<Emphasis Type="Italic">κ</Emphasis>-<Emphasis Type="Italic">PMP</Emphasis>: Enhancing Physics-based Motion Planners with Knowledge-Based Reasoning

Physics-based motion planning is a challenging task, since it requires the computation of the robot motions while allowing possible interactions with (some of) the obstacles in the environment. Kinodynamic motion planners equipped with a dynamic engine acting as state propagator are usually used for that purpose. The difficulties arise in the setting of the adequate forces for the interactions and because these interactions may change the pose of the manipulatable obstacles, thus either facilitating or preventing the finding of a solution path. The use of knowledge can alleviate the stated difficulties. This paper proposes the use of an enhanced state propagator composed of a dynamic engine and a low-level geometric reasoning process that is used to determine how to interact with the objects, i.e. from where and with which forces. The proposal, called κ-PMP can be used with any kinodynamic planner, thus giving rise to e.g. κ-RRT. The approach also includes a preprocessing step that infers from a semantic abstract knowledge described in terms of an ontology the manipulation knowledge required by the reasoning process. The proposed approach has been validated with several examples involving an holonomic mobile robot, a robot with differential constraints and a serial manipulator, and benchmarked using several state-of-the art kinodynamic planners. The results showed a significant difference in the power consumption with respect to simple physics-based planning, an improvement in the success rate and in the quality of the solution paths.     

Computer simulation of the performance of a solar pond in the southern part of Iran

In this study a computer model of a solar pond to be built in the southern part of Iran is developed. The input to the program is the daily solar radiation, ambient temperature, evaporation rate, etc. The temperature rise of the pond for various rates of energy removal is the output of the program. A parametric study on such a computer simulation for optimization of performance of the actual solar pond is quite economical. Several computer experiments are carried out for various conditions of interest of the area around Shiraz in the southern part of Iran. Temperature rise of the bottom of the pond is calculated for different rates of energy removal. It is observed that after a few months of operation, the temperature of the bottom of the pond becomes sufficiently high to allow energy extraction from the pond. The temperature variation of the pond for different overall efficiencies of the pond under various conditions are also obtained and discussed. The response of the pond to several consecutive days of cloudiness is also studied. It is concluded that solar ponds are also reliable solar collector-storage systems for this part of the world.     

Electrical power generation from piezoelectric electrospun nanofibers membranes: electrospinning parameters optimization and effect of membranes thickness on output electrical voltage

Nanogenerators based on piezoelectric nanofibers capable to scavenging mechanical energy from the environment and converting into usable electrical energy. In this research work, the electrospinning parameters were optimized to produce randomly oriented uniform PVDF nanofiber mats without structural defects. Then, optimized nanofiber membranes with different thickness (110, 220, and 310 μm) were fabricated and their output voltages as a performance factor of the nanogenerator were measured. Results indicated that the nanogenerator based on piezoelectric nanofibers can generate voltage as high as several volts electrical outputs by applying mechanical impact. Finally, to investigate the effect of pure thickness on power harvesting efficiency, output voltages of samples were normalized to thickness. Results showed that in spite of the existed literature, increases in nanofiber membrane’s thickness can lead to decrease the output voltage of nanogenerator. These results imply promising applications for various wearable self-powered electrical devices within the clothing systems.     

Fuzzy Bayesian system reliability assessment based on prior two‐parameter exponential distribution under different loss functions

The fuzzy Bayesian system reliability assessment based on prior two‐parameter exponential distribution under squared error symmetric loss function and precautionary asymmetric loss function is proposed in this paper. In order to apply the Bayesian approach, the fuzzy parameters are assumed as fuzzy random variables with fuzzy prior distributions. Because the goal of the paper is to obtain fuzzy Bayes point estimators of system reliability assessment, prior distributions of location‐scale family has been changed to scale family with change variable. On the other hand, also the computational procedures to evaluate the membership degree of any given Bayes point estimate of system reliability have been provided. In order to achieve this purpose, we transform the original problem into a non‐linear programming problem. This non‐linear programming problem is then divided into four sub‐problems for the purpose of simplifying computation. Finally, the sub‐problems can be solved by using any commercial optimizers, e.g. GAMS or LINGO. Copyright © 2010 John Wiley & Sons, Ltd.     

Hopf bifurcation index for large scale power systems

In this paper, we propose a novel index for the prediction of the Hopf bifurcation (HB) in power systems. The proposed index has strictly less processing load and less computation time in comparison to former HB indices. It also uses modern control properties of the power system such as system matrix and critical eigenvalue. Therefore, stochastic subspace system identification (SSSI) is used as a tool for estimation and prediction of the proposed HB index. Combining beneficial properties of SSSI methods and the processing advantages of the proposed index, we project a new algorithm for power system monitoring. The algorithm is easy and straight-forward. We conduct several test conditions for the proposed materials using 2-area 4-machine system, New England 10-Machine and IEEE 50-machine system. Simulation outcome expresses good performance of proposed index in comparison to former HB indices. The proposed index has fairly linear behavior, without discontinuities with respect to increases of system load. It also has less computation load.     

