HEAT TRANSFER IN A THIN LIQUID FILM IN THE PRESENCE OF AN ELECTRIC FIELD

Heat transfer enhancement in an evaporating thin liquid film utilizing a electric field under isothermal interfacial condition is presented. A new mathematical model subjected to van der Waals attractive forces, capillary pressure, and an electric field is developed to describe the heat transfer enhancement in the evaporating thin liquid film. The effect of the electrostatic field on the curvature of the thin film, evaporative flux, pressure gradient distribution, heat flux, and heat transfer coefficient in the thin film is presented. The results show that applying an electric field can enhance heat transfer in a thin liquid film significantly. In addition, utilizing electric fields on the evaporating film will be a way to expand the extended meniscus region to attain high heat transfer coefficients and high rates of heat flux.     

Performance of Wi-Max receiver in presence of DS-UWB system

The effect of UWB interference on a Wi-Max receiver has not been addressed in the literature. This effect is analysed and it is shown that for a realistic scenario a DS-UWB system interference will not have a destructive effect on the performance of a Wi-Max receiver.     

Goal-oriented error estimation and mesh adaptivity in 3d elastoplasticity problems

We propose a 3D adaptive method for plasticity problems based on goal-oriented error estimation, which computes the error with respect to a prescribed quantity of interest. It is a dual-based scheme which requires an adjoint problem. The computed element-wise errors at each load/displacement increment are utilized for the mesh adaptivity purpose. Mesh adaptivity procedure is performed based on refinement and coarsening by introducing hanging nodes in quadrilateral and hexahedral elements in 2d and 3d, respectively. Several numerical simulations are investigated and the results are compared with available analytical solutions, existing experimental data and results of mesh adaptivity based on other conventional error estimation methods.     

Fingerprinting Based Indoor Localization Considering the Dynamic Nature of Wi-Fi Signals

Current localization techniques in outdoors cannot work well in indoors. Wi-Fi fingerprinting technique is an emerging localization technique for indoor environments. However in this technique, the dynamic nature of WiFi signals affects the accuracy of the measurements. In this paper, we use affinity propagation clustering method to decrease the computation complexity in location estimation. Then, we use the least variance of Received Signal Strength (RSS) measured among Access Points (APs) in each cluster. Also we assign lower weights to altering APs for each point in a cluster, to represent the level of similarity to Test Point (TP) by considering the dynamic nature of signals in indoor environments. A method for updating the radio map and improving the results is then proposed to decrease the cost of constructing the radio map. Simulation results show that the proposed method has 22.5% improvement in average in localization results, considering one altering AP in the layout, compared to the case when only RSS subset sampling is considered for localization because of altering APs.

     

On Time-Frequency Resource Leasing in Cognitive Radio Networks

In this work, we introduce a new spectrum leasing based cognitive radio for OFDM-based primary/secondary networks. More precisely, we propose a new leasing scheme both in time and frequency domains in a network composed of a primary transmission and some secondary (cognitive) users forming a cooperative relay network. In the proposed scheme, the primary user decides to lease a part of its available resources (time and frequency) to a selected set of relays, with the aim of increasing its link reliability. The selected relays use a part of the leased resources for relaying the primary signal, and in counterpart, they are allowed to exploit the rest of the frame for their own data transmission. By defining appropriate cost functions, the proposed algorithm decides whether it is of advantage for the primary user to cooperate with the relay network or not. Moreover, if cooperation is advantageous for the primary network, the algorithm selects the optimal amount of the time-frequency resources (number of OFDM symbols and subcarriers) that are involved in the cooperation process. Simulation results show that by using the proposed relaying scheme, both primary and secondary (relay) networks can take advantage in terms of achievable data rates compared to classical leasing systems.     

Distributed cooperative target detection and localization in decentralized wireless sensor networks

In many network applications such as surveillance systems, it is crucial to detect the target and estimate its location. Distributed processing algorithms are capable of providing fast, secure, scalable and robust solutions. In this paper, we study the problem of target detection and localization in a wireless sensor network. Most of the current researches have focused on centralized algorithms and the works done on distributed algorithms usually need center assistance and practical issues such as communication link failure is not addressed in them. In this paper, we first propose a distributed consensus-based algorithm for target detection and then propose a distributed consensus-based localization algorithm. We assume that the target transmits a radio signal that is received in sensors equipped with limited computational and power resources. We consider the communication link failure and use the collaboration of sensor nodes to detect the presence of target. In the proposed target localization algorithm, sensor nodes estimate their distance toward the target using the received signal strength. In both the proposed algorithms, sensor nodes exchange information only with their neighbors and each makes an individual decision. We further prove the convergence of the proposed algorithms. Computer simulations confirm that the proposed algorithms are very fast and applicable in high-performance networks. We improve the localization accuracy at least by 25 % in terms of localization error compared with some recent algorithms.     

