Improved Energy Detector for Wideband Spectrum Sensing in Cognitive Radio Networks

In this paper, an improved energy detector for a wideband spectrum sensing is proposed. For a better detection of the spectrum holes the overall band is divided into equal non-overlapping sub-bands. The main objective is to determine the detection thresholds for each of these subbands jointly. By defining the problem as an optimization problem, we aim to find the maximum aggregated opportunistic throughput of cognitive radio networks. Introducing practical constraints to this optimization problem will change the problem into a convex and solvable one. The results of this paper show that the proposed improved energy detector will increase the aggregated throughput considerably

Association of characteristics of delivery and medical conditions during the first month of life with developmental defects of enamel.

BACKGROUND: Developmental defects of enamel (DDE) may be influenced by health problems and illness in children. The aim of the study was to identify the main characteristics of birth (delivery) and adverse medical conditions during the first month of life that may be related to DDE in permanent teeth. METHODS: 1000 schoolchildren between the ages of 9 and 11 years were selected for this cross-sectional study by multistage randomization from four educational zones in Shiraz in 2013. Intraoral examination was used to diagnose DDE according to World Health Organization screening guidelines and the Modified DDE Index. The data on seven birth factors as well as health and nutritional conditions during the first month of life were collected by a questionnaire completed by the parents, and were analyzed with the chi-squared test, Spearman's correlation and binary logistic regression. RESULTS: 469 (48.2%) out of 974 schoolchildren had at least one permanent tooth with DDE. The defects were significantly related with Apgar score at birth <7 (p = 0.003) and illness during the first month (p = 0.035). The frequency of DDE was significantly lower in the third child in families compared to the first and second child (p = 0.005). However, DDE showed no significant relationship with gestational age, delivery type, birth weight, gender or type of feeding during early infancy. CONCLUSIONS: Three associated factors were identified (birth Apgar score, illness during the first month of life, birth order) for DDE in permanent teeth. No specific illness was found to be significantly associated with DDE

Acoustic phonon scattering in a low density, high mobility AlGaN/GaN field effect transistor

We report on the temperature dependence of the mobility, $\mu$, of the two-dimensional electron gas in a variable density AlGaN/GaN field effect transistor, with carrier densities ranging from 0.4$\times10^{12}$ cm$^{-2}$ to 3.0$\times10^{12}$ cm$^{-2}$ and a peak mobility of 80,000 cm$^{2}$/Vs. Between 20 K and 50 K we observe a linear dependence $\mu_{ac}^{-1} = \alpha$T indicating that acoustic phonon scattering dominates the temperature dependence of the mobility, with $\alpha$ being a monotonically increasing function of decreasing 2D electron density. This behavior is contrary to predictions of scattering in a degenerate electron gas, but consistent with calculations which account for thermal broadening and the temperature dependence of the electron screening. Our data imply a deformation potential D = 12-15 eV.Comment: 3 pages, 2 figures, RevTeX. Submitted to Appl Phys Let

A comparative analysis of particle tracking in a mixer by discrete element method and positron emission particle tracking

Characterisation of particle flow using Positron Emission Particle Tracking (PEPT) is based on tracking the position of a single particle in a dynamic system. Recent developments in PEPT have facilitated tracking multiple particles aiming at improvements in data representation. Nevertheless for systems with a wide residence time distribution and/or dead zone, the conditions for getting representative data which could reflect the bulk behaviour of the powders need to be analysed and specified. In the present work, an attempt is made to simulate PEPT experiments for a paddle mixer using Discrete Element Method (DEM), with a view to investigate the effect of increasing the number of tracers on their time-averaged velocity distribution and whether it can represent the data on whole population of particles. The time averaged velocity distribution of the individual tracer particles (resembling simulated PEPT) is obtained and compared with the time averaged data on entire particle population. The DEM results indicate that for the investigated paddle mixer, it takes 251. s for one tracer to travel adequately in all the active space of the system. The instantaneous tracer velocity fluctuates around the average value obtained for all the particles, suggesting that the average tracer velocity is adequately representative of the average particle velocity in the system. The data of the PEPT experiment with one tracer with those of DEM with one tracer are in good agreement; however, DEM simulation suggests that increasing the number of tracers in the paddle mixer system does not influence the average velocity distribution. Furthermore, the velocity for all particles in the DEM shows a smooth distribution with a peak frequency of the velocity distribution that is lower than PEPT and DEM tracer. When tracking a single tracer in DEM or PEPT, it may not be detected to have zero velocity at any instant of time, whilst the data for all particles show that about 0.3% of particles are stagnant

A PMSM current controller system on FPGA platform

Permanent magnet synchronous motor (PMSM) has gained more interest recently in industrial applications. Digital hardware solutions such as field programmable gate arrays (FPGAs) are the most preferred methods for controlling PMSM drivers. This paper presents an implementation of a current control system for PMSM based on FPGA. Encoder-based speed and position detection method has been used in proposed hardware. The whole system has been modeled and simulated in system level using MATLAB/SIMULINK. Hardware architecture for all computational blocks is implemented using Verilog HDL. The hardware architecture has been successfully synthesized and implemented on Altera Cyclone II FPGA. Proposed system architecture and computational blocks are described and system level and RTL simulation results are presented. Simulation results show that the total computation cycle time of implemented system on Altera Cyclone II FPGA is 456ns.Keywords: PMSM, FPGA, Incremental encoder, CORDIC, Hysteresis Current Control

