Joint optimisation of transmission and waiting times in cognitive radio

Transmission time optimisation is one of the key considerations of cognitive network design. There are many studies in cognitive radio networks (CRNs) focusing on finding the best transmission time for secondary users (SUs) to maximise transmission or energy efficiency. While longer sensing duration leads to a higher sensing accuracy and causes less interference, the SU spends less time for transmission and more energy on sensing spectrum. On the other hand, when the transmission duration becomes longer, although the SU has more opportunities to access the channel, it may encounter higher interference due to primary user (PU) returns and the probability of collision becomes higher. In this article, in a decentralised slotted protocol for CRN, the SU spectrum access is proved as a renewal process, then the interference due to PU return during SU transmission, the missed opportunities due to waiting for the channel to become idle and the energy consumed by the SU in the whole spectrum access process including idling energy, transmission energy and sensing energy consumption are formulated and integrated into newly defined efficiency to obtain the optimum transmission time and waiting time.     

Deforestation in the Miombo woodlands: a pixel-based semi-automated change detection method

Most methods of change detection require a considerable amount of effort and expertise. The procedures of change detection are visual-, classification-, object- or vector-based. The target of this research was to develop an automated and generally unsupervised combination of methods to quantify deforestation on a per pixel basis. The study area was the Gutu district in Zimbabwe. In the first step, Landsat Thematic Mapper (TM) scenes were spectrally unmixed by the Spectral Mixture Analysis (SMA). The calculation of the necessary endmembers was performed by means of the N-FINDR algorithm. After the unmixing process, the data were analysed with change vector analysis (CVA) utilizing spherical statistics. Thereafter, a combination of constraints, including a Bayesian threshold and spherical angles, was applied to identify deforestation. The combination of these methods provided an accurate idea of the state of deforestation and enabled attribution to ‘fire-induced’ and ‘non fire-induced’ classes.     

Nanocrystalline-diamond thin films with high pH and penicillin sensitivity prepared on a capacitive Si-SiO2 structure

A capacitive field-effect EDIS (electrolyte-diamond-insulator-semiconductor) sensor with improved pH and penicillin sensitivity has been realised using a nanocrystalline-diamond (NCD) film as sensitive gate material. The NCD growth process on SiO₂ as well as an additional surface treatment in oxidising medium have been optimised to provide high pH-sensitive, non-porous O-terminated films without damage of the underlying SiO₂ layer. The surface morphology of O-terminated NCD thin films and the layer structure of EDIS sensors have been studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. To establish the relative coverage of the surface functional groups generated by the oxidation of NCD surfaces, X-ray photoelectron spectroscopy analysis was carried out. The hydrophilicity of NCD thin films has been studied by water contact-angle measurements. A nearly Nernstian pH sensitivity of 54-57 mV/pH has been observed for O-terminated NCD films treated in an oxidising boiling mixture for 80 min and in oxygen plasma. The high pH-sensitive properties of O-terminated NCD have been used to develop an EDIS-based penicillin biosensor. A freshly prepared penicillin biosensor possesses a high sensitivity of 85 mV/decade in the concentration range of 0.1-2.5 mM penicillin G. The lower detection limit is 5 μM.     

Single and bulk compressions of soft granules: Experimental study and DEM evaluation

The characterisation of mechanical properties of particulate solids (e.g. yield pressure and failure strength) is often done by an analysis of bulk compression. However, the relationship between bulk compression behaviour and the physical and mechanical parameters of single particles is not well understood. In this paper the deformation and failure behaviour of soft synthetic detergent granules is investigated experimentally using single granule and bulk compression analyses. Furthermore, the bulk compression of soft spheres, with the properties, which are the same as those of single granules used here, is simulated by distinct element method (DEM) and the predictions are compared with the experimental results. Both the experimental and simulation analyses are for a range of low pressures, less than 30 kPa, with the aim of characterising the yield pressure (limiting contact pressure) of the individual granules using the bulk compression models of Heckel, Kawakita and Lüdde and Adams and co-workers. It is shown that the ratio of the yield pressure of single granules to the Heckel parameter for this type of granules is less than one, and is about 0.5. Furthermore, a relationship is developed among the above three models of bulk compression, in which the above ratio is related to parameters such as the inter-particle and particle wall friction coefficients, initial porosity of the bed and lateral to axial pressure ratio of the particles in the bed. Therefore the use of bulk compression method to infer single particle properties should be made with great caution.     

