70 research outputs found
Experimental uncertainty of measured entropy production with pulsed laser PIV and planar laser induced fluorescence
No full textThe article develops an uncertainty analysis for a newly measured variable of local entropy production. Entropy production is measured with post-processing and spatial differencing of measured velocities from particle image velocimetry (PIV), as well as temperatures obtained from planar laser induced fluorescence (PLIF). Measurement uncertainties of fluid velocity depend on the time interval between laser pulses, width of the camera view and other factors. Bias errors are related to elementary bias components and sensitivity coefficients in the uncertainty analysis. The precision errors use a confidence coefficient of 2 for a 95% confidence interval. The newly developed measurement technique and uncertainty analysis are successfully applied to pressure-driven channel flow and buoyancy-driven free convection in a square enclosure.Natural Sciences and Engineering Research Council of CanadaUniversity of Manitoba Graduate FellowshipCFI (Canada Foundation for Innovation)WED (Western Economic Diversification
An Analysis of Collaborative Attacks on Mobile Ad hoc Networks
No full textA Mobile Ad hoc Network (MANET) consists of a set of communicating wireless mobile nodes or devices that do not have any form of fixed infrastructure or centralized authority. The security in MANET has become a significant and active topic within the research community. This is because of high demand in sharing streaming video and audio in various applications, one MANET could be setup quickly to facilitate communications in a hostile environment such as battlefield or emergency situation likes disaster rescue operation. In spite of the several attacks aimed at specific nodes in MANET that have been uncovered, some attacks involving multiple nodes still receive little attention. A reason behind this is because people make use of security mechanisms applicable to wired networks in MANET and overlook the security measures that apply to MANET. Furthermore, it may also have to do with the fact that no survey or taxonomy has been done to clarify the characteristics of different multiple node attacks. This thesis addresses the aforementioned gap by providing a proper definition and categorization of collaborative attacks against MANET from the various multiple node attacks found. Simulation using OPNET Modeler was used to investigate the performance impact of a collaborative blackhole attack on a mobile ad hoc network. Network throughput, packet delivery ratio and end-to-end delay are the performance metrics used in our result analysis. Based on the analyses of performance metrics made, we realised the consequences of a collaborative blackhole attack on MANET. In order to prevent or reduce these consequences, we also discuss a number of mitigation plans to counteract the different kinds of collaborative attacks. Keywords: MANET, Collaborative Attacks, Multiple Node, Blackhole.Contact Information: Author(s): Cong Hoan Vu Address: Folkparksvägen 19:08, 372 40 Ronneby, Sweden. E-mail: [email protected] Adeyinka Soneye Address: Polhemsgatan 27B, LGH 30, 371 40 Karlskrona, Sweden. E-mail: [email protected]
Optimization correlation for entropy production and energy availability in film condensation
No full textThis article investigates the physical significance of entropy production in plate film condensation. An irreversibility distribution ratio yields similar trends as previous studies, whereby the Prandtl number has suggested the relevant influence of inertial effects. Results for the optimized entropy production and plate size are expressed in terms of a duty parameter. It is observed that entropy production provides a useful parameter in the optimization of a two-phase system
Apparent entropy production difference with heat and fluid flow irreversibilities
No full textAn entropy-based procedure is presented to assess the solution accuracy in heat transfer problems with fluid flow using the second law of thermodynamics. The procedure is implemented by a control-volume-based finite-element formulation for discrete equations arising from the conservation laws and the second law. The study involves a comparison of the local entropy production rates computed from two forms of the discretized entropy equation. The computed local entropy production for two heat transfer problems, using the positive-definite and the transport forms of the entropy generation equation, agrees well with analytical solutions. It is demonstrated by the results of the numerical studies that there exists a relationship between a newly defined parameter, called the apparent error in entropy production, and the solution error in the computed value of the scalar in each control volume
Modeling of entropy production in turbulent flows
No full textThis article presents new modeling of turbulence correlations in the entropy transport equation for viscous, incompressible flows. An explicit entropy equation of state is developed for gases with the ideal gas law, while entropy transport equations are derived for both gases and liquids. The formulation specifically considers incompressible forced convection problems without a buoyancy term in the y-momentum equation, as density variations are neglected. Reynolds averaging techniques are applied to the turbulence closure of fluctuating temperature and entropy fields. The problem of rigorously expressing the mean entropy production in terms of other mean flow quantities is addressed. The validity of the newly developed formulation is assessed using direct numerical simulation data and empirical relations for the friction factor. Also, the dissipation (ε) of turbulent kinetic energy is formulated in terms of the Second Law. In contrast to the conventional ε equation modeling, this article proposes an alternative method by utilizing both transport and positive definite forms of the entropy production equation
