Preparation of Sb:SnO2 thin films and its effect on opto-electrical properties

The present study focuses on pure and antimony (Sb)-doped tin oxide thin film and its influence on their structural, optical, and electrical properties. Both undoped and Sb-doped SnO₂ thin films have been grown by using simple, inexpensive pyrolysis spray technique. The deposition temperature was optimized to 450 °C. X-ray diffractions pattern have revealed that the films are polycrystalline and have tetragonal rutile-type crystal structure. Undoped SnO₂ films grow along (110) preferred orientation, while the Sb-doped SnO₂ films grow along (200) direction. The size of Sb-doped tin oxide crystals changes from 26.3 to 58.0 nm when dopant concentration is changed from 5 to 25 wt%. The transmission spectra revealed that all the samples are transparent in the visible region, and the optical bandgap varies between 3.92 and 3.98 eV. SEM analysis shows that the surface morphology and grain size are affected by the doping rate. All the films exhibit a high transmittance in the visible region and show a sharp fundamental absorption edge at about 0.38–0.40 nm. The maximum electrical conductivity of 362.5 S/cm was obtained for the film doped with 5 wt% Sb. However, the carrier concentration is increased from 0.708?×?10¹⁸ to 4.058?×?10²⁰ cm³. The electrical study reveals that the films have n-type electrical conductivity and depend on Sb concentration. We observed a decrease in sheet resistance and resistivity with the increase in Sb dopant concentration. For the dopant concentration of 5 wt% of Sb in SnO₂, the Rs and ρ were found minimum with the values of 88.55 (Ω cm^?2) and 2.75 (Ω cm), respectively. We observed an increase in carrier concentration and a decrease in mobility with the addition of Sb up to 25 wt%. The highest figure of merit values 2.5?×?10^–3 Ω^?1 is obtained for the 5wt% Sb, which may be considered potential materials for solar cells' transparent windows.

     

Structure and formation of shot coke — a microscopy study

A series of shot cokes and sponge cokes from industrial delayed cokers was examined by scanning electron micrsocopy (SEM) and optical micrscopy (OM) of external, fractured internal and polished surfaces. Calcined cokes were etched with chromic acid solution and etching behaviour related to the optical texture of the cokes. The shot coke spheres have an inner structure of fine-grained mosaic and a smooth external skin, 50m thick, of coarse-grained mosaic and small domains. Sponge cokes can be heterogeneous with inclusions of well-ordered carbon within the matrix mosaics. It is considered that the feedstock leading to shot coke in the delayed coker forms a high viscosity fused pitch/ mesophase system which is subject to significant disturbance by volatile evolution. The paste-like system breaks up into fragments as a result of deep agitation by volatile release and movement through the system. The viscosity of the fragments is too high to permit their coalescence and reform a continuous system. Instead, they remain as fragments >1.0m diameter. Structure of cokes from delayed cokers and the associated manipulation of the system by the volatile evolution within the coker. These two factors are inter-related. Differences between cokes arise from differences between viscosities of the mesophase from the feedstock and control the balance between fragmentation and re-coalescence of the charge, as a result of manipulation by volatile release, leading to the two extremes of shot and needle coke.     

Prevalence and profile of renovascular disease in type II diabetic patients with severe hypertension

