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Sample records for monoxide non-uniform behaviour

  1. A generic Approach for Reliability Predictions considering non-uniformly Deterioration Behaviour

    NASA Astrophysics Data System (ADS)

    Krause, Jakob; Kabitzsch, Klaus

    2012-05-01

    Predictive maintenance offers the possibility to prognosticate the remaining time until a maintenance action of a machine has to be scheduled. Unfortunately, current predictive maintenance solutions are only suitable for very specific use cases like reliability predictions based on vibration monitoring. Furthermore, they do not consider the fact that machines may deteriorate non-uniformly, depending on external influences (e.g., the work piece material in a milling machine or the changing fruit acid concentration in a bottling plant). In this paper two concepts for a generic predictive maintenance solution which also considers non-uniformly aging behaviour are introduced. The first concept is based on system models representing the health state of a technical system. As these models are usually statically (viz. without a timely dimension) their coefficients are determined periodically and the resulting time series is used as aging indicator. The second concept focuses on external influences (contexts) which change the behaviour of the previous mentioned aging indicators in order to increase the accuracy of reliability predictions. Therefore, context-depended time series models are determined and used to predict machine reliability. Both concepts were evaluated on data of an air ventilation system. Thereby, it could be shown that they are suitable to determine aging indicators in a generic way and to incorporate external influences in the reliability prediction. Through this, the quality of reliability predictions can be significantly increased. In reality this leads to a more accurate scheduling of maintenance actions. Furthermore, the generic character of the solutions makes the concepts suitable for a wide range of aging processes.

  2. Risk and protective behaviours for residential carbon monoxide poisoning

    PubMed Central

    Rupert, Douglas J; Poehlman, Jon A; Damon, Scott A; Williams, Peyton N

    2015-01-01

    Background Unintentional, non-fire-related carbon monoxide (CO) poisoning is a leading cause of poisoning death and injury in the USA. Residential poisonings caused by faulty furnaces are the most common type of CO exposure. However, these poisonings are largely preventable with annual furnace inspections and CO alarm installation. Objective This study aimed to identify the knowledge, attitudes and beliefs that might lead consumers to adopt these protective behaviours. Methods In August 2009, four focus groups (n=29) were conducted with homeowners in Chicago, Illinois, USA, to identify the knowledge, attitudes and beliefs that lead consumers to adopt risk and protective behaviours. Discussions were transcribed and the findings were analysed using an ordered meta-matrix. Results Focus group participants were aware of CO poisoning and supported the idea of regular furnace inspections. However, few participants consistently scheduled professional inspections for fear of costly repairs and unscrupulous contractors. Participants often owned CO alarms, but many did not locate them properly, nor maintain them. Some participants confused CO and natural gas and were unsure how to react if a CO alarm sounds. Participants stated that incentives, such as discounts and inspector selection tips, would make them more likely to schedule furnace inspections. Participants also identified trustworthy sources for CO education, including realtors, fire departments, home insurance agents and local media outlets. Conclusions Participants’ residential CO risk behaviours are not random but driven by underlying knowledge, attitudes and beliefs. Correcting misperceptions, providing incentives and partnering with trustworthy sources might encourage greater consumer adoption of protective behaviours. PMID:22653781

  3. Radionic Non-Uniform Black Strings

    NASA Astrophysics Data System (ADS)

    Tamaki, T.; Kanno, S.; Soda, J.

    Non-uniform black strings in the two-brane system are investigated using the effective action approach. It is shown that the radion acts as a non-trivial hair of black strings. The stability of solutions is demonstrated using the catastrophe theory. The black strings are shown to be non-uniform.

  4. Non-Uniform Thickness Electroactive Device

    NASA Technical Reports Server (NTRS)

    Su, Ji (Inventor); Harrison, Joycelyn S. (Inventor)

    2006-01-01

    An electroactive device comprises at least two layers of material, wherein at least one layer is an electroactive material and wherein at least one layer is of non-uniform thickness. The device can be produced in various sizes, ranging from large structural actuators to microscale or nanoscale devices. The applied voltage to the device in combination with the non-uniform thickness of at least one of the layers (electroactive and/or non-electroactive) controls the contour of the actuated device. The effective electric field is a mathematical function of the local layer thickness. Therefore, the local strain and the local bending/ torsion curvature are also a mathematical function of the local thickness. Hence the thinnest portion of the actuator offers the largest bending and/or torsion response. Tailoring of the layer thicknesses can enable complex motions to be achieved.

  5. The non-uniformity of fossil preservation.

    PubMed

    Holland, Steven M

    2016-07-19

    The fossil record provides the primary source of data for calibrating the origin of clades. Although minimum ages of clades are given by the oldest preserved fossil, these underestimate the true age, which must be bracketed by probabilistic methods based on multiple fossil occurrences. Although most of these methods assume uniform preservation rates, this assumption is unsupported over geological timescales. On geologically long timescales (more than 10 Myr), the origin and cessation of sedimentary basins, and long-term variations in tectonic subsidence, eustatic sea level and sedimentation rate control the availability of depositional facies that preserve the environments in which species lived. The loss of doomed sediments, those with a low probability of preservation, imparts a secular trend to fossil preservation. As a result, the fossil record is spatially and temporally non-uniform. Models of fossil preservation should reflect this non-uniformity by using empirical estimates of fossil preservation that are spatially and temporally partitioned, or by using indirect proxies of fossil preservation. Geologically, realistic models of preservation will provide substantially more reliable estimates of the origination of clades.This article is part of the themed issue 'Dating species divergences using rocks and clocks'. PMID:27325828

  6. Downsampling Non-Uniformly Sampled Data

    NASA Astrophysics Data System (ADS)

    Eng, Frida; Gustafsson, Fredrik

    2007-12-01

    Decimating a uniformly sampled signal a factor D involves low-pass antialias filtering with normalized cutoff frequency 1/ D followed by picking out every D th sample. Alternatively, decimation can be done in the frequency domain using the fast Fourier transform (FFT) algorithm, after zero-padding the signal and truncating the FFT. We outline three approaches to decimate non-uniformly sampled signals, which are all based on interpolation. The interpolation is done in different domains, and the inter-sample behavior does not need to be known. The first one interpolates the signal to a uniformly sampling, after which standard decimation can be applied. The second one interpolates a continuous-time convolution integral, that implements the antialias filter, after which every D th sample can be picked out. The third frequency domain approach computes an approximate Fourier transform, after which truncation and IFFT give the desired result. Simulations indicate that the second approach is particularly useful. A thorough analysis is therefore performed for this case, using the assumption that the non-uniformly distributed sampling instants are generated by a stochastic process.

  7. A non-uniform expansion mechanical safety model of the stent.

    PubMed

    Yang, J; Huang, N; Du, Q

    2009-01-01

    Stents have a serial unstable structure that readily leads to non-uniform expansion. Non-uniform expansion in turn creates a stent safety problem. We explain how a stent may be simplified to a serial unstable structure, and present a method to calculate the non-uniform expansion of the stent on the basis of the serial unstable structure. We propose a safety criterion based on the expansion displacement instead of the strain, and explain that the parameter Rd, the ratio of the maximum displacement of the elements to normal displacement, is meaningful to assess the safety level of the stent. We also examine how laser cutting influences non-uniform expansion. The examples illustrate how to calculate the parameter Rd to assess non-uniform expansion of the stent, and demonstrate how the laser cutting offset and strengthening coefficient of the material influence the stent expansion behaviour. The methods are valuable for assessing stent safety due to non-uniform expansion. PMID:19517292

  8. Non-uniform MR image reconstruction based on non-uniform FFT

    NASA Astrophysics Data System (ADS)

    Liang, Xiao-yun; Zeng, Wei-ming; Dong, Zhi-hua; Zhang, Zhi-jiang; Luo, Li-min

    2007-01-01

    A Non-Uniform Fast Fourier Transform (NUFFT) based method for non-Cartesian k-space data reconstruction is presented. For Cartesian K-space data, as we all know, image can be reconstructed using 2DFFT directly. But, as far as know, this method has not been universally accepted nowadays because of its inevitable disadvantages. On the contrary, non-Cartesian method is of the advantage over it, so we focused on the method usually. The most straightforward approach for the reconstruction of non-Cartesian data is directly via a Fourier summation. However, the computational complexity of the direct method is usually much greater than an approach that uses the efficient FFT. But the FFT requires that data be sampled on a uniform Cartesian grid in K-space, and a NUFFT based method is of much importance. Finally, experimental results which are compared with existing method are given.

  9. Non-uniform magnetization reversal in nanocomposite magnets

    NASA Astrophysics Data System (ADS)

    Li, Z. B.; Zhang, M.; Shen, B. G.; Sun, J. R.

    2013-03-01

    Magnetization reversal and exchange coupling are investigated in Pr-Fe-B melt-spun ribbons. In nanocomposite magnets, not only does the coercivity decrease but also magnetization reversal becomes more non-uniform in hard grains. The non-uniform magnetization reversal, resulting in a deterioration of squareness in hysteresis loop and a drop of the maximum Henkel plot value, mainly is caused by random arrangement of easy axes and intergranular soft regions among hard grains even with well exchange coupling between soft-hard grains in these ribbons. It is expected that the uniformity in magnetization reversal could be improved with the perfection of easy axes alignment in anisotropy nanocomposites.

  10. GaAs MESFET with lateral non-uniform doping

    NASA Technical Reports Server (NTRS)

    Wang, Y. C.; Bahrami, M.

    1983-01-01

    An analytical model of the GaAs MESFET with arbitrary non-uniform doping is presented. Numerical results for linear lateral doping profile are given as a special case. Theoretical considerations predict that better device linearity and improved F(T) can be obtained by using linear lateral doping when doping density increases from source to drain.

  11. A non-uniform warping theory for beams

    NASA Astrophysics Data System (ADS)

    El Fatmi, Rached

    2007-08-01

    This Note proposes a non-uniform warping beam theory including the effects of torsion and shear forces. Based on a displacement model using three warping parameters associated to three St Venant warping functions corresponding to torsion and shear forces, this theory is free from the classical assumptions on the warpings or on the shears, and is valid for any kind of homogeneous elastic and isotropic cross-section. The result on the structural behavior of the beam specifies the effect of the non-symmetry of the cross-section, and the closed form results obtained for the stresses show the contribution of each internal force. Comparison with St Venant beam theory highlights the additional effects due to the non-uniformity of the warping. To cite this article: R. El Fatmi, C. R. Mecanique 335 (2007).

  12. Effect of non-uniform exchange field in ferromagnetic graphene

    SciTech Connect

    Chowdhury, Debashree Basu, B.

    2015-04-15

    We have presented here the consequences of the non-uniform exchange field on the spin transport issues in spin chiral configuration of ferromagnetic graphene. Taking resort to the spin–orbit coupling (SOC) term and non-uniform exchange coupling term we are successful to express the expression of Hall conductivity in terms of the exchange field and SOC parameters through the Kubo formula approach. However, for a specific configuration of the exchange parameter we have evaluated the Berry curvature of the system. We also have paid attention to the study of SU(2) gauge theory of ferromagnetic graphene. The generation of anti damping spin–orbit torque in spin chiral magnetic graphene is also briefly discussed.

  13. A mechanical model of a non-uniform ionomeric polymer metal composite actuator

    NASA Astrophysics Data System (ADS)

    Anton, Mart; Aabloo, Alvo; Punning, Andres; Kruusmaa, Maarja

    2008-04-01

    This paper describes a mechanical model of an IPMC (ionomeric polymer metal composite) actuator in a cantilever beam configuration. The main contribution of our model is that it gives the most detailed description reported so far of the quasistatic mechanical behaviour of the actuator with non-uniform bending at large deflections. We also investigate a case where part of an IPMC actuator is replaced with a rigid elongation and demonstrate that this configuration would make the actuator behave more linearly. The model is experimentally validated with MuscleSheet™ IPMCs, purchased from BioMimetics Inc.

  14. Characterization of non-uniformly totally polarized beams

    NASA Astrophysics Data System (ADS)

    Martinez-Herrero, R.; Mejías, P. M.; Piquero, G.

    2006-02-01

    Several overall parameters are introduced to characterize the linear or circular polarization content of a non-uniformly totally polarized beam over the region of its wavefront where the irradiance is significant. These parameters are determined from the values of the Stokes parameters. Experimental examples are also given to check both, the physical meaning of the proposed parameters and the validity of the measurement procedure.

  15. A novel non-uniformity correction method based on ROIC

    NASA Astrophysics Data System (ADS)

    Chen, Xiaoming; Li, Yujue; Di, Chao; Wang, Xinxing; Cao, Yi

    2011-11-01

    Infrared focal plane arrays (IRFPA) suffer from inherent low frequency and fixed patter noised (FPN). They are thus limited by their inability to calibrate out individual detector variations including detector dark current (offset) and responsivity (gain). To achieve high quality infrared image by mitigating the FPN of IRFPAs, we have developed a novel non-uniformity correction (NUC) method based on read-out integrated circuit (ROIC). The offset and gain correction coefficients can be calculated by function fitting for the linear relationship between the detector's output and a reference voltage in ROIC. We tested the purposed method using an infrared imaging system using the ULIS 03 19 1 detector with real nonuniformity. A set of 384*288 infrared images with 12 bits was collected to evaluate the performance. With the experiments, the non-uniformity was greatly eliminated. We also used the universe non-uniformity (NU) parameter to estimate the performance. The calculated NU parameters with the two-point calibration (TPC) and the purposed method imply that the purposed method has almost as good performance as TPC.

  16. Naturalness preserved enhancement algorithm for non-uniform illumination images.

    PubMed

    Wang, Shuhang; Zheng, Jin; Hu, Hai-Miao; Li, Bo

    2013-09-01

    Image enhancement plays an important role in image processing and analysis. Among various enhancement algorithms, Retinex-based algorithms can efficiently enhance details and have been widely adopted. Since Retinex-based algorithms regard illumination removal as a default preference and fail to limit the range of reflectance, the naturalness of non-uniform illumination images cannot be effectively preserved. However, naturalness is essential for image enhancement to achieve pleasing perceptual quality. In order to preserve naturalness while enhancing details, we propose an enhancement algorithm for non-uniform illumination images. In general, this paper makes the following three major contributions. First, a lightness-order-error measure is proposed to access naturalness preservation objectively. Second, a bright-pass filter is proposed to decompose an image into reflectance and illumination, which, respectively, determine the details and the naturalness of the image. Third, we propose a bi-log transformation, which is utilized to map the illumination to make a balance between details and naturalness. Experimental results demonstrate that the proposed algorithm can not only enhance the details but also preserve the naturalness for non-uniform illumination images. PMID:23661319

  17. Immersed boundary method with non-uniform distribution of Lagrangian markers for a non-uniform Eulerian mesh

    NASA Astrophysics Data System (ADS)

    Akiki, G.; Balachandar, S.

    2016-02-01

    This study presents a technique to incorporate spheres in a channel flow that uses a non-uniform Eulerian grid using immersed boundary methods with direct forcing. An efficient algorithm is presented which distributes the Lagrangian markers non-uniformly to match the fluid grid and keep the number of markers optimized. Also a novel method to calculate the area weights of the Lagrangian markers is given. It is observed that even the best available algorithms for uniform distribution of markers on a sphere result in a finite error. Using vector spherical harmonics, this error is quantified and reduced to machine precision. A series of simulations of a stationary and moving sphere in a periodic channel at Reynolds number range of 1-100 are presented. Results for a sphere in an ambient shear flow in close proximity of a wall are also shown, where the present non-uniform distribution offers an order of magnitude reduction over uniform distribution of Lagrangian markers. Simulations of a random cluster of 640 monodisperse spherical particles show a 77% reduction in Lagrangian markers with an error of 0.135% in computing the total drag.

  18. Wave modeling in a cylindrical non-uniform helicon discharge

    SciTech Connect

    Chang, L.; Hole, M. J.; Caneses, J. F.; Blackwell, B. D.; Corr, C. S.; Chen, G.

    2012-08-15

    A radio frequency field solver based on Maxwell's equations and a cold plasma dielectric tensor is employed to describe wave phenomena observed in a cylindrical non-uniform helicon discharge. The experiment is carried out on a recently built linear plasma-material interaction machine: The magnetized plasma interaction experiment [Blackwell et al., Plasma Sources Sci. Technol. (submitted)], in which both plasma density and static magnetic field are functions of axial position. The field strength increases by a factor of 15 from source to target plate, and the plasma density and electron temperature are radially non-uniform. With an enhancement factor of 9.5 to the electron-ion Coulomb collision frequency, a 12% reduction in the antenna radius, and the same other conditions as employed in the experiment, the solver produces axial and radial profiles of wave amplitude and phase that are consistent with measurements. A numerical study on the effects of axial gradient in plasma density and static magnetic field on wave propagations is performed, revealing that the helicon wave has weaker attenuation away from the antenna in a focused field compared to a uniform field. This may be consistent with observations of increased ionization efficiency and plasma production in a non-uniform field. We find that the relationship between plasma density, static magnetic field strength, and axial wavelength agrees well with a simple theory developed previously. A numerical scan of the enhancement factor to the electron-ion Coulomb collision frequency from 1 to 15 shows that the wave amplitude is lowered and the power deposited into the core plasma decreases as the enhancement factor increases, possibly due to the stronger edge heating for higher collision frequencies.

  19. Non-uniform projection angle processing in computed tomography

    NASA Astrophysics Data System (ADS)

    Simo, Yanic; Tayag, Tristan J.

    In this paper, we present a novel approach for the collection of computed tomography data. Non-uniform increments in projection angle may be used to reduce data acquisition time with minimal reduction in the accuracy of the reconstructed profile. The key is to exploit those projection angles which correspond to regions where the object contains few high spatial frequency components. This technique is applicable to optical phase computed tomography, as well as X-ray computed tomography. We present simulation results on intraocular lenses used in cataract surgery.

  20. Electrostatic adhesion of multiple non-uniformly charged dielectric particles

    NASA Astrophysics Data System (ADS)

    Kemp, B. A.; Whitney, J. G.

    2013-01-01

    Charged particle adhesion measurements can be as much as one order of magnitude higher than theoretical calculations. This discrepancy has ignited a debate as to the nature of the physics occurring with microscopic particle adhesion. Attempts to bring calculations closer to measured results have produced models that include multiple particle interactions, dielectric polarization, and non-uniform charge. Individually, each of these models can only produce a 2× to 5× enhancement in predicted adhesion force over simple Coulombic attraction. In this correspondence, an analytical model of electrostatic particle forces is developed, which allows for independent assignment of dielectric constant and non-uniform surface charge distribution to an arbitrary number of particles. Because the model can include an image plane, it is ideal for electrostatic adhesion calculations. Application to a monolayer of printed toner particles predicts nearly an order of magnitude increase in adhesion force over Coulombic attraction. These results are the first analytical results to place predictions of charged particle adhesion on the same order of magnitude with measurements.

  1. A multilevel Cartesian non-uniform grid time domain algorithm

    SciTech Connect

    Meng Jun; Boag, Amir; Lomakin, Vitaliy; Michielssen, Eric

    2010-11-01

    A multilevel Cartesian non-uniform grid time domain algorithm (CNGTDA) is introduced to rapidly compute transient wave fields radiated by time dependent three-dimensional source constellations. CNGTDA leverages the observation that transient wave fields generated by temporally bandlimited and spatially confined source constellations can be recovered via interpolation from appropriately delay- and amplitude-compensated field samples. This property is used in conjunction with a multilevel scheme, in which the computational domain is hierarchically decomposed into subdomains with sparse non-uniform grids used to obtain the fields. For both surface and volumetric source distributions, the computational cost of CNGTDA to compute the transient field at N{sub s} observation locations from N{sub s} collocated sources for N{sub t} discrete time instances scales as O(N{sub t}N{sub s}logN{sub s}) and O(N{sub t}N{sub s}log{sup 2}N{sub s}) in the low- and high-frequency regimes, respectively. Coupled with marching-on-in-time (MOT) time domain integral equations, CNGTDA can facilitate efficient analysis of large scale time domain electromagnetic and acoustic problems.

  2. Supernova remnant evolution in non-uniform media

    NASA Astrophysics Data System (ADS)

    Ferreira, S. E. S.; de Jager, O. C.

    In this work numerical simulations showing the time evolution of a supernova remnant (SNR) in an uniform and non-uniform intersteller medium (ISM) are presented. For this we use a hydrodynamic model including a kinematic calculation of the interstellar magnetic field. Important parameters include the ejecta mass and energy of the remnant, as well as interstellar medium density and adiabatic index. By varying these we constructed an analytical expression giving the return time of the reverse shock to the origin. We also computed the evolution of the remnant in non-uniform media. As the SNR evolves from one into another medium of higher density a reflection shock is created which is driven back toward the center. As the reflection shock moves inward it also drags some of the compressed ISM field lines with it and heats the inside of the SNR. When a SNR explodes in a medium with a high density and the blast waves propagate into a medium with a lower density a cavity is being blown away changing the geometry of the high density region. Also, once the forward shock moves into the medium of less density, a second reverse shock will start to form in this region.

  3. Evaluating AIRS Radiometric Error in Non-uniform Scenes using MODIS

    NASA Astrophysics Data System (ADS)

    Pagano, T. S.; Aumann, H. H.

    2014-12-01

    The Atmospheric Infrared Sounder (AIRS) on the EOS Aqua Spacecraft was launched on May 4, 2002. AIRS acquires hyperspectral infrared radiances in 2378 channels ranging in wavelength from 3.7-15.4 um with spectral resolution of better than 1200, and spatial resolution of 13.5 km with global daily coverage. The AIRS was designed to measure temperature and water vapor profiles for improvement in weather forecast and improved parameterization of climate processes. Currently the AIRS Level 1B Radiance Products are assimilated by NWP centers worldwide and have shown considerable forecast improvement. AIRS L1 and L2 products are widely used for studying critical climate processes related to water vapor feedback, atmospheric transport and cloud properties. AIRS trace gas products include ozone profiles, carbon monoxide, and the first global maps of mid-tropospheric carbon dioxide. The AIRS radiances are calibrated using a uniform on-board blackbody and full aperture space view. For this reason, all radiometric measurements assume a uniform scene. As with most instruments, the AIRS 2D spatial response functions (tophat functions) are not flat for all channels, nor are they the same. When viewing a non-uniform scene, this causes a radiometric error that is scene dependent and cannot be removed without knowledge of the scene response. The magnitude of the error depends on the non-uniformity of the AIRS spatial response and the non-uniformity of the scene, but typically only affects about 1% of the data. In this effort we use data from the MODIS instrument to provide information on the scene uniformity that can be used to correct the AIRS data. Early results show we can match the AIRS and MODIS radiances to about 0.6K when we include the AIRS tophat functions in the normalization of the MODIS data (Elliott, Proc SPIE 6296, 2006). The method requires use of different infrared bands in MODIS depending on the channels of AIRS being corrected. Resulting improvement in noise and

  4. Periodic envelopes of waves over non-uniform depth

    NASA Astrophysics Data System (ADS)

    Rajan, Girish K.; Bayram, Saziye; Henderson, Diane M.

    2016-04-01

    The envelope of narrow-banded, periodic, surface-gravity waves propagating in one dimension over water of finite, non-uniform depth may be modeled by the Djordjević and Redekopp ["On the development of packets of surface gravity waves moving over an uneven bottom," Z. Angew. Math. Phys. 29, 950-962 (1978)] equation (DRE). Here we find five approximate solutions of the DRE that are in the form of Jacobi-elliptic functions and discuss them within the framework of ocean swell. We find that in all cases, the maximum envelope-amplitude decreases/increases when the wave group propagates on water of decreasing/increasing depth. In the limit of the elliptic modulus approaching one, three of the solutions reduce to the envelope soliton solution. In the limit of the elliptic modulus approaching zero, two of the solutions reduce to an envelope-amplitude that is uniform in an appropriate reference frame.

  5. Effect on Non-Uniform Heat Generation on Thermionic Reactions

    SciTech Connect

    Schock, Alfred

    2012-01-19

    The penalty resulting from non-uniform heat generation in a thermionic reactor is examined. Operation at sub-optimum cesium pressure is shown to reduce this penalty, but at the risk of a condition analogous to burnout. For high pressure diodes, a simple empirical correlation between current, voltage and heat flux is developed and used to analyze the performance penalty associated with two different heat flux profiles, for series-and parallel-connected converters. The results demonstrate that series-connected converters require much finer power flattening than parallel converters. For example, a ±10% variation in heat generation across a series array can result in a 25 to 50% power penalty.

  6. Coupled Serial and Parallel Non-uniform SQUIDs

    SciTech Connect

    Longhini, Patrick; In, Visarath; Berggren, Susan; Palacios, Antonio; Leese de Escobar, Anna

    2011-04-19

    In this work we numerical model series and parallel non-uniform superconducting quantum interference device (SQUID) array. Previous work has shown that series SQUID array constructed with a random distribution of loop sizes, (i.e. different areas for each SQUID loop) there exists a unique 'anti-peak' at the zero magnetic field for the voltage versus applied magnetic field (V-B). Similar results extend to a parallel SQUID array where the difference lies in the arrangement of the Josephson junctions. Other system parameter such as bias current, the number of loops, and mutual inductances are varied to demonstrate the change in dynamic range and linearity of the V-B response. Application of the SQUID array as a low noise amplifier (LNA) would increase link margins and affect the entire communication system. For unmanned aerial vehicles (UAVs), size, weight and power are limited, the SQUID array would allow use of practical 'electrically small' antennas that provide acceptable gain.

  7. Single image non-uniformity correction using compressive sensing

    NASA Astrophysics Data System (ADS)

    Jian, Xian-zhong; Lu, Rui-zhi; Guo, Qiang; Wang, Gui-pu

    2016-05-01

    A non-uniformity correction (NUC) method for an infrared focal plane array imaging system was proposed. The algorithm, based on compressive sensing (CS) of single image, overcame the disadvantages of "ghost artifacts" and bulk calculating costs in traditional NUC algorithms. A point-sampling matrix was designed to validate the measurements of CS on the time domain. The measurements were corrected using the midway infrared equalization algorithm, and the missing pixels were solved with the regularized orthogonal matching pursuit algorithm. Experimental results showed that the proposed method can reconstruct the entire image with only 25% pixels. A small difference was found between the correction results using 100% pixels and the reconstruction results using 40% pixels. Evaluation of the proposed method on the basis of the root-mean-square error, peak signal-to-noise ratio, and roughness index (ρ) proved the method to be robust and highly applicable.

  8. Compensation for non-uniform attenuation in SPECT brain imaging

    SciTech Connect

    Glick, S.J.; King, M.A.; Pan, T.S.

    1994-05-01

    Photon attenuation is a major limitation in performing quantitative SPECT brain imaging. A number of methods have been proposed for compensation of attenuation in regions of the body that can be modelled as a uniform attenuator. The magnitude of the errors introduced into reconstructed brain images by assuming the head to be a uniform attenuator are uncertain (the skull, sinus cavities and head holder all have different attenuation properties than brain tissue). Brain imaging is unique in that the radioisotope, for the most part, is taken up within a uniform attenuation medium (i.e., brain tissue) which is surrounded by bone (i.e., the skull) of a different density. Using this observation, Bellini`s method for attenuation compensation (which is an exact solution to the exponential Radon transform) has been modified to account for the different attenuation properties of the skull. To test this modified Bellini method, a simple mathematical phantom was designed to model the brain and a skull of varying thickness less than 7.5 mm. To model brain imaging with Tc-99m HMPAO, the attenuation coefficient of the brain tissue and skull were set to 0.15 cm{sup -1} and 0.22 cm{sup -1} respectively. A ray-driven projector which accounted for non-uniform attenuation was used to simulate projection data from 128 views. The detector response and scatter were not simulated. It was observed that reconstructions processed with uniform attenuation compensation (i.e., where it was assumed that the brain tissue and the skull had the same attenuation coefficient) provided errors of 6-20%, whereas those processed with the non-uniform Bellini algorithm were biased by only 0-5%.

  9. Restoration of non-uniform exposure motion blurred image

    NASA Astrophysics Data System (ADS)

    Luo, Yuanhong; Xu, Tingfa; Wang, Ningming; Liu, Feng

    2014-11-01

    Restoring motion-blurred image is the key technologies in the opto-electronic detection system. The imaging sensors such as CCD and infrared imaging sensor, which are mounted on the motion platforms, quickly move together with the platforms of high speed. As a result, the images become blur. The image degradation will cause great trouble for the succeeding jobs such as objects detection, target recognition and tracking. So the motion-blurred images must be restoration before detecting motion targets in the subsequent images. On the demand of the real weapon task, in order to deal with targets in the complex background, this dissertation uses the new theories in the field of image processing and computer vision to research the new technology of motion deblurring and motion detection. The principle content is as follows: 1) When the prior knowledge about degradation function is unknown, the uniform motion blurred images are restored. At first, the blur parameters, including the motion blur extent and direction of PSF(point spread function), are estimated individually in domain of logarithmic frequency. The direction of PSF is calculated by extracting the central light line of the spectrum, and the extent is computed by minimizing the correction between the fourier spectrum of the blurred image and a detecting function. Moreover, in order to remove the strip in the deblurred image, windows technique is employed in the algorithm, which makes the deblurred image clear. 2) According to the principle of infrared image non-uniform exposure, a new restoration model for infrared blurred images is developed. The fitting of infrared image non-uniform exposure curve is performed by experiment data. The blurred images are restored by the fitting curve.

  10. Supernova remnant evolution in uniform and non-uniform media

    NASA Astrophysics Data System (ADS)

    Ferreira, S. E. S.; de Jager, O. C.

    2008-01-01

    Aims:In this work numerical simulations showing the time evolution of supernova remnants (SNRs) in uniform and non-uniform interstellar medium (ISM) are presented. Methods: We use a hydrodynamic model including a kinematic calculation of the interstellar magnetic field. Important parameters influencing SNR evolution include the ejecta mass and energy of the remnant, as well as the ISM density and adiabatic index. Results: By varying these parameters we constructed an analytical expression giving the return time of the SNR reverse shock to the origin, in terms of these parameters. We also found that the reverse shock spends half of its time moving outward and the other half returning to the origin. Also computed is SNR evolution in non-uniform media where the blast wave moves from one medium into either a less or more dense medium. As the SNR moves into a medium of higher density a reflection wave is created at the interface between the two media which is driven back toward the center. This drives mass via a nonspherical flow away from the discontinuity. As this wave moves inward it also drags some of the ISM field lines (if the field is parallel with the interface) with it and heats the inside of the SNR resulting in larger temperatures in this region. When a SNR explodes in a medium with a high density and the blast wave propagates into a medium with a lower density, a cavity is being blown away changing the geometry of the high density region. Also, once the forward shock moves into the medium of less density a second reverse shock will start to evolve in this region.

  11. 10 CFR 835.205 - Determination of compliance for non-uniform exposure of the skin.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 4 2013-01-01 2013-01-01 false Determination of compliance for non-uniform exposure of the skin. 835.205 Section 835.205 Energy DEPARTMENT OF ENERGY OCCUPATIONAL RADIATION PROTECTION Standards for Internal and External Exposure § 835.205 Determination of compliance for non-uniform exposure of the skin. (a) Non-uniform exposures of...

  12. Gridding and fast Fourier transformation on non-uniformly sparse sampled multidimensional NMR data.

    PubMed

    Jiang, Bin; Jiang, Xianwang; Xiao, Nan; Zhang, Xu; Jiang, Ling; Mao, Xi-an; Liu, Maili

    2010-05-01

    For multidimensional NMR method, indirect dimensional non-uniform sparse sampling can dramatically shorten acquisition time of the experiments. However, the non-uniformly sampled NMR data cannot be processed directly using fast Fourier transform (FFT). We show that the non-uniformly sampled NMR data can be reconstructed to Cartesian grid with the gridding method that has been wide applied in MRI, and sequentially be processed using FFT. The proposed gridding-FFT (GFFT) method increases the processing speed sharply compared with the previously proposed non-uniform Fourier Transform, and may speed up application of the non-uniform sparse sampling approaches. PMID:20236843

  13. Gridding and fast Fourier transformation on non-uniformly sparse sampled multidimensional NMR data

    NASA Astrophysics Data System (ADS)

    Jiang, Bin; Jiang, Xianwang; Xiao, Nan; Zhang, Xu; Jiang, Ling; Mao, Xi-an; Liu, Maili

    2010-05-01

    For multidimensional NMR method, indirect dimensional non-uniform sparse sampling can dramatically shorten acquisition time of the experiments. However, the non-uniformly sampled NMR data cannot be processed directly using fast Fourier transform (FFT). We show that the non-uniformly sampled NMR data can be reconstructed to Cartesian grid with the gridding method that has been wide applied in MRI, and sequentially be processed using FFT. The proposed gridding-FFT (GFFT) method increases the processing speed sharply compared with the previously proposed non-uniform Fourier Transform, and may speed up application of the non-uniform sparse sampling approaches.

  14. Nanomagnetic logic with non-uniform states of clocking

    NASA Astrophysics Data System (ADS)

    Puliafito, Vito; Giordano, Anna; Azzerboni, Bruno; Finocchio, Giovanni

    2016-04-01

    Nanomagnetic logic transmits information along a path of nanomagnets. The basic mechanism to drive such a transmission, known as clocking, can be achieved by exploiting the spin-Hall effect (SHE), as recently observed in experiments on Ta/CoFeB/MgO multilayers (Bhowmik et al 2014 Nat. Nano 9 59). This paper shows the fundamental mechanism of the spin-Hall driven clocking by using a full micromagnetic framework and considering two different devices, Ta/CoFeB/MgO and Pt/CoFeB/MgO. The former is used for a direct comparison of the numerical results with the experiments while the latter permits the effect of the Dzyaloshinskii-Moriya interaction (DMI) in the clocking mechanism to be predicted. Results show that the clocking state is non-uniform and it is characterized by the presence of domains separated by Bloch (Néel) domain walls depending on the absence (presence) of the DMI. Our findings point out that for the design of nanomagnetic logic a full micromagnetic approach is necessary.

  15. Non-uniform dose distributions in cranial radiation therapy

    NASA Astrophysics Data System (ADS)

    Bender, Edward T.

    Radiation treatments are often delivered to patients with brain metastases. For those patients who receive radiation to the entire brain, there is a risk of long-term neuro-cognitive side effects, which may be due to damage to the hippocampus. In clinical MRI and CT scans it can be difficult to identify the hippocampus, but once identified it can be partially spared from radiation dose. Using deformable image registration we demonstrate a semi-automatic technique for obtaining an estimated location of this structure in a clinical MRI or CT scan. Deformable image registration is a useful tool in other areas such as adaptive radiotherapy, where the radiation oncology team monitors patients during the course of treatment and adjusts the radiation treatments if necessary when the patient anatomy changes. Deformable image registration is used in this setting, but there is a considerable level of uncertainty. This work represents one of many possible approaches at investigating the nature of these uncertainties utilizing consistency metrics. We will show that metrics such as the inverse consistency error correlate with actual registration uncertainties. Specifically relating to brain metastases, this work investigates where in the brain metastases are likely to form, and how the primary cancer site is related. We will show that the cerebellum is at high risk for metastases and that non-uniform dose distributions may be advantageous when delivering prophylactic cranial irradiation for patients with small cell lung cancer in complete remission.

  16. Non-uniform system response detection for hyperspectral imaging systems

    NASA Astrophysics Data System (ADS)

    Castorena, Juan; Morrison, Jason; Paliwal, Jitendra; Erkinbaev, Chyngyz

    2015-11-01

    Near infrared (NIR) hyperspectral imaging (HSI) has established itself as a powerful non-destructive tool for the chemical analysis of heterogeneous samples. However, one of the main disadvantages of NIR HSI is that the technique suffers from instrumentation-related problems, which in turn affect the acquired images. In general, focal plane array (FPA) based hyperspectral systems are affected by spatial and spectral non-uniform response, the presence of defective sensors (e.g. dead or saturated sensors), and temporal and spatial (e.g. dark current) noise. Another issue is each new camera system needs to be calibrated to assess its specific responses to light. To correct for these issues, we used known standards to measure the response of the sensors and capture the location of the field of view and defective sensors using linear and quadratic models. The parameters of these models were then used as input features for classification of sensor responses using a k-means algorithm. The results conclude that linear models are insufficiently precise for calibration but estimate sufficiently accurately the system's response and functionality. Specifically, it was shown that the classification method discriminates non-responsive regions effectively.

  17. Efficient single image non-uniformity correction algorithm

    NASA Astrophysics Data System (ADS)

    Tendero, Y.; Gilles, J.; Landeau, S.; Morel, J. M.

    2010-10-01

    This paper introduces a new way to correct the non-uniformity (NU) in uncooled infrared-type images. The main defect of these uncooled images is the lack of a column (resp. line) time-dependent cross-calibration, resulting in a strong column (resp. line) and time dependent noise. This problem can be considered as a 1D flicker of the columns inside each frame. Thus, classic movie deflickering algorithms can be adapted, to equalize the columns (resp. the lines). The proposed method therefore applies to the series formed by the columns of an infrared image a movie deflickering algorithm. The obtained single image method works on static images, and therefore requires no registration, no camera motion compensation, and no closed aperture sensor equalization. Thus, the method has only one camera dependent parameter, and is landscape independent. This simple method will be compared to a state of the art total variation single image correction on raw real and simulated images. The method is real time, requiring only two operations per pixel. It involves no test-pattern calibration and produces no "ghost artifacts".

  18. Investigation of non-uniform materials under pressure

    NASA Astrophysics Data System (ADS)

    Shchennikov, Vladimir; Korobeynikov, Igor; Morozova, Natalia; Shchennikov, Vsevolod, Jr.; Voronin, Vladimir; Berger, Ivan; Laboratory of electronic properties of matter at high pressures Team; Laboratory of neutron investigation of matter Team; Laboratory of micromechanics Team

    2013-06-01

    The approach is considered of the investigation of non-uniform (NU) materials at high pressure (P). Under P a material may become NU due to phase transition (PT). At topological insulators the properties may include the contributions both of the bulk states as well as of the surface ones as at NU material etc.. The approach is based on the model of multi-phase system with ordered phase inclusions of variably configuration (A) and concentration (C), and the experimental data are presented for: i) the substances near PT, ii) some ceramics, iii) the certain natural minerals. Si, ZnX, PbX, SmX (X - Te, Se, S), GaP, iron ores, and (WC)xCo1-x hard alloys etc. have been investigated under P up to 30 GPa. It was shown that the model allows to describe resistance (R) and thermoelectric power (S), etc. in the vicinity of PT. For hard alloys WC-Co the elastic modulus has been fitted using the model, and A has been estimated to be distinguished from the simple isotropic case. In the iron ores the A and the C of various components (Fe, FeyOx, MgO,Mg2SiO4, etc.) has been estimated due to the using of the new approach based on the different depth of penetration of X-ray and neutron radiation, and also on different dependences of S, R on C, A.

  19. Terrestrial carbon cycle affected by non-uniform climate warming

    NASA Astrophysics Data System (ADS)

    Xia, Jianyang; Chen, Jiquan; Piao, Shilong; Ciais, Philippe; Luo, Yiqi; Wan, Shiqiang

    2014-03-01

    Feedbacks between the terrestrial carbon cycle and climate change could affect many ecosystem functions and services, such as food production, carbon sequestration and climate regulation. The rate of climate warming varies on diurnal and seasonal timescales. A synthesis of global air temperature data reveals a greater rate of warming in winter than in summer in northern mid and high latitudes, and the inverse pattern in some tropical regions. The data also reveal a decline in the diurnal temperature range over 51% of the global land area and an increase over only 13%, because night-time temperatures in most locations have risen faster than daytime temperatures. Analyses of satellite data, model simulations and in situ observations suggest that the impact of seasonal warming varies between regions. For example, spring warming has largely stimulated ecosystem productivity at latitudes between 30° and 90° N, but suppressed productivity in other regions. Contrasting impacts of day- and night-time warming on plant carbon gain and loss are apparent in many regions. We argue that ascertaining the effects of non-uniform climate warming on terrestrial ecosystems is a key challenge in carbon cycle research.

  20. Dynamic mode decomposition for non-uniformly sampled data

    NASA Astrophysics Data System (ADS)

    Leroux, Romain; Cordier, Laurent

    2016-05-01

    We propose an original approach to estimate dynamic mode decomposition (DMD) modes from non-uniformly sampled data. The proposed strategy processes a time-resolved sequence of flow snapshots in three steps. First, a reduced-order modeling of the non-missing data is made by proper orthogonal decomposition to obtain a low-order description of the state space. Second, the missing data are determined with maximum likelihood by coupling a linear dynamical state-space model with the Expectation-Maximization algorithm. Third, the DMD modes are finally estimated on the reconstructed data with a multiple linear regression method called orthonormalized partial least squares regression. This methodology is assessed for the flow past a NACA0012 airfoil at 20° of angle of attack and a Reynolds number of 103. The flow measurements are obtained with time-resolved particle image velocimetry and artificially subsampled at different ratios of missing data. The results show that the proposed method can reproduce the dominant DMD modes and the main structures of the flow fields for 50 and 75 % of missing data.

  1. SPECT scatter modelling in non-uniform attenuating objects

    NASA Astrophysics Data System (ADS)

    Beekman, Freek J.; den Harder, Johan M.; Viergever, Max A.; van Rijk, Peter P.

    1997-06-01

    SPECT quantitation and image contrast are degraded by photon scatter. Water equivalent depths (WEDs) have been used by several investigators to model scatter responses in non-uniform attenuators. The drawback of this approach is the occurrence of undesired fluctuations in the shape of the scatter responses, as is shown by measurements. An improvement of the WED method is presented, based on the assumption that only a part of the scattering object (the region in the `scatter cone') contributes significantly to the detected scatter events. The remaining part of the object is treated as a uniform medium. The extension of the WED method with extra-conical invariance is evaluated by projection measurements of a phantom with a source. Shapes of scatter responses predicted by the method are found to agree better with the measurements than those predicted by conventional WEDs.

  2. A non-uniform distribution of the nearest brown dwarfs

    NASA Astrophysics Data System (ADS)

    Bihain, G.; Scholz, R.-D.

    2016-05-01

    Context. The census of solar neighbours is still complemented by new discoveries, mainly of very low-mass, faint dwarfs, close to or within the substellar domain. These discoveries contribute to a better understanding of the field population; its origin in terms of Galactic dynamics and (sub)stellar formation and evolution. Also, the nearest stars and brown dwarfs at any given age allow the most precise direct characterization, including the search for planetary companions. Aims: We aim to further assess the substellar census on the Galactic plane. Methods: We projected the 136 stars and 26 brown dwarfs known at <6.5 pc on the Galactic plane and evaluated their distributions. Results: Stars present a uniform- and brown dwarfs a non-uniform distribution, with 21 objects behind the Sun and only five ahead relative to the direction of rotation of the Galaxy. This substellar configuration has a probability of 0.098+10.878-0.098% relative to uniformity. The helio- and geocentric nature of the distribution suggests it might result in part from an observational bias, which if compensated for by future discoveries, might increase the brown-dwarf-to-star ratio, shifting it closer to values found in some star forming regions.

  3. Dynamics of Non-Uniformity Loads of Afc Drives

    NASA Astrophysics Data System (ADS)

    Dolipski, Marian; Remiorz, Eryk; Sobota, Piotr

    2014-03-01

    The length of armoured face conveyors currently used in hard coal mines most often ranges between 200 m and 300 m. The machines are equipped with a main and auxiliary drive. Asynchronous motors mounted in conveyor drives feature the capacity of several hundreds of kilowatts. The non-uniform distribution of loads onto individual drives is observed in practice. The numerical value of loads distribution onto the individual armoured face conveyor drives is represented by a drive load distribution factor. It is defined as a ratio between the load of an electric motor installed in a given drive and the total conveyor load. The article presents a physical armoured face conveyor model intended for examining dynamic phenomena influencing the load non-uniformity of drives. Motion in this physical model is described with the system of (4 · j + 5) non-linear ordinary differential quotations of the second order. A mathematical model is obtained by adding functions describing the interwork of sprocket drums with chains and functions approximating the mechanical characteristics of asynchronous motors powered by means of frequency inverters. A large number of computer simulations was performed using this model enabling to study the impact on the load non-uniformity of drives of such parameters as motor slip, motor supply voltage drop, variations in supply voltage frequency, differences in the gear ratio of transmissions and differentiation in the pitch of scraper chain links along the chain contour. Długość przenośników zgrzebłowych ścianowych stosowanych obecnie w kopalniach węgla kamiennego najczęściej mieści się w przedziale od 200 m do 300 m. Maszyny te wyposażone są zawsze w napęd główny i pomocniczy, przy czym pierwszy z nich wyniesiony jest do chodnika podścianowego. Silniki napędowe o mocy kilkuset kilowatów napędzają bęben łańcuchowy przez sprzęgło i przekładnię zębatą. Z kolei bębny łańcuchowe poruszają łańcuch zgrzebłowy, kt

  4. Illumination non-uniformity of spirally wobbling beam in heavy ion fusion

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Noguchi, K.; Kurosaki, T.; Barada, D.; Kawata, S.; Ma, Y. Y.; Ogoyski, A. I.

    2016-03-01

    In inertial confinement fusion, the driver beam illumination non-uniformity leads a degradation of fusion energy output. The illumination non-uniformity allowed is less than a few percent in inertial fusion target implosion. Heavy ion beam (HIB) accelerator provides a capability to oscillate a beam axis with a high frequency. The wobbling beams may provide a new method to reduce or smooth the beam illumination non-uniformity. In this paper the HIBs wobbling illumination scheme was optimized.

  5. Coherent electron backscattering interference in non-uniform disordered systems

    NASA Astrophysics Data System (ADS)

    Chang, L.; Wu, G. Y.

    2011-08-01

    We study the coherent electron backscattering interference in the presence of electron dephasing in 2D/3D non-uniform (NU) disordered systems, within our virtual electron trap scattering (VETS) model, where the dephasing rate 1/ τφ is taken to be due to the inelastic electron-electron or electron-phonon scattering. A possible saturation mechanism of apparent electronic dephasing is examined. The system considered is composed of two kinds of subsystems, namely, L-islands and H-region with contrasting diffusion constants, of which the L-islands (of low diffusion constant) act as virtual electron traps randomly dispersed in the percolating H-background (of high diffusion constant). The physics of VETS model is characterized by the two important dwell times, τf and τb, with τf/ τb being the mean duration for which an electron wanders in the H-region/L-island before it leaves the region, respectively. In order to make connection with experiments, we introduce the notion of an effective system of uniform ( U) disorder with a dephasing time τφ(effective), which simulates in the aspect of backscattering the NU system being studied. The effective dephasing time τφ(effective) thus introduced is a function of τφ, and the function, τφ(effective)( τφ), is derived and examined. If τb≫ τf, an interesting phenomenon occurs in the range of temperature ( T) where the true dephasing time τφ( T) lies between τf and τb, i.e., τf< τφ( T)< τb. In this case, we obtain τφ(effective)( τφ)≈ τf, which is insensitive to the variation in τφ (or T) and shows the signature of τφ(effective) saturation. However, at the further lowered temperature where τφ( T)≥ τb, τφ(effective) rises up sharply without being saturated.

  6. Finite difference methods with non-uniform meshes for nonlinear fractional differential equations

    NASA Astrophysics Data System (ADS)

    Li, Changpin; Yi, Qian; Chen, An

    2016-07-01

    In this article, finite difference methods with non-uniform meshes for solving nonlinear fractional differential equations are presented, where the non-equidistant stepsize is non-decreasing. The rectangle formula and trapezoid formula are proposed based on the non-uniform meshes. Combining the above two methods, we then establish the predictor-corrector scheme. The error and stability analysis are carefully investigated. At last, numerical examples are carried out to verify the theoretical analysis. Besides, the comparisons between non-uniform and uniform meshes are given, where the non-uniform meshes show the better performance when dealing with the less smooth problems.

  7. Temporal high-pass non-uniformity correction algorithm based on grayscale mapping and hardware implementation

    NASA Astrophysics Data System (ADS)

    Jin, Minglei; Jin, Weiqi; Li, Yiyang; Li, Shuo

    2015-08-01

    In this paper, we propose a novel scene-based non-uniformity correction algorithm for infrared image processing-temporal high-pass non-uniformity correction algorithm based on grayscale mapping (THP and GM). The main sources of non-uniformity are: (1) detector fabrication inaccuracies; (2) non-linearity and variations in the read-out electronics and (3) optical path effects. The non-uniformity will be reduced by non-uniformity correction (NUC) algorithms. The NUC algorithms are often divided into calibration-based non-uniformity correction (CBNUC) algorithms and scene-based non-uniformity correction (SBNUC) algorithms. As non-uniformity drifts temporally, CBNUC algorithms must be repeated by inserting a uniform radiation source which SBNUC algorithms do not need into the view, so the SBNUC algorithm becomes an essential part of infrared imaging system. The SBNUC algorithms' poor robustness often leads two defects: artifacts and over-correction, meanwhile due to complicated calculation process and large storage consumption, hardware implementation of the SBNUC algorithms is difficult, especially in Field Programmable Gate Array (FPGA) platform. The THP and GM algorithm proposed in this paper can eliminate the non-uniformity without causing defects. The hardware implementation of the algorithm only based on FPGA has two advantages: (1) low resources consumption, and (2) small hardware delay: less than 20 lines, it can be transplanted to a variety of infrared detectors equipped with FPGA image processing module, it can reduce the stripe non-uniformity and the ripple non-uniformity.

  8. 10 CFR 835.205 - Determination of compliance for non-uniform exposure of the skin.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Determination of compliance for non-uniform exposure of the skin. 835.205 Section 835.205 Energy DEPARTMENT OF ENERGY OCCUPATIONAL RADIATION PROTECTION Standards for Internal and External Exposure § 835.205 Determination of compliance for non-uniform...

  9. 10 CFR 835.205 - Determination of compliance for non-uniform exposure of the skin.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 4 2014-01-01 2014-01-01 false Determination of compliance for non-uniform exposure of the skin. 835.205 Section 835.205 Energy DEPARTMENT OF ENERGY OCCUPATIONAL RADIATION PROTECTION Standards for Internal and External Exposure § 835.205 Determination of compliance for non-uniform...

  10. 10 CFR 835.205 - Determination of compliance for non-uniform exposure of the skin.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 4 2011-01-01 2011-01-01 false Determination of compliance for non-uniform exposure of the skin. 835.205 Section 835.205 Energy DEPARTMENT OF ENERGY OCCUPATIONAL RADIATION PROTECTION Standards for Internal and External Exposure § 835.205 Determination of compliance for non-uniform...

  11. 10 CFR 835.205 - Determination of compliance for non-uniform exposure of the skin.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Determination of compliance for non-uniform exposure of the skin. 835.205 Section 835.205 Energy DEPARTMENT OF ENERGY OCCUPATIONAL RADIATION PROTECTION Standards for Internal and External Exposure § 835.205 Determination of compliance for non-uniform...

  12. Validation of a heat conduction model for finite domain, non-uniformly heated, laminate bodies

    NASA Astrophysics Data System (ADS)

    Desgrosseilliers, Louis; Kabbara, Moe; Groulx, Dominic; White, Mary Anne

    2016-07-01

    Infrared thermographic validation is shown for a closed-form analytical heat conduction model for non-uniformly heated, laminate bodies with an insulated domain boundary. Experiments were conducted by applying power to rectangular electric heaters and cooled by natural convection in air, but also apply to constant-temperature heat sources and forced convection. The model accurately represents two-dimensional laminate heat conduction behaviour giving rise to heat spreading using one-dimensional equations for the temperature distributions and heat transfer rates under steady-state and pseudo-steady-state conditions. Validation of the model with an insulated boundary (complementing previous studies with an infinite boundary) provides useful predictions of heat spreading performance and simplified temperature uniformity calculations (useful in log-mean temperature difference style heat exchanger calculations) for real laminate systems such as found in electronics heat sinks, multi-ply stovetop cookware and interface materials for supercooled salt hydrates. Computational determinations of implicit insulated boundary condition locations in measured data, required to assess model equation validation, were also demonstrated. Excellent goodness of fit was observed (both root-mean-square error and R 2 values), in all cases except when the uncertainty of low temperatures measured via infrared thermography hindered the statistical significance of the model fit. The experimental validation in all other cases supports use of the model equations in design calculations and heat exchange simulations.

  13. Validation of a heat conduction model for finite domain, non-uniformly heated, laminate bodies

    NASA Astrophysics Data System (ADS)

    Desgrosseilliers, Louis; Kabbara, Moe; Groulx, Dominic; White, Mary Anne

    2015-08-01

    Infrared thermographic validation is shown for a closed-form analytical heat conduction model for non-uniformly heated, laminate bodies with an insulated domain boundary. Experiments were conducted by applying power to rectangular electric heaters and cooled by natural convection in air, but also apply to constant-temperature heat sources and forced convection. The model accurately represents two-dimensional laminate heat conduction behaviour giving rise to heat spreading using one-dimensional equations for the temperature distributions and heat transfer rates under steady-state and pseudo-steady-state conditions. Validation of the model with an insulated boundary (complementing previous studies with an infinite boundary) provides useful predictions of heat spreading performance and simplified temperature uniformity calculations (useful in log-mean temperature difference style heat exchanger calculations) for real laminate systems such as found in electronics heat sinks, multi-ply stovetop cookware and interface materials for supercooled salt hydrates. Computational determinations of implicit insulated boundary condition locations in measured data, required to assess model equation validation, were also demonstrated. Excellent goodness of fit was observed (both root-mean-square error and R 2 values), in all cases except when the uncertainty of low temperatures measured via infrared thermography hindered the statistical significance of the model fit. The experimental validation in all other cases supports use of the model equations in design calculations and heat exchange simulations.

  14. The effect of a non-uniform turning kernel on ant trail morphology.

    PubMed

    Vincent, Andrew D; Myerscough, Mary R

    2004-10-01

    An ordinary differential equation model is constructed for the formation of pheromone trails by ants on a pre-determined network. At each junction of the trails the probability that an ant will turn through any particular angle is given by a turning kernel. We prove analytically using analogies with thermodynamics that turning behaviour determines trail morphology when the turning kernel is steep. We conjecture that this is also true in general for non-uniform turning kernels and present numerical simulations as evidence. Using this conjecture we show the existence of three types of collective foraging: individuals exploring without the use of a trail network, and two distinct types of trail networks; one that consists of low pheromone concentration trails that bend, branch and dissipate and one that consists of high pheromone concentration, straight, unbranched trails. We show that the form of the pheromone response function is crucial in determining the existence and stability of the steady states corresponding to these three foraging strategies, and examine the bifurcations between different trail morphologies as a function of turning kernel steepness for a particular response function. PMID:15657796

  15. Adaptive non-uniformity correction method based on temperature for infrared detector array

    NASA Astrophysics Data System (ADS)

    Zhang, Zhijie; Yue, Song; Hong, Pu; Jia, Guowei; Lei, Bo

    2013-09-01

    The existence of non-uniformities in the responsitivity of the element array is a severe problem typical to common infrared detector. These non-uniformities result in a "curtain'' like fixed pattern noises (FPN) that appear in the image. Some random noise can be restrained by the method kind of equalization method. But the fixed pattern noise can only be removed by .non uniformity correction method. The produce of non uniformities of detector array is the combined action of infrared detector array, readout circuit, semiconductor device performance, the amplifier circuit and optical system. Conventional linear correction techniques require costly recalibration due to the drift of the detector or changes in temperature. Therefore, an adaptive non-uniformity method is needed to solve this problem. A lot factors including detectors and environment conditions variety are considered to analyze and conduct the cause of detector drift. Several experiments are designed to verify the guess. Based on the experiments, an adaptive non-uniformity correction method is put forward in this paper. The strength of this method lies in its simplicity and low computational complexity. Extensive experimental results demonstrate the disadvantage of traditional non-uniformity correct method is conquered by the proposed scheme.

  16. Pixel response non-uniformity correction for multi-TDICCD camera based on FPGA

    NASA Astrophysics Data System (ADS)

    Zhai, Guofang

    2013-10-01

    A non-uniformity correction algorithm is proposed and implemented on a Field-Programmable Gate Array (FPGA) hardware platform to solve a pixel response non-uniformity(PRNU) problem of multi Time Delay and Integration Charge Couple Device(TDICCD) camera. The non-uniformity are introduced and the synthetical correction algorithm is presented, in which the two-point correction method is used in a single channel, gain averaging correction method among multi-channel and the sceneadaptive correction method among multi-TDICCD. Then, the correction algorithm is designed. Finally, analyzing the FPGA ability for fix-point processing, the correction algorithm is optimized, and implemented on FPGA. Testing results indicate that the non-uniformity can be decreased from 8.27% to 0.51% for three TDICCDs camera's images with the proposed correction algorithm, proving that this correction algorithm is with high real-time performance, great engineering realization and satisfaction for the system requirements.

  17. Surface morphology driven non-uniform magnetism in epitaxial BiMnO3

    NASA Astrophysics Data System (ADS)

    Jeen, Hyoungjeen; Hae Kwak, In; Biswas, Amlan

    2016-08-01

    Thin films of BiMnO3 were grown on (001) SrTiO3 substrates by fine tuning the growth conditions. The films are epitaxial and impurity-free, but show island growth mode. From detailed magnetization measurements and surface analysis, we found evidence of morphology driven non-uniform magnetism. The non-uniform magnetism resulted in reduced saturation magnetization, reduced Curie temperature (T C), and nonlinear Arrott plots. In spite of non-uniform magnetism, the temperature dependence of magnetization showed conventional mean field behavior near T C. Our data suggest that non-uniform strain leads to coexistence of separate ferromagnetic and ferroelectric regions in BiMnO3 films which is not observed in bulk samples.

  18. Overall parameters for the characterization of non-uniformly totally polarized beams

    NASA Astrophysics Data System (ADS)

    Martínez-Herrero, R.; Mejías, P. M.; Piquero, G.

    2006-09-01

    Several overall parameters are introduced to characterize the linear or circular polarization content of a non-uniformly totally polarized beam over the region of its wavefront where the irradiance is significant. These figures of merit are determined from the values of the Stokes parameters. The physical meaning of the proposed parameters is tested by computing some numerical examples, and their measurability is checked by considering non-uniformly totally polarized fields generated after propagation through uniaxial anisotropic materials.

  19. Dielectrophoresis device and method having non-uniform arrays for manipulating particles

    DOEpatents

    Cummings, Eric B.; Fintschenko, Yolanda; Simmons, Blake

    2008-09-02

    Microfluidic devices according to embodiments of the present invention include an inlet port, an outlet port, and a channel or chamber having a non-uniform array of insulating features on one or more surfaces. Electrodes are provided for generation of a spatially non-uniform electric field across the array. A voltage source, which may be an A.C. and/or a D.C. voltage source may be coupled to the electrodes for the generation of the electric field.

  20. The Impact of Non-Uniform Cloud Cover on Transit Transmission Spectra

    NASA Astrophysics Data System (ADS)

    Line, Michael; Parmentier, Vivien

    2015-12-01

    Clouds play a substantial role in sculpting transit transmission spectra as they tend to mute or entirely mask spectral features. Many investigations have treated clouds as globally uniform with a single “1D” structure. However, we have learned from albedo phase curves (e.g., Kepler 7) that cloud coverage can be spatially inhomogeneous across the planetary disk. Non-uniform cloud coverage is also supported by brown dwarf variability observations which suggest the presence of “patchy clouds”. We also see non-uniform cloud coverage within our own solar system planets (e.g., belts and zones on Jupiter, ITCZ on earth etc.). Given the mounting evidence for spatially variable cloud coverage, it is prudent that we at least explore the role that non-uniform cloud coverage can have on transit transmission spectra. In this investigation we demonstrate how non-uniform cloud coverage on the terminator can influence transit transmission spectra and the potential biases incurred if non-uniform cloud coverage is not taken into account in spectral retrievals. For instance, a high altitude opaque cloud covering the entire morning terminator, along with a perfectly clear evening terminator can mimic a high mean molecular weight transmission spectrum in a hot Jupiter. Finally, we present the impact that non-uniform cloud coverage may have on transit light curves.

  1. An infrared image non-uniformity correction algorithm based on pixels' equivalent integral capacitance

    NASA Astrophysics Data System (ADS)

    Zhang, Shuanglei; Wang, Tao; Xu, Chun; Chen, Fansheng

    2015-04-01

    In the infrared focal plane array (IRFPA) imaging system, the non-uniformity (NU) of IRFPA directly affects the quality of infrared images. Especially applying in the infrared weak small targets detection and tracking system, the impact of the spatial noise caused by the non-uniformity of IRFPA detector, often more serious than the temporal noise of imaging system. In order to effectively correct the non-uniformity of IRFPA detector, we firstly analyze main factors that cause the non-uniformity of IRFPA detector in imaging. Secondly, according to photoelectric conversion mechanism of IRFPA detector, and the analysis of the process of the target energy accumulation and transfer, we propose a calculation method of pixels' integral capacitance. Then according to the calculation results, we correct the original IR image preliminary. Finally, we validate this non-uniformity correction algorithm by processing IR images collected from actual IRFPA imaging system. Results show that the algorithm can effectively restrain the non-uniformity caused by the differences of the pixels' capacitance.

