Advances in contact algorithms and their application to tires

Currently used techniques for tire contact analysis are reviewed. Discussion focuses on the different techniques used in modeling frictional forces and the treatment of contact conditions. A status report is presented on a new computational strategy for the modeling and analysis of tires, including the solution of the contact problem. The key elements of the proposed strategy are: (1) use of semianalytic mixed finite elements in which the shell variables are represented by Fourier series in the circumferential direction and piecewise polynomials in the meridional direction; (2) use of perturbed Lagrangian formulation for the determination of the contact area and pressure; and (3) application of multilevel iterative procedures and reduction techniques to generate the response of the tire. Numerical results are presented to demonstrate the effectiveness of a proposed procedure for generating the tire response associated with different Fourier harmonics

Exploiting symmetries in the modeling and analysis of tires

A computational procedure is presented for reducing the size of the analysis models of tires having unsymmetric material, geometry and/or loading. The two key elements of the procedure when applied to anisotropic tires are: (1) decomposition of the stiffness matrix into the sum of an orthotropic and nonorthotropic parts; and (2) successive application of the finite-element method and the classical Rayleigh-Ritz technique. The finite-element method is first used to generate few global approximation vectors (or modes). Then the amplitudes of these modes are computed by using the Rayleigh-Ritz technique. The proposed technique has high potential for handling practical tire problems with anisotropic materials, unsymmetric imperfections and asymmetric loading. It is also particularly useful for use with three-dimensional finite-element models of tires

Exploiting symmetries in the modeling and analysis of tires

A simple and efficient computational strategy for reducing both the size of a tire model and the cost of the analysis of tires in the presence of symmetry-breaking conditions (unsymmetry in the tire material, geometry, or loading) is presented. The strategy is based on approximating the unsymmetric response of the tire with a linear combination of symmetric and antisymmetric global approximation vectors (or modes). Details are presented for the three main elements of the computational strategy, which include: use of special three-field mixed finite-element models, use of operator splitting, and substantial reduction in the number of degrees of freedom. The proposed computational stategy is applied to three quasi-symmetric problems of tires: linear analysis of anisotropic tires, through use of semianalytic finite elements, nonlinear analysis of anisotropic tires through use of two-dimensional shell finite elements, and nonlinear analysis of orthotropic tires subjected to unsymmetric loading. Three basic types of symmetry (and their combinations) exhibited by the tire response are identified

Modeling and analysis of the space shuttle nose-gear tire with semianalytic finite elements

A computational procedure is presented for the geometrically nonlinear analysis of aircraft tires. The Space Shuttle Orbiter nose gear tire was modeled by using a two-dimensional laminated anisotropic shell theory with the effects of variation in material and geometric parameters included. The four key elements of the procedure are: (1) semianalytic finite elements in which the shell variables are represented by Fourier series in the circumferential direction and piecewise polynominals in the meridional direction; (2) a mixed formulation with the fundamental unknowns consisting of strain parameters, stress-resultant parameters, and generalized displacements; (3) multilevel operator splitting to effect successive simplifications, and to uncouple the equations associated with different Fourier harmonics; and (4) multilevel iterative procedures and reduction techniques to generate the response of the shell. Numerical results of the Space Shuttle Orbiter nose gear tire model are compared with experimental measurements of the tire subjected to inflation loading

Water catchment area and management method

Due to critical and obvious effect of the wastewater comes from the industry, agriculture and industrial activity nearby the dam has led to environmental issues in Sembrong dam, Kluang Johor which caused negative impacts to the biological, chemical and physical properties of water river environments. The dam itself contained a large number of algae which caused the blocking of sunlight, could not enter directly to the water surface and it threatening to the aquatic life. The dam also traps sediments, which are crucial for maintaining physical progressions and habitats of the dam. The chapter introduce “G.E.T” formula as management method to overcome the pollution problems. The implementation of “G.E.T” formula is basically to improve the urban environmental condition as key for urban policy and environmental management. Sustainable management and utilisation of resources is a guidance in pursuing the development of agricultural and forestry activity at dam area

Computational Modeling of Tires

This document contains presentations and discussions from the joint UVA/NASA Workshop on Computational Modeling of Tires. The workshop attendees represented NASA, the Army and Air force, tire companies, commercial software developers, and academia. The workshop objectives were to assess the state of technology in the computational modeling of tires and to provide guidelines for future research

Application of Carbon-based Nanofluids in Heat Exchangers: Current Trends

Abstract : The thermal performance of a heat exchanger can be enhanced by adding carbon nanostructured materials such as carbon nanotubes and graphene to the conventional working fluid. When nanomaterials are suspended in the working fluid, the fluid is known as Nanofluid. The enhancement in the thermal and rheological properties of the fluid is responsible for the augmentation in heat transfer performance. The influence of carbon nanomaterial on the thermophysical properties, heat transfer characteristics and flow properties are reviewed. The current trends on the utilization of carbon-based nanofluids in heat exchangers were reported. The study shows that carbon-based nanofluids have the potential to improve the performance of heat exchanger and reduce the cost of fabrication by reducing heat exchange area. The study identifies the scope for future study

Molecular features of biguanides required for targeting of mitochondrial respiratory complex I and activation of AMP-kinase.

