A series of microwave resonant oscillator sensors were designed and characterized using bandpass planar and volumetric electrical resonators having loaded quality factor (Q) values in the range of 2 to 20. The use of these resonators in positive feedback circuits yielded sensor Q-factors of up to 2 × 107, demonstrating Q-factor amplifications on the order of 106. It is shown that the Q-factor amplification can be increased in a positive feedback system through the selection of feedback loop group delay, allowing use of resonators with lower static, loaded Q-factor values. A low-frequency electromagnetic interference sensing application is demonstrated for two resonant oscillator configurations, showing considerable frequency sensitivity to 45 kHz emitters.

A prototype regenerative feedback resonant circuit has been developed for measuring the transient spectral response due to perturbations in properties of various electromagnetic materials. The circuit can accommodate a variety of cavity resonators, shown here in the 8 GHz range, with passive quality factors (Qstat) as high as 7000 depending upon material loading. The positive feedback enhanced dynamic quality factors (Qdyn) of resonator∕material combinations in the regenerative circuit are on the order of 10(7)-10(8). The theory, design, and implementation of the circuit is discussed along with real-time monitored example measurements of effects due to photon-induced charge carriers in high-resistivity silicon wafers and magnetic-field induced perturbations of yttrium-iron garnet.

We present a novel architecture based upon a Dicke-switched heterodyne radiometer architecture employing two identical input sections consisting of horn and orthomode transducer to detect the difference between the horizontal (H) and vertical (V) polarization states of two separate object patches imaged by the radiometer. We have constructed and described previously a fully polarimetric W-band passive millimeter wave imager constructed to study the phenomenology of anomaly detection using polarimetric image exploitation of the Stokes images. The heterodyne radiometer used a PIN diode switch between the input millimeter wave energy and that of a reference load in order to eliminate the effects of component drifts and to reduce the effects of 1/f noise. The differential approach differs from our previous work by comparing H and V polarization states detected by each of two input horns instead of a reference load to form signals Delta H and Delta V from adjacent paired object patches. This novel imaging approach reduces common mode noise and enhances detection of small changes between the H and V polarization states of two object patches, now given as difference terms of the fully polarimetric radiometer. We present the theory of operation, initial proof of concept experimental results, and extension of the differential radiometer to a system with a binocular fore optics that allow adjustment of the convergence or shear of the object patches as viewed by the differential polarimetric imager.

Raman spectroscopy has been shown to be a viable method for explosives detection. Currently most forensic Raman systems are either large, powerful instruments for laboratory experiments or handheld instruments for in situ point detection. We have chosen to examine the performance of certain benchtop Raman probe systems with the goal of developing an inexpensive, portable system that could be used to operate in a field forensics laboratory to examine explosives-related residues or samples. To this end, a rugged, low distortion line imaging dispersive Raman spectrograph was configured to work at 830 nm laser excitation and was used to determine whether the composition of thin films of plastic explosives or small (e.g., ≤10 μ m) particles of RDX or other explosives or oxidizers can be detected, identified, and quantified in the field. With 300 mW excitation energy, concentrations of RDX and PETN can be detected and reconstructed in the case of thin Semtex smears, but further work is needed to push detection limits of areal dosages to the ~1 μ g/cm 2 level. We describe the performance of several probe/spectrograph combinations and show preliminary data for particle detection, calibration and detection linearity for mixed compounds, and so forth.

As millimeter-wave arrays become available, off-axis imaging performance of the fore optics increases in importance due to the relatively large physical extent of the arrays. Typically, simple optical telescope designs are adapted to millimeter-wave imaging but single-mirror spherical or classic conic designs cannot deliver adequate image quality except near the optical axis. Since millimeter-wave designs are quasi-optical, optical ray tracing and commercial design software can be used to optimize designs to improve off-axis imaging as well as minimize cross-polarization. Methods that obey the Dragone-Mizuguchi condition for the design of reflective millimeter-wave telescopes with low cross-polarization also provide additional degrees of freedom that offer larger fields of view than possible with single-reflector designs. Dragone's graphical design method does not lend itself readily to computer-based optical design approaches, but subsequent authors expanded on Dragone's geometric design approach with analytic expressions that describe the location, shape, off-axis height and tilt of the telescope elements that satisfy Dragone's design rules and can be used as a first-order design for subsequent computer-based design and optimization. We investigate two design variants that obey the Dragone-Mizuguchi conditions that exhibit ultra-low cross-polarization and a large diffraction-limited field of view well suited to millimeter-wave imaging arrays.

