Numerical and experimental study of steady and unsteady mixed convection flow in a cubical open cavity with the bottom wall heated

En aquest estudi s'analitzen els experiments i simulacions numèriques del flux de convecció mixta en una cavitat cúbica situada a la part inferior d'un canal quadrat. Els nombres de Reynolds en funció de la velocitat mitjana del flux i l'amplada del canal estan en el rang 100≤Re≤1500 i el nombre de Richardson varia entre 0.1≤Ri≤10. La tècnica PIV s'ha utilitzat per a les mesures en un canal d'aigua. Simulacions numèriques Tridimensionals s’han dut a terme amb un codi de volums finits de segon ordre considerant l'aproximació de Boussinesq ja que, per les condicions experimentals utilitzades, la variació de les propietats físiques amb la temperatura no té influència significativa en la topologia general de flux. Per 100≤Re≤1500 i Ri≤0.1 el flux és estacionari i consisteix en un remolí situat a l’interior de la cavitat cúbica que mostra velocitats majors a mesura que augmenta el nombre de Richardson. El flux és no estacionari a Re = 100 i Ri = 10. Prop de les parets laterals es produeixen, de forma alternada, ejeccions de flux, des de l’interior de la cavitat cap al canal, mentre que el flux entra a la cavitat des del canal a través de la part central de la cavitat. S'ha utilitzat una tècnica de mostreig condicional per elucidar l’estructura mitjana de l'evolució del flux turbulent a Ri = 10. S'ha trobat que les ejeccions de flux persisteixen durant tot el rang de Reynolds analitzat. Els números de Nusselt calculats estan d'acord amb els de les correlacions reportades a la literatura, vàlides per cavitats bidimensionalsEn este estudio se analizan los experimentos y simulaciones numéricas del flujo de convección mixta en una cavidad cúbica situada en la parte inferior de un canal de sección cuadrada cuadrado. Los números de Reynolds en función de la velocidad media del flujo y la anchura del canal están en el rango 100≤Re≤1500 y el número de Richardson varía entre 0.1≤Ri≤10. La técnica PIV se ha utilizado para las medidas en un canal de agua. Se han llevado a cabo simulaciones numéricas tridimensionales con un código de volúmenes finitos de segundo orden, considerando la aproximación de Boussinesq ya que, en las condiciones experimentales utilizadas, la variación de las propiedades físicas con la temperatura no tiene influencia significativa en la topología general de flujo. En los rangos 100≤Re≤1500 y Ri≤0.1 el flujo es estacionario y consiste en un remolino situado en el interior de la cavidad cúbica que muestra velocidades mayores a medida que aumenta el número de Richardson. El flujo es no estacionario a Re = 100 y Ri = 10. Cerca de las paredes laterales se producen de forma alternada eyecciones de flujo, desde el interior de la cavidad hacia el canal, mientras que el flujo entra en la cavidad desde el canal a través de la parte central de la cavidad. Se ha utilizado una técnica de muestreo condicional para elucidar la estructura media de la evolución del flujo turbulento a Ri = 10. Se ha encontrado que las eyecciones de flujo persisten durante todo el rango de Reynolds analizado. Los números de Nusselt calculados están de acuerdo con los de las correlaciones reportadas en la literatura, válidas para cavidades bidimensionales.In this study we analyze experiments and numerical simulations of steady and unsteady mixed convection flow in a cubical cavity located at the bottom of a square channel. The Reynolds numbers based on the mean flow velocity and the channel width are in the range 100≤Re≤1500 and the Richardson numbers vary within 0≤Ri≤10. Particle Image Velocimetry has been used for the measurements in a water channel. Three-dimensional direct numerical simulations have been carried out with a second order finite volume code considering the Boussinesq approximation since, for the experimental conditions considered, the variation of the physical properties with temperature has no significant influence on the overall flow topology. For 100≤Re≤1500 and Ri≤0.1 the flow is steady and it consists in a single roll that exhibits larger velocities as the Richardson number is increased. An unsteady periodic flow is found at Re=100 and Ri=10. Alternate flow ejections from the cavity to the channel occur near the lateral walls while the flow enters the cavity from the channel through the central part of the cavity. A conditional sampling technique has been used to elucidate the evolution of the mean unsteady turbulent flow at Ri=10. It has been found that the alternate flow ejections persist for all the Reynolds analyzed. The computed Nusselt numbers are in general agreement with a previously reported correlation, valid for two dimensional cavities of different aspects ratios

