Performance Analysis in Digital Circuits for Process Corner Variations,Slew-Rate and Load Capacitance

The aggressive scaling of CMOS technology has inevitably led to vastly increased power dissipation, process variability and reliability degradation, posing tremendous challenges to robust circuit design. To continue the success of integrated circuits, advanced design research must start in parallel with or even ahead of technology development. In this paper, an attempt is made to analyze various circuits’ delay and power performance by introducing certain level of variation to important process parameters like threshold voltage (V_th), mobility of carriers (μ₀), oxide thickness (t_ox) and doping concentration (n_sd). Basic Monte Carlo simulation is carried out on these circuits to ascertain the stability in performances. A 16 × 1 multiplexer is considered for detailed analysis. SPICE characterization is done for three different input slew rates (0.1, 0.5 and 1 ns) against four different output load drive strengths (1×, 2×, 3× and 4× output capacitive load). From the obtained results, output slew rates and average power results are observed and discussed.     

Synthesis and Characterization of Anti-fungus,Anti-corrosion and Self-cleaning Hybrid Nanocomposite Coatings Based on Sol–Gel Process

Anti-corrosion, anti-fungus, and self-cleaning properties of coatings containing ZnO–TiO₂, SiO₂–TiO₂ and SiO₂/TiO₂/ZnO nanoparticles synthesized based on sol–gel precursors using tetra methoxysilane, 3-glycidoxypropyl trimethoxysilane, tetra (n-butyl orthotitanate) and zinc acetate dihydrate were investigated by FESEM, EDAX and TEM analyses. Results indicated uniform dispersion of inorganic nanoparticles in the range of 20–40 nm in size. Anti-corrosion property of the hybrid coating was characterized by EIS measurements and parametrically analyzed in an equivalent circuit when the coating was exposed to salt solution. Results showed that, ZnO and TiO₂ nanoparticles enhance anti-corrosion property of the hybrid coatings. Anti-fungus and anti-bacterial properties of the coatings were determined by diameter of inhibition zone and inhabitation of bacterial growth, respectively. The coating containing ZnO and TiO₂ nanoparticles showed anti-fungus and anti-bacterial properties which were related to their photocatalytic properties. Degradation of methylene blue in aqueous solution was determined by UV–Visible tests which indicated self-cleaning property of the coatings containing ZnO and TiO₂ nanoparticles.     

Assessment of contaminant diffusivities in building materials from porosimetry tests

Recent studies have shown that surface and gaseous contaminant interactions may play an important role in indoor air quality. Modeling is an important tool to improve our knowledge about the phenomena involved and define appropriate ventilation strategies. However, data for sorption isotherms and diffusion in building materials remain woefully lacking. This paper deals with the latter point. It aims at investigating a methodology based on an analysis of the material porosity first and then the application of Carniglia's mathematical model to determine the effective diffusivity of gaseous species in building materials. This methodology, whose main principles are presented in the first part of the paper, was applied to seven commonly found materials. Mercury intrusion porosimetry (MIP) tests, and the calculations using Carniglia's model, reveal typical total porosities and tortuosity factors for these materials. The analysis of pore size distributions (PSDs) also draws one's attention to the possible differences in the pore structures that may exist between two samples of the same type of material and the differences in the effective diffusivities of contaminants that may result from them. The computed effective diffusivities were subsequently compared to data from experiments carried out in the frame of the EC project MATHIS. An agreement was obtained, thus validating Carniglia's methodology - a methodology that offers many practical advantages compared to diffusion-cell methods.     

Performance evaluation of co-located IEEE 802.15.4-based wireless body sensor networks

Wireless body sensor networks (WBSNs) are expected to play a pivotal role in health-related and well-being applications. In this paper, we consider a situation in which a large number of people wearing body sensor networks are gathered in very close vicinity (as can happen in sport events or emergency hospitals). Clearly, BSNs compete with each other to gain access to the same frequency which results in experiencing mutual (internal) interference. Therefore, we investigate the “internal interference” and its destructive impacts on the overall performance gain of WBSNs using IEEE 802.15.4 standard protocol. As the number of WBSNs increases in the channel, it becomes highly likely for active periods of neighbouring WBSNs to overlap with each other. The increase in overlapping active periods would increase the probability of packet collisions leading to performance degradation. In this paper, two types of interference mitigation strategies are proposed, namely passive schemes and active scheme. The terms passive and active refer to the absence and presence of the capability of communication between WBSNs to efficiently utilise the same frequency spectrum. According to the passive schemes, WBSNs are enabled to change their operating frequencies whenever required to mitigate the impacts of internal interference, whereas active scheme offers collaborative utilisation of the channel. The simulation results show that the proposed active scheme represents the highest performance gains compared to the proposed practical passive schemes.     

