Sonar-Based Rover Navigation for Single or Multiple Platforms: Forward Safe Path and Target Switching Approach

In this paper, we have proposed a sensor fusion scheme along with the geometrical modeling of mobile robot navigation path in an unknown environment. In this scheme, the physical placement of sonars, their ranging limits and beam opening angles are considered. A simple 2-D axis transformation is proposed to relate local robot frame with the actual navigation environment. forward safe path (FSP) and target switching approach (TSA) are proposed for efficient obstacle avoidance and target tracking of mobile robot. FSP greatly simplifies the environment conditions as sensed by the robot and also provides minimum turning path during avoidance of obstacles. This method also removes the ldquooscillationrdquo in the mobile robot navigation path. TSA technique gives highest priority on the target tracking during the obstacle avoidance and seeks minimum distance path towards the target. These methods remove unnecessary turning of mobile robot during navigation. A scheme for target directional motion is also proposed. So, mobile robot takes the minimum turning path required towards the target. These methods also ensure the avoidance of ldquodead cycle problemrdquo. These schemes are successfully implemented on a model of PatrolBot mobile robot from ActivMedia Robotics. The overview of current research work on multi-domain robotic system namely system-of-systems is also presented. This paper also describes the Global Positioning System-based navigation of rovers. Results of real-time experiments with Pioneer II P2AT-8 from ActivMedia are included in this paper to show the future aspect of this research work.     

Performance analysis of low average reporting bits cognitive radio schemes in bandwidth constraint control channels

Collaborative spectrum sensing is regarded as a key technology for tackling the challenges of the practical implementation of cognitive radio (CR). However, most of the proposed solutions require infinite bits or several bits exchanging per each CR to make the final decision to indicate the absence or presence of a primary user. It is well known that if N CRs employ energy detector with the same threshold and then send individual decision bits to a fusion centre, the OR-rule (1-out-of-N rule) will be optimal under Neyman-Pearson criterion. To decrease the average number of exchanging bits, we propose novel schemes while they perform as well as the OR-rule, our analytical and simulation results show that the proposed schemes has two important advantages over previously proposed schemes: (1) the average number of exchanging bits for N CRs always is 1/N bits per CR in perfect control channels; however, it is much higher than 1/N for the other proposed methods, e.g. it is 1 bit for the OR-rule and (2) the proposed method is very robust against the errors of imperfect control channels, specially, in low signal-to-noise ratio (SNR) regimes. Furthermore, the average number of reporting bits do not change considerably under the imperfect control channels.     

Correlation between water permeability of latex-modified concrete (LMC) and water diffusion coefficient of latex film

Cement-based materials are generally known as weak materials in flexure and tension in comparison with compression. Polymers are used in cement-based materials to improve their flexural and tensile behaviors. The composite is called as polymer-modified concrete/mortar. Furthermore, polymers decrease permeability of water into cementitious matrices. Polymers are usually used as admixtures in concretes in form of latexes. Latexes are water-based polymers, which are consistent with water-based concrete matrices. On this basis, these kinds of products are called latex-modified concretes (LMCs). However, it has been found that chemical composition, particle size distribution, molecular weight, physical/mechanical properties of latexes affect performance of modified concretes. In this investigation, six latexes in three categories (acrylic, SBR and polyvinyl acetate) were used as concrete admixtures. They were characterized for chemical composition (by FTIR analysis), minimum film formation temperature, pH, glass transition temperature (T _g), particle size and particle size distribution to evaluate the effect of each property on LMC performance. Due to the formation of latex film in the microcracks and pores of concrete microstructure, it was suggested that diffusion of water into films controls permeability of whole concrete structures. On this basis, the diffusion coefficient of the latex films subjected to water was measured using a new method (continuous FTIR analysis). Capillary water absorption test was performed on concrete specimens to verify validity of the suggestion. It was found that there is a correlation between capillary water absorption of LMCs and water diffusion coefficient of latex films.     

