Finite Elements for a Beam System With Nonlinear Contact Under Periodic Excitation

Solar arrays are structures which are connected to satellites; during launch, they are in a folded position and submitted to high vibrations. In order to save mass, the flexibility of the panels is not negligible and they may strike each other; this may damage the structure. To prevent this, rubber snubbers are mounted at well chosen points of the structure; a prestress is applied to the snubber; but it is quite difficult to check the amount of prestress and the snubber may act only on one side; they will be modeled as one sided springs (see figure 2). In this article, some analysis for responses (displacements) in both time and frequency domains for a clamped-clamped Euler-Bernoulli beam model with a spring are presented. This spring can be unilateral or bilateral fixed at a point. The mounting (beam +spring) is fixed on a rigid support which has a sinusoidal motion of constant frequency. The system is also studied in the frequency domain by sweeping frequencies between two fixed values, in order to save the maximum of displacements corresponding to each frequency. Numerical results are compared with exact solutions in particular cases which already exist in the literature. On the other hand, a numerical and theoretical investigation of nonlinear normal mode (NNM) can be a new method to describe nonlinear behaviors, this work is in progress

Modeling power grids

We present a method to construct random model power grids that closely match statistical properties of a real power grid. The model grids are more difficult to partition than a real grid.Comment: 9 pages, 5 figure

Transport properties of a two impurity system: a theoretical approach

A system of two interacting cobalt atoms, at varying distances, was studied in a recent scanning tunneling microscope experiment by Bork et. al.[Nature Phys. 7, 901 (2011)]. We propose a microscopic model that explains, for all experimentally analyzed interatomic distances, the physics observed in these experiments. Our proposal is based on the two-impurity Anderson model, with the inclusion of a two-path geometry for charge transport. This many-body system is treated in the finite-U slave boson mean-field approximation and the logarithmic-discretization embedded-cluster approximation. We physically characterize the different charge transport regimes of this system at various interatomic distances and show that, as in the experiments, the features observed in the transport properties depend on the presence of two impurities but also on the existence of two conducting channels for electron transport. We interpret the splitting observed in the conductance as the result of the hybridization of the two Kondo resonances associated with each impurity.Comment: 5 pages, 5 figure

Renoprotective role of tualang honey against high cholesterol diet induced acute kidney diseases in an animal model

Introduction: Although there is a growing insight into the causes and mechanisms of kidney diseases, preventive and therapeutic measures are still few. The aim of this study was therefore to determine the renoprotective effect of tualang honey against high cholesterol diet induced acute kidney disease in an animal model. Materials and method: Ten female Sprague-Dawley rats were divided into two groups: high cholesterol diet (HCD) group, fed with 12% cholesterol diet with 0.3% cholic acid, and high cholesterol diet with tualang honey (HCD + TH) group, fed with HCD with oral daily dose of 1.4 g/kg/day of tualang honey by gavage. Biochemical analysis of lipid profile and renal function were performed at 48 hours, 7 days, and 6 weeks of the experiment. The animals were sacrificed at 6 weeks and the kidneys were harvested for histological examination. Results: There was no significant difference between the HCD and the HCD+TH groups in the level of TC. The mean serum LDL-c, TG and vLDL levels at completed 48 hours and 7 days for the HCD+TH group were lower as compared to the HCD group. The only significant difference in renal function test between HCD and HCD + TH groups reported were theserum creatinine at completed 48 hours. Histological examination of the kidney tissue of the HCD and HCD+TH groups at 6 weeks revealed segmental mesangial hypercellularity and mesangial matrix expansion of the glomeruli. Conclusion: Tualang honey supplementation has resulted in an improvement of the renal profile which is suggestive of its renoprotective effect. However, the histopathological examination of the kidneys revealed similar changesin both groups and this may be related to the dose of honey used in the study. Additionally, tualang honey showed improvement in LDL-c, triglyceride and vLDL levels indicating its lipid lowering activities

Early effects of high cholesterol diet on the kidney of an animal model

BACKGROUND: Previous studies have proven that there exists a complex association between progressive kidney damage and hypercholesterolemia. Most of them focused on the impact of chronically high blood cholesterol levels on the kidney. Information on the early effects of hypercholesterolemia on the kidney is still lacking. The aim of this study is therefore to determine early effects of high cholesterol diet on the kidney in an animal model. METHODOLOGY: Ten female Sprague-Dawley rats were divided into two groups: the control group, fed with commercial rat pellet and the high cholesterol diet (HCD) group, fed with 12% cholesterol diet with 0.3% cholic acid. Biochemical analysis of the lipid profile and renal function were performed at completed 48 hours, 7 days, and 6 weeks of the experiment. The animals were sacrificed at 6 weeks and the kidneys were harvested for histological examination. RESULTS: The HCD group rats had significantly higher levels of serum total cholesterol (at 7 days and 6 weeks). The HDL-c and triglyceride levels were, however lower at 6 weeks. The mean serum creatinine level of the HCD group was increased after 48 hours and 7 days compared to control group. Histological examination of the kidney tissue of the HCD group at 6 weeks revealed segmental mesangial hypercellularity and mesangial matrix expansion of the glomeruli. CONCLUSION: The 12% cholesterol diet induced dyslipidaemia in the animal model. It resulted in acute kidney injury based on the serum creatinine at 48 hours and also 7 days. Kidney tissues examined at 6 weeks revealed changes confined to mesangial cells of the renal glomeruli