  2. The role of sarcomere length non-uniformities in residual force enhancement of skeletal muscle myofibrils

    PubMed Central

    Johnston, Kaleena; Jinha, Azim; Herzog, Walter

    2016-01-01

    The sarcomere length non-uniformity theory (SLNT) is a widely accepted explanation for residual force enhancement (RFE). RFE is the increase in steady-state isometric force following active muscle stretching. The SLNT predicts that active stretching of a muscle causes sarcomere lengths (SL) to become non-uniform, with some sarcomeres stretched beyond actin–myosin filament overlap (popping), causing RFE. Despite being widely known, this theory has never been directly tested. We performed experiments on isolated rabbit muscle myofibrils (n = 12) comparing SL non-uniformities for purely isometric reference contractions (I-state) and contractions following active stretch producing RFE (FE-state). Myofibrils were activated isometrically along the descending limb of the force–length relationship (mean ± 1 standard deviation (SD) = 2.8 ± 0.3 µm sarcomere−1). Once the I-state was reached, myofibrils were shortened to an SL on the plateau of the force–length relationship (2.4 µm sarcomere−1), and then were actively stretched to the reference length (2.9 ± 0.3 µm sarcomere−1). We observed RFE in all myofibrils (39 ± 15%), and saw varying amounts of non-uniformity (1 SD = 0.9 ± 0.5 µm) that was not significantly correlated with the amount of RFE, but through pairwise comparisons was found to be significantly greater than the non-uniformity measured for the I-state (0.7 ± 0.4 µm). Three myofibrils exhibited no increase in non-uniformity. Active stretching was accompanied by sarcomere popping in four myofibrils, and seven had popped sarcomeres in the I-state. These results suggest that, while non-uniformities are present with RFE, they are also present in the I-state. Furthermore, non-uniformity is not associated with the magnitude of RFE, and myofibrils that had no increase in non-uniformity with stretch still showed normal RFE. Therefore, it appears that SL non-uniformity is a normal associate of muscle

  3. The role of sarcomere length non-uniformities in residual force enhancement of skeletal muscle myofibrils.

    PubMed

    Johnston, Kaleena; Jinha, Azim; Herzog, Walter

    2016-03-01

    The sarcomere length non-uniformity theory (SLNT) is a widely accepted explanation for residual force enhancement (RFE). RFE is the increase in steady-state isometric force following active muscle stretching. The SLNT predicts that active stretching of a muscle causes sarcomere lengths (SL) to become non-uniform, with some sarcomeres stretched beyond actin-myosin filament overlap (popping), causing RFE. Despite being widely known, this theory has never been directly tested. We performed experiments on isolated rabbit muscle myofibrils (n = 12) comparing SL non-uniformities for purely isometric reference contractions (I-state) and contractions following active stretch producing RFE (FE-state). Myofibrils were activated isometrically along the descending limb of the force-length relationship (mean ± 1 standard deviation (SD) = 2.8 ± 0.3 µm sarcomere(-1)). Once the I-state was reached, myofibrils were shortened to an SL on the plateau of the force-length relationship (2.4 µm sarcomere(-1)), and then were actively stretched to the reference length (2.9 ± 0.3 µm sarcomere(-1)). We observed RFE in all myofibrils (39 ± 15%), and saw varying amounts of non-uniformity (1 SD = 0.9 ± 0.5 µm) that was not significantly correlated with the amount of RFE, but through pairwise comparisons was found to be significantly greater than the non-uniformity measured for the I-state (0.7 ± 0.4 µm). Three myofibrils exhibited no increase in non-uniformity. Active stretching was accompanied by sarcomere popping in four myofibrils, and seven had popped sarcomeres in the I-state. These results suggest that, while non-uniformities are present with RFE, they are also present in the I-state. Furthermore, non-uniformity is not associated with the magnitude of RFE, and myofibrils that had no increase in non-uniformity with stretch still showed normal RFE. Therefore, it appears that SL non-uniformity is a normal associate of muscle

  4. Modelling photon transport in non-uniform media for SPECT with a vectorized Monte Carlo code.

    PubMed

    Smith, M F

    1993-10-01

    A vectorized Monte Carlo code has been developed for modelling photon transport in non-uniform media for single-photon-emission computed tomography (SPECT). The code is designed to compute photon detection kernels, which are used to build system matrices for simulating SPECT projection data acquisition and for use in matrix-based image reconstruction. Non-uniform attenuating and scattering regions are constructed from simple three-dimensional geometric shapes, in which the density and mass attenuation coefficients are individually specified. On a Stellar GS1000 computer, Monte Carlo simulations are performed between 1.6 and 2.0 times faster when the vector processor is utilized than when computations are performed in scalar mode. Projection data acquired with a clinical SPECT gamma camera for a line source in a non-uniform thorax phantom are well modelled by Monte Carlo simulations. The vectorized Monte Carlo code was used to stimulate a 99Tcm SPECT myocardial perfusion study, and compensations for non-uniform attenuation and the detection of scattered photons improve activity estimation. The speed increase due to vectorization makes Monte Carlo simulation more attractive as a tool for modelling photon transport in non-uniform media for SPECT. PMID:8248288

  5. Numerical simulation of the impact of urban non-uniformity on precipitation

    NASA Astrophysics Data System (ADS)

    Song, Yuqiang; Liu, Hongnian; Wang, Xueyuan; Zhang, Ning; Sun, Jianning

    2016-06-01

    To evaluate the influence of urban non-uniformity on precipitation, the area of a city was divided into three categories (commercial, high-density residential, and low-density residential) according to the building density data from Landsat satellites. Numerical simulations of three corresponding scenarios (urban non-uniformity, urban uniformity, and non-urban) were performed in Nanjing using the WRF model. The results demonstrate that the existence of the city results in more precipitation, and that urban heterogeneity enhances this phenomenon. For the urban non-uniformity, uniformity, and non-urban experiments, the mean cumulative summer precipitation was 423.09 mm, 407.40 mm, and 389.67 mm, respectively. Urban non-uniformity has a significant effect on the amount of heavy rainfall in summer. The cumulative precipitation from heavy rain in the summer for the three numerical experiments was 278.2 mm, 250.6 mm, and 236.5 mm, respectively. In the nonuniformity experiments, the amount of precipitation between 1500 and 2200 (LST) increased significantly. Furthermore, the adoption of urban non-uniformity into the WRF model could improve the numerical simulation of summer rain and its daily variation.

  6. Gravitational Instability of Cylindrical Viscoelastic Medium Permeated with Non Uniform Magnetic Field and Rotation

    NASA Astrophysics Data System (ADS)

    Dhiman, Joginder Singh; Sharma, Rajni

    2016-03-01

    The self-gravitating instability of an infinitely extending axisymmetric cylinder of viscoelastic medium permeated with non uniform magnetic field and rotation is studied for both the strongly coupled plasma (SCP) and weakly coupled plasma (WCP). The non uniform magnetic field and rotation are considered to act along the axial direction of the cylinder. The normal mode method of perturbations is applied to obtain the dispersion relation. The condition for the onset of gravitational instability has been derived from the dispersion relation under both strongly and weakly coupling limits. It is found that the Jeans criterion for gravitational collapse gets modified due to the presence of shear and bulk viscosities for the SCP, however, the magnetic field and rotation whether uniform or non uniform has no effect on the Jeans criterion of an infinitely extending axisymmetric cylinder of a self-gravitating viscoelastic medium.

  7. Effects of Non-Uniform Fuel Distribution on Detonation Tube Performance

    NASA Technical Reports Server (NTRS)

    Perkins, H. Douglas; Sung, Chih-Jen

    2003-01-01

    A pulse detonation engine uses a series of high frequency intermittent detonation tubes to generate thrust. The process of filling the detonation tube with fuel and air for each cycle may yield non-uniform mixtures. Uniform mixing is commonly assumed when calculating detonation tube thrust performance. In this study, detonation cycles featuring idealized non-uniform H2/air mixtures were analyzed using a two-dimensional Navier-Stokes computational fluid dynamics code with detailed chemistry. Mixture non-uniformities examined included axial equivalence ratio gradients, transverse equivalence ratio gradients, and partially fueled tubes. Three different average test section equivalence ratios were studied; one stoichiometric, one fuel lean, and one fuel rich. All mixtures were detonable throughout the detonation tube. Various mixtures representing the same average test section equivalence ratio were shown to have specific impulses within 1% of each other, indicating that good fuel/air mixing is not a prerequisite for optimal detonation tube performance under the conditions investigated.

  8. Carbon monoxide sensor and method of use thereof

    DOEpatents

    McDaniel; Anthony H. , Medlin; J. Will , Bastasz; Robert J.

    2007-09-04

    Carbon monoxide sensors suitable for use in hydrogen feed streams and methods of use thereof are disclosed. The sensors are palladium metal/insulator/semiconductor (Pd-MIS) sensors which may possess a gate metal layer having uniform, Type 1, or non-uniform, Type 2, film morphology. Type 1 sensors display an increased sensor response in the presence of carbon monoxide while Type 2 sensors display a decreased response to carbon monoxide. The methods and sensors disclosed herein are particularly suitable for use in proton exchange membrane fuel cells (PEMFCs).

  9. Research of improved sparse grid non-uniformity correction technologies for infrared resistor array

    NASA Astrophysics Data System (ADS)

    Du, Hui-jie; Zhao, Hong-ming; Gao, Yang; Yu, Hong; Zhang, Yi

    2015-10-01

    Infrared resistor arrays perform a vital role in the hardware in the loop testing of infrared seekers. Infrared resistor arrays composed of large numbers of suspended resistor elements are commonly used to produce dynamic two-dimensional images of infrared radiation. Due to inconsistencies in the fabrication process of the resistor arrays, the temperature each resistor elements reaches for a given input voltage is variable and this leads to more significant radiance differences, these differences result in spatially-distributed radiance non-uniformity. Therefore, in order to obtain an available infrared image, non-uniformity correction (NUC) is necessary. In this paper, the non-uniformity characters of the infrared resistor arrays are analyzed base on measured data and then an improved sparse grid method for engineering are discussed and analyzed. First of all, the NUC camera has a strong influence on the effectiveness of the infrared resistor arrays NUC procedure. According to the actual fact and the laboratory condition, we presented an alternative method for collecting resistor arrays intended to reduce the influence causing by the NUC camera. Secondly, based on the measured non-uniformity data, we obtain the response characteristics of the infrared resistor arrays. In each gray level, we take two points or several points correction algorithm to calculate the gain data and the offset data, and then the linear look-up table is established. Finally, through MATLAB we develop the correction software, and we can obtain the driving output conveniently. The result shows that the image quality has a remarkable improvement after non-uniformity correction, the non-uniformity correction flow and algorithm preferably satisfies the requirement of the high confidence infrared imaging simulation.

  10. Compression gain of spin wave signals in a magnonic YIG waveguide with thermal non-uniformity

    NASA Astrophysics Data System (ADS)

    Kolokoltsev, O.; Gómez-Arista, Ivan; Qureshi, N.; Acevedo, A.; Ordóñez-Romero, César L.; Grishin, A.

    2015-03-01

    We report on the observation of the compression gain of the signals carried by surface spin waves (MSSWs) in yittrium iron garnet films as a result of non-uniform optical heating of the spin wave medium. Efficient gain takes place if a frequency downshift of the spin wave spectrum induced by the heating is compensated by the corresponding non-uniformity of the bias magnetic field. It is proposed that the effect can be understood in part as an interaction between spin waves and a thermally induced potential well in the sample.

  11. Some applications of the characteristics non-uniform Doppler to radar

    NASA Astrophysics Data System (ADS)

    Gray, John E.; Breaux, Nancy A.; Hansen, Jeremiah J.

    2016-05-01

    Since the inception of coherent waveforms, it has been realized that the effect of non-uniform motion of a non-point like object can induce structure in the return spectrum of the waveform that can be exploited. The non-uniform Doppler spectrum has useful information that can be found in the spreading of the Doppler spectrum for the motion models: acceleration, jerk, quadric, and exponential slowdown as examples well as a characteristic of periodic motion. We illustrate this with examples relevant to automotive radar, tracking meteors with ambient sources, characterizing moving sources and other relevant examples.

  12. Propagation characteristics of a non-uniformly Hermite-Gaussian correlated beam

    NASA Astrophysics Data System (ADS)

    Song, Zhenzhen; Liu, Zhengjun; Zhou, Keya; Sun, Qiongge; Liu, Shutian

    2016-01-01

    We introduce a new kind of partially coherent beam, non-uniformly Hermite-Gaussian correlated beam, by employing a non-uniformly Hermite function to modulate the spectral degree of coherence. The evolution of such scalar beam on propagation in free space and turbulent atmosphere are investigated. It is demonstrated that the spectral intensity distributions exhibit extraordinary propagation characteristics, such as self-focusing and laterally shifted intensity maxima. The position of the maximum intensity and the intensity profile can be controlled by the order of the Hermite function. The results can be useful in free-space optical communications and beam shaping.

  13. Additive non-uniform random sampling in superimposed fiber Bragg grating strain gauge

    NASA Astrophysics Data System (ADS)

    Ma, Y. C.; Liu, H. Y.; Yan, S. B.; Yang, Y. H.; Yang, M. W.; Li, J. M.; Tang, J.

    2013-05-01

    This paper demonstrates an additive non-uniform random sampling and interrogation method for dynamic and/or static strain gauge using a reflection spectrum from two superimposed fiber Bragg gratings (FBGs). The superimposed FBGs are designed to generate non-equidistant space of a sensing pulse train in the time domain during dynamic strain gauge. By combining centroid finding with smooth filtering methods, both the interrogation speed and accuracy are improved. A 1.9 kHz dynamic strain is measured by generating an additive non-uniform randomly distributed 2 kHz optical sensing pulse train from a mean 500 Hz triangular periodically changing scanning frequency.

  14. Improving performance of LMS non-uniformity correction by sigma filter

    NASA Astrophysics Data System (ADS)

    Liang, Chaobing; Sang, Hongshi

    2013-10-01

    Spatial smoothing filters are usually used in LMS-based non-uniformity correction methods to get an estimation of true scene. Edge-smearing of these filters is the main reason for `ghosting' artifacts. A method based on sigma filter is proposed, which can improve accuracy of non-uniformity and mitigate `ghosting' artifacts. Sigma filter is also used to detect abnormal pixels and adaptively adjust learning rate. Tests with simulated data and real infrared sequences have shown that the proposed method outperforms other representative LMS-based methods.

  15. Photocathode non-uniformity contribution to the energy resolution of scintillators.

    PubMed

    Mottaghian, M; Koohi-Fayegh, R; Ghal-Eh, N; Etaati, G R

    2010-06-01

    This paper introduces the basics of the light transport simulation in scintillators and the wavelength-dependencies in the process. The non-uniformity measurement of the photocathode surface is undertaken, showing that for the photocathode used in this study the quantum efficiency falls to about 4 % of its maximum value, especially in areas far from the centre. The wavelength- and position-dependent quantum efficiency is implemented in the Monte Carlo light transport code, showing that, the contribution of the photocathode non-uniformity to the energy resolution is estimated to be around 18 %, when all position- and wavelength-dependencies are included. PMID:20167795

  16. Interaction of high intensity laser with non-uniform clusters and enhanced X-ray emission

    SciTech Connect

    Liu, C. S.; Tripathi, V. K.; Kumar, Manoj

    2014-10-15

    Laser irradiated clusters with non-uniform density variation are shown to broaden surface plasmon resonance very significantly. As the clusters get heated and expand hydro-dynamically, the Bremsstrahlung X-ray emission yield passes through a maximum in time. The maximum yield decreases with increase in non-uniformity in the electron density inside the clusters. At higher laser intensity, the nonlinearity in laser cluster interaction may arise even prior to electron heating, via the relativistic mass variation and the nonlinear restoration force on electrons. For clusters with radius less than one tenth of the laser wavelength, the restoration force nonlinearity dominates.

  17. The Pierce diode with an external circuit: II, Non-uniform equilibria

    SciTech Connect

    Lawson, W.S.

    1987-07-22

    The non-uniform (non-linear) equilibria of the classical (short circuit) Pierce diode and the extended (series RLC external circuit) Pierce diode are described theoretically, and explored via computer simulation. It is found that most equilibria are correctly predicted by theory, but that the continuous set of equilibria of the classical Pierce diode at ..cap alpha.. = 2..pi.. are not observed. The stability characteristics of the non-uniform equilibria are also worked out, and are consistent with the simulations. 8 refs., 22 figs., 3 tabs.

  18. Analysis of axially non-uniform loss distribution in 3-phase induction motor considering skew effect

    SciTech Connect

    Kown, B.I.; Kim, B.T.; Jun, C.S.; Park, S.C. )

    1999-05-01

    This paper discusses the phenomena of the axially non-uniform distribution of magnetic flux densities and losses in a 3-phase squirrel cage induction motor of which the rotor bars are skewed. A 2-dimensional complex finite element method taking account of the effects of the skewed rotor bars is utilized for the analysis of characteristics such as copper and iron losses and the loss distributions are examined. The summing up values of non-uniform losses resulted from the finite element analysis are compared with measurement values.

  19. English Non-Uniformity: A Non-Adult Form of Ethnic English.

    ERIC Educational Resources Information Center

    Stout, Steven Owen

    The paper examines interpretive aspects of English non-uniformity among fifth and sixth grade Native Americans at Laguna Elementary School, Laguna, New Mexico. Speaker assessments of instances of uninflected "be" are ordered to form an implicational scale. The variability in the students' assessment pattern is compared to previous inter-ethnic…

  20. Travelling waves in boundary-controlled, non-uniform, cascaded lumped systems

    NASA Astrophysics Data System (ADS)

    O'Connor, William J.; Zhu, Ming

    2013-08-01

    A companion paper considers travelling and standing waves in cascaded, lumped, mass-spring systems, controlled by two boundary actuators, one at each end, when the system is uniform. It first proposes definitions of waves in finite lumped systems. It then shows how to control the actuators to establish desired waves from rest, and to maintain them despite disturbances. The present paper extends this work to the more general, non-uniform case, when mass and spring values can be arbitrary. A special "bi-uniform" case is first studied, consisting of two different uniform cascaded systems in series, with an obvious, uncontrolled, impedance mismatch where they meet. The paper shows how boundary actuator control systems can be designed to establish, and robustly maintain, apparently pure travelling waves of constant amplitude in either the first or the second uniform section, in each case with an appropriate, partial, standing wave pattern in the other section. Then a more general non-uniform case is studied. A definition of a "pure travelling wave" in non-uniform systems is proposed. Curiously, it does not imply constant amplitude motion. It does however yield maximum power transfer between boundary actuators. The definition, and its implementation in a control system, involves extending the notions of "pure" travelling waves, of standing waves, and of input and output impedances of sources and loads, when applied to non-uniform lumped systems. Practical, robust control strategies are presented for all cases.

  1. Phase Transitions in a Non-Uniformly Stressed Iron Borate Single Crystal

    NASA Astrophysics Data System (ADS)

    Dzhuraev, D. R.; Niyazov, L. N.; Sokolov, B. Yu.

    2016-05-01

    Based on the Landau thermodynamic theory, phase transformations observed in a FeBO3 single crystal subject to spatially non-uniform mechanical stresses are analyzed. It is demonstrated that the main results of theoretical consideration of structural and magnetic phase transitions in the examined crystal do not contradict with the available experimental data.

  2. The Implementation of non-uniformity correction in multi-TDICCD imaging system

    NASA Astrophysics Data System (ADS)

    Zhai, Guofang; Cheng, Yun; Han, Zhixue; Wang, Dong

    2015-10-01

    Abstract—a non-uniformity correction algorithm is proposed and implemented on a Field-Programmable Gate Array (FPGA) hardware platform to solve a problem of pixel response non-uniformity(PRNU) for multiple Time Delay and Integration Charge Couple Device(TDICCD) camera. The non-uniformity is introduced and a synthetical correction algorithm is presented, in which the two-point correction method is applied to a single channel, gain averaging correction method among multi-channel and scene-adaptive correction method among multiple-TDICCD. Then, the correction algorithm is generated. Finally, the FPGA ability for fix-point processing is analyzed; the correction algorithm is optimized, and implemented on FPGA. Testing results indicate that the non-uniformity can be decreased from 8.27% to 0.51% for three TDICCDs camera's images with this proposed correction algorithm, proving that this correction algorithm is with high real-time performance, great engineering realization and satisfaction for the system requirements.

  3. Algebraic grid adaptation method using non-uniform rational B-spline surface modeling

    NASA Technical Reports Server (NTRS)

    Yang, Jiann-Cherng; Soni, B. K.

    1992-01-01

    An algebraic adaptive grid system based on equidistribution law and utilized by the Non-Uniform Rational B-Spline (NURBS) surface for redistribution is presented. A weight function, utilizing a properly weighted boolean sum of various flow field characteristics is developed. Computational examples are presented to demonstrate the success of this technique.

  4. Output-only modal identification by compressed sensing: Non-uniform low-rate random sampling

    NASA Astrophysics Data System (ADS)

    Yang, Yongchao; Nagarajaiah, Satish

    2015-05-01

    Modal identification or testing of structures consists of two phases, namely, data acquisition and data analysis. Some structures, such as aircrafts, high-speed machines, and plate-like civil structures, have active modes in the high-frequency range when subjected to high-speed or broadband excitation in their operational conditions. In the data acquisition stage, the Shannon-Nyquist sampling theorem indicates that capturing the high-frequency modes (signals) requires uniform high-rate sampling, resulting in sensing too many samples, which potentially impose burdens on the data transfer (especially in wireless platform) and data analysis stage. This paper explores a new-emerging, alternative, signal sampling and analysis technique, compressed sensing, and investigates the feasibility of a new method for output-only modal identification of structures in a non-uniform low-rate random sensing framework based on a combination of compressed sensing (CS) and blind source separation (BSS). Specifically, in the data acquisition stage, CS sensors sample few non-uniform low-rate random measurements of the structural responses signals, which turn out to be sufficient to capture the underlying mode information. Then in the data analysis stage, the proposed method uses the BSS technique, complexity pursuit (CP) recently explored by the authors, to directly decouple the non-uniform low-rate random samples of the structural responses, simultaneously yielding the mode shape matrix as well as the non-uniform low-rate random samples of the modal responses. Finally, CS with ℓ1-minimization recovers the uniform high-rate modal response from the CP-decoupled non-uniform low-rate random samples of the modal response, thereby enabling estimation of the frequency and damping ratio. Because CS sensors are currently in laboratory prototypes and not yet commercially available, their functionality-randomly sensing few non-uniform samples-is simulated in this study, which is performed on the

  5. The Gas Motion Due To Non-Uniform Heating By 3He(n,p)3H Reactions In The Nuclear-Pumped3He -Lasers

    NASA Astrophysics Data System (ADS)

    Çetin, Füsun

    2007-04-01

    In the nuclear pumped-lasers, the passage of these energetic charged particles through gas results in a non-uniform volumetric energy deposition. This spatial non-uniformity induces a gas motion, which results in density and hence refractive index gradients that affects the laser's optical behaviour. The motion of 3He gas in a closed cavity is studied when it experiences transient and spatially non-uniform volumetric heating caused by the passage of 3He(n,p)3H reaction products. Gas motion is described by the radial velocity field of gas flow. Spatial and temporal variations of radial gas velocity are calculated for various tube parameters by using a dynamic energy deposition model. In the calculations, it is assumed that the laser tube is irradiated with neutrons from the pulse at a peak power of 1200 MW corresponding to a maximum thermal neutron flux of 8×1016 n / cm2sn in the central channel of ITU TRIGA Mark II Reactor. Results are examined.

  6. The Gas Motion Due To Non-Uniform Heating By 3He(n,p)3H Reactions In The Nuclear-Pumped3He -Lasers

    SciTech Connect

    Cetin, Fuesun

    2007-04-23

    In the nuclear pumped-lasers, the passage of these energetic charged particles through gas results in a non-uniform volumetric energy deposition. This spatial non-uniformity induces a gas motion, which results in density and hence refractive index gradients that affects the laser's optical behaviour. The motion of 3He gas in a closed cavity is studied when it experiences transient and spatially non-uniform volumetric heating caused by the passage of 3He(n,p)3H reaction products. Gas motion is described by the radial velocity field of gas flow. Spatial and temporal variations of radial gas velocity are calculated for various tube parameters by using a dynamic energy deposition model. In the calculations, it is assumed that the laser tube is irradiated with neutrons from the pulse at a peak power of 1200 MW corresponding to a maximum thermal neutron flux of 8x1016 n / cm2sn in the central channel of ITU TRIGA Mark II Reactor. Results are examined.

  7. Node Non-Uniform Deployment Based on Clustering Algorithm for Underwater Sensor Networks.

    PubMed

    Jiang, Peng; Liu, Jun; Wu, Feng

    2015-01-01

    A node non-uniform deployment based on clustering algorithm for underwater sensor networks (UWSNs) is proposed in this study. This algorithm is proposed because optimizing network connectivity rate and network lifetime is difficult for the existing node non-uniform deployment algorithms under the premise of improving the network coverage rate for UWSNs. A high network connectivity rate is achieved by determining the heterogeneous communication ranges of nodes during node clustering. Moreover, the concept of aggregate contribution degree is defined, and the nodes with lower aggregate contribution degrees are used to substitute the dying nodes to decrease the total movement distance of nodes and prolong the network lifetime. Simulation results show that the proposed algorithm can achieve a better network coverage rate and network connectivity rate, as well as decrease the total movement distance of nodes and prolong the network lifetime. PMID:26633408

  8. The development of non-uniform deposition of holes in gate oxides

    SciTech Connect

    Freitag, R.K.; Dozier, C.M.; Brown, D.B.; Burke, E.A.

    1988-12-01

    The subthreshold technique was used to study irradiated MOS transistors at 80 K. Stretchout of the subthreshold curve demonstrated production of lateral non-uniformities (LNUs) in the hole distribution. The LNUs were analyzed in terms of (a) a parallel transistor model, and (b) the statistics of the non-uniform distribution of dose deposition in the SiO/sub 2/. The results confirm the hypothesis that at 80 K the principal source of LNUs is the granularity in dose deposition. The relative standard deviation for the deposited dose is larger for thin oxides, for 10 kev x-rays (as opposed to Co-60), and at low doses. These physical phenomena are predicted to have a significant effect at room temperature also.

  9. Node Non-Uniform Deployment Based on Clustering Algorithm for Underwater Sensor Networks

    PubMed Central

    Jiang, Peng; Liu, Jun; Wu, Feng

    2015-01-01

    A node non-uniform deployment based on clustering algorithm for underwater sensor networks (UWSNs) is proposed in this study. This algorithm is proposed because optimizing network connectivity rate and network lifetime is difficult for the existing node non-uniform deployment algorithms under the premise of improving the network coverage rate for UWSNs. A high network connectivity rate is achieved by determining the heterogeneous communication ranges of nodes during node clustering. Moreover, the concept of aggregate contribution degree is defined, and the nodes with lower aggregate contribution degrees are used to substitute the dying nodes to decrease the total movement distance of nodes and prolong the network lifetime. Simulation results show that the proposed algorithm can achieve a better network coverage rate and network connectivity rate, as well as decrease the total movement distance of nodes and prolong the network lifetime. PMID:26633408

  10. Selective exfoliation of single-layer graphene from non-uniform graphene grown on Cu

    NASA Astrophysics Data System (ADS)

    Lim, Jae-Young; Lee, Jae-Hyun; Jang, Hyeon-Sik; Joo, Won-Jae; Hwang, SungWoo; Whang, Dongmok

    2015-11-01

    Graphene growth on a copper surface via metal-catalyzed chemical vapor deposition has several advantages in terms of providing high-quality graphene with the potential for scale-up, but the product is usually inhomogeneous due to the inability to control the graphene layer growth. The non-uniform regions strongly affect the reliability of the graphene in practical electronic applications. Herein, we report a novel graphene transfer method that allows for the selective exfoliation of single-layer graphene from non-uniform graphene grown on a Cu foil. Differences in the interlayer bonding energy are exploited to mechanically separate only the top single-layer graphene and transfer this to an arbitrary substrate. The dry-transferred single-layer graphene showed electrical characteristics that were more uniform than those of graphene transferred using conventional wet-etching transfer steps.

  11. Capacity achieving nonbinary LDPC coded non-uniform shaping modulation for adaptive optical communications.

    PubMed

    Lin, Changyu; Zou, Ding; Liu, Tao; Djordjevic, Ivan B

    2016-08-01

    A mutual information inspired nonbinary coded modulation design with non-uniform shaping is proposed. Instead of traditional power of two signal constellation sizes, we design 5-QAM, 7-QAM and 9-QAM constellations, which can be used in adaptive optical networks. The non-uniform shaping and LDPC code rate are jointly considered in the design, which results in a better performance scheme for the same SNR values. The matched nonbinary (NB) LDPC code is used for this scheme, which further improves the coding gain and the overall performance. We analyze both coding performance and system SNR performance. We show that the proposed NB LDPC-coded 9-QAM has more than 2dB gain in symbol SNR compared to traditional LDPC-coded star-8-QAM. On the other hand, the proposed NB LDPC-coded 5-QAM and 7-QAM have even better performance than LDPC-coded QPSK. PMID:27505775

  12. Selective exfoliation of single-layer graphene from non-uniform graphene grown on Cu.

    PubMed

    Lim, Jae-Young; Lee, Jae-Hyun; Jang, Hyeon-Sik; Joo, Won-Jae; Hwang, SungWoo; Whang, Dongmok

    2015-11-13

    Graphene growth on a copper surface via metal-catalyzed chemical vapor deposition has several advantages in terms of providing high-quality graphene with the potential for scale-up, but the product is usually inhomogeneous due to the inability to control the graphene layer growth. The non-uniform regions strongly affect the reliability of the graphene in practical electronic applications. Herein, we report a novel graphene transfer method that allows for the selective exfoliation of single-layer graphene from non-uniform graphene grown on a Cu foil. Differences in the interlayer bonding energy are exploited to mechanically separate only the top single-layer graphene and transfer this to an arbitrary substrate. The dry-transferred single-layer grapheme showed electrical characteristics that were more uniform than those of graphene transferred using conventional wet-etching transfer steps. PMID:26491038

  13. The non-uniform distribution of the perihelia of near-Earth objects

    NASA Astrophysics Data System (ADS)

    JeongAhn, Youngmin; Malhotra, R.

    2013-10-01

    We show that each sub-group of NEOs (Amors, Apollos and Atens) has different observational selection effects that cause distinctive features in the apparent distribution of their angular elements. We also reveal that the NEOs' perihelia (argument of perihelion ω and longitude of perihelion π) have intrinsically non-uniform distributions caused by secular planetary perturbations: ω is non-uniform for the Apollo asteroids because of secular dynamics associated with eccentricity-ω coupling, and the Amors' π distribution is peaked along the secularly forced eccentricity vector. These secular effects are dominated by Jupiter's perturbations, and it is remarkable that this strongly chaotic population of minor planets reveals the presence of Jupiter in its angular distributions.

  14. Energy-Efficient Algorithm for Sensor Networks with Non-Uniform Maximum Transmission Range

    PubMed Central

    Yu, Yimin; Song, Chao; Liu, Ming; Gong, Haigang

    2011-01-01

    In wireless sensor networks (WSNs), the energy hole problem is a key factor affecting the network lifetime. In a circular multi-hop sensor network (modeled as concentric coronas), the optimal transmission ranges of all coronas can effectively improve network lifetime. In this paper, we investigate WSNs with non-uniform maximum transmission ranges, where sensor nodes deployed in different regions may differ in their maximum transmission range. Then, we propose an Energy-efficient algorithm for Non-uniform Maximum Transmission range (ENMT), which can search approximate optimal transmission ranges of all coronas in order to prolong network lifetime. Furthermore, the simulation results indicate that ENMT performs better than other algorithms. PMID:22163950

  15. Effect of Thermal Gradient on Vibration of Non-uniform Visco-elastic Rectangular Plate

    NASA Astrophysics Data System (ADS)

    Khanna, Anupam; Kaur, Narinder

    2016-04-01

    Here, a theoretical model is presented to analyze the effect of bilinear temperature variations on vibration of non-homogeneous visco-elastic rectangular plate with non-uniform thickness. Non-uniformity in thickness of the plate is assumed linear in one direction. Since plate's material is considered as non-homogeneous, authors characterized non-homogeneity in poisson ratio and density of the plate's material exponentially in x-direction. Plate is supposed to be clamped at the ends. Deflection for first two modes of vibration is calculated by using Rayleigh-Ritz technique and tabulated for various values of plate's parameters i.e. taper constant, aspect ratio, non-homogeneity constants and thermal gradient. Comparison of present findings with existing literature is also provided in tabular and graphical manner.

  16. Non-uniformity effects of the inter-foil distance on GEM detector performance

    NASA Astrophysics Data System (ADS)

    Yan, Huang; Han, YI; Zhi-Gang, Xiao; Zhao, Zhang; Wen-Jing, Cheng; Li-Ming, Lü; Wei-Hua, Yan; Ren-Sheng, Wang; Hong-Jie, Li; Yan, Zhang; Li-Min, Duan; Rong-Jiang, Hu; Chen-Gui, Lu; He-Run, Yang; Peng, Ma; Hai-Yan, Gao

    2016-04-01

    The non-uniformity effect of the inter-foil distance has been studied using a gaseous electron multiplication (GEM) detector with sensitive area of 50mm × 50mm. A gradient of the inter-foil distance is introduced by using spacers with different heights at the two ends of the foil gap. While the cluster size and the intrinsic spatial resolution show insignificant dependence on the inter-foil distance, the gain exhibits an approximately linear dependence on the inter-foil distance. From the slope, a quantitative relationship between the change of the inter-foil distance and the change of the gain is derived, which can be used as a method to evaluate the non-uniformity of the foil gap in the application of large-area GEM detectors. Supported by National Natural Science Foundation of China (11375094, U1332207, 11120101004), and by Tsinghua University Initiative Scientific Research Program

  17. Beam moments and angular momentum in non-uniformly polarized beams

    NASA Astrophysics Data System (ADS)

    Serna, Julio; Piquero, Gemma

    2009-05-01

    The angular momentum of non-uniformly totally polarized beams is investigated using methods from the beam characterization approach. The relationship between the elements of the beam matrix for the two components of the field and the angular momentum is given. The unconventional distribution of the polarization across the beam profile could result in contributions to both the spin and orbital terms of the angular momentum. To illustrate this, a particular example with a vortex beam is considered.

  18. Proposals for the generation of angular momentum from non-uniformly polarized beams

    NASA Astrophysics Data System (ADS)

    Alonso, Mara; Piquero, Gemma; Serna, Julio

    2012-04-01

    Several optical arrangements using non-uniformly polarized fields are proposed for generating beams with spin and/or orbital angular momentum. By choosing adequately the input beam polarization and the characteristics of the different proposed set-ups we can control the overall angular momentum of the output beam at will. The orbital angular momentum is analyzed with the beam moments theory and the spin term is evaluated using the averaged s3 Stokes parameter.

  19. Applications of anisotropic slipline theory with non-uniform lattice rotation

    NASA Astrophysics Data System (ADS)

    Pandey, Animesh; Gupta, Anurag

    2016-06-01

    Anisotropic slipline theory, with non-uniform lattice rotation field, is used to discuss new slipline solutions for the plane strain problems of punch indentation and mode 1 stationary crack in a ductile single crystal with piecewise linear yield locus. The proposed solution allows for both linear dislocation arrays and sectors with bulk dislocation density. Such features provide considerable latitude in the number of allowable stress discontinuities, and their orientation, when compared to the solutions which assume uniform lattice rotation.

  20. Phase-locked laser array having a non-uniform spacing between lasing regions

    NASA Technical Reports Server (NTRS)

    Ackley, Donald E. (Inventor)

    1986-01-01

    A phase-locked semiconductor array wherein the lasing regions of the array are spaced an effective distance apart such that the modes of oscillation of the different lasing regions are phase-locked to one another. The center-to-center spacing between the lasing regions is non-uniform. This variation in spacing perturbs the preferred 180.degree. phase difference between adjacent lasing regions thereby providing an increased yield of arrays exhibiting a single-lobed, far-field radiation pattern.

  1. Non-uniform composite representation of hydroelectric systems for long-term hydrothermal scheduling

    SciTech Connect

    Cruz, G. da Jr.; Soares, S.

    1995-12-31

    This paper presents a non-uniform composite representation of hydroelectric systems for use in long-term hydrothermal scheduling. This representation was developed from reservoir operational rules based on optimal reservoir trajectories obtained with a deterministic hydrothermal scheduling algorithm. A test system consisting of {tau} large hydroelectric plants of the Southeast Brazilian Power System with 12,572 MW of installed power capacity was selected for a case study. Operational cost comparisons with the classical uniform composite representation reveal significant savings.

  2. An introduction to the theory of NON-uniformity of hygrothermal constituent of the environment

    NASA Astrophysics Data System (ADS)

    Jokl, M. V.

    1989-12-01

    Non-uniformity of the hygrothermal constituent of the environment (NUN) causes problems not only of hot workplaces in industry, but also in lightweight buildings, and air-conditioned and even ventilated buildings. It is almost impossible to avoid cold draughts, unilateral thermal radiation etc. in such situations. The theory and definition of NUN in space and in time, and NUN climatic (convective, radiant, perspiratory) and NUN conductive are described.

  3. An introduction to the theory of NON-uniformity of hygrothermal constituent of the environment.

    PubMed

    Jokl, M V

    1989-12-01

    Non-uniformity of the hygrothermal constituent of the environment (NUN) causes problems not only of hot workplaces in industry, but also in lightweight buildings, and air-conditioned and even ventilated buildings. It is almost impossible to avoid cold draughts, unilateral thermal radiation etc. in such situations. The theory and definition of NUN in space and in time, and NUN climatic (convective, radiant, perspiratory) and NUN conductive are described. PMID:2613363

  4. Non-uniform cosine modulated filter banks using meta-heuristic algorithms in CSD space.

    PubMed

    Kalathil, Shaeen; Elias, Elizabeth

    2015-11-01

    This paper presents an efficient design of non-uniform cosine modulated filter banks (CMFB) using canonic signed digit (CSD) coefficients. CMFB has got an easy and efficient design approach. Non-uniform decomposition can be easily obtained by merging the appropriate filters of a uniform filter bank. Only the prototype filter needs to be designed and optimized. In this paper, the prototype filter is designed using window method, weighted Chebyshev approximation and weighted constrained least square approximation. The coefficients are quantized into CSD, using a look-up-table. The finite precision CSD rounding, deteriorates the filter bank performances. The performances of the filter bank are improved using suitably modified meta-heuristic algorithms. The different meta-heuristic algorithms which are modified and used in this paper are Artificial Bee Colony algorithm, Gravitational Search algorithm, Harmony Search algorithm and Genetic algorithm and they result in filter banks with less implementation complexity, power consumption and area requirements when compared with those of the conventional continuous coefficient non-uniform CMFB. PMID:26644921

  5. Rapid analysis of non-uniformly sampled pulsed field gradient data for velocity estimation.

    PubMed

    Raghavan, K; Park, J C; Pavlovskaya, G E; Gibbs, S J

    2001-06-01

    Bretthorst's recent generalization of the Lomb-Scargle periodogram shows that a sufficient statistic for frequency estimation from non-uniformly, but simultaneously sampled quadrature data is equivalent to the FFT of those data with the missing samples replaced by zeros. We have applied this concept to the rapid analysis of pulsed field gradient MRI data which have been non-uniformly sampled in the velocity encoding wave vector q. For a small number of q samples, it is more computationally efficient to calculate the periodogram directly rather than using the FFT algorithm with a large number of zeros. The algorithm we have implemented for finding the peak of the generalized periodogram is simple and robust; it involves repeated apodization and grid searching of the periodogram until the desired velocity resolution is achieved. The final estimate is refined by quadratic interpolation. We have tested the method for fully developed Poiseuille flow of a Newtonian fluid and have demonstrated substantial improvement in the precision of velocity measurement achievable in a fixed acquisition time with non-uniform sampling. The method is readily extendible to multidimensional data. Analysis of a 256 by 256 pixel image with 8 q samples and an effective velocity resolution of better than 1/680 of the Nyquist range requires approximately 1 minute computation time on a 400 MHz SUN Ultrasparc II processor. PMID:11672628

  6. The magneto-optical properties of non-uniform graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Chung, Hsien-Ching; Lin, Ming-Fa

    2015-03-01

    When synthesizing few-layer graphene nanoribbons (GNRs), non-uniform GNRs would be made simultaneously. Recently, the non-uniform GNRs, which is a stack of two GNRs with unequal widths, have been fabricated by mechanically exfoliated from bulk graphite. Some theoretical predictions have been reported, such as gap opening and transport properties. Under the influence of magnetic fields, magnetic quantization takes place and drastically changes the electronic properties. By tuning the geometric configuration, four categories of magneto-electronic spectra are exhibited. (1) The spectrum is mostly contributed by quasi-Landau levels (QLLs) of monolayer GNRs. (2) The spectrum displays two groups of QLLs, and the non-uniform GNR behaves like a bilayer one. (3) An intermediate category, the spectrum is composite disordered. (4) The spectrum presents the coexistence of monolayer and bilayer spectra. In this work, the magneto-electronic and optical properties for different geometric configurations are given, such as energy dispersions, density of states, wave functions, and magneto-absorption spectra are presented. Furthermore, the transformation between monolayer and bilayer spectra as well as the coexistence of monolayer and bilayer spectra are discussed in detail. One of us (Hsien-Ching Chung) thanks Ming-Hui Chung and Su-Ming Chen for financial support. This work was supported in part by the National Science Council of Taiwan under Grant Number 98-2112-M-006-013-MY4.

  7. Characterization of non-uniformity and bias-heating for uncooled bolometer FPA detectors using simulator

    NASA Astrophysics Data System (ADS)

    Lee, Jungeon; Kyung, Chong-Min

    2013-06-01

    There are some difficulties in the development of uncooled focal plane array (FPA) detectors due to the absence of full simulation model which reflects the characterization of FPA detectors by variations of various parameters. In this paper we propose the simulator for the both readout integrated circuit (ROIC) and bolometer FPA which is based on a thermal equivalence equation of bolometer and mathematical modeling of optical and electrical part in infrared sensor system. The simulator shows the characteristics and the behaviors of individual components of infrared sensor system in the transient-state and steady-state. We present here the simulation results for output characteristics of detectors owing to variations of parameters induced non-uniformity in FPA detectors and find the dominant parameter to be the leading source non-uniformity in FPA detectors. We also present the simulation results for some typical ROICs to cancel the bias-heating which wastes most of the dynamic range of infrared sensor system. These show the effectiveness of compensation for the bias-heating according to variations of parameters. Using the proposed simulator we can expect the quantitative amount of non-uniformity due to the statistical variations in various processing steps and design of ROIC components. It can be used for the systematic design of infrared sensor system which cannot be performed in fabrication procedure.

  8. Bubble Detachment in Variable Gravity Under the Influence of a Non-Uniform Electric Field

    NASA Technical Reports Server (NTRS)

    Chang, Shinan; Herman, Cila; Iacona, Estelle

    2002-01-01

    The objective of the study reported in this paper is to investigate the effects of variable, reduced gravity on the formation and detachment behavior of individual air bubbles under the influence of a non-uniform electric field. For this purpose, variable gravity experiments were carried out in parabolic nights. The non-uniform electric field was generated by a spherical electrode and a plate electrode. The effect of the magnitude of the non-uniform electric field and gravity level on bubble formation, development and detachment at an orifice was investigated. An image processing code was developed that allows the measurement of bubble volume, dimensions and contact angle at detachment. The results of this research can be used to explore the possibility of enhancing boiling heat transfer in the variable and low gravity environments by substituting the buoyancy force with a force induced by the electric field. The results of experiments and measurements indicate that the level of gravity significantly affects bubble shape, size and frequency. The electric field magnitude also influences bubble detachment, however, its impact is not as profound as that of variable gravity for the range of electric field magnitudes investigated in the present study.

  9. Optical sensitivity non-uniformity analysis and optimization of a tilt optical readout focal plane array

    NASA Astrophysics Data System (ADS)

    Fu, Jianyu; Shang, Haiping; Shi, Haitao; Li, Zhigang; Ou, Yi; Chen, Dapeng; Zhang, Qingchuan

    2016-02-01

    An optical readout focal plane array (FPA) usually has a differently tilted reflector/absorber at the initial state due to the micromachining technique. The angular deviation of the reflector/absorber has a strong impact on the optical sensitivity non-uniformity, which is a key factor which affects the imaging uniformity. In this study, a theoretical analysis has been developed, and it is found that the stress matching in SiO2-Aluminum (Al) bilayer leg could make a contribution towards reducing the optical sensitivity non-uniformity. Ion implantation of phosphorus (P) has been utilized to control the stress in SiO2 film. By controlling the implantation energy and dose, the stress and stress stability are modified. The optical readout FPA has been successfully fabricated with the stress-control technique based on P+ implantation. It is demonstrated that the gray response non-uniformity of optical readout FPA has decreased from 25.69% to 10.7%.

  10. Correlation-based methods in calibrating an FBG sensor with strain field non-uniformity

    NASA Astrophysics Data System (ADS)

    Cieszczyk, S.

    2015-12-01

    Fibre Bragg gratings have many sensing applications, mainly for measuring strain and temperature. The physical quantity that influences grating uniformly along its length causes a related shift of the Bragg wavelength. Many peak detection algorithms have been proposed, among which the most popular are the detection of maximum intensity, the centroid detection, the least square method, the cross-correlation, auto-correlation and fast phase correlation. Nonuniform gratings elongation is a cause of spectrum deformation. The introduction of non-uniformity can be intentional or appear as an unintended effect of placing sensing elements in the tested structure. Heterogeneous impacts on grating may result in additional errors and the difficulty in tracking the Bragg wavelength based on a distorted spectrum. This paper presents the application of correlation methods of peak wavelength shifts estimation for non-uniform Bragg grating elongation. The autocorrelation, cross-correlation and fast phase correlation algorithms are considered and experimental spectra measured for axisymmetric strain field along the Bragg grating are analyzed. The strain profile consists of constant and variable components. The results of this study indicate the properties of correlation algorithms applied to moderately non-uniform elongation of an FBG sensor.

  11. Experimental derivation of the fluence non-uniformity correction for air kerma near brachytherapy linear sources

    SciTech Connect

    Vianello, E. A.; Almeida, C. E. de

    2008-07-15

    In brachytherapy, one of the elements to take into account for measurements free in air is the non-uniformity of the photon fluence due to the beam divergence that causes a steep dose gradient near the source. The correction factors for this phenomenon have been usually evaluated by two available theories by Kondo and Randolph [Radiat. Res. 13, 37-60 (1960)] and Bielajew [Phys. Med. Biol. 35, 517-538 (1990)], both conceived for point sources. This work presents the experimental validation of the Monte Carlo calculations made by Rodriguez and deAlmeida [Phys. Med. Biol. 49, 1705-1709 (2004)] for the non-uniformity correction specifically for a Cs-137 linear source measured using a Farmer type ionization chamber. The experimental values agree very well with the Monte Carlo calculations and differ from the results predicted by both theoretical models widely used. This result confirms that for linear sources there are some important differences at short distances from the source and emphasizes that those theories should not be used for linear sources. The data provided in this study confirm the limitations of the mentioned theories when linear sources are used. Considering the difficulties and uncertainties associated with the experimental measurements, it is recommended to use the Monte Carlo data to assess the non-uniformity factors for linear sources in situations that require this knowledge.

  12. Effect of non-uniform surface resistance on the quality factor of superconducting niobium cavity

    NASA Astrophysics Data System (ADS)

    Tan, Weiwei; Lu, Xiangyang; Yang, Ziqin; Zhao, Jifei; Yang, Deyu; Yang, Yujia

    2016-08-01

    The formula Rs = G /Q0 is commonly used in the calculation of the surface resistance of radio frequency niobium superconducting cavities. The applying of such equation is under the assumption that surface resistance is consistent over the cavity. However, the distribution of the magnetic field varies over the cavity. The magnetic field in the equator is much higher than that in the iris. According to Thermal Feedback Theory, it leads non-uniform distribution of the density of heat flux, which results in a different temperature distribution along the cavity inter surface. The BCS surface resistance, which depends largely on the temperature, is different in each local inner surface. In this paper, the effect of surface non-uniform resistance on the quality factor has been studied, through the calculation of Q0 in the original definition of it. The results show that it is necessary to consider the non-uniform distribution of magnetic field when the accelerating field is above 20 MV/m for TESLA cavities. Also, the effect of inhomogeneity of residual resistance on the quality factor is discussed. Its distribution barely affects the quality factor.

  13. Improving feature size uniformity from interference lithography systems with non-uniform intensity profiles

    NASA Astrophysics Data System (ADS)

    Chang, En-Chiang; Mikolas, David; Lin, Pao-Te; Schenk, Tony; Wu, Chien-Li; Sung, Cheng-Kuo; Fu, Chien-Chung

    2013-11-01

    The non-uniform intensity profile of Gaussian-like laser beams used in interference lithography (IL) leads to a non-uniform dose and feature size distribution across the sample. Previously described methods to improve dose uniformity are reviewed. However, here we examine the behavior of the non-uniformity from the viewpoint of photoresist response rather than the IL system configuration. Samples with a fixed intra-sample dose profile were exposed with an increasing average dose. A line/space pattern with a period of 240 nm across an area of 2 × 2 cm2 was produced using IL on identical samples using a HeCd laser operated at 325 nm and a Lloyd’s mirror IL system. A binary model of photoresist response predicts that the absolute range of line widths in nanometers should be significantly reduced as the overall sample dose is increased. We have experimentally verified a reduction in the range of line widths within a given sample from 50 to 16 nm as the overall dose is increased by only 60%. This resulted in a drop in the narrowest line width from 120 to 65 nm. An etch process is demonstrated to increase the line width by generating a wider secondary chrome hard mask from the narrowly patterned primary chrome hard mask. The subsequent fabrication of a silicon nanoimprint mold is used as a demonstration of the technique.

  14. Comparison of FBP and Iterative Algorithms with Non-Uniform Angular Sampling

    PubMed Central

    Zeng, Gengsheng L.

    2014-01-01

    Some people may believe that the filtered backprojection (FBP) algorithm does not work if the projection data are measured non-uniformly. Some may also believe that iterative algorithms can automatically handle the non-uniformly sampled data in the projector/backprojector. This paper claims that the FBP algorithm can effectively handle the situation where the angular sampling is not uniform. This paper compares the images that are reconstructed by both the FBP and the iterative Landweber algorithms when the angular sampling is nonuniform. When the iteration number is low, the iterative algorithms do not handle the non-uniform sampling properly. A weighting strategy is then suggested and it makes the image resolution more isotropic. In few-view tomography, the FBP and iterative algorithms both perform poorly if no other prior information is used. We have made the following observations: 1) When using an iterative algorithm, one must use early solutions due to noise amplification. 2) An early solution can have anisotropic spatial resolution if the angular sampling is not uniform. 3) The anisotropic resolution problem can be solved by introducing angle dependent weighting, which is not noise dependent. 4) The weighting is not effective when the iteration number is large. The weighting only affects the early solutions, and does not affect the converged solution. 5) When the iteration number is large, the model-mismatch errors are amplified and cause artifacts in the image. 6) The FBP algorithm is not sensitive to the model-mismatch errors, and does not have the “early solution” problems. 7) In few-view tomography, both FBP and iterative algorithms perform poorly, while the FBP algorithm gives a sharper image than the iterative algorithm does. PMID:25678716

  15. Mobilization of phenol and dichlorophenol in unsaturated soils by non-uniform electrokinetics.

    PubMed

    Luo, Qishi; Zhang, Xihui; Wang, Hui; Qian, Yi

    2005-06-01

    The poor mobility of organic pollutants in contaminated sites frequently results in slow remediation processes. Organics, especially hydrophobic compounds, are generally retained strongly in soil matrix as a result of sorption, sequestration, or even formation into non-aqueous-phase liquids and their mobility is thus greatly reduced. The objective of this study was to evaluate the feasibility of using non-uniform electrokinetic transport processes to enhance the mobility of organic pollutants in unsaturated soils with no injection reagents. Phenol and 2,4-dichlorophenol (2,4-DCP), and kaolin and a natural sandy loam soil were selected as model organics and soils, respectively. The results showed that non-uniform electrokinetics can accelerate the desorption and movement of phenol and 2,4-DCP in unsaturated soils. Electromigration and electroosmotic flow were the main driving forces, and their role in the mobilization of phenol and 2,4-DCP varied with soil pH. The movement of 2,4-DCP in the sandy loam towards the anode (about 1.0 cmd(-1)V(-1)) was 1.0-1.5 cmd(-1)V(-1) slower than that in the kaolin soil, but about 0.5 cmd(-1)V(-1) greater than that of phenol in the sandy loam. When the sandy loam was adjusted to pH 9.3, the movement of phenol and 2,4-DCP towards the anode was about twice and five times faster than that at pH 7.7, respectively. The results also demonstrated that the movement of phenol and 2,4-DCP in soils can be easily controlled by regulating the operational mode of electric field. It is believed that non-uniform electrokinetics has the potential for practical application to in situ remediation of organics-contaminated sites. PMID:15857640

  16. Axial development and radial non-uniformity of flow in packed columns.

    PubMed

    Park, Jaekeun C; Raghavan, Karthik; Gibbs, Stephen J

    2002-02-01

    Flow inhomogeneity and axial development in low-pressure chromatographic columns have been studied by magnetic resonance imaging velocimetry. The columns studied included (a) an 11.7-mm I.D. column packed with either 50 microm diameter porous polyacrylamide, or 99 or 780 microm diameter impermeable polystyrene beads, and (b) a 5-mm I.D. column commercially packed with 10 microm polymeric beads. The packing methods included gravity settling, slurry packing, ultrasonication, and dry packing with vibration. The magnetic resonance method used averaged apparent fluid velocity over both column cross-sections and fluid displacements greater than one particle diameter and hence permits assessment of macroscopic flow non-uniformities. The results confirm that now non-uniformities induced by the conical distributor of the 11.7-mm I.D. column or the presence of voids at the column entrance relax on a length scale of the column radius. All of the 11.7-mm I.D. columns examined exhibit near wall channeling within a few particle diameters of the wall. The origins of this behavior are demonstrated by imaging of the radial dependence of the local porosity for a column packed with 780 microm beads. Columns packed with the 99-microm beads exhibit reduced flow in a region extending from ten to three-to-five particle diameters from the wall. This velocity reduction is consistent with a reduced porosity of 0.35 in this region as compared to approximately 0.43 in the bulk of the column. Ultrasonicated and dry-packed columns exhibit enhanced flow in a region located between approximately eight and 20 particle diameters from the wall. This enhancement maybe caused by packing density inhomogeneity and/or particle size segregation caused by vibration during the packing process. No significant non-uniformities on length scales of 20 microm or greater were observed in the commercially packed column packed with 10 microm particles. PMID:11860146

  17. Forensic use of photo response non-uniformity of imaging sensors and a counter method.

    PubMed

    Dirik, Ahmet Emir; Karaküçük, Ahmet

    2014-01-13

    Analogous to use of bullet scratches in forensic science, the authenticity of a digital image can be verified through the noise characteristics of an imaging sensor. In particular, photo-response non-uniformity noise (PRNU) has been used in source camera identification (SCI). However, this technique can be used maliciously to track or inculpate innocent people. To impede such tracking, PRNU noise should be suppressed significantly. Based on this motivation, we propose a counter forensic method to deceive SCI. Experimental results show that it is possible to impede PRNU-based camera identification for various imaging sensors while preserving the image quality. PMID:24515007

  18. Non-uniformly polarized beams across their transverse profiles: an introductory study for undergraduate optics courses

    NASA Astrophysics Data System (ADS)

    Piquero, Gemma; Vargas-Balbuena, Javier

    2004-11-01

    We provide a simple theoretical study of beams non-uniformly polarized across their transverse sections which can be introduced in undergraduate optics courses. In order to generate such beams we propose to use a slightly convergent (or divergent) linearly and uniformly polarized beam impinging on an anisotropic uniaxial material with the beam propagation direction along the optic axis. Analytical expressions for the Jones vector, Stokes parameters, ellipticity and azimuth at each point of the transverse section, perpendicular to the propagation direction, are obtained at the output of this system. By means of these parameters a detailed description of the state of polarization across the transverse profile is given.

  19. Pull-in analysis of non-uniform microcantilever beams under large deflection

    NASA Astrophysics Data System (ADS)

    Singh, Sajal Sagar; Pal, Prem; Pandey, Ashok Kumar

    2015-11-01

    Cantilever beams under the influence of electrostatic force form an important subclass of microelectromechanical system (MEMS) and nanoelectromechanical system. Most of the studies concerning these micro-nano resonators are centered around uniform cantilever beams. In this paper, we have investigated another class of micro-resonators consisting of non-uniform cantilever beams. The study is focused around investigating pull-in voltage and resonance frequency of non-uniform cantilever beams when they operate in the linear regime about different static equilibriums. In this paper, we term this frequency as "linear frequency." Calculation of the linear frequency is done at different static equilibriums corresponding to different DC voltages. We have studied two classes of beams, one with increasing cross sectional area from the clamped edge (diverging beam) and other with decreasing cross sectional area from the clamped edge (converging beam). Within each class, we have investigated beams with linear as well as quartic variation in width. We start by obtaining Euler beam equation for non-uniform cantilever beams considering large deflection and their corresponding exact mode shapes from the linear equation. Subsequently, using the Galerkin method based on single mode approximation, we obtain static and dynamic modal equations for finding pull-in voltage and resonance frequency as a function of DC voltage, respectively. We found that the linear frequency of converging beams increases with increase in non-uniform parameter (α) while those of diverging beams decreases with α. A similar trend is observed for pull-in voltage. Within the converging class, beams with quartic variation in width show significant increase in both frequency and pull-in voltage as compared to corresponding linearly tapered beams. In quantitative terms, converging beams with quartic variation in width and α=-0.6 showed an increase in linear frequency by a factor of 2.5 times and pull-in voltage

  20. Streamer initiation and propagation in insulating oil in weakly non-uniform fields under impulse conditions

    SciTech Connect

    Badent, R.; Kist, K.; Schwab, A.J.

    1996-12-31

    This paper deals with the investigation of prebreakdown phenomenon in insulating oil in weakly non-uniform fields of rod-plane geometries with gaps up to 100 mm under impulse voltages of both polarities up to 700 kV. As with the point-plane configuration, the rod-plane geometry shows a decrease of the time to breakdown with increasing voltage rate-of-rise. At a specific rate, a significantly shorter breakdown time is observed both for positive and negative polarities. Beyond this discontinuity range breakdown time decreases again but with lower rates.

  1. Re-defining the cerebellar cortex as an assembly of non-uniform Purkinje cell microcircuits

    PubMed Central

    Cerminara, Nadia L; Lang, Eric J; Sillitoe, Roy V; Apps, Richard

    2015-01-01

    The adult mammalian cerebellar cortex is generally assumed to have a uniform cytoarchitecture. Differences in cerebellar function are thought to arise, in the main, through distinct patterns of input and output connectivity, rather than as a result of variations in cortical microcircuitry. However, evidence from anatomical, physiological and genetic studies is increasingly challenging this orthodoxy and there are now various lines of evidence that the cerebellar cortex is non uniform. Here we develop the hypothesis that regional differences in cerebellar cortical microcircuit properties lead to important differences in information processing. PMID:25601779

  2. A simple model for characterizing non-uniform fibre-based composites and networks.

    PubMed

    Chatterjee, Avik P

    2011-04-20

    A mean-field model is presented that describes non-uniformities in the spatial distribution of fibres in networks and composites in terms of fluctuations in the local composition. The mean pore radius, specific surface area, lineal path function, and chord length probability density are expressed as functions of the fibre volume fraction within a heuristic formalism. The impact of statistical heterogeneities in the fibre distribution upon the elastic moduli is assessed within the semi-empirical Reuss-Voigt-Hill averaging scheme. Results from illustrative calculations suggest that such macroscopically averaged material properties are particularly sensitive to variations in the mean pore radius. PMID:21436504

  3. The impact of non-uniform capsid charge density on virus assembly

    NASA Astrophysics Data System (ADS)

    Li, Siyu; Erdemci-Tandogan, Gonca; Wagner, Jef; Zandi, Roya

    Many spherical viruses efficiently encapsulate their genome into shells (capsids) with icosahedral symmetry. Under many circumstances, this process is spontaneous and is primarily driven by the electrostatic interaction between positively charged capsid proteins and negatively charged genome. Through the free energy minimization of a generic potential, we calculate the optimal encapsulated genome length. In this talk, I will present our results due to a non-uniform charge distribution on the shell and its impact on the optimal size of encapsulated genome. This work was supported by the National Science Foundation through Grant No. DMR-13-10687.

