Analytical model for bar-end cover separation failure in RC beams strengthened with near-surface mounted FRP

The flexural performance of RC beams can be improved using the near-surface mounted (NSM) FRP strengthening technique. A likely failure mode of such FRP-strengthened RC beams is bar-end cover separation which involves the detachment of the NSM FRP reinforcement together with the concrete cover along the level of the steel tension reinforcement. This paper presents a new analytical strength model for this failure mode. The proposed strength model and two existing strength models for this failure mode are compared with test results to demonstrate the superior performance of the new analytical model.

On Infinite Time Performance of Nonlinear Model Predictive Controllers

This paper addresses the problem of infinite time performance of model predictive controllers applied to constrained nonlinear systems. The total performance is compared with a finite horizon optimal cost to reveal performance limits of closed-loop model predictive control systems. Based on the Principle of Optimality, an upper and a lower bound of the ratio between the total performance and the finite horizon optimal cost are obtained explicitly expressed by the optimization horizon. The results also illustrate, from viewpoint of performance, how model predictive controllers approaches to infinite optimal controllers as the optimization horizon increases.

Finite-element investigation of cold-formed steel portal frames in fire

This paper presents the results of a full-scale site fire test performed on a cold-formed steel portal frame building with semi-rigid joints. The purpose of the study is to establish a performance-based approach for the design of such structures in fire boundary conditions. In the full-scale site fire test, the building collapsed asymmetrically at a temperature of 714°C. A non-linear elasto-plastic finite-element shell model is described and is validated against the results of the full-scale test. A parametric study is presented that highlights the importance of in-plane restraint from the side rails in preventing an outwards sway failure for both a single portal and full building geometry model. The study also demonstrates that the semi-rigidity of the joints should be taken into account in the design. The single portal and full building geometry models display a close match to site test results with failure at 682°C and 704°C, respectively. A design case is described in accordance with Steel Construction Institute design recommendations. The validated single portal model is tested with pinned bases, columns protected, realistic loading and rafters subject to symmetric uniform heating in accordance with the ISO 834 standard fire curve; failure occurs at 703°C.

Time-lapse monitoring of fluid induced geophysical property variations within an unstable earthwork using P-wave refraction

A significant portion of the UK’s transportation system relies on a network of geotechnical earthworks (cuttings and embankments) that were constructed more than 100 years ago, whose stability is affected by the change in precipitation patterns experienced over the past few decades. The vulnerability of these structures requires a reliable, cost- and time-effective monitoring of their geomechanical condition. We have assessed the potential application of P-wave refraction for tracking the seasonal variations of seismic properties within an aged clay-filled railway embankment, located in southwest England. Seismic data were acquired repeatedly along the crest of the earthwork at regular time intervals, for a total period of 16 months. P-wave first-break times were picked from all available recorded traces, to obtain a set of hodocrones referenced to the same spatial locations, for various dates along the surveyed period of time. Traveltimes extracted from each acquisition were then compared to track the pattern of their temporal variability. The relevance of such variations over time was compared with the data experimental uncertainty. The multiple set of hodocrones was subsequently inverted using a tomographic approach, to retrieve a time-lapse model of VPVP for the embankment structure. To directly compare the reconstructed VPVP sections, identical initial models and spatial regularization were used for the inversion of all available data sets. A consistent temporal trend for P-wave traveltimes, and consequently for the reconstructed VPVP models, was identified. This pattern could be related to the seasonal distribution of precipitation and soil-water content measured on site.

Finite element modelling of cyclic behaviour of cold-formed steel bolted moment-resisting connections

This paper investigates the accuracy of new finite element modelling approaches to predict the behaviour of bolted moment-connections between cold-formed steel members, formed by using brackets bolted to the webs of the section, under low cycle fatigue. ABAQUS software is used as a modelling platform. Such joints are used for portal frames and potentially have good seismic resisting capabilities, which is important for construction in developing countries. The modelling implications of a two-dimensional beam element model, a three-dimensional shell element model and a three-dimensional solid element model are reported. Quantitative and qualitative results indicate that the three-dimensional quadratic S8R shell element model most accurately predicts the hysteretic behaviour and energy dissipation capacity of the connection when compared to the test results.