Design a Cloud Security Model in VANET Communication: Implementation, Performance and Security Analysis

In the first paper of this work, the design and the architecture of our proposed model framework, VANET Security as a Service (VSaaS), was discussed. In this second paper, the performance metrics measurements will be investigated through the NS2, SUMO and Trans simulations, to evaluate the security overhead of the secure Vehicle Information Messages (VIMs), which are sent by the vehicles to the cloud as a coarse-grained information. Moreover, our proposed model framework (VSaaS) will be discussed against the security requirements in the VANET

Design a Cloud Security Model in VANET Communication: Design and Architecture

During the last few years, Intelligent Transportation System (ITS) has been progressed at a rapid rate, which aimed to improve the transportation activities in the terms of the safety and efficiency. According to many issues with the traditional Vehicular Ad-Hoc Networks (VANET), some efforts are made to merge the VANET with the cloud technology. This work proposes the VANET based on the cloud (V2Cloud), and designs a security model framework that is hosted on the cloud to manage the security services, and provide a secure VANET communication between the different entities eg vehicles, authorities and etc. This security model framework is called VANET Security as a Service (VSaaS). Our works will presented in a set of two papers. In this first one, it presents VSaaS design and architecture in order to show that the VSaaS fulfills the VANET's security requirements, and protects the VANET against the different types of attacks. The second paper will present the progress towards the implementation and the security analysis of the proposed architecture, along with the results of the performance of the security overhead for the secure Vehicle Information Messages (VIMs), which are sent by vehicles to the cloud as a coarse-grained information

Achieving business and IT alignment from organisational learning perspectives

Business and IT alignment has continued as a top concern for business and IT executives for almost three decades. Many researchers have conducted empirical studies on the relationship between business-IT alignment and performance. Yet, these approaches, lacking a social perspective, have had little impact on sustaining performance and competitive advantage. In addition to the limited alignment literature that explores organisational learning that is represented in shared understanding, communication, cognitive maps and experiences. Hence, this paper proposes an integrated process that enables social and intellectual dimensions through the concept of organisational learning. In particular, the feedback and feed- forward process which provide a value creation across dynamic multilevel of learning. This mechanism enables on-going effectiveness through development of individuals, groups and organisations, which improves the quality of business and IT strategies and drives to performance

Study of Heat Pipe Thermal Performance with Internal Modified Geometry

The aim of this study was to investigate the effect of inserting a new internal tube packing (TP) on the thermal performance of a thermosyphon heat pipe (THP). The THP pipe was made from copper with an inner diameter of 17.4 mm and length of 600 mm. The new internal tube packing (TP) had a central copper disc with two copper tubes soldered onto both sides to transport vapor and condensate. The upper tube or riser had an inner diameter of 8.3 mm and was 300 mm long; it was connected to a hole in the disc from the upper side to transport the steam to the condenser section. The lower tube or downcomer had an inner diameter of 5 mm, was 225 mm long and was connected to the lower side of the disc to collect the condensate and transport it to the evaporator. The TP was inserted inside the THP to complete the design of the improved heat pipe (TPTHP). Experimental results showed that the TPTHP reduces the transit time from 16 to 11 min and the thermal resistance by 17–62% based on the input power and depending on the conditions of the THP. The results also showed that the inclination angle and filling ratio have no effect on the thermal resistance of the TPTHP

A Lumped-Parameter Model for Nonlinear Waves in Graphene

A lumped-parameter nonlinear spring-mass model which takes into account the third-order elastic stiffness constant is considered for modeling the free and forced axial vibrations of a graphene sheet with one fixed end and one free end with a mass attached. It is demonstrated through this simple model that, in free vibration, within certain initial energy level and depending upon its length and the nonlinear elastic constants, that there exist bounded periodic solutions which are non-sinusoidal, and that for each fixed energy level, there is a bifurcation point depending upon material constants, beyond which the periodic solutions disappear. The amplitude, frequency, and the corresponding wave solutions for both free and forced harmonic vibrations are calculated analytically and numerically. Energy sweep is also performed for resonance application