  4. Influence of a non-uniform stress on the electromechanical transduction coefficient of a magnetostrictive unimorph

    NASA Astrophysics Data System (ADS)

    Starke, E.; Marschner, U.; Pfeifer, G.; Fischer, W.-J.; Flatau, A. B.

    2010-04-01

    In this paper an electromechanical network model of a magnetostrictive unimorph structure, acting as solenoid coil core, is developed. For typical applications a non-uniform stress distribution in the magnetostrictive layer results which is simulated via FEM. This phenomenon leads to a spatial varying electromechanical transduction coefficient for large deflections and was taken into account by coupled finite electromechanical network elements. By simplifying the finite network model an easy to use new network model is obtained which enables the fast analysis of the system and optimization of sensor and actor properties.

  5. A dispersion relation in bidust acoustic wave in non uniform stratified plasma

    SciTech Connect

    Valdeblanquez, E.

    2006-12-04

    Low frequencies waves are studied in plasma with two kind of dusty grains. Also considered are stratified plasma with layers of different densities to that of the main plasma. In this analysis each dust species is treated with a simplified model of fluid equations, and electrons and ions are determined by a Boltzmann factor. Relative velocities between each species and the non uniform plasma is considered in order to study instabilities. In cases in which the speed or the density of current of the charged dust grains is zero, the dispersion equation is recovered.

  6. Non-uniform absorption of terahertz radiation on superconducting hot electron bolometer microbridges

    SciTech Connect

    Miao, W.; Zhang, W.; Zhong, J. Q.; Shi, S. C.; Delorme, Y.; Lefevre, R.; Feret, A.; Vacelet, T.

    2014-02-03

    We interpret the experimental observation of a frequency-dependence of superconducting hot electron bolometer (HEB) mixers by taking into account the non-uniform absorption of the terahertz radiation on the superconducting HEB microbridge. The radiation absorption is assumed to be proportional to the local surface resistance of the HEB microbridge, which is computed using the Mattis-Bardeen theory. With this assumption the dc and mixing characteristics of a superconducting niobium-nitride (NbN) HEB device have been modeled at frequencies below and above the equilibrium gap frequency of the NbN film.

  7. Non-Uniformities in Thin-Film Cadmium Telluride Solar Cells Using Electroluminescence and Photoluminescence: Preprint

    SciTech Connect

    Zaunbrecher, K.; Johnston, S.; Yan, F.; Sites, J.

    2011-07-01

    It is the purpose of this research to develop specific imaging techniques that have the potential to be fast, in-line tools for quality control in thin-film CdTe solar cells. Electroluminescence (EL) and photoluminescence (PL) are two techniques that are currently under investigation on CdTe small area devices made at Colorado State University. It is our hope to significantly advance the understanding of EL and PL measurements as applied to CdTe. Qualitative analysis of defects and non-uniformities is underway on CdTe using EL, PL, and other imaging techniques.

  8. Image retargeting using non-uniform scaling with adaptive local search window

    NASA Astrophysics Data System (ADS)

    Wang, Shanshan; Abdel-Dayem, Amr

    2011-10-01

    This paper presents a new content-aware image-retargeting scheme, based on non-uniform scaling, to adaptively adjust the image's dimensions for various screen sizes. Based on an importance map, the energy contribution for each line in the reduced dimension to the overall energy within the image is computed. Then, the image is adaptively mapped and resampled based on the energy contribution function. Experimental results showed that the performance of the proposed scheme is comparable to seam carving in visual quality. However, it is computationally less expensive.

  9. Non-uniform FFT for the finite element computation of the micromagnetic scalar potential

    NASA Astrophysics Data System (ADS)

    Exl, L.; Schrefl, T.

    2014-08-01

    We present a quasi-linearly scaling, first order polynomial finite element method for the solution of the magnetostatic open boundary problem by splitting the magnetic scalar potential. The potential is determined by solving a Dirichlet problem and evaluation of the single layer potential by a fast approximation technique based on Fourier approximation of the kernel function. The latter approximation leads to a generalization of the well-known convolution theorem used in finite difference methods. We address it by a non-uniform FFT approach. Overall, our method scales O(M+N+Nlog N) for N nodes and M surface triangles. We confirm our approach by several numerical tests.

  10. Gravitational Influences on Flame Propagation Through Non-Uniform, Premixed Gas Systems

    NASA Technical Reports Server (NTRS)

    Miller, Fletcher J.; Easton, John; Marchese, Anthony; Hovermann, Fred

    2003-01-01

    Flame propagation through non-uniformly premixed (or layered) gases has importance both in useful combustion systems and in unintentional fires. As summarized recently and in previous Microgravity Workshop papers, non-uniform premixed gas combustion receives scant attention compared to the more usual limiting cases of diffusion or uniformly premixed flames, especially regarding the role gravity plays. This paper summarizes our recent findings on gravitational effects on layered combustion along a floor, in which the fuel concentration gradient exists normal to the direction of flame spread. In an effort to understand the mechanism by which the flames spread faster in microgravity (and much faster, in laboratory coordinates, than the laminar burning velocity for uniform mixtures), we have begun making pressure measurements across the spreading flame front that are described here. Earlier researchers, testing in 1g, claimed that hydrostatic pressure differences could account for the rapid spread rates. Additionally, we present the development of a new apparatus to study flame spread in free (i.e., far from walls), non-homogeneous fuel layers formed in a flow tunnel behind an airfoil that has been tested in normal gravity.

  11. Non-Uniform Contrast and Noise Correction for Coded Source Neutron Imaging

    SciTech Connect

    Santos-Villalobos, Hector J; Bingham, Philip R

    2012-01-01

    Since the first application of neutron radiography in the 1930s, the field of neutron radiography has matured enough to develop several applications. However, advances in the technology are far from concluded. In general, the resolution of scintillator-based detection systems is limited to the $10\\mu m$ range, and the relatively low neutron count rate of neutron sources compared to other illumination sources restricts time resolved measurement. One path toward improved resolution is the use of magnification; however, to date neutron optics are inefficient, expensive, and difficult to develop. There is a clear demand for cost-effective scintillator-based neutron imaging systems that achieve resolutions of $1 \\mu m$ or less. Such imaging system would dramatically extend the application of neutron imaging. For such purposes a coded source imaging system is under development. The current challenge is to reduce artifacts in the reconstructed coded source images. Artifacts are generated by non-uniform illumination of the source, gamma rays, dark current at the imaging sensor, and system noise from the reconstruction kernel. In this paper, we describe how to pre-process the coded signal to reduce noise and non-uniform illumination, and how to reconstruct the coded signal with three reconstruction methods correlation, maximum likelihood estimation, and algebraic reconstruction technique. We illustrates our results with experimental examples.

  12. Effects of magnetic field on the interaction between terahertz wave and non-uniform plasma slab

    NASA Astrophysics Data System (ADS)

    Tian, Yuan; Ai, Xia; Han, YiPing; Guo, LiXin

    2015-10-01

    In this paper, the interaction between terahertz electromagnetic wave and a non-uniform magnetized plasma slab is investigated. Different from most of the published literatures, the plasma employed in this work is inhomogeneous in both collision frequency and electron density. Profiles are introduced to describe the non-uniformity of the plasma slab. At the same time, magnetic field is applied to the background of the plasma slab. It came out with an interesting phenomenon that there would be a valley in the absorption band as the plasma's electromagnetic characteristic is affected by the magnetic field. In addition, the valley located just near the middle of the absorption peak. The cause of the valley's appearance is inferred in this paper. And the influences of the variables, such as magnetic field strength, electron density, and collision frequency, are discussed in detail. The objective of this work is also pointed out, such as the applications in flight communication, stealth, emissivity, plasma diagnose, and other areas of plasma.

  13. Detecting damage in non-uniform beams using the dereverberated transfer function response

    NASA Astrophysics Data System (ADS)

    Purekar, A. S.; Pines, D. J.; Purekar, A. S.

    2000-08-01

    Delamination damage in composite rotorcraft flexbeams caused by excessive vibratory and fatigue loads can lead to degradation in flapwise and lagwise performance of the rotor blade. In addition, delaminations can result in rapid fatigue failure of these tailored composite elements leading to catastrophic results. A novel damage detection strategy is evaluated in this work which attempts to exploit the dereverberated transfer function response of beams with tapered geometries. This approach avoids high fidelity finite element models of damaged one-dimensional beams with non-uniform geometries. To obtain the dereverberated transfer function response, a virtual control force is applied to the reverberated transfer function response to remove resonant and anti-resonant dynamics associated with the beam's boundary conditions. Magnitude and phase characteristics between each actuator and sensor can then be used to infer changing structural properties. Analytical and experimental results suggest that this approach can be used to quantitatively and qualitatively infer delamination damage in non-uniform beams. Experimental results are displayed for beams with varying thickness and width tapers.

  14. Mixed convection flow with non-uniform heat source/sink in a doubly stratified magnetonanofluid

    NASA Astrophysics Data System (ADS)

    Mehmood, K.; Hussain, S.; Sagheer, M.

    2016-06-01

    In this study, we explore the unsteady flow of viscous nanofluid driven by an inclined stretching sheet. The novelty of the present study is to account for the effect of a non-uniform heat source/sink in a thermally and solutally stratified magnetonanofluid. Governing system of nonlinear partial differential equations is converted into a system of nonlinear ordinary differential equations. Solution of the transformed system is obtained using RK4 method with shooting technique. It is observed that increase in the values of thermal and mass stratification parameter reduce the velocity profile and increase in the values of variable thermal conductivity parameter and non-uniform heat source/sink parameters enhance the temperature distribution. Moreover, skin friction coefficient, Nusselt number and Sherwood number are discussed. Obtained results are displayed both graphically and in tabular form to illustrate the effect of different parameters on the velocity, temperature and concentration profiles. Numerical results are compared with previous published results and found to be in good agreement for special cases of the emerging parameters.

  15. On the existence of free energy densities in non-uniform fluids

    NASA Astrophysics Data System (ADS)

    Lovett, Ronald; Baus, Marc

    1992-02-01

    The perception that unambigous constructions of local thermodynamic quantities cannot be given in equilibrium but non-uniform fluids has grown out of the recognition that many distinct thermodynamic fields satisfy the existing prescriptions for these quantities. That is, the existing prescriptions for thermodynamic fields underdetermine these quantities. It is shown that in many important cases, however, the requirement that thermodynamic consistency - the hallmark of classical thermodynamics-hold on all spatial scales does lead to a complete specification of free energy densities. The development presented requires-as in thermodynamics in general-a clear view of what fields actually fix the state of a non-uniform system. In the absence of a clear experimental foundation, the present development is built upon the statistical mechanical framework supporting density functional methods. It is noted that the identification of the free energy density as a stress tensor component is clouded by the fact that the traditional stress tensor formulation actually underdetermines a stress tensor. While this confusion should have no thermodynamic consequences it is also noted that the boundary conditions which play an essential role in constructing a thermodynamically meaningful stress tensor are not explicitly stated in general.

  16. Adhesion of voids to bimetal interfaces with non-uniform energies

    NASA Astrophysics Data System (ADS)

    Zheng, Shijian; Shao, Shuai; Zhang, Jian; Wang, Yongqiang; Demkowicz, Michael J.; Beyerlein, Irene J.; Mara, Nathan A.

    2015-10-01

    Interface engineering has become an important strategy for designing radiation-resistant materials. Critical to its success is fundamental understanding of the interactions between interfaces and radiation-induced defects, such as voids. Using transmission electron microscopy, here we report an interesting phenomenon in their interaction, wherein voids adhere to only one side of the bimetal interfaces rather than overlapping them. We show that this asymmetrical void-interface interaction is a consequence of differing surface energies of the two metals and non-uniformity in their interface formation energy. Specifically, voids grow within the phase of lower surface energy and wet only the high-interface energy regions. Furthermore, because this outcome cannot be accounted for by wetting of interfaces with uniform internal energy, our report provides experimental evidence that bimetal interfaces contain non-uniform internal energy distributions. This work also indicates that to design irradiation-resistant materials, we can avoid void-interface overlap via tuning the configurations of interfaces.

  17. Adhesion of voids to bimetal interfaces with non-uniform energies

    DOE PAGESBeta

    Zheng, Shijian; Shao, Shuai; Zhang, Jian; Wang, Yongqiang; Demkowicz, Michael J.; Beyerlein, Irene J.; Mara, Nathan A.

    2015-10-21

    Interface engineering has become an important strategy for designing radiation-resistant materials. Critical to its success is fundamental understanding of the interactions between interfaces and radiation-induced defects, such as voids. Using transmission electron microscopy, here we report an interesting phenomenon in their interaction, wherein voids adhere to only one side of the bimetal interfaces rather than overlapping them. We show that this asymmetrical void-interface interaction is a consequence of differing surface energies of the two metals and non-uniformity in their interface formation energy. Specifically, voids grow within the phase of lower surface energy and wet only the high-interface energy regions. Furthermore,more » because this outcome cannot be accounted for by wetting of interfaces with uniform internal energy, our report provides experimental evidence that bimetal interfaces contain non-uniform internal energy distributions. Ultimately, this work also indicates that to design irradiation-resistant materials, we can avoid void-interface overlap via tuning the configurations of interfaces.« less

  18. Adhesion of voids to bimetal interfaces with non-uniform energies

    SciTech Connect

    Zheng, Shijian; Shao, Shuai; Zhang, Jian; Wang, Yongqiang; Demkowicz, Michael J.; Beyerlein, Irene J.; Mara, Nathan A.

    2015-10-21

    Interface engineering has become an important strategy for designing radiation-resistant materials. Critical to its success is fundamental understanding of the interactions between interfaces and radiation-induced defects, such as voids. Using transmission electron microscopy, here we report an interesting phenomenon in their interaction, wherein voids adhere to only one side of the bimetal interfaces rather than overlapping them. We show that this asymmetrical void-interface interaction is a consequence of differing surface energies of the two metals and non-uniformity in their interface formation energy. Specifically, voids grow within the phase of lower surface energy and wet only the high-interface energy regions. Furthermore, because this outcome cannot be accounted for by wetting of interfaces with uniform internal energy, our report provides experimental evidence that bimetal interfaces contain non-uniform internal energy distributions. Ultimately, this work also indicates that to design irradiation-resistant materials, we can avoid void-interface overlap via tuning the configurations of interfaces.

  19. Velocity controlled sound field reproduction by non-uniformly spaced loudspeakers

    NASA Astrophysics Data System (ADS)

    Shin, Mincheol; Nelson, Philip A.; Fazi, Filippo M.; Seo, Jeongil

    2016-05-01

    One approach to the reproduction of a sound field is to ensure the reproduction of the acoustic pressure on the surface bounding the volume within which reproduction is sought. However, this approach suffers from technical limitations when the loudspeakers used for the reproduction of the surface acoustic pressures are unevenly spaced. It is shown in this paper that sound field reproduction with a spatially non-uniform loudspeaker arrangement can be considerably improved by changing the physical quantity to be controlled on the bounding surface from pressure to particle velocity. One of the main advantages of the velocity control method is the simplicity with which the inverse problem can be regularized, irrespective of the direction of arrival of the sound to be reproduced. In addition, the velocity controlled sound field shows better reproduction of the time averaged intensity flow in the reproduction region which in turn appears to be closely linked with better human perception of sound localization. Furthermore, the proposed method results in smoother "panning functions" that describe the variation of the source outputs as a function of the angle of incidence of the sound to be reproduced. The performance of the velocity matching method has been evaluated by comparison to the conventional pressure matching method and through simulations with several non-uniform loudspeaker layouts. The simulated results were also verified with experiments and subjective tests.

  20. Spatially variant red blood cell crenation in alternating current non-uniform fieldsa

    PubMed Central

    An, Ran; Wipf, David O.; Minerick, Adrienne R.

    2014-01-01

    Alternating-current (AC) electrokinetics involve the movement and behaviors of particles or cells. Many applications, including dielectrophoretic manipulations, are dependent upon charge interactions between the cell or particle and the surrounding medium. Medium concentrations are traditionally treated as spatially uniform in both theoretical models and experiments. Human red blood cells (RBCs) are observed to crenate, or shrink due to changing osmotic pressure, over 10 min experiments in non-uniform AC electric fields. Cell crenation magnitude is examined as functions of frequency from 250 kHz to 1 MHz and potential from 10 Vpp to 17.5 Vpp over a 100 μm perpendicular electrode gap. Experimental results show higher peak to peak potential and lower frequency lead to greater cell volume crenation up to a maximum volume loss of 20%. A series of experiments are conducted to elucidate the physical mechanisms behind the red blood cell crenation. Non-uniform and uniform electrode systems as well as high and low ion concentration experiments are compared and illustrate that AC electroporation, system temperature, rapid temperature changes, medium pH, electrode reactions, and convection do not account for the crenation behaviors observed. AC electroosmotic was found to be negligible at these conditions and AC electrothermal fluid flows were found to reduce RBC crenation behaviors. These cell deformations were attributed to medium hypertonicity induced by ion concentration gradients in the spatially nonuniform AC electric fields. PMID:24753734

  1. Water-in-oil emulsification in a non-uniform alternating electric field

    NASA Astrophysics Data System (ADS)

    Choi, Suhwan; Saveliev, Alexei

    2015-11-01

    The emulsification of a water microdroplet placed in castor oil was performed using a non-uniform alternating electric field formed in the pin-to-plate geometry. A non-uniform electric field of ~40 kV/mm alternating with a frequency of 6.7 kHz was generated near the pin electrode. The applied frequency exceeded charge relaxation frequency of castor oil (0.3 Hz) and was below charge relaxation frequency of deionized water (7.8 kHz) used in the experiments. The emulsification process was captured with a CCD camera. The emulsification process started with entrainment of the water droplet in the high electric filed region near the pin electrode under the dielectrophoretic force. Upon touching the pin, the microdroplet was disintegrated in numerous channels and secondary droplets. The process continued by entrainment of secondary droplets and continuous size reduction. Three droplet breakup mechanisms were identified: drop elongation and capillary breakup, ac electrospraying of individual droplets, chain and bridge formation and decay. The quasi-steady narrow size distribution of emulsified water droplets with diameters close to 1 μm was formed after a few minutes. The generated emulsion was confined near the needle electrode due to the dielectrophoretic force. The emulsion had a well-defined boundary with a shape resembling a pendant drop suspended on the pin electrode.

  2. Analytical Quantification of the Subslab Volatile Organic Vapor Concentration from a Non-uniform Source

    PubMed Central

    Shen, Rui; Suuberg, Eric M.

    2014-01-01

    The transport of volatile organic vapors from subsurface to building involves complex processes. Since the release of the draft subsurface vapor intrusion guidance by the U.S. EPA in 2002, great progress has been made in understanding these processes in various field and modeling studies. In these studies, the importance of analyzing and predicting the subslab volatile organic vapor concentration was noted. To quantitatively predict subslab vapor concentration is, however, complicated, especially for sites located over non-uniform vapor sources. This manuscript provides a method to estimate the vapor concentration beneath the subslab using a closed-form analytical solution that can approximate full three-dimensional modeling results, but does not require the use of advanced numerical simulation. This method allows prediction of the subslab vapor concentration profile beneath the slab for various source configurations, given inputs of building slab dimension and source depth. The interaction of the influences of non-uniform source and the slab capping effect on the subslab vapor concentration is addressed. PMID:24639604

  3. Effects of magnetic field on the interaction between terahertz wave and non-uniform plasma slab

    SciTech Connect

    Tian, Yuan; Han, YiPing; Guo, LiXin; Ai, Xia

    2015-10-15

    In this paper, the interaction between terahertz electromagnetic wave and a non-uniform magnetized plasma slab is investigated. Different from most of the published literatures, the plasma employed in this work is inhomogeneous in both collision frequency and electron density. Profiles are introduced to describe the non-uniformity of the plasma slab. At the same time, magnetic field is applied to the background of the plasma slab. It came out with an interesting phenomenon that there would be a valley in the absorption band as the plasma's electromagnetic characteristic is affected by the magnetic field. In addition, the valley located just near the middle of the absorption peak. The cause of the valley's appearance is inferred in this paper. And the influences of the variables, such as magnetic field strength, electron density, and collision frequency, are discussed in detail. The objective of this work is also pointed out, such as the applications in flight communication, stealth, emissivity, plasma diagnose, and other areas of plasma.

  4. Gravitational Influences on Flame Propagation through Non-Uniform, Premixed Gas Systems

    NASA Technical Reports Server (NTRS)

    Miller, Fletcher J.; Easton, John; Ross, Howard D.; Marchese, Anthony; Perry, David; Kulis, Michael

    2001-01-01

    Flame propagation through non-uniformly premixed (or layered) gases has importance both in useful combustion systems and in unintentional fires. As summarized previously, non-uniform premixed gas combustion receives scant attention compared to the more usual limiting cases of diffusion or uniformly premixed flames, especially regarding the role gravity plays. This paper summarizes our progress on furthering the knowledge of layered combustion, in which a fuel concentration gradient exists normal to the direction of flame spread. We present experimental and numerical results for flame spread through propanol-air layers formed near the flash point temperature (25 C) or near the stoichiometric temperature (33 C). Both the model and experimental results show that the removal of gravity results in a faster spreading flame, by as much as 80% depending on conditions. This is exactly the opposite effect as that predicted by an earlier model reported. We also found that having a gallery lid results in faster flame spread, an effect more pronounced at normal gravity, demonstrating the importance of enclosure geometry. Also reported here is the beginning of our spectroscopic measurements of fuel vapor.

  5. Adhesion of voids to bimetal interfaces with non-uniform energies

    PubMed Central

    Zheng, Shijian; Shao, Shuai; Zhang, Jian; Wang, Yongqiang; Demkowicz, Michael J.; Beyerlein, Irene J.; Mara, Nathan A.

    2015-01-01

    Interface engineering has become an important strategy for designing radiation-resistant materials. Critical to its success is fundamental understanding of the interactions between interfaces and radiation-induced defects, such as voids. Using transmission electron microscopy, here we report an interesting phenomenon in their interaction, wherein voids adhere to only one side of the bimetal interfaces rather than overlapping them. We show that this asymmetrical void-interface interaction is a consequence of differing surface energies of the two metals and non-uniformity in their interface formation energy. Specifically, voids grow within the phase of lower surface energy and wet only the high-interface energy regions. Furthermore, because this outcome cannot be accounted for by wetting of interfaces with uniform internal energy, our report provides experimental evidence that bimetal interfaces contain non-uniform internal energy distributions. This work also indicates that to design irradiation-resistant materials, we can avoid void-interface overlap via tuning the configurations of interfaces. PMID:26486278

  6. Finite volume analysis the thermal behavior of electrode non-uniformity

    NASA Astrophysics Data System (ADS)

    Ye, Wei-Biao

    2016-08-01

    Non-uniformity in electrode thickness can result in quality control defectively. To quantitatively detect the non-uniformity of electrode thickness during the manufacturing processes. A heat transfer model based on heat conduction equation has been employed to provide the computational study. The effects of boundary conditions of adiabatic and periodic walls along coating direction, electrode thickness changes from 3.9 to 30.0 %, and two types of located region in thickness changes, as well as anode and cathode material properties on temperature change percents are analyzed and discussed in detail. The relationship between thickness changes percents and temperature change percents of electrode is established. It is found that the thickness changes have a sensitivity of 1 % changes in electrode thickness will result in 1 % in temperature changes at an inherent time point. The selected time points are 0.008 or 0.01 s for cathode and 0.004 s for anode. The minimum thickness change percent 3.9 % will be detected. Further, the comparison of the computational results with experimental ones shows the validity of the heat conduction model.

  7. Readout integrated circuit for microbolometer with an analog non-uniformity correction

    NASA Astrophysics Data System (ADS)

    Hwang, C. H.; Woo, D. H.; Lee, Y. S.; Lee, H. C.

    2005-10-01

    We have developed a microbolometer readout integrated circuit (ROIC) that corrects the non-uniformity in analog operation and acts in both normal mode and edge detection mode. A capacitive transimpedance amplifier (CTIA) has been employed as the input circuit of the microbolometer. Generally, when fabricating microbolometer focal plane arrays (FPAs), offset-error and gain-error in the inter-microbolometer are induced by fabrication error. They are shown as fixed pattern noise (FPN) in the infrared image. In the present study, a circuit correcting the offset-error and the gain-error in the normal mode by controlling the bias and the integration capacitance of the CTIA is proposed. This circuit does not require an additional DSP chip, and the non-uniformity is corrected before the analog to digital conversion (ADC). Thus, it can utilize 3-4 bits lower ADC compared to the conventional readout circuit. In the edge detection mode, after correcting the gain-error in two adjacent pixels, edge detection can be realized by subtracting their signal without the DSP. We have designed the suggested circuit to output a 10bit level effective infrared signal using 0.35um 2-poly 3-metal CMOS technology.

  8. A method for real time detecting of non-uniform magnetic field

    NASA Astrophysics Data System (ADS)

    Marusenkov, Andriy

    2015-04-01

    The principle of measuring magnetic signatures for observing diverse objects is widely used in Near Surface work (unexploded ordnance (UXO); engineering & environmental; archaeology) and security and vehicle detection systems as well. As a rule, the magnitude of the signals to be measured is much lower than that of the quasi-uniform Earth magnetic field. Usually magnetometers for these purposes contain two or more spatially separated sensors to estimate the full tensor gradient of the magnetic field or, more frequently, only partial gradient components. The both types (scalar and vector) of magnetic sensors could be used. The identity of the scale factors and proper alignment of the sensitivity axes of the vector sensors are very important for deep suppression of the ambient field and detection of weak target signals. As a rule, the periodical calibration procedure is used to keep matching sensors' parameters as close as possible. In the present report we propose the technique for detection magnetic anomalies, which is almost insensitive to imperfect matching of the sensors. This method based on the idea that the difference signals between two sensors are considerably different when the instrument is rotated or moved in uniform and non-uniform fields. Due to the misfit of calibration parameters the difference signal observed at the rotation in the uniform field is similar to the total signal - the sum of the signals of both sensors. Zero change of the difference and total signals is expected, if the instrument moves in the uniform field along a straight line. In contrast, the same move in the non-uniform field produces some response of each of the sensors. In case one measures dB/dx and moves along x direction, the sensors signals is shifted in time with the lag proportional to the distance between sensors and the speed of move. It means that the difference signal looks like derivative of the total signal at move in the non-uniform field. So, using quite simple

  9. Improved photo response non-uniformity (PRNU) based source camera identification.

    PubMed

    Cooper, Alan J

    2013-03-10

    The concept of using Photo Response Non-Uniformity (PRNU) as a reliable forensic tool to match an image to a source camera is now well established. Traditionally, the PRNU estimation methodologies have centred on a wavelet based de-noising approach. Resultant filtering artefacts in combination with image and JPEG contamination act to reduce the quality of PRNU estimation. In this paper, it is argued that the application calls for a simplified filtering strategy which at its base level may be realised using a combination of adaptive and median filtering applied in the spatial domain. The proposed filtering method is interlinked with a further two stage enhancement strategy where only pixels in the image having high probabilities of significant PRNU bias are retained. This methodology significantly improves the discrimination between matching and non-matching image data sets over that of the common wavelet filtering approach. PMID:23312587

  10. Non-uniform spatial response of the LCoS spatial light modulator

    NASA Astrophysics Data System (ADS)

    Lopez, Víctor; González-Vega, Arturo; Aguilar, Alberto; Landgrave, J. E. A.; García-Márquez, Jorge

    2016-05-01

    Liquid crystal on silicon (LCoS) spatial light modulators have been considered for a wide variety of scientific applications, due to their phase modulation capability and high spatial resolution. Nevertheless, their intrinsic characteristics, like the extensively studied depolarization and phase shift fluctuations, can make their behavior significantly distant from the ideal and somewhat unpredictable. Here, we present the characterization of a different source of uncertainty: the non-uniform spatial response of the LCoS, which is fundamentally different to the static aberrations of the panel. We measured local deviations of ±22% from the expected phase shift, resulting in non-negligible effects for phase modulation measurements, phase shifting interferometry, wavefront correction, and speckle interferometry.

  11. Non-Uniform Sampling and J-UNIO Automation for Efficient Protein NMR Structure Determination.

    PubMed

    Didenko, Tatiana; Proudfoot, Andrew; Dutta, Samit Kumar; Serrano, Pedro; Wüthrich, Kurt

    2015-08-24

    High-resolution structure determination of small proteins in solution is one of the big assets of NMR spectroscopy in structural biology. Improvements in the efficiency of NMR structure determination by advances in NMR experiments and automation of data handling therefore attracts continued interest. Here, non-uniform sampling (NUS) of 3D heteronuclear-resolved [(1)H,(1)H]-NOESY data yielded two- to three-fold savings of instrument time for structure determinations of soluble proteins. With the 152-residue protein NP_372339.1 from Staphylococcus aureus and the 71-residue protein NP_346341.1 from Streptococcus pneumonia we show that high-quality structures can be obtained with NUS NMR data, which are equally well amenable to robust automated analysis as the corresponding uniformly sampled data. PMID:26227870

  12. Discharge Characteristics of SF6 in a Non-Uniform Electric Field Under Repetitive Nanosecond Pulses

    NASA Astrophysics Data System (ADS)

    Ran, Huijuan; Wang, Lei; Wang, Jue; Wang, Tao; Yan, Ping

    2014-05-01

    The characteristics of high pressure sulphur hexafluoride (SF6) discharges in a highly non-uniform electric field under repetitive nanosecond pulses are investigated in this paper. The influencing factors on discharge process, such as gas pressure, pulse repetition frequency (PRF), and number of applied pulses, are analyzed. Experimental results show that the corona intensity weakens with the increase of gas pressure and strengthens with the increase of PRF or number of applied pulses. Spark discharge images suggest that a shorter and thicker discharge plasma channel will lead to a larger discharge current. The number of applied pulses to breakdown descends with the increase of PRF and ascends with the rise of gas pressure. The reduced electric field (E/p) decreases with the increase of PRF in all circumstances. The experimental results provide significant supplements to the dielectric characteristics of strongly electronegative gases under repetitive nanosecond pulses.

  13. The algorithm analysis on non-uniformity correction based on LMS adaptive filtering

    NASA Astrophysics Data System (ADS)

    Zhan, Dongjun; Wang, Qun; Wang, Chensheng; Chen, Huawang

    2010-11-01

    The traditional least mean square (LMS) algorithm has the performance of good adaptivity to noise, but there are several disadvantages in the traditional LMS algorithm, such as the defect in desired value of pending pixels, undetermined original coefficients, which result in slow convergence speed and long convergence period. Method to solve the desired value of pending pixel has improved based on these problems, also, the correction gain and offset coefficients worked out by the method of two-point temperature non-uniformity correction (NUC) as the original coefficients, which has improved the convergence speed. The simulation with real infrared images has proved that the new LMS algorithm has the advantages of better correction effect. Finally, the algorithm is implemented on the hardware structure of FPGA+DSP.

  14. Spike phase synchronization in delayed-coupled neural networks: Uniform vs. non-uniform transmission delay

    NASA Astrophysics Data System (ADS)

    Jalili, Mahdi

    2013-03-01

    In this paper, we investigated phase synchronization in delayed dynamical networks. Non-identical spiking Hindmarsh-Rose neurons were considered as individual dynamical systems and coupled through a number of network structures such as scale-free, Erdős-Rényi, and modular. The individual neurons were coupled through excitatory chemical synapses with uniform or distributed time delays. The profile of spike phase synchrony was different when the delay was uniform across the edges as compared to the case when it was distributed, i.e., different delays for the edges. When an identical transmission delay was considered, a quasi-periodic pattern was observed in the spike phase synchrony. There were specific values of delay where the phase synchronization reached to its peaks. The behavior of the phase synchronization in the networks with non-uniform delays was different with the former case, where the phase synchrony decreased as distributed delays introduced to the networks.

  15. The effects of non-uniform loss on time reversal mirrors

    NASA Astrophysics Data System (ADS)

    Taddese, Biniyam Tesfaye; Antonsen, Thomas M.; Ott, Edward; Anlage, Steven M.

    2014-08-01

    Time reversal mirrors work perfectly only for lossless wave propagation; dissipation destroys time-reversal invariance and limits the performance of time-reversal mirrors. Here, a new measure of time-reversal mirror performance is introduced and the adverse effect of dissipation on this performance measure is investigated. The technique of exponential amplification is employed to partially overcome the effect of non-uniform loss distributions, and its success is tested quantitatively using the new performance measure. A numerical model of a star graph is employed to test the applicability of this technique on realizations with various random spatial distributions of loss. A subset of the numerical results are also verified by experimental results from an electromagnetic time-reversal mirror. The exponential amplification technique is a simple way to improve the performance of emerging technologies based on time-reversed wave propagation such as directed communication and wireless power transfer.

  16. THE NON-UNIFORM, DYNAMIC ATMOSPHERE OF BETELGEUSE OBSERVED AT MID-INFRARED WAVELENGTHS

    SciTech Connect

    Ravi, V.; Wishnow, E. H.; Townes, C. H.; Lockwood, S.; Mistry, H.; Tatebe, K.

    2011-10-10

    We present an interferometric study of the continuum surface of the red supergiant star Betelgeuse at 11.15 {mu}m wavelength, using data obtained with the Berkeley Infrared Spatial Interferometer each year between 2006 and 2010. These data allow an investigation of an optically thick layer within 1.4 stellar radii of the photosphere. The layer has an optical depth of {approx}1 at 11.15 {mu}m, and varies in temperature between 1900 K and 2800 K and in outer radius between 1.16 and 1.36 stellar radii. Electron-hydrogen-atom collisions contribute significantly to the opacity of the layer. The layer has a non-uniform intensity distribution that changes between observing epochs. These results indicate that large-scale surface convective activity strongly influences the dynamics of the inner atmosphere of Betelgeuse and mass-loss processes.

  17. Non-uniform black strings and the critical dimension in the 1/D expansion

    NASA Astrophysics Data System (ADS)

    Suzuki, Ryotaku; Tanabe, Kentaro

    2015-10-01

    Non-uniform black strings (NUBS) are studied by the large D effective theory approach. By solving the near-horizon geometry in the 1 /D expansion, we obtain the effective equation for the deformed horizon up to the next-to-next-to-leading order (NNLO) in 1 /D. We also solve the far-zone geometry by the Newtonian approximation. Matching the near and far zones, the thermodynamic variables are computed in the 1 /D expansion. As the result, the large D analysis gives a critical dimension D * ≃ 13 .5 at which the translation-symmetry-breaking phase transition changes between first and second order. This value of D * agrees perfectly, within the precision of the 1 /D expansion, with the result previously obtained by E. Sorkin through the numerical resolution. We also compare our NNLO results for the thermodynamics of NUBS to earlier numerical calculations, and find good agreement within the expected precision.

  18. Exact actuator disk solutions for non-uniform heavy loading and slipstream contraction

    NASA Astrophysics Data System (ADS)

    Conway, John T.

    1998-06-01

    A semi-analytical method has been developed to solve for the inviscid incompressible flow induced by a heavily loaded actuator disk with non-uniform loading. The solution takes the contraction of the slipstream fully into account. The method is an extension of the analytical theory of Conway (1995) for the linearized actuator disk and is exact for an incompressible perfect fluid. The solutions for the velocities and stream function are given as one-dimensional integrals of expressions containing complete elliptic integrals. Any load distribution with bounded radial gradient can be treated. Results are presented here for both contra-rotating and normal propellers. For the special case of a contra-rotating propeller with a parabolic velocity profile in the ultimate wake, the vorticity in the slipstream is shown to be the same as in the analytically tractable spherical vortex of Hill (1894) and the related family of steady vortices explored by Fraenkel (1970, 1972) and Norbury (1973).

  19. Motion of non-uniform double current-vortex sheets in magnetohydrodynamic flows

    NASA Astrophysics Data System (ADS)

    Matsuoka, Chihiro

    2016-03-01

    A nonlinear motion of vortex sheets with a non-uniform current is investigated using the vortex blob method. The fluid interface forms a double layered current-vortex sheet due to the boundary condition possessing the induction equation. We can prove that the current only flows on the interface and that does not appear in the bulk when we apply the initial magnetic field to be parallel to the interface. We show that the current induced on a vortex sheet leads to a strong amplification of the magnetic field, taking the motion of vortex sheets in magnetohydrodynamic Richtmyer-Meshkov instability as an example. When the initial Lorentz force term is large, an oscillation due to the Alfvén wave appears and the nonlinear growth is suppressed.

  20. Probing Invisible, Excited Protein States by Non-Uniformly Sampled Pseudo-4D CEST Spectroscopy.

    PubMed

    Long, Dong; Delaglio, Frank; Sekhar, Ashok; Kay, Lewis E

    2015-09-01

    Chemical exchange saturation transfer (CEST) NMR spectroscopy is a powerful tool for studies of slow timescale protein dynamics. Typical experiments are based on recording a large number of 2D data sets and quantifying peak intensities in each of the resulting planes. A weakness of the method is that peaks must be resolved in 2D spectra, limiting applications to relatively small proteins. Resolution is significantly improved in 3D spectra but recording uniformly sampled data is time-prohibitive. Here we describe non-uniformly sampled HNCO-based pseudo-4D CEST that provides excellent resolution in reasonable measurement times. Data analysis is done through fitting in the time domain, without the need of reconstructing the frequency dimensions, exploiting previously measured accurate peak positions in reference spectra. The methodology is demonstrated on several protein systems, including a nascent form of superoxide dismutase that is implicated in neurodegenerative disease. PMID:26178142

  1. A new alternating bi-diagonal compact scheme for non-uniform grids

    NASA Astrophysics Data System (ADS)

    Sengupta, Tapan K.; Sengupta, Aditi

    2016-04-01

    A new compact scheme has been developed for any non-uniform grid. The compact scheme has been developed for spatial discretization and is analyzed here in conjunction with four-stage, fourth order Runge-Kutta (RK4) scheme for time integration while solving the one-dimensional convection equation. The space-time discretization combination is calibrated by subjecting the system to global spectral analysis (GSA) which was developed by the authors' group. Here, the compact scheme has been obtained by using a combination of two bi-diagonal schemes. The novel aspect of this scheme is its application in the physical plane directly without the necessity of mapping or transformations. Some typical cases for problems in acoustics, as well as fluid mechanics, have been studied here and potential use in large eddy simulations (LES) has been demonstrated by solving Navier-Stokes equation for lid driven cavity.

  2. Off-axis magneto-donor impurity in a non-uniform height quantum ribbon

    NASA Astrophysics Data System (ADS)

    Suaza, Y. A.; Fulla, M. R.; Posada-Rudas, J. G.; Marín, J. H.

    2015-11-01

    Single electron and off-axis neutral donor in non-uniform height quantum ribbon under threading external magnetic field is analyzed. The quantum ribbon height dependence with polar angle is modeled trough the two-parametric function. One of these parameters define the number of protuberances and the other one allows us to exert control on the structural deformation depth. By considering quantum ribbons with very small height-to-base aspect ratio, it was possible to obtain the energy structure through the adiabatic procedure. The corresponding angular dependent Schrödinger equation can be solved in the framework of the exact diagonalization method. The results of calculation show that the Aharanov-Bohm oscillation patterns are very sensitive against changes of the quantum ribbon structural parameters.

  3. Particle fracture simulation in non-uniform microstructures of metal-matrix composites

    SciTech Connect

    Ghosh, S.; Moorthy, S.

    1998-01-23

    This paper deals with the evolution of damage in microstructures of reinforced ductile-matrix composites, by particle cracking and splitting. A small deformation Voronoi Cell finite element model is developed, in which each element may consist of a matrix phase, an inclusion phase and a crack phase. Brittle inclusions may be of arbitrary shapes and sizes, and may be dispersed non-uniformly in the matrix. Damage initiation of inclusions is assumed to follow a maximum principal stress theory. Complete particle cracking or splitting is assumed at the onset of damage. The model is validated by a few comparison studies. Various geometric patterns are studied to test the effectiveness of the model, as well as to understand the effect of morphology on damage evolution. Actual microstructures from optical micrographs of Al-Si-Mg composite systems are analyzed and compared with experimentally observed results. Quantitative characterization and statistical analysis is conducted to correlate morphological parameters with mechanical response.

  4. Effect of Non-Uniform Inlet Temperature on Flow Stagnation in a Pumped Fluid Tube Radiator

    NASA Astrophysics Data System (ADS)

    Reavis, Gretchen

    2008-01-01

    The effect of a non-uniform inlet temperature on the panel fluid tube flow stagnation point is examined using a spacecraft radiator panel model with 20 fluid tubes constructed in Thermal Desktop®. Fluid temperature variations due to panel edge effect and localized hot and cold spots in the flow path were simulated by varying the fluid inlet temperature on one or more tubes. Results show that a large fluid inlet temperature difference between tubes can decrease the fluid system stability and increase the possibility of fluid stagnation with the coldest fluid tube initiating stagnation. Conversely, a small fluid inlet temperature difference between tubes can, in some cases, increase the fluid system stability and decrease the possibility of fluid stagnation. A uniform fluid inlet temperature provides for a near optimization of the stagnation point as compared to fluid temperature gradients across the panel.

  5. Detecting Non-Uniform Clusters in Large-Scale Interaction Graphs

    PubMed Central

    Levtov, Nissan; Amberkar, Sandeep; Kaderali, Lars; Volkovich, Zeev

    2014-01-01

    Abstract Graph clustering becomes difficult as the graph size and complexity increase. In particular, in interaction graphs, the clusters are small and the data on the underlying interaction are not only complex, but also noisy due to the lack of information and experimental errors. The graphs representing such data consist of (possibly overlapping) clusters of non-uniform size with some false positive and false negative links. In this article, we propose a new approach, assuming that clusters in the graphs of protein–protein interaction (PPI) networks resemble corrupted cliques. Therefore, the problem can be reduced to looking for clusters only among nodes of approximately similar degrees. This idea was implemented using a soft version of the Farthest-Point-First (FPF) clustering algorithm with the Jaccard distance function modified to perform on slightly overlapping clusters. The StripClust program developed by us was tested on a synthetic network and on the yeast PPI network. PMID:24050498

  6. Numerical Study of Wave Propagation in a Non-Uniform Flow

    NASA Technical Reports Server (NTRS)

    Povitsky, Alex; Bushnell, Dennis M. (Technical Monitor)

    2000-01-01

    The propagation of acoustic waves originating from cylindrical and spherical pulses, in a non-uniform mean flow, and in the presence of a reflecting wall is investigated by Hardin and Pope approach using compact approximation of spatial derivatives. The 2-D and 3-D stagnation flows and a flow around a cylinder are taken as prototypes of real world flows with strong gradients of mean pressure and velocity. The intensity and directivity of acoustic wave patterns appear to be quite different from the benchmark solutions obtained in a static environment for the same geometry. The physical reasons for amplification and weakening of sound are discussed in terms of dynamics of wave profile and redistribution of acoustic energy and its potential and kinetic components. For an acoustic wave in the flow around a cylinder, the observed mean acoustic pressure is approximately doubled (upstream pulse position) and halved (downstream pulse position) in comparison with the sound propagation in static ambient conditions.

  7. Novel cone lasing emission in a non-uniform one-dimensional photonic crystal

    NASA Astrophysics Data System (ADS)

    Li, Yi; Zhou, Wen-Yuan; Ying, Cui-Feng; Yang, Na; Chen, Shao-Jie; Ye, Qing; Tian, Jian-Guo

    2015-06-01

    Novel cone lasing emission is observed from a photonic crystal (PC) with graded layers, which is fabricated by two-beam holographic interference in dichromated gelatin. The cone lasing is composed of one lasing spot and one concentric lasing ring. The good agreement between the experimental results and a numerical simulation performed using the transfer matrix method demonstrates that this lasing ring is induced by the coupling between the band edge and minigap, which is represented as some oscillations near the band edge in the passband of the reflection spectrum. The cone lasing may be useful for multi-wavelength fluorescence detection since the dual-colour directional enhanced fluorescence can be achieved without the mutual interference of lasing modes. Moreover, this readily observable cone lasing provides a direct visualization of the dispersion relation of non-uniform PCs.

  8. Characterizing Non-Uniformity of Performance of Thin-Film Solar Cells

    NASA Technical Reports Server (NTRS)

    Clark, Eric B. (Technical Monitor); Lush, Gregory B.

    2003-01-01

    Thin-film Solar Cells are being actively studied for terrestrial and space applications because of their potential to provide low-cost, lightweight, and flexible electric power system. Currently, thin-film solar cell performance is limited partially by the nonuniformity of performance that they typically exhibit. This nonuniformity of performance necessitates more detailed characterization techniques than the well-known macroscopic measurements such as current-voltage and efficiency. This project seeks to explore methods of characterization that take into account the spatial nonuniformity of thin-film solar cells. In this presentation we show results of electroluminescence images, short-circuit maps, and Kelvin Probe maps. All these mapping characterization and analysis tools show that the non-uniformities can correlated with device performance and efficiency.

  9. Non-Uniform Plasma Discharges in Near Earth Space Environment and Ionosphere to Troposphere Responses

    NASA Astrophysics Data System (ADS)

    McCanney, J. M.

    2009-05-01

    Most earth weather and ionosphere-space environment coupling studies separate the problems into distinct groups. Heliosphere to solar wind - solar storm activity to ionospheric coupling - thermosphere and mid- altitude to the ionosphere and electrical effects such as elves and sprites and thunderstorms in another group - additionally mid and high latitude weather systems are many times separated also. The theoretical work here shows that not only are these areas coupled and related, but it also shows that without the constant electrical and resulting magnetic driving forces from space environments, earth would have little if no weather variability at all below the ionosphere. With only solar light energy as input, earth (and the other planets) would have little weather at all. The realization that extensive electrical activates occur in and above the troposphere, extending to the ionosphere and ultimately coupling to the magnetosphere have raised the theoretical and experimental questions regarding the sources of EMF which create the observed effects. The current work has identified 17 Local Electrical Batteries (LEBs), which provide the electrical EMF that can be linked to the observed effects the jet streams and lower atmospheric weather phenomenon. The path of the sources of EMF can be followed from the passing solar wind through "tunnels" that end in electrical currents that pass into the atmosphere via the ionosphere to storm cloud systems in the lower atmosphere. However the source of energy comes from localized plasma discharging of a non-uniform plasma environment that powers the electrical systems of the entire solar system. These are ultimately the sources of electrical energy that power the severe lower atmospheric storm systems such as westerly moving hurricanes at low latitudes and associated tornadoes. The connection is made theoretically with the solar wind that drives the 17 identified LEBs. The ultimate source of driving energy is the result of an

  10. Retrospective non-uniform illumination correction techniques in images of tuberculosis.

    PubMed

    Priya, Ebenezer; Srinivasan, Subramanian; Ramakrishnan, Swaminathan

    2014-10-01

    Image pre-processing is highly significant in automated analysis of microscopy images. In this work, non-uniform illumination correction has been attempted using the surface fitting method (SFM), multiple regression method (MRM), and bidirectional empirical mode decomposition (BEMD) in digital microscopy images of tuberculosis (TB). The sputum smear positive and negative images recorded under a standard image acquisition protocol were subjected to illumination correction techniques and evaluated by error and statistical measures. Results show that SFM performs more efficiently than MRM or BEMD. The SFM produced sharp images of TB bacilli with better contrast. To further validate the results, multifractal analysis was performed that showed distinct variation before and after implementation of illumination correction by SFM. Results demonstrate that after illumination correction, there is a 26% increase in the number of bacilli, which aids in classification of the TB images into positive and negative, as TB positivity depends on the count of bacilli. PMID:25115957

  11. Non-uniform multivariate embedding to assess the information transfer in cardiovascular and cardiorespiratory variability series.

    PubMed

    Faes, Luca; Nollo, Giandomenico; Porta, Alberto

    2012-03-01

    The complexity of the short-term cardiovascular control prompts for the introduction of multivariate (MV) nonlinear time series analysis methods to assess directional interactions reflecting the underlying regulatory mechanisms. This study introduces a new approach for the detection of nonlinear Granger causality in MV time series, based on embedding the series by a sequential, non-uniform procedure, and on estimating the information flow from one series to another by means of the corrected conditional entropy. The approach is validated on short realizations of linear stochastic and nonlinear deterministic processes, and then evaluated on heart period, systolic arterial pressure and respiration variability series measured from healthy humans in the resting supine position and in the upright position after head-up tilt. PMID:21419400

  12. Online blind calibration of non-uniform photodetectors: application to endomicroscopy.

    PubMed

    Savoire, Nicolas; André, Barbara; Vercauteren, Tom

    2012-01-01

    We present an original method for the online blind calibration of non-uniform photodetectors. The disparity of the detectors may arise from both irregular spatial arrangement and distinct slowly time-varying photometric transfer functions. As natural images are mostly continuous, the signal collected by neighboring detectors is strongly correlated over time. The core idea of our method is to translate the calibration problem into relative pairwise calibrations between neighboring detectors followed by the regularized inversion of a system akin to gradient-based surface recovery. From our blind calibration procedure, we design an online blind calibration pipeline compatible with clinical practice. Online blind calibration is proved to be statistically better than standard offline calibration for reconstructing endomicroscopy sequences. PMID:23286185

  13. Synchronization in a non-uniform network of excitatory spiking neurons

    NASA Astrophysics Data System (ADS)

    Echeveste, Rodrigo; Gros, Claudius

    Spontaneous synchronization of pulse coupled elements is ubiquitous in nature and seems to be of vital importance for life. Networks of pacemaker cells in the heart, extended populations of southeast asian fireflies, and neuronal oscillations in cortical networks, are examples of this. In the present work, a rich repertoire of dynamical states with different degrees of synchronization are found in a network of excitatory-only spiking neurons connected in a non-uniform fashion. In particular, uncorrelated and partially correlated states are found without the need for inhibitory neurons or external currents. The phase transitions between these states, as well the robustness, stability, and response of the network to external stimulus are studied.

  14. Sampling-interval-dependent stability for linear sampled-data systems with non-uniform sampling

    NASA Astrophysics Data System (ADS)

    Shao, Hanyong; Lam, James; Feng, Zhiguang

    2016-09-01

    This paper is concerned with the sampling-interval-dependent stability of linear sampled-data systems with non-uniform sampling. A new Lyapunov-like functional is constructed to derive sampling-interval-dependent stability results. The Lyapunov-like functional has three features. First, it depends on time explicitly. Second, it may be discontinuous at the sampling instants. Third, it is not required to be positive definite between sampling instants. Moreover, the new Lyapunov-like functional can make use of the information fully of the sampled-data system, including that of both ends of the sampling interval. By making a new proposition for the Lyapunov-like functional, a sampling-interval-dependent stability criterion with reduced conservatism is derived. The new sampling-interval-dependent stability criterion is further extended to linear sampled-data systems with polytopic uncertainties. Finally, examples are given to illustrate the reduced conservatism of the stability criteria.

  15. Implementation of non-uniform FFT based Ewald summation in dissipative particle dynamics method

    NASA Astrophysics Data System (ADS)

    Wang, Yong-Lei; Laaksonen, Aatto; Lu, Zhong-Yuan

    2013-02-01

    The ENUF method, i.e., Ewald summation based on the non-uniform FFT technique (NFFT), is implemented in dissipative particle dynamics (DPD) simulation scheme to fast and accurately calculate the electrostatic interactions at mesoscopic level. In a simple model electrolyte system, the suitable ENUF-DPD parameters, including the convergence parameter α, the NFFT approximation parameter p, and the cut-offs for real and reciprocal space contributions, are carefully determined. With these optimized parameters, the ENUF-DPD method shows excellent efficiency and scales as O(NlogN). The ENUF-DPD method is further validated by investigating the effects of charge fraction of polyelectrolyte, ionic strength and counterion valency of added salts on polyelectrolyte conformations. The simulations in this paper, together with a separately published work of dendrimer-membrane complexes, show that the ENUF-DPD method is very robust and can be used to study charged complex systems at mesoscopic level.

  16. Non-uniform dispersion of the source-sink relationship alters wavefront curvature.

    PubMed

    Romero, Lucia; Trenor, Beatriz; Ferrero, Jose M; Starmer, C Frank

    2013-01-01

    The distribution of cellular source-sink relationships plays an important role in cardiac propagation. It can lead to conduction slowing and block as well as wave fractionation. It is of great interest to unravel the mechanisms underlying evolution in wavefront geometry. Our goal is to investigate the role of the source-sink relationship on wavefront geometry using computer simulations. We analyzed the role of variability in the microscopic source-sink relationship in driving changes in wavefront geometry. The electrophysiological activity of a homogeneous isotropic tissue was simulated using the ten Tusscher and Panfilov 2006 action potential model and the source-sink relationship was characterized using an improved version of the Romero et al. safety factor formulation (SFm2). Our simulations reveal that non-uniform dispersion of the cellular source-sink relationship (dispersion along the wavefront) leads to alterations in curvature. To better understand the role of the source-sink relationship in the process of wave formation, the electrophysiological activity at the initiation of excitation waves in a 1D strand was examined and the source-sink relationship was characterized using the two recently updated safety factor formulations: the SFm2 and the Boyle-Vigmond (SFVB) definitions. The electrophysiological activity at the initiation of excitation waves was intimately related to the SFm2 profiles, while the SFVB led to several counterintuitive observations. Importantly, with the SFm2 characterization, a critical source-sink relationship for initiation of excitation waves was identified, which was independent of the size of the electrode of excitation, membrane excitability, or tissue conductivity. In conclusion, our work suggests that non-uniform dispersion of the source-sink relationship alters wavefront curvature and a critical source-sink relationship profile separates wave expansion from collapse. Our study reinforces the idea that the safety factor

  17. Improvement of brain segmentation accuracy by optimizing non-uniformity correction using N3.

    PubMed

    Zheng, Weili; Chee, Michael W L; Zagorodnov, Vitali

    2009-10-15

    Smoothly varying and multiplicative intensity variations within MR images that are artifactual, can reduce the accuracy of automated brain segmentation. Fortunately, these can be corrected. Among existing correction approaches, the nonparametric non-uniformity intensity normalization method N3 (Sled, J.G., Zijdenbos, A.P., Evans, A.C., 1998. Nonparametric method for automatic correction of intensity nonuniformity in MRI data. IEEE Trans. Med. Imag. 17, 87-97.) is one of the most frequently used. However, at least one recent study (Boyes, R.G., Gunter, J.L., Frost, C., Janke, A.L., Yeatman, T., Hill, D.L.G., Bernstein, M.A., Thompson, P.M., Weiner, M.W., Schuff, N., Alexander, G.E., Killiany, R.J., DeCarli, C., Jack, C.R., Fox, N.C., 2008. Intensity non-uniformity correction using N3 on 3-T scanners with multichannel phased array coils. NeuroImage 39, 1752-1762.) suggests that its performance on 3 T scanners with multichannel phased-array receiver coils can be improved by optimizing a parameter that controls the smoothness of the estimated bias field. The present study not only confirms this finding, but additionally demonstrates the benefit of reducing the relevant parameter values to 30-50 mm (default value is 200 mm), on white matter surface estimation as well as the measurement of cortical and subcortical structures using FreeSurfer (Martinos Imaging Centre, Boston, MA). This finding can help enhance precision in studies where estimation of cerebral cortex thickness is critical for making inferences. PMID:19559796

  18. Relationship between local molecular field theory and density functional theory for non-uniform liquids.

    PubMed

    Archer, A J; Evans, R

    2013-01-01

    The local molecular field theory (LMF) developed by Weeks and co-workers has proved successful for treating the structure and thermodynamics of a variety of non-uniform liquids. By reformulating LMF in terms of one-body direct correlation functions we recast the theory in the framework of classical density functional theory (DFT). We show that the general LMF equation for the effective reference potential φ(R)(r) follows directly from the standard mean-field DFT treatment of attractive interatomic forces. Using an accurate (fundamental measures) DFT for the non-uniform hard-sphere reference fluid we determine φ(R)(r) for a hard-core Yukawa liquid adsorbed at a planar hard wall. In the approach to bulk liquid-gas coexistence we find the effective potentials exhibit rich structure that can include damped oscillations at large distances from the wall as well as the repulsive hump near the wall required to generate the low density "gas" layer characteristic of complete drying. We argue that it would be difficult to obtain the same level of detail from other (non-DFT based) implementations of LMF. LMF emphasizes the importance of making an intelligent division of the interatomic pair potential of the full system into a reference part and a remainder that can be treated in mean-field approximation. We investigate different divisions for an exactly solvable one-dimensional model where the pair potential has a hard-core plus a linear attractive tail. Results for the structure factor and the equation of state of the uniform fluid show that including a significant portion of the attraction in the reference system can be much more accurate than treating the full attractive tail in mean-field approximation. We discuss further aspects of the relationship between LMF and DFT. PMID:23298050

  19. Ambient noise tomography of a deep geothermal reservoir in non-uniform noise conditions

    NASA Astrophysics Data System (ADS)

    Lehujeur, Maximilien; Vergne, Jérôme; Schmittbuhl, Jean; Maggi, Alessia

    2016-04-01

    Passive imaging from the correlation of ambient seismic noise is of great interest for the exploration, the characterization and the monitoring of deep geothermal sites. It can probe the subsoil with no natural or induced seismic sources and at much lower costs than active methods. Here, we want to apply this method to the geothermal sites of Rittershoffen and Soultz-sous-forêts, Alsace, France. The data is provided by several seismological networks installed in the area over the last years and initially dedicated to the monitoring of the induced seismicity. The implementation of ambient noise tomography in such context have some specificities. We show that in this region, both the fundamental and the first overtone of the Rayleigh waves are present in the empirical Green functions and should be unambiguously identified. The period band is restricted to the range 1-7s due to the depth of the targeted structures (first 5 kilometers). This requires working with a noise dominated by the secondary micro-seismic peak whose spatial distribution is highly non-uniform in this region. Furthermore, the small aperture of the networks forces us to include station pairs whose distance is less than the 3 wavelengths rule, in order to maintain a proper lateral resolution of the tomographic images. The analysis of the noise correlation functions indicate that the non-uniform distribution of the noise sources and the short inter-station distances induce significant errors on the tomographic maps. To overcome this issue, we propose an inversion scheme based on the full correlation waveforms to estimate the group and phase speed dispersion maps together with the azimuthal distribution of the noise sources. The method is first applied to synthetic data showing that the procedure produces accurate velocity measurements. The method is then applied to real data to estimate the velocity structure around the two geothermal sites.

  20. Eye safety analysis for non-uniform retinal scanning laser trajectories

    NASA Astrophysics Data System (ADS)

    Schelinski, Uwe; Dallmann, Hans-Georg; Grüger, Heinrich; Knobbe, Jens; Pügner, Tino; Reinig, Peter; Woittennek, Franziska

    2016-03-01

    Scanning the retinae of the human eyes with a laser beam is an approved diagnosis method in ophthalmology; moreover the retinal blood vessels form a biometric modality for identifying persons. Medical applied Scanning Laser Ophthalmoscopes (SLOs) usually contain galvanometric mirror systems to move the laser spot with a defined speed across the retina. Hence, the load of laser radiation is uniformly distributed and eye safety requirements can be easily complied. Micro machined mirrors also known as Micro Electro Mechanical Systems (MEMS) are interesting alternatives for designing retina scanning systems. In particular double-resonant MEMS are well suited for mass fabrication at low cost. However, their Lissajous-shaped scanning figure requires a particular analysis and specific measures to meet the requirements for a Class 1 laser device, i.e. eye-safe operation. The scanning laser spot causes a non-uniform pulsing radiation load hitting the retinal elements within the field of view (FoV). The relevant laser safety standards define a smallest considerable element for eye-related impacts to be a point source that is visible with an angle of maximum 1.5 mrad. For non-uniform pulsing expositions onto retinal elements the standard requires to consider all particular impacts, i.e. single pulses, pulse sequences in certain time intervals and cumulated laser radiation loads. As it may be expected, a Lissajous scanning figure causes the most critical radiation loads at its edges and borders. Depending on the applied power the laser has to be switched off here to avoid any retinal injury.

