Outage analysis of selection diversity over Rayleigh fading channels with multiple co-channel interferers

In this paper an approach to the performance analysis of signal-to-interference (SIR) based selection combining (SC) operating over the Rayleigh fading channels experiencing an arbitrary number of multiple, Rayleigh co-channel interferers is presented. We have presented a general analysis of multibranch SC where each branch experiences an arbitrary number of multiple equal power co-channel interferers. Useful closed form expressions are derived for the probability density function (PDF) and cumulative distribution function (CDF) at the output of the combiner. Also an outage analysis is performed in order to show the effects of the number of multiple interferers, diversity order and input SIR unbalance to the system performances.     

Second‐Order Statistics of System with Microdiversity and Macrodiversity Reception in Gamma‐Shadowed Rician Fading Channels

In this letter, a wireless communication system with microdiversity and macrodiversity reception in gamma‐shadowed Rician fading channels is considered. Exact and rapidly converging infinite‐series expressions for the average level crossing rate and average fade duration at the output of the system are provided. Numerical results are presented graphically to illustrate the proposed mathematical analysis and to examine the effects of the system's parameters on the quantities considered.     

Maximum Likelihood Approach for RFID Tag Set Cardinality Estimation with Detection Errors

Estimation schemes of Radio Frequency IDentification (RFID) tag set cardinality are studied in this paper using Maximum Likelihood (ML) approach. We consider the estimation problem under the model of multiple independent reader sessions with detection errors due to unreliable radio communication links and/or collisions. In every reader session, both the detection error probability and the total number of tags are estimated. In particular, after the $R$ -th reader session, the number of tags detected in $j$ ( $j=1,2,...,R$ ) reader sessions out of $R$ sessions is updated, which we call observed evidence. Then, in order to maximize the likelihood function of the number of tags and the detection error probability given the observed evidences, we propose three different estimation methods depending on how to treat the discrete nature of the tag set cardinality. The performance of the proposed methods is evaluated under different system parameters and compared with that of the conventional method via computer simulations assuming flat Rayleigh fading environments and framed-slotted ALOHA based protocol.     

Antifungal efficiency of corona pretreated polyester and polyamide fabrics loaded with Ag nanoparticles

This study discusses the possibility of using the corona (electric discharge at atmospheric pressure) treatment for fiber surface activation that can facilitate the loading of Ag nanoparticles (NPs) from colloids onto the polyester and polyamide fabrics and thus enhance their antifungal activity against Candida albicans. The laundering durability of achieved effects and the influence of dyeing of fabrics with disperse dyes on their antifungal efficiency were studied. The morphology of fibers loaded with Ag nanoparticles was characterized by SEM whereas X-ray photoelectron spectroscopy was used for the evaluation of surface chemical changes. Corona pretreated polyester and polyamide fabrics loaded with Ag nanoparticles showed better antifungal properties compared to untreated fabrics. The advantage of corona treated fabrics became even more prominent after washing test, particularly for polyester fabrics. Antifungal efficiency of polyester and polyamide fabrics loaded with Ag nanoparticles were almost unaffected by dyeing process.     

Optimal closed-loop control of a hybrid step motor with chopper drive

Optimal closed-loop control of a hybrid step motor control with chopper drive is described. Expressions for the average torque and optimal control angle giving maximal average torque in the stationary state without phase current chopper control are presented. The effects of chopper current control on the torque and acceleration characteristics of a hybrid step motor are discussed. Expression have been developed for the control angle in the chopper current control mode, yielding greater torques and improved acceleration of hybrid step motors than for the optimal control angle without phase current control. The speed response of a hybrid step motor operated in a closed-loop system has been studied by computer simulation for different supply voltages and torque loads, using various control angle algorithms.     