A Predictive Correlation for Dynamic Viscosity of Fatty Acid Methyl Esters and Biodiesel

The viscosity of biodiesel, which is a mixture of fatty acid methyl esters (FAME), is an important physical property in the injection and efficient combustion. In this study, a simple correlation, with only one adjustable parameter, is proposed for predicting the viscosity of FAME and their mixtures (biodiesel) as a function of temperature. First, the adjustable parameter of the correlation is calculated for various FAME. The average absolute relative deviation (AARD) is obtained to be 0.97% for 226 data points. Second, the adjustable parameter of FAME is connected to the number of carbon atoms and the number of double bonds to build a predictive correlation for the calculation of viscosity. The AARD for 226 data points is obtained to be 2.28%. Third, the proposed model is employed to predict the viscosity of biodiesel without introducing any new adjustable parameter. To predict the viscosity of biodiesel, the average of the adjustable parameter is applied to the correlation. The AARD of 2.96% is obtained for 185 data points comprised of 23 different biodiesels. To better understand the ability of the correlation in the estimation of the viscosity of biodiesel and FAME, a comparison is made between the present correlation and a number of correlations available in the literature.     

Investigation of the electroactivity,conductivity, and morphology of poly(pyrrole‐co‐N‐alkyl pyrrole) prepared via electrochemical nanopolymerization and chemical polymerization

The copolymerization of pyrrole (Py) with N‐ethyl pyrrole, N‐butyl pyrrole, and N‐octyl pyrrole (NOPy) was carried out by electrochemical and chemical oxidation. In the electrochemical method, copolymer thin films with different feed ratios of monomers were synthesized by the cyclic voltammetry method in a lithium perchlorate (LiClO₄)/acetonitrile (CH₃CN) electrolyte on the surface of a glassy carbon working electrode. The deposition conditions on the glassy carbon, the influence of the molar ratios of the monomers on the formation of the copolymers, and the electroactivity of the copolymers were investigated with cyclic voltammetry. Nanoparticles made of a conjugate of the copolymers with different feed ratios of monomers were prepared by chemical polymerization (conventional and interfacial methods) in the presence of iron(III) chloride hexahydrate (FeCl₃·6H₂O) as the oxidant. Nanostructural copolymers with higher conductivities were synthesized by simple tuning of the preparation conditions in a two‐phase medium. Fourier transform infrared spectroscopy, scanning electron microscopy, and four‐probe conductivity measurement techniques were applied for the characterization of the obtained copolymers. The conductivity of the obtained copolymer by an interfacial method with chloroform as the organic phase was 20 times higher than the copolymer obtained via an interfacial method with toluene as the organic phase and 700 times higher than the copolymer prepared by the conventional method (for a molar ratio of 70 : 30 Py : NOPy). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Enumeration Order Equivalence in Rational Numbers

The enumeration of elements of c.e. sets in the theory of computability and computational complexity has already been investigated. However, the order of this enumeration has received less attention. The enumeration orders of elements of c.e. sets by means of Turing machines on natural numbers are investigated. In this paper, we consider the enumeration orders of elements of c.e. sets on rational numbers. We present enumeration order reducibility and enumeration order equivalence on rational numbers and propose some lemmas and theorems on these concepts. Also, we show that the theories here hold for Rc and we could repeat the same theories in this domain, in a same way.     

Electric Power Generation from Thermoelectric Cells Using a Solar Dish Concentrator

In this paper, design details, theoretical analysis, and outcomes of a preliminary experimental investigation on a concentrator thermoelectric generator (CTEG) utilizing solar thermal energy are presented. The designed CTEG system consisted of a parabolic dish collector with an aperture diameter of 1.8 m used to concentrate sunlight onto a copper receiver plate with 260 mm diameter. Four BiTe-based thermoelectric cells (TEC) installed on the receiver plate were used to convert the concentrated solar thermal energy directly into electric energy. A microchannel heat sink was used to remove waste heat from the TEC cold side, and a two-axis tracking system was used to track the sun continuously. Experimental tests were conducted on individual cells and on the overall CTEG system under different heating rates. Under maximum heat flux, a single TEC generator was able to produce 4.9 W for a temperature difference of 109°C, corresponding to 2.9% electrical efficiency. The overall CTEG system was able to produce electric power of up to 5.9 W for a 35°C temperature difference with a hot-side temperature of 68°C. The results of the investigation help to estimate the potential of the CTEG system and show concentrated thermoelectric generation to be one of the potential options for production of electric power from renewable energy sources.