  1. An analytical approach to quantitative reconstruction of non-uniform attenuated brain SPECT.

    PubMed

    Liang, Z; Ye, J; Harrington, D P

    1994-11-01

    An analytical approach to quantitative brain SPECT (single-photon-emission computed tomography) with non-uniform attenuation is developed. The approach formulates accurately the projection-transform equation as a summation of primary- and scatter-photon contributions. The scatter contribution can be estimated using the multiple-energy-window samples and removed from the primary-energy-window data by subtraction. The approach models the primary contribution as a convolution of the attenuated source and the detector-response kernel at a constant depth from the detector with the central-ray approximation. The attenuated Radon transform of the source can be efficiently deconvolved using the depth-frequency relation. The approach inverts exactly the attenuated Radon transform by Fourier transforms and series expansions. The performance of the analytical approach was studied for both uniform- and non-uniform-attenuation cases, and compared to the conventional FBP (filtered-backprojection) method by computer simulations. A patient brain X-ray image was acquired by a CT (computed-tomography) scanner and converted to the object-specific attenuation map for 140 keV energy. The mathematical Hoffman brain phantom was used to simulate the emission source and was resized such that it was completely surrounded by the skull of the CT attenuation map. The detector-response kernel was obtained from measurements of a point source at several depths in air from a parallel-hole collimator of a SPECT camera. The projection data were simulated from the object-specific attenuating source including the depth-dependent detector response. Quantitative improvement (>5%) in reconstructing the data was demonstrated with the nonuniform attenuation compensation, as compared to the uniform attenuation correction and the conventional FBP reconstruction. The commuting time was less than 5 min on an HP/730 desktop computer for an image array of 1282*32 from 128 projections of 128*32 size. PMID

  2. On the non-uniform distribution of the angular elements of near-Earth objects

    NASA Astrophysics Data System (ADS)

    JeongAhn, Youngmin; Malhotra, Renu

    2014-02-01

    We examine the angular distributions of near-Earth objects (NEOs) which are often regarded as uniform. The apparent distribution of the longitude of ascending node, Ω, is strongly affected by well-known seasonal effects in the discovery rate of NEOs. The deviation from the expected π-periodicity in the apparent distribution of Ω indicates that its intrinsic distribution is slightly enhanced along a mean direction, Ω‾=111°; approximately 53% of NEOs have Ω values within ±90° of Ω‾. We also find that each subgroup of NEOs (Amors, Apollos and Atens) has different observational selection effects which cause different non-uniformities in the apparent distributions of their arguments of perihelion ω, and longitudes of perihelion ϖ. For their intrinsic distributions, our analysis reveals that the Apollo asteroids have non-uniform ω due to secular dynamics associated with inclination-eccentricity-ω coupling, and the Amors’ ϖ distribution is peaked towards the secularly forced eccentricity vector. The Apollos’ ω distribution is axial, favoring values near 0° and 180°; the two quadrants centered at 0° and 180° account for 55% of the Apollos’ ω values. The Amors’ ϖ distribution peaks near ϖ‾=4°; 61% of Amors have ϖ within ±90° of this peak. We show that these modest but statistically significant deviations from uniform random distributions of angular elements are owed to planetary perturbations, primarily Jupiter’s. It is remarkable that this strongly chaotic population of minor planets reveals the presence of Jupiter in its angular distributions.

  3. Chronic intracortical microelectrode arrays induce non-uniform, depth-related tissue responses

    NASA Astrophysics Data System (ADS)

    Woolley, Andrew J.; Desai, Himanshi A.; Otto, Kevin J.

    2013-04-01

    Objective. Brain-implanted microelectrode arrays show promise as future clinical devices. However, biological responses to various designs, compositions and locations of these implants have not been fully characterized, and may impact the long-term functionality of these devices. In order to improve our understanding of the tissue conditions at the interface of chronic brain-implanted microdevices, we proposed utilizing advanced histology and microscopy techniques to image implanted devices and surrounding tissue intact within brain slices. We then proposed utilizing these methods to examine whether depth within the cerebral cortex affected tissue conditions around implants. Approach. Histological data was collected from rodent brain slices containing intact, intracortical microdevices four weeks after implantation surgery. Thick tissue sections containing the chronic implants were processed with fluorescent antibody labels, and imaged in an optical clearing solution using laser confocal microscopy. Main Results. Tissue surrounding microdevices exhibited two major depth-related phenomena: a non-uniform microglial coating along the device length and a dense mass of cells surrounding the implant in cerebral cortical layers I and II. Detailed views of the monocyte-derived immune cells improve our understanding of the close and complex association that immune cells have with chronic brain implants, and illuminated a possible relationship between cortical depth and the intensity of a chronic monocyte response around penetrating microdevices. The dense mass of cells contained vimentin, a protein not typically expressed highly in CNS cells, evidence that non-CNS cells likely descended down the face of the penetrating devices from the pial surface. Significance. Image data of highly non-uniform and depth-dependent biological responses along a device provides novel insight into the complexity of the tissue response to penetrating brain-implanted microdevices. The presented

  4. Control of Meridional Flow by a Non-Uniform Rotational Magnetic Field

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin; Ramachandran, Narayanan

    1999-01-01

    The diffusive mass transfer of species during crystal growth in vertical ampoules is significantly affected by fluid flow in the liquid mother phase (melt). For electrically conductive melts, an elegant way of remotely inducing and controlling this flow is by utilizing a uniform rotational magnetic field (RMF) in the transverse direction. It induces an azimuthal flow which tends to homogenize the thermal and solutal fields. The rotating field also reduces the diffusion boundary layer, stabilizes temperature fluctuations, and promotes better overall crystal growth. For moderate strengths of the applied magnetic field (2-20 m Tesla) with frequencies of up to 400 Hz, the induced secondary meridional flow becomes significant. It typically consists of one roll at the bottom of the liquid column and a second roll (vortex) at the top. The flow along the centerline (ampoule axis) is directed from the growing solid (interface) towards the liquid (melt). In case of convex interfaces (e.g. in floating zone crystal growth) such flow behavior is beneficial since it suppresses diffusion at the center. However, for concave interfaces (e.g. vertical Bridgman crystal growth) such a flow tends to exacerbate the situation in making the interface shape more concave. It would be beneficial to have some control of this meridional flow- for example, a single recirculating cell with controllable direction and flow magnitude will make this technique even more attractive for crystal growth. Such flow control is a possibility if a non-uniform PNE field is utilized for this purpose. Although this idea has been proposed earlier, it has not been conclusively demonstrated so far. In this work, we derive the governing equations for the fluid dynamics for such a system and obtain solutions for a few important cases. Results from parallel experimental measurements of fluid flow in a mercury column subjected to non-uniform RMF will also be presented.

  5. Determination of the responsivity non-uniformity of an infrared camera with regard to the measurement of radiance temperatures

    NASA Astrophysics Data System (ADS)

    Gutschwager, Berndt; Cárdenas-García, Daniel; Hollandt, Jörg

    2015-11-01

    This paper presents a method to accurately determine the responsivity non-uniformity of the pixels of an infrared camera. Mandatory for the use of infrared cameras for measurements of radiance temperatures with small uncertainties is the knowledge of this responsivity non-uniformity and the resulting ability to correct the responsivity non-uniformity of the measured image. Infrared cameras are optically and electronically more complex than radiation thermometers. For the calibration of infrared cameras a large-area source with a known radiance distribution is required. Practical implementations of such large-area sources are plate radiators, which generally have a non-homogeneous distribution of the radiance and of the radiance temperature over their surface. The determination of the non-uniformity of the radiance temperature of a plate radiator is mandatory for the accurate calibration of infrared cameras, i.e. for the determination and adequate consideration of the responsivity non-uniformity of all pixels of an infrared camera.

  6. Flow instabilities in non-uniformly heated helium jet arrays used for divertor PFCs

    SciTech Connect

    Youchison, Dennis L.

    2015-07-30

    In this study, due to a lack of prototypical experimental data, little is known about the off-normal behavior of recently proposed divertor jet cooling concepts. This article describes a computational fluid dynamics (CFD) study on two jet array designs to investigate their susceptibility to parallel flow instabilities induced by non-uniform heating and large increases in the helium outlet temperature. The study compared a single 25-jet helium-cooled modular divertor (HEMJ) thimble and a micro-jet array with 116 jets. Both have pure tungsten armor and a total mass flow rate of 10 g/s at a 600 °C inlet temperature. We investigated flow perturbations caused by a 30 MW/m2 off-normal heat flux applied over a 25 mm2 area in addition to the nominal 5 MW/m2 applied over a 75 mm2 portion of the face. The micro-jet array exhibited lower temperatures and a more uniform surface temperature distribution than the HEMJ thimble. We also investigated the response of a manifolded nine-finger HEMJ assembly using the nominal heat flux and a 274 mm2 heated area. For the 30 MW/m2 case, the micro-jet array absorbed 750 W in the helium with a maximum armor surface temperature of 1280 °C and a fluid/solid interface temperature of 801 °C. The HEMJ absorbed 750 W with a maximum armor surface temperature of 1411 °C and a fluid/solid interface temperature of 844 °C. For comparison, both the single HEMJ finger and the micro-jet array used 5-mm-thick tungsten armor. The ratio of maximum to average temperature and variations in the local heat transfer coefficient were lower for the micro-jet array compared to the HEMJ device. Although high heat flux testing is required to validate the results obtained in these simulations, the results provide important guidance in jet design and manifolding to increase heat removal while providing more even temperature distribution and minimizing non-uniformity in the gas flow and thermal stresses at the

  7. Flow instabilities in non-uniformly heated helium jet arrays used for divertor PFCs

    DOE PAGESBeta

    Youchison, Dennis L.

    2015-07-30

    In this study, due to a lack of prototypical experimental data, little is known about the off-normal behavior of recently proposed divertor jet cooling concepts. This article describes a computational fluid dynamics (CFD) study on two jet array designs to investigate their susceptibility to parallel flow instabilities induced by non-uniform heating and large increases in the helium outlet temperature. The study compared a single 25-jet helium-cooled modular divertor (HEMJ) thimble and a micro-jet array with 116 jets. Both have pure tungsten armor and a total mass flow rate of 10 g/s at a 600 °C inlet temperature. We investigated flowmore » perturbations caused by a 30 MW/m2 off-normal heat flux applied over a 25 mm2 area in addition to the nominal 5 MW/m2 applied over a 75 mm2 portion of the face. The micro-jet array exhibited lower temperatures and a more uniform surface temperature distribution than the HEMJ thimble. We also investigated the response of a manifolded nine-finger HEMJ assembly using the nominal heat flux and a 274 mm2 heated area. For the 30 MW/m2 case, the micro-jet array absorbed 750 W in the helium with a maximum armor surface temperature of 1280 °C and a fluid/solid interface temperature of 801 °C. The HEMJ absorbed 750 W with a maximum armor surface temperature of 1411 °C and a fluid/solid interface temperature of 844 °C. For comparison, both the single HEMJ finger and the micro-jet array used 5-mm-thick tungsten armor. The ratio of maximum to average temperature and variations in the local heat transfer coefficient were lower for the micro-jet array compared to the HEMJ device. Although high heat flux testing is required to validate the results obtained in these simulations, the results provide important guidance in jet design and manifolding to increase heat removal while providing more even temperature distribution and minimizing non-uniformity in the gas flow and thermal stresses at the armor joint.« less

  8. Scale effects on propeller cavitating hydrodynamic and hydroacoustic performances with non-uniform inflow

    NASA Astrophysics Data System (ADS)

    Yang, Qiongfang; Wang, Yongsheng; Zhang, Zhihong

    2013-03-01

    Considering the lack of theoretical models and ingredients necessary to explain the scaling of the results of propeller cavitation inception and cavitating hydroacoustics from model tests to full scale currently, and the insufficient reflection of the nuclei effects on cavitation in the numerical methods, the cavitating hydrodynamics and cavitation low frequency noise spectrum of three geometrically similar 7-bladed highly skewed propellers with non-uniform inflow are addressed. In this process, a numerical bridge from the multiphase viscous simulation of propeller cavitation hydrodynamics to its hydro-acoustics is built, and the scale effects on performances and the applicability of exist scaling law are analyzed. The effects of non-condensable gas(NCG) on cavitation inception are involved explicitly in the improved Sauer's cavitation model, and the cavity volume acceleration related to its characteristic length is used to produce the noise spectrum. Results show that, with the same cavitation number, the cavity extension on propeller blades increases with diameter associated with an earlier shift of the beginning point of thrust decline induced by cavitation, while the three decline slopes of thrust breakdown curves are found to be nearly the same. The power of the scaling law based on local Reynolds number around 0.9 R section is determined as 0.11. As for the smallest propeller, the predominant tonal noise is located at blade passing frequency(BPF), whereas 2BPF for the middle and both 2BPF and 3BPF for the largest, which shows the cavitating line spectrum is fully related to the interaction between non-uniform inflow and fluctuated cavity volume. The predicted spectrum level exceedance from the middle to the large propeller is 6.65 dB at BPF and 5.94 dB at 2BPF. Since it just differs less than 2 dB to the increment obtained by empirical scaling law, it is inferred that the scale effects on them are acceptable with a sufficient model scale, and so do the

  9. Compensation for z-directional non-uniformity of a monopole antenna at 7T MRI

    NASA Astrophysics Data System (ADS)

    Kim, Nambeom; Woo, Myung-Kyun; Kang, Chang-Ki

    2016-06-01

    The research was conducted to find ways to compensate for z-directional non-uniformity at a monopole antenna array (MA) coil by using a tilted optimized non-saturating excitation (TONE) pulse and to evaluate the feasibility of using the MA coil with the TONE pulse for anatomical and angiographic imaging. The sensitivity of a MA coil along the z-direction was measured by using an actual flip angle imaging pulse sequence with an oil phantom to evaluate the flip angle distributions of the MA coil for 7T magnetic resonance imaging (MRI). The effects on the z-directional uniformity were examined by using slow and fast TONE pulses, i.e., TONE SLOW and TONE FAST. T1- and T2* -weighted images of the human brain were also examined. The z-directional profiles of the TONE pulses were analyzed by using the average signal intensity throughout the brain. The effect of the TONE pulses on cerebral vessels was further examined by analyzing maximal intensity projections of T1-weighted images. With increasing the applied flip angles, the sensitivity slope slightly increased (0.044 per degree). For the MA coil, the TONE SLOWpulse yielded a compensated profile along the z-direction while the TONE HIGH pulse, which has a flat excitation profile along the z-direction, exhibited a tilted signal intensity toward the coil end, clearly indicating an intrinsic property of the MA coil. Similar to the phantom study, human brain images revealed z-directional symmetry around the peak value for the averaged signal intensity of the TONE SLOW pulse while the TONE HIGH pulse exhibited a tilted signal intensity toward the coil end. In vascular system imaging, the MA coil also clearly demonstrated a beneficial effect on the cerebral vessels, either with or without the TONE pulses. This study demonstrates that TONE pulses could compensate for the intrinsic z-directional non-uniformity of MA coils that exhibit strong uniformity in the x-y plane. Furthermore, tilted pulses, such as TONE pulses, were

  10. Models And Experiments Of Laminar Diffusion Flames In Non-Uniform Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Baker, J.; Varagani, R.; Saito, K.

    2003-01-01

    Non-uniform magnetic fields affect laminar diffusion flames as a result of the paramagnetic and diamagnetic properties of the products and reactants. Paramagnetism is the weak attraction to a magnetic field a material exhibits as a result of permanent magnetic dipole moments in the atoms of the material. Diamagnetism is the weak repulsion to a magnetic field exhibited by a material due to the lack of permanent magnetic dipole moments in the atoms of a material. The forces associated with paramagnetic and diamagnetism are several orders of magnitude less than the forces associated with the more familiar ferromagnetism. A typical example of a paramagnetic gas is oxygen while hydrocarbon fuels and products of combustion are almost always diamagnetic. The fact that magnets can affect flame behavior has been recognized for more than one hundred years. Early speculation was that such behavior was due to the magnetic interaction with the ionized gases associated with a flame. Using a scaling analysis, it was later shown that for laminar diffusion flames the magnetic field/ionized gas interaction was insignificant to the paramagnetic and diamagnetic influences. In this effort, the focus has been on examining laminar diffusion slot flames in the presence of non-uniform upward decreasing magnetic fields produced using permanent magnets. The principal reason for choosing slot flames was mathematical models of such flames show an explicit dependence on gravitational body forces, in the buoyancy-controlled regime, and an applied magnetic field would also impose a body force. In addition, the behavior of such flames was more easily visualized while maintaining the symmetry of the two-dimensional problem whereas it would have been impossible to obtain a symmetric magnetic field around a circular flame and still visually record the flame height and shape along the burner axis. The motivation for choosing permanent magnets to produce the magnetic fields was the assumption that

  11. Effect of the laser intensity profile on the shock non-uniformity in a directly driven spherical target

    NASA Astrophysics Data System (ADS)

    Temporal, Mauro; Canaud, Benoit; Garbett, Warren J.; Ramis, Rafael

    2015-10-01

    > An axially symmetric laser beam configuration irradiating a spherical capsule has been considered in the context of inertial confinement fusion (ICF). The laser beams are located at co-latitudes 49° and 131° and mimic the quad positions in the second cone of the Laser Mégajoule Facility. The capsule is directly irradiated by the laser beams whose energy deposition generates a nearly spherical shock wave. Two-dimensional hydrodynamic numerical simulations have been performed to analyse the non-uniformity of the shock wavefront launched inward throughout the target. Different laser intensity profiles, calculated by the illumination model, have been tested. The performance, in terms of shock non-uniformity, has been compared, and it is found that with an appropriate choice of the laser intensity profile it is possible to control the shock non-uniformity at early times.

  12. The ℓ-distribution method for modeling non-gray absorption in uniform and non-uniform gaseous media

    NASA Astrophysics Data System (ADS)

    André, Frédéric

    2016-08-01

    The ℓ-distribution modeling is proposed for radiative heat transfer in uniform and non-uniform non-gray gaseous media. The method is partly based on the application of results from the k-moment method. It combines this technique with several concepts from probability theory: the notion of rank transmutation maps allows extending the k-moment method to an infinite number of k-moments; copula models appear naturally to extend the method from uniform to non-uniform gas paths. The ℓ-distribution approach is shown to provide results: (1) more accurate - up to three orders of magnitude - than usual k-distribution approaches in uniform media, (2) as precise as correlated-k models in non-uniform situations. All these results are obtained at a computational cost lower than k-distribution models. Differences and similarities between k- and ℓ-distribution methods are discussed.

  13. Characterization of temperature non-uniformity over a premixed CH4-air flame based on line-of-sight TDLAS

    NASA Astrophysics Data System (ADS)

    Zhang, Guangle; Liu, Jianguo; Xu, Zhenyu; He, Yabai; Kan, Ruifeng

    2016-01-01

    A novel technique for characterizing temperature non-uniformity has been investigated based on measurements of line-of-sight tunable diode laser absorption spectroscopy. It utilized two fiber-coupled distributed feedback diode lasers at wavelengths around 1339 and 1392 nm as light sources to probe the field at multiple absorptions lines of water vapor and applied a temperature binning strategy combined with Gauss-Seidel iteration method to explore the temperature non-uniformity of the field in one dimension. The technique has been applied to a McKenna burner, which produced a flat premixed laminar CH4-air flame. The flame and its adjacent area formed an atmospheric field with significant non-uniformity of temperature and water vapor concentration. The effect of the number of temperature bins on column-density and temperature results has also been explored.

  14. Intensity non-uniformity correction using N3 on 3-T scanners with multichannel phased array coils.

    PubMed

    Boyes, Richard G; Gunter, Jeff L; Frost, Chris; Janke, Andrew L; Yeatman, Thomas; Hill, Derek L G; Bernstein, Matt A; Thompson, Paul M; Weiner, Michael W; Schuff, Norbert; Alexander, Gene E; Killiany, Ronald J; DeCarli, Charles; Jack, Clifford R; Fox, Nick C

    2008-02-15

    Measures of structural brain change based on longitudinal MR imaging are increasingly important but can be degraded by intensity non-uniformity. This non-uniformity can be more pronounced at higher field strengths, or when using multichannel receiver coils. We assessed the ability of the non-parametric non-uniform intensity normalization (N3) technique to correct non-uniformity in 72 volumetric brain MR scans from the preparatory phase of the Alzheimer's Disease Neuroimaging Initiative (ADNI). Normal elderly subjects (n=18) were scanned on different 3-T scanners with a multichannel phased array receiver coil at baseline, using magnetization prepared rapid gradient echo (MP-RAGE) and spoiled gradient echo (SPGR) pulse sequences, and again 2 weeks later. When applying N3, we used five brain masks of varying accuracy and four spline smoothing distances (d=50, 100, 150 and 200 mm) to ascertain which combination of parameters optimally reduces the non-uniformity. We used the normalized white matter intensity variance (standard deviation/mean) to ascertain quantitatively the correction for a single scan; we used the variance of the normalized difference image to assess quantitatively the consistency of the correction over time from registered scan pairs. Our results showed statistically significant (p<0.01) improvement in uniformity for individual scans and reduction in the normalized difference image variance when using masks that identified distinct brain tissue classes, and when using smaller spline smoothing distances (e.g., 50-100 mm) for both MP-RAGE and SPGR pulse sequences. These optimized settings may assist future large-scale studies where 3-T scanners and phased array receiver coils are used, such as ADNI, so that intensity non-uniformity does not influence the power of MR imaging to detect disease progression and the factors that influence it. PMID:18063391

  15. Intensity non-uniformity correction using N3 on 3-T scanners with multichannel phased array coils

    PubMed Central

    Boyes, Richard G.; Gunter, Jeff L.; Frost, Chris; Janke, Andrew L.; Yeatman, Thomas; Hill, Derek L.G.; Bernstein, Matt A.; Thompson, Paul M.; Weiner, Michael W.; Schuff, Norbert; Alexander, Gene E.; Killiany, Ronald J.; DeCarli, Charles; Jack, Clifford R.; Fox, Nick C.

    2008-01-01

    Measures of structural brain change based on longitudinal MR imaging are increasingly important but can be degraded by intensity non-uniformity. This non-uniformity can be more pronounced at higher field strengths, or when using multichannel receiver coils. We assessed the ability of the non-parametric non-uniform intensity normalization (N3) technique to correct non-uniformity in 72 volumetric brain MR scans from the preparatory phase of the Alzheimer’s Disease Neuroimaging Initiative (ADNI). Normal elderly subjects (n = 18) were scanned on different 3-T scanners with a multichannel phased array receiver coil at baseline, using magnetization prepared rapid gradient echo (MP-RAGE) and spoiled gradient echo (SPGR) pulse sequences, and again 2 weeks later. When applying N3, we used five brain masks of varying accuracy and four spline smoothing distances (d = 50, 100, 150 and 200 mm) to ascertain which combination of parameters optimally reduces the non-uniformity. We used the normalized white matter intensity variance (standard deviation/mean) to ascertain quantitatively the correction for a single scan; we used the variance of the normalized difference image to assess quantitatively the consistency of the correction over time from registered scan pairs. Our results showed statistically significant (p < 0.01) improvement in uniformity for individual scans and reduction in the normalized difference image variance when using masks that identified distinct brain tissue classes, and when using smaller spline smoothing distances (e.g., 50-100 mm) for both MP-RAGE and SPGR pulse sequences. These optimized settings may assist future large-scale studies where 3-T scanners and phased array receiver coils are used, such as ADNI, so that intensity non-uniformity does not influence the power of MR imaging to detect disease progression and the factors that influence it. PMID:18063391

  16. A Non-Uniformly Under-Sampled Blade Tip-Timing Signal Reconstruction Method for Blade Vibration Monitoring

    PubMed Central

    Hu, Zheng; Lin, Jun; Chen, Zhong-Sheng; Yang, Yong-Min; Li, Xue-Jun

    2015-01-01

    High-speed blades are often prone to fatigue due to severe blade vibrations. In particular, synchronous vibrations can cause irreversible damages to the blade. Blade tip-timing methods (BTT) have become a promising way to monitor blade vibrations. However, synchronous vibrations are unsuitably monitored by uniform BTT sampling. Therefore, non-equally mounted probes have been used, which will result in the non-uniformity of the sampling signal. Since under-sampling is an intrinsic drawback of BTT methods, how to analyze non-uniformly under-sampled BTT signals is a big challenge. In this paper, a novel reconstruction method for non-uniformly under-sampled BTT data is presented. The method is based on the periodically non-uniform sampling theorem. Firstly, a mathematical model of a non-uniform BTT sampling process is built. It can be treated as the sum of certain uniform sample streams. For each stream, an interpolating function is required to prevent aliasing in the reconstructed signal. Secondly, simultaneous equations of all interpolating functions in each sub-band are built and corresponding solutions are ultimately derived to remove unwanted replicas of the original signal caused by the sampling, which may overlay the original signal. In the end, numerical simulations and experiments are carried out to validate the feasibility of the proposed method. The results demonstrate the accuracy of the reconstructed signal depends on the sampling frequency, the blade vibration frequency, the blade vibration bandwidth, the probe static offset and the number of samples. In practice, both types of blade vibration signals can be particularly reconstructed by non-uniform BTT data acquired from only two probes. PMID:25621612

  17. Mechanisms of gas breakdown in non-uniform electric field between flat electrodes

    NASA Astrophysics Data System (ADS)

    Lisovskiy, Valeriy; Osmayev, Ruslan; Yegorenkov, Vladimir

    2015-09-01

    This paper studies how the electric field non-uniformity and the electron diffusion escape affect the DC gas breakdown between flat electrodes. We registered the breakdown curves of the DC discharge between the electrodes having the radius of Re = 6 mm with the inter-electrode gap values L between 3 and 72 mm in the tubes of inner diameter values of 13 and 56 mm within the nitrogen pressure range p from 0.02 to 120 Torr. We found that the breakdown curves for the gap of 3 mm actually match in the total pressure range, the diffusion escape of electrons to the tube walls playing no role in the gas breakdown process. In a narrow tube the minimum breakdown voltage is constant in the range of L/Re <= 1 but with the subsequent gap growth it increases linearly in order to compensate for the diffusion loss to the tube walls. For the wide tubes of 56 mm in diameter and for the gap of 72 mm the breakdown curves possess more flat minima and they run in the range of lower breakdown voltage values than one for a narrow tube. The minimum breakdown voltage grows slowly only in the range of L/Re >2. and Scientific Center of Physical Technologies, Svobody Sq.6, Kharkov, 61022, Ukraine.

  18. Non-uniform sampling: post-Fourier era of NMR data collection and processing.

    PubMed

    Kazimierczuk, Krzysztof; Orekhov, Vladislav

    2015-11-01

    The invention of multidimensional techniques in the 1970s revolutionized NMR, making it the general tool of structural analysis of molecules and materials. In the most straightforward approach, the signal sampling in the indirect dimensions of a multidimensional experiment is performed in the same manner as in the direct dimension, i.e. with a grid of equally spaced points. This results in lengthy experiments with a resolution often far from optimum. To circumvent this problem, numerous sparse-sampling techniques have been developed in the last three decades, including two traditionally distinct approaches: the radial sampling and non-uniform sampling. This mini review discusses the sparse signal sampling and reconstruction techniques from the point of view of an underdetermined linear algebra problem that arises when a full, equally spaced set of sampled points is replaced with sparse sampling. Additional assumptions that are introduced to solve the problem, as well as the shape of the undersampled Fourier transform operator (visualized as so-called point spread function), are shown to be the main differences between various sparse-sampling methods. PMID:26290057

  19. Adaptation of filtered back-projection to compton imaging with non-uniform azimuthal geometry

    NASA Astrophysics Data System (ADS)

    Lee, Hyounggun; Lee, Taewoong; Lee, Wonho

    2016-05-01

    For Compton image reconstruction, analytic reconstruction methods such as filtered backprojection have been used for real-time imaging. The conventional filtered back-projection method assumes a uniformly distributed azimuthal response in the detector system. In this study, we applied filtered back-projection to the experimental data from detector systems with limited azimuthal angle coverage ranges and estimated the limitations of the analytic reconstruction methods when applied to these systems. For the system with a uniform azimuthal response, the images reconstructed by using filtered back-projection showed better angular resolutions than the images obtained by using simple back-projection did. However, when filtered back-projection was applied to reconstruct Compton images based on measurements performed by using Compton cameras with limited response geometries, the reconstructed images exhibited artifacts caused by the geometrical limitations. Our proposed method employs the Compton camera's rotation to overcome the angular response limitations; when the rotation method was applied in this study, the artifacts in the reconstructed images caused by angular response limitations were minimized. With this method, filtered back-projection can be applied to reconstruct real-time Compton images even when the radiation measurements are performed by using Compton cameras with non-uniform azimuthal response geometries.

  20. Temperature model for process impact non-uniformity in genipin recovery by high pressure processing.

    PubMed

    Ramos-de-la-Peña, Ana Mayela; Montañez, Julio C; Reyes-Vega, María de la Luz; Contreras-Esquivel, Juan Carlos

    2015-11-15

    A model for the process impact temperature non-uniformity during high pressure processing (HPP) of genipap fruit purees was found during genipin recovery. Purees were subjected to HPP (130-530 MPa) under quasi-isobaric non-isothermal conditions (15 min; 0, 4.6 and 9.3mg pectinases/g fruit). Genipin and protein concentration was determined, and pH was measured. Polygalacturonase activity was quantified indirectly by protein content (mg/g fruit). First order kinetics described temperature changes (0-4 min). Polygalacturonase was activated at 130 MPa, inactivated reversibly at 330 MPa and activated again at 530 MPa. Enzyme reaction rate constant (k) was placed in the 0-4 min model and temperature from 2 to 15 min was described. Protein content and pH characterization in terms of decimal reduction time improved highly the 2-15 min model. Since temperature changes were modeled, more insight of its behavior in an HPP reactor was obtained, avoiding uniformity assumptions, making easier the industrial scale HPP implementation. PMID:25977049

  1. Regional paleofire regimes affected by non-uniform climate, vegetation and human drivers

    NASA Astrophysics Data System (ADS)

    Blarquez, Olivier; Ali, Adam A.; Girardin, Martin P.; Grondin, Pierre; Fréchette, Bianca; Bergeron, Yves; Hély, Christelle

    2015-09-01

    Climate, vegetation and humans act on biomass burning at different spatial and temporal scales. In this study, we used a dense network of sedimentary charcoal records from eastern Canada to reconstruct regional biomass burning history over the last 7000 years at the scale of four potential vegetation types: open coniferous forest/tundra, boreal coniferous forest, boreal mixedwood forest and temperate forest. The biomass burning trajectories were compared with regional climate trends reconstructed from general circulation models, tree biomass reconstructed from pollen series, and human population densities. We found that non-uniform climate, vegetation and human drivers acted on regional biomass burning history. In the open coniferous forest/tundra and dense coniferous forest, the regional biomass burning was primarily shaped by gradual establishment of less climate-conducive burning conditions over 5000 years. In the mixed boreal forest an increasing relative proportion of flammable conifers in landscapes since 2000 BP contributed to maintaining biomass burning constant despite climatic conditions less favourable to fires. In the temperate forest, biomass burning was uncoupled with climatic conditions and the main driver was seemingly vegetation until European colonization, i.e. 300 BP. Tree biomass and thus fuel accumulation modulated fire activity, an indication that biomass burning is fuel-dependent and notably upon long-term co-dominance shifts between conifers and broadleaf trees.

  2. Gramicidin Induce Local Non-Uniform Distribution of Lipids in Multi-Component Membrane Domains

    NASA Astrophysics Data System (ADS)

    Mao, Yu; Hussain, Fazle; Huang, Juyang

    2015-03-01

    In lipid membranes, gramicidin form trans-membrane channels that are specific for monovalent cations. We performed Molecular Dynamics simulations of gramicidin in coexisting liquid-ordered (Lo) and liquid disordered (Ld) domains using GROMACS. The lipid compositions of Lo and Ld domains are DOPC/DSPC/Cholesterol = 6.5/52.6/40.9 and 74.4/10.6/15, respectively. In the Ld domain, the membrane thickness matches the hydrophobic length of gramicidin quite well, and water molecules can diffuse through the gramicidin channels. However, in the Lo lipid domain, the bilayer thickness is far greater than the hydrophobic length of gramicidin and majority of gramicidin do not form conducting channel. The simulation result explained our experimental finding that gramicidin partition favorably into the Ld domains. The calculated radial distribution functions of lipids indicate that gramicidin recruit a layer of short DOPC surrounding each protein and keep cholesterol and taller DSPC away from the protein-bilayer interface. Our result indicates that membrane proteins are capable of inducing non-uniform distributions of lipids and creating a local bilayer environment, which favors protein function.

  3. Zombie Vortex Instability: Effects of Non-uniform Stratification & Thermal Cooling

    NASA Astrophysics Data System (ADS)

    Barranco, Joseph; Pei, Suyang; Marcus, Phil; Jiang, Chung-Hsiang

    2015-11-01

    The Zombie Vortex Instability (ZVI) is a nonlinear instability in rotating, stratified, shear flows, such as in protoplanetary disks (PPD) of gas and dust orbiting new stars. The instability mechanism is the excitation of baroclinic critical layers, leading to vorticity amplification and nonlinear evolution into anticyclonic vortices and cyclonic sheets. ZVI is most robust when the Coriolis frequency, shear rate, and Brunt-Väisälä (BV) frequency are of the same order. Previously, we investigated ZVI with uniform stratification and without thermal cooling. Here, we explore the role of non-uniform stratification as would be found in PPDs in which the BV frequency is zero in the disk midplane, and increases away from the midplane. We find that ZVI is vigorous 1-3 pressure scale heights away from the midplane, but the non-isotropic turbulence generated by ZVI can penetrate into the midplane. We also explore the effect of thermal cooling and find that ZVI is still robust for cooling times as short as 5 orbital periods. ZVI may play important roles in transporting angular momentum in PPDs, and in trapping dust grains, which may trigger gravitational clumping into planetesimals.

  4. Proposal for a Domain Wall Nano-Oscillator driven by Non-uniform Spin Currents

    PubMed Central

    Sharma, Sanchar; Muralidharan, Bhaskaran; Tulapurkar, Ashwin

    2015-01-01

    We propose a new mechanism and a related device concept for a robust, magnetic field tunable radio-frequency (rf) oscillator using the self oscillation of a magnetic domain wall subject to a uniform static magnetic field and a spatially non-uniform vertical dc spin current. The self oscillation of the domain wall is created as it translates periodically between two unstable positions, one being in the region where both the dc spin current and the magnetic field are present, and the other, being where only the magnetic field is present. The vertical dc spin current pushes it away from one unstable position while the magnetic field pushes it away from the other. We show that such oscillations are stable under noise and can exhibit a quality factor of over 1000. A domain wall under dynamic translation, not only being a source for rich physics, is also a promising candidate for advancements in nanoelectronics with the actively researched racetrack memory architecture, digital and analog switching paradigms as candidate examples. Devising a stable rf oscillator using a domain wall is hence another step towards the realization of an all domain wall logic scheme. PMID:26420544

  5. Non-uniform velocity profile mechanism for flame stabilization in a porous radiant burner

    SciTech Connect

    Catapan, R.C.; Costa, M.; Oliveira, A.A.M.

    2011-01-15

    Industrial processes where the heating of large surfaces is required lead to the possibility of using large surface porous radiant burners. This causes additional temperature uniformity problems, since it is increasingly difficult to evenly distribute the reactant mixture over a large burner surface while retaining its stability and keeping low pollutant emissions. In order to allow for larger surface area burners, a non-uniform velocity profile mechanism for flame stabilization in a porous radiant burner using a single large injection hole is proposed and analyzed for a double-layered burner operating in open and closed hot (laboratory-scale furnace, with temperature-controlled, isothermal walls) environments. In both environments, local mean temperatures within the porous medium have been measured. For lower reactant flow rate and ambient temperature the flame shape is conical and anchored at the rim of the injection hole. As the volumetric flow rate or furnace temperature is raised, the flame undergoes a transition to a plane flame stabilized near the external burner surface. However, the stability range envelope remains the same in both regimes. (author)

  6. Non-uniform Solar Temperature Field on Large Aperture, Fully-Steerable Telescope Structure

    NASA Astrophysics Data System (ADS)

    Liu, Yan

    2016-09-01

    In this study, a 110-m fully steerable radio telescope was used as an analysis platform and the integral parametric finite element model of the antenna structure was built in the ANSYS thermal analysis module. The boundary conditions of periodic air temperature, solar radiation, long-wave radiation shadows of the surrounding environment, etc. were computed at 30 min intervals under a cloudless sky on a summer day, i.e., worstcase climate conditions. The transient structural temperatures were then analyzed under a period of several days of sunshine with a rational initial structural temperature distribution until the whole set of structural temperatures converged to the results obtained the day before. The non-uniform temperature field distribution of the entire structure and the main reflector surface RMS were acquired according to changes in pitch and azimuth angle over the observation period. Variations in the solar cooker effect over time and spatial distributions in the secondary reflector were observed to elucidate the mechanism of the effect. The results presented here not only provide valuable realtime data for the design, construction, sensor arrangement and thermal deformation control of actuators but also provide a troubleshooting reference for existing actuators.

  7. Modeling and Compensating Temperature-Dependent Non-Uniformity Noise in IR Microbolometer Cameras.

    PubMed

    Wolf, Alejandro; Pezoa, Jorge E; Figueroa, Miguel

    2016-01-01

    Images rendered by uncooled microbolometer-based infrared (IR) cameras are severely degraded by the spatial non-uniformity (NU) noise. The NU noise imposes a fixed-pattern over the true images, and the intensity of the pattern changes with time due to the temperature instability of such cameras. In this paper, we present a novel model and a compensation algorithm for the spatial NU noise and its temperature-dependent variations. The model separates the NU noise into two components: a constant term, which corresponds to a set of NU parameters determining the spatial structure of the noise, and a dynamic term, which scales linearly with the fluctuations of the temperature surrounding the array of microbolometers. We use a black-body radiator and samples of the temperature surrounding the IR array to offline characterize both the constant and the temperature-dependent NU noise parameters. Next, the temperature-dependent variations are estimated online using both a spatially uniform Hammerstein-Wiener estimator and a pixelwise least mean squares (LMS) estimator. We compensate for the NU noise in IR images from two long-wave IR cameras. Results show an excellent NU correction performance and a root mean square error of less than 0.25 ∘ C, when the array's temperature varies by approximately 15 ∘ C. PMID:27447637

  8. Instability of Non-uniform Toroidal Magnetic Fields in Accretion Disks

    NASA Astrophysics Data System (ADS)

    Hirabayashi, Kota; Hoshino, Masahiro

    2016-05-01

    We present a new type of instability that is expected to drive magnetohydrodynamic (MHD) turbulence from a purely toroidal magnetic field in an accretion disk. It is already known that in a differentially rotating system, the uniform toroidal magnetic field is unstable due to magnetorotational instability (MRI) under a non-axisymmetric and vertical perturbation, while it is stable under a purely vertical perturbation. Contrary to the previous study, this paper proposes an unstable mode completely confined to the equatorial plane, driven by the expansive nature of the magnetic pressure gradient force under a non-uniform toroidal field. The basic nature of this growing eigenmode, which we name “magneto-gradient driven instability,” is studied using linear analysis, and the corresponding nonlinear evolution is then investigated using two-dimensional ideal MHD simulations. Although a single localized magnetic field channel alone cannot provide sufficient Maxwell stress to contribute significantly to the angular momentum transport, we find that the mode coupling between neighboring toroidal fields under multiple localized magnetic field channels drastically generates a highly turbulent state and leads to the enhanced transport of angular momentum, which is comparable to the efficiency seen in previous studies on MRIs. This horizontally confined mode may play an important role in the saturation of an MRI through complementray growth with the toroidal MRIs and coupling with magnetic reconnection.

  9. Modeling and Compensating Temperature-Dependent Non-Uniformity Noise in IR Microbolometer Cameras

    PubMed Central

    Wolf, Alejandro; Pezoa, Jorge E.; Figueroa, Miguel

    2016-01-01

    Images rendered by uncooled microbolometer-based infrared (IR) cameras are severely degraded by the spatial non-uniformity (NU) noise. The NU noise imposes a fixed-pattern over the true images, and the intensity of the pattern changes with time due to the temperature instability of such cameras. In this paper, we present a novel model and a compensation algorithm for the spatial NU noise and its temperature-dependent variations. The model separates the NU noise into two components: a constant term, which corresponds to a set of NU parameters determining the spatial structure of the noise, and a dynamic term, which scales linearly with the fluctuations of the temperature surrounding the array of microbolometers. We use a black-body radiator and samples of the temperature surrounding the IR array to offline characterize both the constant and the temperature-dependent NU noise parameters. Next, the temperature-dependent variations are estimated online using both a spatially uniform Hammerstein-Wiener estimator and a pixelwise least mean squares (LMS) estimator. We compensate for the NU noise in IR images from two long-wave IR cameras. Results show an excellent NU correction performance and a root mean square error of less than 0.25 ∘C, when the array’s temperature varies by approximately 15 ∘C. PMID:27447637

  10. Uniform and Non-uniform Perturbations in Brain-Machine Interface Task Elicit Similar Neural Strategies

    PubMed Central

    Armenta Salas, Michelle; Helms Tillery, Stephen I.

    2016-01-01

    The neural mechanisms that take place during learning and adaptation can be directly probed with brain-machine interfaces (BMIs). We developed a BMI controlled paradigm that enabled us to enforce learning by introducing perturbations which changed the relationship between neural activity and the BMI's output. We introduced a uniform perturbation to the system, through a visuomotor rotation (VMR), and a non-uniform perturbation, through a decorrelation task. The controller in the VMR was essentially unchanged, but produced an output rotated at 30° from the neurally specified output. The controller in the decorrelation trials decoupled the activity of neurons that were highly correlated in the BMI task by selectively forcing the preferred directions of these cell pairs to be orthogonal. We report that movement errors were larger in the decorrelation task, and subjects needed more trials to restore performance back to baseline. During learning, we measured decreasing trends in preferred direction changes and cross-correlation coefficients regardless of task type. Conversely, final adaptations in neural tunings were dependent on the type controller used (VMR or decorrelation). These results hint to the similar process the neural population might engage while adapting to new tasks, and how, through a global process, the neural system can arrive to individual solutions. PMID:27601981

  11. Proposal for a Domain Wall Nano-Oscillator driven by Non-uniform Spin Currents

    NASA Astrophysics Data System (ADS)

    Sharma, Sanchar; Muralidharan, Bhaskaran; Tulapurkar, Ashwin

    2015-09-01

    We propose a new mechanism and a related device concept for a robust, magnetic field tunable radio-frequency (rf) oscillator using the self oscillation of a magnetic domain wall subject to a uniform static magnetic field and a spatially non-uniform vertical dc spin current. The self oscillation of the domain wall is created as it translates periodically between two unstable positions, one being in the region where both the dc spin current and the magnetic field are present, and the other, being where only the magnetic field is present. The vertical dc spin current pushes it away from one unstable position while the magnetic field pushes it away from the other. We show that such oscillations are stable under noise and can exhibit a quality factor of over 1000. A domain wall under dynamic translation, not only being a source for rich physics, is also a promising candidate for advancements in nanoelectronics with the actively researched racetrack memory architecture, digital and analog switching paradigms as candidate examples. Devising a stable rf oscillator using a domain wall is hence another step towards the realization of an all domain wall logic scheme.

  12. The Propagation of Nonlinear Pressure Waves Through Regions of Non-Uniform Temperature

    NASA Astrophysics Data System (ADS)

    Dizinno, Nicholas; Vradis, George; Otugen, Volkan

    2006-11-01

    A numerical study of wave propagation through gases with non-uniform temperature distributions will be presented. The aim of this study is to determine the impact of temperature gradients on high-intensity pressure waves of various initial wave forms. Emphasis is paid to wave reflection and transmission. Ultimately, the performance of thermal barriers in attenuating nonlinear waves is evaluated. The concept of using regions of hot gas inside an ambient environment has potential in aeroacoustic applications, such as jet screech mitigation. This analysis considers the one-dimensional compressible unsteady Euler's equations with an ideal gas state equation. The domain is composed of two regions with uniform and equal gas properties separated by a third region with higher gas temperature (lower density). Pressure is uniform throughout the domain. We introduce various high-intensity wave forms into this medium. Our investigation studies how the shape and extent of the thermal zone affect transmission and reflection of the wave. This is done for a range of wave and thermal field parameters. A Fourier analysis will study the frequency content of the incident, transmitted and reflected waves. These results will help determine the effectiveness of using thermal barriers for nonlinear wave attenuation.

  13. Evaluation of rapid cell division in non-uniform cell cycles.

    PubMed

    Lee, Juyun; Jeon, Wonju; Chang, Man; Han, Myung-Soo

    2015-10-01

    To better understand the mechanisms of development of harmful algal blooms (HABs), accurate estimates of species-specific in situ growth rates are needed. HABs are caused by rapid cell division by the causative microorganisms. To accurately estimate the in situ growth rates of harmful algae having non-uniform and/or irregular cell cycles, we modified a standard equation based on the cell cycle, and calculated the in situ growth rate to describe the process of bloom development in nature. Sampling of a developing bloom of Heterosigma akashiwo in Pohang Bay, Korea, was conducted every 3 h from 15:00 on August 2 to 07:00 on August 4, 2006. The amount of H. akashiwo DNA was measured using flow cytometry following tyramide signal amplification-fluorescence in situ hybridization. On August 2, the percentage of G1 phase cells decreased from 15:00 to 19:00 then increased until 22:00; it then decreased until 07:00 on August 3, followed by an increase to 10:00. This indicates the ability of the cells in nature to undergo more than one round of division per day. During the following night two rounds of division did not occur. The in situ growth rates estimated using the modified equation ranged from 0.31 to 0.53 d(-1) . We conclude that the use of this equation enables more accurate estimates of bloom formation by rapidly dividing cells. PMID:26175341

  14. State Estimation for a Class of Non-Uniform Sampling Systems with Missing Measurements.

    PubMed

    Lin, Honglei; Sun, Shuli

    2016-01-01

    This paper is concerned with the state estimation problem for a class of non-uniform sampling systems with missing measurements where the state is updated uniformly and the measurements are sampled randomly. A new state model is developed to depict the dynamics at the measurement sampling points within a state update period. A non-augmented state estimator dependent on the missing rate is presented by applying an innovation analysis approach. It can provide the state estimates at the state update points and at the measurement sampling points within a state update period. Compared with the augmented method, the proposed algorithm can reduce the computational burden with the increase of the number of measurement samples within a state update period. It can deal with the optimal estimation problem for single and multi-sensor systems in a unified way. To improve the reliability, a distributed suboptimal fusion estimator at the state update points is also given for multi-sensor systems by using the covariance intersection fusion algorithm. The simulation research verifies the effectiveness of the proposed algorithms. PMID:27455282

  15. Chatter resistance of non-uniform turning bars with attached dynamic absorbers—Analytical approach

    NASA Astrophysics Data System (ADS)

    Saffury, J.; Altus, E.

    2010-05-01

    Forced harmonic vibration of a non-uniform elastic beam with attached dynamic vibration absorbers (DVA) is studied. Analytical approximation of the solution is obtained by the functional perturbation method (FPM). The problem has application to cutting tools operations where the resistance of the tool holder against regenerative chatter can be enhanced by optimizing the real part of the frequency response function (FRF). A test case of a beam with step-like heterogeneity and single DVA at the tip shows that the FPM solution is very accurate for up to ˜40 percent deviation in both stiffness and mass density. Using the analytical results and Sims approach, optimal DVA tuning is found for each set of beam heterogeneity parameters by solving a set of nonlinear algebraic equations numerically. It is found that the optimum can be further improved by searching for the best step location. The system optimization is then expanded to a general heterogeneous beam with a DVA at its tip. The mass and stiffness distribution is optimized by applying the Lagrange variation method on the FPM solution yielding Fredholm integral equations. The optimized morphology is found to be approximately linear and far from the "intuitive" step-like one (Rivin and Kang, 1992) and yields better chatter-resistance.

  16. Advances in iterative non-uniformity correction techniques for infrared scene projection

    NASA Astrophysics Data System (ADS)

    Danielson, Tom; Franks, Greg; LaVeigne, Joe; Prewarski, Marcus; Nehring, Brian

    2015-05-01

    Santa Barbara Infrared (SBIR) is continually developing improved methods for non-uniformity correction (NUC) of its Infrared Scene Projectors (IRSPs) as part of its comprehensive efforts to achieve the best possible projector performance. The most recent step forward, Advanced Iterative NUC (AI-NUC), improves upon previous NUC approaches in several ways. The key to NUC performance is achieving the most accurate possible input drive-to-radiance output mapping for each emitter pixel. This requires many highly-accurate radiance measurements of emitter output, as well as sophisticated manipulation of the resulting data set. AI-NUC expands the available radiance data set to include all measurements made of emitter output at any point. In addition, it allows the user to efficiently manage that data for use in the construction of a new NUC table that is generated from an improved fit of the emitter response curve. Not only does this improve the overall NUC by offering more statistics for interpolation than previous approaches, it also simplifies the removal of erroneous data from the set so that it does not propagate into the correction tables. AI-NUC is implemented by SBIR's IRWindows4 automated test software as part its advanced turnkey IRSP product (the Calibration Radiometry System or CRS), which incorporates all necessary measurement, calibration and NUC table generation capabilities. By employing AI-NUC on the CRS, SBIR has demonstrated the best uniformity results on resistive emitter arrays to date.

  17. Neural networks with non-uniform embedding and explicit validation phase to assess Granger causality.

    PubMed

    Montalto, Alessandro; Stramaglia, Sebastiano; Faes, Luca; Tessitore, Giovanni; Prevete, Roberto; Marinazzo, Daniele

    2015-11-01

    A challenging problem when studying a dynamical system is to find the interdependencies among its individual components. Several algorithms have been proposed to detect directed dynamical influences between time series. Two of the most used approaches are a model-free one (transfer entropy) and a model-based one (Granger causality). Several pitfalls are related to the presence or absence of assumptions in modeling the relevant features of the data. We tried to overcome those pitfalls using a neural network approach in which a model is built without any a priori assumptions. In this sense this method can be seen as a bridge between model-free and model-based approaches. The experiments performed will show that the method presented in this work can detect the correct dynamical information flows occurring in a system of time series. Additionally we adopt a non-uniform embedding framework according to which only the past states that actually help the prediction are entered into the model, improving the prediction and avoiding the risk of overfitting. This method also leads to a further improvement with respect to traditional Granger causality approaches when redundant variables (i.e. variables sharing the same information about the future of the system) are involved. Neural networks are also able to recognize dynamics in data sets completely different from the ones used during the training phase. PMID:26356599

  18. Effects of Non-Uniform Inlet Temperature Distribution on High-Pressure Turbine Blade Loading

    NASA Astrophysics Data System (ADS)

    Smith, Craig I.; Chang, Dongil; Tavoularis, Stavros

    2012-09-01

    The effects of a non-uniform inlet field on the performance of a commercial, transonic, single-stage, high-pressure, axial turbine with a curved inlet duct have been investigated numerically by solving the unsteady Reynolds-averaged Navier-Stokes equations with the shear stress transport (SST) turbulence model. By adjusting the alignment of the experimentally-based inlet temperature field with respect to the stator vanes, two clocking configurations were generated: a Vane-Impinging (VI) case, in which each hot streak impinged on a vane and a Mid-Pitch (MP) case, in which each hot streak passed between two vanes. An additional case with a purely radial (PR) variation of inlet temperature was also investigated. In the VI case, it was observed that, as the hot streaks impinged on the stator vanes, they spread spanwise due to the actions of the casing passage vortices and the radial pressure gradient; this resulted in a stream entering the rotor with relatively low temperature variations. In the MP case, the hot streaks were convected undisturbed past the relatively cool vane section. Relatively high time-averaged enthalpy values were found to occur on the pressure side of the blades in the MP configuration.

  19. Dynamics of dielectric barrier discharge in non-uniform gas composition investigated by laser spectroscopic measurements

    NASA Astrophysics Data System (ADS)

    Urabe, Keiichiro; Ito, Yosuke; Choi, Joon-Young; Sakai, Osamu; Tachibana, Kunihide

    2009-10-01

    It is well known that stable and glow dielectric barrier discharge (DBD) at atmospheric pressure is observed using helium gas and AC high voltage of kHz-order frequency. We have investigated the discharge mechanisms of DBDs from a view point of the spatiotemporal distributions of excited species measured by laser spectroscopic methods. In this presentation, we will show convincing arguments about the discharge model of the DBD especially having the non-uniformity of gas composition. As a DBD plasma source for atmospheric pressure processes, we have investigated an atmospheric pressure plasma jet (APPJ) using helium gas flow in ambient air, and this plasma source can be regarded as the DBD near the boundary interface of helium gas and ambient air. In this APPJ, we observed spatiotemporal distributions of excited species density inside the helium gas channel, using laser absorption spectroscopy and laser induced fluorescence, to measure the densities of helium metastable atom (2^3S1 state) and nitrogen ion (X^2σg^+ state) respectively. To study the influence of nitrogen gas contamination on the discharge profile of DBD, we have also applied CO2-laser heterodyne interferometry to measure the special distribution of electron density in parallel-plate DBD.

  20. Photoionization microscopy of Rydberg hydrogen atom in a non-uniform electrical field

    NASA Astrophysics Data System (ADS)

    Shao-Hao, Cheng; De-Hua, Wang; Zhao-Hang, Chen; Qiang, Chen

    2016-06-01

    In this paper, we investigate the photoionization microscopy of the Rydberg hydrogen atom in a gradient electric field for the first time. The observed oscillatory patterns in the photoionization microscopy are explained within the framework of the semiclassical theory, which can be considered as a manifestation of interference between various electron trajectories arriving at a given point on the detector plane. In contrast with the photoionization microscopy in the uniform electric field, the trajectories of the ionized electron in the gradient electric field will become chaotic. An infinite set of different electron trajectories can arrive at a given point on the detector plane, which makes the interference pattern of the electron probability density distribution extremely complicated. Our calculation results suggest that the oscillatory pattern in the electron probability density distribution depends sensitively on the electric field gradient, the scaled energy and the position of the detector plane. Through our research, we predict that the interference pattern in the electron probability density distribution can be observed in an actual photoionization microscopy experiment once the external electric field strength and the position of the electron detector plane are reasonable. This study provides some references for the future experimental research on the photoionization microscopy of the Rydberg atom in the non-uniform external fields. Project supported by the National Natural Science Foundation of China (Grant No. 11374133) and the Project of Shandong Provincial Higher Educational Science and Technology Program, China (Grant No. J13LJ04).

  1. Uniform and Non-uniform Perturbations in Brain-Machine Interface Task Elicit Similar Neural Strategies.

    PubMed

    Armenta Salas, Michelle; Helms Tillery, Stephen I

    2016-01-01

    The neural mechanisms that take place during learning and adaptation can be directly probed with brain-machine interfaces (BMIs). We developed a BMI controlled paradigm that enabled us to enforce learning by introducing perturbations which changed the relationship between neural activity and the BMI's output. We introduced a uniform perturbation to the system, through a visuomotor rotation (VMR), and a non-uniform perturbation, through a decorrelation task. The controller in the VMR was essentially unchanged, but produced an output rotated at 30° from the neurally specified output. The controller in the decorrelation trials decoupled the activity of neurons that were highly correlated in the BMI task by selectively forcing the preferred directions of these cell pairs to be orthogonal. We report that movement errors were larger in the decorrelation task, and subjects needed more trials to restore performance back to baseline. During learning, we measured decreasing trends in preferred direction changes and cross-correlation coefficients regardless of task type. Conversely, final adaptations in neural tunings were dependent on the type controller used (VMR or decorrelation). These results hint to the similar process the neural population might engage while adapting to new tasks, and how, through a global process, the neural system can arrive to individual solutions. PMID:27601981

  2. Vertical dynamic response of non-uniform motion of high-speed rails

    NASA Astrophysics Data System (ADS)

    Tran, Minh Thi; Ang, Kok Keng; Luong, Van Hai

    2014-10-01

    In this paper, a computational study using the moving element method (MEM) is carried out to investigate the dynamic response of a high-speed rail (HSR) traveling at non-uniform speeds. A new and exact formulation for calculating the generalized mass, damping and stiffness matrices of the moving element is proposed. Two wheel-rail contact models are examined. One is linear and the other nonlinear. A parametric study is carried out to understand the effects of various factors on the dynamic amplification factor (DAF) in contact force between the wheel and rail such as the amplitude of acceleration/deceleration of the train, the severity of railhead roughness and the wheel load. Resonance in the vibration response can possibly occur at various stages of the journey of the HSR when the speed of the train matches the resonance speed. As to be expected, the DAF in contact force peaks when resonance occurs. The effects of the severity of railhead roughness and the wheel load on the occurrence of the jumping wheel phenomenon, which occurs when there is a momentary loss of contact between the wheel and track, are investigated.

  3. Size Distribution Imaging by Non-Uniform Oscillating-Gradient Spin Echo (NOGSE) MRI.

    PubMed

    Shemesh, Noam; Álvarez, Gonzalo A; Frydman, Lucio

    2015-01-01

    Objects making up complex porous systems in Nature usually span a range of sizes. These size distributions play fundamental roles in defining the physicochemical, biophysical and physiological properties of a wide variety of systems - ranging from advanced catalytic materials to Central Nervous System diseases. Accurate and noninvasive measurements of size distributions in opaque, three-dimensional objects, have thus remained long-standing and important challenges. Herein we describe how a recently introduced diffusion-based magnetic resonance methodology, Non-Uniform-Oscillating-Gradient-Spin-Echo (NOGSE), can determine such distributions noninvasively. The method relies on its ability to probe confining lengths with a (length)6 parametric sensitivity, in a constant-time, constant-number-of-gradients fashion; combined, these attributes provide sufficient sensitivity for characterizing the underlying distributions in μm-scaled cellular systems. Theoretical derivations and simulations are presented to verify NOGSE's ability to faithfully reconstruct size distributions through suitable modeling of their distribution parameters. Experiments in yeast cell suspensions - where the ground truth can be determined from ancillary microscopy - corroborate these trends experimentally. Finally, by appending to the NOGSE protocol an imaging acquisition, novel MRI maps of cellular size distributions were collected from a mouse brain. The ensuing micro-architectural contrasts successfully delineated distinctive hallmark anatomical sub-structures, in both white matter and gray matter tissues, in a non-invasive manner. Such findings highlight NOGSE's potential for characterizing aberrations in cellular size distributions upon disease, or during normal processes such as development. PMID:26197220

  4. The Effect of Non-Uniform Wetting Properties on Contact Line Dynamics

    NASA Astrophysics Data System (ADS)

    Grivel, Morgane; Jeon, David; Gharib, Morteza

    2015-11-01

    Surfaces with non-uniform wetting properties have been shown to modify contact line dynamics and induce passive displacements of shallow flows. These surfaces are patterned with alternating hydrophobic and hydrophilic stripes of a certain width, spacing and orientation. A thin rectangular wall jet impinges on the surfaces and Fourier Transform Profilometry is used to reconstruct the 3D profile of the low to medium Reynolds number flows. Our previous work reported the development of intriguing roller structures at the contact line near hydrophobic-hydrophilic interfaces and the effect of varying the stripes' dimensions and orientation on these flows. Our present work extends the study to the effects of flow rate and plate inclination angle (with respect to the horizontal). The current work also studies air entrainment by the roller structures of the modified contact line. We will also discuss potential uses of this technique for modifying contact line dynamics and bow waves near surface-piercing bodies. Work is funded by the Office of Naval Research (grant N00014-11-1-0031) and the National Science Foundation's GRFP.

  5. The lateral line is necessary for blind cavefish rheotaxis in non-uniform flow.

    PubMed

    Kulpa, Matthew; Bak-Coleman, Joseph; Coombs, Sheryl

    2015-05-15

    When encountering a unidirectional flow, many fish exhibit an unconditioned orienting response known as rheotaxis. This multisensory behavior can reportedly involve visual, vestibular, tactile and lateral line cues. However, the precise circumstances under which different senses contribute are still unclear and there is considerable debate, in particular, about the contributions of the lateral line. In this study, we investigate the rheotactic behavior of blind cavefish under conditions of spatially non-uniform flow (a jet stream), which in theory, should promote reliance on lateral line cues. The behavior of individual lateral line enabled and disabled fish was videorecorded under IR light in a square arena that prevented streamwise biases and that contained a narrow jet stream in the center of the tank. Whereas the stream's peak velocity (8 cm s(-1)) declined very little in the streamwise direction, it declined steeply in the cross-stream direction (∼3-4.5 cm s(-1) cm(-1)). Lateral line enabled fish showed higher levels of orientation to the stream and its source (a 1-cm-wide nozzle) when in the central (jet stream) region of the tank compared with surrounding regions, whereas lateral line disabled fish showed random orientations in all regions of the tank. The results of this study indicate that the spatial characteristics of flow play a role in determining the sensory basis of rheotaxis. PMID:25827837

  6. Iterative Image Reconstruction for PROPELLER-MRI using the NonUniform Fast Fourier Transform

    PubMed Central

    Tamhane, Ashish A.; Anastasio, Mark A.; Gui, Minzhi; Arfanakis, Konstantinos

    2013-01-01

    Purpose To investigate an iterative image reconstruction algorithm using the non-uniform fast Fourier transform (NUFFT) for PROPELLER (Periodically Rotated Overlapping parallEL Lines with Enhanced Reconstruction) MRI. Materials and Methods Numerical simulations, as well as experiments on a phantom and a healthy human subject were used to evaluate the performance of the iterative image reconstruction algorithm for PROPELLER, and compare it to that of conventional gridding. The trade-off between spatial resolution, signal to noise ratio, and image artifacts, was investigated for different values of the regularization parameter. The performance of the iterative image reconstruction algorithm in the presence of motion was also evaluated. Results It was demonstrated that, for a certain range of values of the regularization parameter, iterative reconstruction produced images with significantly increased SNR, reduced artifacts, for similar spatial resolution, compared to gridding. Furthermore, the ability to reduce the effects of motion in PROPELLER-MRI was maintained when using the iterative reconstruction approach. Conclusion An iterative image reconstruction technique based on the NUFFT was investigated for PROPELLER MRI. For a certain range of values of the regularization parameter the new reconstruction technique may provide PROPELLER images with improved image quality compared to conventional gridding. PMID:20578028

  7. 3D-printed phantom for the characterization of non-uniform rotational distortion (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hohert, Geoffrey; Pahlevaninezhad, Hamid; Lee, Anthony; Lane, Pierre M.

