An adaptive least squares channel estimation based on conjugate gradient approach for multipath fading CDMA systems

Multiple access interference (MAI) is the main factor affecting the performance of channel estimation techniques for code division multiple access (CDMA) systems. Although, several multi-user channel estimation algorithms have been proposed to mitigate MAI, these algorithms require high computational complexities. In this paper, we address the problem of iterative least squares (LS) mobile channel estimation at high channel efficiency that requires a short training sequence along with the spreading sequences. We employ an efficient iterative method based on conjugate gradient (CG) algorithm to reduce the computational complexity of the estimation method. Computer simulations illustrate that the proposed method performs almost identical to the exact LS estimate for reasonable training lengths.     

Comparison of alteplase (tissue plasminogen activator) high‐dose vs. low‐dose protocol in restoring hemodialysis catheter function: The ALTE‐DOSE study

Hemodialysis catheter (HDC) dysfunction due to thrombosis is common, and dysfunction incidence can reach up to 50% within 1 year of use. Although administration of intraluminal alteplase (tissue plasminogen activator [tPA]) is the standard of practice to pharmacologically restore HDC function, there are no evidence‐based guidelines concerning the optimal tPA dose. The purpose of this study was to compare the efficacy of 1.0‐mg vs. 2.0‐mg tPA dwell protocols in restoring the HDC function in thrombotic dysfunctional catheters. A retrospective, single‐center study was conducted on two independent cohorts of patients; the first (n = 129) received 2.0 mg tPA/catheter lumen, while the second (n = 108) received 1.0 mg tPA/catheter lumen. Kaplan–Meier and Cox regression analyses were performed to compare the catheter survival time between patients who received 1.0 mg tPA and those who received 2.0 mg tPA. Catheter removal occurred in 25 (19.4%) of those catheters treated with 1.0 mg tPA compared with 11 (10.2%) of catheters treated with 2.0 mg tPA (P = 0.05). The hazard ratio (HR) for catheter removal was 2.75 (95% confidence interval [^95%CI] = 1.25–6.04) for the 1.0‐mg tPA cohort compared with the 2.0‐mg tPA cohort. Correction added on 3 December 2012, after first online publication: The tPA cohort values were changed. Female gender (HR = 2.51; ^95%CI = 1.20–5.27) and age (HR = 0.96; ^95%CI = 0.94–0.98) were also associated with catheter survival. Our findings suggest that treatment of dysfunctional HDC with 2.0‐mg tPA dwells is superior to 1.0‐mg tPA dwells.     

Cultural Experience as a (Critical) Factor in Crisis Communication Planning

A key issue in crisis communication is the way people process crisis‐relevant information to minimize danger. This paper discusses the impact of previously experienced crises on the public's interpretation of warning messages. People may not have direct experience of a crisis, but they still have acquired mediated experiences of a variety of crises. The present study introduces the term cultural experience of crisis to label the synthesis of mediated crisis experiences, media and fictional narratives, collective memories of societal disasters, conversations, and immediate crisis experiences of witnesses and victims. The proposed model of cultural experience of crisis is elaborated on the basis of a qualitative text analysis derived from four qualitative interviews 16 focus groups interviews carried out in Estonia from 2008 to 2009.     

Effect of mineral filler type on autogenous shrinkage of self-compacting concrete

Based on an experimental programme, including autogenous shrinkage tests on concrete, ultrasonic monitoring of fresh concrete, and mercury intrusion porosimetry, the influence of the filler type on the autogenous shrinkage of self-compacting concrete has been investigated. The onset of percolating structure formation (time zero) is influenced by the filler type due to a possible accelerating effect of the filler on the cement hydration. Limestone filler accelerates the hydration process, and reduces time zero, while this is not the case when using quartzite filler. Using fly ash, showing only a slight acceleration, a slight reduction of time zero is obtained. A very significant swelling peak is noticed during the first day. This swelling peak is not a measuring artefact, but is caused mainly by water absorption on the filler surface and resulting disjoining pressure. Some part of the swelling peak might also be caused by Ca(OH)₂ crystallisation. The fineness of the filler is an important factor for this swelling behaviour, although also the nature of the filler seems to have an influence. The superplasticiser also interacts with the fillers, influencing the swelling behaviour. The different filler types used in this study did not lead to significant differences in critical pore diameter of the microstructure. This might explain why no significant differences have been found in final autogenous shrinkage values using the different filler types.     

Catalytic coating of virus particles with zinc oxide

We show that the rod-shaped Tobacco mosaic virus (TMV) can be coated with the wide band gap semiconductor zinc oxide by electroless deposition under mild reaction conditions. The process involves pretreatment with aqueous Pd(II), followed by nucleation of ZnO, directed to palladium centers formed on the surface of TMV. The mechanism is based on the local pH change due to the reduction of nitrate by dimethylamine borane at the palladium. Morphology and chemical composition have been analyzed by transmission electron microscopy (TEM) and by energy filtering TEM, respectively. The optical properties were elucidated by cathodoluminescence, which showed the desired near-band edge emission.     

Underdog or bulldog: introducing biogas technologies in Estonia

The production and use of biogas, along with corresponding sector-specific activities and technologies, is a relatively new subject in Estonia. This paper gives an instructive overview of main barriers behind the development incentives, policy support and technological innovation in terms of emerging market for biogas. The article examines the complexity of market-related, political, technological and social obstacles for introduction biogas technologies. There is a major gap between resource potential, technological capacity and practice in Estonia. About 2?% of the theoretical potential of biogas is being used, totalling around 11?million?Nm³, based primarily on landfill biogas. First, political setting for biogas innovation is still vague, however, consolidated and enhanced since 2010 to compete with other renewables and mainstream energy technologies. The article underlines the statement that the reason why Estonian biogas production has not followed the path of growth and technology transfer is the low renewable electricity feed-in tariff. However, there are many other legal and engineering factors that have held back biogas applications and sector development in general. Stakeholders have established the Estonian Biogas Association, increasing sector’s visibility, targeted lobby to support policy-making, technological and social innovation and professional networking. Though getting the biogas sector to succeed demands a comprehensive approach and involvement of more actors in demand side including local leaders and consumers, both enthusiasm and scepticism should be informed by a sound understanding of framework conditions and complexities for path-breaking transformations in energy systems. To promote biogas production, profitable and technologically feasible showcases should demonstrate benefits and issues to the target group and stakeholders. Instead agricultural and CHP development mode, the priority of using biogas in Estonia could be seen as green vehicle fuel for transport.     

Efficiency of granulated blast furnace slag replacement of cement according to the equivalent binder concept

The strength development of slag cement has a great consideration for the scheduling of formwork removal, prestressing operations, and other practical aspects of slag cement usage. The prediction of slag concrete strength, using the Feret’s model has been studied by introducing the concept of the equivalent binder. This has led to define an efficiency coefficient of slag which distinguishes the latter with the regard to the cement. Thus, this obtained coefficient characterizes well the slag and lets to predict the slag concrete strength from strength values of a normal concrete made without slag for a given age and replacement rate. At 90 days age, the test results show that for 15% replacement rate, the slag is activated completely and gives 67% of efficiency more than the cement. For higher replacement rate, the efficiency of the slag decreases and becomes similar to that of cement for 50% replacement rate.