Development of residual strength evaluation tool based on stress-strain approximation

To allow for a safe design of metallic structures, it must be considered that, as a result of the manufacturing and processing operations, cracks or flaws below the NDI (Non-Destructive Inspection) detectability level always exist in the component after inspection. Further problems originate from the defect geometry. Failure of engineering structural components and structures have been mostly traced to surface cracks. Especially for a surface crack containing structure that is thin, the limit collapse of a ligament is usually the main cause of structure rupture. Study of the evaluation procedure relating to the limit load of the surface crack ligament is, therefore, an important project for conventional fracture assessment, particularly for pressure vessel (LBB) assessment. For this purpose, novel more accurate residual strength prediction method based on the Elasto-Plastic Fracture Mechanics (EPFM) has been developed and tested. Laboratory tests on tensile plate specimens with surface cracks were performed considering two different materials. In the final part of the work, effort was directed toward the verification and justification of selected analytical methods by adequate component testing. The most significant results of this work deal with residual strength evaluation for the thin wall pressure containing components. The important finding is that there is a potential for improvement in comparison to the current methods that may be used to increase payoff of the lightweight structures. The presented very robust analysis method and the useful structure integrity evaluation procedure should significantly contribute to the state-of-the-art structure optimisation and being applied to the design of the light-weight structures should ease the effort of the structure engineer to develop the successful and reliable hardware and to keep in place with advancing technologies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Automated retrofit targeting of heat exchanger networks

The aim of this paper is to develop a novel heat exchanger network (HEN) retrofit method based on a new automated retrofit targeting (ART) algorithm. ART uses the heat surplus-deficit table (HSDT) in combination with the Bridge Retrofit concepts to generate retrofit bridges option, from which a retrofit design may be formulated. The HSDT is a tabular tool that shows potential for improved re-integration of heat source and sink streams within a HEN. Using the HSDT, retrofit bridges—a set of modifications that links a cooler to a heater to save energy—may be identified, quantified, and compared. The novel retrofit method including the ART algorithm has been successfully implemented in Microsoft ExcelTM to enable analysis of large-scale HENs. A refinery case study with 27 streams and 46 existing heat exchangers demonstrated the retrofit method’s potential. For the case study, the ART algorithm found 68903 feasible unique retrofit opportunities with a minimum 400 kW·unit^–1 threshold for heat recovery divided by the number of new units. The most promising retrofit project required 3 new heat exchanger units to achieve a heat savings of 4.24 MW with a favorable annualised profit and a reasonable payback period.

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Spatial targeting evaluation of energy and environmental performance of waste-to-energy processing

Waste-to-energy supply chains are important potential contributors to minimising the environmental impacts of municipal solid waste by reducing the amounts of waste sent to landfill, as well as the fossil fuel consumption and environmental footprints. Accounting for the spatial and transport properties of the waste-to-energy supply chains is crucial for understanding the problem and improving the supply chain designs. The most significant challenge is the distributed nature of the waste generation and the household energy demands. The current work proposes concepts and a procedure for targeting the size of the municipal solid waste collection zone as the first step in the waste-to-energy supply chains synthesis. The formulated concepts and the provided case study reveal trends of reducing the net greenhouse gas savings and energy recovery by increasing the collection zone size. Population density has a positive correlation with the greenhouse gas saving and energy recovery performance. For smaller zone size the energy recovery from waste approaches and in some cases may surpass the energy spent on waste transportation. The energy recovery and greenhouse gas savings remain significant even for collection zones as large as 200 km². The obtained trends are discussed and key directions for future work are proposed.

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Synthetic Biology and Tissue Engineering: Toward Fabrication of Complex and Smart Cellular Constructs

Tissue engineering approaches, with the goals of replacing or recovering damaged or diseased tissues, or of reconstituting tissues in vitro for disease modeling and drug development, have the potential to make significant contributions to medicine. Advances in stem cell biology, biomaterial synthesis and characterization, and microscale technologies have made engineered tissues a reality. However, the classic tools used to build tissues in the lab do not allow for complete control of cell behaviors. More recently, synthetic biology principles have developed robust and versatile approaches to program cells with artificial genetic circuits, where cell behavior and function can be manipulated. At the interface between synthetic biology and tissue engineering, there is space for a new area of investigation where material engineering and cellular engineering complement and sustain each other. In this progress report, synthetic biology principles and how they have been used to engineer cells with potential to dictate cell behavior and function in tissue constructs of the future are briefly described. It is believed that this research area still needs further exploration to fully exploit synthetic biology to make smart and functional cellular constructs for therapeutic and in vitro applications.