    2016-03-01

    Endoscopic catheter-based imaging systems that employ a 2-dimensional rotary or 3-dimensional rotary-pullback scanning mechanism require constant angular velocity at the distal tip to ensure correct angular registration of the collected signal. Non-uniform rotational distortion (NURD) - often present due to a variety of mechanical issues - can result in inconsistent position and velocity profiles at the tip, limiting the accuracy of any measurements. Since artifacts like NURD are difficult to identify and characterize during tissue imaging, phantoms with well-defined patterns have been used to quantify position and/or velocity error. In this work we present a fast, versatile, and cost-effective method for making fused deposition modeling 3D printed phantoms for identifying and quantifying NURD errors along an arbitrary user-defined pullback path. Eight evenly-spaced features are present at the same orientation at all points on the path such that deviations from expected geometry can be quantified for the imaging catheter. The features are printed vertically and then folded together around the path to avoid issues with printer head resolution. This method can be adapted for probes of various diameters and for complex imaging paths with multiple bends. We demonstrate imaging using the 3D printed phantoms with a 1mm diameter rotary-pullback OCT catheter and system as a means of objectively evaluating the mechanical performance of similarly constructed probes.

  8. Bulk breakdown in rexolite for non-uniform field geometries and single polarity pulses <10 microseconds.

    SciTech Connect

    Savage, Mark Edward; Stoltzfus, Brian Scott

    2005-06-01

    Although there is much written in regards to voltage breakdown of polymeric insulators under AC and DC conditions, much less is written involving Rexolite{copyright}(1422), non-uniform field geometries, and impulse conditions. Yet, in order to design optimized pulsed power systems with some desired degree of reliability, understanding the behavior of this type of insulating system is needed. Specifically, Sandia National Laboratory's ZR project, which will use anode plugs in the vacuum stack (thus increasing the electrical stress in the Rexolite insulators), needs to be able to estimate the reliability of these vacuum stack insulators. In an effort to estimate the insulator's lifetime small scale testing is in progress. Nine samples have been tested so far and at least ten more will be tested. Results from the current testing suggest that the Rexolite 'ages' from pulse to pulse, that there is some volume dependence on breakdown strength, and that the electrode-vacuum-insulator interface has an affect on the insulator lifetime.

  9. Effects of the non-uniform initial environment and the guide field on the plasmoid instability

    SciTech Connect

    Ni, Lei; Lin, Jun; Murphy, Nicholas A.

    2013-06-15

    Effects of non-uniform initial mass density and temperature on the plasmoid instability are studied via 2.5-dimensional resistive magnetohydrodynamic (MHD) simulations. Our results indicate that the development of the plasmoid instability is apparently prevented when the initial plasma density at the center of the current sheet is higher than that in the upstream region. As a result, the higher the plasma density at the center and the lower the plasma β in the upstream region, the higher the critical Lundquist number needed for triggering secondary instabilities. When β=0.2, the critical Lundquist number is higher than 10{sup 4}. For the same Lundquist number, the magnetic reconnection rate is lower for the lower plasma β case. Oppositely, when the initial mass density is uniform and the Lundquist number is low, the magnetic reconnection rate turns out to be higher for the lower plasma β case. For the high Lundquist number case (>10{sup 4}) with uniform initial mass density, the magnetic reconnection is not affected by the initial plasma β and the temperature distribution. Our results indicate that the guide field has a limited impact on the plasmoid instability in resistive MHD.

  10. 2D Flow patterning in Hele-Shaw configurations using Non-Uniform Electroosmotic Slip

    NASA Astrophysics Data System (ADS)

    Boyko, Evgeniy; Rubin, Shimon; Gat, Amir; Bercovici, Moran

    2015-11-01

    We present an analytical study, validated by numerical simulations, of electroosmotic flow in a Hele-Shaw configuration with non-uniform zeta potential distribution. Applying the lubrication approximation and assuming thin electric double layer, we derive a pair of uncoupled Poisson equations for the pressure and the stream function, and show that the inhomogeneous parts in these equations are governed by gradients in zeta potential parallel and perpendicular to the applied electric field, respectively. We obtain a solution for the case of a disk with uniform zeta potential and show that the flow field created is an exact dipole, even in the immediate vicinity of the disk. We then illustrate the ability to generate complex flow fields using superposition of such disks. Furthermore, we study the inverse problem in which we define the desired flow pattern and solve for the zeta potential distribution required in order to establish it. We demonstrate that such inverse problem solutions can be used to create directional flows confined within narrow regions, without physical walls. We show that these solutions can be assembled to create complex microfluidic networks, composed of intersecting channels and turns, which are basic building blocks in microfluidic devices.

  11. Flow patterning in Hele-Shaw configurations using non-uniform electro-osmotic slip

    NASA Astrophysics Data System (ADS)

    Boyko, Evgeniy; Rubin, Shimon; Gat, Amir D.; Bercovici, Moran

    2015-10-01

    We present an analytical study of electro-osmotic flow in a Hele-Shaw configuration with non-uniform zeta potential distribution. Applying the lubrication approximation and assuming thin electric double layer, we obtain a pair of uncoupled Poisson equations for the pressure and depth-averaged stream function, and show that the inhomogeneous parts in these equations are governed by gradients in zeta potential parallel and perpendicular to the applied electric field, respectively. We obtain a solution for the case of a disk-shaped region with uniform zeta potential and show that the flow field created is an exact dipole, even in the immediate vicinity of the disk. In addition, we study the inverse problem where the desired flow field is known and solve for the zeta potential distribution required in order to establish it. Finally, we demonstrate that such inverse problem solutions can be used to create directional flows confined within narrow regions, without physical walls. Such solutions are equivalent to flow within channels and we show that these can be assembled to create complex microfluidic networks, composed of intersecting channels and turns, which are basic building blocks in microfluidic devices.

  12. n-dimensional non uniform rational b-splines for metamodeling

    SciTech Connect

    Turner, Cameron J; Crawford, Richard H

    2008-01-01

    Non Uniform Rational B-splines (NURBs) have unique properties that make them attractive for engineering metamodeling applications. NURBs are known to accurately model many different continuous curve and surface topologies in 1- and 2-variate spaces. However, engineering metamodels of the design space often require hypervariate representations of multidimensional outputs. In essence, design space metamodels are hyperdimensional constructs with a dimensionality determined by their input and output variables. To use NURBs as the basis for a metamodel in a hyperdimensional space, traditional geometric fitting techniques must be adapted to hypervariate and hyperdimensional spaces composed of both continuous and discontinuous variable types. In this paper, they describe the necessary adaptations for the development of a NURBs-based metamodel called a Hyperdimensional Performance Model or HyPerModel. HyPerModels are capable of accurately and reliably modeling nonlinear hyperdimensional objects defined by both continuous and discontinuous variables of a wide variety of topologies, such as those that define typical engineering design spaces. They demonstrate this ability by successfully generating accurate HyPerModels of 10 trial functions laying the foundation for future work with N-dimensional NURBs in design space applications.

  13. Nonlinear motion of non-uniform current-vortex sheets in MHD Richtmyer-Meshkov instability

    NASA Astrophysics Data System (ADS)

    Matsuoka, Chihiro; Nishihara, Katsunobu; Sano, Takayoshi

    2013-10-01

    When a supernova explosion occurs, materials that composed the star scatter in a high speed with a strong shock wave. These scattered materials, called ``supernova remnants'' (SNR), expand into the space and finally become a source in order to create new solar systems. It is known that SNR have a strong magnetic field compared to the surrounding interstellar medium; however, there exist few models to explain this extraordinary magnetic amplification mechanism in SNR. Here, we consider the Richtmyer-Meshkov instability in magnetohydrodynamic flows (MHD-RMI) and construct a model in order to describe the magnetic amplification in SNR. Due to the existence of the density jump, the tangential component of the magnetic field between the interface is different; therefore, the interface in MHD-RMI becomes a (non-uniform) current-vortex sheet. In this study, we investigate motion of this current-vortex sheet using the vortex blob method. We show that the current induced on a vortex sheet leads to a strong amplification of the magnetic field when the Lorenz force term is sufficiently small, and present various interfacial profiles depending on the magnitude of the Atwood number and Lorenz force. This work was supported by a Grant-in-Aid for Scientific Research (C) from the Japan Society for the Promotion of Science.

  14. Identifying Microlenses In Large, Non-uniformly Sampled Surveys: The Case Of PTF

    NASA Astrophysics Data System (ADS)

    Price-Whelan, Adrian M.; Agúeros, M.; Fournier, A.; Ofek, E.; Street, R.

    2012-05-01

    Many current photometric, time-domain surveys are driven by specific goals, such as supernova searches, transiting exoplanet discoveries, or stellar variability studies, which set the cadence with which individual fields get re-imaged. In the case of the Palomar Transient Factory (PTF), several such sub-surveys are being conducted in parallel, leading to an extremely non-uniform sampling gradient over the survey footprint of nearly 20,000 deg^2: while the typical 7.26 deg^2 PTF field has been imaged 15 times, 1000 deg^2 of the survey has been observed more than 150 times. We use the existing PTF data to study the trade-off between a large survey footprint and irregular sampling when searching for microlensing events, and to examine the probability that such events can be recovered in these data. We conduct Monte Carlo simulations to evaluate our detection efficiency in a hypothetical survey field as a function of both the baseline and number of observations. We also apply variability statistics to systematically differentiate between periodic, transient, and flat light curves. Preliminary results suggest that both recovery and discovery of microlensing events are possible with a careful consideration of photometric systematics. This work can help inform predictions about the observability of microlensing signals in future wide-field time-domain surveys such as that of LSST.

  15. Non-Uniform Displacements within the Achilles Tendon observed during Passive and Eccentric Loading

    PubMed Central

    Slane, Laura Chernak; Thelen, Darryl G.

    2014-01-01

    The goal of this study was to investigate Achilles tendon tissue displacement patterns under passive and eccentric loading conditions. Nine healthy young adults were positioned prone on an examination table with their foot secured to a rotating footplate aligned with the ankle. Subjects cyclically rotated their ankle over a 25 deg range of motion at 0.5 Hz. An inertial load geared to the footplate induced eccentric plantarflexor contractions with dorsiflexion. Passive cyclic ankle motion was also performed over the same angular range of motion. An ultrasound transducer positioned over the distal Achilles tendon was used to collect radiofrequency (RF) images at 70 frames/sec. Two-dimensional ultrasound elastographic analysis of the RF data was used to track tendon tissue displacements throughout the cyclic motion. Non-uniform tissue displacement patterns were observed in all trials, with the deeper portions of the Achilles tendon consistently exhibiting larger displacements than the superficial tendon (average of 0.9–2.6 mm larger). Relative to the passive condition, eccentric loading consistently induced smaller tissue displacements in all tendon regions, except for the superficial tendon in a flexed knee posture. Significantly greater overall tissue displacement was observed in a more extended knee posture (30 deg) relative to a flexed knee posture (90 deg). These spatial- and posture-dependent displacement patterns suggest that the tendon undergoes nonuniform deformation under in vivo loading conditions. Such behavior could reflect relative sliding between the distinct tendon fascicles that arise from the gastrocnemius and soleus muscles. PMID:25150898

  16. Flux measurements in the near surface layer over a non-uniform crop surface in China

    NASA Astrophysics Data System (ADS)

    Gao, Z.; Bian, L.; Liu, S.

    2005-06-01

    Eddy covariance measurements were conducted on fluxes of moisture, heat and CO2 in a near-surface layer over a non-uniform crop surface in an agricultural ecosystem in the central plain of China from 10 June to 20 July 2002. During this period, the mean canopy height was about 0.50 m. The study site consisted of grass (10% of area), bean (15%), corn (15%) and rice (60%). Based on footprint analysis, we expected >90% of the measured flux (at a height of 4 m above ground surface) to occur within the nearest 600 m of upwind area. We examined interdiurnal variations in the components of the surface energy balance and in CO2 flux. Results show that the pattern of energy partition had no obvious variation during the season. Daytime absorption of CO2 flux by the crop canopy suddenly increased after thunderstorm events. We examined the energy budget closure and found it to be around 0.85. We compared energy partitioning for all rain-free days, and found energy imbalance was more significant for the 1~3 days after rainy events and energy components almost achieve balance for the other rain-free days. It indicated that the cold or warm rainwater infiltrating into soil made problems.

  17. Railroad inspection based on ACFM employing a non-uniform B-spline approach

    NASA Astrophysics Data System (ADS)

    Chacón Muñoz, J. M.; García Márquez, F. P.; Papaelias, M.

    2013-11-01

    The stresses sustained by rails have increased in recent years due to the use of higher train speeds and heavier axle loads. For this reason surface and near-surface defects generate by Rolling Contact Fatigue (RCF) have become particularly significant as they can cause unexpected structural failure of the rail, resulting in severe derailments. The accident that took place in Hatfield, UK (2000), is an example of a derailment caused by the structural failure of a rail section due to RCF. Early detection of RCF rail defects is therefore of paramount importance to the rail industry. The performance of existing ultrasonic and magnetic flux leakage techniques in detecting rail surface-breaking defects, such as head checks and gauge corner cracking, is inadequate during high-speed inspection, while eddy current sensors suffer from lift-off effects. The results obtained through rail inspection experiments under simulated conditions using Alternating Current Field Measurement (ACFM) probes, suggest that this technique can be applied for the accurate and reliable detection of surface-breaking defects at high inspection speeds. This paper presents the B-Spline approach used for the accurate filtering the noise of the raw ACFM signal obtained during high speed tests to improve the reliability of the measurements. A non-uniform B-spline approximation is employed to calculate the exact positions and the dimensions of the defects. This method generates a smooth approximation similar to the ACFM dataset points related to the rail surface-breaking defect.

  18. Regional paleofire regimes affected by non-uniform climate, vegetation and human drivers

    PubMed Central

    Blarquez, Olivier; Ali, Adam A.; Girardin, Martin P.; Grondin, Pierre; Fréchette, Bianca; Bergeron, Yves; Hély, Christelle

    2015-01-01

    Climate, vegetation and humans act on biomass burning at different spatial and temporal scales. In this study, we used a dense network of sedimentary charcoal records from eastern Canada to reconstruct regional biomass burning history over the last 7000 years at the scale of four potential vegetation types: open coniferous forest/tundra, boreal coniferous forest, boreal mixedwood forest and temperate forest. The biomass burning trajectories were compared with regional climate trends reconstructed from general circulation models, tree biomass reconstructed from pollen series, and human population densities. We found that non-uniform climate, vegetation and human drivers acted on regional biomass burning history. In the open coniferous forest/tundra and dense coniferous forest, the regional biomass burning was primarily shaped by gradual establishment of less climate-conducive burning conditions over 5000 years. In the mixed boreal forest an increasing relative proportion of flammable conifers in landscapes since 2000 BP contributed to maintaining biomass burning constant despite climatic conditions less favourable to fires. In the temperate forest, biomass burning was uncoupled with climatic conditions and the main driver was seemingly vegetation until European colonization, i.e. 300 BP. Tree biomass and thus fuel accumulation modulated fire activity, an indication that biomass burning is fuel-dependent and notably upon long-term co-dominance shifts between conifers and broadleaf trees. PMID:26330162

  19. Regional paleofire regimes affected by non-uniform climate, vegetation and human drivers.

    PubMed

    Blarquez, Olivier; Ali, Adam A; Girardin, Martin P; Grondin, Pierre; Fréchette, Bianca; Bergeron, Yves; Hély, Christelle

    2015-01-01

    Climate, vegetation and humans act on biomass burning at different spatial and temporal scales. In this study, we used a dense network of sedimentary charcoal records from eastern Canada to reconstruct regional biomass burning history over the last 7000 years at the scale of four potential vegetation types: open coniferous forest/tundra, boreal coniferous forest, boreal mixedwood forest and temperate forest. The biomass burning trajectories were compared with regional climate trends reconstructed from general circulation models, tree biomass reconstructed from pollen series, and human population densities. We found that non-uniform climate, vegetation and human drivers acted on regional biomass burning history. In the open coniferous forest/tundra and dense coniferous forest, the regional biomass burning was primarily shaped by gradual establishment of less climate-conducive burning conditions over 5000 years. In the mixed boreal forest an increasing relative proportion of flammable conifers in landscapes since 2000 BP contributed to maintaining biomass burning constant despite climatic conditions less favourable to fires. In the temperate forest, biomass burning was uncoupled with climatic conditions and the main driver was seemingly vegetation until European colonization, i.e. 300 BP. Tree biomass and thus fuel accumulation modulated fire activity, an indication that biomass burning is fuel-dependent and notably upon long-term co-dominance shifts between conifers and broadleaf trees. PMID:26330162

  20. Tools for experimental characterization of the non-uniform rotational distortion in intravascular OCT probes

    NASA Astrophysics Data System (ADS)

    Dufour, Marc L.; Bisaillon, Charles-Etienne; Lamouche, Guy; Vergnole, Sebastien; Hewko, Mark; D'Amours, Frédéric; Padioleau, Christian; Sowa, Michael

    2011-03-01

    The Industrial Material Institute (IMI) together with the Institute for Biodiagnostic (IBD) has developed its own optical catheters for cardiovascular imaging applications. Those catheters have been used experimentally in the in vitro coronary artery model of the Langendorff beating heart and in a percutaneous coronary intervention procedure in a porcine model. For some catheter designs, non-uniform rotational distortion (NURD) can be observed as expected from past experience with intra-vascular ultrasound (IVUS) catheters. A two-dimensional (2D) coronary artery test bench that simulates the path into the coronary arteries has been developed. The presence or absence of NURD can be assessed with the test bench using a custom-built cardiovascular Optical Coherence Tomography (OCT) imaging system. A square geometry instead of the circular shape of an artery is used to simulate the coronary arteries. Thereby, it is easier to visualize NURD when it is present. The accumulated torsion induced by the friction on the catheter is measured along the artery path. NURD is induced by the varying friction force that is balanced by the accumulated torsion force. The pullback force is measured and correlated with NURD observed in the 2D test bench. Finally, a model is presented to help understanding the mechanical constraint that leads to the friction force variations.

  1. Vibration and Noise Characteristics of Elliptical Gears due to Non-Uniform Rotation

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Nagamura, Kazuteru; Ikejo, Kiyotaka

    Elliptical gear is a typical non-circular gear, which transmits a variable-ratio rotation and power simultaneously. Due to the non-uniform rotation, the vibration and noise of elliptical gears demonstrate particular characteristics which should be paid attention to in practical application. In this paper, two elliptical gears, which are a single elliptical gear and a double elliptical gear, have been investigated to analyze the vibration and noise characteristics of elliptical gears. The corresponding circular gears for comparison are also investigated. General factors including the torque, the rotation speed, the gear vibration acceleration and the gear noise of the four test gears are measured by running test. The root mean square of the Circumferential Vibration Acceleration (CVA) and the sound pressure level of the noise of elliptical gears are obtained from the measured results and compared with those of circular gears to clarify the vibration and noise characteristics of elliptical gears. Furthermore, the frequency analysis of the CVA of elliptical gears is conducted by Fast Fourier Transform Algorithm (FFT) and compared with that of circular gears. The main vibration component of elliptical gear is uncovered according to the obtained frequency spectra. In addition, the Critical Rotation Speeds of Tooth Separation (CRSTS) of elliptical gear is obtained and its relation with load torque is unveiled.

  2. N-dimensional non uniform rational B-splines for metamodeling

    SciTech Connect

    Turner, Cameron J; Crawford, Richard H

    2008-01-01

    Non Uniform Rational B-splines (NURBs) have unique properties that make them attractive for engineering metamodeling applications. NURBs are known to accurately model many different continuous curve and surface topologies in 1-and 2-variate spaces. However, engineering metamodels of the design space often require hypervariate representations of multidimensional outputs. In essence, design space metamodels are hyperdimensional constructs with a dimensionality determined by their input and output variables. To use NURBs as the basis for a metamodel in a hyperdimensional space, traditional geometric fitting techniques must be adapted to hypervariate and hyperdimensional spaces composed of both continuous and discontinuous variable types. In this paper, we describe the necessary adaptations for the development of a NURBs-based metamodel called a Hyperdimensional Performance Model or HyPerModel. HyPerModels are capable of accurately and reliably modeling nonlinear hyperdimensional objects defined by both continuous and discontinuous variables of a wide variety of topologies, such as those that define typical engineering design spaces. We demonstrate this ability by successfully generating accurate HyPerModels of 10 trial functions laying the foundation for future work with N-dimensional NURBs in design space applications.

  3. Non-uniform changes in membrane receptors in the rat urinary bladder following outlet obstruction.

    PubMed

    Zeng, Jianwen; Ekman, Mari; Jiang, Chonghe; Uvelius, Bengt; Swärd, Karl

    2015-09-01

    The aim of the present study was to investigate the expression and distribution of membrane receptors after bladder outlet obstruction (BOO). Partial bladder outlet obstruction (BOO) was induced in female rats and bladders were harvested after either 10 days or 6 weeks of BOO. The expression of different receptors was surveyed by microarrays and corroborated by immunohistochemistry and western blotting. A microarray experiment identified 10 membrane receptors that were differentially expressed compared to sham-operated rats including both upregulated and downregulated receptors. Four of these were selected for functional experiments on the basis of magnitude of change and relevance to bladder physiology. At 6 weeks of BOO, maximal contraction was reduced for neuromedin B and vasopressin (AVP), consistent with reductions of receptor mRNA levels. Glycine receptor-induced contraction on the other hand was increased and receptor mRNA expression was accordingly upregulated. Maximal relaxation by the β3-adrenergic receptor agonist CL316243 was reduced as was the receptor mRNA level. Immunohistochemistry supported reduced expression of neuromedin B receptors, V1a receptors and β3-adrenergic receptors, but glycine receptor expression appeared unchanged. Western blotting confirmed repression of V1a receptors and induction of glycine receptors in BOO. mRNA for vasopressin was detectable in the bladder, suggesting local AVP production. We conclude that changes in receptor expression following bladder outlet obstruction are non-uniform. Some receptors are upregulated, conferring increased responsiveness to agonist, whereas others are downregulated, leading to decreased agonist-induced responses. This study might help to select pharmacological agents that are effective in modulating lower urinary tract symptoms in BOO. PMID:26004535

  4. Electron trapping non-uniformity in high-pressure-Bridgman-grown CdZnTe

    SciTech Connect

    Amman, Mark; Lee, Julie S.; Luke, Paul N.

    2002-05-09

    Gamma-ray spectroscopy is a valuable tool of science and technology. Many applications for this tool are in need of a detector technology capable of achieving excellent energy resolution and efficient detection while operating at room temperature. Detectors based on the material cadmium zinc telluride (CdZnTe) could potentially meet this need if certain material deficiencies are addressed. The coplanar-grid as well as other electron-only detection techniques are effective in overcoming some of the material problems of CdZnTe and, consequently, have led to efficient gamma-ray detectors with good energy resolution while operating at room temperature. At the present time, the performance of these detectors is mainly limited by the degree of uniformity in electron generation and transport. Despite recent progress in the growth of CdZnTe material, small variations in these properties remain a barrier to the widespread success of such detectors. Alpha-particle response characterization of Cd ZnTe crystals fabricated into simple planar detectors provides an effective tool to accurately study such variations. We have used a finely collimated alpha source to produce two-dimensional maps of detector response. For a number of crystals, a clear correlation has been observed between their alpha response maps and the distribution of tellurium inclusions inside the crystals. An analysis of the induced charge signals indicates that regions of enhanced electron trapping are associated with the inclusions, and that these regions extend beyond the physical size of the inclusions. Such regions introduce non-uniform electron trapping in the material that then degrades the spectroscopic performance of the material as a gamma-ray detector.

  5. Quantitative multi-pinhole small-animal SPECT: uniform versus non-uniform Chang attenuation correction

    NASA Astrophysics Data System (ADS)

    Wu, C.; de Jong, J. R.; Gratama van Andel, H. A.; van der Have, F.; Vastenhouw, B.; Laverman, P.; Boerman, O. C.; Dierckx, R. A. J. O.; Beekman, F. J.

    2011-09-01

    Attenuation of photon flux on trajectories between the source and pinhole apertures affects the quantitative accuracy of reconstructed single-photon emission computed tomography (SPECT) images. We propose a Chang-based non-uniform attenuation correction (NUA-CT) for small-animal SPECT/CT with focusing pinhole collimation, and compare the quantitative accuracy with uniform Chang correction based on (i) body outlines extracted from x-ray CT (UA-CT) and (ii) on hand drawn body contours on the images obtained with three integrated optical cameras (UA-BC). Measurements in phantoms and rats containing known activities of isotopes were conducted for evaluation. In 125I, 201Tl, 99mTc and 111In phantom experiments, average relative errors comparing to the gold standards measured in a dose calibrator were reduced to 5.5%, 6.8%, 4.9% and 2.8%, respectively, with NUA-CT. In animal studies, these errors were 2.1%, 3.3%, 2.0% and 2.0%, respectively. Differences in accuracy on average between results of NUA-CT, UA-CT and UA-BC were less than 2.3% in phantom studies and 3.1% in animal studies except for 125I (3.6% and 5.1%, respectively). All methods tested provide reasonable attenuation correction and result in high quantitative accuracy. NUA-CT shows superior accuracy except for 125I, where other factors may have more impact on the quantitative accuracy than the selected attenuation correction.

  6. Ice friction: Role of non-uniform frictional heating and ice premelting

    NASA Astrophysics Data System (ADS)

    Persson, B. N. J.

    2015-12-01

    The low friction of ice is usually attributed to the formation of a thin water film due to melting of ice by frictional heating. Melting of ice is a first order phase transition where physical quantities like mass density, the elastic modulus or the shear strength changes abruptly at the transition temperature. Thus, one may expect the friction coefficient to change abruptly at some characteristic sliding speed, when the melt water film is produced. We show that taking into account that, due to non-uniform frictional heating, melting does not occur simultaneously in all the ice contact regions, the transition is not abrupt but still more rapid (as a function of sliding speed) than observed experimentally. The slower than expected drop in the friction with increasing sliding speed may be a consequence of the following paradoxical phenomena: before the melt-water film is formed, the friction of ice is high and a large frictional heating occur which may result in the melting of the ice. If a thin (nanometer) water film would form, the friction becomes low which results in small frictional heating and the freezing of the water film. This suggests a region in sliding speed where a thin (nanometer) surface layer of the ice may be in a mixed state with small ice-like and water-like domains, which fluctuate rapidly in space and time. Alternatively, and more likely, heat-softening of the ice may occur resulting in a thin, statistically homogeneous (in the lateral direction) layer of disordered ice, with a shear strength which decreases continuously as the ice surface temperature approaches the bulk melting temperature. This layer could be related to surface premelting of ice. Using a phenomenological expression for the frictional shear stress, I show that the calculated ice friction is in good agreement with experimental observations.

  7. Topographic viscous fingering: fluid-fluid displacement in a channel of non-uniform gap width.

    PubMed

    Woods, Andrew W; Mingotti, Nicola

    2016-10-13

    We consider the displacement of one fluid by a second immiscible fluid through a long, thin permeable channel whose thickness and permeability decrease away from the axis of the channel. We build a model that illustrates how the shape of the fluid-fluid interface evolves in time. We find that if the injected fluid is of the same viscosity as the original fluid, then the cross-channel variations in permeability and thickness tend to focus the flow along the centre of the channel. If the viscosity of the injected fluid is smaller than the original fluid, then this flow focusing intensifies, leading to very poor sweep of the original fluid in the system, with the injected fluid bypassing much of the channel. We also show that if the viscosity ratio of the injected fluid to the original fluid is sufficiently large, then a blunt nose may develop at the leading edge of the injected fluid, whereas the remainder of the fluid-fluid interface becomes stretched out along the edges of the channel. This leads to a much more efficient sweep of the original fluid from the channel. We generalize the model to illustrate how buoyancy forces and capillary pressure affect the evolution of the system and compare our model predictions with some simple laboratory experiments. This partial stabilization of a fluid interface in a channel of non-uniform width represents a generalization of the classical Saffman-Taylor instability, and our nonlinear solutions for the evolution of the interface highlight the importance of cross-channel variations in permeability and thickness in modelling flow in channelled reservoirs.This article is part of the themed issue 'Energy and the subsurface'. PMID:27597790

  8. Accurate determination of rates from non-uniformly sampled relaxation data.

    PubMed

    Stetz, Matthew A; Wand, A Joshua

    2016-08-01

    The application of non-uniform sampling (NUS) to relaxation experiments traditionally used to characterize the fast internal motion of proteins is quantitatively examined. Experimentally acquired Poisson-gap sampled data reconstructed with iterative soft thresholding are compared to regular sequentially sampled (RSS) data. Using ubiquitin as a model system, it is shown that 25 % sampling is sufficient for the determination of quantitatively accurate relaxation rates. When the sampling density is fixed at 25 %, the accuracy of rates is shown to increase sharply with the total number of sampled points until eventually converging near the inherent reproducibility of the experiment. Perhaps contrary to some expectations, it is found that accurate peak height reconstruction is not required for the determination of accurate rates. Instead, inaccuracies in rates arise from inconsistencies in reconstruction across the relaxation series that primarily manifest as a non-linearity in the recovered peak height. This indicates that the performance of an NUS relaxation experiment cannot be predicted from comparison of peak heights using a single RSS reference spectrum. The generality of these findings was assessed using three alternative reconstruction algorithms, eight different relaxation measurements, and three additional proteins that exhibit varying degrees of spectral complexity. From these data, it is revealed that non-linearity in peak height reconstruction across the relaxation series is strongly correlated with errors in NUS-derived relaxation rates. Importantly, it is shown that this correlation can be exploited to reliably predict the performance of an NUS-relaxation experiment by using three or more RSS reference planes from the relaxation series. The RSS reference time points can also serve to provide estimates of the uncertainty of the sampled intensity, which for a typical relaxation times series incurs no penalty in total acquisition time. PMID:27393626

  9. Size Distribution Imaging by Non-Uniform Oscillating-Gradient Spin Echo (NOGSE) MRI

    PubMed Central

    Shemesh, Noam; Álvarez, Gonzalo A.; Frydman, Lucio

    2015-01-01

    Objects making up complex porous systems in Nature usually span a range of sizes. These size distributions play fundamental roles in defining the physicochemical, biophysical and physiological properties of a wide variety of systems – ranging from advanced catalytic materials to Central Nervous System diseases. Accurate and noninvasive measurements of size distributions in opaque, three-dimensional objects, have thus remained long-standing and important challenges. Herein we describe how a recently introduced diffusion-based magnetic resonance methodology, Non-Uniform-Oscillating-Gradient-Spin-Echo (NOGSE), can determine such distributions noninvasively. The method relies on its ability to probe confining lengths with a (length)6 parametric sensitivity, in a constant-time, constant-number-of-gradients fashion; combined, these attributes provide sufficient sensitivity for characterizing the underlying distributions in μm-scaled cellular systems. Theoretical derivations and simulations are presented to verify NOGSE’s ability to faithfully reconstruct size distributions through suitable modeling of their distribution parameters. Experiments in yeast cell suspensions – where the ground truth can be determined from ancillary microscopy – corroborate these trends experimentally. Finally, by appending to the NOGSE protocol an imaging acquisition, novel MRI maps of cellular size distributions were collected from a mouse brain. The ensuing micro-architectural contrasts successfully delineated distinctive hallmark anatomical sub-structures, in both white matter and gray matter tissues, in a non-invasive manner. Such findings highlight NOGSE’s potential for characterizing aberrations in cellular size distributions upon disease, or during normal processes such as development. PMID:26197220

  10. Supersonic Mass Flux Measurements via Tunable Diode Laser Absorption and Non-Uniform Flow Modeling

    NASA Technical Reports Server (NTRS)

    Chang, Leyen S.; Strand, Christopher L.; Jeffries, Jay B.; Hanson, Ronald K.; Diskin, Glenn S.; Gaffney, Richard L.; Capriotti, Diego P.

    2011-01-01

    Measurements of mass flux are obtained in a vitiated supersonic ground test facility using a sensor based on line-of-sight (LOS) diode laser absorption of water vapor. Mass flux is determined from the product of measured velocity and density. The relative Doppler shift of an absorption transition for beams directed upstream and downstream in the flow is used to measure velocity. Temperature is determined from the ratio of absorption signals of two transitions (lambda(sub 1)=1349 nm and lambda(sub 2)=1341.5 nm) and is coupled with a facility pressure measurement to obtain density. The sensor exploits wavelength-modulation spectroscopy with second-harmonic detection (WMS-2f) for large signal-to-noise ratios and normalization with the 1f signal for rejection of non-absorption related transmission fluctuations. The sensor line-of-sight is translated both vertically and horizontally across the test section for spatially-resolved measurements. Time-resolved measurements of mass flux are used to assess the stability of flow conditions produced by the facility. Measurements of mass flux are within 1.5% of the value obtained using a facility predictive code. The distortion of the WMS lineshape caused by boundary layers along the laser line-of-sight is examined and the subsequent effect on the measured velocity is discussed. A method for correcting measured velocities for flow non-uniformities is introduced and application of this correction brings measured velocities within 4 m/s of the predicted value in a 1630 m/s flow.

  11. Groundwater Mounding in Non-uniform Aquifers with Implications for Managed Aquifer Recharge

    NASA Astrophysics Data System (ADS)

    Zlotnik, V. A.; Noel, P.; Kacimov, A. R.; Al Maktoumi, A. K.

    2015-12-01

    Many areas of the world (e.g. the Middle East and North Africa countries) are deficient in observation networks and hydrogeological data needed for Managed Aquifer Recharge (MAR) design. Therefore, diagnostic analytical approaches are appropriate for feasibility studies of MAR. It was found that the common assumption of aquifer thickness uniformity often does not hold, especially in mountainous watersheds. However, the only practical result available for non-uniform aquifers was developed for well hydraulics applications (point sinks or sources) by Hantush (1962), while the recharge zones may cover large areas on the scale of kilometers, such as temporarily filled impoundments (natural and engineered reservoirs in wadis, depressions, trenches, etc.) or perennial streams accepting massive treated wastewater discharge. To address these important, but overlooked MAR problems in sloping aquifers, a set of new closed-form analytical solutions for water table elevations were obtained. Interestingly, the 2D groundwater flow equation acquires the advection-dispersion equation form in these cases. The quadratures in closed-form solutions obtained by the Green's function method converge rapidly. These models account for both shapes and orientations of sources with respect to the direction of the aquifer base gradient. Qualitatively, solutions in sloping aquifers have an important trait: the mounding is limited in time and space, unlike in aquifers with a horizontal base. Aquifers with the greater slopes have the lesser potential of waterlogging from the rising water table and different storage characteristics (height and volume of locally stored water). Computational aspects of these solutions for MAR analyses are illustrated by example utilizing regional aquifer properties near Az Zarqa River, Jordan. (This study was supported by a grant from USAID-FABRI, project contract: AID-OAA-TO-11-00049, Subcontract: 1001624 -12S-19745).

  12. Low-salinity plume detachment under non-uniform summer wind off the Changjiang Estuary

    NASA Astrophysics Data System (ADS)

    Ge, Jianzhong; Ding, Pingxing; Chen, Changsheng

    2015-04-01

    In the past, two physical mechanisms, baroclinic instability (BI) and strong asymmetric tidal mixing (SATM) during the spring tidal period, were proposed for the offshore detachment of the low-salinity plume over the inner shelf of the East China Sea (ECS). These two mechanisms were re-examined using both observations and a fully three-dimensional (3-D), high-resolution, unstructured-grid, free-surface, primitive-equation, Finite-Volume Community Ocean Model (FVCOM). The observed currents and salinities showed that the plume was characterized by a two-layer system, in which the upper layer is mainly driven by the river discharge-induced buoyancy flow and the lower layer is predominantly controlled by tidal mixing and rectification. The SATM mechanism was based on the model run without calibration against observed currents and salinity around the plume region, so that it should be applied with caution to a realistic condition observed on the inner shelf of the ECS. The BI mechanism was derived under a condition without consideration of tidal mixing. Although BI could still occur along the frontal zone when tides were included, it was unable to produce a single, large, detached low-salinity lens observed on the inner shelf of the ECS. The process-oriented model experiment results suggest that for a given river discharge and realistic tidal flow, the spatially non-uniform southwesterly surface wind during the southeast monsoon-dominant summer could increase frontal spatial variability and thus produce a significant offshore detachment of low-salinity water on the inner shelf of East China Sea.

  13. Computationally efficient real-time interpolation algorithm for non-uniform sampled biosignals

    PubMed Central

    Eftekhar, Amir; Kindt, Wilko; Constandinou, Timothy G.

    2016-01-01

    This Letter presents a novel, computationally efficient interpolation method that has been optimised for use in electrocardiogram baseline drift removal. In the authors’ previous Letter three isoelectric baseline points per heartbeat are detected, and here utilised as interpolation points. As an extension from linear interpolation, their algorithm segments the interpolation interval and utilises different piecewise linear equations. Thus, the algorithm produces a linear curvature that is computationally efficient while interpolating non-uniform samples. The proposed algorithm is tested using sinusoids with different fundamental frequencies from 0.05 to 0.7 Hz and also validated with real baseline wander data acquired from the Massachusetts Institute of Technology University and Boston's Beth Israel Hospital (MIT-BIH) Noise Stress Database. The synthetic data results show an root mean square (RMS) error of 0.9 μV (mean), 0.63 μV (median) and 0.6 μV (standard deviation) per heartbeat on a 1 mVp–p 0.1 Hz sinusoid. On real data, they obtain an RMS error of 10.9 μV (mean), 8.5 μV (median) and 9.0 μV (standard deviation) per heartbeat. Cubic spline interpolation and linear interpolation on the other hand shows 10.7 μV, 11.6 μV (mean), 7.8 μV, 8.9 μV (median) and 9.8 μV, 9.3 μV (standard deviation) per heartbeat. PMID:27382478

  14. Guided filter and adaptive learning rate based non-uniformity correction algorithm for infrared focal plane array

    NASA Astrophysics Data System (ADS)

    Sheng-Hui, Rong; Hui-Xin, Zhou; Han-Lin, Qin; Rui, Lai; Kun, Qian

    2016-05-01

    Imaging non-uniformity of infrared focal plane array (IRFPA) behaves as fixed-pattern noise superimposed on the image, which affects the imaging quality of infrared system seriously. In scene-based non-uniformity correction methods, the drawbacks of ghosting artifacts and image blurring affect the sensitivity of the IRFPA imaging system seriously and decrease the image quality visibly. This paper proposes an improved neural network non-uniformity correction method with adaptive learning rate. On the one hand, using guided filter, the proposed algorithm decreases the effect of ghosting artifacts. On the other hand, due to the inappropriate learning rate is the main reason of image blurring, the proposed algorithm utilizes an adaptive learning rate with a temporal domain factor to eliminate the effect of image blurring. In short, the proposed algorithm combines the merits of the guided filter and the adaptive learning rate. Several real and simulated infrared image sequences are utilized to verify the performance of the proposed algorithm. The experiment results indicate that the proposed algorithm can not only reduce the non-uniformity with less ghosting artifacts but also overcome the problems of image blurring in static areas.

  15. Influence of magnetic non-uniformity existing in a rigid rotor supported by a superconducting magnetic bearing on its whirling

    NASA Astrophysics Data System (ADS)

    Kamada, Soichiro; Amano, Ryosuke; Sugiura, Toshihiko

    2014-05-01

    Superconducting magnetic bearings (SMBs) have a significant feature over conventional bearings in terms of supporting a shaft without physical contact while attaining its stability without control. In their large-scale rotary applications, magnetization distribution of a rotor in the circumferential direction can be non-uniform and it would be better to know influence of such circumferential magnetic non-uniformity existing in a rotor on its dynamics, especially on its behaviors in the vicinity of the critical speed. In this study, further developing our previous research, we improved our analytical model so that we can adjust several different degrees of magnetic non-uniformity by arranging multiple magnetization vectors and investigated its influence. First, we simulated dynamical behavior of the system by numerical calculations and their results show that, with increasing the degree of magnetic non-uniformity, the whirling amplitude of the system, together with the difference of the amplitudes in the orthogonal directions in the whirling plane, get larger. Further, the rotational frequency at which the whirling amplitude takes its peak gets lower, which is caused by nonlinearity of the electromagnetic force. We carried out experiments and verified our numerical predicions.

  16. Advanced GF(32) nonbinary LDPC coded modulation with non-uniform 9-QAM outperforming star 8-QAM.

    PubMed

    Liu, Tao; Lin, Changyu; Djordjevic, Ivan B

    2016-06-27

    In this paper, we first describe a 9-symbol non-uniform signaling scheme based on Huffman code, in which different symbols are transmitted with different probabilities. By using the Huffman procedure, prefix code is designed to approach the optimal performance. Then, we introduce an algorithm to determine the optimal signal constellation sets for our proposed non-uniform scheme with the criterion of maximizing constellation figure of merit (CFM). The proposed nonuniform polarization multiplexed signaling 9-QAM scheme has the same spectral efficiency as the conventional 8-QAM. Additionally, we propose a specially designed GF(32) nonbinary quasi-cyclic LDPC code for the coded modulation system based on the 9-QAM non-uniform scheme. Further, we study the efficiency of our proposed non-uniform 9-QAM, combined with nonbinary LDPC coding, and demonstrate by Monte Carlo simulation that the proposed GF(23) nonbinary LDPC coded 9-QAM scheme outperforms nonbinary LDPC coded uniform 8-QAM by at least 0.8dB. PMID:27410549

  17. Stability of Central Finite Difference Schemes on Non-Uniform Grids for 1D Partial Differential Equations with Variable Coefficients

    NASA Astrophysics Data System (ADS)

    Volders, Kim

    2010-09-01

    This paper deals with stability in the numerical solution of general one-dimensional partial differential equations with variable coefficients. We will generalize stability results for central finite difference schemes on non-uniform grids that were obtained by In't Hout & Volders (2009) for the Black-Scholes equation. Subsequently we will apply our stability results to the CEV model.

  18. TH-A-BRF-11: Image Intensity Non-Uniformities Between MRI Simulation and Diagnostic MRI

    SciTech Connect

    Paulson, E

    2014-06-15

    Purpose: MRI simulation for MRI-based radiotherapy demands that patients be setup in treatment position, which frequently involves use of alternative radiofrequency (RF) coil configurations to accommodate immobilized patients. However, alternative RF coil geometries may exacerbate image intensity non-uniformities (IINU) beyond those observed in diagnostic MRI, which may challenge image segmentation and registration accuracy as well as confound studies assessing radiotherapy response when MR simulation images are used as baselines for evaluation. The goal of this work was to determine whether differences in IINU exist between MR simulation and diagnostic MR images. Methods: ACR-MRI phantom images were acquired at 3T using a spin-echo sequence (TE/TR:20/500ms, rBW:62.5kHz, TH/skip:5/5mm). MR simulation images were obtained by wrapping two flexible phased-array RF coils around the phantom. Diagnostic MR images were obtained by placing the phantom into a commercial phased-array head coil. Pre-scan normalization was enabled in both cases. Images were transferred offline and corrected for IINU using the MNI N3 algorithm. Coefficients of variation (CV=σ/μ) were calculated for each slice. Wilcoxon matched-pairs and Mann-Whitney tests compared CV values between original and N3 images and between MR simulation and diagnostic MR images. Results: Significant differences in CV were detected between original and N3 images in both MRI simulation and diagnostic MRI groups (p=0.010, p=0.010). In addition, significant differences in CV were detected between original MR simulation and original and N3 diagnostic MR images (p=0.0256, p=0.0016). However, no significant differences in CV were detected between N3 MR simulation images and original or N3 diagnostic MR images, demonstrating the importance of correcting MR simulation images beyond pre-scan normalization prior to use in radiotherapy. Conclusions: Alternative RF coil configurations used in MRI simulation can Result in

  19. GRBs Redshift Distribution Shape Properties as Confirmation of their Progenitors Population Non-uniformity

    NASA Astrophysics Data System (ADS)

    Arkhangelskaja, I. V.

    optical spectrometers if object located at high z values. The occurrence of minimum in long GRBs redshift distribution allows to conclude non-uniformity of its progenitors population and existence at least two subclasses in long GRB class. The obtained results allow considering that the whole GRB subset with known redshifts usage as "standard candles" for various cosmological tests could be excluded. Before such analysis different GRB samples might be separated and then various subsets could be investigated separately just as short and long events.

  20. Theoretical/numerical model for the transport of non-uniform suspended sediment in open channels

    NASA Astrophysics Data System (ADS)

    Jha, Sanjeev K.; Bombardelli, Fabián A.

    2011-05-01

    In this paper, we address the transport of multi-disperse suspended sediment mixtures in open channels, via the use of the two-fluid model. To that end, we extend previously developed frameworks for the dilute and non-dilute transport of suspended sediment. Within the scope of the Reynolds-averaged Navier-Stokes (RANS) equations, these modeling frameworks comprise mass and momentum equations for both phases (water and sediment). Here, we calculate the distribution of total volumetric concentration of sediment using two approaches: (1) by considering the mixture as represented by a single size; we call this approach Partial two-fluid model for uniform sediments (PTFMU); and (2) by combining the volumetric concentration of the sediment corresponding to several particle size classes; we call this approach Partial two-fluid model for non-uniform sediments (PTFMNU). In the second approach, we propose a methodology for the computation of the overall velocity of the disperse phase as a function of the velocities of each size class. k- ɛ type closures to account for the turbulence in the carrier phase (water) are applied. We also consider the coupling between the two phases through the drag force. Velocities of the carrier and disperse phases, and concentrations for each sediment class size are numerically solved by integrating the differential equations over control volumes. In order to validate our models, we compare numerical results to experimental data of Einstein and Chien [H.A. Einstein, N. Chien, Effects of heavy sediment concentration near the bed on velocity and sediment distribution, MRD sediment series report, University of California, Berkley, 1955] and Taggart et al. [W.C. Taggart, C.A. Yermoli, S. Montes, A. Ippen, Effects of sediment size and gradation on concentration profiles for turbulent flow, Massachusetts Institute of Technology, 1972]. Results of mean velocity of the carrier phase are in close agreement with the experimental data. For the prediction

  1. Flame balls in non-uniform mixtures: existence and finite activation energy effects

    NASA Astrophysics Data System (ADS)

    Daou, Remi; Pearce, Philip; Daou, Joel

    2016-01-01

    The paper's broad motivation, shared by a recent theoretical investigation [Daou and Daou, "Flame balls in mixing layers," Combustion and Flame, Vol. 161 (2014), pp. 2015-2024], is a fundamental but apparently untouched combustion question; specifically, 'What are the critical conditions insuring the successful ignition of a diffusion flame by means of an external energy deposit (spark), after mixing of cold reactants has occurred in a mixing layer?' The approach is based on a generalisation of the concept of Zeldovich flame balls, well known in premixed reactive mixtures, to non-uniform mixtures. This generalisation leads to a free boundary problem (FBP) for axisymmetric flame balls in a two-dimensional mixing layer in the distinguished limit β → ∞ with εL = O(1); here β is the Zeldovich number and εL is a non-dimensional measure of the stoichiometric premixed flame thickness. The existence of such flame balls is the main object of current investigation. Several original contributions are presented. First, an analytical contribution is made by carrying out the analysis of Daou and Daou (2014) in the asymptotic limit εL → 0 to higher order. The results capture, in particular, the dependence of the location of the flame ball centre (argued to represent the optimal ignition location which differs from the stoichiometric location) on εL. Second, two detailed numerical studies of the axisymmetric flame balls are presented for arbitrary values of εL. The first study addresses the infinite-β FBP and the second one the original finite-β problem based on the constant density reaction-diffusion equations. In particular, it is shown that solutions to the FBP exist for arbitrary values of εL while actual finite-β flame balls exist in a specific domain of the β-εL plane, namely for εL less than a maximum value proportional to ?; this scaling is consistent with the existence of solutions to the FBP for arbitrary εL. In fact, the flame ball existence domain

  2. Analysis of impact of non-uniformities on thin-film solar cells and modules with two-dimesional simulations

    NASA Astrophysics Data System (ADS)

    Koishiyev, Galymzhan T.

    Clean and environmentally friendly photovoltaic (PV) technologies are now generally recognized as an alternative solution to many global-scale problems such as energy demand, pollution, and environment safety. The cost ($/kWh) is the primary challenge for all PV technologies. In that respect, thin-film polycrystalline PV technology (CdTe, Cu(In,Ga)Se2, etc), due to its fast production line, large area panels and low material usage, is one of the most promising low-cost technologies. Due to their granular structure, thin-film solar cells are inherently non-uniform. Also, inevitable fluctuations during the multistep deposition process of large area thin-film solar panels and specific manufacturing procedures such as scribing result in non-uniformities. Furthermore, non-uniformities can occur, become more severe, or increase in size during the solar-panel's life cycle due to various environmental conditions (i.e. temperature variation, shading, hail impact, etc). Non-uniformities generally reduce the overall efficiency of solar cells and modules, and their effects therefore need to be well understood. This thesis focuses on the analysis of the effect of non-uniformities on small size solar cells and modules with the help of numerical simulations. Even though the 2-D model developed here can analyze the effect of non-uniformities of any nature, only two specific types of microscopic non-uniformities were addressed here: shunts and weak-diodes. One type of macroscopic non-uniformity, partial shading, was also addressed. The circuit model developed here is a network of diodes, current-sources, and transparent-conductive-oxide (TCO) resistors. An analytic relation between the TCO-resistor, which is the primary model parameter, and TCO sheet resistance rhoS, which is the corresponding physical parameter, was derived. Based on the model several useful general results regarding a uniform cell were deduced. In particular, a global parameter delta, which determines the

  3. Effects of contact-based non-uniformities in cadmium sulfide/cadmium telluride thin-film solar cells

    NASA Astrophysics Data System (ADS)

    Davies, Alan R.

    To strongly contribute to the near-term electricity supply, CdTe-based photovoltaic devices must continue to improve in performance under the constraint of simple and cost efficient fabrication methods. This dissertation focuses on characterization and modeling of devices with non-uniform performance induced by the cell contacts. Devices were obtained from a commercially viable pilot-scale fabrication system at Colorado State University. Current versus voltage (J-V), quantum efficiency (QE) and laser-beam-induced current (LBIC) were the main characterization techniques applied in this work. The p-type CdTe semiconductor has a large work-function and thus tends to form a Schottky barrier when the back-electrode is formed. A common strategy of mitigating the performance-limiting contact barrier is to prepare the CdTe surface with a chemical etch, and include Cu to reduce the effective barrier. Non-uniformity of the etch or Cu inclusion, or insufficient application of Cu can result in a non-uniform contact, with regions of high- and low-energy Schottky barriers participating in the cell performance. Barrier non-uniformities in devices with little or no Cu were identified with the LBIC measurement and a model for their influence was developed and tested using PSpice circuit modeling software. Because of their superstrate configuration, CdTe cells feature front contacts made from transparent-conducting oxides (TCOs). Fluorine-doped tin oxide (F:SnO2) is a common choice because of its availability and acceptable optical and electrical properties. When the n-CdS layer of the CdS/CdTe structure is thinned to encourage greater current generation, non-uniformities of the solar cell junction arise, as CdTe comes into sporadic contact with the TCO layer. Device simulations suggest that the SnO2/CdTe junction is weaker than CdS/CdTe because of a large conduction-band offset induced by the differing electron affinities in the heterojunction. LBIC was used to verify increasing

  4. Design of a Mach-15 Total-Enthalpy Nozzle with Non-Uniform Inflow Using Rotational MOC

    NASA Technical Reports Server (NTRS)

    Gaffney, Richard L., Jr.

    2005-01-01

    A new computer program to design nozzles with non-uniform idow has been developed using the rotational method of characteristics (MOC). This program has been used to design a nozzle for the NASA's HYPULSE shock-expansion tunnel for use in scramjet engine tests at a Mach-15 flight-enthalpy condition. The nozzle has an area ratio of 9.5:l that expands the inflow from Mach 6 along the centerline to Mach 8.7. Although the density and Mach number vary radially at the exit due to the non-uniformities of the inflow, the MOC procedure produces exit flow that is parallel and has uniform static pressure. The design has been verified with CFD which compares favorably with the MOC solution.

  5. ADMIRE: a locally adaptive single-image, non-uniformity correction and denoising algorithm: application to uncooled IR camera

    NASA Astrophysics Data System (ADS)

    Tendero, Y.; Gilles, J.

    2012-06-01

    We propose a new way to correct for the non-uniformity (NU) and the noise in uncooled infrared-type images. This method works on static images, needs no registration, no camera motion and no model for the non uniformity. The proposed method uses an hybrid scheme including an automatic locally-adaptive contrast adjustment and a state-of-the-art image denoising method. It permits to correct for a fully non-linear NU and the noise efficiently using only one image. We compared it with total variation on real raw and simulated NU infrared images. The strength of this approach lies in its simplicity, low computational cost. It needs no test-pattern or calibration and produces no "ghost-artefact".

  6. Design of a Mach-15 Total-Enthalpy Nozzle With Non-uniform Inflow Using Rotational MOC

    NASA Technical Reports Server (NTRS)

    Gaffney, Richard L., Jr.

    2004-01-01

    A new computer program to design nozzles with non-uniform inflow has been developed using the rotational method of characteristics (MOC). This program has been used to design a nozzle for the NASA's HYPULSE shock-expansion tunnel for use in scramjet engine tests at a Mach-15 flight-enthalpy condition. The nozzle has an area ratio of 9.5:1 that expands the inflow from Mach 6 along the centerline to Mach 8.7. Although the density and Mach number vary radially at the exit due to the non-uniformities of the inflow, the MOC procedure produces exit flow that is parallel and has uniform static pressure. The design has been verified with CFD which compares favorably with the MOC solution.

  7. Quantitative recurrence statistics and convergence to an extreme value distribution for non-uniformly hyperbolic dynamical systems

    NASA Astrophysics Data System (ADS)

    Holland, M. P.; Rabassa, P.; Sterk, A. E.

    2016-08-01

    For non-uniformly hyperbolic dynamical systems we consider the time series of maxima along typical orbits. Using ideas based upon quantitative recurrence time statistics we prove convergence of the maxima (under suitable normalization) to an extreme value distribution, and obtain estimates on the rate of convergence. We show that our results are applicable to a range of examples, and include new results for Lorenz maps, certain partially hyperbolic systems, and non-uniformly expanding systems with sub-exponential decay of correlations. For applications where analytic results are not readily available we show how to estimate the rate of convergence to an extreme value distribution based upon numerical information of the quantitative recurrence statistics. We envisage that such information will lead to more efficient statistical parameter estimation schemes based upon the block-maxima method.

  8. An efficient closed-form design method for nearly perfect reconstruction of non-uniform filter bank.

    PubMed

    Kumar, A; Pooja, R; Singh, G K

    2016-03-01

    In this paper, an efficient closed form method for the design of multi-channel nearly perfect reconstruction of non-uniform filter bank with the prescribed stopband attenuation and channel overlapping is presented. In this method, the design problem of multi-channel non-uniform filter bank (NUFB) is considered as the design of a prototype filter whose magnitude response at quadrature frequency is 0.707, which is exploited for finding the optimum passband edge frequency through empirical formula instead of using single or multivariable optimization technique. Two main attributes used in assessing the performance of filter bank are peak reconstruction error (PRE) and computational time (CPU time). As compared to existing methods, this method is very simple and easy to implement for NUFBs. To implement this algorithm, a Matlab program has been developed, and several examples are presented to illustrate the performance of proposed method. PMID:26861726

  9. Recovering the pollutant release history in aquifers with non uniform flow field.

    NASA Astrophysics Data System (ADS)

    Zanini, A.; Butera, I.; Tanda, M.

    2005-12-01

    The great interest in environmental issues has led to an attention to the quality of groundwater. Scientific efforts in groundwater flow studies have primarily focused on the flow and transport behavior and on the identification of the corresponding parameters. Since '90 increasing attention has been paid to the problem of recovering the release history of a pollutant because the knowledge of the pollution injection function gives information about the future pollution spread and allows a better planning of remediation action (Liu and Ball, 1999, Snodgrass and Kitanidis, 1997, Skaggs and Kabala, 1994, Butera and Tanda, 2003). Moreover, from a legal and regulatory point of view, it is also important to determine the release time period and the highest values of concentration released; in fact, an available release history can be a useful tool for sharing the costs of remediation of a polluted area among the actors. Some approaches developed in the literature to the inverse problem solution (geostatistical approach (Snodgrass and Kitanidis, 1997), Tikhonov regularization method (Skaggs and Kabala, 1994)) require the computation of the function that describes the effect, in time at a certain location of the aquifer, due to an impulsive release of pollutant at the source. This function, named transfer or Kernel function can be analy1itically determined if the problem has a simple geometry and regular boundary conditions. In many cases the characteristic of the groundwater flow field do not allow for the analytical transfer function formulation; this is the case, for instance, of non uniform in the mean flow due to complicated boundary conditions, existence of pumping wells, high heterogeneity of the aquifer (Sudicky, 1986) etc.. With the available procedures the technician has to reduce the real problem to a very simplified scheme to which the analytical transfer function can be applied. As a consequence a rough approximation in the results can be expected. In this

  10. Time-lapse Monitoring of Two-dimensional Non-uniform Unsaturated Flow Processes Using Ground Penetrating Radar

    NASA Astrophysics Data System (ADS)

    Lytle, B. A.; Mangel, A. R.; Moysey, S. M.

    2015-12-01

    Unsaturated flow in the vadose zone often manifests as preferential flow resulting in transport of water and solutes through the soil much faster than would occur for uniform matrix flow. Time-lapse ground-penetrating radar (GPR) monitoring shows significant potential for identifying the presence of non-uniform flow and quantitative monitoring of the hydrologic response of a soil system. We investigate non-uniform flow in the vadose zone for an infiltration experiment performed in a 60 cm deep sand-filled tank that is continuously monitored with 1000 MHz reflection GPR. During the experiment, 100 constant offset and 300 common mid-point (CMP) time-lapse radar profiles were collected using an automated gantry system to rapidly position the antennas, allowing for a set of 1 constant offset and 3 CMP profiles to be collected every 13 seconds. The constant offset profiles were interpreted to evaluate spatial and temporal changes of reflected arrivals over the course of the experiment, whereas the CMPs were used to estimate the initial EM wave velocity in the tanks using a normal moveout analysis. Changes in traveltime to a static reflector were used to estimate spatial changes in velocity and to create two-dimensional velocity models. The GPR data were then migrated using the estimated 2D velocity model to improve GPR reflection images, which could then be interpreted to identify evidence of non-uniform flow phenomena. To verify the approach, the methodology was also applied to GPR data simulated using transient water contents generated by the unsaturated flow simulator HYDRUS2D given lab-measured hydraulic properties for the soil. For both the empirical and simulated data, we found that the 2D velocity analysis was effective in monitoring changes in the wetting front and that migration of the reflection profiles was able to improve the interpretation of non-uniform flow.

  11. An automatic generation of non-uniform mesh for CFD analyses of image-based multiscale human airway models

    NASA Astrophysics Data System (ADS)

    Miyawaki, Shinjiro; Tawhai, Merryn H.; Hoffman, Eric A.; Lin, Ching-Long

    2014-11-01

    The authors have developed a method to automatically generate non-uniform CFD mesh for image-based human airway models. The sizes of generated tetrahedral elements vary in both radial and longitudinal directions to account for boundary layer and multiscale nature of pulmonary airflow. The proposed method takes advantage of our previously developed centerline-based geometry reconstruction method. In order to generate the mesh branch by branch in parallel, we used the open-source programs Gmsh and TetGen for surface and volume meshes, respectively. Both programs can specify element sizes by means of background mesh. The size of an arbitrary element in the domain is a function of wall distance, element size on the wall, and element size at the center of airway lumen. The element sizes on the wall are computed based on local flow rate and airway diameter. The total number of elements in the non-uniform mesh (10 M) was about half of that in the uniform mesh, although the computational time for the non-uniform mesh was about twice longer (170 min). The proposed method generates CFD meshes with fine elements near the wall and smooth variation of element size in longitudinal direction, which are required, e.g., for simulations with high flow rate. NIH Grants R01-HL094315, U01-HL114494, and S10-RR022421. Computer time provided by XSEDE.