The aim of this study was to determine the prevalence and profile of renal artery stenosis (RAS) in NIDDM population with severe hypertension. 60 consecutive NIDDM with severe HT (> or = 3 hypotensive drugs), 42 F/18 M (SR: 2.8), mean age: 66.6 +/- 6.5 years, diabetes duration: 14.1 +/- 6 years have had metabolic, ABPM and renal investigations: color duplex scan (CDS) (with renal us): n = 60, and/or arteriography: n = 17). 13 (21.5%) renal artery stenosis > or = 70%: 8 unilateral/5 bilateral were proved by arteriography. We compared classic HT (n = 47) versus renovascular HT (n = 13). There was no difference for age (years): 64.8 +/- 8 versus 70.6 +/- 6.4, HT duration (years): 11.6 +/- 6.8 versus 12.3 +/- 6. B.M.I.: 31.5 +/- 6 versus 27.6 +/- 3.3, HBA1C (%): 8.9 +/- 2.2 versus 8.8 +/- 0.9, cholesterol (mmol/L): 5.7 +/- 1.3 versus 5.5 +/- 0.6. Significant difference (p < 0.05) was noticed for S.R. (F/M): 2.9 versus 1.16, diabetes duration (years): 11.7 +/- 5 versus 16.5 +/- 8, frequency of retinopathy (%): 30 versus 61, smoking (%): 10 versus 40, triglycerides (mmol/L): 1.9 +/- 1.1 versus 2.6 +/- 1.1, and (p < 0.01) for blood pressure level (mmHg) (SBP: 142 +/- 20 vs 155 +/- 7, DBP: 81 +/- 13 vs 87 +/- 10, MBP: 103 +/- 16 vs 111 +/- 6), frequency (%) of HT escape (> or = 140/SBP, > or = 90/DBP) on ABPM: 40 versus 75 and 24 versus 40, insulin requirence (%): 36 versus 69, macroangiopathy (%): 51 versus 100 (coronaropathy: 34 vs 61, legs arteritis: 21 vs 69, carotid stenosis: 17 vs 30) and for renal function: frequency (%) of micro-macroalbuminuria: 36 versus 92 creatinaemia (mmol/L): 80 +/- 24 versus 124 +/- 44, creatinaemia clearance (mmL/min): 65 +/- 30 versus 40 +/- 12 while are found 5 renal insufficiencies (> or = 120 mmol/L). In NIDDM population with severe HT, renovascular HT is frequent (21.5%), and RAS must be evocated in unstable HT and/or renal injury with macro angiopathy, old NIDDM (> 15 years), requiring insulin. Colour duplex scan (+ renal US) mays lead to arteriography to confirm renal artery stenosis.     

A secure fog-based platform for SCADA-based IoT critical infrastructure

The rapid proliferation of Internet of things (IoT) devices, such as smart meters and water valves, into industrial critical infrastructures and control systems has put stringent performance and scalability requirements on modern Supervisory Control and Data Acquisition (SCADA) systems. While cloud computing has enabled modern SCADA systems to cope with the increasing amount of data generated by sensors, actuators, and control devices, there has been a growing interest recently to deploy edge data centers in fog architectures to secure low-latency and enhanced security for mission-critical data. However, fog security and privacy for SCADA-based IoT critical infrastructures remains an under-researched area. To address this challenge, this contribution proposes a novel security “toolbox” to reinforce the integrity, security, and privacy of SCADA-based IoT critical infrastructure at the fog layer. The toolbox incorporates a key feature: a cryptographic-based access approach to the cloud services using identity-based cryptography and signature schemes at the fog layer. We present the implementation details of a prototype for our proposed secure fog-based platform and provide performance evaluation results to demonstrate the appropriateness of the proposed platform in a real-world scenario. These results can pave the way toward the development of a more secure and trusted SCADA-based IoT critical infrastructure, which is essential to counter cyber threats against next-generation critical infrastructure and industrial control systems. The results from the experiments demonstrate a superior performance of the secure fog-based platform, which is around 2.8 seconds when adding five virtual machines (VMs), 3.2 seconds when adding 10 VMs, and 112 seconds when adding 1000 VMs, compared to the multilevel user access control platform.     

Optimal Robust Control for Unstable Delay System

Proportional-Integral-Derivative control system has been widely used in industrial applications. For uncertain and unstable systems, tuning controller parameters to satisfy the process requirements is very challenging. In general, the whole system’s performance strongly depends on the controller’s efficiency and hence the tuning process plays a key role in the system’s response. This paper presents a robust optimal Proportional-Integral-Derivative controller design methodology for the control of unstable delay system with parametric uncertainty using a combination of Kharitonov theorem and genetic algorithm optimization based approaches. In this study, the Generalized Kharitonov Theorem (GKT) for quasi-polynomials is employed for the purpose of designing a robust controller that can simultaneously stabilize a given unstable second-order interval plant family with time delay. Using a constructive procedure based on the Hermite-Biehler theorem, we obtain all the Proportional-Integral-Derivative gains that stabilize the uncertain and unstable second-order delay system. Genetic Algorithms (GAs) are utilized to optimize the three parameters of the PID controllers and the three parameters of the system which provide the best control that makes the system robust stable under uncertainties. Specifically, the method uses genetic algorithms to determine the optimum parameters by minimizing the integral of time-weighted absolute error ITAE, the Integral-Square-Error ISE, the integral of absolute error IAE and the integral of time-weighted Square-Error ITSE. The validity and relatively effortless application of presented theoretical concepts are demonstrated through a computation and simulation example.     