Modelling of Evaporator in Waste Heat Recovery System using Finite Volume Method and Fuzzy Technique

The evaporator is an important component in the Organic Rankine Cycle (ORC)-based Waste Heat Recovery (WHR) system since the effective heat transfer of this device reflects on the efficiency of the system. When the WHR system operates under supercritical conditions, the heat transfer mechanism in the evaporator is unpredictable due to the change of thermo-physical properties of the fluid with temperature. Although the conventional finite volume model can successfully capture those changes in the evaporator of the WHR process, the computation time for this method is high. To reduce the computation time, this paper develops a new fuzzy based evaporator model and compares its performance with the finite volume method. The results show that the fuzzy technique can be applied to predict the output of the supercritical evaporator in the waste heat recovery system and can significantly reduce the required computation time. The proposed model, therefore, has the potential to be used in real time control applications.

Addiction to Runx1 is partially attenuated by loss of p53 in the Eµ-Myc lymphoma model

The Runx genes function as dominant oncogenes that collaborate potently with Myc or loss of p53 to induce lymphoma when over-expressed. Here we examined the requirement for basal Runx1 activity for tumor maintenance in the Eµ-Myc model of Burkitt's lymphoma. While normal Runx1fl/fl lymphoid cells permit mono-allelic deletion, primary Eµ-Myc lymphomas showed selection for retention of both alleles and attempts to enforce deletion in vivo led to compensatory expansion of p53null blasts retaining Runx1. Surprisingly, Runx1 could be excised completely from established Eµ-Myc lymphoma cell lines in vitro without obvious effects on cell phenotype. Established lines lacked functional p53, and were sensitive to death induced by introduction of a temperature-sensitive p53 (Val135) allele. Transcriptome analysis of Runx1-deleted cells revealed a gene signature associated with lymphoid proliferation, survival and differentiation, and included strong de-repression of recombination-activating (Rag) genes, an observation that was mirrored in a panel of human acute leukemias where RUNX1 and RAG1,2 mRNA expression were negatively correlated. Notably, despite their continued growth and tumorigenic potential, Runx1null lymphoma cells displayed impaired proliferation and markedly increased sensitivity to DNA damage and dexamethasone-induced apoptosis, validating Runx1 function as a potential therapeutic target in Myc-driven lymphomas regardless of their p53 status.

Spatio-temporal Rich Model Based Video Steganalysis on Cross Sections of Motion Vector Planes

A rich model based motion vector steganalysis benefiting from both temporal and spatial correlations of motion vectors is proposed in this work. The proposed steganalysis method has a substantially superior detection accuracy than the previous methods, even the targeted ones. The improvement in detection accuracy lies in several novel approaches introduced in this work. Firstly, it is shown that there is a strong correlation, not only spatially but also temporally, among neighbouring motion vectors for longer distances. Therefore, temporal motion vector dependency along side the spatial dependency is utilized for rigorous motion vector steganalysis. Secondly, unlike the filters previously used, which were heuristically designed against a specific motion vector steganography, a diverse set of many filters which can capture aberrations introduced by various motion vector steganography methods is used. The variety and also the number of the filter kernels are substantially more than that of used in previous ones. Besides that, filters up to fifth order are employed whereas the previous methods use at most second order filters. As a result of these, the proposed system captures various decorrelations in a wide spatio-temporal range and provides a better cover model. The proposed method is tested against the most prominent motion vector steganalysis and steganography methods. To the best knowledge of the authors, the experiments section has the most comprehensive tests in motion vector steganalysis field including five stego and seven steganalysis methods. Test results show that the proposed method yields around 20% detection accuracy increase in low payloads and 5% in higher payloads.

On lattices from combinatorial game theory modularity and a representation theorem: Finite case

We show that a self-generated set of combinatorial games, S, may not be hereditarily closed but, strong self-generation and hereditary closure are equivalent in the universe of short games. In [13], the question “Is there a set which will give an on-distributive but modular lattice?” appears. A useful necessary condition for the existence of a finite non-distributive modular L(S) is proved. We show the existence of S such that L(S) is modular and not distributive, exhibiting the first known example. More, we prove a Representation Theorem with Games that allows the generation of all finite lattices in game context. Finally, a computational tool for drawing lattices of games is presented.

