Fluctuating target detection in presence of non Gaussian clutter in OFDM radars

Today, Orthogonal Frequency Division Multiplexing (OFDM) radars are very interested in detection of low Radar Cross Section (RCS) targets. A vast number of research work has been reported about target detection in OFDM radars. But all these papers concern detection in presence of Gaussian interference and also assume that target has a constant scattering coefficient or RCS. In this paper, we present a Generalized Likelihood Ratio (GLR) detector for detecting a moving target in presence of Gaussian interference and evaluate its performance in presence of different types of clutter distribution and target fluctuation. We assume three scenarios for detecting a fluctuating target in the presence of four different distributions of clutter; Rayleigh, Log-normal, Weibull and K-compound. In the first scenario, we consider the RCS's of target are constant subcarrier to subcarrier and pulse to pulse in a burst of pulses while they are varying fast according to Chi-square probability density function (swerling case II) burst to burst. In the second scenario, we assume that the RCS of target varies slowly according to Chi-square probability density function (swerling case I) subcarrier to subcarrier and they are constant pulse to pulse in a burst of pulses while they are varing fast according to Chi-square probability density function burst to burst. And in the third scenario, we assume the scattering coefficients of target are varing fast subcarrier to subcarrier and burst to burst, while they are constant pulse to pulse in a burst of pulses. We provide a few numerical examples to illustrate the detection performance of moving target under conditions of three scenarios, fluctuating models and different distributions of clutter and demonstrate the achieved performance improvement due to the OFDM signaling.     

Dynamic response analysis of wind turbines under blade pitch system fault,grid loss,and shutdown events

This study focuses on the dynamic responses of land‐based and floating wind turbines under blade pitch system fault and emergency shutdown conditions. The NREL 5 MW turbine is studied. A hydraulic pitch system is considered, and the faults under study are events with a seized blade or a blade running out of control. Emergency shutdown is defined as a fast pitch‐to‐feather maneuver of the blades. Load cases with power production and grid fault with ensuing shutdown are also analysed for comparison. The fault scenarios and the blades' fast pitching activity are simulated using HAWC2 through external Dynamic Link Libraries. On the basis of the time‐domain simulations, the response characteristics of the land‐based and the floating turbines in the four design load cases are compared. The load effects from the fault conditions are compared with the operational cases. Strong system dynamics and resonant responses, such as the tower elastic mode and the yaw resonant response, are elicited during shutdown. If the pitch system has a fault and one blade is hindered from normal pitching, the uneven load distribution of the blades leads to large structural and motion responses. For both turbines, the response maxima vary cyclically with the instantaneous azimuth when the blades start pitching to feather. For the floating wind turbine, the interaction of waves and wind also affects the results. The effect of the pitch rate during shutdown is analysed. The responses of the land‐based turbine in grid loss and shutdown conditions are proportional to the pitch rate, whereas decreased sensitivity is found in the cases with pitch system faults. For the floating turbine, the effect of the pitch rate is small, and reduced pitch and yaw motion extremes are observed as the pitch rate increases. Copyright © 2013 John Wiley & Sons, Ltd.     

A comparative study between experimentally measured mechanical attributes and users’ perception of soft feel coatings: Correlating human sense with surface characteristics of polyurethane based coatings

Different soft feel coating formulations using waterborne resins composed of soft and hard polyurethane resins were prepared. The effects of resins mixtures on the soft feel properties were studied. Attempts were made to find out the correlation between users perception and experimentally measured surface characteristics of the coatings. To this end, 72 people were asked to touch the coatings in a similar testing environment and to express their feeling in order to rank them between 1 (lowest soft feel effect) and 4 (highest soft feel effect). The coatings physical characteristics were studied by tensile test, micro Vickers hardness, atomic force microscope (AFM) and friction coefficient measurement. It was shown that the mixtures of 25:75 of soft and hard resins resulted in the best soft feel effect. Users did not consider low or high hardness films as soft. Instead, those coatings having greater toughness were ranked as the best soft feel effect. Also, coatings with lower friction coefficient and lower surface roughness were preferred by users. However, the lowest friction coefficient did not result in the best soft feel appeal. In fact, the mechanical properties, surface roughness and friction coefficient were found to play as the criteria to show soft feel effect. It is thus concluded that by selecting appropriate surface characteristics of coatings related to soft feel effect, good agreement between these properties and human feeling can be made.     

Wireless amperometric neurochemical monitoring using an integrated telemetry circuit

An integrated circuit for wireless real-time monitoring of neurochemical activity in the nervous system is described. The chip is capable of conducting high-resolution amperometric measurements in four settings of the input current. The chip architecture includes a first-order Delta Sigma modulator (Delta Sigma M) and a frequency-shift-keyed (FSK) voltage-controlled oscillator (VCO) operating near 433 MHz. It is fabricated using the AMI 0.5 microm double-poly triple-metal n-well CMOS process, and requires only one off-chip component for operation. Measured dc current resolutions of approximately 250 fA, approximately 1.5 pA, approximately 4.5 pA, and approximately 17 pA were achieved for input currents in the range of +/-5, +/-37, +/-150, and +/-600 nA, respectively. The chip has been interfaced with a diamond-coated, quartz-insulated, microneedle, tungsten electrode, and successfully recorded dopamine concentration levels as low as 0.5 microM wirelessly over a transmission distance of approximately 0.5 m in flow injection analysis experiments.     