Quantum decoherence of Dirac fields in non-inertial frames beyond the single-mode approximation

The effects of Quantum decoherence on Dirac fields in an accelerated frame are studied beyond the single-mode approximation. The decoherence phenomena are investigated through the quantum channel approach using the amplitude damping channel and the dephasing one. The entanglement and purity are two distinct quantum features which are investigated. We have assumed that only the non-inertial observer experiences decoherence phenomena. The associated effects of the acceleration, damping rate, and dephasing rate are considered. It is found that acceleration and decoherence rates will decrease the degree of entanglement and purity. It turns out that beyond the single-mode approximation, the maximal entangled state cannot be achieved. Moreover, a comparison between the damping and dephasing processes is done which reveals the fact that damping effects on the entanglement are stronger than dephasing effects, whereas dephasing has stronger effects on the purity.     

Mixing of glass fibers with nylon 6,6

Nylon 6,6 is one of the toughest of the engineering thermoplastic resins. It is resistant to corrosion and chemicals, but has a limited capability due to low rigidity, strength and moisture adsorption. Glass fibers are very strong and rigid but susceptible to environmental attack. Proper mixing of these two materials would form a fiber composite with high strength, toughness, rigidity and stability at elevated temperatures. The main purpose of this work was to study the effect of properties of a fiber composite containing 20% loading of glass fibers in Nylon 6,6. Two different types of twin screw extruders, one a co-rotating and the other a counter-rotating, were used. Two different screw designs, a high-shear and a low-shear design, were used on each of these extruders. A statistical process study was developed using ECHIP. RPM of the screw and the output rate of the extruder were the identified variables in the process. Molded samples were evaluated for tensile, flexural, impact and heat deflection characteristics. Scanning Electron Microscopy study was also performed to evaluate the fiber distribution, length and wetting characteristics. The results were analyzed for all of the above properties and it was concluded that there was a great improvement in the properties of the reinforced material. Also, it was found that low RPM and output rates on the co-rotating twin-screw extruder would result in the best properties.     

Investigation of precursors concentration in spray solution on the optoelectronic properties of CuInSe2 thin films deposited by spray pyrolysis method

Copper indium selenide CuInSe₂(CISe) thin films were deposited by chemical spray pyrolysis (CSP) method of CuInS₂(CIS) and subsequent selenization process. To study the effects of solution concentration, we prepared different precursors solution of CIS including different amount of indium salts from 0.025 to 0.100 M with In/Cu 1.25 and S/In 4. These results propose that solution concentration is critical for inflecting the morphological, optical, electrical, and electrochemical characteristics of solution-processed CISe films and device performance. The studied morphological properties of deposited samples were homogenous, crack-free with large grains in indium salt concentrations more than 0.075 M. The deposited film thickness depends on the spray precursor concentration and increases for higher concentration. In addition with increasing of indium precursor concentration from 0.025 to 0.100 M in spray solution, the optical bandgap of deposited film decreases from 1.40 to 1.35 eV. Also the films mobility and carrier density were notably influenced by any change in the solution concentration. Electrical and electrochemical properties showed a decrease in carrier density from?~?10²⁰ to?~?10¹⁷ cm^?3 and the increase in mobility of order?~?10^–7 to?~?10^–2 cm²/V s, respectively, for 0.025 M, 0.100 M CISe films. All films exhibited p-type conductivity owing to different concentrations. However, it seems that the concentration of the ideal solution is 0.100 molars.

     

Prospects of nuclear power plants for sustainable energy development in Islamic Republic of Iran

This paper presents the feasible contributive share of electricity generation from each energy resources. This includes the economical feasibilities and all demographic projections involved in forecasting methodology, which explicitly reflect on overall national power demand projection in the Energy prospects of Islamic Republic of Iran till 2033. The Energy demand and reliability are presented with a view to elaborate on significant role and required capacity of Nuclear Power Plants (NPP) towards fulfillment of an energy mix policy in the country.