Covers iOS5 Sams Teach Yourself iPad 2 in 10 Minutes, Third Edition offers straightforward, practical answers when you need fast results. By working through 10-minute lessons, youll learn everything you need to use your iPad 2 to get online, get apps, use the Web, manage email, books, photos, music, videoanything! Each compact lesson zeroes in on essential techniques, with fast, step-by-step instructions that help you do it right the first time! Tips point out shortcuts and solutions Cautions help you avoid common pitfalls Notes provide additional information 10 minutes is all you need to learn how to Use FaceTime for personal video phone calls and conferences Take photos and make video clips with the front-facing and rear-facing cameras Manage settings for the iPad 2 and customize it to suit your needs Hook up to external devices such as a camera, a presentation screen, TV, or HDTV Use Safari to access the Web, including your bookmarked and favorite sites Use the Mail app to read, send, and manage your email Manage personal information with the Calendar, Contacts, and Notes apps Subscribe to and read digital versions of magazines and newspapers Watch videos, TV shows, and movies on your iPad 2 Use iBooks and the iBooks Store to browse, buy, download, and read digital books Get and play music on the iPad 2 from iTunes and other sources Use Messages to have real-time text discussions with friends and family Learn about new features to iOS 5, including iCloud, Photo Booth, and more Category: iPad Covers: Apple Digital Media User Level: Beginning

This report describes research and development efforts toward a novel passive millimeter-wave (mm-wave) electromagnetic imaging device for broad-area search. It addresses the technical challenge of detecting anomalies that occupy a small fraction of a pixel. The purpose of the imager is to pinpoint suspicious locations for cuing subsequent higher-resolution imaging. The technical basis for the approach is to exploit thermal and polarization anomalies that distinguish man-made features from natural features.

We present experimental results obtained from a scanning passive W-band fully polarimetric imager. Passive millimeter wave imaging offers persistent day/nighttime imaging and the ability to penetrate dust, clouds and other obscurants, as well as thin layers of clothing and even dry soil. The selection of the W-band atmospheric window at 94 GHz offers a compromise as there is sufficient angular resolution for imaging applications using modestly-sized reflectors appropriate for mobile as well as fixed location applications. The imager is based upon an F/2.1 off-axis parabolic reflector that exhibits -34 dB of cross polarization suppression. The heterodyne radiometer produces a 6 GHz IF with 4 GHz of bandwidth resulting in an NEDT of < 200 mK. Polarimetric imaging reveals the presence of man-made objects due to their typically anisotropic nature and the interaction of these objects with incident millimeter wave radiation. The phenomenology studies were undertaken to determine the richest polarimetric signals to use for exploitation. In addition to a conventional approach to polarimetric image analysis in which the Stokes I, Q, U, and V images were formed and displayed, we present an alternative method for polarimetric image exploitation based upon multivariate image analysis (MIA). MIA uses principal component analysis (PCA) and 2D scatter or score plots to identify various pixel classes in the image compared with the more conventional scene-based image analysis approaches. Multivariate image decomposition provides a window into the complementary interplay between spatial and statistical correlations contained in the data.

We have used scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) to study compositional homogeneity at several stages in the processing of powders to the Ba2YCu3Ox high Tc superconductor. We investigated the effects of solution pH and ionic concentration in the precipitation preparation of mixed hydroxycarbonates of Ba, Y, and Cu as precursor to the Ba2YCu3O7−x high Tc superconductor. Our results show that both powder homogeneity and particle morphology are strongly dependent on these parameters. Additionally, studies of the compacted powders by EDS mapping at successive stages of processing show the development of phase inhomogeneities even in homogeneous starting powders.

The effect of increasing primary amine hydrocarbon chain length on the SCR of NOx from diesel engine exhaust was investigated and compared to ammonia. Methylamine (CH3NH2), ethylamine (CH3CH2NH2), propylamine (CH3CH2CH2NH2) and butylamine (CH3CH2CH2CH2NH2) were tested using a 12 cell mini core NH3 - SCR catalyst cut from a 400 cpsi block. There is a steady decrease in NOx conversion as the length of the hydrocarbon chain increases (from 50% for methylamine to 26% for butylamine). For the same number of carbons in the amine, primary amines are more active reductants than methyl substituted secondary or tertiary amines. For example, ethylamine (NOx conversion of 45%) is more active than dimethylamine (NOx conversion of 34%).Since the amines are reactive in the gas phase in the temperature range of diesel engine exhaust, gas phase conversions were estimated by replacing the mini core SCR catalyst with an equivalent length of quartz beads. There was no smooth transition in gas phase NO and NOx conversions with increasing hydrocarbon chain length. The results suggest a different mechanism for gas phase reactions depending on the nature of the amine. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.

A new concept for radiation detection is proposed, allowing a decoupling of the sensing medium and the readout. An electromagnetic material, such as a magnetic ceramic ferrite, is placed near a source to be tracked such as a shipping container. The electromagnetic material changes its properties, in this case its magnetic permeability, as a function of radiation. This change is evident as a change in reflection frequency and magnitude when probed using a microwave/millimeter-wave source. This brief report discusses modeling of radiation interaction of various candidate materials using a radiation detector modeling code Geant4, system design considerations for the remote readout, and some theory of the material interaction physics. The theory of radiation change in doped magnetic insulator ferrites such as yttrium iron garnet (YIG) seems well founded based on literature documentation of the photomagnetic effect. The literature also suggests sensitivity of permittivity to neutrons in some ferroelectrics. Research to date indicates that experimental demonstration of these effects in the context of radiation detection is warranted.