An evidential fusion approach for activity recognition in ambient intelligence environments

With the growing emergence of ambient intelligence, ubiquitous computing, sensor networks and wireless networking technologies, “ubiquitous networked robotics” is becoming an active research domain of intelligent autonomous systems. It targets new innovative applications in which robotic systems will become part of these networks of artifacts to provide novel capabilities and various assistive services anywhere and anytime, such as healthcare and monitoring services for elderly in Ambient Assisted Living (AAL) environments. Situation recognition, in general, and activity recognition, in particular, provide an added value on the contextual information that can help the ubiquitous networked robot to autonomously provide the best service that meet the needs of the elderly. Dempster–Shafer theory of evidence and its derivatives are an efficient tool to handle uncertainty and incompleteness in smart homes and ubiquitous computing environments. However, their combination rules yield counter-intuitive results in high conflicting activities. In this paper, we propose a new approach to support conflict resolution in activity recognition in AAL environments. This approach is based on a new mapping for conflict evidential fusion to increase the efficiency and accuracy of activity recognition. It gives intuitive interpretation for combining multiple sources in all conflicting situations. The proposed approach, evaluated on a real world smart home dataset, achieves 78% of accuracy in activity recognition. The obtained results outperform those obtained with the existing combination rules.     

Retracted and replaced: Enabling technologies for the ‘always best connected’ concept

This article has been retracted and replaced. Retraction notice DOI: 10.1002/wcm.426 ‘Always Best Connected’ (ABC) is considered one of the main requirements for next generation networks. The ABC concept allows a person to have access to applications using the devices and network technologies that best suits his or her needs or profile at any time. Clearly, this requires the combination of a set of existing and new technologies, at all levels of the protocol stack, into one integrated system. In this paper, a considerable set of the technologies, that are expected to play a key role towards the ABC vision, are presented. Starting from a reference architecture, the paper describes the required enhancements at certain levels of a traditional protocol stack, as well as technologies for mobility and end‐to‐end Quality of Service (QoS) support. The paper concludes with a case study that reveals the advantages of the ABC concept. Copyright © 2004 John Wiley & Sons, Ltd.     

The Use of Silica Microparticles to Improve the Efficiency of Optical Hyperthermia (OH)

Although optical hyperthermia could be a promising anticancer therapy, the need for high concentrations of light-absorbing metal nanoparticles and high-intensity lasers, or large exposure times, could discourage its use due to the toxicity that they could imply. In this article, we explore a possible role of silica microparticles that have high biocompatibility and that scatter light, when used in combination with conventional nanoparticles, to reduce those high concentrations of particles and/or those intense laser beams, in order to improve the biocompatibility of the overall procedure. Our underlying hypothesis is that the scattering of light caused by the microparticles would increase the optical density of the irradiated volume due to the production of multiple reflections of the incident light: the nanoparticles present in the same volume would absorb more energy from the laser than without the presence of silica particles, resulting either in higher heat production or in the need for less laser power or absorbing particles for the same required temperature rise. Testing this new optical hyperthermia procedure, based on the use of a mixture of silica and metallic particles, we have measured cell mortality in vitro experiments with murine glioma (CT-2A) and mouse osteoblastic (MC3T3-E1) cell lines. We have used gold nanorods (GNRs) that absorb light with a wavelength of 808 nm, which are conventional in optical hyperthermia, and silica microparticles spheres (hereinafter referred to as SMSs) with a diameter size to scatter the light of this wavelength. The obtained results confirm our initial hypothesis, because a high mortality rate is achieved with reduced concentrations of GNR. We found a difference in mortality between CT2A cancer cells and cells considered non-cancer MC3T3, maintaining the same conditions, which gives indications that this technique possibly improves the efficiency in the cell survival. This might be related with differences in the proliferation rate. Since the experiments were carried out in the 2D dimensions of the Petri dishes, due to sedimentation of the silica particles at the bottom, whilst light scattering is a 3D phenomenon, a large amount of the energy provided by the laser escapes outside the medium. Therefore, better results might be expected when applying this methodology in tissues, which are 3D structures, where the multiple reflections of light we believe will produce higher optical density in comparison to the conventional case of no using scattering particles. Accordingly, further studies deserve to be carried out in this line of work in order to improve the optical hyperthermia technique.