Measurements of thermophysical properties of perfluorocarbons and ionic liquids

No presente trabalho propõe-se estudar a tensão superficial de vários perfluorocarbonetos lineares, cíclicos, aromáticos e [alfa]-substituídos bem como líquidos iónicos com o catião imidazolium em comum. Apesar do seu interesse inerente, informação sobre esta propriedade para os compostos seleccionados é escassa e quando disponível apresenta discrepâncias consideráveis entre si. As medições foram realizadas no intervalo de temperaturas (283 to 353) K usando o método do anel de Du Noüy. Para os fluorocarbonetos, os dados experimentais demonstram que a estrutura molecular é o factor primordial no comportamento da superfície uma vez que os fluorocarbonetos aromáticos apresentam a tensão superficial mais elevada, seguida pelos fluorocarbonetos cíclicos e substituídos. Os perfluorocarbonetos lineares apresentam os menores valores de tensão superficial, aumentando ligeiramente com o aumento do número de carbonos. Os líquidos iónicos estudados foram seleccionados com o objectivo de fornecerem um estudo compreensivo sobre a influência do tamanho da cadeia alquílica do catião, o número de substituições no catião e a influência do anião. A influência do conteúdo de água na tensão superficial foi estudada em função da temperatura e da fracção molar de água para o liquido iónico mais hidrofóbico, [omim][PF6], e para o mais higroscópico, [bmim][PF6]. As funções termodinâmicas de superfície, como a entropia e entalpia de superfície, foram derivadas a partir da dependência da tensão superficial com a temperatura. Os dados obtidos para o fluorocarbonetos foram comparados com a correlação proposta por Faizullin, apresentando um desvio inferior a 4 % e demonstrando a sua aplicabilidade para com esta classe de compostos. A metodologia adoptada neste trabalho requer o conhecimento das densidades dos compostos de modo a aplicar a necessária correcção hidrostática. Contudo, para os líquidos iónicos esta informação é limitada ou mesmo inexistente. Por este motivo realizaram-se medições de densidade em função da pressão (0.10 < p/MPa < 10.0) e da temperatura (293.15 < T/K < 393.15). Desta dependência, as propriedades termodinâmicas, tais como compressibilidade isotérmica, expansividade isobárica, coeficiente térmico da pressão e dependência da capacidade calorífica com a pressão foram investigadas. A influência do teor de água na densidade foi também estudada para o líquido iónico mais hidrofóbico, [omim][PF6]. Um modelo simples de volume-ideal foi aplicado de forma preditiva para os volumes molares dos líquidos iónicos, em condições ambientais, descrevendo bem os dados experimentais. ABSTRACT: This work aims at studying the surface tension of some linear, cyclic, aromatic, [alfa]-substituted perfluorocarbons and imidazolium based ionic liquids. Despite its fundamental interest, information about this property for these compounds is scarce and the available data present strong discrepancies among each other. The measurements were carried out in the temperature range (283 to 353) K with the Du Noüy ring method. For the fluorocarbons, the analysis of the experimental data shows that the molecular structure is the main factor in the surface since the aromatic fluorocompounds present the highest surface tensions, followed by the cyclic and substituted fluorocompounds. The linear n-perfluoroalkanes exhibit the lowest surface tension values, slightly increasing with the carbon number. The set of selected ionic liquids was chosen to provide a comprehensive study of the influence of the cation alkyl chain length, the number of cation substitutions and the anion on the properties under study. The influence of water content in the surface tension was studied for several ILs as a function of the temperature as well as a function of water mole fraction, for the most hydrophobic IL investigated, [omim][PF6], and one hygroscopic IL, [bmim][PF6]. The surface thermodynamic functions such as surface entropy and enthalpy were derived from the temperature dependence of the surface tension values. The perfluorocarbons experimental data were compared against the Faizullin correlation, and it is shown that this correlation describes the measured surface tensions with deviations inferior to 4 %. The methodology adopted in this work requires the knowledge of the densities of the compounds under study in order to apply an hydrostatic correction. However, for ionic liquids these information is scarse and in some cases unavailable. Therefore, experimental measurements of the pressure (0.10 < p/MPa < 10.0) and temperature (293.15 < T/K < 393.15) dependence of the density and derived thermodynamic properties, such as the isothermal compressibility, the isobaric expansivity, the thermal pressure coefficient, and the pressure dependence of the heat capacity of several imidazolium-based ionic were determined. The influence of water content in the density was also studied for the most hydrophobic IL used, [omim][PF6]. A simple ideal-volume model was employed for the prediction of the imidazolium molar volumes at ambient conditions, which proved to agree well with the experimental results.