An Assessment of Failed Government Projects in Low Resource Countries: A Systematic Review

Government development projects are of colossal significance to the development of the citizenry and this is fundamental to national development. However, available published literature has revealed that, globally, the quantum of failures in government development projects is on the ascendancy in recent times, especially among low-resource countries. In sub-Saharan Africa, about 25% of government projects are not completed and over 19,000 abandoned government projects are found in some areas and a third of projects that were started in Ghana are never completed consuming almost 20% of gross domestic product. This study assesses failed government projects in low-resource countries. A systematic review using about 21 published articles was downloaded among forty-one others and filtered based on study title, contents, objectives, publication date, and ethical issues among others. The study found that among the reasons for these governments’ failed projects are poor planning, poor management, implementation defects, cost variation, difficult stakeholders’ behaviour, poor procurement processes, poor monitoring, bureaucracy, communication and many more. The study concluded that there are increases in the incidence of government-failed projects due to poor planning, poor management, poor selection of contractors and lack of specific funding of projects and these have negative implications for economic growth and development among low-resource countries. The study recommends that government should ascribe itself to some future realistic project goals, abide by project policy implementation directives, and ensure effective monitoring and efficient collaboration with stakeholders. Keywords: assessment, failed government projects, low-resource countries, systematic review DOI: 10.7176/PPAR/13-5-04 Publication date:July 31st 202

Hybrid biometric template protection:Resolving the agony of choice between bloom filters and homomorphic encryption

Abstract Bloom filters (BFs) and homomorphic encryption (HE) are prominent techniques used to design biometric template protection (BTP) schemes that aim to protect sensitive biometric information during storage and biometric comparison. However, the pros and cons of BF‐ and HE‐based BTPs are not well studied in literature. We investigate the strengths and weaknesses of these two approaches since both seem promising from a theoretical viewpoint. Our key insight is to extend our theoretical investigation to cover the practical case of iris recognition on the ground that iris (1) benefits from the alignment‐free property of BFs and (2) induces huge computational burdens when implemented in the HE‐encrypted domain. BF‐based BTPs can be implemented to be either fast with high recognition accuracy while missing the important privacy property of ‘unlinkability’, or to be fast with unlinkability‐property while missing the high accuracy. HE‐based BTPs, on the other hand, are highly secure, achieve good accuracy, and meet the unlinkability‐property, but they are much slower than BF‐based approaches. As a synthesis, we propose a hybrid BTP scheme that combines the good properties of BFs and HE, ensuring unlinkability and high recognition accuracy, while being about seven times faster than the traditional HE‐based approach

Improved Multiplication-Free Biometric Recognition under Encryption

Modern biometric recognition systems extract distinctive feature vectors of biometric samples using deep neural networks to measure the amount of (dis-)similarity between two biometric samples. Studies have shown that personal information (e.g., health condition, ethnicity, etc.) can be inferred, and biometric samples can be reconstructed from those feature vectors, making their protection an urgent necessity. State-of-the-art biometrics protection solutions are based on homomorphic encryption (HE) to perform recognition over encrypted feature vectors, hiding the features and their processing while releasing the outcome only. However, this comes at the cost of those solutions' efficiency due to the inefficiency of HE-based solutions with a large number of multiplications; for (dis-)similarity measures, this number is proportional to the vector's dimension.In this paper, we tackle the HE performance bottleneck by freeing the two common (dis-)similarity measures, the cosine similarity and the squared Euclidean distance, from multiplications. Assuming normalized feature vectors, our approach pre-computes and organizes those (dis-)similarity measures into lookup tables. This transforms their computation into simple table lookups and summations only. We integrate the table lookup with HE and introduce pseudo-random permutations to enable cheap plaintext slot selection, which significantly saves the recognition runtime and brings a positive impact on the recognition performance. We then assess their runtime efficiency under encryption and record runtimes between 16.74ms and 49.84ms for both the cleartext and encrypted decision modes over the three security levels, demonstrating their enhanced speed for a compact encrypted reference template reduced to one ciphertext