BACKGROUND: The biguanides are a family of drugs with diverse clinical applications. Metformin, a widely used anti-hyperglycemic biguanide, suppresses mitochondrial respiration by inhibiting respiratory complex I. Phenformin, a related anti-hyperglycemic biguanide, also inhibits respiration, but proguanil, which is widely used for the prevention of malaria, does not. The molecular structures of phenformin and proguanil are closely related and both inhibit isolated complex I. Proguanil does not inhibit respiration in cells and mitochondria because it is unable to access complex I. The molecular features that determine which biguanides accumulate in mitochondria, enabling them to inhibit complex I in vivo, are not known. RESULTS: Here, a family of seven biguanides are used to reveal the molecular features that determine why phenformin enters mitochondria and inhibits respiration whereas proguanil does not. All seven biguanides inhibit isolated complex I, but only four of them inhibit respiration in cells and mitochondria. Direct conjugation of a phenyl group and bis-substitution of the biguanide moiety prevent uptake into mitochondria, irrespective of the compound hydrophobicity. This high selectivity suggests that biguanide uptake into mitochondria is protein mediated, and is not by passive diffusion. Only those biguanides that enter mitochondria and inhibit complex I activate AMP kinase, strengthening links between complex I and the downstream effects of biguanide treatments. CONCLUSIONS: Biguanides inhibit mitochondrial complex I, but specific molecular features control the uptake of substituted biguanides into mitochondria, so only some biguanides inhibit mitochondrial respiration in vivo. Biguanides with restricted intracellular access may be used to determine physiologically relevant targets of biguanide action, and for the rational design of substituted biguanides for diverse clinical applications

Occupational safety basics understanding in oil and gas industry: An evaluation

In project management, risk is a surprise that might be resulted in a good, or bad, impact on a project. However, people tend to consider it a threat. This study is an evaluation work to the understanding of the risk management and safety culture of the construction sector in oil and gas industry in Iraq. A survey questionnaire was prepared, tested, distributed to a sample of engineers, from several engineering specialties, who are working on different levels in the mentioned sector. A high percent of the respondents are safety engineers, and some have a higher university degree, e.g. MS an Ph.D. The collected data then analyzed using different statistical approaches. The results show that there is a good understanding of the safety in general among engineers. However, risk management and planning tools are not understood effectively among the respondents. Moreover, having a higher degree or specializing in different majors have no impact on perceptional understanding of the safety and risk. This study is one of the first steps in studying the occupational safety in Iraq construction and oil and gas industries. Since Iraq is considered for rebuilding after different wars, international firms are in need to understand how safety is managed and to what level it is applied. From this perspective, this study is one of studies that help achieving the firms’ goal regarding safety

Wound Healing Activities of Rafflesia Hasseltii Extract in Rats

The effects of topical application of Rafflesia hasseltii buds and flowers extract on the rate of wound healing and histology of healed wound were assessed. Four groups of adult male Sprague Dawley rats were experimentally wounded in the posterior neck area. A thin layer of blank placebo was applied topically to wounds of Group 1 rats. Wounds of experimental animals (Group 2 and 3) were treated with placebo containing 5% and 10% R. hasseltii buds extract, respectively. A thin layer of Intrasite gel was applied topically to wounds of Group 4 animals as reference. Macroscopically, wounds treated with placebo containing 5% and 10% R. hasseltii buds extract or Intrasite gel have been significantly accelerated the rate of wound healing compared to placebo-treated wounds. Histological analysis of healed wounds has confirmed this effect. Wounds treated with placebo containing 5%, 10% R. hasseltii buds extract or Intrasite gel showed markedly less scar width at wound enclosure and granulating tissue contained markedly more collagen and proliferating fibroblasts, but with the absence of inflammatory cells compared to wounds treated with blank placebo. In conclusion, the findings of increased rate of wound closure and contraction together with the histological findingssuggest that Rafflesia hasseltii buds extract is very effective in accelerating the wound healing process