  12. Intelligibility of time-compressed speech: the effect of uniform versus non-uniform time-compression algorithms.

    PubMed

    Schlueter, Anne; Lemke, Ulrike; Kollmeier, Birger; Holube, Inga

    2014-03-01

    For assessing hearing aid algorithms, a method is sought to shift the threshold of a speech-in-noise test to (mostly positive) signal-to-noise ratios (SNRs) that allow discrimination across algorithmic settings and are most relevant for hearing-impaired listeners in daily life. Hence, time-compressed speech with higher speech rates was evaluated to parametrically increase the difficulty of the test while preserving most of the relevant acoustical speech cues. A uniform and a non-uniform algorithm were used to compress the sentences of the German Oldenburg Sentence Test at different speech rates. In comparison, the non-uniform algorithm exhibited greater deviations from the targeted time compression, as well as greater changes of the phoneme duration, spectra, and modulation spectra. Speech intelligibility for fast Oldenburg sentences in background noise at different SNRs was determined with 48 normal-hearing listeners. The results confirmed decreasing intelligibility with increasing speech rate. Speech had to be compressed to more than 30% of its original length to reach 50% intelligibility at positive SNRs. Characteristics influencing the discrimination ability of the test for assessing effective SNR changes were investigated. Subjective and objective measures indicated a clear advantage of the uniform algorithm in comparison to the non-uniform algorithm for the application in speech-in-noise tests. PMID:24606289

  13. Visualization of non-uniform current flow in coated conductors by scanning Hall-probe magnetic microscopy

    NASA Astrophysics Data System (ADS)

    Abiru, K.; Honda, Y.; Inoue, M.; Kiss, T.; Iijima, Y.; Kakimoto, K.; Saitoh, T.; Nakao, K.; Shiohara, Y.

    2009-10-01

    We have visualized non-uniform current flow in RE123 coated conductors by using a scanning Hall-probe magnetic microscopy (SHPM). Newly developed SHPM system allows us to measure two-dimensional magnetic field distribution with high spatial resolution in micro-meter scale. Corresponding current density distribution can be obtained from the magnetic field image by solving inverted Biot-Savart’s law. One of the most important advantages of the present system is to visualize the current density distribution in practical high transport current and also in wide scanning area. For example, the system has current leads with large capacity up to 500 A, and the operating distance can be 15 cm by 15 cm with a micro-meter step distance. Using the SHPM system, we have successfully visualized current density distributions in the coated conductor, and clarified different kinds of non-uniform current flow. Those insights are very useful to identify local defects as well as non-uniform tape quality. These results indicate that the SHPM system is a powerful diagnostic tool not only to observe spatial inhomogeneities of transport property but also to understand their reason in practical coated conductors.

  14. A polynomial chaos approach to narrow band modeling of radiative heat transfer in non-uniform gaseous media

    NASA Astrophysics Data System (ADS)

    André, Frédéric

    2016-05-01

    An accurate treatment of non-uniformities is required in many applications involving radiative heat transfer in gaseous media. Usual techniques to handle path non-uniformities rely on simplifying assumptions, such as scaling or correlation of gas spectra. Those approximations are usually accurate but may also fail to provide accurate results, especially when large temperature gradients are considered. The objective of the present work is to show that this problem can be treated rigorously. The proposed method can be applied to any arbitrary narrow band model. It is based on some results from Polynomial Chaos' framework and copulas theory. Although the mathematical derivation may appear sophisticated, applying the method is straightforward. It is shown that adding only one coefficient to any uniform narrow band model (for a simple case involving a non-uniform column discretized into two uniform sub-paths) allows to achieve almost LBL accuracy for radiative heat transfer calculations. The technique is described and applied to some "severe" test cases from the literature.

  15. One-step fabrication of nanostructure-covered microstructures using selective aluminum anodization based on non-uniform electric field

    NASA Astrophysics Data System (ADS)

    Park, Yong Min; Kim, Byeong Hee; Seo, Young Ho

    2016-06-01

    This paper presents a selective aluminum anodization technique for the fabrication of microstructures covered by nanoscale dome structures. It is possible to fabricate bulging microstructures, utilizing the different growth rates of anodic aluminum oxide in non-uniform electric fields, because the growth rate of anodic aluminum oxide depends on the intensity of electric field, or current density. After anodizing under a non-uniform electric field, bulging microstructures covered by nanostructures were fabricated by removing the residual aluminum layer. The non-uniform electric field induced by insulative micropatterns was estimated by computational simulations and verified experimentally. Utilizing computational simulations, the intensity profile of the electric field was calculated according to the ratio of height and width of the insulative micropatterns. To compare computational simulation results and experimental results, insulative micropatterns were fabricated using SU-8 photoresist. The results verified that the shape of the bottom topology of anodic alumina was strongly dependent on the intensity profile of the applied electric field, or current density. The one-step fabrication of nanostructure-covered microstructures can be applied to various fields, such as nano-biochip and nano-optics, owing to its simplicity and cost effectiveness.

  16. Receptivity of flat-plate boundary layer in a non-uniform free stream (vorticity normal to the plate)

    NASA Technical Reports Server (NTRS)

    Kogan, M. N.

    1994-01-01

    Recent progress in both the linear and nonlinear aspects of stability theory has highlighted the importance of the receptivity problem. One of the most unclear aspects of receptivity study is the receptivity of boundary-layer flow normal to vortical disturbances. Some experimental and theoretical results permit the proposition that quasi-steady outer-flow vortical disturbances may trigger by-pass transition. In present work such interaction is investigated for vorticity normal to a leading edge. The interest in these types of vortical disturbances arise from theoretical work, where it was shown that small sinusoidal variations of upstream velocity along the spanwise direction can produce significant variations in the boundary-layer profile. In the experimental part of this work, such non-uniform flow was created and the laminar-turbulent transition in this flow was investigated. The experiment was carried out in a low-turbulence direct-flow wind tunnel T-361 at the Central Aerohydrodynamic Institute (TsAGI). The non-uniform flow was produced by laminar or turbulent wakes behind a wire placed normal to the plate upstream of the leading edge. The theoretical part of the work is devoted to studying the unstable disturbance evolution in a boundary layer with strongly non-uniform velocity profiles similar to that produced by outer-flow vorticity. Specifically, the Tollmien-Schlichting wave development in the boundary layer flow with spanwise variations of velocity is investigated.

  17. Effects of non-uniform windowing in a Rician-fading channel and simulation of adaptive automatic repeat request protocols

    NASA Astrophysics Data System (ADS)

    Kmiecik, Chris G.

    1990-06-01

    Two aspects of digital communication were investigated. In the first part, a Fast Fourier Transformation (FFT) based, M-ary frequency shift keying (FSK) receiver in a Rician-fading channel was analyzed to determine the benefits of non-uniform windowing of sampled received data. When a frequency offset occurs, non-uniform windowing provided better FFT magnitude separation. The improved dynamic range was balanced against a loss in detectability due to signal attenuation. With large frequency offset, the improved magnitude separation outweighed the loss in detectability. An analysis was carried out to determine what frequency deviation is necessary for non-uniform windowing to out-perform uniform windowing in a slow Rician-fading channel. Having established typical values of probability of bit errors, the second part of this thesis looked at improving throughput in a digital communications network by applying adaptive automatic repeat request (ARQ) protocols. The results of simulations of adaptive ARQ protocols with variable frame lengths is presented. By varying the frame length, improved throughput performance through all bit error rates was achieved.

  18. GPU-accelerated non-uniform fast Fourier transform-based compressive sensing spectral domain optical coherence tomography.

    PubMed

    Xu, Daguang; Huang, Yong; Kang, Jin U

    2014-06-16

    We implemented the graphics processing unit (GPU) accelerated compressive sensing (CS) non-uniform in k-space spectral domain optical coherence tomography (SD OCT). Kaiser-Bessel (KB) function and Gaussian function are used independently as the convolution kernel in the gridding-based non-uniform fast Fourier transform (NUFFT) algorithm with different oversampling ratios and kernel widths. Our implementation is compared with the GPU-accelerated modified non-uniform discrete Fourier transform (MNUDFT) matrix-based CS SD OCT and the GPU-accelerated fast Fourier transform (FFT)-based CS SD OCT. It was found that our implementation has comparable performance to the GPU-accelerated MNUDFT-based CS SD OCT in terms of image quality while providing more than 5 times speed enhancement. When compared to the GPU-accelerated FFT based-CS SD OCT, it shows smaller background noise and less side lobes while eliminating the need for the cumbersome k-space grid filling and the k-linear calibration procedure. Finally, we demonstrated that by using a conventional desktop computer architecture having three GPUs, real-time B-mode imaging can be obtained in excess of 30 fps for the GPU-accelerated NUFFT based CS SD OCT with frame size 2048(axial) × 1,000(lateral). PMID:24977582

  19. GPU-accelerated non-uniform fast Fourier transform-based compressive sensing spectral domain optical coherence tomography

    PubMed Central

    Xu, Daguang; Huang, Yong; Kang, Jin U.

    2014-01-01

    We implemented the graphics processing unit (GPU) accelerated compressive sensing (CS) non-uniform in k-space spectral domain optical coherence tomography (SD OCT). Kaiser-Bessel (KB) function and Gaussian function are used independently as the convolution kernel in the gridding-based non-uniform fast Fourier transform (NUFFT) algorithm with different oversampling ratios and kernel widths. Our implementation is compared with the GPU-accelerated modified non-uniform discrete Fourier transform (MNUDFT) matrix-based CS SD OCT and the GPU-accelerated fast Fourier transform (FFT)-based CS SD OCT. It was found that our implementation has comparable performance to the GPU-accelerated MNUDFT-based CS SD OCT in terms of image quality while providing more than 5 times speed enhancement. When compared to the GPU-accelerated FFT based-CS SD OCT, it shows smaller background noise and less side lobes while eliminating the need for the cumbersome k-space grid filling and the k-linear calibration procedure. Finally, we demonstrated that by using a conventional desktop computer architecture having three GPUs, real-time B-mode imaging can be obtained in excess of 30 fps for the GPU-accelerated NUFFT based CS SD OCT with frame size 2048(axial)×1000(lateral). PMID:24977582

  20. Carbon Monoxide Toxicity

    PubMed Central

    Aniol, Michael J.

    1992-01-01

    Of all fatal poisonings in the United States, an estimated half are due to carbon monoxide. The number of non-lethal poisonings due to carbon monoxide is difficult to estimate because signs and symptoms of carbon monoxide poisoning cover a wide spectrum and mimic other disorders. Misdiagnosis is serious, as the patient often returns to the contaminated environment. Those not receiving proper treatment are at significant risk, as high as 10% to 12%, of developing late neurological sequelae. The diagnosis of carbon monoxide poisoning depends upon precise history taking, careful physical examination, and a high index of suspicion. ImagesFigure 2 PMID:21221282

  1. Non-uniform thickness in Europa's icy shell: implications for astrobiology mission design

    NASA Astrophysics Data System (ADS)

    Fairén, A.; Amils, R.

    zero shell thickness [12]) with liquid water at shallow depths [5], allowing for bolide penetration, diapirism and the extrusion of water to the surface. The heterogeneity in shell's thickness may be originated in spatial variations in tidal heating [13] and/or warm water upwellings from the silicate interior capable of melt-through the ice from below [12,14]. This thickness heterogeneity can be embedded in a general equatorward thickening trending, due to tidal dissipation and surface temperature variations [15]. A major constraint must be addressed at this point: the dynamism of ductile ice near the base of the shell may drive to decay in lateral thickness contrasts. But this effect has been examined both assuming ice as a Newtonian [16,17,18] and a non-Newtonian material [19], broadly reaching to similar conclusions: global shell thickness variations may survive for up to 100 Myr. In addition, lateral pressure gradients may not decay if they comprise only shallow depths [19]. Therefore, our results point to a dynamic non-uniform Europa's icy shell, displaying some regional and temporal heterogeneity in thickness. As thin/thick ice distribution is as time dependent as the surface ice features are (both are reshaped in periods ˜ 100 Myr), the analysis performed here offers an estimation of the current thickness distribution in the ice shell, estimation that cannot be extrapolated to ancient (e.g., >100 Myr) times. The astrobiological potential the shell and ocean below possess is highlighted by these results: a somewhere thin outer crust allows the possibility for some exogenous materials delivered by asteroids and comets to reach the inner liquid water ocean by breaching the brittle lithosphere [20], and so join to those generated in the interior of Europa via volcanic and hydrothermal activity [21]. In addition, pressure gradients driving the ductile ice at the base of the shell to flow laterally may help to redistribute such materials among the inner ice shell and

  2. Dynamic equilibria and magnetohydrodynamic instabilities in toroidal plasmas with non-uniform transport coefficients

    SciTech Connect

    Futatani, Shimpei; Bos, Wouter J. T.; Morales, Jorge A.

    2015-05-15

    It can be shown that in the presence of a toroidal magnetic field induced by poloidal coils, combined with the electromagnetic field induced by a central solenoid, no static equilibrium is possible within the MHD description, as soon as non-zero resistivity is assumed. The resulting dynamic equilibrium was previously discussed for the case of spatially homogeneous resisitivity. In the present work, it is shown how a spatial inhomogeneity of the viscosity and resisitivity coefficients influences this equilibrium. Parameters in both the stable, tokamak-like regime and unstable, reversed field pinch-like regime are considered. It is shown that, whereas the magnitudes of the velocity and magnetic field fluctuations are strongly modified by the spatial variation of the transport coefficients, the qualitative flow behaviour remains largely unaffected.

  3. Characterization and modeling of two-phase heat transfer in chip-scale non-uniformly heated microgap channels

    NASA Astrophysics Data System (ADS)

    Ali, Ihab A.

    A chip-scale, non-uniformly heated microgap channel, 100 micron to 500 micron in height with dielectric fluid HFE-7100 providing direct single- and two-phase liquid cooling for a thermal test chip with localized heat flux reaching 100 W/cm2, is experimentally characterized and numerically modeled. Single-phase heat transfer and hydraulic characterization is performed to establish the single-phase baseline performance of the microgap channel and to validate the mesh-intensive CFD numerical model developed for the test channel. Convective heat transfer coefficients for HFE-7100 flowing in a 100-micron microgap channel reached 9 kW/m2K at 6.5 m/s fluid velocity. Despite the highly non-uniform boundary conditions imposed on the microgap channel, CFD model simulation gave excellent agreement with the experimental data (to within 5%), while the discrepancy with the predictions of the classical, "ideal" channel correlations in the literature reached 20%. A detailed investigation of two-phase heat transfer in non-ideal micro gap channels, with developing flow and significant non-uniformities in heat generation, was performed. Significant temperature non-uniformities were observed with non-uniform heating, where the wall temperature gradient exceeded 30°C with a heat flux gradient of 3-30 W/cm2, for the quadrant-die heating pattern compared to a 20°C gradient and 7-14 W/cm2 heat flux gradient for the uniform heating pattern, at 25W heat and 1500 kg/m2s mass flux. Using an inverse computation technique for determining the heat flow into the wetted microgap channel, average wall heat transfer coefficients were found to vary in a complex fashion with channel height, flow rate, heat flux, and heating pattern and to typically display an inverse parabolic segment of a previously observed M-shaped variation with quality, for two-phase thermal transport. Examination of heat transfer coefficients sorted by flow regimes yielded an overall agreement of 31% between predictions of the

  4. Avoiding symmetry-breaking spatial non-uniformity in deformable image registration via a quasi-volume-preserving constraint.

    PubMed

    Aganj, Iman; Reuter, Martin; Sabuncu, Mert R; Fischl, Bruce

    2015-02-01

    The choice of a reference image typically influences the results of deformable image registration, thereby making it asymmetric. This is a consequence of a spatially non-uniform weighting in the cost function integral that leads to general registration inaccuracy. The inhomogeneous integral measure--which is the local volume change in the transformation, thus varying through the course of the registration--causes image regions to contribute differently to the objective function. More importantly, the optimization algorithm is allowed to minimize the cost function by manipulating the volume change, instead of aligning the images. The approaches that restore symmetry to deformable registration successfully achieve inverse-consistency, but do not eliminate the regional bias that is the source of the error. In this work, we address the root of the problem: the non-uniformity of the cost function integral. We introduce a new quasi-volume-preserving constraint that allows for volume change only in areas with well-matching image intensities, and show that such a constraint puts a bound on the error arising from spatial non-uniformity. We demonstrate the advantages of adding the proposed constraint to standard (asymmetric and symmetrized) demons and diffeomorphic demons algorithms through experiments on synthetic images, and real X-ray and 2D/3D brain MRI data. Specifically, the results show that our approach leads to image alignment with more accurate matching of manually defined neuroanatomical structures, better tradeoff between image intensity matching and registration-induced distortion, improved native symmetry, and lower susceptibility to local optima. In summary, the inclusion of this space- and time-varying constraint leads to better image registration along every dimension that we have measured it. PMID:25449738

  5. Effects of non-uniform stiffness on the swimming performance of a passively-flexing, fish-like foil model.

    PubMed

    Lucas, Kelsey N; Thornycroft, Patrick J M; Gemmell, Brad J; Colin, Sean P; Costello, John H; Lauder, George V

    2015-10-01

    Simple mechanical models emulating fish have been used recently to enable targeted study of individual factors contributing to swimming locomotion without the confounding complexity of the whole fish body. Yet, unlike these uniform models, the fish body is notable for its non-uniform material properties. In particular, flexural stiffness decreases along the fish's anterior-posterior axis. To identify the role of non-uniform bending stiffness during fish-like propulsion, we studied four foil model configurations made by adhering layers of plastic sheets to produce discrete regions of high (5.5 × 10(-5) Nm(2)) and low (1.9 × 10(-5) Nm(2)) flexural stiffness of biologically-relevant magnitudes. This resulted in two uniform control foils and two foils with anterior regions of high stiffness and posterior regions of low stiffness. With a mechanical flapping foil controller, we measured forces and torques in three directions and quantified swimming performance under both heaving (no pitch) and constant 0° angle of attack programs. Foils self-propelled at Reynolds number 21 000-115 000 and Strouhal number ∼0.20-0.25, values characteristic of fish locomotion. Although previous models have emphasized uniform distributions and heaving motions, the combination of non-uniform stiffness distributions and 0° angle of attack pitching program was better able to reproduce the kinematics of freely-swimming fish. This combination was likewise crucial in maximizing swimming performance and resulted in high self-propelled speeds at low costs of transport and large thrust coefficients at relatively high efficiency. Because these metrics were not all maximized together, selection of the 'best' stiffness distribution will depend on actuation constraints and performance goals. These improved models enable more detailed, accurate analyses of fish-like swimming. PMID:26447541

  6. Ferrofluid flow due to a rotating disk in the presence of a non-uniform magnetic field

    NASA Astrophysics Data System (ADS)

    Bhandari, A.; Kumar, V.

    2016-05-01

    The flow of a ferrofluid due to a rotating disk in the presence of a non-uniform magnetic field in the axial direction is studied through mathematical modeling of the problem. Contour and surface plots in the presence of 10 kilo-ampere/meter, 100 kilo-ampere/meter magnetization force are presented here for radial, tangential and axial velocity profiles, and results are also drawn for the magnetic field intensity. These results are compared with the ordinary case where magnetization force is absent.

  7. Denoising Algorithm for the Pixel-Response Non-Uniformity Correction of a Scientific CMOS Under Low Light Conditions

    NASA Astrophysics Data System (ADS)

    Hu, Changmiao; Bai, Yang; Tang, Ping

    2016-06-01

    We present a denoising algorithm for the pixel-response non-uniformity correction of a scientific complementary metal-oxide-semiconductor (CMOS) image sensor, which captures images under extremely low-light conditions. By analyzing the integrating sphere experimental data, we present a pixel-by-pixel flat-field denoising algorithm to remove this fixed pattern noise, which occur in low-light conditions and high pixel response readouts. The response of the CMOS image sensor imaging system to the uniform radiance field shows a high level of spatial uniformity after the denoising algorithm has been applied.

  8. Evaluation of the impact of non-uniform neutron radiation fields on the dose received by glove box radiation workers

    NASA Astrophysics Data System (ADS)

    Crawford, Arthur Bryan

    The effort to estimate the radiation dose received by an occupationally exposed worker is a complex task. Regulatory guidance assumes that the stochastic risks from uniform and non-uniform whole-body irradiations are equal. An ideal uniform irradiation of the whole body would require a broad parallel radiation field of relatively high-energy radiation, which many occupationally exposed workers do not experience. In reality, workers are exposed to a non-uniform irradiation of the whole body such as a radiation field with one or more types of radiation, each with varying energies and/or fluence rates, incident on the worker. Most occupational radiation exposure at LANL is due to neutron radiation. Many of these exposures originate from activities performed in glove boxes with nuclear materials. A standard Los Alamos 2 x 2 x 2 glove box is modeled with the source material being clean weapons grade plutonium. Dosimeter tally planes were modeled to stimulate the various positions that a dosimeter can be worn. An anthropomorphic phantom was used to determine whole body dose. Various geometries of source position and phantom location were used to determine the effects of streaming on the radiation dose a worker may receive. Based on computational and experimental results, the effects of a non-uniform radiation field have on radiation dose received by a worker in a glove box environment are: (1) Dosimeter worn at chest level can overestimate the whole body dose between a factor of two to six depending on location of the phantom with the source material close to the front of the glove box, (2) Dosimeter should be worn at waist level instead of chest level to more accurately reflect the whole body dose received, (3) Dose can be significantly higher for specific locations of the worker relative to the position of the source, (4) On the average the testes contribute almost 44% of the whole body dose for a male, and (5) Appropriate design considerations such as more shielding

  9. FM Reconstruction of Non-Uniformly Sampled Protein NMR Data at Higher Dimensions and Optimization by Distillation

    PubMed Central

    Hyberts, Sven G.; Frueh, Dominique P.; Arthanari, Haribabu; Wagner, Gerhard

    2010-01-01

    Non-uniform sampling (NUS) enables recording of multidimensional NMR data at resolutions matching the resolving power of modern instruments without using excessive measuring time. However, in order to obtain satisfying results, efficient reconstruction methods are needed. Here we describe an optimized version of the Forward Maximum entropy (FM) reconstruction method, which can reconstruct up to three indirect dimensions. For complex datasets, such as NOESY spectra, the performance of the procedure is enhanced by a distillation procedure that reduces artifacts stemming from intense peaks. PMID:19705283

  10. Harmonically mode-locked femtosecond fiber laser using non-uniform, WS2-particle deposited side-polished fiber

    NASA Astrophysics Data System (ADS)

    Lee, Junsu; Park, June; Koo, Joonhoi; Jhon, Young Min; Lee, Ju Han

    2016-03-01

    We investigated the feasibility of using a WS2-deposited side-polished fiber as a harmonic mode-locker to produce a femtosecond fiber laser with a frequency of 1.51 GHz. Our work focuses on using a side-polished fiber platform with non-uniform WS2 particles prepared through liquid phase exfoliation method without centrifugation. Femtosecond optical pulses were generated from an all-fiberized erbium-doped fiber-based ring cavity by increasing the pump power to achieve a tunable pulse repetition rate from 14.57 MHz to 1.51 GHz (104th harmonic). The characteristics of the output pulse were systematically investigated to analyze the pulse repetition rate, harmonic order, average output power, pulse energy, and pulse width as a function of the pump power. The output performance of the laser was compared to that of a laser based on a microfiber-based WS2 film SA described in (Yan et al 2015 Opt. Mater. Express 5 479-89). This experimental demonstration reaffirms that a side-polished fiber is an effective platform to implement an ultrafast harmonic mode-locker, and non-uniform WS2 particles prepared via simple liquid phase exfoliation method without centrifugation provide a suitable saturable absorption response at 1.55 μm.

  11. Locally non-uniform finite-difference time domain with application to stealth, crosstalk, and narrow apertures

    NASA Astrophysics Data System (ADS)

    Riley, D. J.

    1993-04-01

    A technique to integrate a dense, locally non-uniform mesh into finite-difference time-domain (FDTD) codes is presented. The method is designed for the full-wave analysis of multi-material layers that are physically thin, but perhaps electrically thick. Such layers are often used for the purpose of suppressing electromagnetic reflections from conducting surfaces. Throughout the non-uniform local mesh, average values for the conductivity and permittivity are used, where as variations in permeability are accommodated by splitting H-field line integrals and enforcing continuity of the normal B field. A unique interpolation scheme provides accuracy and late-time stability for mesh discontinuities as large as 1000 to 1. Application is made to resistive sheets, the absorbing Salisbury screen, crosstalk on printed circuit boards, and apertures that are narrow both in width and depth with regard to a uniform cell. Where appropriate, comparisons are made with the MoM code CARLOS and transmission-line theory. The hybrid mesh formulation has been highly optimized for both vector and parallel-processing on Cray Y-MP architectures.

  12. Analysis of hysteresis effect on the vibration motion of a bimodal non-uniform micro-cantilever using MCS theory

    NASA Astrophysics Data System (ADS)

    Korayem, M. H.; Korayem, A. H.; Hosseini Hashemi, Sh.

    2016-02-01

    Nowadays, to enhance the performance of atomic force microscopy (AFM) micro-cantilevers (MCs) during imaging, reduce costs and increase the surface topography precision, advanced MCs equipped with piezoelectric layers are utilized. Using the modified couple stress (MCS) theory not only makes the modeling more exhaustive, but also increases the accuracy of prediction of the vibration behavior of the system. In this paper, Hamilton's principle by consideration of the MCS theory has been used to extract the equations. In addition, to discretize the equations, differential quadrature method has been adopted. Analysis of the hysteresis effect on the vibration behavior of the AFM MC is of significant importance. Thus, to model the hysteresis effect, Bouc-Wen method, which is solved simultaneously with the vibration equations of non-uniform Timoshenko beam, has been utilized. Furthermore, a bimodal excitation of the MC has been considered. The results reveal that the hysteresis effect appears as a phase difference in the time response. Finally, the effect of the geometric parameters on the vibration frequency of the system which is excited by combination of the first two vibration modes of the non-uniform piezoelectric MC has been examined. The results indicate the considerable effect of the MC length in comparison with other geometric parameters such as the MC width and thickness.

  13. Modified Zakharov-Kuznetsov equation for a non-uniform electron-positron-ion magnetoplasma with kappa-distributed electrons

    NASA Astrophysics Data System (ADS)

    Ahmad, Ali; Masood, W.

    2015-10-01

    > We investigate the low-frequency (by comparison with the ion Larmor frequency) electrostatic solitary structures in a spatially non-uniform electron-positron-ion (e-p-i) magnetoplasma with non-Maxwellian electrons. A linear dispersion relation for the obliquely propagating ion acoustic drift wave is derived and it is shown that the non-Maxwellian electron population modifies the dispersion characteristics of the wave under consideration. We also carry out a nonlinear analysis and derive the modified Zakharov-Kuznetsov (MZK) equation for the coupled drift acoustic wave in a non-uniform magnetized plasma. We highlight the differences between the MZK equation and its homogeneous counterpart. We also find the solution of the MZK equation using the tangent hyperbolic method. It is observed that the electron spectral index , positron concentration, and propagation angle alter the structure of the ion acoustic drift solitary waves. The results obtained in this paper may be beneficial to understanding the propagation characteristics of electrostatic drift solitary structures in the interstellar medium and in laboratory experiments where electron-positron plasmas have recently been created by impinging ultra-intense laser pulses on a solid density target at the Lawrence Livermore National Laboratory (LLNL).

  14. Renovascular effects of neuropeptide-Y in the split hydronephrotic rat kidney: non-uniform pattern of vascular reactivity.

    PubMed Central

    Dietrich, M S; Fretschner, M; Nobiling, R; Persson, P B; Steinhausen, M

    1991-01-01

    1. The renovascular effects of neuropeptide-Y (NPY) were examined in the split hydronephrotic rat kidney. 2. Systemic infusion of low non-pressor doses of NPY (0.2 micrograms kg-1 up to 5.0 micrograms kg-1) produced a non-uniform pattern of vascular reactivity. In general, a significant constriction of the proximal and distal arcuate artery was seen at all doses. No constriction was seen at the interlobular artery or the larger part of the afferent arteriole. These segments initially dilated during the lower dose infusions. The very distal part of the afferent arteriole adjacent to the glomerulus and the proximal efferent arteriole responded in a similar way to the arcuate arteries. 3. NPY, locally applied into the tissue bath at concentrations of 1 nmol l-1 up to 25 nmol l-1, produced non-uniform vascular reactions similar to those of intravenously infused NPY. At the considerably higher local dosage of 1.14 mumol l-1, all vascular segments revealed vasoconstriction. 4. NPY application did not attenuate effects of acetylcholine. This observation suggests that the mechanism of NPY-induced vasoconstriction does not rely upon antagonism of endothelium-derived vasodilatation. 5. The pattern of vascular reactivity to NPY was substantially different from that known for the vasoconstrictors noradrenaline and angiotensin II in our preparation. PMID:1822552

  15. The effect of non-uniform mass loading on the linear, temporal development of particle-laden shear layers

    SciTech Connect

    Senatore, Giacomo; Davis, Sean; Jacobs, Gustaaf

    2015-03-15

    The effect of non-uniformity in bulk particle mass loading on the linear development of a particle-laden shear layer is analyzed by means of a stochastic Eulerian-Eulerian model. From the set of governing equations of the two-fluid model, a modified Rayleigh equation is derived that governs the linear growth of a spatially periodic disturbance. Eigenvalues for this Rayleigh equation are determined numerically using proper conditions at the co-flowing gas and particle interface locations. For the first time, it is shown that non-uniform loading of small-inertia particles (Stokes number (St) <0.2) may destabilize the inviscid mixing layer development as compared to the pure-gas flow. The destabilization is triggered by an energy transfer rate that globally flows from the particle phase to the gas phase. For intermediate St (1 < St < 10), a maximum stabilizing effect is computed, while at larger St, two unstable modes may coexist. The growth rate computations from linear stability analysis are verified numerically through simulations based on an Eulerian-Lagrangian (EL) model based on the inviscid Euler equations and a point particle model. The growth rates found in numerical experiments using the EL method are in very good agreement with growth rates from the linear stability analysis and validate the destabilizing effect induced by the presence of particles with low St.

  16. Locally non-uniform finite-difference time domain with application to stealth, crosstalk, and narrow apertures

    SciTech Connect

    Riley, D.J.

    1993-04-01

    A technique to integrate a dense, locally non-uniform mesh into finite-difference time-domain (FDTD) codes is presented. The method is designed for the full-wave analysis of multi-material layers that are physically thin, but perhaps electrically thick. Such layers are often used for the purpose of suppressing electromagnetic reflections from conducting surfaces. Throughout the non-uniform local mesh, average values for the conductivity and permittivity are used, where as variations in permeability are accommodated by splitting H-field line integrals and enforcing continuity of the normal B field. A unique interpolation scheme provides accuracy and late-time stability for mesh discontinuities as large as 1000 to 1. Application is made to resistive sheets, the absorbing Salisbury screen, crosstalk on printed circuit boards, and apertures that are narrow both in width and depth with regard to a uniform cell. Where appropriate, comparisons are made with the MoM code CARLOS and transmission-line theory. The hybrid mesh formulation has been highly optimized for both vector and parallel-processing on Cray YMP architectures.

  17. Design of multiplier-less sharp transition width non-uniform filter banks using gravitational search algorithm

    NASA Astrophysics Data System (ADS)

    Bindiya T., S.; Elias, Elizabeth

    2015-01-01

    In this paper, multiplier-less near-perfect reconstruction tree-structured filter banks are proposed. Filters with sharp transition width are preferred in filter banks in order to reduce the aliasing between adjacent channels. When sharp transition width filters are designed as conventional finite impulse response filters, the order of the filters will become very high leading to increased complexity. The frequency response masking (FRM) method is known to result in linear-phase sharp transition width filters with low complexity. It is found that the proposed design method, which is based on FRM, gives better results compared to the earlier reported results, in terms of the number of multipliers when sharp transition width filter banks are needed. To further reduce the complexity and power consumption, the tree-structured filter bank is made totally multiplier-less by converting the continuous filter bank coefficients to finite precision coefficients in the signed power of two space. This may lead to performance degradation and calls for the use of a suitable optimisation technique. In this paper, gravitational search algorithm is proposed to be used in the design of the multiplier-less tree-structured uniform as well as non-uniform filter banks. This design method results in uniform and non-uniform filter banks which are simple, alias-free, linear phase and multiplier-less and have sharp transition width.

  18. Guiding-centre transformation of the radiation-reaction force in a non-uniform magnetic field

    NASA Astrophysics Data System (ADS)

    Hirvijoki, E.; Decker, J.; Brizard, A. J.; Embréus, O.

    2015-10-01

    > In this paper, we present the guiding-centre transformation of the radiation-reaction force of a classical point charge travelling in a non-uniform magnetic field. The transformation is valid as long as the gyroradius of the charged particles is much smaller than the magnetic field non-uniformity length scale, so that the guiding-centre Lie-transform method is applicable. Elimination of the gyromotion time scale from the radiation-reaction force is obtained with the Poisson-bracket formalism originally introduced by Brizard (Phys. Plasmas, vol. 11, 2004, 4429-4438), where it was used to eliminate the fast gyromotion from the Fokker-Planck collision operator. The formalism presented here is applicable to the motion of charged particles in planetary magnetic fields as well as in magnetic confinement fusion plasmas, where the corresponding so-called synchrotron radiation can be detected. Applications of the guiding-centre radiation-reaction force include tracing of charged particle orbits in complex magnetic fields as well as the kinetic description of plasma when the loss of energy and momentum due to radiation plays an important role, e.g. for runaway-electron dynamics in tokamaks.

  19. Carbon monoxide poisoning

    PubMed Central

    Dolan, Michael C.

    1985-01-01

    Carbon monoxide poisoning is a significant cause of illness and death. Its protean symptoms probably lead to a gross underestimation of its true incidence. Low levels of carbon monoxide aggravate chronic cardiopulmonary problems, and high levels are associated with cardiac arrhythmias and cerebral edema. Patients who survive acute poisoning are at risk of delayed neurologic sequelae. The measurement of carboxyhemoglobin levels does not reveal the tissue levels of carbon monoxide but is useful in determining therapy. Treatment includes the monitoring and management of cardiac arrhythmias and oxygenation. Hyperbaric oxygenation is beneficial, but there are currently no definite criteria for its use. PMID:4027805

  20. Application of TAGE Iterative Methods for the Solution of Nonlinear Two Point Boundary Value Problems with Linear Mixed Boundary Conditions on a Non-Uniform Mesh

    NASA Astrophysics Data System (ADS)

    Mohanty, R. K.; Talwar, Jyoti; Khosla, Noopur

    2012-05-01

    We report the application of two parameter alternating group explicit (TAGE) iteration and Newton-TAGE iteration methods for the solution of nonlinear differential equation u″=F(x, u, u‧) subject to linear mixed boundary conditions on a non-uniform mesh. In both cases, we use only three non-uniform grid points. The convergence theory for TAGE iteration method is analyzed. Numerical examples are considered to demonstrate computationally and the utility of TAGE iteration methods.

  1. Carbon monoxide poisoning

    MedlinePlus

    ... any major gas-burning appliances (such as a furnace or water heater). Many carbon monoxide poisonings occur in the winter months when furnaces, gas fireplaces, and portable heaters are being used ...

  2. Carbon Monoxide Information Center

    MedlinePlus Videos and Cool Tools

    ... Center The Invisible Killer Carbon monoxide, also known as CO, is called the "Invisible Killer" because it's ... used or incorrectly-vented fuel-burning appliances such as furnaces, stoves, water heaters and fireplaces. Watch This ...

  3. Carbon monoxide intoxication

    SciTech Connect

    Kales, S.N. )

    1993-11-01

    Carbon monoxide poisoning usually results from inhalation of exhaust fumes from motor vehicles, smoke from fires or fumes from faulty heating systems. Carbon monoxide has a high affinity for hemoglobin, with which it forms carboxyhemoglobin. The resulting decrease in both oxygen-carrying capacity and oxygen release can lead to end-organ hypoxia. The clinical presentation is nonspecific. Headache, dizziness, fatigue and nausea are common in mild to moderate carbon monoxide poisoning. In more severe cases, tachycardia, tachypnea and central nervous system depression occur. When carbon monoxide intoxication is suspected, empiric treatment with 100 percent oxygen should be initiated immediately. The diagnosis is confirmed by documenting an elevated carboxyhemoglobin level. Hyperbaric oxygen therapy is recommended in patients with neurologic dysfunction, cardiac dysfunction or a history of unconsciousness. 26 refs.

  4. Carbon Monoxide Poisoning

    MedlinePlus

    ... colorless gas created when fuels (such as gasoline, wood, coal, natural gas, propane, oil, and methane) burn incompletely. ** Carbon Monoxide can have different effects on people based on its concentration in the ...

  5. Estimating carbon monoxide exposure

    NASA Technical Reports Server (NTRS)

    Edgerley, R. H.

    1971-01-01

    Method predicts effects of carbon monoxide on astronauts confined in spacecraft cabin atmospheres. Information on need for low toxicity level also applies to confined spaces. Benefits are applicable to industry and public health.

  6. Experimental study on occupant's thermal responses under the non-uniform conditions in vehicle cabin during the heating period

    NASA Astrophysics Data System (ADS)

    Zhang, Wencan; Chen, Jiqing; Lan, Fengchong

    2014-03-01

    The existing investigations on thermal comfort mostly focus on the thermal environment conditions, especially of the air-flow field and the temperature distributions in vehicle cabin. Less attention appears to direct to the thermal comfort or thermal sensation of occupants, even to the relationship between thermal conditions and thermal sensation. In this paper, a series of experiments were designed and conducted for understanding the non-uniform conditions and the occupant's thermal responses in vehicle cabin during the heating period. To accurately assess the transient temperature distribution in cabin in common daily condition, the air temperature at a number of positions is measured in a full size vehicle cabin under natural winter environment in South China by using a discrete thermocouples network. The occupant body is divided into nine segments, the skin temperature at each segment and the occupant's local thermal sensation at the head, body, upper limb and lower limb are monitored continuously. The skin temperature is observed by using a discrete thermocouples network, and the local thermal sensation is evaluated by using a seven-point thermal comfort survey questionnaire proposed by American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc(ASHRAE) Standard. The relationship between the skin temperature and the thermal sensation is discussed and regressed by statistics method. The results show that the interior air temperature is highly non-uniform over the vehicle cabin. The locations where the occupants sit have a significant effect on the occupant's thermal responses, including the skin temperature and the thermal sensation. The skin temperature and thermal sensation are quite different between body segments due to the effect of non-uniform conditions, clothing resistance, and the human thermal regulating system. A quantitative relationship between the thermal sensation and the skin temperature at each body segment of occupant in

  7. Determining the response of infinite, one-dimensional, non-uniform periodic structures by substructuring using waveshape coordinates

    NASA Astrophysics Data System (ADS)

    Brown, G. P.; Byrne, K. P.

    2005-10-01

    A method is presented for determining the wavenumbers, waveshapes and point receptances for an infinite, one-dimensional, non-uniform periodic structure with distributed periodic attachments or supports. The approach is based on a general theory of harmonic wave propagation in one-dimensional periodic systems. Ill-conditioning was previously reported as an impediment to applying the theory to problems of practical importance. In this paper ill-conditioning problems are overcome and a method of substructuring using waveshape coordinates is presented that dramatically improves computational efficiency. The accuracy and generality of the new method are tested by comparing computed and measured receptances for a typical TGV railway track with UIC60 rail, rail pad, ballast and concrete sleepers. The computed results are found to correlate well with measured data.

  8. Beam test studies of 3D pixel sensors irradiated non-uniformly for the ATLAS forward physics detector

    NASA Astrophysics Data System (ADS)

    Grinstein, S.; Baselga, M.; Boscardin, M.; Christophersen, M.; Da Via, C.; Dalla Betta, G.-F.; Darbo, G.; Fadeyev, V.; Fleta, C.; Gemme, C.; Grenier, P.; Jimenez, A.; Lopez, I.; Micelli, A.; Nelist, C.; Parker, S.; Pellegrini, G.; Phlips, B.; Pohl, D.-L.; Sadrozinski, H. F.-W.; Sicho, P.; Tsiskaridze, S.

    2013-12-01

    Pixel detectors with cylindrical electrodes that penetrate the silicon substrate (so called 3D detectors) offer advantages over standard planar sensors in terms of radiation hardness, since the electrode distance is decoupled from the bulk thickness. In recent years significant progress has been made in the development of 3D sensors, which culminated in the sensor production for the ATLAS Insertable B-Layer (IBL) upgrade carried out at CNM (Barcelona, Spain) and FBK (Trento, Italy). Based on this success, the ATLAS Forward Physics (AFP) experiment has selected the 3D pixel sensor technology for the tracking detector. The AFP project presents a new challenge due to the need for a reduced dead area with respect to IBL, and the in-homogeneous nature of the radiation dose distribution in the sensor. Electrical characterization of the first AFP prototypes and beam test studies of 3D pixel devices irradiated non-uniformly are presented in this paper.

  9. Memory usage reduction and intensity modulation for 3D holographic display using non-uniformly sampled computer-generated holograms

    NASA Astrophysics Data System (ADS)

    Zhang, Zhao; Liu, Juan; Jia, Jia; Li, Xin; Pan, Yijie; Han, Jian; Hu, Bin; Wang, Yongtian

    2013-12-01

    The real-time holographic display encounters heavy computational load of computer-generated holograms and precisely intensity modulation of 3D images reconstructed by phase-only holograms. In this study, we demonstrate a method for reducing memory usage and modulating the intensity in 3D holographic display. The proposed method can eliminate the redundant information of holograms by employing the non-uniform sampling technique. By combining with the novel look-up table method, 70% reduction in the storage amount can be reached. The gray-scale modulation of 3D images reconstructed by phase-only holograms can be extended either. We perform both numerical simulations and optical experiments to verify the practicability of this method, and the results match well with each other. It is believed that the proposed method can be used in 3D dynamic holographic display and design of the diffractive phase elements.

  10. Ram-pressure scaling and non-uniformity characterization of a spherically imploding liner formed by hypervelocity plasma jets

    NASA Astrophysics Data System (ADS)

    Cassibry, Jason; Dougherty, Jesse; Thompson, Seth; Hsu, Scott; Witherspoon, F. D.; University of AL in Huntsville Team; Los Alamos National Laboratory Team; HyperV Technologies Corp. Team

    2014-10-01

    Three-dimensional modeling of plasma liner formation and implosion is performed using the Smoothed Particle Hydrodynamics Code (SPHC) with radiation, thermal transport, and tabular equations of state (EOS), accounting for ionization, in support of a proposed 60-gun plasma liner formation experiment for plasma-jet driven magneto-inertial fusion (PJMIF). Previous SPHC modeling showed that ideal gas law scaling of peak stagnation pressure increased linearly with density and number of jets, quadratically with jet radius and velocity, and inversely with the initial jet length, while results with tabular EOS, thermal transport, and radiation have greater sensitivity to the initial jet distribution. A series of simulations are conducted to study the effects of initial jet conditions on peak ram pressure and liner non-uniformity during plasma liner implosion. The growth rate of large-amplitude density perturbations introduced by the discrete jets are computed and compared with predictions by the Bell-Plesset equation.

  11. Temperature-driven self-assembly of self-limiting uniform supraparticles from non-uniform unimolecular micelles.

    PubMed

    Picco, Agustín S; Yameen, Basit; Knoll, Wolfgang; Ceolín, Marcelo R; Azzaroni, Omar

    2016-06-01

    In this work, the self-assembly of non-uniform unimolecular micelles constituted of a hyperbranched polyester core decorated with a corona of thermoresponsive poly(N-isopropylacrylamide) (PNIPAm) chains has been studied. As revealed by dynamic light scattering (DLS), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS), these unimicelles form uniform supraparticles through a thermally-induced self-limited process, as well as exhibit molecular features commonly observed in PNIPAm-based gels. We believe that these results provide new insights into the application of stimuli-responsive polymeric materials as versatile building blocks to build up soft supraparticles displaying well-defined dimensional characteristics. PMID:26990953

  12. Characterization of the non-uniform reaction in chemically-amplified calix[4]resorcinarene molecular resist thin films

    SciTech Connect

    Prabhu, Vivek M.; Kang, Shuhui; Kline, R. Joseph; DeLongchamp, Dean M.; Fischer, Daniel A.; Wu, Wen-li; Satija, Sushil K.; Bonnesen, Peter V; Sha, Jing; Ober, Christoper K.

    2011-01-01

    The ccc stereoisomer-purified tert-butoxycarbonyloxy (t-Boc) protected calix[4]resorcinarene molecular resists blended with photoacid generator exhibit a non-uniform photoacid catalyzed reaction in thin films. The surface displays a reduced reaction extent, compared to the bulk, with average surface-layer thickness (7.0 1.8) nm determined by neutron reflectivity with deuterium-labeled t-Boc groups. Ambient impurities (amines and organic bases) are known to quench surface reactions and contribute, but grazing incidence X-ray diffraction shows an additional effect that the protected molecular resist are preferentially oriented at the surface, while the bulk of the film displayed diffuse scattering representative of amorphous packing. The surface deprotection reaction and presence of photoacid was quantified by near-edge X-ray absorption fine structure measurements.

  13. Free vibration analysis of a robotic fish based on a continuous and non-uniform flexible backbone with distributed masses

    NASA Astrophysics Data System (ADS)

    Coral, W.; Rossi, C.; Curet, O. M.

    2015-12-01

    This paper presents a Differential Quadrature Element Method for free transverse vibration of a robotic fish based on a continuous and non-uniform flexible backbone with distributed masses (fish ribs). The proposed method is based on the theory of a Timoshenko cantilever beam. The effects of the masses (number, magnitude and position) on the value of natural frequencies are investigated. Governing equations, compatibility and boundary conditions are formulated according to the Differential Quadrature rules. The convergence, efficiency and accuracy are compared to other analytical solution proposed in the literature. Moreover, the proposed method has been validate against the physical prototype of a flexible fish backbone. The main advantages of this method, compared to the exact solutions available in the literature are twofold: first, smaller computational cost and second, it allows analysing the free vibration in beams whose section is an arbitrary function, which is normally difficult or even impossible with other analytical methods.

  14. Accelerating spatially non-uniform update for sparse target recovery in fluorescence molecular tomography by ordered subsets and momentum methods

    NASA Astrophysics Data System (ADS)

    Zhu, Dianwen; Li, Changqing

    2015-03-01

    Fluorescence molecular tomography (FMT) is a significant preclinical imaging modality that has been actively studied in the past two decades. However, it remains a challenging task to obtain fast and accurate reconstruction of fluorescent probe distribution in small animals due to the large computational burden and the ill-posed nature of the inverse problem. We have recently studied a non-uniform multiplicative updating algorithm, and obtained some further speed gain with the ordered subsets (OS) method. However, increasing the number of OS leads to larger approximation errors and the speed gain from larger number of OS is marginal. In this paper, we propose to further enhance the convergence speed by incorporating the first order momentum method that uses previous iterations to achieve a quadratic convergence rate. Using cubic phantom experiment, we have shown that the proposed method indeed leads to a much faster convergence.

  15. A Delta-Sigma Modulator Using a Non-uniform Quantizer Adjusted for the Probability Density of Input Signals

    NASA Astrophysics Data System (ADS)

    Kitayabu, Toru; Hagiwara, Mao; Ishikawa, Hiroyasu; Shirai, Hiroshi

    A novel delta-sigma modulator that employs a non-uniform quantizer whose spacing is adjusted by reference to the statistical properties of the input signal is proposed. The proposed delta-sigma modulator has less quantization noise compared to the one that uses a uniform quantizer with the same number of output values. With respect to the quantizer on its own, Lloyd proposed a non-uniform quantizer that is best for minimizing the average quantization noise power. The applicable condition of the method is that the statistical properties of the input signal, the probability density, are given. However, the procedure cannot be directly applied to the quantizer in the delta-sigma modulator because it jeopardizes the modulator's stability. In this paper, a procedure is proposed that determine the spacing of the quantizer with avoiding instability. Simulation results show that the proposed method reduces quantization noise by up to 3.8dB and 2.8dB with the input signal having a PAPR of 16dB and 12dB, respectively, compared to the one employing a uniform quantizer. Two alternative types of probability density function (PDF) are used in the proposed method for the calculation of the output values. One is the PDF of the input signal to the delta-sigma modulator and the other is an approximated PDF of the input signal to the quantizer inside the delta-sigma modulator. Both approaches are evaluated to find that the latter gives lower quantization noise.

  16. Variable parameter McCarthy-Muskingum flow transport model for compound channels accounting for distributed non-uniform lateral flow

    NASA Astrophysics Data System (ADS)

    Swain, Ratnakar; Sahoo, Bhabagrahi

    2015-11-01

    In this study, the fully volume conservative simplified hydrodynamic-based variable parameter McCarthy-Muskingum (VPMM) flow transport model advocated by Perumal and Price in 2013 is extended to exclusively incorporate the distributed non-uniform lateral flow in the routing scheme accounting for compound river channel flows. The revised VPMM formulation is exclusively derived from the combined form of the de Saint-Venant's continuity and momentum equations with the spatiotemporally distributed lateral flow which is solved using the finite difference box scheme. This revised model could address the earlier model limitations of: (i) non-accounting non-uniformly distributed lateral flow, (ii) ignoring floodplain flow, and (iii) non-consideration of catchment dynamics of lateral flow generation restricting its real-time application. The efficacy of the revised formulation is tested to simulate 16 years (1980-1995) river runoff from real-time storm events under scarce morpho-hydrological data conditions in a tropical monsoon-type 48 km Bolani-Gomlai reach of the Brahmani River in eastern India. The spatiotemporally distributed lateral flows generated in real-time is computed by water balance approach accounting for catchment characteristics of normalized network area function, land use land cover classes, and soil textural classes; and hydro-meteorological variables of precipitation, soil moisture, minimum and maximum temperatures, wind speed, relative humidity, and solar radiation. The multiple error measures used in this study and the simulation results reveal that the revised VPMM model has a greater practical utility in estimating the event-based and long-term meso-scale river runoff (both discharge and its stage) at any ungauged site, enhancing its application for real-time flood estimation.

  17. Issues in measure-preserving three dimensional flow integrators: Self-adjointness, reversibility, and non-uniform time stepping

    SciTech Connect

    Finn, John M.

    2015-03-01

    Properties of integration schemes for solenoidal fields in three dimensions are studied, with a focus on integrating magnetic field lines in a plasma using adaptive time stepping. It is shown that implicit midpoint (IM) and a scheme we call three-dimensional leapfrog (LF) can do a good job (in the sense of preserving KAM tori) of integrating fields that are reversible, or (for LF) have a 'special divergence-free' property. We review the notion of a self-adjoint scheme, showing that such schemes are at least second order accurate and can always be formed by composing an arbitrary scheme with its adjoint. We also review the concept of reversibility, showing that a reversible but not exactly volume-preserving scheme can lead to a fractal invariant measure in a chaotic region, although this property may not often be observable. We also show numerical results indicating that the IM and LF schemes can fail to preserve KAM tori when the reversibility property (and the SDF property for LF) of the field is broken. We discuss extensions to measure preserving flows, the integration of magnetic field lines in a plasma and the integration of rays for several plasma waves. The main new result of this paper relates to non-uniform time stepping for volume-preserving flows. We investigate two potential schemes, both based on the general method of Ref. [11], in which the flow is integrated in split time steps, each Hamiltonian in two dimensions. The first scheme is an extension of the method of extended phase space, a well-proven method of symplectic integration with non-uniform time steps. This method is found not to work, and an explanation is given. The second method investigated is a method based on transformation to canonical variables for the two split-step Hamiltonian systems. This method, which is related to the method of non-canonical generating functions of Ref. [35], appears to work very well.

  18. A model to non-uniform Ni Schottky contact on SiC annealed at elevated temperatures

    SciTech Connect

    Pristavu, G.; Brezeanu, G.; Badila, M.; Pascu, R.; Danila, M.; Godignon, P.

    2015-06-29

    Ni Schottky contacts on SiC have a nonideal behavior, with strong temperature dependence of the electrical parameters, caused by a mixed barrier on the contact area and interface states. A simple analytical model that establishes a quantitative correlation between Schottky contact parameter variation with temperature and barrier height non-uniformity is proposed. A Schottky contact surface with double Schottky barrier is considered. The main model parameters are the lower barrier (Φ{sub Bn,l}) and a p factor which quantitatively evaluates the barrier non-uniformity on the Schottky contact area. The model is validated on Ni/4H-SiC Schottky contacts, post metallization sintered at high temperatures. The measured I{sub F}–V{sub F}–T characteristics, selected so as not to be affected by interface states, were used for model correlation. An inhomogeneous double Schottky barrier (with both nickel silicide and Ni droplets at the interface) is formed by a rapid thermal annealing (RTA) at 750 °C. High values of the p parameter are obtained from samples annealed at this temperature, using the proposed model. A significant improvement in the electrical properties occurs following RTA at 800 °C. The expansion of the Ni{sub 2}Si phase on the whole contact area is evinced by an X-Ray diffraction investigation. In this case, the p factor is much lower, attesting the uniformity of the contact. The model makes it possible to evaluate the real Schottky barrier, for a homogenous Schottky contact. Using data measured on samples annealed at 800 °C, a true barrier height of around 1.73 V has been obtained for Ni{sub 2}Si/4H-SiC Schottky contacts.

  19. A model to non-uniform Ni Schottky contact on SiC annealed at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Pristavu, G.; Brezeanu, G.; Badila, M.; Pascu, R.; Danila, M.; Godignon, P.

    2015-06-01

    Ni Schottky contacts on SiC have a nonideal behavior, with strong temperature dependence of the electrical parameters, caused by a mixed barrier on the contact area and interface states. A simple analytical model that establishes a quantitative correlation between Schottky contact parameter variation with temperature and barrier height non-uniformity is proposed. A Schottky contact surface with double Schottky barrier is considered. The main model parameters are the lower barrier (ΦBn,l) and a p factor which quantitatively evaluates the barrier non-uniformity on the Schottky contact area. The model is validated on Ni/4H-SiC Schottky contacts, post metallization sintered at high temperatures. The measured IF-VF-T characteristics, selected so as not to be affected by interface states, were used for model correlation. An inhomogeneous double Schottky barrier (with both nickel silicide and Ni droplets at the interface) is formed by a rapid thermal annealing (RTA) at 750 °C. High values of the p parameter are obtained from samples annealed at this temperature, using the proposed model. A significant improvement in the electrical properties occurs following RTA at 800 °C. The expansion of the Ni2Si phase on the whole contact area is evinced by an X-Ray diffraction investigation. In this case, the p factor is much lower, attesting the uniformity of the contact. The model makes it possible to evaluate the real Schottky barrier, for a homogenous Schottky contact. Using data measured on samples annealed at 800 °C, a true barrier height of around 1.73 V has been obtained for Ni2Si/4H-SiC Schottky contacts.

  20. some morphological effects related to a non-uniform uplifting of crustal blocks in Northern Sicily (Central Mediterranean)

    NASA Astrophysics Data System (ADS)

    Nigro, Fabrizio; Renda, Pietro; Favara, Rocco

    2010-05-01

    We can distinguish two morphological evolutions of the drainage basins which develop in the earth's sectors subjected to uplift and tilting, in relationship to their antecedence or subsequence in comparison to the tectonic process. If this process begins in concomitance with a geomorphic cycle the main valleys of the drainage basins will longitudinally be developed according to the tilting direction which the crustal block is subjected. But if the non-uniform vertical movement develops in a sector already characterized by the presence of a idrographic network, this can be influenced in its pattern in various ways. A crustal block contemporarily subject to uplift and tilting will be characterized to its inside, at the end of this process, by more elevated and less elevated sectors. The erosive ground processes suffer this non-uniform vertical movement and since it gradually develops in time, landforms, as valleys of drainage basins, will suffer analogous variations. If pre-existing, the slopes of the valleys will be subjected to tilting also and one of the characteristics in the evolution of the reliefs connected with the uplift and the tilting of crustal blocks are represented by the progressive asymmetry of the slopes of a valley. The uplift and the tilting of the block progressively determines a difference of inclination of the slopes of the incising valley. This effect is given by the progressive incision and migration of the axis of the valley that it determines slopes with crests to different middle elevation between the right side and that left. The erosional process that determines him with the uplift and the tilting of the crustal blocks are characterized by a greater erosion rate in the sectors of head of the slope that is mostly raised. Likewise, the migration of the river consistent with the tilting direction determines a greater rate of erosion along one of the banks. The general morphometric result can be that of the individualization of slopes that

  1. Forward solution of the electromagnetic field induced by tsunamis using non-uniform thin-sheet approximation

    NASA Astrophysics Data System (ADS)

    Kawashima, I.; Toh, H.; Satake, K.

    2013-12-01

    A seafloor geomagnetic observatory in the northwest Pacific detected clear electromagnetic (EM) variations associated with tsunami passage from two earthquakes that occurred along the Kuril Trench (Toh et al., 2011). Previous seismological analyses indicated that the M8.3 earthquake on 15 November 2006 was an underthrust type on the landward slope of the trench, while the M8.1 earthquake on 13 January 2007 was a normal fault type on the seaward side (Ammon et al., 2008). Here we report the simulation results on the frequency dependence of those tsunami-induced EM signals observed at the seafloor, using a three-dimensional (3-D) non-uniform thin-sheet approximation by Dawson and Weaver (1979) and McKirdy, Weaver, & Dawson (1985), which can accommodate not only the inducing non-uniform source fields caused by particle motions of conducting seawater at the time of tsunami passage but also the self-induction effect within the ocean and its conductive substrata. Horizontal particle motions were calculated by Fujii and Satake (2008) with two types of hydrodynamic approximation, viz., the Boussinesq approximation and the long-wave approximation. Because the dispersion effect of each tsunami was more remarkable in the 2007 event, the observed EM variations were expected to be more compatible with the simulated EM signals using the Boussinesq approximation than the long-wave approximation. We calculated EM variations after we confirmed that synthetic plane waves in a flat ocean produced theoretically predicted harmonic EM variations well. In both approximations, the calculated EM variations associated with the initial wave of the tsunami at the time of the 2006 event are consistent with the observed ones, but the agreement became worse for the subsequent tsunami phases. As for the 2007 event, the calculated EM variations were less consistent compared with the 2006 event irrespective to the hydrodynamic approximations used. This can be due to the current limitation of thin

  2. Issues in measure-preserving three dimensional flow integrators: Self-adjointness, reversibility, and non-uniform time stepping

    SciTech Connect

    Finn, John M.

    2015-03-15

    Properties of integration schemes for solenoidal fields in three dimensions are studied, with a focus on integrating magnetic field lines in a plasma using adaptive time stepping. It is shown that implicit midpoint (IM) and a scheme we call three-dimensional leapfrog (LF) can do a good job (in the sense of preserving KAM tori) of integrating fields that are reversible, or (for LF) have a “special divergence-free” (SDF) property. We review the notion of a self-adjoint scheme, showing that such schemes are at least second order accurate and can always be formed by composing an arbitrary scheme with its adjoint. We also review the concept of reversibility, showing that a reversible but not exactly volume-preserving scheme can lead to a fractal invariant measure in a chaotic region, although this property may not often be observable. We also show numerical results indicating that the IM and LF schemes can fail to preserve KAM tori when the reversibility property (and the SDF property for LF) of the field is broken. We discuss extensions to measure preserving flows, the integration of magnetic field lines in a plasma and the integration of rays for several plasma waves. The main new result of this paper relates to non-uniform time stepping for volume-preserving flows. We investigate two potential schemes, both based on the general method of Feng and Shang [Numer. Math. 71, 451 (1995)], in which the flow is integrated in split time steps, each Hamiltonian in two dimensions. The first scheme is an extension of the method of extended phase space, a well-proven method of symplectic integration with non-uniform time steps. This method is found not to work, and an explanation is given. The second method investigated is a method based on transformation to canonical variables for the two split-step Hamiltonian systems. This method, which is related to the method of non-canonical generating functions of Richardson and Finn [Plasma Phys. Controlled Fusion 54, 014004 (2012

  3. Acoustic field modeling for physiotherapy ultrasound applicators by using approximated functions of measured non-uniform radiation distributions.