Raltegravir Is a Potent Inhibitor of XMRV, a Virus Implicated in Prostate Cancer and Chronic Fatigue Syndrome

Xenotropic murine leukemia-related retrovirus (XMRV) is a recently discovered retrovirus that has been linked to human prostate cancer and chronic fatigue syndrome (CFS). Both diseases affect a large fraction of the world population, with prostate cancer affecting one in six men, and CFS affecting an estimated 0.4 to 1% of the population.. We found that the retroviral integrase inhibitor, raltegravir, was potent and selective against XMRV at submicromolar concentrations, in MCF-7 and LNCaP cells, a breast cancer and prostate cancer cell line, respectively. Another integrase inhibitor, L-000870812, and two nucleoside reverse transcriptase inhibitors, zidovudine (ZDV), and tenofovir disoproxil fumarate (TDF) also inhibited XMRV replication. When combined, these drugs displayed mostly synergistic effects against this virus, suggesting that combination therapy may delay or prevent the selection of resistant viruses.If XMRV proves to be a causal factor in prostate cancer or CFS, these discoveries may allow for rational design of clinical trials

A Bayesian inverse dynamic approach for impulsive wave loading reconstruction: Theory, laboratory and field application

The measurement of wave forces acting on marine structures is a complicated task, both during physical experiments and, even more so, in the field. Force transducers adopted in laboratory experiments require a minimum level of structural movement, thus violating the main assumption of fully rigid structure and introducing a dynamic response of the system. Sometimes the induced vibrations are so intense that they completely nullify the reliability of the experiments. On-site, it is even more complex, since there are no force transducers of the size and capacity able to measure such massive force intensity acting over the very large domain of a marine structure. To this end, this investigation proposes a Bayesian methodology aimed to remove the undesired effects from the directly (laboratory applications) or indirectly (field applications) measured wave forces. The paper presents three applications of the method: i) a theoretical application on a synthetic signal for which MATLAB® procedures are provided, ii) an experimental application on laboratory data collected during experiments aimed to model broken wave loading on a cylinder upon a shoal and iii) a field application designed to reconstruct the wave force that generated recorded vibrations on the Wolf Rock lighthouse during Hurricane Ophelia. The proposed methodology allows the inclusion of existing information on breaking and broken wave forces through the process-based informative prior distributions, while it also provides the formal framework for uncertainty quantification of the results through the posterior distribution. Notable findings are that the broken wave loading shows similar features for both laboratory and field data. The load time series is characterised by an initial impulsive component constituted by two peaks and followed by a delayed smoother one. The first two peaks are due to the initial impact of the aerated front and to the sudden deceleration of the falling water mass previously upward accelerated by the initial impact. The third, less intense peak, is due to the interaction between the cylinder and remaining water mass carried by the individual wave. Finally, the method allows to properly identify the length of the impulsive loading component. The implications of this length on the use of the impulse theory for the assessment or design of marine structures are discussed

Biometric Verification Secure Against Malicious Adversaries

Biometric verification has been widely deployed in current authentication solutions as it proves the physical presence of individuals. To protect the sensitive biometric data in such systems, several solutions have been developed that provide security against honest-but-curious (semi-honest) attackers. However, in practice attackers typically do not act honestly and multiple studies have shown drastic biometric information leakage in such honest-but-curious solutions when considering dishonest, malicious attackers. In this paper, we propose a provably secure biometric verification protocol to withstand malicious attackers and prevent biometric data from any sort of leakage. The proposed protocol is based on a homomorphically encrypted log likelihood-ratio-based (HELR) classifier that supports any biometric modality (e.g. face, fingerprint, dynamic signature, etc.) encoded as a fixed-length real-valued feature vector and performs an accurate and fast biometric recognition. Our protocol, that is secure against malicious adversaries, is designed from a protocol secure against semi-honest adversaries enhanced by zero-knowledge proofs. We evaluate both protocols for various security levels and record a sub-second speed (between $0.37$s and $0.88$s) for the protocol against semi-honest adversaries and between $0.95$s and $2.50$s for the protocol secure against malicious adversaries.Comment: This is a complete reworking and major expansion of our paper arXiv:1705.09936 * Reworking of original semi-honest protocol and its security proof * Major expansions: tailored zero-knowledge proofs; efficient variant of original protocol that we prove secure against malicious adversaries; extensive experimental evaluation using three different datasets; in-depth comparison with related wor