Cumulus momentum fluxes in cloud-resolving model simulations of toga-coare

O objectivo deste trabalho científico é o estudo do transporte vertical de momento linear horizontal (CMT) realizado por sistemas de nuvens de convecção profunda sobre o oceano tropical. Para realizar este estudo, foram utilizadas simulações tridimensionais produzidas por um modelo explícito de nuvens (CRM) para os quatro meses de duração da campanha observacional TOGA COARE que ocorreu sobre as águas quentes do Pacífico ocidental. O estudo foca essencialmente as características estatísticas e à escala da nuvem do CMT durante um episódio de fortes ventos de oeste e durante um período de tempo maior que incluí este evento de convecção profunda. As distribuições verticais e altitude-temporais de campos atmosféricos relacionados com o CMT são avaliadas relativamente aos campos observacionais disponíveis, mostrando um bom acordo com os resultados de estudos anteriores, confirmando assim a boa qualidade das primeiras e fornecendo a confiança necessária para continuar a investigação. A sensibilidade do CMT em relação do domínio espacial do model é analisada, utilizando dois tipos de simulações tridimensionais produzidas por domínios horizontais de diferente dimensão, sugerindo que o CMT não depende da dimensão do domínio espacial horizontal escolhido para simular esta variável. A capacidade da parameterização do comprimento de mistura simular o CMT é testada, destacando as regiões troposféricas onde os fluxos de momento linear horizontal são no sentido do gradiente ou contra o gradiente. Os fluxos no sentido do gradiente apresentam-se relacionados a uma fraca correlação entre os campos atmosféricos que caracterizam esta parameterização, sugerindo que as formulações dos fluxos de massa dentro da nuvem e o fenómeno de arrastamento do ar para dentro da nuvem devem ser revistos. A importância do ar saturado e não saturado para o CMT é estudada com o objectivo de alcançar um melhor entendimento acerca dos mecanismos físicos responsáveis pelo CMT. O ar não saturado e saturado na forma de correntes descendentes contribuem de forma determinante para o CMT e deverão ser considerados em futuras parameterizações do CMT e da convecção em nuvens cumulus. Métodos de agrupamento foram aplicados às contribuições do ar saturado e não saturado, analisando os campos da força de flutuação e da velocidade vertical da partícula de ar, concluindo-se a presença de ondas gravíticas internas como mecanismo responsável pelo ar não saturado. A força do gradiente de pressão dentro da nuvem é também avaliada, utilizando para este efeito a fórmula teórica proposta por Gregory et al. (1997). Uma boa correlação entre esta força e o produto entre efeito de cisalhamento do vento e a perturbação da velocidade vertical é registada, principalmente para as correntes ascendentes dentro da nuvem durante o episódio de convecção profunda. No entanto, o valor ideal para o coeficiente empírico c*, que caracteriza a influência da força do gradiente de pressão dentro da nuvem sobre a variação vertical da velocidade horizontal dentro da nuvem, não é satisfatoriamente alcançado. Bons resultados são alcançados através do teste feito à aproximação do fluxo de massa proposta por Kershaw e Gregory (1997) para o cálculo do CMT total, revelando mais uma vez a importância do ar não saturado para o CMT.

Higher order model for analysis of magneto-electro-elastic plates

In this paper is presented an higher-order model for static and free vibration analyses of magneto-electro-elastic plates, wich allows the analysis of thin and thick plates, which allows the analysis of thin and thick plates. The finite element model is a single layer triangular plate/shell element with 24 degrees of fredom for the generalized mechanical displacements. Two degrees on freedom are introduced per each element layer, one corresponding to the electrical potential and the other for magnetic potential. Solutions are obtained for different laminations of the magneto-electro-elastic plate, as well as for the purely elastic plate as a special case.

Stochastic ground motion simulation with geological site effects in damage asessment

Damage assessment of structures with a mechanical non linear model demands the representation of seismic action in terms of an accelerogram (dynamic analysis) or a response spectrum (pushover analysis). Stochastic ground motion simulation is largely used in regions where seismic strong-motion records are available in insufficient number. In this work we present a variation of the stochastic finite-fault method with dynamic corner frequency that includes the geological site effects. The method was implemented in a computer program named SIMULSIS that generate time series (accelerograms) and response spectra. The program was tested with the MW= 7.3 Landers earthquake (June 28, 1992) and managed to reproduce its effects. In the present work we used it to reproduce the effects of the 1980’s Azores earthquake (January 1, 1980) in several islands, with different possible local site conditions. In those places, the response spectra are presented and compared with the buildings damage observed.