An Upper Bound on Air Interface Blocking Probability in Multiservice CDMA Networks

We propose a novel approach to derive an upper bound for the air interface blocking probability in a multiservice CDMA network with soft handoff (SHO) as a function of network load. This method requires only general assumptions made for network design and dimensioning. We obtain an approximated upper bound and compare it with the calculated values for the upper bound and with real network simulation results to show that our method with a reduced computational complexity is also accurate.     

Response of reinforced concrete structures to macrocell corrosion of reinforcements. Part II: After propagation of microcracks via a numerical approach

Investigation of response of reinforced concrete (RC) structures due to axisymmetric macrocell corrosion of rebars is of concern after propagation of microcracks within the concrete medium. The geometry, boundary and interfaces conditions of the present problem are identical to those stated in part I. As seen in the companion paper, the exact solution to the boundary value problem corresponding to the uncracked steel–rust–concrete composite was possible. After appearance of the microcracks the concrete behavior becomes nonlinear anisotropic with post-cracking softening, and the associated problem is analytically intractable. Therefore, it is proposed to employ a novel meshless method, namely gradient reproducing kernel particle (GRKPM), in the cylindrical coordinates. The analytical and numerical solutions pertinent to the uncracked concrete are in good agreement. Subsequently, the effects of the parameters associated with the mechanical behavior of concrete and properties of rust on the time of surface cracking, the maximum values of consumed rebar per unit area of anode and crack width openings at the time of surface cracking, and the maximum value of radial stress at the rust–concrete interface are scrutinized in some detail.     

A simulated annealing approach for the multi-periodic rail-car fleet sizing problem

In this paper, we proposed a new formulation and a solution procedure for optimizing the fleet size and freight car allocation wherein car demands and travel times are assumed to be deterministic and unmet demands are backordered. We assume that unmet demands become zero at the end of the planning horizon, i.e., the car demands are totally satisfied through the horizon. There are important interactions between decisions on sizing a rail car fleet and utilizing that fleet. Consequently, the optimum use of rail-cars for demands response in the length of the time periods is one of the main advantages of the proposed model. The model also provides rail network information such as yard capacity, unmet demands, and number of loaded and empty rail-car at any given time and location. Computational tests showed that small-size instances can be solved by the exact approach in a fair amount of CPU time, but it is not feasible for medium and large-size instances. To tackle this problem, a Simulated Annealing (SA) algorithm is proposed to solve the model. The algorithm works efficiently on a neighborhood search within solution space, acceptance probability, and inferior solutions to escape from trap (i.e., local optimal solution). Numerical examples are solved to check for the efficiency and validity of the SA algorithm.     

Modelling machine tool dynamics using a distributed parameter tool–holder joint interface

Increasing productivity in machining process demands high material removal rate in stable cutting conditions and depends strongly on dynamic properties of machine tool structure. Combined analytical–experimental procedures based on receptance coupling substructure analysis (RCSA) are employed to determine the stability of machine operating conditions at different tool configurations. The RCSA employs holder–spindle experimental mobility measurements in conjunction with an analytical model for the tool to predict the dynamics of different sets of tool and holder–spindle combinations without the need for repeated mobility measurements. In this paper an alternative approach using the concept of tool on resilient support is adopted to predict the machine tool dynamics in various tool configurations. In the proposed model the tool, represented by an analytical model, is partly resting on a resilient support provided by the holder–spindle assembly. The support dynamic flexibility is measured by performing vibration tests on the holder–spindle assembly. Tool–holder joint interface characteristics are included in the model by considering a distributed elastic interface layer between the holder–spindle and the tool shank part. The distributed interface layer takes into account the change in normal contact pressure along the joint interface and comparing with the lumped joint model used in RCSA it allows more detailed representation of the joint interface flexibility and damping which have crucial roles in machine dynamics. Experiments are conducted to demonstrate the efficiency of proposed model in prediction of milling operation dynamics and it is shown that the model is capable of accurately predicting the dynamic absorber effect of spindle in a tool tuning practice.     

The effect of nanoparticles on oil sludge biodegradation by Chromohalobacter sp. isolated from the Bahregan area in the Persian Gulf

In this study, sampling was performed from oil-sludge-contaminated site from Bahregan area in the Persian Gulf of Iran. Alkane-degrading bacteria from oil sludge were isolated by chemotaxis in hydroxylase gene. Thus, Chromohalobacter strain was selected as useful strain for the biodegradation of oil sludge. The biodegradation of oil sludge by Chromohalobacter in the absence and presence of nanoparticles in light and dark conditions was investigated by gas chromatography–mass spectrometry analysis. Results of analysis showed that although Chromohalobacter is capable of the biodegradation of oil sludge, Fe₂O₃ and Fe₃O₄ nanoparticles with this bacterium increase the biodegradation in a short time.     

Design and analysis of efficient QCA reversible adders

The Journal of Supercomputing - Quantum-dot cellular automata (QCA) as an emerging nanotechnology are envisioned to overcome the scaling and the heat dissipation issues of the current CMOS...     

Energy efficient hybrid full adder design for digital signal processing in nanoelectronics

Analog Integrated Circuits and Signal Processing - In recent years, there has been a growing interest in energy efficient VLSI designs for portable devices. Full adder cell is one of the most...     

Application of NOMA for cellular-connected UAVs:opportunities and challenges

Unmanned aerial vehicles (UAVs) have gained considerable interests in numerous civil applications.To push forward its potentials,cellular-connected UAVs have be...     

Novel single-trit comparator circuits in ternary quantum-dot cellular automata

Analog Integrated Circuits and Signal Processing - Today, with the continuation of the reduction of the dimensions of transistors, the thickness of the gate is so small that it causes the leakage...