Experimental Investigation of Pulsating Heat Pipes and a Proposed Correlation

Pulsating heat pipes are complex heat transfer devices, and their optimum thermal performance is largely dependent on different parameters. In this paper, in order to investigate these parameters, first a closed-loop pulsating heat pipe (CLPHP) was designed and manufactured. The CLPHP was made of copper tubes with internal diameters of 1.8 mm. The lengths of the evaporator, adiabatic, and condenser sections were 60, 150, and 60 mm, respectively. Afterward, the effect of various parameters, including the working fluid (water and ethanol), the volumetric filling ratio (30%, 40%, 50%, 70%, 80%), and the input heat power (5 to 70 W), on the thermal performance of the CLPHP was investigated experimentally. The results showed that the manufactured CLPHP has the best thermal performance for water and ethanol as working fluids when the corresponding filling ratios are 40% and 50%, respectively. Finally, with the available experimental data set of CLPHPs, a power-law correlation based on dimensionless groups was established to predict their input heat flux. Compared with the experimental data, the root-mean-square deviation of the correlation prediction was 19.7%, and 88.6% of the deviations were within ± 30%.     

A novel arterial Wick for gas–liquid phase separation

Gas–liquid phase separation under microgravity conditions or in small-scale fluidic systems represents a challenge for two-phase liquid-continuous systems. In this study, capillary channels formed by 3-mm diameter stretched stainless-steel springs coated with a commercial superhydrophobic coating are used to remove air bubbles from water. A single channel is capable of absorbing a stream of 3.7-mm diameter bubbles impinging on a small area of the channel at a rate of over 50 bubbles/s. High-permeability walls lead to fast individual absorption events (4 ms for 2.5-mm bubbles) where bubble collapse time is limited by the inertia of the surrounding liquid. A horizontal three-channel array has been shown capable of absorbing impinging bubbles from a sparger at superficial gas velocities of 0.03 m/s. The ultimate capacity of the 3-mm diameter channel is predicted to be much higher than what could be measured with the existing apparatus. © 2018 American Institute of Chemical Engineers AIChE J, 65: 1340–1354, 2019     

Optimal distribution function determination for plus fraction splitting

Reservoir fluid modelling is one of the most important steps in reservoir simulation and modelling of flow lines as well as surface facilities. One of the most uncertain parameters of the reservoir fluids is the plus fraction. An accurate and consistent splitting scheme can reduce this uncertainty and as a result, enhance the modelling of reservoir fluids. The existing schemes for splitting plus fractions are all based on assuming a specific mole fraction‐molecular weight distribution with predefined constant values that may yield inaccurate and inconsistent results. In this study, an optimization‐based algorithm was developed to determine the aforementioned controlling parameters of the plus fraction distribution function, enforcing the relationship between specific gravity and molecular weight of the single carbon numbers (SCNs). The introduced optimization‐based splitting technique was applied to different samples, covering a wide range of reservoir fluids, including gas condensates, volatile oils, black oils, and heavy oils. The results showed that the proposed technique yielded a more consistent molecular weight‐mole fraction distribution concerning the experimental extended analysis of plus fractions, yielding an average relative error of 25.8 % compared to 76, 33.6, and 45.9 % for the Katz, Ahmed, and Whitson methods, respectively. It was also shown that the proposed method results in more accurate and more consistent phase behaviour predictions than the existing methods concerning the experimental data. Furthermore, the results showed that the introduced optimization‐based method yields monotonic split samples regarding specific gravity and molecular weight, while the conventional techniques do not guarantee to preserve the monotonicity.     

Origins and minimization of intermodulation distortion in a pseudo-differential CMOS beamforming receiver

Analog Integrated Circuits and Signal Processing - This paper studies how nonlinear distortion is generated in the combination of an inverter-based low-noise amplifier and a passive mixer. The...     

Effect of EPS beads in lightening a typical zeolite and cement-treated sand

Bulletin of Engineering Geology and the Environment - The current study aims to assess the influence of EPS beads inclusion on the strength properties of stabilized poorly-graded sands. Various...