    PubMed

    Gutiérrez, Mario Ibrahín; Calás, Héctor; Ramos, Antonio; Vera, Arturo; Leija, Lorenzo

    2012-08-01

    The strongest therapeutic effects in ultrasonic physiotherapy are mainly produced at the first centimeters, i.e. close to the applicator surface and, in general, only in the near-field zone. The acoustic field produced in practice by this type of transducers differs from the classical models because the vibration distribution on the real transducer surfaces is non-uniform. However, neither models using uniform distribution, nor those using typical non-uniform distribution patterns for the source accurately represent the radiation of this kind of transducers. Although this therapy is widely used and many efforts have been made in experimentally studying the patterns of ultrasound radiation produced during physiotherapy applications (IEC-61689, 1998), additional modeling researches still would be needed in order to achieve improved models giving field patterns closer to the measured ultrasonic results. In this paper, acoustic patterns produced from two source radiation functions are proposed and evaluated for field modeling of physiotherapy applicators. Both the functions are approximations to the pressure distribution measured close to the emitting surface and they are based on the modulation of the classical simply-supported function using either sinusoidal or Bessel-type distributions. The simply-supported function is accounted for the radiator-fixing condition and the modulation function simulates the complex vibration distribution of this kind of transducer. The modulator Bessel function is based on reports about Bessel-type vibration distributions found in piezoelectric disk resonators. The use of a selected sinusoidal segment represents another analytical option for obtaining an approximated behavior of the measured data in a real applicator. Both the field models are implemented using the finite element method (FEM) to obtain the numerical solution of wave equation at each point in the radiated space. The solution is reached by considering axisymmetric

  4. Issues in measure-preserving three dimensional flow integrators: Self-adjointness, reversibility, and non-uniform time stepping

    DOE PAGESBeta

    Finn, John M.

    2015-03-01

    Properties of integration schemes for solenoidal fields in three dimensions are studied, with a focus on integrating magnetic field lines in a plasma using adaptive time stepping. It is shown that implicit midpoint (IM) and a scheme we call three-dimensional leapfrog (LF) can do a good job (in the sense of preserving KAM tori) of integrating fields that are reversible, or (for LF) have a 'special divergence-free' property. We review the notion of a self-adjoint scheme, showing that such schemes are at least second order accurate and can always be formed by composing an arbitrary scheme with its adjoint. Wemore » also review the concept of reversibility, showing that a reversible but not exactly volume-preserving scheme can lead to a fractal invariant measure in a chaotic region, although this property may not often be observable. We also show numerical results indicating that the IM and LF schemes can fail to preserve KAM tori when the reversibility property (and the SDF property for LF) of the field is broken. We discuss extensions to measure preserving flows, the integration of magnetic field lines in a plasma and the integration of rays for several plasma waves. The main new result of this paper relates to non-uniform time stepping for volume-preserving flows. We investigate two potential schemes, both based on the general method of Ref. [11], in which the flow is integrated in split time steps, each Hamiltonian in two dimensions. The first scheme is an extension of the method of extended phase space, a well-proven method of symplectic integration with non-uniform time steps. This method is found not to work, and an explanation is given. The second method investigated is a method based on transformation to canonical variables for the two split-step Hamiltonian systems. This method, which is related to the method of non-canonical generating functions of Ref. [35], appears to work very well.« less

  5. A coarse-grained model of the myofibril: Overall dynamics and the evolution of sarcomere non-uniformities

    NASA Astrophysics Data System (ADS)

    Givli, Sefi; Bhattacharya, Kaushik

    2009-02-01

    A theoretical framework for predicting the macroscopic behavior of a muscle myofibril based on the collective behavior of sarcomeres is presented. The analysis is accomplished by rigorously transforming the nonlinear dynamics of an assemblage of sarcomeres into a partial differential equation for the probability distribution function of sarcomere lengths in the presence of stochastic temporal fluctuations and biological variability. This enables the study of biologically relevant specimens with reasonable computational effort. The model is validated by a comparison to quantitative experimental results. Further, it reproduces experimental observations that cannot be explained by standard single sarcomere models, and provides new insights into muscle function and muscle damage during cyclic loading. We show that the accumulation of overstretched sarcomeres, which is related to muscle damage, depends on a delicate interplay between the dynamics of a large number of sarcomeres and the load characteristics, such as its magnitude and frequency. Further, we show that biological variability rather than stochastic fluctuations are the main source for sarcomere non-uniformities.

  6. The segmented non-uniform dielectric module design for uniformity control of plasma profile in a capacitively coupled plasma chamber

    SciTech Connect

    Xia, Huanxiong Xiang, Dong Yang, Wang Mou, Peng

    2014-12-15

    Low-temperature plasma technique is one of the critical techniques in IC manufacturing process, such as etching and thin-film deposition, and the uniformity greatly impacts the process quality, so the design for the plasma uniformity control is very important but difficult. It is hard to finely and flexibly regulate the spatial distribution of the plasma in the chamber via controlling the discharge parameters or modifying the structure in zero-dimensional space, and it just can adjust the overall level of the process factors. In the view of this problem, a segmented non-uniform dielectric module design solution is proposed for the regulation of the plasma profile in a CCP chamber. The solution achieves refined and flexible regulation of the plasma profile in the radial direction via configuring the relative permittivity and the width of each segment. In order to solve this design problem, a novel simulation-based auto-design approach is proposed, which can automatically design the positional sequence with multi independent variables to make the output target profile in the parameterized simulation model approximate the one that users preset. This approach employs an idea of quasi-closed-loop control system, and works in an iterative mode. It starts from initial values of the design variable sequences, and predicts better sequences via the feedback of the profile error between the output target profile and the expected one. It never stops until the profile error is narrowed in the preset tolerance.

  7. Long-range weight functions in fundamental measure theory of the non-uniform hard-sphere fluid.

    PubMed

    Hansen-Goos, Hendrik

    2016-06-22

    We introduce long-range weight functions to the framework of fundamental measure theory (FMT) of the non-uniform, single-component hard-sphere fluid. While the range of the usual weight functions is equal to the hard-sphere radius R, the modified weight functions have range 3R. Based on the augmented FMT, we calculate the radial distribution function g(r) up to second order in the density within Percus' test particle theory. Consistency of the compressibility and virial routes on this level allows us to determine the free parameter γ of the theory. As a side result, we obtain a value for the fourth virial coefficient B 4 which deviates by only 0.01% from the exact result. The augmented FMT is tested for the dense fluid by comparing results for g(r) calculated via the test particle route to existing results from molecular dynamics simulations. The agreement at large distances (r  >  6R) is significantly improved when the FMT with long-range weight functions is used. In order to improve agreement close to contact (r  =  2R) we construct a free energy which is based on the accurate Carnahan-Starling equation of state, rather than the Percus-Yevick compressibility equation underlying standard FMT. PMID:27115721

  8. Non-Uniform Distribution Pattern for Differentially Expressed Genes of Transgenic Rice Huahui 1 at Different Developmental Stages and Environments

    PubMed Central

    Liu, Zhi; Zhao, Jie; Li, Yunhe; Zhang, Wenwei; Jian, Guiliang; Peng, Yufa; Qi, Fangjun

    2012-01-01

    DNA microarray analysis is an effective method to detect unintended effects by detecting differentially expressed genes (DEG) in safety assessment of genetically modified (GM) crops. With the aim to reveal the distribution of DEG of GM crops under different conditions, we performed DNA microarray analysis using transgenic rice Huahui 1 (HH1) and its non-transgenic parent Minghui 63 (MH63) at different developmental stages and environmental conditions. Considerable DEG were selected in each group of HH1 under different conditions. For each group of HH1, the number of DEG was different; however, considerable common DEG were shared between different groups of HH1. These findings suggested that both DEG and common DEG were adequate for investigation of unintended effects. Furthermore, a number of significantly changed pathways were found in all groups of HH1, indicating genetic modification caused everlasting changes to plants. To our knowledge, our study for the first time provided the non-uniformly distributed pattern for DEG of GM crops at different developmental stages and environments. Our result also suggested that DEG selected in GM plants at specific developmental stage and environment could act as useful clues for further evaluation of unintended effects of GM plants. PMID:22606331

  9. Ray-tracing WKB analysis of Whistler waves in non-uniform magnetic fields applied to space thrusters

    NASA Astrophysics Data System (ADS)

    Cardinali, A.; Melazzi, D.; Manente, M.; Pavarin, D.

    2014-02-01

    Radiofrequency magnetized cylindrical plasma sources are proposed for the development of space thrusters, whose thrust efficiency and specific impulse depend on the power coupled into the plasma. At this stage of research, emphasis has been on the absorption of Whistler wave energy by non-uniform plasmas but not much on the role played by the magneto-static confinement field, considered uniform, constant and aligned with the axis of the source. We present RAYWh (RAY-tracing Whistler), a three-dimensional (3D) ray-tracing solver for electromagnetic propagation and power deposition in cylindrical plasma sources for space plasma thrusters, where actual magnetic confinement configurations along with plasma density profiles are included. The propagation and absorption of Whistler waves are investigated by solving the 3D Maxwell-Vlasov model equations by a Wentzel-Kramers-Brillouin (WKB) asymptotic expansion. The reduced set of equations for the wave phase and for the square amplitude of the electric field is solved numerically by means of a modified Runge-Kutta algorithm. Unexpected cut-offs, resonances, radial reflections, mode conversions and power deposition profile of the excited waves are found, when realistic confinement magnetic fields are considered. An analysis of the influence of axial wavenumbers and the axial length of the system on the power deposition is presented.

  10. Breakdown Characteristics of Gas Insulated Switchgears for Non-standard Lightning Impulse Waveforms under Non-uniform Electric Field

    NASA Astrophysics Data System (ADS)

    Ueta, Genyo; Kaneko, Shuhei; Okabe, Shigemitsu

    To improve insulation specification of a gas insulated switchgear (GIS), it is necessary to recognize the insulation characteristics of SF6 gas under actual surge (called non-standard lightning impulse waveform) occurring in the field substation. The authors had observed the insulation characteristics of SF6 gas gap under various types of non-standard lightning impulse waveforms and compared them with under standard lightning impulse waveform quantitatively. From the investigation of the experimental results, the evaluation method for real surges is shown and the method is applied to typical surges for various UHV and 500kV systems. In the proceeding study, therefore, only for the quasi-uniform electric field (with a typical range of the field utilization factors in the bus of a GIS) was investigated. In this paper, the insulation characteristics of SF6 gas gap for non-uniform electric field were observed experimentally and investigated about the evaluation method of converting non-standard lightning impulse waveforms equivalently to the standard lightning impulse waveform.

  11. Development of a non-uniform discrete Fourier transform based high speed spectral domain optical coherence tomography system.

    PubMed

    Wang, Kai; Ding, Zhihua; Wu, Tong; Wang, Chuan; Meng, Jie; Chen, Minghui; Xu, Lei

    2009-07-01

    We develop a high speed spectral domain optical coherence tomography (SD-OCT) system based on a custom-built spectrometer and non-uniform discrete Fourier transform (NDFT) to realize minimized depth dependent sensitivity fall-off. After precise spectral calibration of the spectrometer, NDFT of the acquired spectral data is adopted for image reconstruction. The spectrometer is able to measure a wavelength range of about 138 nm with a spectral resolution of 0.0674 nm at central wavelength of 835 nm, corresponding to an axial imaging range of 2.56 mm in air. Zemax simulations and sensitivity fall-off measurements under two alignment states of the spectrometer are given. Both theoretical simulations and experiments are done to study the depth dependent sensitivity of the developed system based on NDFT in contrast to those based on conventional discrete Fourier transform (DFT) with and without interpolation. In vivo imaging on human finger from volunteer is conducted at A-scan rate of 29 kHz and reconstruction is done based on different methods. The comparing results confirm that reconstruction method based on NDFT indeed improves sensitivity especially at large depth while maintaining the coherence-function-limited depth resolution. PMID:19582127

  12. Influence of non-uniform flow distribution on overall heat transfer in convective bundle of circulating fluidized bed boiler

    NASA Astrophysics Data System (ADS)

    Kalisz, Sylwester; Pronobis, Marek

    2005-09-01

    In the paper the results of comparative investigations on heat transfer performance of boiler convective bundle and its additional surface, i.e. membrane water wall are presented. For this purpose the non-uniform flow field was modelled in an isothermal test stand operated in self-modeling mode. Then the heat transfer characteristics of such arrangement were estimated by means of naphthalene heat/mass transfer analogy technique. The bundle samples in the shape of round bars (rods) were cast with naphthalene and placed in 27 locations in the bundle while water-wall-modeling samples were coated with naphthalene by painting. Both types of samples were exposed to cold air flow. The results were then compared to the mean heat transfer performance of the same bundle exposed to uniform flow field. The differences of approximately 10% were noticed. Moreover, the heat transfer coefficients for additional surface were even three times lower than those of the bundle. In view of results obtained in the work, the commonly made assumption of equality of heat transfer coefficients for both the bundle and its additional surface may lead to certain errors in heat transfer calculations and discrepancies between the calculated values of heating surfaces area and later operational needs of steam generator.

  13. Non-uniform noise spatial distribution in CT myocardial perfusion and a potential solution: statistical image reconstruction

    NASA Astrophysics Data System (ADS)

    Thériault Lauzier, Pascal; Tang, Jie; Chen, Guang-Hong

    2012-03-01

    Myocardial perfusion scans are an important tool in the assessment of myocardial viability following an infarction. Cardiac perfusion analysis using CT datasets is limited by the presence of so-called partial scan artifacts. These artifacts are due to variations in beam hardening and scatter between different short-scan angular ranges. In this research, another angular range dependent effect is investigated: non-uniform noise spatial distribution. Images reconstructed using filtered backprojection (FBP) are subject to this effect. Statistical image reconstruction (SIR) is proposed as a potential solution. A numerical phantom with added Poisson noise was simulated and two swines were scanned in vivo to study the effect of FBP and SIR on the spatial uniformity of the noise distribution. It was demonstrated that images reconstructed using FBP often show variations in noise on the order of 50% between different time frames. This variation is mitigated to about 10% using SIR. The noise level is also reduced by a factor of 2 in SIR images. Finally, it is demonstrated that the measurement of quantitative perfusion metrics are generally more accurate when SIR is used instead of FBP.

  14. Optimization of relativistic backward wave oscillator with non-uniform slow wave structure and a resonant reflector

    SciTech Connect

    Chen, Zaigao; Wang, Jianguo; Wang, Yue

    2015-01-15

    This letter optimizes synchronously 18 parameters of a relativistic backward wave oscillator with non-uniform slow wave structure (SWS) and a resonant reflector by using the parallel genetic algorithms and particle-in-cell simulation. The optimization results show that the generation efficiency of microwave from the electron beam has increased 32% compared to that of the original device. After optimization, the electromagnetic mode propagating in the resonant changes from the original TM{sub 020} mode of reflector to higher-order TM{sub 021} mode, which has a high reflection coefficient in a broader frequency range than that of the former. The modulation of current inside the optimized device is much deeper than that in the original one. The product of the electric field and current is defined. Observing this product, it is found that the interaction of the electron beam with the electromagnetic wave in the optimized device is much stronger than that in the original device, and at the rear part of SWS of the optimized device, the electron beam dominantly gives out the energy to the electromagnetic wave, leading to the higher generation efficiency of microwave than that of the original device.

  15. Local Available Potential Energy in Simulations of Stratified Turbulence with Uniform and Non-uniform Ambient Density Gradients

    NASA Astrophysics Data System (ADS)

    Portwood, Gavin; de Bruyn Kops, Stephen; Turbulence Simulation Laboratory Team

    2015-11-01

    In stratified flows, the maximum amount of potential energy that can be converted to kinetic energy is the difference between the potential energy in the instantaneous flow and that in the flow if the fluid parcels were adiabatically sorted to produce the lowest energy configuration. Lorentz (1955) defines this global quantity as available potential energy (APE). Holliday and McIntyre (1981) introduces the concept of local available potential energy (Ea) associated with a fluid parcel, and Molemaker and McWilliams (2010) develop the transport for this quantity for a viscous, Boussinesq fluid. Here, we characterize Ea in simulations of a vortex street with uniform and non-uniform stabilizing ambient density gradients. In pseudo-spectral direct numerical simulations resolved on up to 4096 × 2048 × 2048 grid points, we find that the majority of APE is due to fluid parcels displaced a small distance, relative to the buoyancy length scale, from their locations in the sorted density field. By computing each term in the transport equation for Ea, we observe by how much Ea of a fluid parcel changes in time due to local dipycnal mixing, and by how much global mixing alters the position of the local parcel in the sorted density field. This work is funded by DoD HPCMP though Frontier Project FPCFD-FY14-007 and the Office of Naval Research via grant N00014-15-1-2248.

  16. A unified approach for nonlinear vibration analysis of curved structures using non-uniform rational B-spline representation

    NASA Astrophysics Data System (ADS)

    Askari, H.; Esmailzadeh, E.; Barari, A.

    2015-09-01

    A novel procedure for the nonlinear vibration analysis of curved beam is presented. The Non-Uniform Rational B-Spline (NURBS) is combined with the Euler-Bernoulli beam theory to define the curvature of the structure. The governing equation of motion and the general frequency formula, using the NURBS variables, is applicable for any type of curvatures, is developed. The Galerkin procedure is implemented to obtain the nonlinear ordinary differential equation of curved system and the multiple time scales method is utilized to find the corresponding frequency responses. As a case study, the nonlinear vibration of carbon nanotubes with different shapes of curvature is investigated. The effect of oscillation amplitude and the waviness on the natural frequency of the curved nanotube is evaluated and the primary resonance case of system with respect to the variations of different parameters is discussed. For the sake of comparison of the results obtained with those from the molecular dynamic simulation, the natural frequencies evaluated from the proposed approach are compared with those reported in literature for few types of carbon nanotube simulation.

  17. Micro-scale blood particulate dynamics using a non-uniform rational B-spline-based isogeometric analysis.

    PubMed

    Chivukula, V; Mousel, J; Lu, J; Vigmostad, S

    2014-12-01

    The current research presents a novel method in which blood particulates - biconcave red blood cells (RBCs) and spherical cells are modeled using isogeometric analysis, specifically Non-Uniform Rational B-Splines (NURBS) in 3-D. The use of NURBS ensures that even with a coarse representation, the geometry of the blood particulates maintains an accurate description when subjected to large deformations. The fundamental advantage of this method is the coupling of the geometrical description and the stress analysis of the cell membrane into a single, unified framework. Details on the modeling approach, implementation of boundary conditions and the membrane mechanics analysis using isogeometric modeling are presented, along with validation cases for spherical and biconcave cells. Using NURBS - based isogeometric analysis, the behavior of individual cells in fluid flow is presented and analyzed in different flow regimes using as few as 176 elements for a spherical cell and 220 elements for a biconcave RBC. This work provides a framework for modeling a large number of 3-D deformable biological cells, each with its own geometric description and membrane properties. To the best knowledge of the authors, this is the first application of the NURBS - based isogeometric analysis to model and simulate blood particulates in flow in 3D. PMID:25132674

  18. Series-NonUniform Rational B-Spline (S-NURBS) model: A geometrical interpolation framework for chaotic data

    NASA Astrophysics Data System (ADS)

    Shao, Chenxi; Liu, Qingqing; Wang, Tingting; Yin, Peifeng; Wang, Binghong

    2013-09-01

    Time series is widely exploited to study the innate character of the complex chaotic system. Existing chaotic models are weak in modeling accuracy because of adopting either error minimization strategy or an acceptable error to end the modeling process. Instead, interpolation can be very useful for solving differential equations with a small modeling error, but it is also very difficult to deal with arbitrary-dimensional series. In this paper, geometric theory is considered to reduce the modeling error, and a high-precision framework called Series-NonUniform Rational B-Spline (S-NURBS) model is developed to deal with arbitrary-dimensional series. The capability of the interpolation framework is proved in the validation part. Besides, we verify its reliability by interpolating Musa dataset. The main improvement of the proposed framework is that we are able to reduce the interpolation error by properly adjusting weights series step by step if more information is given. Meanwhile, these experiments also demonstrate that studying the physical system from a geometric perspective is feasible.

  19. Series-NonUniform Rational B-Spline (S-NURBS) model: a geometrical interpolation framework for chaotic data.

    PubMed

    Shao, Chenxi; Liu, Qingqing; Wang, Tingting; Yin, Peifeng; Wang, Binghong

    2013-09-01

    Time series is widely exploited to study the innate character of the complex chaotic system. Existing chaotic models are weak in modeling accuracy because of adopting either error minimization strategy or an acceptable error to end the modeling process. Instead, interpolation can be very useful for solving differential equations with a small modeling error, but it is also very difficult to deal with arbitrary-dimensional series. In this paper, geometric theory is considered to reduce the modeling error, and a high-precision framework called Series-NonUniform Rational B-Spline (S-NURBS) model is developed to deal with arbitrary-dimensional series. The capability of the interpolation framework is proved in the validation part. Besides, we verify its reliability by interpolating Musa dataset. The main improvement of the proposed framework is that we are able to reduce the interpolation error by properly adjusting weights series step by step if more information is given. Meanwhile, these experiments also demonstrate that studying the physical system from a geometric perspective is feasible. PMID:24089968

  20. SPHARA - A Generalized Spatial Fourier Analysis for Multi-Sensor Systems with Non-Uniformly Arranged Sensors: Application to EEG

    PubMed Central

    Graichen, Uwe; Eichardt, Roland; Fiedler, Patrique; Strohmeier, Daniel; Zanow, Frank; Haueisen, Jens

    2015-01-01

    Important requirements for the analysis of multichannel EEG data are efficient techniques for signal enhancement, signal decomposition, feature extraction, and dimensionality reduction. We propose a new approach for spatial harmonic analysis (SPHARA) that extends the classical spatial Fourier analysis to EEG sensors positioned non-uniformly on the surface of the head. The proposed method is based on the eigenanalysis of the discrete Laplace-Beltrami operator defined on a triangular mesh. We present several ways to discretize the continuous Laplace-Beltrami operator and compare the properties of the resulting basis functions computed using these discretization methods. We apply SPHARA to somatosensory evoked potential data from eleven volunteers and demonstrate the ability of the method for spatial data decomposition, dimensionality reduction and noise suppression. When employing SPHARA for dimensionality reduction, a significantly more compact representation can be achieved using the FEM approach, compared to the other discretization methods. Using FEM, to recover 95% and 99% of the total energy of the EEG data, on average only 35% and 58% of the coefficients are necessary. The capability of SPHARA for noise suppression is shown using artificial data. We conclude that SPHARA can be used for spatial harmonic analysis of multi-sensor data at arbitrary positions and can be utilized in a variety of other applications. PMID:25885290

  1. Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties.

    PubMed

    Mehdizadeh Dehkordi, Arash; Bhattacharya, Sriparna; Darroudi, Taghi; Zeng, Xiaoyu; Alshareef, Husam N; Tritt, Terry M

    2015-01-01

    We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3. PMID:26327483

  2. Turbulent variance characteristics of temperature and humidity over a non-uniform land surface for an agricultural ecosystem in China

    NASA Astrophysics Data System (ADS)

    Gao, Z. Q.; Bian, L. G.; Chen, Z. G.; Sparrow, M.; Zhang, J. H.

    2006-05-01

    This paper describes the application of the variance method for flux estimation over a mixed agricultural region in China. Eddy covariance and flux variance measurements were conducted in a near-surface layer over a non-uniform land surface in the central plain of China from 7 June to 20 July 2002. During this period, the mean canopy height was about 0.50 m. The study site consisted of grass (10% of area), beans (15%), corn (15%) and rice (60%). Under unstable conditions, the standard deviations of temperature and water vapor density (normalized by appropriate scaling parameters), observed by a single instrument, followed the Monin-Obukhov similarity theory. The similarity constants for heat (C-T) and water vapor (C-q) were 1.09 and 1.49, respectively. In comparison with direct measurements using eddy covariance techniques, the flux variance method, on average, underestimated sensible heat flux by 21% and latent heat flux by 24%, which may be attributed to the fact that the observed slight deviations (20% or 30% at most) of the similarity "constants" may be within the expected range of variation of a single instrument from the generally-valid relations.

  3. Large-eddy simulation of boundary layer flow on a non-uniform grid using explicit filtering and reconstruction

    NASA Astrophysics Data System (ADS)

    Goodfriend, Lauren; Katopodes Chow, Fotini; Vanella, Marcos; Balaras, Elias

    2013-11-01

    Many realistic flows, such as the urban boundary layer, are too expensive to simulate directly. Large-eddy simulation (LES) and adaptive mesh refinement (AMR) reduce the computational cost of turbulence modeling by restricting resolved length scales, but combining these techniques generates additional errors. The grid refinement interfaces in AMR grids can reflect resolved energy and create interpolation errors. This study investigates the use of explicit filtering and reconstruction to mitigate grid interface errors in LES of a pressure gradient forced boundary layer. The domain is split in the streamwise direction into two equally sized structured grids, one fine and one coarse, with periodic boundaries in the streamwise and spanwise directions. This simple test case allows observation of the effects of the grid interfaces. Explicit filtering is found to reduce accumulation of resolved energy at the fine-to-coarse interface and improve the shape of coherent structures, compared to basic LES. Reconstruction of the subfilter velocity is shown to further the improvements of explicit filtering. These results inform the use of LES on block-structured non-uniform grids, such as nested grids in local atmospheric models or on more complex Cartesian AMR grids.

  4. The segmented non-uniform dielectric module design for uniformity control of plasma profile in a capacitively coupled plasma chamber

    NASA Astrophysics Data System (ADS)

    Xia, Huanxiong; Xiang, Dong; Yang, Wang; Mou, Peng

    2014-12-01

    Low-temperature plasma technique is one of the critical techniques in IC manufacturing process, such as etching and thin-film deposition, and the uniformity greatly impacts the process quality, so the design for the plasma uniformity control is very important but difficult. It is hard to finely and flexibly regulate the spatial distribution of the plasma in the chamber via controlling the discharge parameters or modifying the structure in zero-dimensional space, and it just can adjust the overall level of the process factors. In the view of this problem, a segmented non-uniform dielectric module design solution is proposed for the regulation of the plasma profile in a CCP chamber. The solution achieves refined and flexible regulation of the plasma profile in the radial direction via configuring the relative permittivity and the width of each segment. In order to solve this design problem, a novel simulation-based auto-design approach is proposed, which can automatically design the positional sequence with multi independent variables to make the output target profile in the parameterized simulation model approximate the one that users preset. This approach employs an idea of quasi-closed-loop control system, and works in an iterative mode. It starts from initial values of the design variable sequences, and predicts better sequences via the feedback of the profile error between the output target profile and the expected one. It never stops until the profile error is narrowed in the preset tolerance.

  5. A Non-uniform Stepping Mechanism for E. coli UvrD Monomer Translocation along Single Stranded DNA

    PubMed Central

    Tomko, Eric J.; Fischer, Christopher J.; Niedziela-Majka, Anita; Lohman, Timothy M.

    2007-01-01

    Summary E. coli UvrD is an SF1 helicase involved in several DNA metabolic processes. Although a UvrD dimer is needed for helicase activity, a monomer can translocate with 3′ to 5′ directionality along single stranded DNA and this ATP-dependent translocation is likely involved in RecA displacement. In order to understand how the monomeric translocase functions, we have combined fluorescence stopped-flow kinetic methods with novel analysis methods to determine the kinetic mechanism, including ATP coupling stoichiometry, for UvrD monomer translocation along ssDNA. Our results suggest that the macroscopic rate of UvrD monomer translocation is not limited by each ATPase cycle, but rather by a slow step (pause) in each translocation cycle that occurs after four to five rapid one nucleotide translocation steps, with each rapid step coupled to hydrolysis of one ATP. These results suggest a non-uniform stepping mechanism that differs from either a Brownian motor or previous structure based inch-worm mechanisms. PMID:17499041

  6. Long-range weight functions in fundamental measure theory of the non-uniform hard-sphere fluid

    NASA Astrophysics Data System (ADS)

    Hansen-Goos, Hendrik

    2016-06-01

    We introduce long-range weight functions to the framework of fundamental measure theory (FMT) of the non-uniform, single-component hard-sphere fluid. While the range of the usual weight functions is equal to the hard-sphere radius R, the modified weight functions have range 3R. Based on the augmented FMT, we calculate the radial distribution function g(r) up to second order in the density within Percus’ test particle theory. Consistency of the compressibility and virial routes on this level allows us to determine the free parameter γ of the theory. As a side result, we obtain a value for the fourth virial coefficient B 4 which deviates by only 0.01% from the exact result. The augmented FMT is tested for the dense fluid by comparing results for g(r) calculated via the test particle route to existing results from molecular dynamics simulations. The agreement at large distances (r  >  6R) is significantly improved when the FMT with long-range weight functions is used. In order to improve agreement close to contact (r  =  2R) we construct a free energy which is based on the accurate Carnahan–Starling equation of state, rather than the Percus–Yevick compressibility equation underlying standard FMT.

  7. Temperature and number density measurement in non-uniform supersonic flowfields undergoing mixing using toluene PLIF thermometry

    NASA Astrophysics Data System (ADS)

    Gamba, Mirko; Miller, Victor A.; Mungal, M. Godfrey; Hanson, Ronald K.

    2015-08-01

    Single-excitation, dual-band-collection toluene planar laser-induced fluorescence (PLIF) is used to measure temperature and number density (or partial pressure) fields in non-uniform supersonic complex flows in the presence of mixing and compressibility. The study provides a quantitative evaluation of the technique in transverse jets in supersonic crossflow (JISCF). It is found that toluene PLIF is highly effective in visualizing the structure of supersonic flows and that temperature can be accurately inferred with acceptable signal-to-noise ratios (of order 30) even when mixing occurs. The technique was applied to several JISCFs that differ by jet fluid properties with resulting different structures. In the presence of compressibility and mixing, it is found that the PLIF signal is non-unique, a feature that is used to identify the mixing region of the transverse jet. Measurement errors due to camera registration errors have also been quantified. Because of the complexity of the flowfield, it is found that minute misalignment (<0.1 pixels) between the two PLIF images can introduce measurable errors on the order of tens of Kelvins and significant errors in temperature gradients.

  8. Concentration polarization effects on the macromolecular transport in the presence of non-uniform magnetic field: A numerical study using a lumen-wall model

    NASA Astrophysics Data System (ADS)

    Mohammadpourfard, M.; Aminfar, H.; Khajeh, K.

    2014-04-01

    In this paper, the concentration polarization phenomena in a two dimensional tube under steady state conditions containing ferrofluid (blood and 4 vol% Fe3O4) is reported in the presence of non-uniform magnetic field. Lumen-wall model has been used for solving the mass transport equation. Hemodynamics parameters such as flow rate, viscosity, wall shear stress (WSS) and the macromolecules surface concentration which accumulate on the blood vessel wall, influenced the formation and progression of atherosclerosis disease. Effective parameters on the low density lipoprotein (LDL) surface concentration (LSC) such as: the wall filtration velocity, inlet Reynolds number and WSS under applied non-uniform magnetic field have been examined.

  9. Solid State Carbon Monoxide Sensor

    NASA Technical Reports Server (NTRS)

    Upchurch, Billy T. (Inventor); Wood, George M. (Inventor); Schryer, David R. (Inventor); Leighty, Bradley D. (Inventor); Oglesby, Donald M. (Inventor); Kielin, Erik J. (Inventor); Brown, Kenneth G. (Inventor); DAmbrosia, Christine M. (Inventor)

    1999-01-01

    A means for detecting carbon monoxide which utilizes an un-heated catalytic material to oxidize carbon monoxide at ambient temperatures. Because this reaction is exothermic, a thermistor in contact with the catalytic material is used as a sensing element to detect the heat evolved as carbon monoxide is oxidized to carbon dioxide at the catalyst surface, without any heaters or external heating elements for the ambient air or catalytic element material. Upon comparison to a reference thermistor, relative increases in the temperature of the sensing thermistor correspond positively with an increased concentration of carbon monoxide in the ambient medium and are thus used as an indicator of the presence of carbon monoxide.

  10. Rubbing salt into wounded endothelium: sodium potentiates proatherogenic effects of TNF-α under non-uniform shear stress.

    PubMed

    Wild, J; Soehnlein, O; Dietel, B; Urschel, K; Garlichs, C D; Cicha, I

    2014-07-01

    Increased consumption of sodium is a risk factor for hypertension and cardiovascular diseases. In vivo studies indicated that high dietary sodium may have a direct negative influence on endothelium. We investigated the effects of high sodium on the endothelial activation during early steps of atherogenesis. Endothelial cells (HUVECs) grown in a model of arterial bifurcations were exposed to shear stress in the presence of normal or high (+ 30 mmol/l) sodium. Adherent THP-1 cells, and the adhesion molecule expression were quantified. Sodium channel blockers, pathways' inhibitors, and siRNA against tonicity-responsive enhancer binding protein (TonEBP) were used to identify the mechanisms of sodium effects on endothelium. ApoE-deficient mice on low-fat diet received water containing normal or high salt (8% w/v) for four weeks, and the influence of dietary salt on inflammatory cell adhesion in the common carotid artery and carotid bifurcation was measured by intravital microscopy. In vitro, high sodium dramatically increased the endothelial responsiveness to tumour necrosis factor-α under non-uniform shear stress. Sodium-induced increase in monocytic cell adhesion was mediated by reactive oxygen species and the endothelial nitric oxygen synthase, and was sensitive to the knockdown of TonEBP. The results were subsequently confirmed in the ApoE-deficient mice. As compared with normal-salt group, high-salt intake significantly enhanced the adhesion of circulating CD11b+ cells to carotid bifurcations, but not to the straight segment of common carotid artery. In conclusion, elevated sodium has a direct effect on endothelial activation under atherogenic shear stress in vitro and in vivo, and promotes the endothelial-leukocyte interactions even in the absence of increased lipid concentrations. PMID:24573382

  11. Effects of Non-Uniform Wall Heating on Thermal and Momentum Fields in a 3-Dimensional Urban Environment

    NASA Astrophysics Data System (ADS)

    Nazarian, N.; Kleissl, J. P.

    2014-12-01

    As urbanization progresses, microclimate modifications are also aggravated and the increasing environmental concerns call for more sophisticated methods of urban microclimate analysis. Comprehensive numerical simulations for a clear summer day in southern California are performed in a compact low-rise urban environment. The effect of realistic unsteady, non-uniform thermal forcing, that is caused by solar insolation and inter-building shadowing on thermal and flow conditions are analyzed based on Algebraic Wall-Modeled Large Eddy Simulation (LES) model. The urban thermal field is influenced by urban density, material properties and local weather conditions, as well as urban canyon flow. Urban canyon conditions are translated into vertical and horizontal bulk Richardson numbers indicating atmospheric instability and solar tilt with respect to the momentum forcing of the canyon vortex, respectively. The effect of roof heating is found to be critical on the vortex formation between buildings when the vertical bulk Richardson number is low. Variations of Convective Heat Transfer Coefficients (CHTCs) along building walls are studied and the street canyon ventilation performance is characterized by the mean of air exchange rate (ACH). It is found that volumetric air exchange from street canyons, as well as the distribution of heat transfer along the wall depends strongly on the three-dimensional orientation of the heated wall in relation to wind direction. For example, air removal increases by surface heating and is larger when the leeward wall is heated. In summary, we demonstrate the importance of considering complex realistic conditions on 3-dimensional thermal and momentum fields in Urban Environments.

  12. Quantifying the Distribution and Influence of Non-Uniform Bed Properties on Spatial Patterns of Turbidity in Shallow Coastal Bays

    NASA Astrophysics Data System (ADS)

    Wiberg, P.; Carr, J. A.; Safak, I.; Anutaliya, A.

    2014-12-01

    Increases in turbidity in shallow coastal bays typically occur in response to resuspension of bed sediment driven by the interaction between wind-generated waves and the bay bottom. The mass and grain size of resuspended sediment at any location in a bay are strongly controlled by local bed properties. This suggests that spatial variations in bed properties, such as grain size, porosity and erodibility, should be reflected in spatial patterns of turbidity. Unfortunately, knowledge of bed properties in coastal bays is typically sparse at best. In this study we address two related questions: 1) how best to estimate the spatial distribution of bed properties in shallow coastal bays; and 2) how does the spatial distribution of bed properties affect the spatial pattern of wave-driven turbidity? We explored these questions using field observations and the Delft3D coastal hydrodynamic and sediment transport model for a system of shallow coastal bays on Virginia's Atlantic coast. This system comprises bays of varying geometry with similar wind and tidal forcing. We found a strong relationship between water residence time and measured grain size. We leveraged the relationships between residence time and grain size fractions to map the spatial distribution of grain size throughout the system based on a recent mapping of residence times for the Virginia coastal bays. This spatially varying map of grain size was used as the initial bed conditions for 2-month-long runs of Delft3D forced with measured wind and tides. The resulting patterns of suspended sediment concentration (SSC) and turbidity differ dramatically from those obtained from simulations with an initially spatially homogeneous bed, with high wave-driven SSC near the mainland in the non-uniform case but high SSC near the inlets for the uniform case. The pre- and post-simulation bed properties are compared to each other and with measured bed properties to investigate how close the residence-time generated bed is to

  13. Effect of medium permeability anisotropy on the morphological evolution of two non-uniformities in a geochemical dissolution system

    NASA Astrophysics Data System (ADS)

    Lai, Keng-Hsin; Chen, Jui-Sheng; Liu, Chen-Wuing; Hsu, Shao-Yiu; Steefel, Carl

    2016-02-01

    The morphological evolutions of chemical dissolution fronts have attracted increasing interest in the field of the geological sciences and in industrial applications. Extensive research based on numerical simulations has been conducted to understand how various mechanisms and processes influence the morphological evolution of chemical dissolution fronts within geological media. Most researchers in previous studies have assumed the medium permeability to be isotropic for developing numerical models, despite isotropic geological media being uncommon in the real world. This study investigates the effect of medium permeability anisotropy on the morphological evolutions of two non-uniformities with higher permeability in a geochemical dissolution system. A series of numerical simulations are performed to evaluate the effect of medium permeability anisotropy on the morphological evolution of a chemical dissolution front. The simulation results indicate that the patterns of the dissolution reaction front are substantially affected by medium permeability anisotropy. An increase in the permeability anisotropy ratio, which is defined as the ratio of the permeability in the transverse direction to that in the longitudinal direction, enhances the dominance of the flow-focusing effect over the stabilizing or merging effect induced by diffusion/dispersion mechanism. Therefore, an increase in the permeability anisotropy ratio can increase the fingering length of the dissolution front or cause the dissolution front to have a more unstable pattern. By contrast, a reduction in the permeability anisotropy ratio will weaken the flow-focusing effect, thereby reducing the fingering length of the dissolution front or changing the front morphology such that it has a more stable status. The effect of the permeability anisotropy ratio on the morphological evolution tends to decrease when the Zhao number (negative dimensionless upstream pressure gradient) of the system increases. The

  14. A study to evaluate non-uniform phase maps in shape memory alloys using finite element method

    NASA Astrophysics Data System (ADS)

    Motte, Naren

    The unique thermo-mechanical behavior of Shape Memory Alloys (SMAs), such as their ability to recover the original shape upon heating or being able to tolerate large deformations without undergoing plastic transformations, makes them a good choice for actuators. This work studies their application in the aerospace and defense industries where SMA components can serve as release mechanisms for gates of enclosures that have to be deployed remotely. This work provides a novel approach in evaluating the stress and heat induced change of phase in a SMA, in terms of the transformation strain tensor. In particular, the FEA tool ANSYS has been used to perform a 2-D analysis of a Cu-Al-Zn-Mn SMA specimen undergoing a nontraditional loading path in two steps with stress and heating loads. In the first load step, tensile displacement is applied, followed by the second load step in which the specimen is heated while the end displacements are held constant. A number of geometric configurations are examined under the two step loading path. Strain results are used to calculate transformation strain which provides a quantitative measure of phase at a material point; when transformation strain is zero, the material point is either twinned martensite, or austenite depending on the temperature. Transformation strain value of unity corresponds to detwinned martensite. A value between zero and one indicates mixed phase. In this study, through two step loading in conjunction with transformation strain calculations, a method for mapping transient non-uniform distribution of phases in an SMA is introduced. Ability to obtain drastically different phase distributions under same loading path by modifying the geometry is demonstrated. The failure behavior of SMAs can be designed such that the load level the crack initiates and the path it propagates can be customized.

  15. Numerical study of the ferrofluid flow and heat transfer through a rectangular duct in the presence of a non-uniform transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Aminfar, H.; Mohammadpourfard, M.; Ahangar Zonouzi, S.

    2013-02-01

    This paper investigates numerically the hydro-thermal characteristics of a ferrofluid (water and 4 vol% Fe3O4) in a vertical rectangular duct which is exposed to a non-uniform transverse magnetic field generated by an electric current going through a wire located parallelly under the duct. The two phase mixture model and the control volume technique have been used to study the flow. The results show that applying the aforementioned magnetic field increases the Nusselt number and friction factor and also creates a pair of vortices that enhances heat transfer and prevents sedimentation of nano-particles. Furthermore, unlike the axial non-uniform magnetic field, the increase of the Nusselt number for the transverse magnetic field is considerable in all length along the duct and it is also concluded that with increasing the Reynolds number, the effect of the transverse non-uniform magnetic field on the Nusselt number is more than that of the axial non-uniform magnetic field.

  16. Comparison of Uniform and Non-uniform Water Flux Density Approaches Applied on a Mathematical Model of Heat Transfer and Solidification for a Continuous Casting of Round Billets

    NASA Astrophysics Data System (ADS)

    Assuncao, Charles Sostenes; Tavares, Roberto Parreiras; Oliveira, Guilherme; Pereira, Luiz Carlos

    2015-02-01

    In the present work, the water flux densities of nozzles with flat jet and full cone jet were experimentally measured using an apparatus in industrial scale that reproduces the secondary cooling of the continuous casting of round billets of Vallourec Tubos do Brasil. A mathematical function was defined to express the water flux density in both longitudinal and angular directions of the strand. A mathematical model for heat transfer and solidification for the continuous casting of round billets was developed applying the experimental water flux density profile, establishing a non-uniform water distribution approach. The mathematical model was validated by experimental measurements of the billet superficial temperature, performed at the industrial plant. The results of the mathematical model using both uniform and non-uniform water flux density approaches were compared. The non-uniform water distribution approach enabled to identify important variations of the heat transfer coefficients and the billet temperatures, especially in the first cooling zones where the steel temperature is higher, and to assess more accurately the local effects of the water distribution on the thermal behavior of the strand. The non-uniform water flux density approach applied to the mathematical model was a useful and more accurate tool to improve the comprehension of the thermal behavior of the steel along the secondary cooling.

  17. An Analysis of Non-Uniform Stress States in Finite Thin Film/Substrate System: The Need of Full-Field Curvature Measurements

    ERIC Educational Resources Information Center

    Ngo, Duc Minh

    2009-01-01

    Current methodologies used for the inference of thin film stresses through curvatures are strictly restricted to stress and curvature states which are assumed to remain uniform over the entire film/substrate system. In this dissertation, we extend these methodologies to non-uniform stress and curvature states for the single layer of thin film or…

  18. A new approach to the optimisation of non-uniform sampling schedules for use in the rapid acquisition of 2D NMR spectra of small molecules.

    PubMed

    Sidebottom, Philip J

    2016-08-01

    Non-uniform sampling allows the routine, rapid acquisition of 2D NMR data. When the number of points in the NUS schedule is low, the quality of the data obtained is very dependent of the schedule used. A simple proceedure for finding optimium schedules has been developed and is demonstrated for the multiplicity edited HSQC experiment. PMID:27160788

  19. Three-point compact finite difference scheme on non-uniform meshes for the time-fractional Black-Scholes equation

    NASA Astrophysics Data System (ADS)

    Dimitrov, Yuri M.; Vulkov, Lubin G.

    2015-11-01

    We construct a three-point compact finite difference scheme on a non-uniform mesh for the time-fractional Black-Scholes equation. We show that for special graded meshes used in finance, the Tavella-Randall and the quadratic meshes the numerical solution has a fourth-order accuracy in space. Numerical experiments are discussed.

  20. A comparison of intensity modulated x-ray therapy to intensity modulated proton therapy for the delivery of non-uniform dose distributions

    NASA Astrophysics Data System (ADS)

    Flynn, Ryan

    2007-12-01

    The distribution of biological characteristics such as clonogen density, proliferation, and hypoxia throughout tumors is generally non-uniform, therefore it follows that the optimal dose prescriptions should also be non-uniform and tumor-specific. Advances in intensity modulated x-ray therapy (IMXT) technology have made the delivery of custom-made non-uniform dose distributions possible in practice. Intensity modulated proton therapy (IMPT) has the potential to deliver non-uniform dose distributions as well, while significantly reducing normal tissue and organ at risk dose relative to IMXT. In this work, a specialized treatment planning system was developed for the purpose of optimizing and comparing biologically based IMXT and IMPT plans. The IMXT systems of step-and-shoot (IMXT-SAS) and helical tomotherapy (IMXT-HT) and the IMPT systems of intensity modulated spot scanning (IMPT-SS) and distal gradient tracking (IMPT-DGT), were simulated. A thorough phantom study was conducted in which several subvolumes, which were contained within a base tumor region, were boosted or avoided with IMXT and IMPT. Different boosting situations were simulated by varying the size, proximity, and the doses prescribed to the subvolumes, and the size of the phantom. IMXT and IMPT were also compared for a whole brain radiation therapy (WBRT) case, in which a brain metastasis was simultaneously boosted and the hippocampus was avoided. Finally, IMXT and IMPT dose distributions were compared for the case of non-uniform dose prescription in a head and neck cancer patient that was based on PET imaging with the Cu(II)-diacetyl-bis(N4-methylthiosemicarbazone (Cu-ATSM) hypoxia marker. The non-uniform dose distributions within the tumor region were comparable for IMXT and IMPT. IMPT, however, was capable of delivering the same non-uniform dose distributions within a tumor using a 180° arc as for a full 360° rotation, which resulted in the reduction of normal tissue integral dose by a factor of

  1. Simple estimation of induced electric fields in nervous system tissues for human exposure to non-uniform electric fields at power frequency

    NASA Astrophysics Data System (ADS)

    Tarao, Hiroo; Miyamoto, Hironobu; Korpinen, Leena; Hayashi, Noriyuki; Isaka, Katsuo

    2016-06-01

    Most results regarding induced current in the human body related to electric field dosimetry have been calculated under uniform field conditions. We have found in previous work that a contact current is a more suitable way to evaluate induced electric fields, even in the case of exposure to non-uniform fields. If the relationship between induced currents and external non-uniform fields can be understood, induced electric fields in nervous system tissues may be able to be estimated from measurements of ambient non-uniform fields. In the present paper, we numerically calculated the induced electric fields and currents in a human model by considering non-uniform fields based on distortion by a cubic conductor under an unperturbed electric field of 1 kV m‑1 at 60 Hz. We investigated the relationship between a non-uniform external electric field with no human present and the induced current through the neck, and the relationship between the current through the neck and the induced electric fields in nervous system tissues such as the brain, heart, and spinal cord. The results showed that the current through the neck can be formulated by means of an external electric field at the central position of the human head, and the distance between the conductor and the human model. As expected, there is a strong correlation between the current through the neck and the induced electric fields in the nervous system tissues. The combination of these relationships indicates that induced electric fields in these tissues can be estimated solely by measurements of the external field at a point and the distance from the conductor.

  2. Simple estimation of induced electric fields in nervous system tissues for human exposure to non-uniform electric fields at power frequency.

    PubMed

    Tarao, Hiroo; Miyamoto, Hironobu; Korpinen, Leena; Hayashi, Noriyuki; Isaka, Katsuo

    2016-06-21

    Most results regarding induced current in the human body related to electric field dosimetry have been calculated under uniform field conditions. We have found in previous work that a contact current is a more suitable way to evaluate induced electric fields, even in the case of exposure to non-uniform fields. If the relationship between induced currents and external non-uniform fields can be understood, induced electric fields in nervous system tissues may be able to be estimated from measurements of ambient non-uniform fields. In the present paper, we numerically calculated the induced electric fields and currents in a human model by considering non-uniform fields based on distortion by a cubic conductor under an unperturbed electric field of 1 kV m(-1) at 60 Hz. We investigated the relationship between a non-uniform external electric field with no human present and the induced current through the neck, and the relationship between the current through the neck and the induced electric fields in nervous system tissues such as the brain, heart, and spinal cord. The results showed that the current through the neck can be formulated by means of an external electric field at the central position of the human head, and the distance between the conductor and the human model. As expected, there is a strong correlation between the current through the neck and the induced electric fields in the nervous system tissues. The combination of these relationships indicates that induced electric fields in these tissues can be estimated solely by measurements of the external field at a point and the distance from the conductor. PMID:27222929

  3. Carbon copy deaths: carbon monoxide gas chamber.

    PubMed

    Patel, F

    2008-08-01

    The news media can exert a powerful influence over suicidal behaviour. It has been observed that like-minded individuals are able to preplan a group suicide method using modern communication technology in the form of websites and online chatrooms and mobile phone texting. A case of carbon monoxide (CO) poisoning is presented to illustrate the recent phenomenon of cyber suicides by suffocation from a burning barbecue (charcoal burner) in 'gas chamber' conversions. Although barbecues (BBQ) are very popular in Britain and widely available, there have been relatively few reported cases of copycat deaths from CO gas suffocation. PMID:18586213

  4. A discriminative model-constrained EM approach to 3D MRI brain tissue classification and intensity non-uniformity correction

    NASA Astrophysics Data System (ADS)

    Wels, Michael; Zheng, Yefeng; Huber, Martin; Hornegger, Joachim; Comaniciu, Dorin

    2011-06-01

    We describe a fully automated method for tissue classification, which is the segmentation into cerebral gray matter (GM), cerebral white matter (WM), and cerebral spinal fluid (CSF), and intensity non-uniformity (INU) correction in brain magnetic resonance imaging (MRI) volumes. It combines supervised MRI modality-specific discriminative modeling and unsupervised statistical expectation maximization (EM) segmentation into an integrated Bayesian framework. While both the parametric observation models and the non-parametrically modeled INUs are estimated via EM during segmentation itself, a Markov random field (MRF) prior model regularizes segmentation and parameter estimation. Firstly, the regularization takes into account knowledge about spatial and appearance-related homogeneity of segments in terms of pairwise clique potentials of adjacent voxels. Secondly and more importantly, patient-specific knowledge about the global spatial distribution of brain tissue is incorporated into the segmentation process via unary clique potentials. They are based on a strong discriminative model provided by a probabilistic boosting tree (PBT) for classifying image voxels. It relies on the surrounding context and alignment-based features derived from a probabilistic anatomical atlas. The context considered is encoded by 3D Haar-like features of reduced INU sensitivity. Alignment is carried out fully automatically by means of an affine registration algorithm minimizing cross-correlation. Both types of features do not immediately use the observed intensities provided by the MRI modality but instead rely on specifically transformed features, which are less sensitive to MRI artifacts. Detailed quantitative evaluations on standard phantom scans and standard real-world data show the accuracy and robustness of the proposed method. They also demonstrate relative superiority in comparison to other state-of-the-art approaches to this kind of computational task: our method achieves average

  5. The fluid dynamics of work transfer in the non-uniform viscous rotating flow within a Tesla disc turbomachine

    NASA Astrophysics Data System (ADS)

    Guha, Abhijit; Sengupta, Sayantan

    2014-03-01

    In this article, the fluid dynamics of work transfer within the narrow spacing (usually of the order of 100 μm) of multiple concentric discs of a Tesla disc turbomachine (turbine or compressor) has been analysed theoretically and computationally. Both the overall work transfer and its spatial development have been considered. It has been established that the work transfer mechanism in a Tesla disc turbomachine is very different from that in a conventional turbomachine, and the formulation of the Euler's work equation for the disc turbomachine contains several conceptual subtleties because of the existence of complex, three dimensional, non-uniform, viscous flow features. A work equivalence principle has been enunciated, which establishes the equality between the magnitudes of work transfer determined rigorously from two different approaches—one based on the shear stress acting on the disc surfaces and the other based on the change in angular momentum of the fluid. Care is needed in identifying the shear stress components that are responsible for the generation or absorption of useful power. It is shown from the Reynolds transport theorem that mass-flow-averaged tangential velocities (as opposed to the normally used area-averaged values) must be used in determining the change in angular momentum; the calculation has to be carefully formulated since both radial velocity (that determines throughput) and tangential velocity (that generates torque) depend strongly on the coordinate perpendicular to the disc surfaces. The principle of work transfer has been examined both in the absolute and relative frames of reference, revealing the subtle role played by Coriolis force. The concept of a new non-dimensional quantity called the torque potential fraction (Δ tilde H) is introduced. The value of Δ tilde H at any radial position increases with a decrease in inter-disc spacing. The computational fluid dynamic analysis shows that, for small value of inter-disc spacing and

  6. An Analytical Model for Non-Uniform Magnetic Field Effects on Two-Dimensional Laminar Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Calvert, M. E.; Baker, J.; Saito, K.; VanderWal, R. L.

    2001-01-01

    In 1846, Michael Faraday found that permanent magnets could cause candle flames to deform into equatorial disks. He believed that the change in flame shape was caused by the presence of charged particles within the flames interacting with the magnetic fields. Later researchers found that the interaction between the flame ions and the magnetic fields were much too small to cause the flame deflection. Through a force analysis, von Engel and Cozens showed that the change in the flame shape could be attributed to the diamagnetic flame gases in the paramagnetic atmosphere. Paramagnetism occurs in materials composed of atoms with permanent magnetic dipole moments. In the presence of magnetic field gradients, the atoms align with the magnetic field and are drawn into the direction of increasing magnetic field. Diamagnetism occurs when atoms have no net magnetic dipole moment. In the presence of magnetic gradient fields, diamagnetic substances are repelled towards areas of decreasing magnetism. Oxygen is an example of a paramagnetic substance. Nitrogen, carbon monoxide and dioxide, and most hydrocarbon fuels are examples of diamagnetic substances. In order to evaluate the usefulness of these magnets in altering flame behavior, a study has been undertaken to develop an analytical model to describe the change in the flame length of a laminar diffusion jet in the presence of a nonuniform magnetic field.

  7. An exact formulation of k-distribution methods in non-uniform gaseous media and its approximate treatment within the Multi-Spectral framework

    NASA Astrophysics Data System (ADS)

    ANDRE, Frédéric; HOU, Longfeng; SOLOVJOV, Vladimir P.

    2016-01-01

    The main restriction of k-distribution approaches for applications in radiative heat transfer in gaseous media arises from the use of a scaling or correlation assumption to treat non-uniform situations. It is shown that those cases can be handled exactly by using a multidimensional k-distribution that addresses the problem of spectral correlations without using any simplifying assumptions. Nevertheless, the approach cannot be suggested for engineering applications due to its computational cost. Accordingly, a more efficient method, based on the so-called Multi-Spectral Framework, is proposed to approximate the previous exact formulation. The model is assessed against reference LBL calculations and shown to outperform usual k-distribution approaches for radiative heat transfer in non-uniform media.

  8. Quantifying physical structure changes and non-uniform water flow in cattle manure during dry anaerobic digestion process at lab scale: Implication for biogas production.

    PubMed

    André, L; Durante, M; Pauss, A; Lespinard, O; Ribeiro, T; Lamy, E

    2015-09-01

    The aim of this study was to investigate and quantify non-uniform water flow during dry AD and its implication for biogas production. Laboratory tracer experiments were performed on cattle manure over the course of AD. The evolution of the permeability, the dry bulk density, the dry porosity, the total and volatile solid contents of cattle manure at different stages of AD, revealed waste structure changes, impacting water flow and methane production. Tracer experiments and numerical modeling performed by using a physical non-equilibrium model indicated non-uniform preferential flow patterns during degradation. According to literature, the increase of inoculum recirculation frequency improved methane production rate. However, these results demonstrated that this improvement occurs only at the beginning of manure degradation. After 19 days of degradation the inoculum recirculation and the flow patterns modification had no effect on methane production rate. PMID:26094191

  9. Lattice Boltzmann Simulation of Mixed Convection Heat Transfer in a Driven Cavity with Non-uniform Heating of the Bottom Wall

    NASA Astrophysics Data System (ADS)

    Soufiene, Bettaibi; Ezeddine, Sediki; Frédéric, Kuznik; Sauro, Succi

    2015-01-01

    The goal of this article is to study numerically the mixed convection in a differentially heated lid-driven cavity with non-uniform heating of the bottom wall. The velocity field is solved by a hybrid scheme with multiple relaxation time Lattice Boltzmann (MRT-LBM) model, while the temperature field is obtained by resolution of the energy balance equation using the finite difference method (FDM). First, the model is checked and validated using data from the literature. Validation of the present results with those available in the literature shows a good agreement. A good efficiency in time simulation is confirmed. Thereafter, the model has been applied to mixed convection in a driven cavity with non-uniform heating wall at the fixed Grashof number Gr = 106. It is found that, the heat transfer is weakened as the Richardson number is augmented. For Gr = 106, we note the appearance of secondary vortices at different positions of the cavity corners.

  10. Large deflections of non-prismatic nonlinearly elastic cantilever beams subjected to non-uniform continuous load and a concentrated load at the free end

    NASA Astrophysics Data System (ADS)

    Brojan, Miha; Cebron, Matjaz; Kosel, Franc

    2012-06-01

    This work studies large deflections of slender, non-prismatic cantilever beams subjected to a combined loading which consists of a non-uniformly distributed continuous load and a concentrated load at the free end of the beam. The material of the cantilever is assumed to be nonlinearly elastic. Different nonlinear relations between stress and strain in tensile and compressive domain are considered. The accuracy of numerical solutions is evaluated by comparing them with results from previous studies and with a laboratory experiment.

  11. The influence of local effects on thermal sensation under non-uniform environmental conditions--gender differences in thermophysiology, thermal comfort and productivity during convective and radiant cooling.

    PubMed

    Schellen, L; Loomans, M G L C; de Wit, M H; Olesen, B W; van Marken Lichtenbelt, W D

    2012-09-10

    Applying high temperature cooling concepts, i.e. high temperature cooling (T(supply) is 16-20°C) HVAC systems, in the built environment allows the reduction in the use of (high quality) energy. However, application of high temperature cooling systems can result in whole body and local discomfort of the occupants. Non-uniform thermal conditions, which may occur due to application of high temperature cooling systems, can be responsible for discomfort. Contradictions in literature exist regarding the validity of the often used predicted mean vote (PMV) index for both genders, and the index is not intended for evaluating the discomfort due to non-uniform environmental conditions. In some cases, however, combinations of local and general discomfort factors, for example draught under warm conditions, may not be uncomfortable. The objective of this study was to investigate gender differences in thermophysiology, thermal comfort and productivity in response to thermal non-uniform environmental conditions. Twenty healthy subjects (10 males and 10 females, age 20-29 years) were exposed to two different experimental conditions: a convective cooling situation (CC) and a radiant cooling situation (RC). During the experiments physiological responses, thermal comfort and productivity were measured. The results show that under both experimental conditions the actual mean thermal sensation votes significantly differ from the PMV-index; the subjects are feeling colder than predicted. Furthermore, the females are more uncomfortable and dissatisfied compared to the males. For females, the local sensations and skin temperatures of the extremities have a significant influence on whole body thermal sensation and are therefore important to consider under non-uniform environmental conditions. PMID:22877870

  12. A non-uniform three-gap buncher cavity with suppression of transverse-electromagnetic mode leakage in the triaxial klystron amplifier

    SciTech Connect

    Qi, Zumin; Zhang, Jun Zhong, Huihuang; Zhu, Danni; Qiu, Yongfeng

    2014-01-15

    The triaxial klystron amplifier is an efficient high power relativistic klystron amplifier operating at high frequencies due to its coaxial structure with large radius. However, the coaxial structures result in coupling problems among the cavities as the TEM mode is not cut-off in the coaxial tube. Therefore, the suppression of the TEM mode leakage, especially the leakage from the buncher cavity to the input cavity, is crucial in the design of a triaxial klystron amplifier. In this paper, a non-uniform three-gap buncher cavity is proposed to suppress the TEM mode leakage. The cold cavity analysis shows that the non-uniform three-gap buncher cavity can significantly suppress the TEM mode generation compared to a uniform three-gap buncher cavity. Particle-in-cell simulation shows that the power leakage to the input cavity is less than 1.5‰ of the negative power in the buncher cavity and the buncher cavity can efficiently modulate an intense relativistic electron beam free of self-oscillations. A fundamental current modulation depth of 117% is achieved by employing the proposed non-uniform buncher cavity into an X-band triaxial amplifier, which results in the high efficiency generation of high power microwave.

  13. Non-uniformity correction of human brain imaging at high field by RF field mapping of B1+ and B1-

    NASA Astrophysics Data System (ADS)

    Watanabe, Hidehiro; Takaya, Nobuhiro; Mitsumori, Fumiyuki

    2011-10-01

    A new method of non-uniform image correction is proposed. Image non-uniformity is originated from the spatial distribution of RF transmission and reception fields, represented as B1+ and B1-, respectively. In our method, B1+ mapping was performed invivo by a phase method. In B1- mapping, images with multiple TEs were acquired with a multi-echo adiabatic spin echo (MASE) sequence which enables homogeneous excitation. By T2 fitting of these images an M0 map ( M0MASE) was obtained, in which signal intensity was expressed as the product of B1- and M0(1-e). The ratio of this M0MASE map to the B1+ map showed a similar spatial pattern in different human brains. These ratios of M0MASE to B1+ in 24 subjects were averaged and then fitted with a spatially polynomial function to obtain a ratio map of B1-/B1+(α). Uniform image was achieved in spin echo (SE), MASE and inversion recovery turboFLASH (IRTF) images using measured B1+ and calculated B1- by αB1+. Water fractions in gray and white matters obtained from the M0 images corrected by this method were in good agreement with previously reported values. From these experimental results, the proposed method of non-uniformity correction is validated at 4.7 T imaging.