Optimization of job allocation in construction organizations to maximize workers' career development opportunities

© 2019 American Society of Civil Engineers. Workforce planning in the construction industry too often ignores the symbiotic relationship between employee and employer objectives by overly concentrating on corporate objectives such as maximizing productivity at the expense of construction workers' career development needs. Overall, the consequence of this approach is suboptimal performance. To address this problem, this paper presents an innovative multiobjective model that enables managers to optimize the relationship between these interdependent corporate priorities. The proposed model was implemented and solved using mixed-integer nonlinear programming on a case study involving the allocation of tasks to employees with different skill levels in a multidisciplinary engineering consulting company. While leading to a small loss of productivity, the results show a significant improvement in the career development of workers compared to conventional productivity-oriented workforce planning models, with on average 8.6% improvement in employees' closeness to their ideal skill set. Furthermore, the model produced Pareto-optimal points and a Pareto curve that enabled client-model users to select optimum job allocation based on their preferences. This research represents a paradigm shift toward a new class of socially responsible workforce planning models in which the objectives of both employees and employers are optimized

Differences in maladaptive schemas between patients suffering from chronic and acute posttraumatic stress disorder and healthy controls

War, as a stressor event, has a variety of acute and chronic negative consequences, such as posttraumatic stress disorder (PTSD). In this context, early maladaptive schema-based problems in PTSD have recently become an important research area. The aim of this study was to assess early maladaptive schemas in patients with acute and chronic PTSD.; Using available sampling methods and diagnostic criteria, 30 patients with chronic PTSD, 30 patients with acute PTSD, and 30 normal military personnel who were matched in terms of age and wartime experience were selected and assessed with the Young Schema Questionnaire-Long Form, Beck Depression Inventory second version (BDI-II), the Beck Anxiety Inventory (BAI), and the Impact of Events Scale (IES).; Both acute and chronic PTSD patients, when compared with normal military personnel, had higher scores for all early maladaptive schemas. Additionally, veterans suffering from chronic PTSD, as compared with veterans suffering from acute PTSD and veterans without PTSD, reported more impaired schemas related, for instance, to Self-Control, Social Isolation, and Vulnerability to Harm and Illness.; The results of the present study have significant preventative, diagnostic, clinical, research, and educational implications with respect to PTSD

Negative Echo in the Density Evolution of Ultracold Fermionic Gases

We predict a nonequilibrium critical phenomenon in the space-time density evolution of a fermionic gas above the temperature of transition into the superfluid phase. On the BCS side of the BEC-BCS crossover, the evolution of a localized density disturbance exhibits a negative echo at the point of the initial inhomogeneity. Approaching the BEC side, this effect competes with the slow spreading of the density of bosonic molecules. However, even here the echo dominates for large enough times. This effect may be used as an experimental tool to locate the position of the transition.Comment: 4 pages, 2 figure

CFD modelling of a pilot-scale counter-current spray drying tower for the manufacture of detergent powder

A steady-state, three-dimensional, multiphase CFD modelling of a pilot-plant counter-current spray drying tower is carried out to study the drying behavior of detergent slurry droplets. The software package ANSYS Fluent is employed to solve the heat, mass and momentum transfer between the hot gas and the polydispersed droplets/particles using the Eulerian-Lagrangian approach. The continuous phase turbulence is modelled using the differential Reynolds stress model. The drying kinetics is modelled using a single droplet drying model[1] which is incorporated into the CFD code using user-defined functions. Heat loss from the insulated tower wall to the surrounding is modelled by considering thermal resistances due to deposits on the inside surface, wall, insulation and outside convective film. For the particle-wall interaction, the restitution coefficient is specified as a constant value as well as a function of particle moisture content. It is found that the variation in the value of restitution coefficient with moisture causes significant changes in the velocity, temperature and moisture profiles of the gas as well as the particles. Overall, a reasonably good agreement is obtained between the measured and predicted powder temperature, moisture content and gas temperature at the bottom and top outlets of the tower; considering the complexity of the spray drying process, simplifying assumptions made in both the CFD and droplet drying models and the errors associated with the measurements

Effect of Different Levels of Nano-selenium on Performance, Blood Parameters, Immunity and Carcass Characteristics of BroilerChickens

The aim of the present study was to test the hypothesis that nano- seleniuminclusion in broilers’ diets can improve productivity and metabolic functions of broilers.Feed and water were provided ad libitum. A total of 180 one-day old male Ross 308 chicks were randomly assigned to six groups based on a completely randomized design, each with three replicates of 10 birds. One of the groups served as the control (CON) and was given a basal diet without further dietary supplementation, whereas the other five groups were offered the same starterandgrower diets further supplemented with dietary nano-selenium (NS) at 0.1 mg/kg of feed (NS1), 0.2 mg/kg of feed (NS2), 0.3 mg/kg of feed (NS3), 0.4 mg/kg of feed (NS4), and 0.5 mg/kg of feed (NS5). Nano-selenium dietary supplementation significantly improved weight gain and feed conversion ratio in starter (1st-21st day), grower (22nd-42nd day) and whole (1st-42nd) periods of experiment (P0.05). While, albumin levels in blood were decreased and anti-Newcastle disease hemagglutination-inhibition titer was increased after the dietary supplementation with the nano-selenium (P< 0.05). As conclusion, the current study demonstrated that the supplementation of nano-selenium in broiler diets could improve growth performance, carcass components and immune function, without negative effects on internal organs, and other carcass parameters and gastrointestinal parts