New method for generalised PR target design for perpendicular magnetic recording

In recent years, perpendicular magnetic recording (PMR) has been the main topic of interest in the industry. Given current estimates, that would suggest an areal density using PMR as great as one terabit per square inch – making possible in two to three years a 3.5-inch disk drive capable of storing an entire terabyte of data [1]. As the areal density is increased, however, the signal processing aspects of magnetic recording becomes more difficult. The present technique for finding the optimised GPR targets is based on the minmimum mean squared error (MMSE) between the equaliser output and the desired output, subject to the monic constraint [2]. In this paper, we present a new method of designing GPR targets for PMR. This method is based on maximising the ratio of minimum squared eucledian distance of the PR target to the noise penalty introduced by the PR filter

A novel low complexity local hybrid pseudo-SSIM-SATD distortion metric towards perceptual rate control

The front-end block-based video encoder applies an Image Quality Assessment (IQA) as part of the distortion metric. Typically, the distortion metric applies uniform weighting for the absolute differences within a Sub-Macroblock (Sub-MB) at any given time. As video is predominately designed for Humans, the distortion metric should reflect the Human Visual System (HVS). Thus, a perceptual distortion metric (PDM), will lower the convex hull of the Rate-Distortion (R-D) curve towards the origin, by removing perceptual redundancy and retaining perceptual clues. Structured Similarity (SSIM), a perceptual IQA, has been adapted via logarithmic functions to measure distortion, however, it is restricted to the Group of Picture level and hence unable to adapt to the local Sub-MB changes. This paper proposes a Local Hybrid Pseudo-SSIM-SATD (LHPSS) Distortion Metric, operating at the Sub-MB level and satisfying the Triangle Equality Rule (≤). A detailed discussion of LHPSS's Psuedo-SSIM model will illustrate how SSIM can be perceptually scaled within the distortion metric space of SATD using non-logarithmic functions. Results of HD video encoded across different QPs will be presented showing the competitive bit usage under IbBbBbBbP prediction structure for similar image quality. Finally, the mode decision choices superimposed on the Intra frame will illustrate that LHPSS lowers the R-D curve as homogeneous regions are represented with larger block size

Review of standard traditional distortion metrics and a need for perceptual distortion metric at a (sub) macroblock level

Within a video encoder the distortion metric performs an Image Quality Assessment (IQA). However, to exploit perceptual redundancy to lower the convex hull of the Rate- Distortion (R-D) curve, a Perceptual Distortion Metric (PDM) modelling of the Human Visual System (HVS) should be used. Since block-based video encoders like H.264/AVC operate at the Sub-Macroblock (Sub-MB) level, there exists a need to produce a locally operating PDM. A locally operating PDM must meet the requirements of Standard Traditional Distortion Metrics (STDMs), in that it must satisfy the Triangle Equality Rule. Hence, this paper presents a review of STDMs of SSE, SAD and SATD against the perceptual IQA of Structural Similarity (SSIM) at the Sub-MB level. Furthermore, this paper illustrates the Universal Bounded Region (UBR) by block size that supports the triangle equality rule within the Sub-MB level, between SSIM and STDMs like SATD at the prediction stage

Convalescent plasma for COVID-19 complicated by ARDS due to TRALI

© 2021 BMJ Publishing Group. All rights reserved. Convalescent plasma, which contains antibodies from recovered individuals, has been used as an effective treatment for infectious diseases in the past and is currently being used as a potential treatment option for COVID-19. Multiple studies have reported this treatment to be safe. We report a case of a patient who developed acute respiratory distress syndrome (ARDS) with features suggestive of transfusion-related acute lung injury after being treated with convalescent plasma for COVID-19. We emphasise the need to be aware of the potential risk of transfusion reactions and disease worsening with convalescent plasma administration and to weigh the risk and benefits of this therapy before administration to patients and propose that further study be done regarding the potential risks of convalescent plasma

Exploiting resource contention in highly mobile environments and its application to vehicular ad-hoc networks

As network resources are shared between many users, resource management must be a key part of any communication system as it is needed to provide seamless communication and to ensure that applications and servers receive their required Quality-of-Service. However, mobile environments also need to consider handover issues. Furthermore, in a highly mobile environment, traditional reactive approaches to handover are inadequate and thus proactive techniques have been investigated. Recent research in proactive handover techniques, defined two key parameters: Time Before Handover and Network Dwell Time for a mobile node in any given networking topology. Using this approach, it is possible to enhance resource management in common networks using probabilistic mechanisms because it is possible to express contention for resources in terms of: No Contention, Partial Contention and Full Contention. This proactive approach is further enhanced by the use of a contention queue to detect contention between incoming requests and those waiting for service. This paper therefore presents a new methodology to support proactive resource allocation for future networks such as Vehicular Ad-Hoc Networks. The proposed approach has been applied to a vehicular testbed and results are presented that show that this approach can improve overall network performance in mobile heterogeneous environments

