Response of Materials during sliding on various surface textures

In the present investigation, basic studies were conducted using Inclined pin-on-plate sliding Tester to understand the role of surface texture of hard material against soft materials during sliding. Soft materials such as Al-Mg alloy, pure Al and pure Mg were used as pins and 080 M40 steel was used as plate in the tests. Two surface parameters of steel plates — roughness and texture — were varied in tests. It was observed that the transfer layer formation and the coefficient of friction which has two components, namely adhesion and plowing component, are controlled by the surface texture of harder material. For the case of Al-Mg alloy, stick-slip phenomenon was absent under both dry and lubricated conditions. However, for the case of Al, it was observed only under lubricated conditions while for the case of Mg, it was observed under both dry and lubricated conditions. Further, it was observed that the amplitude of stick-slip motion primarily depends on plowing component of friction. The plowing component of friction was highest for the surface that promotes plane strain conditions near the surface and was lowest for the surface that promotes plane stress conditions near the surface.

On continuous timed automata with input-determined guards

We consider a general class of timed automata parameterized by a set of “input-determined” operators, in a continuous time setting. We show that for any such set of operators, we have a monadic second order logic characterization of the class of timed languages accepted by the corresponding class of automata. Further, we consider natural timed temporal logics based on these operators, and show that they are expressively equivalent to the first-order fragment of the corresponding MSO logics. As a corollary of these general results we obtain an expressive completeness result for the continuous version of MTL.

Response of Materials During Sliding on Various Surface Textures

In the present investigation, soft materials, such as Al-4Mg alloy, high-purity Al and pure Mg pins were slid against hard steel plates of various surface textures to study the response of materials during sliding. The experiments were conducted using an inclined pin-on-plate sliding apparatus under both dry and lubricated conditions in an ambient environment. Two kinds of frictional response, namely steady-state and stick-slip, were observed during sliding. In general, the response was dependent on material pair, normal load, lubrication, and surface texture of the harder material. More specifically, for the case of Al-4Mg alloy, the stick-slip response was absent under both dry and lubricated conditions. For Al, stick-slip was observed only under lubricated conditions. For the case of Mg, the stick-slip response was seen under both dry and lubricated conditions. Further, it was observed that the amplitude of stick-slip motion primarily depends on the plowing component of friction. The plowing component of friction was the highest for the surfaces that promoted plane strain conditions and was the lowest for the surfaces that promoted plane stress conditions near the surface.

River water quality response under hypothetical climate change scenarios in Tunga-Bhadra river, India

Analysis of climate change impacts on streamflow by perturbing the climate inputs has been a concern for many authors in the past few years, but there are few analyses for the impacts on water quality. To examine the impact of change in climate variables on the water quality parameters, the water quality input variables have to be perturbed. The primary input variables that can be considered for such an analysis are streamflow and water temperature, which are affected by changes in precipitation and air temperature, respectively. Using hypothetical scenarios to represent both greenhouse warming and streamflow changes, the sensitivity of the water quality parameters has been evaluated under conditions of altered river flow and river temperature in this article. Historical data analysis of hydroclimatic variables is carried out, which includes flow duration exceedance percentage (e.g. Q90), single low- flow indices (e.g. 7Q10, 30Q10) and relationships between climatic variables and surface variables. For the study region of Tunga-Bhadra river in India, low flows are found to be decreasing and water temperatures are found to be increasing. As a result, there is a reduction in dissolved oxygen (DO) levels found in recent years. Water quality responses of six hypothetical climate change scenarios were simulated by the water quality model, QUAL2K. A simple linear regression relation between air and water temperature is used to generate the scenarios for river water temperature. The results suggest that all the hypothetical climate change scenarios would cause impairment in water quality. It was found that there is a significant decrease in DO levels due to the impact of climate change on temperature and flows, even when the discharges were at safe permissible levels set by pollution control agencies (PCAs). The necessity to improve the standards of PCA and develop adaptation policies for the dischargers to account for climate change is examined through a fuzzy waste load allocation model developed earlier. Copyright (C) 2011 John Wiley & Sons, Ltd.

Measurement of Stress-Strain Response of A Rammed Earth Prism In Compression Using Fiber Bragg Grating Sensors

A comparative study of strain response and mechanical properties of rammed earth prisms, has been made using Fiber Bragg Grating (FBG) sensors (optical) and clip-on extensometer (electro-mechanical). The aim of this study is to address the merits and demerits of traditional extensometer vis-à-vis FBG sensor; a uni-axial compression test has been performed on a rammed earth prism to validate its structural properties from the stress - strain curves obtained by two different methods of measurement. An array of FBG sensors on a single fiber with varying Bragg wavelengths (..B), has been used to spatially resolve the strains along the height of the specimen. It is interesting to note from the obtained stress-strain curves that the initial tangent modulus obtained using the FBG sensor is lower compared to that obtained using clip-on extensometer. The results also indicate that the strains measured by both FBG and extensometer sensor follow the same trend and both the sensors register the maximum strain value at the same time.