Investigating shrinkage and moisture diffusivity of melon seed in a microwave assisted thin layer fluidized bed dryer

This work aimed to investigate the drying behavior of melon seed during combined fluidized bed-microwave drying system. Three drying air temperatures (40, 55 and 70 °C), three microwave powers (270, 450 and 630 W) and three air velocities (0.8, 1.5 and 2.3 m/s) were tested. Five mathematical models were selected to fit the experimental data for drying kinetics, and the results revealed that the Aghbashloo et al. model exhibited, in all cases, the best performance in fitting the experimental data (R² varying from 0.99088 to 0.99998; χ² from 0.00000 to 0.00185 and RMSE from 0.02289 to 0.82316). Calculated values of moisture diffusivity for dried melon seed varied from a minimum of 6.51 × 10?10 to a maximum of 6.59 × 10?9 m²/s under the tested drying conditions. Moisture diffusivity values increased as air temperature and microwave power was increased. Shrinkage values were calculated and found to vary in the range from 46.99 to 15.09 %.     

Study on Hot Ring Compression Test of Nimonic 115 Superalloy Using Experimental Observations and 3D FEM Simulation

In hot forging of Nimonic 115, it is desirable to determine friction coefficients. Changing magnitudes of temperature and type of lubricant at the surface of the workpiece and dies influence friction coefficient. This paper describes an experimental investigation of friction under hot forging conditions using the ring compression test. The 3D FEM simulations were used to derive the friction calibration curves and to evaluate material deformation, geometric changes, and load-displacement results. A series of ring compression tests were carried out to obtain friction coefficients for a number of lubricants including mica plate, glass powder, graphite powder, and dry condition. The experiments show how the variations in temperature at the interface affected frictional behavior. On the basis of these results, mica is recommended for hot forging of Nimonic 115 and its friction coefficient is approximately 0.3.     

Effect of primary parameters on the performance of PEM fuel cell

A one-dimensional, steady-state and isothermal model for a proton exchange membrane (PEM) fuel cell has been developed to investigate the effects of various parameters such as the molar fraction of nitrogen gas, relative humidity, temperature, pressure, membrane thickness, anode and cathode stoichiometric flow ratio and the distribution of oxygen in the cathode catalyst while water transfer in membrane is produced by diffusion, pressure gradient and electro-osmotic drag. The most critical problems to overcome in the proton exchange membrane (PEM) fuel cell technology are the water and thermal management. The results show that the cell performance increases as operating pressure and temperature are increased. The performance of cell can decrease by decreasing the relative humidity of inlet gases and increasing the membrane thickness. Increasing the anode and cathode stoichiometric flow ratio can also improve the cell performance. As the oxygen concentration becomes zero in about 8 percent depth of cathode catalyst layer, the thickness of cathode catalyst layer can be reduced 92 percent without any potential loss in output voltage. The cathode activation loss also becomes high by increasing the molar fraction of nitrogen gas. The modeling results agree very well with experimental results.     

A variable neighbourhood search algorithm for the flexible job-shop scheduling problem

The flexible job-shop scheduling problem (FJSP) is a generalisation of the classical job-shop scheduling problem which allows an operation of each job to be executed by any machine out of a set of available machines. FJSP consists of two sub-problems which are assigning each operation to a machine out of a set of capable machines (routing sub-problem) and sequencing the assigned operations on the machines (sequencing sub-problem). This paper proposes a variable neighbourhood search (VNS) algorithm that solves the FJSP to minimise makespan. In the process of the presented algorithm, various neighbourhood structures related to assignment and sequencing problems are used for generating neighbouring solutions. To compare our algorithm with previous ones, an extensive computational study on 181 benchmark problems has been conducted. The results obtained from the presented algorithm are quite comparable to those obtained by the best-known algorithms for FJSP.