Titania–alumina mixed oxide was synthesized hydrothermally using tetrapropylammonium hydroxide (TPAOH) as the template. The dried, calcined and palladium loaded samples were characterized for particle morphology, weight loss, nitrogen adsorption/desorption at liquid nitrogen temperature, texture and metal dispersion. The Pd loaded material was tested for NO reduction in a fixed bed catalytic reactor using a simulated gas mixture closely resembling lean burn engine exhaust. Scanning electron microscopy of the dried and calcined samples revealed a well developed tubular fibrous network of titania–alumina. Thermogravimetry (TG) of the dried sample indicated about 16% weight loss due to decomposition of an oxy-hydroxide structure of the material, mostly boehmite, which was confirmed by X-ray diffraction (XRD) measurements. The boehmite phase changed to poorly crystalline γ-alumina upon calcination where as titania remained as anatase. BET specific surface area, adsorption–desorption isotherms and BJH pore size distributions indicated formation of a mesoporous structure. The surface area of the dried material increased when calcined at 600 °C but the pore size distribution patterns for the dried, calcined and palladium dispersed materials remained unchanged. These observations along with TG and XRD analyses suggest that a thermo-resistant, mesoporous, high surface area, crystalline titania–alumina framework can be prepared using the hydrothermal synthesis route. A peak NOx conversion of 75% with the palladium dispersed catalyst indicates high catalytic activity, possibly due to high dispersion of Pd confirmed by CO chemisorption studies.

With a view to developing onboard generation of selective reductants for NO, removal from diesel engine exhaust we compared the performance of a primary, secondary and tertiary amine to NH3 using a typical mini core NH3-SCR catalyst. Primary amines with short hydrocarbon chains, e.g. CH3NH2 (maximum NOx conversion, 50%) approached the NOx conversion obtained using NH3 (maximum NOx conversion, 70%). Increasing the amine to NOx ratio greater than I results in NOx conversions closer to those of NH3 (maximum NOx conversion increased to 60%). Secondary and tertiary amines had smaller NOx conversions as a function of temperature and the drop in NO and NOx conversion decreased with increasing amine hydrogen substitution. Also, the maximum NOx conversion for each reductant tends to move to a lower temperature as the degree of substitution increases.Unlike NH3, the amines can react in the gas phase at temperatures within the range of diesel engine exhaust. Due to this gas phase reactivity the NOx conversions measured using the mini core SCR catalyst also contain a gas phase conversion component. Gas phase conversions were investigated by replacing the mini core SCR catalyst with an equivalent length of quartz beads. Subtraction of the two results highlighted the differences between the mini core catalytic and gas phase conversions measured in this manner over the temperature range investigated. These differential NOx conversions for the three amines had maxima at about 375 degrees C. (c) 2006 Elsevier Ltd. All rights reserved.

A radio frequency characterization of a split-ringed, electro-optical modulator (EOM) is provided herein. This characterization is given in terms of electromagnetic simulation data, as obtained from a finite-difference, time-domain code, and a lumped element circuit model. The simulation data provides insight into the field structure within the cavity; the circuit model provides a simple, yet accurate set of design and analysis formulas that relate resonant frequency, voltage levels and power levels to the geometrical and material parameters of the cavity. To validate the claims made from the simulation data and circuit model, experimental data is also provided and a favorable comparison among all data sets is shown. It is concluded that the cavity under consideration can be made to resonate at low frequencies, without increasing the overall size of the cavity. Even though the price in doing so is a reduction in cavity Q and electro-optical crystal voltage, this split-ringed EOM is well suited to an efficient thermal management scheme. Guidance is given on how to optimize the cavity in terms of voltage, Q, power levels, and voltage levels.

A continuous short contact time thermal cracker was constructed and operated to investigate the production of alpha olefins in the C9–C16 range. Alpha olefins in this range are normally used as chemical feedstocks for lubricants, surfactants, alcohols and other valuable commodities. The CETC unit was operated at 100 g h−1 between 495 and 570°C using paraffin wax, waste wax from a gold refinery, waste plastic-derived oil and topped waste plastic-derived (wax enriched) oil. The effect of operating temperature, heavy ends recycle rate and feed types on the production of alpha olefins was examined in detail. It was found that the concentration of heavy paraffins with carbon numbers greater than C16 in the heavy ends recycle stream is a good indicator for estimating the concentration of alpha olefins in the C9–C16 range. It was shown that feed type is the most critical factor in determining high alpha olefins yield in this range. Following is the order of suitability for producing alpha olefins in the C9–C16 range: paraffin wax>plastic-derived oil (topped)>plastic-derived oil (as received)>waste wax.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSelective oil agglomeration of lignite using vacuum bottoms only as an integral part of coprocessingMichio Ikura, James F. Kelly, and C. Edward CapesCite this: Energy Fuels 1989, 3, 2, 132–136Publication Date (Print):March 1, 1989Publication History Published online1 May 2002Published inissue 1 March 1989https://pubs.acs.org/doi/10.1021/ef00014a004https://doi.org/10.1021/ef00014a004research-articleACS PublicationsRequest reuse permissionsArticle Views63Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts