Localised deformation patterning in 2D granular materials revealed by digital image correlation

Tests have been performed on an analogue two-dimensional granular material in a special laboratory apparatus that allows the application of general stress or strain conditions. Digital image correlation of pairs of consecutive photographs taken during the tests has enabled fields of displacement and hence strain to be determined. Thus direct observation of internal displacements and strains has been possible for a series of general strain increments with different orientations of principal strain and different imposed angles of dilation. This analysis has successfully provided clear evidence of evolving internal structures of deformation. The observed evolving structures consist of bands of localised deformation and ‘cells’ of low deformation between the bands. The orientations of the identified localised features and cells are seen to depend on the applied strain path. The characteristic features and dimensions of the bands have been approximately identified.     

Sand–rubber mixtures undergoing isotropic loading: derivation and experimental probing of a physical model

The volume of scrap tyres, an undesired urban waste, is increasing rapidly in every country. Mixing sand and rubber particles as a lightweight backfill is one of the possible alternatives to avoid stockpiling them in the environment. This paper presents a minimal model aiming to shed light on the relevant physical parameters governing the evolution of the void ratio of sand–rubber mixtures undergoing an isotropic compression loading, where the mixtures consist of various volume ratios of rubber. It is based on the idea that, when pressure is applied, the rubber particles deform and partially fill the porous space of the system, leading to a decrease of the void ratio with increasing pressure. We show that our simple approach is capable of reproducing experimental data obtained with sand and rubber of similar particle size distributions up to mixtures composed of 50% of rubber. The effect of the particle shape and size on the model parameters is discussed.     

Modelling tensile/compressive strength ratio of fibre reinforced cemented soils

The present work proposes a theoretical model for predicting the splitting tensile strength (q_t) - unconfined compressive strength (q_u) ratio of artificially cemented fibre reinforced soils. The proposed developments are based on the concept of superposition of failure strength contributions of the soil, cement and fibres phases. The soil matrix obeys the critical state soil mechanics concept, while the strength of the cemented phase can be described using the Drucker-Prager failure criterion and fibres contribution to strength is related to the composite deformation. The proposed developments are challenged to simulate the experimental results for fibre reinforced cemented Botucatu residual soil, for 7 days of cure. While the proposed analytical relation fits well the experimental data for this material, it also provides a theoretical explanation for some features of the experimentally derived strength relationships for artificially fibre reinforced cemented clean sands. A parametric study to analyse the effect of adding different fibre contents and fibre properties is provided. The proposed modelling developments also confirm the existence of a rather constant q_t/q_u ratio with moulding density, cement and fibre contents .     

Effects of tool rotation and pin diameter on fatigue properties of friction stir welded lap joints

The objective of this study was to determine the effects of the tool pin diameter and tool rotation on the fatigue behaviour of friction stir welded (FSW) lap joints. FSW lap joints of AA 5754 aluminium alloy plates were produced by means of a conventional semiautomatic milling machine. Consequently, defect free FSW lap joints were produced on alloy plates at a constant traverse speed but with different tool pin diameter and tool rotation. Therefore, within this study, tool rotation and the tool pin diameter were accepted as variable parameters, while others held fixed. The results of the tests performed, indicate that an optimisation is required for the studied parameters, in order to obtain reasonable fatigue strength. An index, related to tool rotation, traverse speed, pin diameter, and pin height can be identified and used to select optimum parameters for FSW applications.     

Is garlic a promising food for benign prostatic hyperplasia and prostate cancer?

Prostate cancer is one of the most common male malignancies worldwide, and benign prostatic hyperplasia (BPH) is a common cause of lower urinary tract symptoms in elderly men. Garlic (Allium sativum) has been known to have anti-inflammatory, anti-cancer and antioxidant effects. Owing to these effects, garlic and its preparations have been used for the treatment of prostate cancer and relief of BPH symptoms for decades. It is thought that the mechanism(s) through which garlic may show anti-cancer and anti-inflammatory effects should be investigated further. Several researchers are attempting to demonstrate the useful properties of garlic and its mechanism(s) of action. This review aims to present the current studies related with the effects of garlic in prostate diseases, namely prostate cancer and BPH.     

Design and implementation of a hybrid fuzzy logic controller for a quadrotor VTOL vehicle

Helicopters have generated considerable interest in both the control community due to their complex dynamics, and in military community because of their advantages over regular aerial vehicles. In this paper, we present the modeling and control of a four rotor vertical take-off and landing (VTOL) unmanned air vehicle known as quadrotor aircraft. This model has been generated using Newton-Euler equations. In order to control the helicopter, classical PD (proportional derivative) and Hybrid Fuzzy PD controllers have been designed. Although fuzzy control of various dynamical systems has been presented in literature, application of this technology to quadrotor helicopter control is quite new. A quadrotor helicopter has nonlinear characteristics where classical control methods are not adequate especially when there are time delays, disturbances and nonlinear vehicle dynamics. On the other hand, Fuzzy control is nonlinear and it is thus suitable for nonlinear system control. Matlab Simulink has been used to test, analyze and compare the performance of the controllers in simulations. For the evaluation of the autonomous flight controllers, some experiments were also performed. For this purpose, an experimental test stand has been designed and manufactured. This study showed that although, both of the classical PD and the Fuzzy PD controllers can control the system properly, the Fuzzy PD controllers performed slightly better than the classical PD controllers, and have benefits such as better disturbance rejection, ease of building the controllers.     

The Responses of Ionospheric Conductivities on the Mid-Latitudes to Changes in the BZ Component of Interplanetary Magnetic Field

Wireless Personal Communications - In this study, we investigate the response of the ionospheric conductivities on the middle latitudes to the southward and northward turnings of the BZ component...     

Energy recovery from hydrogen combustion at elevated pressures

Hydrogen is assumed as one of the most environmentally benign fuels. By the combustion of hydrogen enormous amount of H₂O; and therefore, latent heat is produced. Because, there is not so much need to heat at low temperatures, methods are needed to recover latent heat at higher temperatures. One of the methods to upgrade the latent heat at higher temperatures is the method of combustion at elevated pressures. Increasing the pressure of the exhaust gas makes it possible to recover latent heat and higher extra exergy output from the system. In this work, both latent and sensible heat recoveries at elevated pressures are investigated using environmentally friendly fuel hydrogen. It is shown that coefficient of performance (COP) and exergy efficiency (${\eta }_{ex}$) is very satisfactory even at high pressures.     

Evaluation of the effect of food and beverages on enamel and restorative materials by SEM and Fourier transform infrared spectroscopy

Objectives To examine different types of restorative materials used in children as well as primary and permanent teeth enamel when affected by erosive foods. Materials and Method Buttermilk, fruit yoghurt, Coca‐cola, fruit juice, Filtek Z‐250, Dyract Extra, Fuji II LC, and Fuji IX and tooth enamel were used. Measurements were performed on 1‐day, 1‐week, 1‐month, 3‐month, 6‐month time periods by using ATR‐FTIR technique and surface of the specimens were examined with SEM. Results Permanent tooth showed the least change among human tooth samples when compared to restorative materials. Among filler materials, the most change was observed in Fuji IX. In terms of beverages the most changes on absorption peaks obtained from spectra were seen on the samples held in Coca‐Cola and orange‐juice. Conclusion The exposure of human enamel and restorative materials to acidic drinks may accelerate the degradation process and so reduce the life time of filler materials at equivalent integral exposure times longer than three months. Clinical Relevance Erosive foods and drinks having acidic potential destroy not only tooth enamel but also restorative materials. Microsc. Res. Tech. 77:79–90, 2014. © 2013 Wiley Periodicals, Inc.     

Determination of the relationship between uniaxial and triaxial swelling equations for clay bearing rocks

Design in swelling mediums is mostly based on uniaxial data since the standards proposed by the International Society for Rock Mechanics Commission on Swelling Rocks for uniaxial tests are in the form of recommendations, triaxial sets are not highly available; and there is no standard developed for triaxial tests. The main purpose of this study is to define the relationship between the uniaxial and the triaxial swelling equations and to predict the triaxial values using the uniaxial data. The other purpose of the study is to contribute to the development of the standards and to expand the data available in the literature about triaxial swelling behavior. Numerous uniaxial and triaxial swelling tests were performed on the samples from seven different locations, in Turkey, in a state of the art swelling laboratory. As a result of the determination of the triaxial swelling behavior of these samples, the relationships between the uniaxial and the triaxial swelling data for the individual samples as well as the whole set of samples are expressed by the equations derived from the statistical analyses.