Structural and magnetic properties of Pr-alloyed MnBi nanostructures

The structural and magnetic properties of Pr-alloyed MnBi (short MnBi-Pr) nanostructures with a range of Pr concentrations have been investigated. The nanostructures include thin films having Pr concentrations 0, 2, 3, 5 and 9 atomic percent and melt-spun ribbons having Pr concentrations 0, 2, 4 and 6 percent respectively. Addition of Pr into the MnBi lattice has produced a significant change in the magnetic properties of these nanostructures including an increase in coercivity and structural phase transition temperature, and a decrease in saturation magnetization and anisotropy energy. The highest value of coercivity measured in the films is 23 kOe and in the ribbons is 5.6 kOe. The observed magnetic properties are explained as the consequences of competing ferromagnetic and antiferromagnetic interactions

The Spitzer Survey of the Small Magellanic Cloud: Discovery of Embedded Protostars in the HII Region NGC 346

We use Spitzer Space Telescope observations from the Spitzer Survey of the Small Magellanic Cloud (S3MC) to study the young stellar content of N66, the largest and brightest HII region in the SMC. In addition to large numbers of normal stars, we detect a significant population of bright, red infrared sources that we identify as likely to be young stellar objects (YSOs). We use spectral energy distribution (SED) fits to classify objects as ordinary (main sequence or red giant) stars, asymptotic giant branch stars, background galaxies, and YSOs. This represents the first large-scale attempt at blind source classification based on Spitzer SEDs in another galaxy. We firmly identify at least 61 YSOs, with another 50 probable YSOs; only one embedded protostar in the SMC was reported in the literature prior to the S3MC. We present color selection criteria that can be used to identify a relatively clean sample of YSOs with IRAC photometry. Our fitted SEDs indicate that the infrared-bright YSOs in N66 have stellar masses ranging from 2 Msun to 17 Msun, and that approximately half of the objects are Stage II protostars, with the remaining YSOs roughly evenly divided between Stage I and Stage III sources. We find evidence for primordial mass segregation in the HII region, with the most massive YSOs being preferentially closer to the center than lower-mass objects. Despite the low metallicity and dust content of the SMC, the observable properties of the YSOs appear consistent with those in the Milky Way. Although the YSOs are heavily concentrated within the optically bright central region of N66, there is ongoing star formation throughout the complex and we place a lower limit on the star formation rate of 3.2 x 10^-3 Msun/yr over the last ~1 Myr.Comment: 13 pages, 5 figures (3 in color), 2 tables. Accepted for publication in Ap

Failure time and microcrack nucleation

The failure time of samples of heterogeneous materials (wood, fiberglass) is studied as a function of the applied stress. It is shown that in these materials the failure time is predicted with a good accuracy by a model of microcrack nucleation proposed by Pomeau. It is also shown that the crack growth process presents critical features when the failure time is approached.Comment: 13 pages, 4 figures, submitted to Europhysics Letter

The improvement of Mo/4H-SiC Schottky diodes via a P2O5 surface passivation treatment

Molybdenum (Mo)/4H-silicon carbide (SiC) Schottky barrier diodes have been fabricated with a phosphorus pentoxide (P2O5) surface passivation treatment performed on the SiC surface prior to metallization. Compared to the untreated diodes, the P2O5-treated diodes were found to have a lower Schottky barrier height by 0.11 eV and a lower leakage current by two to three orders of magnitude. Physical characterization of the P2O5-treated Mo/SiC interfaces revealed that there are two primary causes for the improvement in electrical performance. First, transmission electron microscopy imaging showed that nanopits filled with silicon dioxide had formed at the surface after the P2O5 treatment that terminates potential leakage paths. Second, secondary ion mass spectroscopy revealed a high concentration of phosphorus atoms near the interface. While only a fraction of these are active, a small increase in doping at the interface is responsible for the reduction in barrier height. Comparisons were made between the P2O5 pretreatment and oxygen (O2) and nitrous oxide (N2O) pretreatments that do not form the same nanopits and do not reduce leakage current. X-ray photoelectron spectroscopy shows that SiC beneath the deposited P2O5 oxide retains a Si-rich interface unlike the N2O and O2 treatments that consume SiC and trap carbon at the interface. Finally, after annealing, the Mo/SiC interface forms almost no silicide, leaving the enhancement to the subsurface in place, explaining why the P2O5 treatment has had no effect on nickel- or titanium-SiC contacts

Scaling and Formulary cross sections for ion-atom impact ionization

The values of ion-atom ionization cross sections are frequently needed for many applications that utilize the propagation of fast ions through matter. When experimental data and theoretical calculations are not available, approximate formulas are frequently used. This paper briefly summarizes the most important theoretical results and approaches to cross section calculations in order to place the discussion in historical perspective and offer a concise introduction to the topic. Based on experimental data and theoretical predictions, a new fit for ionization cross sections is proposed. The range of validity and accuracy of several frequently used approximations (classical trajectory, the Born approximation, and so forth) are discussed using, as examples, the ionization cross sections of hydrogen and helium atoms by various fully stripped ions.Comment: 46 pages, 8 figure