Applications of solid electrolytes in galvanic sensors

The concepts and theoretical origins of conduction domains for solid electrolytes and electrode polarization are outlined briefly. The point electrode made of the ' solid electrolyte material is useful for deflecting the semipermeability flux away from the electrode. The emf of galvanic sensors consisting of two solid electrolytes in intimate contact with each other and in which transport occurs by a common ion is reviewed. The voltage of such cells depends on the chemical potential of the active species at the interface between the two electrolytes, which can be evaluated from the transport properties of electrolytes using a numerical procedure. The factors governing the speed of response of solid electrolyte gas sensors are analyzed. A rigorous expression for the emf of non-isothermal galvanic sensors and the criterion for the design of temperature compensated reference electrodes for nonisothermal galvanic sensors are outlined. Non-isothermal sensors are useful for the continuous monitoring of concentrations or chemical potentials in reactive systems at high temperatures. The principles of operation of galvanic sensors for oxygen, sulphur, oxides of sulphur (SOx,x=2,3), carbon, oxides uf carbon (COx,x= 1,2), oxides of nitrogen (NOx,x= 1,2) and silicon are discussed. The use of auxiliary electrodes in galvanic sensors to expand the detection capability of known solid electrolytes to a large number of species is explained with reference to sensors for sulphur and oxides of sulphur (SOx,x=2,3).Finally the cause of the common errors in galvanic measurements and test for the correct functioning of galvanic sensors is given.

On Convergence of Differential Evolution Over a Class of Continuous Functions With Unique Global Optimum

Differential evolution (DE) is arguably one of the most powerful stochastic real-parameter optimization algorithms of current interest. Since its inception in the mid 1990s, DE has been finding many successful applications in real-world optimization problems from diverse domains of science and engineering. This paper takes a first significant step toward the convergence analysis of a canonical DE (DE/rand/1/bin) algorithm. It first deduces a time-recursive relationship for the probability density function (PDF) of the trial solutions, taking into consideration the DE-type mutation, crossover, and selection mechanisms. Then, by applying the concepts of Lyapunov stability theorems, it shows that as time approaches infinity, the PDF of the trial solutions concentrates narrowly around the global optimum of the objective function, assuming the shape of a Dirac delta distribution. Asymptotic convergence behavior of the population PDF is established by constructing a Lyapunov functional based on the PDF and showing that it monotonically decreases with time. The analysis is applicable to a class of continuous and real-valued objective functions that possesses a unique global optimum (but may have multiple local optima). Theoretical results have been substantiated with relevant computer simulations.

Continuous Recording of Retardation and Intensity of Echoes from the Ionosphere

Pulse retardation method of Breit and Tuve has been modified to record continuously the equivalent height as well as the intensity of reflections from the ionosphere. Synchronized pulses are transmitted, and the received ground pulse and the reflected pulses, after amplification and suitable distortion, are applied to the focusing cylinder of a cathode ray tube the horizontal deflecting plates of which are connected to a synchronized linear time base circuit. The pattern on the screen is composed of a bright straight line corresponding to the time base with dark gaps corresponding to the received pulses. The distance between the initial points of the gaps represents retardation while the widths of the gaps correspond to the intensity of the pulses. The pattern is photographed on a vertically moving film. One of the first few records taken at Bangalore on 4 megacycles is reproduced. It shows, among other things, that the less retarded component of magneto-ionic splitting from the F layer is present most of the time. Whenever the longer retardation component does occur, it has stronger intensity than the former. Towards the late evening hours, just before disappearing, when the F layer rises and exhibits magnetoionic splitting, the intensity of the less retarded component is extremely low compared with the other component.

Dielectric response of BaZrO3/BaTiO3 and SrTiO3/BaZrO3 superlattices

Dielectric materials with high tunability, low loss, and desired range of permittivity are an attractive class of materials for a variety of applications in microwave components such as tunable filters, phase shifters, antennas, etc. In this article, we have investigated the low frequency dielectric properties of BaZrO3/BaTiO3 and SrTiO3/BaZrO3 superlattices of varying modulation periods for the potential application toward electrically tunable devices. The dielectric response of the superlattices as a function of temperature revealed remarkable stability for both types of superlattices, with no observed dielectric anomalies within that range. Dielectric losses were also nominally low with minimal variation within the measured temperature range. Sufficiently high tunability of ∼ 40% was observed for the BaZrO3/BaTiO3 superlattices at the lowest individual layer thicknesses. In comparison, the SrTiO3/BaZrO3 superlattices showed a minimum tunability for lowest period structures. It showed maximum tunability of ∼ 20% at 10 kHz and room temperature at an intermediate dimension of 3.85 nm periodicity superlattice. The tunability value degraded with increasing as well as decreasing periodicities for the SrTiO3/BaZrO3 superlattices. The dielectric response has been explained on the basis of size effects, interlayer coupling between dissimilar materials, domain contribution, and depolarizing electric fields.

Influence of surge impedance of the connecting lead in response time measurement of u.h.v. damped capacitive voltage dividers

In the determination of the response time of u.h.v. damped capacitive impulse voltage dividers using the CIGRE IMR-1MS group (1) method and the arrangement suggested by the International Electrotechnical Commission (the I EC square loop),the surge impedance of the connecting lead has been found to influence the accuracy of determination. To avoid this difficulty,a new graphical procedure is proposed. As this method uses only those data points which can be determined with good accuracy, errors in response-time area evaluation do not influence the result.

A Method of Evaluating Electrical Response of Solion Diodes

A method of evaluating the transient electrical response of a solion diode when excited by different current stimuli is given. This method is extended to obtain the transient response of the solion when connected in a circuit. To illustrate the utility of this method a circuit incorporating a solion diode has been analyzed.