Electrospray modeling of highly viscous and non‐Newtonian liquids

The electrohydrodynamic spraying of highly viscous and non‐Newtonian aqueous solutions of sodium alginate were experimentally modeled with high direct‐current electric fields. A prototype electrospray setup comprising a nozzle connected to a high‐voltage counter electrode connected to earth and a curing facility to solidify the droplets was used. The main aim was initially set to extend the knowledge of the electrospray to highly viscous liquids, where shear thinning was the main rheological feature of fluid flow through the nozzle of the spray system. To model the process, the effects on the size of beads of the electric field strength, nozzle diameter, flow rate, and the material properties of density, viscosity, surface tension, and electrical conductivity were characterized. The size distribution of the beads was obtained after the droplets were cured in a calcium chloride solution with an image analyzer system. The rheological study, carried out on different concentrations of alginate solution (i.e., 1–3 w/v %), showed a significant reduction in the viscosity as a function of the shear rate. Considering the shear‐thinning behavior of the solutions, in the modeling we applied the viscosity at the operational shear rate in the nozzle. Four dimensionless groups were introduced to obtain the relationship between the dimensionless group representing diameter and the other groups in the dripping and jet modes with statistical analysis of the experimental data. The proposed equations correlated the size of beads within ±10% deviations as compared to the experimental results. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Performance analysis of lognormally shadowed generalized Gamma fading channels

A new composite channel model is proposed for the performance analysis of shadowed fading channels. This model is represented as a mixture of generalized Gamma (GG) multipath fading and lognormal shadowing. GG distribution includes the Rayleigh, Nakagami, and Weibull as special cases; hence the presented model, which is referred to as GG‐L, is a generic model that covers many well‐known composite fading models, including the Rayleigh–lognormal (R‐L), Nakagami–lognormal (N‐L), and Weibull–lognormal (W‐L). The main drawback of the lognormal‐based composite models is that the composite probability density function (PDF) is not in closed form, thereby making the performance evaluation of communication links in these channels cumbersome. To bypass this problem, an approximation method is developed which makes it possible to derive a closed‐form, analytical expression for GG‐L composite distribution. The proposed method only needs the mean and the variance of the underlying lognormal distribution, and hence, bypasses the required complicated integration needed to calculate the PDF of the received signal envelope in GG‐L channel. Based on this method, the most statistical characteristics, such as cumulative density function (CDF) and moments of the GG‐L composite distribution, are derived and used for the performance analysis of a single receiver operating over GG‐L fading channel. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of Molybdenum on Metallurgical and Wear Properties of Fe–Cr–C Hard facing alloy

Protection of Metals and Physical Chemistry of Surfaces - In this research, Surface hardening was performed by two types of Flux Cored Arc Welding (FCAW) filler metals based on Fe–Cr–C...     

Optical Imaging Approaches to Monitor Static and Dynamic Cell‐on‐Chip Platforms: A Tutorial Review

Miniaturized laboratories on chip platforms play an important role in handling life sciences studies. The platforms may contain static or dynamic biological cells. Examples are a fixed medium of an organ‐on‐a‐chip and individual cells moving in a microfluidic channel, respectively. Due to feasibility of control or investigation and ethical implications of live targets, both static and dynamic cell‐on‐chip platforms promise various applications in biology. To extract necessary information from the experiments, the demand for direct monitoring is rapidly increasing. Among different microscopy methods, optical imaging is a straightforward choice. Considering light interaction with biological agents, imaging signals may be generated as a result of scattering or emission effects from a sample. Thus, optical imaging techniques could be categorized into scattering‐based and emission‐based techniques. In this review, various optical imaging approaches used in monitoring static and dynamic platforms are introduced along with their optical systems, advantages, challenges, and applications. This review may help biologists to find a suitable imaging technique for different cell‐on‐chip studies and might also be useful for the people who are going to develop optical imaging systems in life sciences studies.     

Microstructures and Grain Refinement of Additive-Manufactured Ti-xW Alloys

Metallurgical and Materials Transactions A - It is necessary to better understand the composition–processing–microstructure relationships that exist for materials produced by additive...     

Role of splenectomy in human liver transplantation under modern-day immunosuppression

Between January 1987 and October 1991, 1466 patients underwent consecutive Orthotopic Liver Transplantation (OLTx) at the University of Pittsburgh. Forty of these patient's had concomitant splenectomy with OLTx. These patients were compared to 147 randomly selected OLTx patients without splenectomy within the same time period. One-year patient and graft survival (PS and GS) were lower in splenectomized (Splx) patients compared to nonsplenectomized (non-Splx) patients (59% vs 86% PS, 55% vs 80% GS, respectively). One-month and one-year patient mortality in the Splx group was higher than in the non-splx patients (20% vs 3.4%, P < 0.001 for one month; 40% vs 14.3%, P = 0.003 for one year, respectively). One-month and one-year sepsis-related mortality was also high in Splx patients (17.5% vs 2.7%, P = 0.0022, for one month, and 30% vs 11.5%, P = 0.0043, for one year, respectively). We conclude that concomitant splenectomy with OLTx has a significantly higher patient mortality mainly due to its septic complications and, at present, unless there is a specific indication for a splenectomy, the routine addition of this procedure to liver allograft surgery would not be recommended.