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Modeling and analysis of slow CW decrease IEEE 802.11 WLAN
The IEEE 802.11 medium access control (MAC) protocol provides a contention-based distributed channel access mechanism for mobile stations to share the wireless medium, which may introduce a lot of collisions in case of overloaded active stations. Slow contention window (CW) decrease scheme is a simple and efficient solution for this problem. In this paper, we use an analytical model to compare the slow CW decrease scheme to the IEEE 802.11 MAC protocol. Several parameters are investigated such as the number of stations, the initial CW size, the decrease factor value, the maximum backoff stage and the coexistence with the RequestToSend and ClearToSend (RTS/CTS) mechanism. The results show that the slow CW decrease scheme can efficiently improve the throughput of IEEE 802.11, and that the throughput gain is higher when the decrease factor is larger. Moreover, the initial CW size and maximum backoff stage also affect the performance of slow CW decrease scheme
Dynamics of receptor-mediated nanoparticle internalization into endothelial cells.
International audienceNanoparticles offer a promising medical tool for targeted drug delivery, for example to treat inflamed endothelial cells during the development of atherosclerosis. To inform the design of such therapeutic strategies, we develop a computational model of nanoparticle internalization into endothelial cells, where internalization is driven by receptor-ligand binding and limited by the deformation of the cell membrane and cytoplasm. We specifically consider the case of nanoparticles targeted against ICAM-1 receptors, of relevance for treating atherosclerosis. The model computes the kinetics of the internalization process, the dynamics of binding, and the distribution of stresses exerted between the nanoparticle and the cell membrane. The model predicts the existence of an optimal nanoparticle size for fastest internalization, consistent with experimental observations, as well as the role of bond characteristics, local cell mechanical properties, and external forces in the nanoparticle internalization process
EvaluaciĂłn del rendimiento de los mĂ©todos de iteraciĂłn de listas en Java: un estudio empĂrico
Introduction: Lists are used in various software applications including web applications, desktop applications, and Internet ofThings (IoT) applications to store different types of items (e.g.country name, product model, and device category). Users can select one or more of these items to perform specific tasks such asfilling forms, ordering products, reading device data, etc. In somesoftware applications, lists store a huge number of items to be iterated over in order to know what users have selected. From a software development perspective, there are a number of methods toiterate over list items. Materials and Methods: In this paper, fivelist iteration methods: Classic For, Enhanced For, Iterator, List Iterator, and For Each have been compared experimentally with eachother with regard to their performance (execution time required toiterate over list items). Thus, a number of experimental test scenarios have been conducted to obtain the comparison results. Resultsand Discussion: The experimental results of this study have beenpresented in Table 4. Conclusions: Overall performance evaluation showed that Iterator and List Iterator methods outperformedother list iteration methods in all test scenarios. However, List Iterator outperformed Iterator when the list size was small. On theother hand, Iterator outperformed List Iterator when the list sizewas large
Information Technology Governance Control Level in Jordanian Banks Using: Control Objectives for Information and Related Technology (COBIT 5)
Information technology is considered a sensitive part for most strategies in the global market competition. There are plenty of factors indicating expansion in the world of information technology, the matter that places greater demands on the control of the environment for information technology and augments the need to mitigate risk and cost control related to the IT environment information. Hence, the importance of emphasizing the horizons of information, and the existence of effective controls on the IT environment should be designed for information technology services used by several parties, managers, auditors and owners. This should facilitate controls and offer the opportunity to re - engineer the applications of the existing regulatory environment, which requires a comprehensive review and redesign of the regulatory controls. To respond to any changes in the business environment, executives must ensure that information technology works with the greatest possible efficiency to help achieve goals and objectives. Growing competitive advantage, ensuring compliance and continuity, security and privacy are essential in order to achieve effective management for Information Technology related risks as well as maximal benefits in technology investment. Keywords: Business goal, Enterprise Governance of IT, IT governance, Organizational structure, Risk management
A Comparative Earthquakes Risk Assessment Approach Applied to the United Arab Emirates
This paper presents the preliminary results of a long research project on the assessment and mitigation of seismic risk in major cities in the UAE. UAE’s earthquake activity has long been recognized as one of the lowest in the world. All cities have experienced moderate earthquakes in the past, and will again do in the future. Recent earthquakes in Iran (e.g., Bam in 2003, --- in 2005) have killed thousands of people. Because of the different design and construction practices, different population density concentrations and economic activities in the UAE, different damages and losses are likely to be experienced. The impact of an earthquake is not limited to direct losses, such as the loss of life, loss of structures and business interruptions. Earthquakes also cause indirect losses by producing supply shortages and demand reductions in various economic sectors. In a country such as the UAE, which is undergoing an unprecedented constructionbased development with high-rise buildings being the main feature, a large earthquake in a major city can actually cause a considerable economic loss. In this study, a framework for assessing and comparing the risk associated with the adverse consequences of earthquakes in the UAE is presented. The framework is based on a simple risk-characterization model that is used to assess the health risks associated with toxic chemicals. The model: Risk = D × RF × Pop × ER, adopted to fit our purpose of estimating the risk associated with the consequences of earthquakes, the various parameters in the above mentioned model are translated as follows: Dose (D)= seismic “force” at a specific location or weighted for an area; Response Factor (RF) = degree of damage or losses per unit “force”; Population (Pop) = a factor representing exposed population. Equivalent populations may also include exposed environment or exposed infrastructure. Emergency Response (ER) = effectiveness of available emergency response programs to reduce risk immediately as the adverse effects take place. It should be noted that emergency response in this case is different than deliberate risk management. First, the earthquake hazard and risk in the UAE, including the estimation of the amplitudes of the ground motion parameters, is stochastically assessed. Then the comparative risk framework to assess the relative impacts on people and buildings in the seven emirates and the major cities of the UAE is applied. The result is a ranking system for risk that is being integrated within a geographic information system (GIS). The database is intended for detailed development to maximize benefits to the various stake holders in the community
Spectrum of One-Dimensional Anharmonic Oscillators
We use a power-series expansion to calculate the eigenvalues of anharmonic
oscillators bounded by two infinite walls. We show that for large finite values
of the separation of the walls, the calculated eigenvalues are of the same high
accuracy as the values recently obtained for the unbounded case by the
inner-product quantization method. We also apply our method to the Morse
potential. The eigenvalues obtained in this case are in excellent agreement
with the exact values for the unbounded Morse potential.Comment: 11 pages, 5 figures, 4 tables; there are changes to match the version
published in Can. J. Phy
Any -state solutions of the Hulth\'en potential by the asymptotic iteration method
In this article, we present the analytical solution of the radial
Schr\"{o}dinger equation for the Hulth\'{e}n potential within the framework of
the asymptotic iteration method by using an approximation to the centrifugal
potential for any states. We obtain the energy eigenvalues and the
corresponding eigenfunctions for different screening parameters. The wave
functions are physical and energy eigenvalues are in good agreement with the
results obtained by other methods for different values. In order to
demonstrate this, the results of the asymptotic iteration method are compared
with the results of the supersymmetry, the numerical integration, the
variational and the shifted 1/N expansion methods.Comment: 14 pages and 1 figur
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