Nonlinear STAP processing

The paper deals with the cancellation of clutter echoes in modern airborne early warning (AEW) radar systems equipped with digital beam-forming. The performances of reduced degrees of freedom (DoF) GLRT (generalised likelihood ratio test) detectors and the previously conceived nonlinear detector are compared. The nonlinear detector is demonstrated to be a compromise solution between computational requirements and detection performance. Moreover, it shows much higher robustness to nonhomogeneous clutter. A MATLAB-based software tool is used to show the results that can be achieved using live data recorded by the experimental radar AAFTE (Adaptive Array Flight Test Equipment) of the US Naval Research Laboratory     

A Simple Analytical Framework for the Performance Evaluation of a Tree-Based Connection Rerouting Architecture in a UMTS Network

The enormous increase in wireless communications and the growing request for transmission bandwidth have led to the need to configure wireless access networks with cellular structures based on the use of micro- and pico-cells. Applying these structures means that handovers between neighboring cells are more frequent and therefore have to be carefully managed. A key issue in connection with this is the rerouting of the data flows directed to a user making a handover. In fact, the time interval needed to update all the routing tables in the crossover switches is critical because in this interval data have to be stored, and later forwarded once the route towards the new location has been determined. The paper considers a connectionless protocol, the Signaling Network Layer (SNL), which has been conceived for use in the Universal Mobile Telecommunication System (UMTS) context for connection rerouting purposes and is based on a tree-structured rerouting architecture. Through an analytical model based on a queueing network, its performance is analyzed in terms of the distribution of the rerouting delay. The proposed model is then applied to a case study to demonstrate its versatility and manageability and to get insight into the dimensioning of the rerouting architecture.     

Estimating topology preserving and smooth displacement fields

We propose a method for enforcing topology preservation and smoothness onto a given displacement field. We first analyze the conditions for topology preservation on two- and three-dimensional displacement fields over a discrete rectangular grid. We then pose the problem of finding the closest topology preserving displacement field in terms of its complete set of gradients, which we later solve using a cyclic projections framework. Adaptive smoothing of a displacement field is then formulated as an extension of topology preservation, via constraints imposed on the Jacobian of the displacement field. The simulation results indicate that this technique is a fast and reliable method to estimate a topology preserving displacement field from a noisy observation that does not necessarily preserve topology. They also show that the proposed smoothing method can render morphometric analysis methods that are based on displacement field of shape transformations more robust to noise without removing important morphologic characteristics.     

Human body shadowing variability in short-range indoor radio links at 3–11 GHz band

Measurement results for human body shadowing and local environmental effects in short-range indoor radio channels are presented. A narrowband measurement system, comprising a signal generator, two identical triangular monopoles and a spectrum analyser, was used in the measurements. When the radio link was periodically blocked by a human body with various objects in and around the link, fading depths of up to 15 dB and even more were observed at spot frequencies of 3–11 GHz band. Standard deviation and its range for human body blockage are estimated for different radio link scenarios simulating real environments. The distribution of human body shadowing was analysed and compared with known distribution functions.     

Dirac Fermions in Blue Phosphorene Monolayer

2D materials beyond graphene and in particular 2D semiconductors have raised interest due to their unprecedented electronic properties, such as high carrier mobility or tunable bandgap. Blue phosphorene is an allotrope of black phosphorene that resembles graphene as it presents a honeycomb structure. However, it is known to have semiconductor character and the crucial point is to determine whether this hexagonal phase of phosphorene presents Dirac fermions as in graphene. Here, the first compelling experimental evidence of Dirac fermions in blue phosphorene layer grown on Cu(111) surface is presented. The results highlight the formation of a highly ordered blue phosphorene sheet with a clear Dirac cone at the high symmetry points of the Brillouin Zone. The charge carriers behave as massless relativistic particles. Therefore, all the expectations held for graphene, such as high-speed electronic devices based on ballistic transport at room temperature, may also be applied to blue phosphorene.     

In‐center hemodialysis attendance: Patient perceptions of risks,barriers, and recommendations

Missed hemodialysis treatments lead to increased morbidity and mortality in the end‐stage renal disease population. Little is known about why patients have difficulty attending their scheduled in‐center dialysis treatments. Semistructured interviews with 15 adherent and 15 nonadherent hemodialysis patients were conducted to determine patients' attitudes about dialysis, health beliefs and risk perception regarding missed treatments, barriers and facilitators to hemodialysis attendance, and recommendations to improve the system to facilitate dialysis attendance. Average time on dialysis was 2.5 years for the nonadherent group and 7.3 years in the adherent group. In both groups, patients felt that dialysis is life‐saving and a necessity. A substantial number of patients in both groups understood that missing hemodialysis treatments is dangerous and several patients could clearly communicate the risk of skipping. The most common barriers to hemodialysis were inadequate or unreliable transportation (mentioned in both groups) and a lack of motivation to get to dialysis or that dialysis is not a priority (typically mentioned by the nonadherent group). Facilitators to hemodialysis attendance included explanations from the health care team regarding the risk of skipping and relationships with other dialysis patients. Patient recommendations to improve dialysis attendance included continued education about the risk of poor attendance and more accessible transportation. Patients did not feel that home dialysis would improve adherence. Hemodialysis patients must adhere to a complex and burdensome regimen. Through the elucidation of barriers and facilitators to hemodialysis attendance and through specific patient recommendations, at least three interventions may be further investigated to improve hemodialysis attendance: Improvement of the transportation system, education and supportive encouragement from the health care team, and peer support mentorship.     