Modified three rail shear fixture (ASTM D 4255/D 4255M) and an experimental study of nonlinear in-plane shear behaviour of FRC

In order to understand the nature of nonlinearity in the in-plane shear behaviour of fibre reinforce composites (FRC), experimental data of such materials under loading cycles, involving loading, unloading, reversed loading and unloading from reversed loading, are essential. Using the standard ASTM D 4255/D 4255 M method, it will require the fixture to be subjected to tension as well as compression. It has been proven in this paper that the standard ASTM D 4255/D 4255 M fixture is incapable of delivering such data as premature buckling is expected when the fixture is under tension, even though it claimed that the fixture could be loaded in tension as well as in compression. A cyclic rail shear fixture (CRSF) as a modified version of ASTM D 4255/D 4255 M fixture has been proposed in this paper and it has been designed and manufactured. The new fixture, which maintains all the capabilities of its standard counterpart, is truly capable of sustaining loading in tension as well as in compression so that specimens can be tested for loading and reversed loading. A series of experiments have been carried out using the new fixture to characterise the nonlinear in-plane shear stress–strain relationship of unidirectional fibre reinforced composite specimens under various cyclic loading conditions. Some new experimental data of this nature are presented in this paper, which are novel in contents and crucial in guiding the formulation of theoretical models for the nonlinear behaviour of in-plane shear for general applications.     

Using UV pretreatment to enhance biofiltration of mixtures of aromatic VOCs

Mixtures of airborne toluene and o-xylene, two relatively recalcitrant volatile organic compounds (VOCs), were treated effectively using integrated UV-biofiltration. The set-up consisted of a biofilter receiving UV-pretreated stream and a reference biofilter receiving no pretreatment. Experimental conditions included UV fluences of 6 and 12 mJcm(-2) as well as air flow rates of 6.3 and 9.4 Lmin(-1), corresponding to biofilter empty bed retention times (EBRTs) of 45 and 30s, respectively. The inlet concentration of organics (toluene and o-xylene) ranged between 70 and 650 mg(carbon)m(-3). The UV-biofilter consistently provided removal efficiencies of greater than 95% over the range of toluene and o-xylene inlet concentrations. Also, the coupled UV-biofiltration system provided up to 60% additional contaminant removal compared to the sum of that offered by UV and reference biofilter, demonstrating the synergistic effect of UV on biofilter performance. The UV photooxidation partially oxidized a fraction of toluene and o-xylene into water soluble and more biodegradable intermediates, such as acetaldehyde and formaldehyde, which were readily removed in the downstream biofilter. These intermediates along with up to 20ppmv ozone, formed through the photolysis of oxygen by 185 nm UV, contributed to the enhanced degradation of parent VOCs in the biofilter as well as the absence of any inhibitory effects of the VOCs on one another. Also, the presence of ozone helped control the growth of excess biofilm in the UV-coupled biofilter. While the standalone biofilter showed significant pressure drop increase (of up to 14 mm H(2)Om(-1) of the bed) over the course of experiment, the UV-coupled biofilter maintained a relatively low pressure drop of less than 3 mmH(2)Om(-1) of the bed.     

Impact of UV/H(2)O(2) advanced oxidation treatment on molecular weight distribution of NOM and biostability of water

The presence of natural organic matter (NOM) poses several challenges to the commercial practice of UV/H₂O₂ process for micropollutant removal. During the commercial application of UV/H₂O₂ advanced oxidation treatment, NOM is broken down into smaller species potentially affecting biostability by increasing Assimilable Organic Carbon (AOC) and Biodegradable Organic Carbon (BDOC) of water. This work investigated the potential impact of UV/H₂O₂ treatment on the molecular weight distribution of NOM and biostability of different water sources. A recently developed flow cytometric method for enumeration of bacteria was utilized to assess biological stability of the treated water at various stages through measurement of AOC. BDOC was also assessed for comparison and to better study the biostability of water. Both AOC and BDOC increased by about 3-4 times over the course of treatment, indicating the reduction of biological stability. Initial TOC and the source of NOM were found to be influencing the biostability profile of the treated water. Using high performance size exclusion chromatography, a wide range of organic molecule weights were found responsible for AOC increase; however, low molecular weight organics seemed to contribute more. Positive and meaningful correlations were observed between BDOC and AOC of different waters that underwent different treatments.     

Superacidic Catalyst Containing Phosphotungstic Acid Covalently Embedded Into Silica Matrix

Silicon - Homogeneous acidic catalysts of many industrial processes cause a multitude of problems such as production of toxic waste, hazards to workers, and corrosion of expensive equipment. These...