Nutritional evaluation of triathletes

O “triathlon”, nas suas diferentes dimensões, constitui-se inigualável modelo de prova de alta » intensidade e longa duração, notadamentc o “Ironman” Competições desta modalidade têm ganhado enorme repercussão nos veículos de comunicação e se tornado cada vez mais competitivas, com a profissionalização do esporte. A busca por melhores resultados passa pelos aspectos ligados à nutrição dos atletas. Sabidamente diversas “manobras” nutricionais são capazes de interferir na “performance” de atletas, assim como, a inadequação da sua dieta pode prejudicar o rendimento esportivo. Sabendo-se que o “triathlon” constitui-se modelo interessante para a avaliação dos efeitos de uma dieta adequada sobre a “performance”, propusemonos a realizar uma avaliação nutricional com 31 atletas paulistas, do sexo masculino, profissionais e amadores da modalidade, no que diz respeito a adequação da sua dieta ao gasto e necessidade energética diária, percentual de gordura corporal, assim como, seus conhecimentos básicos sobre o assunto, para podermos, posteriormente, propor formas de intervenção. Os resultados obtidos com atletas profissionais e amadores mostraram um gasto calórico diário de 2.450 e 1.870 kcal e uma necessidade energética diária de 4.250 e 3.730 kcal, respectivamente, valores superiores ao consumo energético encontrado de 3.800 e 3.000 kcal para profissionais c amadores. Notou-sc uma ingestão elevada de lípides que poderia ser reduzida em beneficio de um aporte maior de carboidratos, substrato mais importante para estes atletas. O perfil inadequado da ingestão de macronutrientcs pode ser devido ao elevado grau de desconhecimento dos atletas sobre o assunto. Desta forma, parece-nos que a adoção de questionários sobre conhecimentos básicos de nutrição para atletas faz-se necessário para o sucesso da implementação de alterações em suas dietas, assim como, ficou claro que os atletas da nossa amostragem poderiam aumentar a ingestão percentual de carboidratos em detrimento da de lípides, notadamentc os amadoresTriathlon is a good model for high intensity and prolonged exercise, in which the energy expenditure is pronounced. Very little is known, however, about the profile of Brazilian triathletes, as well as about their nutrition pattern. In this study we have evaluated the antropometric profile of Brazilian amateurs and professional triathletes, their nutrional pattern and their basic knowledge on nutrition. The results obtained showed that these athletes have a daily energy need of about 3730 kcal and 4250 kcal for amateurs and professionals, respectively. The dietary pattern assessment, however, showed that all of them presented a relatively high intake of fat, which could be substituted by an increased carbohydrate intake. All the athletes demonstrated a poor knowledge of basic nutrition, reflected in their dietary habit

Visualization of positive and negative sense viral RNA for probing the mechanism of direct-acting antivirals against hepatitis C virus

RNA viruses are highly successful pathogens and are the causative agents for many important diseases. To fully understand the replication of these viruses it is necessary to address the roles of both positive-strand RNA ((+)RNA) and negative-strand RNA ((-)RNA), and their interplay with viral and host proteins. Here we used branched DNA (bDNA) fluorescence in situ hybridization (FISH) to stain both the abundant (+)RNA and the far less abundant (-)RNA in both hepatitis C virus (HCV)- and Zika virus-infected cells, and combined these analyses with visualization of viral proteins through confocal imaging. We were able to phenotypically examine HCV-infected cells in the presence of uninfected cells and revealed the effect of direct-acting antivirals on HCV (+)RNA, (-)RNA, and protein, within hours of commencing treatment. Herein, we demonstrate that bDNA FISH is a powerful tool for the study of RNA viruses that can provide insights into drug efficacy and mechanism of action