A Surprise Party (on Your Computer)?

Iv?n Arce of Core Security Technologies looks at the current state of malware and introduces the articles he selected for this special issue.     

A review of the metallurgy of heat treatment of welded joints

This paper deals with the metallurgical changes which occur during heat treatment of welded joints. Stress relieving heat treatment in the temperature range below A₁, the normalizing heat treatment and the heat treatment in the intercritical range A₁–A₃, are all considered. The thermal regime of welding is described. The practice of intercover of the weldment before applying PWHT to ambient temperature is described. It is stressed that the aim of stress-relieving heat treatment is not only to relax internal stresses but also to improve the microstructure and impact properties of HAZ and weld metal, to improve dimensional stability and increase resistance against stress corrosion. Examples are given of the effect of annealing in the intercritical range A₁–A₃ on the improvement in toughness of electroslag welded joints. Changes in dislocation distribution and density, precipitation processes and grain sizes during PWHT are described.     

A Survey on the Numerics and Computations for the Landau-Lifshitz Equation of Micromagnetism

The Landau-Lifshitz (LL)equation of micromagnetism governs rich variety of the evolution of magnetization patterns in ferromagnetic media. This is due to the complexity of physical quantities appearing in the LL equation. This complexity causes also an interesting mathematical properties of the LL equation: nonlocal character for some quantities,nonconvex side-constraints, strongly nonlinear terms. These effects influence also the numerical approximations. In this work, recent developments on the approximation of weak solutions, together with the overview of well-known methods for strong solutions,are addressed. Author is supported by the Fund for Scientific Research - Flanders FWO (Belgium).     

Software Licensing Models: What's Out There?

As software and hardware evolve, licensing choices are becoming more complex. Understanding licensing trends and the latest models is one way to achieve the greatest return on software investment.     

Investigation of Flow Patterns in Continuous‐flow Stirred Vessels by Laser Doppler Velocimetry

The flow structure of a continuous‐flow reactor stirred by a Rushton turbine was investigated by laser Doppler velocimetry for two different mean residence time‐mixing time ratios. Velocity measurements were obtained for two inlet locations, corresponding to the incoming liquid stream being fed co‐currently or counter‐currently to the flow discharged by the turbine. In all investigated configurations and for all operating conditions, it was found that the flow disruption caused by the incoming liquid stream was observable mainly in the first vessel quarter, which followed the feed‐tube plane. From comparison of the velocities encountered in the various planes in the continuous‐flow reactor to the velocities of the batch reactor, it was also concluded that it may be possible to intensify the usage of the turbine‐stirred vessel by decreasing the characteristic times ratio, without considerable flow by‐pass and/or short‐circuiting problems.     

Reconstructing design parameters of a rectangular resonator via peak signal-to-noise ratio and global optimization algorithms

This article proposes an approach for reconstructing physical parameters of a sample in a rectangular resonator during microwave radiation, knowing a priori, its electric field distribution. The inverse problem was solved using two global optimization algorithms and the peak signal-to-noise ratio (PSNR) criterion. First, the Self-regulated Fretwidth Harmony Search algorithm (SFHS) identified suitable resonant frequencies for a given configuration. Next, the unified Particle Swarm Optimization (UPSO) optimized said configuration. Together, they became a maximization strategy of the PSNR through a dual optimization process. Results showed the ability of the approach for estimating the height of each sample block and the resonating frequency of the cavity. This process takes longer to finish as a higher PSNR is demanded (mainly due to the aforementioned dual optimization). Even so, it allows for more similar electric field distributions between both, the direct and inverse problems.     

Performance analysis of the IEEE 802.11 DCF in the presence of the hidden stations

In this paper, we present an analytical model to evaluate the hidden station effect on the performance of the IEEE 802.11 Distributed Coordination Function (DCF) in both non-saturation and saturation condition. DCF is a random channel-access scheme based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) method and the exponential backoff procedure. DCF is widely used and can support both wireless network with an access point and ad hoc wireless network because of its random channel-access method. On the other hand, this method unavoidably suffers the hidden station effect that causes significant performance degradation. As shown in this paper, hidden stations occur frequently in real-world settings, and the performance impact on the 802.11 DCF is a significant concern, but it has not been adequately studied. We study this problem through a spatial–temporal analysis and a Markov chain model. Our model generalizes the existing work on the performance modeling of 802.11 DCF for both non-saturation and saturation conditions. The scenario of no hidden station can be considered as a special case in our model. The performance of our model is evaluated by comparison with ns-2 simulations.     

Morphometric and some immunohistochemical characteristics of human choroids plexus stroma and psammoma bodies

Psammoma bodies (PBs) are one of many choroids plexus aging changes. The aim of our research was to perform the quantification of PBs' presence in human choroids plexus stroma, as well as to evaluate the characteristics of choroids plexus stroma in cases in which PBs were present. Afterwards, the observations of the histochemical analysis would be confirmed by immunohistochemical analysis. Choroid plexuses of 30 cadavers were used for the histochemical and, choroids plexuses of 15 cadavers in which PBs' presence was confirmed during the histochemical analysis, were used as material for the immunohistochemical analysis. Light microscopy, histochemical, immunohistochemical, and morphometric method were applied during the study. Classification of the cases was performed by cluster analysis. We observed increase of choroids plexus PBs' presence during the aging process. But this increase is not linear. Their presence is the largest in the second cluster that is younger than the third and older than the first. Nuclear morphometric parameters of the stroma in these cases showed that the cellular composition in this cluster is different than in other two and, that contain larger number of lymphoid cells. Immunohistochemical analysis showed PBs' positive reaction on vimentin, CD45R0, and LCA markers, while in their vicinity, as well as inside them, numerous T-cells were observed. So, the presence of CD45R0 and LCA-positive T cells, PBs' positive reaction on the same markers, indirectly connect these cells with PBs' formation process.     

Effective dimensionality of cuprate superconductors

A novel optical method for accurate monitoring of the carrier densityN in layered conductors is introduced. It is applied to several cuprate superconductors, and it is found thatT _c doesnot scale withN. However, if the closely spaced pairs or triplets of CuO₂ planes were coupled together to act as distinct metallic slabs, the relevant variable could ben, theslab carrier density. Indeed, we found thatT _c does scale nicely withn. This suggests that high-T _c superconductivity is effectively a two-dimensional phenomenon; it can occur in a cuprate slab which is only one unit cell thick. Finally, estimates are obtained for the length scales of localization of charge carriers:d 8 Å andd 2 Å in all the cuprates under study.