance being the first to evaluate the post concession performance of a major maritime player in Sub-Saharan Africa. It will contribute to the never- ending debate by the Academia on the effect of ownership or privatisation on efficiency from the perspective of port institutional reforms in the third world countries Practical Impact: It will benefit the Federal Government of Nigeria as a reference document of the first five years of the port reform policy and help the Government to intervene in areas of observed inefficiencies and make adjustments where possible. On the part of the "Landlord" NPA it will help them in the performing their regulatory role by identifying the operators who are making inefficient use of the resources allocated to them and provide the basis for future evaluation. Finally, it will give the various stake holders in the Maritime Industry a full grasp of the effect of concession in a Nation's port as Nigeria is the first country in the world to hand over terminal operations in all her ports in one scoop

    High-Level Object Oriented Genetic Programming in Logistic Warehouse Optimization

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    Disertační práce je zaměřena na optimalizaci průběhu pracovních operací v logistických skladech a distribučních centrech. Hlavním cílem je optimalizovat procesy plánování, rozvrhování a odbavování. Jelikož jde o problém patřící do třídy složitosti NP-težký, je výpočetně velmi náročné nalézt optimální řešení. Motivací pro řešení této práce je vyplnění pomyslné mezery mezi metodami zkoumanými na vědecké a akademické půdě a metodami používanými v produkčních komerčních prostředích. Jádro optimalizačního algoritmu je založeno na základě genetického programování řízeného bezkontextovou gramatikou. Hlavním přínosem této práce je a) navrhnout nový optimalizační algoritmus, který respektuje následující optimalizační podmínky: celkový čas zpracování, využití zdrojů, a zahlcení skladových uliček, které může nastat během zpracování úkolů, b) analyzovat historická data z provozu skladu a vyvinout sadu testovacích příkladů, které mohou sloužit jako referenční výsledky pro další výzkum, a dále c) pokusit se předčit stanovené referenční výsledky dosažené kvalifikovaným a trénovaným operačním manažerem jednoho z největších skladů ve střední Evropě.This work is focused on the work-flow optimization in logistic warehouses and distribution centers. The main aim is to optimize process planning, scheduling, and dispatching. The problem is quite accented in recent years. The problem is of NP hard class of problems and where is very computationally demanding to find an optimal solution. The main motivation for solving this problem is to fill the gap between the new optimization methods developed by researchers in academic world and the methods used in business world. The core of the optimization algorithm is built on the genetic programming driven by the context-free grammar. The main contribution of the thesis is a) to propose a new optimization algorithm which respects the makespan, the utilization, and the congestions of aisles which may occur, b) to analyze historical operational data from warehouse and to develop the set of benchmarks which could serve as the reference baseline results for further research, and c) to try outperform the baseline results set by the skilled and trained operational manager of the one of the biggest warehouses in the middle Europe.

    The Impacts of Airport Centrality in the EU Network and Inter- Airport Competition on Airport Efficiency

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    In this paper we study the relationship between airport efficiency and two factors: an airport’s centrality in the EU network, and the intensity of competition from alternative airports in the same catchment area. We apply a two-stage econometric model based on the Simar & Wilson (2007) bootstrap procedure to a balanced sample of 57 European airports. We also design and compute our own measures of airport centrality and competition. The results show that efficiency is positively related to centrality in the European network, as measured by a weighted sum of minimal paths passing through the airport in question. The intensity of competition between airports also has a positive effect on efficiency. Our analysis suggests that air transportation policies should focus on increasing competition within important catchment areas (e.g., by investing in infrastructure facilitating access to alternative airports) and enhancing the connectivity of the EU network (e.g., by subsidizing new point-to-point connections between airports with capacity to spare).air transportation, efficiency, network centrality, inter – airports competition.
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