Complexity analysis of sleep and alterations with insomnia based on non-invasive techniques

For the first time, fractal analysis techniques are implemented to study the correlations present in sleep actigraphy for individuals suffering from acute insomnia with comparisons made against healthy subjects. Analysis was carried out for 21 healthy individuals with no diagnosed sleep disorders and 26 subjects diagnosed with acute insomnia during night-time hours. Detrended fluctuation analysis was applied in order to look for 1/f-fluctuations indicative of high complexity. The aim is to investigate whether complexity analysis can differentiate between people who sleep normally and people who suffer from acute insomnia. We hypothesize that the complexity will be higher in subjects who suffer from acute insomnia owing to increased night-time arousals. This hypothesis, although contrary to much of the literature surrounding complexity in physiology, was found to be correct—for our study. The complexity results for nearly all of the subjects fell within a 1/f-range, indicating the presence of underlying control mechanisms. The subjects with acute insomnia displayed significantly higher correlations, confirmed by significance testing—possibly a result of too much activity in the underlying regulatory systems. Moreover, we found a linear relationship between complexity and variability, both of which increased with the onset of insomnia. Complexity analysis is very promising and could prove to be a useful non-invasive identifier for people who suffer from sleep disorders such as insomnia.     

Line balancing and model sequencing to reduce work overload in mixed-model U-line production environments

Mixed-model U-lines (MMULs) are important elements of just-in-time production systems. For successful implementation of MMULs, a smoothed workload distribution among workstations is important. This requires that line balancing and model sequencing problems are solved simultaneously. This article presents a mixed, zero–one, nonlinear mathematical programming formulation for balancing and sequencing MMULs simultaneously with the objective of reducing work overload. Since the problem is NP-hard, an effective simulated annealing approach is also presented and its performance compared with existing approaches. The results show that the proposed simulated annealing algorithm outperforms existing approaches.     

Magnetic cell separation: characterization of magnetophoretic mobility

Magnetic cell separation has become a popular technique to enrich or deplete cells of interest from a heterogeneous cell population. One important aspect of magnetic cell separation is the degree to which a cell binds paramagnetic material. It is this paramagnetic material that imparts a positive magnetophoretic mobility to the target cell, thus allowing effective cell separation. A mathematical relationship has been developed to correlate magnetic labeling to the magnetophoretic mobility of an immunomagnetically labeled cell. Four parameters have been identified that significantly affect magnetophoretic mobility of an immunomagnetically labeled cell: the antibody binding capacity (ABC) of a cell population, the secondary antibody amplification (psi), the particle-magnetic field interaction parameter (DeltachiV(m)), and the cell diameter (D(c)). The ranges of these parameters are calculated and presented along with how the parameters affect the minimum and maximum range of magnetophoretic mobility. A detailed understanding of these parameters allows predictions of cellular magnetophoretic mobilities and provides control of cell mobility through selection of antibodies and magnetic particle conjugates.     

Poly(ethylene glycol dimethacrylate-n-vinyl imidazole) beads for heavy metal removal

Poly(ethylene glycol dimethacrylate-n-vinyl imidazole) [poly(EGDMA-VIM)] hydrogel (average diameter 150-200 microm) was prepared by copolymerizing ethylene glycol dimethacrylate (EGDMA) with n-vinyl imidazole (VIM). The copolymer hydrogel bead composition was characterized by elemental analysis and found to contain 5 EGDMA monomer units each VIM monomer unit. Poly(EGDMA-VIM) beads had a specific surface area of 59.8 m2/g. Poly(EGDMA-VIM) beads were characterized by swelling studies and scanning electron microscopy (SEM). These poly(EGDMA-VIM) beads with a swelling ratio of 78% were used for the heavy metal removal studies. Chelation capacity of the beads for the selected metal ions, i.e., Cd(II), Hg(II) and Pb(II) were investigated in aqueous media containing different amounts of these ions (10-750 mg/l) and at different pH values (3.0-7.0). Chelation rate was very fast. The maximum chelation capacities of the poly(EGDMA-VIM) beads were 69.4 mg/g for Cd(II), 114.8 mg/g for Pb(II) and 163.5 mg/g for Hg(II). The affinity order on molar basis was observed as follows: Hg(II) > Cd(II) > Pb(II). Chelation behavior of heavy metal ions could be modelled using both the Langmuir and Freundlich isotherms. pH significantly affected the chelation capacity of VIM incorporated beads. Chelation of heavy metal ions from synthetic wastewater was also studied. The chelation capacities are 45.6 mg/g for Cd(II), 74.2 mg/g for Hg(II) and 92.5 mg/g for Pb(II) at 0.5 mmol/l initial metal concentration. Regeneration of the chelating-beads was easily performed with 0.1 M HNO3. These features make poly(EGDMA-VIM) beads potential candidate adsorbent for heavy metal removal.