Establishment of a Standing Ethics/institutional Review Board in a Nigerian University: A Blueprint for Developing Countries
No full textAn ethics/institutional review board(IRB) was established according to International standards at the University of Ibadan in Nigeria. To achieve this, a private-public partnership was developed to support a review of prevailing practice and the development of necessary infrastructure for an effective IRB. An internationally registered and well-constituted IRB with a federal-wide assurance (FWA) from the National Institute of Health in the United States was established within a year. Over a 3-year period, the number of proposals reviewed increased by 150% while time to approval decreased by 62%. International collaboration and external research funding has increased substantially. These findings support our initial supposition that the development of a properly functioning IRB can be a catalyst for increased research productivity at academic centers in developing countries while ensuring the protection of vulnerable human research subjects. The University of Ibadan is now assisting other academic Institutions in Nigeria and sub-Saharan Africa with the establishment of their own IRBs
African Europeans : an untold history
No full textThe history of Africans in Europe is unknown to many as it is a history that is not taught in most European schools. The book African Europeans: An Untold History educates the reader on this crucial missing aspect by detailing the influences and activities of Blacks in Europe and how they contributed to what Europe is today. The book helps readers to understand how the historical construction of the Negro as a beast of burden, without heritage or culture, contributed to the eradication of Black history in Europe. The author, Olivette Otele, then counters this by setting out the history of the many Black people and Black groups that did ordinary and extraordinary things in Europe. In doing so, Otele deconstructs a dominant narrative in European history that suggests that only exceptional Black people contributed and did so rarely
Non-specific cell-mediated immunity in Nigerian children with uncomplicated malaria
No full textNon-specific cellular immunity was determined in 59 Nigerian children
aged between 1-9 years with uncomplicated malaria and 93 age-matched
uninfected controls using percentage migration index (%M.I) and Mantoux
tuberculin skin test. The mean %M.I (using malaria Pf 155 antigen) was
significantly lower in malaria subjects compared with the controls
(p<0.05) while the mean diameter of tuberculin skin reaction (using
Purified Protein Derivative of Mycobacterium butyricum ) was
significantly lower in children with uncomplicated malaria compared
with the controls (p<0.05). The mean total white blood cell count
(TWBC) was also significantly reduced in the malaria subjects when
compared with the controls (p<0.05). The results show that
leucocytes of children with uncomplicated malaria exhibited effective
adaptive immune response. This may help to combat initial contact with
malaria parasites
Undergraduate students' knowledge of copyright infringement
No full textThis study examined undergraduate students’ knowledge of copyright infringement at the University of Ilorin, Nigeria. A descriptive survey design was adopted. Three hundred and seventy-two (372) undergraduate students randomly selected from twelve universities constituted the sample for the study. Four research questions were developed and answered and data was collected through a self-designed questionnaire. The findings demonstrate that the majority of the respondents are aware of copyright infringement and have strong perception that copyright infringement is a form of intellectual dishonesty. In addition, the results indicate that downloading content from the internet without permission from the owner is the major way through which undergraduates mostly infringed on the copyright. The findings also show that high cost of textbook is a contributing factor that leads students to infringe on copyright law, followed by scarcity of materials, fear of scoring poor marks, lack of awareness and overarching curricula while the desire to defy authority had the least influence. The increasing awareness of copyright law and possible punishment for violating the law was rated as the most fundamental way of reducing copyright infringement. The only hypothesis tested in the study revealed a significant difference in the perception of undergraduate students on copyright infringement based on their academic level with (Chi Cal. = 740.85, df=16, chi table= 26.30 at 0.05 level of significant difference). Upon these findings, the study recommends that author and publishers should try to reduce the cost of their textbooks. In addition, libraries in higher institutions should be well equipped with enough and relevant printed/literary resources. These should be readily available and accessible to the students when needed, in order to help reducing the rate of piracy and photocopying in higher institutions
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