  14. Important role of the non-uniform Fe distribution for the ferromagnetism in group-IV-based ferromagnetic semiconductor GeFe

    SciTech Connect

    Wakabayashi, Yuki K.; Ohya, Shinobu; Ban, Yoshisuke; Tanaka, Masaaki

    2014-11-07

    We investigate the growth-temperature dependence of the properties of the group-IV-based ferromagnetic semiconductor Ge{sub 1−x}Fe{sub x} films (x = 6.5% and 10.5%), and reveal the correlation of the magnetic properties with the lattice constant, Curie temperature (T{sub C}), non-uniformity of Fe atoms, stacking-fault defects, and Fe-atom locations. While T{sub C} strongly depends on the growth temperature, we find a universal relationship between T{sub C} and the lattice constant, which does not depend on the Fe content x. By using the spatially resolved transmission-electron diffractions combined with the energy-dispersive X-ray spectroscopy, we find that the density of the stacking-fault defects and the non-uniformity of the Fe concentration are correlated with T{sub C}. Meanwhile, by using the channeling Rutherford backscattering and particle-induced X-ray emission measurements, we clarify that about 15% of the Fe atoms exist on the tetrahedral interstitial sites in the Ge{sub 0.935}Fe{sub 0.065} lattice and that the substitutional Fe concentration is not correlated with T{sub C}. Considering these results, we conclude that the non-uniformity of the Fe concentration plays an important role in determining the ferromagnetic properties of GeFe.

  15. Thermoelastic analysis of non-uniform pressurized functionally graded cylinder with variable thickness using first order shear deformation theory(FSDT) and perturbation method

    NASA Astrophysics Data System (ADS)

    Khoshgoftar, M. J.; Mirzaali, M. J.; Rahimi, G. H.

    2015-11-01

    Recently application of functionally graded materials(FGMs) have attracted a great deal of interest. These materials are composed of various materials with different micro-structures which can vary spatially in FGMs. Such composites with varying thickness and non-uniform pressure can be used in the aerospace engineering. Therefore, analysis of such composite is of high importance in engineering problems. Thermoelastic analysis of functionally graded cylinder with variable thickness under non-uniform pressure is considered. First order shear deformation theory and total potential energy approach is applied to obtain the governing equations of non-homogeneous cylinder. Considering the inner and outer solutions, perturbation series are applied to solve the governing equations. Outer solution for out of boundaries and more sensitive variable in inner solution at the boundaries are considered. Combining of inner and outer solution for near and far points from boundaries leads to high accurate displacement field distribution. The main aim of this paper is to show the capability of matched asymptotic solution for different non-homogeneous cylinders with different shapes and different non-uniform pressures. The results can be used to design the optimum thickness of the cylinder and also some properties such as high temperature residence by applying non-homogeneous material.

  16. On the increase of the "non-uniform" scaling of the magnetic field variations before the Mw9.0 earthquake in Japan in 2011

    NASA Astrophysics Data System (ADS)

    Skordas, E. S.

    2014-06-01

    By applying Detrended Fluctuation Analysis (DFA) to the time series of the geomagnetic data recorded at three measuring stations in Japan, Rong et al. in 2012 recently reported that anomalous magnetic field variations were identified well before the occurrence of the disastrous Tohoku Mw9.0 earthquake that occurred on 11 March 2011 in Japan exhibiting increased "non-uniform" scaling behavior. Here, we provide an explanation for the appearance of this increase of "non-uniform" scaling on the following grounds: These magnetic field variations are the ones that accompany the electric field variations termed Seismic Electric Signals (SES) activity which have been repeatedly reported that precede major earthquakes. DFA as well as multifractal DFA reveal that the latter electric field variations exhibit scaling behavior as shown by analyzing SES activities observed before major earthquakes in Greece. Hence, when these variations are superimposed on a background of pseudosinusoidal trend, their long range correlation properties—quantified by DFA—are affected resulting in an increase of the "non-uniform" scaling behavior. The same is expected to hold for the former magnetic field variations. This explanation is strengthened by recent findings showing that the fluctuations of the order parameter of seismicity exhibited an unprecedented minimum almost two months before the Tohoku earthquake occurrence which is characteristic for an almost simultaneous emission of Seismic Electric Signals activity.

  17. Analytical solution to 3D SPECT reconstruction with non-uniform attenuation, scatter, and spatially-variant resolution variation for variable focal-length fan-beam collimators

    NASA Astrophysics Data System (ADS)

    Wen, Junhai; Lu, Hongbing; Li, Tianfang; Liang, Zhengrong

    2003-05-01

    In the past decades, analytical (non-iterative) methods have been extensively investigated and developed for the reconstruction of three-dimensional (3D) single-photon emission computed tomography (SPECT). However, it becomes possible only recently when the exact analytic non-uniform attenuation reconstruction algorithm was derived. Based on the explicit inversion formula for the attenuated Radon transform discovered by Novikov (2000), we extended the previous researches of inverting the attenuated Radon transform of parallel-beam collimation geometry to fan-beam and variable focal-length fan-beam (VFF) collimators and proposed an efficient, analytical solution to 3D SPECT reconstruction with VFF collimators, which compensates simultaneously for non-uniform attenuation, scatter, and spatially-variant or distance-dependent resolution variation (DDRV), as well as suppression of signal-dependent non-stationary Poisson noise. In this procedure, to avoid the reconstructed images being corrupted by the presence of severe noise, we apply a Karhune-Loève (K-L) domain adaptive Wiener filter, which accurately treats the non-stationary Poisson noise. The scatter is then removed by our scatter estimation method, which is based on the energy spectrum and modified from the triple-energy-window acquisition protocol. For the correction of DDRV, a distance-dependent deconvolution is adapted to provide a solution that realistically characterizes the resolution kernel in a real SPECT system. Finally image is reconstructed using our VFF non-uniform attenuation inversion formula.

  18. On the increase of the "non-uniform" scaling of the magnetic field variations before the M(w)9.0 earthquake in Japan in 2011.

    PubMed

    Skordas, E S

    2014-06-01

    By applying Detrended Fluctuation Analysis (DFA) to the time series of the geomagnetic data recorded at three measuring stations in Japan, Rong et al. in 2012 recently reported that anomalous magnetic field variations were identified well before the occurrence of the disastrous Tohoku Mw9.0 earthquake that occurred on 11 March 2011 in Japan exhibiting increased "non-uniform" scaling behavior. Here, we provide an explanation for the appearance of this increase of "non-uniform" scaling on the following grounds: These magnetic field variations are the ones that accompany the electric field variations termed Seismic Electric Signals (SES) activity which have been repeatedly reported that precede major earthquakes. DFA as well as multifractal DFA reveal that the latter electric field variations exhibit scaling behavior as shown by analyzing SES activities observed before major earthquakes in Greece. Hence, when these variations are superimposed on a background of pseudosinusoidal trend, their long range correlation properties-quantified by DFA-are affected resulting in an increase of the "non-uniform" scaling behavior. The same is expected to hold for the former magnetic field variations. This explanation is strengthened by recent findings showing that the fluctuations of the order parameter of seismicity exhibited an unprecedented minimum almost two months before the Tohoku earthquake occurrence which is characteristic for an almost simultaneous emission of Seismic Electric Signals activity. PMID:24985445

  19. Modified Omega-k Algorithm for High-Speed Platform Highly-Squint Staggered SAR Based on Azimuth Non-Uniform Interpolation

    PubMed Central

    Zeng, Hong-Cheng; Chen, Jie; Liu, Wei; Yang, Wei

    2015-01-01

    In this work, the staggered SAR technique is employed for high-speed platform highly-squint SAR by varying the pulse repetition interval (PRI) as a linear function of range-walk. To focus the staggered SAR data more efficiently, a low-complexity modified Omega-k algorithm is proposed based on a novel method for optimal azimuth non-uniform interpolation, avoiding zero padding in range direction for recovering range cell migration (RCM) and saving in both data storage and computational load. An approximate model on continuous PRI variation with respect to sliding receive-window is employed in the proposed algorithm, leaving a residual phase error only due to the effect of a time-varying Doppler phase caused by staggered SAR. Then, azimuth non-uniform interpolation (ANI) at baseband is carried out to compensate the azimuth non-uniform sampling (ANS) effect resulting from continuous PRI variation, which is further followed by the modified Omega-k algorithm. The proposed algorithm has a significantly lower computational complexity, but with an equally effective imaging performance, as shown in our simulation results. PMID:25664433

  20. Ambient Concentrations of Carbon Monoxide

    EPA Science Inventory

    This indicator presents trends in ambient carbon monoxide concentrations across the U.S. from 1980 to 2009. By tracking ambient carbon monoxide (CO) – a criteria pollutant with the potential to cause cardiovascular and neurological damage – this dataset shows how a...

  1. Carbon Monoxide Sensor

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The fuel cell is a system which employs an electrochemical process to convert gases- J such as hydrogen and oxygen directly into electricity. Under NASA sponsorship, GE's Aircraft Equipment Division developed fuel cells to supply electrical power for the Gemini and Biosatellite spacecraft of the sixties and is currently working on advanced fuel cell development. This long-term effort has resulted in a series of spinoff applications using the same general technology for a variety of purposes, among them the recently marketed Dosimeter. The Dosimeter is designed to help users meet safety requirements for industrial atmospheres, as specified by the Occupational Safety and Health Administration and other regulatory agencies. The compact, pocket-sized sensor measures personnel exposure to carbon monoxide and provides both a visual and an audible alarm if the concentration of the gas exceeds present levels. The Dosimeter offers substantial improvement in measuring accuracy over earlier warning indicators.

  2. Conjugate heat transfer of laminar mixed convection of a nanofluid through an inclined tube with circumferentially non-uniform heating

    PubMed Central

    2011-01-01

    Laminar mixed convection of a nanofluid consisting of water and Al2O3 in an inclined tube with heating at the top half surface of a copper tube has been studied numerically. The bottom half of the tube wall is assumed to be adiabatic (presenting a tube of a solar collector). Heat conduction mechanism through the tube wall is considered. Three-dimensional governing equations with using two-phase mixture model have been solved to investigate hydrodynamic and thermal behaviours of the nanofluid over wide range of nanoparticle volume fractions. For a given nanoparticle mean diameter the effects of nanoparticle volume fractions on the hydrodynamics and thermal parameters are presented and discussed at different Richardson numbers and different tube inclinations. Significant augmentation on the heat transfer coefficient as well as on the wall shear stress is seen. PMID:21711867

  3. Conjugate heat transfer of laminar mixed convection of a nanofluid through an inclined tube with circumferentially non-uniform heating.

    PubMed

    Allahyari, Shahriar; Behzadmehr, Amin; Sarvari, Seyed Masoud Hosseini

    2011-01-01

    Laminar mixed convection of a nanofluid consisting of water and Al2O3 in an inclined tube with heating at the top half surface of a copper tube has been studied numerically. The bottom half of the tube wall is assumed to be adiabatic (presenting a tube of a solar collector). Heat conduction mechanism through the tube wall is considered. Three-dimensional governing equations with using two-phase mixture model have been solved to investigate hydrodynamic and thermal behaviours of the nanofluid over wide range of nanoparticle volume fractions. For a given nanoparticle mean diameter the effects of nanoparticle volume fractions on the hydrodynamics and thermal parameters are presented and discussed at different Richardson numbers and different tube inclinations. Significant augmentation on the heat transfer coefficient as well as on the wall shear stress is seen. PMID:21711867

  4. Use of high-granularity CdZnTe pixelated detectors to correct response non-uniformities caused by defects in crystals

    NASA Astrophysics Data System (ADS)

    Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; De Geronimo, G.; Eger, J.; Emerick, A.; Fried, J.; Hossain, A.; Roy, U.; Salwen, C.; Soldner, S.; Vernon, E.; Yang, G.; James, R. B.

    2016-01-01

    Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm3 pixelated detectors, fabricated with conventional pixel patterns with progressively smaller pixel sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices.

  5. Metastable inhomogeneous vortex configuration with non-uniform filling fraction inside a blind hole array patterned in a BSCCO single crystal and concentrating magnetic flux inside it

    NASA Astrophysics Data System (ADS)

    Shaw, Gorky; Banerjee, S. S.; Tamegai, T.; Suderow, Hermann

    2016-06-01

    Using magneto-optical imaging, we map the local magnetic field distribution inside a hexagonally ordered array of blind holes patterned in BSCCO single crystals. The nature of the spatial distribution of local magnetic field and shielding currents across the array reveals the presence of a non-uniform vortex configuration partially matched with the blind holes at sub-matching fields. We observe that the filling fraction is different in two different regions of the array. The mean vortex configuration within the array is described as a patchy vortex configuration with the patches having different mean filling fraction. The patchy nature of the vortex configuration is more pronounced at partial filling of the array at low fields while the configuration becomes more uniform with a unique filling fraction at higher fields. The metastable nature of this patchy vortex configuration is revealed by the application of magnetic field pulses of fixed height or individual pulses of varying height to the array. The metastability of the vortex configuration allows a relatively easy way of producing flux reorganization and flux focusing effects within the blind hole array. The effect of the magnetic field pulses modifies the vortex configuration within the array and produces a uniform enhancement in the shielding current around the patterned array edges. The enhanced shielding current concentrates magnetic flux within the array by driving vortices away from the edges and towards the center of the array. The enhanced shielding current also prevents the uninhibited entry of vortices into the array. We propose that the metastable patchy vortex configuration within the blind hole array is due to a non-uniform pinning landscape leading to non-uniform filling of individual blind holes.

  6. Evaluation of the partial flip angle spin echo method to improve non-uniformity in T1-weighted imaging with the 3-tesla MRI

    NASA Astrophysics Data System (ADS)

    Watanabe, Youhei; Tsuzaka, Masatoshi; Ishibashi, Kazuto; Sakurai, Yasuo

    2008-03-01

    The higher signal-to-noise ratio (SNR) of 3-Tesla magnetic resonance imaging (3T MRI) contributes to an improvement in the spatial and temporal resolution. However, T1-weighted images of the brain obtained by the spin-echo (SE) method using 3T MRI are unsuitable for clinical use because of the inhomogeneity of the radio frequency (RF) field B1 non-uniformity. And it is clear by SE method. In addition, the prolongation of the longitudinal relaxation time (T1) of most tissues leads to a decrease in the T1 contrast. Therefore, many hospitals that utilize 3TMRI use the GRE method instead of the SE method in order to obtain an adequate T1 contrast, as can be obtained using FLASH (fast low angle shot), and high uniformity of images. Further, many studies have been performed to improve the non uniformity using techniques such as spatial presaturation. However, when filters are used, the high intensity of the influence in susceptible regions, signal deficits, and original contrast are lost, and a distortion can be clearly observed when the GRE method is used. Therefore, we obtained the T1-weighted images by using the partial flip angle SE method instead of the GRE method or SE method. We attempted to improve the image non-uniformity by using the partial flip angle SE method. Using this method, we could improve the image uniformity and also realize an adequate T1 contrast. As a result, the uniformity was found to improve by 6% and it became 82.6% at 110°. These results indicate that the use of the partial flip angle SE method is effective for obtaining adequate uniformity in the T1-weighted images of the brain.

  7. Effects of non-uniform heat source and magnetic field on the flow and heat transfer over a nonlinearly stretching sheet with suction

    NASA Astrophysics Data System (ADS)

    Isa, Siti Suzilliana Putri Mohamed; Arifin, Norihan Md; Bachok@Lati, Norfifah; Ali, Fadzilah Md.; Nazar, Roslinda Mohd

    2015-05-01

    A theoretical study has been presented to describe the flow and heat transfer in the boundary layers on a nonlinearly stretching sheet with a variable wall temperature and suction, in the presence of magnetic field and non-uniform heat source. The governing partial differential equations are converted into ordinary differential equations by similarity transformation, which is then solved numerically using the shooting method. Results for the skin friction coefficient, local Nusselt number, velocity profiles as well as temperature profiles are presented through graphs and table for several sets of values of the parameters. The effects of the parameters on the flow and heat transfer characteristics are thoroughly examined.

  8. Note: improving spatial resolution of optical frequency-domain reflectometry against frequency tuning nonlinearity using non-uniform fast Fourier transform.

    PubMed

    Ding, Zhenyang; Liu, Tiegen; Meng, Zhuo; Liu, Kun; Chen, Qinnan; Du, Yang; Li, Dingjie; Yao, X Steve

    2012-06-01

    We propose using non-uniform FFT to minimize the degrading effect of frequency tuning nonlinearity of a tunable laser source (TLS) in an optical frequency-domain reflectometry (OFDR) system. We use an auxiliary interferometer to obtain the required instantaneous optical frequency of the TLS and successfully demonstrate 100 times enhancement in spatial resolution of OFDR with only a 20% increase in computation time. The corresponding measurement reflectivity sensitivity is better than -80 dB, sufficient to detect bending induced index changes in an optical fiber. PMID:22755676

  9. Note: Improving spatial resolution of optical frequency-domain reflectometry against frequency tuning nonlinearity using non-uniform fast Fourier transform

    NASA Astrophysics Data System (ADS)

    Ding, Zhenyang; Liu, Tiegen; Meng, Zhuo; Liu, Kun; Chen, Qinnan; Du, Yang; Li, Dingjie; Yao, X. Steve

    2012-06-01

    We propose using non-uniform FFT to minimize the degrading effect of frequency tuning nonlinearity of a tunable laser source (TLS) in an optical frequency-domain reflectometry (OFDR) system. We use an auxiliary interferometer to obtain the required instantaneous optical frequency of the TLS and successfully demonstrate 100 times enhancement in spatial resolution of OFDR with only a 20% increase in computation time. The corresponding measurement reflectivity sensitivity is better than -80 dB, sufficient to detect bending induced index changes in an optical fiber.

  10. Analytical modeling of large amplitude free vibration of non-uniform beams carrying a both transversely and axially eccentric tip mass

    NASA Astrophysics Data System (ADS)

    Malaeke, Hasan; Moeenfard, Hamid

    2016-03-01

    The objective of this paper is to study large amplitude flexural-extensional free vibration of non-uniform cantilever beams carrying a both transversely and axially eccentric tip mass. The effects of variable axial force is also taken into account. Hamilton's principle is utilized to obtain the partial differential equations governing the nonlinear vibration of the system as well as the corresponding boundary conditions. A numerical finite difference scheme is proposed to find the natural frequencies and mode shapes of the system which is validated specifically for a beam with linearly varying cross section. Using a single mode approximation in conjunction with the Lagrange method, the governing equations are reduced to a set of two nonlinear ordinary differential equations in terms of end displacement components of the beam which are coupled due to the presence of the transverse eccentricity. These temporal coupled equations are then solved analytically using the multiple time scales perturbation technique. The obtained analytical results are compared with the numerical ones and excellent agreement is observed. The qualitative and quantitative knowledge resulting from this research is expected to enable the study of the effects of eccentric tip mass and non-uniformity on the large amplitude flexural-extensional vibration of beams for improved dynamic performance.

  11. MHD Natural Convective Flow in an Isosceles Triangular Cavity Filled with Porous Medium due to Uniform/Non-Uniform Heated Side Walls

    NASA Astrophysics Data System (ADS)

    Javed, Tariq; Siddiqui, Muhammad Arshad; Mehmood, Ziafat; Pop, Ioan

    2015-10-01

    In this article, numerical simulations are carried out for fluid flow and heat transfer through natural convection in an isosceles triangular cavity under the effects of uniform magnetic field. The cavity is of cold bottom wall and uniformly/non-uniformly heated side walls and is filled with isotropic porous medium. The governing Navier Stoke's equations are subjected to Penalty finite element method to eliminate pressure term and Galerkin weighted residual method is applied to obtain the solution of the reduced equations for different ranges of the physical parameters. The results are verified as grid independent and comparison is made as a limiting case with the results available in literature, and it is shown that the developed code is highly accurate. Computations are presented in terms of streamlines, isotherms, local Nusselt number and average Nusselt number through graphs and tables. It is observed that, for the case of uniform heating side walls, strength of circulation of streamlines gets increased when Rayleigh number is increased above critical value, but increase in Hartmann number decreases strength of streamlines circulations. For non-uniform heating case, it is noticed that heat transfer rate is maximum at corners of bottom wall.

  12. Peristaltic propulsion of generalized Burgers' fluids through a non-uniform porous medium: a study of chyme dynamics through the diseased intestine.

    PubMed

    Tripathi, D; Anwar Bég, O

    2014-02-01

    A mathematical study of the peristaltic flow of complex rheological viscoelastic fluids using the generalized fractional Burgers' model through a non-uniform channel is presented. This model is designed to study the movement of chyme and undigested chyme (biophysical waste materials) through the small intestine to the large intestine. To simulate blockages and impedance of debris generated by cell shedding, infections, adhesions on the wall and undigested material, a drag force porous media model is utilized. This effectively mimicks resistance to chyme percolation generated by solid matrix particles in the regime. The conduit geometry is mathematically simulated as a sinusoidal propagation with linear increment in shape of the bolus along the length of channel. A modified Darcy-Brinkman model is employed to simulate the generalized flows through isotropic, homogenous porous media, a simplified but physically robust approximation to actual clinical situations. To model the rheological properties of chyme, a viscoelastic Burgers' fluid formulation is adopted. The governing equations are simplified by assuming long wavelength and low Reynolds number approximations. Numerical and approximate analytical solutions are obtained with two semi-numerical techniques, namely the homotopy perturbation method and the variational iteration method. Visualization of the results is achieved with Mathematica software. The influence of the dominant hydromechanical and geometric parameters such as fractional viscoelastic parameters, wave number, non-uniformity constant, permeability parameter, and material constants on the peristaltic flow characteristics are depicted graphically. PMID:24300568

  13. Carbon monoxide intoxication.

    PubMed

    Bleecker, Margit L

    2015-01-01

    Carbon monoxide (CO) is a colorless, odorless, nonirritant gas that accounts for numerous cases of CO poisoning every year from a variety of sources of incomplete combustion of hydrocarbons. These include poorly functioning heating systems, indoor propane-powered forklifts, indoor burning of charcoal burning briquettes, riding in the back of pick-up trucks, ice skating rinks using propane-powered resurfacing machines, and gasoline-powered generators that are not in correct locations. Once CO is inhaled it binds with hemoglobin to form carboxyhemoglobin (COHb) with an affinity 200 times greater than oxygen that leads to decreased oxygen-carrying capacity and decreased release of oxygen to tissues leading to tissue hypoxia. Ischemia occurs with CO poisoning when there is loss of consciousness that is accompanied by hypotension and ischemia in the arterial border zones of the brain. Besides binding to many heme-containing proteins, CO disrupts oxidative metabolism leading to the formation of free radicals. Once hypotension and unconsciousness occur with CO poisoning, lipid peroxidation and apoptosis follow. Because COHb has a short half-life, examination of other biomarkers of CO neurotoxicity that reflect inflammation or neuronal damage has not demonstrated consistent results. The initial symptoms with CO exposure when COHb is 15-30% are nonspecific, namely, headache, dizziness, nausea, fatigue, and impaired manual dexterity. However individuals with ischemic heart disease may experience chest pain and decreased exercise duration at COHb levels between 1% and 9%. COHb levels between 30% and 70% lead to loss of consciousness and eventually death. Following resolution of acute symptoms there may be a lucid interval of 2-40 days before the development of delayed neurologic sequelae (DNS), with diffuse demyelination in the brain accompanied by lethargy, behavior changes, forgetfulness, memory loss, and parkinsonian features. Seventy-five percent of patients with DNS

  14. Two-phase simulation of non-uniform magnetic field effects on biofluid (blood) with magnetic nanoparticles through a collapsible tube

    NASA Astrophysics Data System (ADS)

    Aminfar, H.; Mohammadpourfard, M.; Ghaderi, F.

    2013-04-01

    In this paper, the behavior of a two-dimensional tube with an elastic segment containing ferrofluid (blood and 3 vol% Fe3O4), in presence of non-uniform magnetic field is reported. Two cases of magnetic field including constant gradient (both positive and negative) and field of a wire, carrying electric current were examined. Surface tension of the membrane is considered to be fixed and constant along the elastic wall. Numerical solution of governing equations of the flow field has been obtained using the two-phase mixture model and control volume technique. Also, the membrane equation has been used to iterate and access the membrane position. Based on the obtained results, applying positive gradient magnetic field makes the tube narrower, but the negative one and magnetic field of electric wire opens the tube up.

  15. Radiation Effects on the Flow of Powell-Eyring Fluid Past an Unsteady Inclined Stretching Sheet with Non-Uniform Heat Source/Sink

    PubMed Central

    Hayat, Tasawar; Asad, Sadia; Mustafa, Meraj; Alsaedi, Ahmed

    2014-01-01

    This study investigates the unsteady flow of Powell-Eyring fluid past an inclined stretching sheet. Unsteadiness in the flow is due to the time-dependence of the stretching velocity and wall temperature. Mathematical analysis is performed in the presence of thermal radiation and non-uniform heat source/sink. The relevant boundary layer equations are reduced into self-similar forms by suitable transformations. The analytic solutions are constructed in a series form by homotopy analysis method (HAM). The convergence interval of the auxiliary parameter is obtained. Graphical results displaying the influence of interesting parameters are given. Numerical values of skin friction coefficient and local Nusselt number are computed and analyzed. PMID:25072515

  16. Melting Phenomenon in MHD Stagnation Point Flow of Dusty Fluid over a Stretching Sheet in the Presence of Thermal Radiation and Non-Uniform Heat Source/Sink

    NASA Astrophysics Data System (ADS)

    Prasannakumara, B. C.; Gireesha, B. J.; Manjunatha, P. T.

    2015-09-01

    A comprehensive numerical study is conducted to investigate the effect of melting on flow and heat transfer of incompressible viscous dusty fluid near two-dimensional stagnation-point flow over a stretching surface, in the presence of thermal radiation, non-uniform heat source/sink and applied magnetic field. Using suitable transformations, the governing nonlinear partial differential equations are transformed into a set of coupled nonlinear ordinary differential equations and then they are solved numerically. The influence of the various interesting parameters on the flow and heat transfer is analyzed and discussed in detail through plotted graphs. Comparison of the present results with existing results is shown and a good agreement is observed. We found that the velocity and temperature fields increase with an increase in the melting process of the stretching sheet.

  17. X-ray conversion efficiency and radiation non-uniformity in the hohlraum experiments at Shenguang-III prototype laser facility

    SciTech Connect

    Zhang, Huasen; Song, Peng; Zou, Shiyang Zhao, Yiqing; Zheng, Wudi; Gu, Peijun; Pei, Wenbing; Yang, Dong; Li, Sanwei; Li, Zhichao; Guo, Liang; Wang, Feng; Peng, Xiaoshi; Wei, Huiyue; Xu, Tao; Jiang, Shaoen; Ding, Yongkun

    2014-11-15

    The hohlraum radiation properties are studied experimentally by the Shenguang-III prototype laser facility and numerically by the two-dimensional code LARED with the multi-group radiation transfer model. The measured radiation temperature is consistent with the prediction of the simulations in a wide laser energy range, suggesting that the x-ray conversion efficiency is around 75% at the peak radiation temperature. The delicate hohlraum experiments further show that the radiation intensity inside the hohlraum is significantly non-uniform. The measured radiation flux of the hot spot region is over twice higher than that of the re-emitted wall region. Good agreements between the experiments and simulations further demonstrate the validity of the LARED code to study the hohlraum radiation properties.

  18. Radar Imaging of Non-Uniformly Rotating Targets via a Novel Approach for Multi-Component AM-FM Signal Parameter Estimation

    PubMed Central

    Wang, Yong

    2015-01-01

    A novel radar imaging approach for non-uniformly rotating targets is proposed in this study. It is assumed that the maneuverability of the non-cooperative target is severe, and the received signal in a range cell can be modeled as multi-component amplitude-modulated and frequency-modulated (AM-FM) signals after motion compensation. Then, the modified version of Chirplet decomposition (MCD) based on the integrated high order ambiguity function (IHAF) is presented for the parameter estimation of AM-FM signals, and the corresponding high quality instantaneous ISAR images can be obtained from the estimated parameters. Compared with the MCD algorithm based on the generalized cubic phase function (GCPF) in the authors’ previous paper, the novel algorithm presented in this paper is more accurate and efficient, and the results with simulated and real data demonstrate the superiority of the proposed method. PMID:25806870

  19. [Carbon monoxide intoxications in Portugal].

    PubMed

    Sá, Márcia Christel; Rodrigues, Rui Paulo; Moura, Daniel

    2011-01-01

    The prevalence of carbon monoxide intoxication in the World shows that this is a common situation. In Portugal, there are no concrete data available in literature and its incidence remains unknown. Currently, the use of hyperbaric oxygen is a valid therapeutic for carbon monoxide poisoning management. However, its effectiveness and its proper handling are still controversial. The first aim of this study was to estimate the incidence of carbon monoxide intoxication in Portugal and to analyze its demographic characteristics. The second objective of this work was to evaluate the possible change in the type of treatment applied in areas near de hyperbaric chamber of Unidade Local de Saúde de Matosinhos, since its opening in June 2006. To achieve these objectives, we conducted a survey on admissions data for carbon monoxide intoxication occured between January first, 2000 and December 31, 2007. These data was collected in seven hospitals and in the Administração Central do Sistema de Saúde, I.P. Nationally, 621 hospitalizations were recorded, which represents an incidence of 5,86/100000 in 8 years. In the seven hospitals, there were 93 hospitalizations due to carbon monoxide intoxication during the same period of time. There was a peak of incidence during winter, between November and March and there was a similar distribution in men (47,3%) and women (52,7%). Since June 2006, date of opening of the hyperbaric chamber, the Unidade Local de Saúde de Matosinhos, E.P.E. recorded a sharp increase in the number of hospitalization for carbon monoxide intoxication. The number of admissions in the 19 months after the chamber opening was double the number of all cases occurred in that institution in the 65 months prior. We concluded that, in Portugal, carbon monoxide intoxication is an uncommon situation but it´s still an important cause of hospitalization. The referral of cases to the Unidade Local de Saúde de Matosinhos, E.P.E. since the opening of hyperbaric chamber

  20. Carbon monoxide poisoning from Sterno.

    PubMed Central

    Murray, T. J.

    1978-01-01

    A high school student became ill and later unconscious while working over a heating table set over three cans of burning Sterno. Measurements of 1000 to 3000 parts per million of carbon monoxide were obtained around and above the apparatus. Although the room was well ventilated there was incomplete combustion of the canned heating fuel because the apparatus was surrounded by aluminum foil, which resulted in poor oxygenation of the flame area. This case demonstrates the hazards of carbon monoxide poisoning from incompletely burned Sterno. PMID:638911

  1. (Carbon monoxide metabolism by photosynthetic bacteria)

    SciTech Connect

    Not Available

    1989-01-01

    Research continued on the metabolism of carbon monoxide by Rhodospirillum rubrum. This report discusses progress on the activity, induction, inhibition, and spectroscopic analysis of the enzyme Carbon Monoxide Dehydrogenase. (CBS)

  2. MOPITT Carbon Monoxide Over India

    NASA Technical Reports Server (NTRS)

    2002-01-01

    MOPITT observed high levels of carbon monoxide (red and yellow pixels) over the Indian sub-continent during March. These values are associated with industrial activity in the region just south of the Himalayan Mountains. Notice that to the north, the Himalayas are characterized by low values (blue pixels).

  3. Open air carbon monoxide poisoning.

    PubMed

    Jumbelic, M I

    1998-01-01

    An unusual manner of carbon monoxide poisoning claimed the lives of two adults in two separate incidents. In the first case, a young man was four wheeling in a swampy area when his jeep became stuck in the mud as he continued to floor the accelerator. Carbon monoxide fumes entered the vehicle through the rusted floorboards, killing the driver. In the second case, two teens were skinny dipping behind a motor boat when they became affected by the boat exhaust. One of the youths was overcome and submerged into the lake. Both incidents were initially attributed to incorrect causes--a car accident and a drowning--because of the false notion that carbon monoxide is not a hazard in a ventilated area. The carboxyhemoglobin levels in these victims were 78 and 62% respectively. It was only through laboratory testing that carbon monoxide poisoning was identified as the cause of their demise. Physicians as well as the public need to be aware of the potential for this life threatening hazard to occur so that there can be proper emergency treatment and the prevention of fatalities. PMID:9456553

  4. Carbon monoxide and lethal arrhythmias

    SciTech Connect

    Farber, J.P.; Schwartz, P.J.; Vanoli, E.; Stramba-Badiale, M.; De Ferrari, G.M. )

    1990-12-01

    The effect of acute exposure to carbon monoxide on ventricular arrhythmias was studied in a previously described chronically maintained animal model of sudden cardiac death. In 60 percent of dogs with a healed anterior myocardial infarction, the combination of mild exercise and acute myocardial ischemia induces ventricular fibrillation. The events in this model are highly reproducible, thus allowing study by internal control analysis. Dogs that develop ventricular fibrillation during the test of exercise and acute myocardial ischemia are considered at high risk for sudden death and are defined as 'susceptible'; dogs that survive the test without a fatal arrhythmia are considered at low risk for sudden death and are defined as 'resistant.' In the current study, the effects of carboxyhemoglobin levels ranging from 5 to 15 percent were tested in resistant and susceptible dogs. A trend toward higher heart rates was observed at all levels of carboxyhemoglobin, although significant differences were observed only with 15 percent carboxyhemoglobin. This trend was observed at rest and during exercise in both resistant and susceptible dogs. In resistant animals, in which acute myocardial ischemia is typically associated with bradycardia even under the control condition, this reflex response occurred earlier and was augmented after exposure to carbon monoxide. This effect may depend on the increased hypoxic challenge caused by carbon monoxide, and thus on an augmentation of the neural reflex activation or a sensitization of the sinus node to acetylcholine induced by hypoxia. In both resistant and susceptible dogs, carbon monoxide exposure induced a worsening of ventricular arrhythmias in a minority of cases. This worsening was not reproducible in subsequent trials. These data indicate that acute exposure to carbon monoxide is seldom arrhythmogenic in dogs that have survived myocardial infarction. (Abstract Truncated)

  5. Carbon Monoxide from Biomass Burning

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This pair of images shows levels of carbon monoxide at the atmospheric pressure level of 700 millibars (roughly 12,000 feet in altitude) over the continent of South America, as observed by the Measurements Of Pollution In The Troposphere (MOPITT) sensor flying aboard NASA's Terra spacecraft. Data for producing the image on the left were acquired on March 3, 2000, and for the image on the right on September 7, 2000. Blue pixels show low values, yellows show intermediate values, and the red to pink and then white pixels are progressively higher values. In the lefthand image (March 3), notice the fairly low levels of carbon monoxide over the entire continent. The slightly higher equatorial values are the result of burning emissions in sub-Saharan Africa that are convected at the Intertropical Convergence Zone (ITCZ) and spread by the trade winds. Also, notice the effect of the elevated surface topography across the Andes Mountains running north to south along the western coastline. (In this region, white pixels show no data.) In the righthand image (September 7), a large carbon monoxide plume is seen over Brazil, produced primarily by biomass burning across Amazonia and lofted into the atmosphere by strong cloud convection. The generally higher carbon monoxide levels as compared to March are both the result of South American fire emissions and the transport of carbon monoxide across the Atlantic Ocean from widespread biomass burning over Southern Africa. These images were produced using MOPITT data, which are currently being validated. These data were assimilated into an atmospheric chemical transport model using wind vectors provided by the National Center for Environmental Prediction (NCEP). Although there is good confidence in the relative seasonal values and geographic variation measured by MOPITT, that team anticipates their level of confidence will improve further with ongoing intensive validation campaigns and comparisons with in situ and ground

  6. 2.5D modelling of a horizontal electric dipole using Finite Difference method with non-uniform grids and preconditioned sparse matrices

    NASA Astrophysics Data System (ADS)

    Miranda, D. D.; Howard, A. Q.

    2012-12-01

    Computational modelling of geophysical data is an important step in the process of hydrocarbon exploration. It consists in simulating the exploratory procedure and realistic geological environments. It allows a preliminary evaluation of the exploration feasibility of a particular terrain or geological model, indicating the best conditions for geophysical surveys. In this paper, we assess the Finite Difference frequency domain method for modelling the electromagnetic response of a horizontal electric dipole in 1D and 2.5D geometries. The non-uniform grid is refined in regions where the electromagnetic fields vary rapidly, namely the regions where we have variation in conductivity distribution and near the source dipole. We chose the horizontal electromagnetic dipole because it is the source normally used in the marine controlled-source electromagnetic surveys (mCSEM), which is the next step in our research. The mCSEM, also known as Sea Bed Logging, is a method for detection and characterization of thin resistive structures, like hydrocarbon reservoirs, often located in regions of deep water. It consists of a mobile electric dipole or a magnetic loop as a source, positioned near the sea floor where an array of electric and magnetic receivers are deployed. The source transmitter uses a low frequency signal on the order of 1Hz, that diffuses both in the ocean and in the sediments beneath it and is captured by the receivers . Amplitude and phase of this signal depend on the electrical conductivity of the seabed environment. The complexity of the environments and the large dimensions of the geological domains that we want to investigate make the modelling procedure extremely demanding, since the Finite Difference method requires a total discretization of the studied domain, resulting in large systems of linear equations, which can make the procedure long and expensive. Non-uniform grids and exploitation of the sparse property of the Finite Difference matrices are example

  7. Self-Consistent Simulations of Inductively Coupled Discharges at Very Low Pressures Using a FFT Method for Calculating the Non-local Electron Conductivity for the General Case of a Non-Uniform Plasma

    NASA Astrophysics Data System (ADS)

    Polomarov, Oleg; Theodosiou, Constantine; Kaganovich, Igor

    2003-10-01

    A self-consistent system of equations for the kinetic description of non-local, non-uniform, nearly collisionless plasmas of low-pressure discharges is presented. The system consists of a non-local conductivity operator, and a kinetic equation for the electron distribution function (EEDF) averaged over fast electron bounce motions. A Fast Fourier Transform (FFT) method was applied to speed up the numerical simulations. The importance of accounting for the non-uniform plasma density profile in computing the current density profile and the EEDF is demonstrated. Effects of plasma non-uniformity on electron heating in rf electric field have also been studied. An enhancement of the electron heating due to the bounce resonance between the electron bounce motion and the rf electric field has been observed. Additional information on the subject is posted in http://www.pppl.gov/pub_report/2003/PPPL-3814-abs.html and in http://arxiv.org/abs/physics/0211009

  8. Computational modeling of geometry effects on the IDL surface concentration in the presence of non-uniform magnetic field - links to atherosclerosis

    NASA Astrophysics Data System (ADS)

    Aminfar, H.; Mohammadpourfard, M.; Khajeh, K.

    2016-01-01

    Effect of geometry on the atherosclerosis is a significant issue, so the 3D s-shape and 2D axisymmetric stenosis tube as a blood vessel have been analyzed in this work. This paper has focused on the most important parameters in the LSC uptake, inlet Re number and infiltration velocity in the presence of non-uniform magnetic field. The magnetic field is arising from the thin wire with electric current placed vertically to the arterial blood vessel. According to the results of this study, applying magnetic field can be a treatment for atherosclerosis by reducing LSC along the vessel wall. It is observed that, application of magnetic field leads to production of a vortex in the flow, high strain rate, increment of WSS, and also reduction in LSC. For solving the mass transport equation, Lumen-wall model has been used. Blood flow has been considered laminar and incompressible containing Ferro fluid (blood and 4 vol% Fe3O4) under steady state conditions. Numerical solution of governing equations was obtained by using the single-phase model and control volume technique for flow field.

  9. Performance enhancement using a non-uniform vertical electric field and polymer networks for in-plane switching of multi-pretilt, vertically aligned liquid crystal devices.

    PubMed

    Lin, G J; Chen, T J; Tsai, Y W; Lin, Y T; Wu, J J; Yang, Y J

    2014-11-01

    A simple and reproducible alignment method for fabricating vertically aligned (VA) liquid crystal (LC) cells with a multi-pretilt structure is developed. A non-uniform vertical electric field is employed in the LC/monomer mixed cells during the photocuring process, and two pretilt domains with a functional small pretilt angle (∼1.6°) in the stabilized VA LC/polymer cells are achieved. The enhanced electro-optical performance of the cell driven by an in-plane switching field is demonstrated. Compared to the pure cell, the 2 wt.% pretilt angle cell shows 36%, 64%, and 76% improvement in the optical switch, the gray-level rise time, and the gray-level fall time responses, respectively, which are obtained at a low driving voltage (≤12  V). When applied to LC devices, the proposed method not only effectively benefits the LC molecular alignment, but it also significantly boosts the electro-optical performance. PMID:25361320

  10. Design and experiment of 4H-SiC JBS diodes achieving a near-theoretical breakdown voltage with non-uniform floating limiting rings terminal

    NASA Astrophysics Data System (ADS)

    Yuan, Hao; Song, Qingwen; Tang, Xiaoyan; Zhang, Yimeng; Zhang, Yimen; Zhang, Yuming

    2016-09-01

    In this paper, a 4H-SiC Junction Barrier Schottky diode (JBS) with non-uniform floating limiting rings (FLRs) has been investigated and fabricated using n type 4H-SiC epitaxial layer with thickness of 31 μm and doping concentration of 3.3 × 1015 cm-3. According to the simulated results, the key parameters of a FLRs design to achieve a high voltage are the minimum space between two adjacent doped rings, spacing growth step and number of rings. The experimental results also show a great agreement with simulated results. Meanwhile, a near-ideal breakdown voltage of 3.7 kV was achieved, which yield around 95% of the parallel-plane breakdown voltage. The forward characteristics show that the fabricated JBS diodes have a forward current density of 210 A/cm2 at 3 V and a specific on-resistance (Rsp-on) of 7.58 mΩ cm2. Different FLRs parameters have no effect on the forward device performance.

  11. Study on Reduction of Time Lag for Laser-Induced Electrical Discharge in Atmospheric Air with Non-Uniform Electric Field

    NASA Astrophysics Data System (ADS)

    Okano, Daisuke

    1998-11-01

    Study on Reduction of Time Lag for Laser-Induced Electrical Discharge in Atmospheric Air with Non-Uniform Electric Field* , Daisuke Okano, Kyushu Tokai University, 9-1-1 Toroku, Kumamoto, Japan. -----As an electrical discharge can be inductively occurred [1] by a pulsed laser-produced plasma (PLPP) in a rod-to-plate air gap stressed by a DC high voltage(Va), the starting point of laser-induced electrical discharge (LIED) is almost delayed more than few microseconds from focusing the laser beam. It is expected that the LIED by a PLPP is effectively occurred by reducing the time lag. The aim of our research focuses on the reduction for the time lag of LIED using CO2- and YAG pulsed lasers. The typical results are summarized as follows.The time lag of LIED in an atmospheric air gap (30mm) stressed at Va=30 kV is strongly reduced to 33 using CO2- and YAG pulsed lasers. The mechanism for the time lag of LIED is due to the electron attachment and detachment. [1] M.Inoue, T.Takashima, D.Okano et.al., Bull. of Inst. of Industrial Sci. & technical res.in Kyushu Tokai University, No.11 (1995)165 in Japanese. . *This work was supported by Grant-in-Aid for Scientific Research (C)-no.10650295 of The Ministry of education, Science Sports and Culture in japan.

  12. Single particle characterization of biomass burning organic aerosol (BBOA): evidence for non-uniform mixing of high molecular weight organics and potassium

    NASA Astrophysics Data System (ADS)

    Lee, A. K. Y.; Willis, M. D.; Healy, R. M.; Wang, J. M.; Jeong, C.-H.; Wenger, J. C.; Evans, G. J.; Abbatt, J. P. D.

    2015-11-01

    Biomass burning is a major source of black carbon (BC) and primary organic aerosol globally. In particular, biomass burning organic aerosol (BBOA) is strongly associated with atmospheric brown carbon (BrC) that absorbs near ultraviolet and visible light, resulting in significant impacts on regional visibility degradation and radiative forcing. The mixing state of BBOA can play a critical role in the prediction of aerosol optical properties. In this work, single particle measurements from a soot-particle aerosol mass spectrometer coupled with a light scattering module (LS-SP-AMS) were performed to examine the mixing state of BBOA, refractory black carbon (rBC) and potassium (K+, a tracer for biomass burning aerosol) in an air mass influenced by aged biomass burning. Cluster analysis of single particle measurements identified five BBOA-related particle types. rBC accounted for 3-14 w.t. % of these particle types on average. Only one particle type exhibited a strong ion signal for K+, with mass spectra characterized by low molecular weight organic species. The remaining four particle types were classified based on the apparent molecular weight of the BBOA constituents. Two particle types were associated with low potassium content and significant amounts of high molecular weight (HMW) organic compounds. Our observations indicate non-uniform mixing of particles within a biomass burning plume in terms of molecular weight and illustrate that HMW BBOA can be a key contributor to low-volatility BrC observed in BBOA particles.

  13. Radiation heat transfer model using Monte Carlo ray tracing method on hierarchical ortho-Cartesian meshes and non-uniform rational basis spline surfaces for description of boundaries

    NASA Astrophysics Data System (ADS)

    Kuczyński, Paweł; Białecki, Ryszard

    2014-06-01

    The paper deals with a solution of radiation heat transfer problems in enclosures filled with nonparticipating medium using ray tracing on hierarchical ortho-Cartesian meshes. The idea behind the approach is that radiative heat transfer problems can be solved on much coarser grids than their counterparts from computational fluid dynamics (CFD). The resulting code is designed as an add-on to OpenFOAM, an open-source CFD program. Ortho-Cartesian mesh involving boundary elements is created based upon CFD mesh. Parametric non-uniform rational basis spline (NURBS) surfaces are used to define boundaries of the enclosure, allowing for dealing with domains of complex shapes. Algorithm for determining random, uniformly distributed locations of rays leaving NURBS surfaces is described. The paper presents results of test cases assuming gray diffusive walls. In the current version of the model the radiation is not absorbed within gases. However, the ultimate aim of the work is to upgrade the functionality of the model, to problems in absorbing, emitting and scattering medium projecting iteratively the results of radiative analysis on CFD mesh and CFD solution on radiative mesh.

  14. 4D non-uniformly sampled HCBCACON and ¹J(NCα)-selective HCBCANCO experiments for the sequential assignment and chemical shift analysis of intrinsically disordered proteins.

    PubMed

    Nováček, Jiří; Haba, Noam Y; Chill, Jordan H; Zídek, Lukáš; Sklenář, Vladimír

    2012-06-01

    A pair of 4D NMR experiments for the backbone assignment of disordered proteins is presented. The experiments exploit (13)C direct detection and non-uniform sampling of the indirectly detected dimensions, and provide correlations of the aliphatic proton (H(α), and H(β)) and carbon (C(α), C(β)) resonance frequencies to the protein backbone. Thus, all the chemical shifts regularly used to map the transient secondary structure motifs in the intrinsically disordered proteins (H(α), C(α), C(β), C', and N) can be extracted from each spectrum. Compared to the commonly used assignment strategy based on matching the C(α) and C(β) chemical shifts, inclusion of the H(α) and H(β) provides up to three extra resonance frequencies that decrease the chance of ambiguous assignment. The experiments were successfully applied to the original assignment of a 12.8 kDa intrinsically disordered protein having a high content of proline residues (26 %) in the sequence. PMID:22580891

  15. Simulation of magnetic drug targeting through tracheobronchial airways in the presence of an external non-uniform magnetic field using Lagrangian magnetic particle tracking

    NASA Astrophysics Data System (ADS)

    Pourmehran, O.; Rahimi-Gorji, M.; Gorji-Bandpy, M.; Gorji, T. B.

    2015-11-01

    Drug delivery technologies are an important area within biomedicine. Targeted drug delivery aims to reduce the undesired side effects of drug usage by directing or capturing the active agents near a desired site within the body. Herein, a numerical investigation of magnetic drug targeting (MDT) using aerosol drugs named polystyrene particle (PMS40) in human lung is presented considering one-way coupling on the transport and capture of the magnetic particle. A realistic 3D geometry based on CT scan images is provided for CFD simulation. An external non-uniform magnetic field is applied. Parametric investigation is conducted and the influence of particle diameter, magnetic source position, and magnetic number (Mn) on the deposition efficiency and particle behavior is reported. According to the results, the magnetic field increased deposition efficiency of particles in a target region, the efficiency of deposition and MDT technique has a direct relation with increasing the particle diameter for magnetic number of 1 Tesla (T) and lower (Mn≤1(T)). Also it can be seen that there is an inverse relation between the particle diameter and deposition efficiency when Mn is more than 1 (T).

  16. Electric Field Optimization in 170 kV Gas-Insulated Switchgear Spacer based on Non-Uniform Rational B-spline Curve

    NASA Astrophysics Data System (ADS)

    Han, In Su; Kim, Eung Sik; Min, Suk Won; Hur, Don; Park, Jong Keun

    2004-10-01

    In this paper, the electric field at the spacer in a 170 kV gas-insulated switchgear (GIS) is optimized. Initially, the tangential and total electric fields around the original shape of the 170 kV GIS produced by a Korean company are calculated using a combination of the charge simulation method (CSM) and surface charge method (SCM). The contour of the spacer in the 170 kV GIS is found using a non-uniform rational B-spline (NURB) curve the effectiveness of which has been proved. By moving some control points in the NURB curve, the initial shape of the 170 kV GIS can be determined so that we may begin to optimize the electric field. Owing to the proposed algorithm, the overall process has a stable convergence. The objects that we want to design are the upper and lower parts of the spacer. Finally, we can find the shapes in which the tangential and total electric fields are optimized.

  17. Accelerating electrostatic interaction calculations with graphical processing units based on new developments of Ewald method using non-uniform fast Fourier transform.

    PubMed

    Yang, Sheng-Chun; Wang, Yong-Lei; Jiao, Gui-Sheng; Qian, Hu-Jun; Lu, Zhong-Yuan

    2016-01-30

    We present new algorithms to improve the performance of ENUF method (F. Hedman, A. Laaksonen, Chem. Phys. Lett. 425, 2006, 142) which is essentially Ewald summation using Non-Uniform FFT (NFFT) technique. A NearDistance algorithm is developed to extensively reduce the neighbor list size in real-space computation. In reciprocal-space computation, a new algorithm is developed for NFFT for the evaluations of electrostatic interaction energies and forces. Both real-space and reciprocal-space computations are further accelerated by using graphical processing units (GPU) with CUDA technology. Especially, the use of CUNFFT (NFFT based on CUDA) very much reduces the reciprocal-space computation. In order to reach the best performance of this method, we propose a procedure for the selection of optimal parameters with controlled accuracies. With the choice of suitable parameters, we show that our method is a good alternative to the standard Ewald method with the same computational precision but a dramatically higher computational efficiency. PMID:26584145

  18. Carbon monoxide kinetics following simulated cigarette smoking

    SciTech Connect

    Karnik, A.S.; Coin, E.J.

    1980-05-01

    Carbon monoxide kinetics were measured in the blood (% carboxyhemoglobin) and alveolar phase (ppM carbon monoxide) after simulated cigarette smoking. Cigarette smoking was siumlated using the same amount of carbon monoxide that 2R1F cigarettes manufactured by the Tobacco Research Institute would contain. Ten boluses of air containing carbon monoxide equivalent to smoking one cigarette were inhaled by six healthy nonsmoker volunteers. Carbon monoxide in the air phase was measured by an Ecolyzer and carboxyhemoglobin was measured by a CO-Oximeter. The mean rise in alveolar carbon monoxide immediately and 20 min after inhaling the last bolus was 3.3 and 3.1 ppM, respectively (p<.005). The mean rise in carboxyhemoglobin immediately and 20 min after inhalation of the last bolus was 0.8 and 0.5% respectively (P<.005). The changes in carboxyhemoglobin were found to be similar to changes that occur when one cigarette is actually smoked.

  19. 40 CFR 52.1581 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Control strategy: Carbon monoxide. 52... strategy: Carbon monoxide. (a) Approval—The September 28, 1995 revision to the carbon monoxide state... Quality Standard for carbon monoxide through the year 2007. (b) The base year carbon monoxide...

  20. 40 CFR 52.1581 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 4 2013-07-01 2013-07-01 false Control strategy: Carbon monoxide. 52... strategy: Carbon monoxide. (a) Approval—The September 28, 1995 revision to the carbon monoxide state... Quality Standard for carbon monoxide through the year 2007. (b) The base year carbon monoxide...

  1. 21 CFR 862.3220 - Carbon monoxide test system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Carbon monoxide test system. 862.3220 Section 862....3220 Carbon monoxide test system. (a) Identification. A carbon monoxide test system is a device intended to measure carbon monoxide or carboxyhemoglobin (carbon monoxide bound to the hemoglobin in...

  2. 21 CFR 862.3220 - Carbon monoxide test system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Carbon monoxide test system. 862.3220 Section 862....3220 Carbon monoxide test system. (a) Identification. A carbon monoxide test system is a device intended to measure carbon monoxide or carboxyhemoglobin (carbon monoxide bound to the hemoglobin in...

  3. 40 CFR 52.1581 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 4 2011-07-01 2011-07-01 false Control strategy: Carbon monoxide. 52... strategy: Carbon monoxide. (a) Approval—The September 28, 1995 revision to the carbon monoxide state... Quality Standard for carbon monoxide through the year 2007. (b) The base year carbon monoxide...

  4. 21 CFR 862.3220 - Carbon monoxide test system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Carbon monoxide test system. 862.3220 Section 862....3220 Carbon monoxide test system. (a) Identification. A carbon monoxide test system is a device intended to measure carbon monoxide or carboxyhemoglobin (carbon monoxide bound to the hemoglobin in...

  5. 21 CFR 862.3220 - Carbon monoxide test system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Carbon monoxide test system. 862.3220 Section 862....3220 Carbon monoxide test system. (a) Identification. A carbon monoxide test system is a device intended to measure carbon monoxide or carboxyhemoglobin (carbon monoxide bound to the hemoglobin in...

  6. 40 CFR 52.1581 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 4 2014-07-01 2014-07-01 false Control strategy: Carbon monoxide. 52... strategy: Carbon monoxide. (a) Approval—The September 28, 1995 revision to the carbon monoxide state... Quality Standard for carbon monoxide through the year 2007. (b) The base year carbon monoxide...

  7. 21 CFR 862.3220 - Carbon monoxide test system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Carbon monoxide test system. 862.3220 Section 862....3220 Carbon monoxide test system. (a) Identification. A carbon monoxide test system is a device intended to measure carbon monoxide or carboxyhemoglobin (carbon monoxide bound to the hemoglobin in...

  8. 40 CFR 52.1581 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 4 2012-07-01 2012-07-01 false Control strategy: Carbon monoxide. 52... strategy: Carbon monoxide. (a) Approval—The September 28, 1995 revision to the carbon monoxide state... Quality Standard for carbon monoxide through the year 2007. (b) The base year carbon monoxide...

  9. APPLICATION OF A LUMPED-PROCESS MATHEMATICAL MODEL TO DISSOLUTION OF NON-UNIFORMLY DISTRIBUTED IMMISCIBLE LIQUID IN HETEROGENEOUS POROUS MEDIA

    PubMed Central

    Marble, J. C.; DiFilippo, E. L.; Zhang, Z.; Tick, G. R.; Brusseau, M. L.

    2010-01-01

    The use of a lumped-process mathematical model to simulate the complete dissolution of immiscible liquid non-uniformly distributed in physically heterogeneous porous-media systems was investigated. The study focused specifically on systems wherein immiscible liquid was poorly accessible to flowing water. Two representative, idealized scenarios were examined, one wherein immiscible liquid at residual saturation exists within a lower-permeability unit residing in a higher-permeability matrix, and one wherein immiscible liquid at higher saturation (a pool) exists within a higher-permeability unit adjacent to a lower-permeability unit. As expected, effluent concentrations were significantly less than aqueous solubility due to dilution and by-pass flow effects. The measured data were simulated with two mathematical models, one based on a simple description of the system and one based on a more complex description. The permeability field and the distribution of the immiscible-liquid zones were represented explicitly in the more complex, distributed-process model. The dissolution rate coefficient in this case represents only the impact of local-scale (and smaller) processes on dissolution, and the parameter values were accordingly obtained from the results of experiments conducted with one-dimensional, homogeneously-packed columns. In contrast, the system was conceptualized as a pseudo-homogeneous medium with immiscible liquid uniformly distributed throughout the system for the simpler, lumped-process model. With this approach, all factors that influence immiscible-liquid dissolution are incorporated into the calibrated dissolution rate coefficient, which in such cases serves as a composite or lumped term. The calibrated dissolution rate coefficients obtained from the simulations conducted with the lumped-process model were approximately two to three orders of magnitude smaller than the independently-determined values used for the simulations conducted with the

  10. Modelling river bank erosion using a 2D depth-averaged numerical model of flow and non-cohesive, non-uniform sediment transport

    NASA Astrophysics Data System (ADS)

    El Kadi Abderrezzak, Kamal; Die Moran, Andrés; Tassi, Pablo; Ata, Riadh; Hervouet, Jean-Michel

    2016-07-01

    Bank erosion can be an important form of morphological adjustment in rivers. With the advances made in computational techniques, two-dimensional (2D) depth-averaged numerical models have become valuable tools for resolving many engineering problems dealing with sediment transport. The objective of this research work is to present a simple, new, bank-erosion operator that is integrated into a 2D Saint-Venant-Exner morphodynamic model. The numerical code is based on an unstructured grid of triangular elements and finite-element algorithms. The slope of each element in the grid is compared to the angle of repose of the bank material. Elements for which the slope is too steep are tilted to bring them to the angle of repose along a horizontal axis defined such that the volume loss above the axis is equal to the volume gain below, thus ensuring mass balance. The model performance is assessed using data from laboratory flume experiments and a scale model of the Old Rhine. For the flume experiment case with uniform bank material, relevant results are obtained for bank geometry changes. For the more challenging case (i.e. scale model of the Old Rhine with non-uniform bank material), the numerical model is capable of reproducing the main features of the bank failure, induced by the newly designed groynes, as well as the transport of the mobilized sediment material downstream. Some deviations between the computed results and measured data are, however, observed. They are ascribed to the effects of three-dimensional (3D) flow structures, pore pressure and cohesion, which are not considered in the present 2D model.

  11. Evaluation of hyperelastic models for the non-linear and non-uniform high strain-rate mechanics of tibial cartilage.

    PubMed

    Deneweth, Jessica M; McLean, Scott G; Arruda, Ellen M

    2013-06-21

    Accurate modeling of the high strain-rate response of healthy human knee cartilage is critical to investigating the mechanism(s) of knee osteoarthritis and other cartilage disorders. Osteoarthritis has been suggested to originate from regional shifts in joint loading during walking and other high strain-rate physical activities. Tibial plateau cartilage under compression rates analogous to walking exhibits a non-linear and location-dependent mechanical response. A constitutive model of cartilage that efficiently predicts the non-linear and non-uniform high strain-rate mechanics of tibial plateau cartilage is important for computational studies of osteoarthritis development. A transversely isotropic hyperelastic statistical chain model has been developed. The model's ability to simulate the 1-strain/s unconfined compression response of healthy human tibial plateau articular cartilage has been assessed, along with two other hyperelastic statistical chain models. The transversely isotropic model exhibited a superior fit to the non-linear stress-strain response of the cartilage. Furthermore, the model maintained its predictive capability after being reduced from four degrees of freedom to one. The remaining material constant of the model, which represented the local collagen density of the tissue, demonstrated a regional dependence in close agreement with physiological variations in collagen density and cartilage modulus in human knees. The transversely isotropic eight-chain network of freely jointed chains with a regionally-dependent material constant represents a novel and efficient approach for modeling the complex response of human tibial cartilage under high strain-rate compression. The anisotropy and microstructural variations of the cartilage matrix dictate the model's response, rendering it directly applicable to computational modeling of the human knee. PMID:23669276

  12. Statistical searches for microlensing events in large, non-uniformly sampled time-domain surveys: A test using palomar transient factory data

    SciTech Connect

    Price-Whelan, Adrian M.; Agüeros, Marcel A.; Fournier, Amanda P.; Street, Rachel; Ofek, Eran O.; Covey, Kevin R.; Levitan, David; Sesar, Branimir; Laher, Russ R.; Surace, Jason

    2014-01-20

    Many photometric time-domain surveys are driven by specific goals, such as searches for supernovae or transiting exoplanets, which set the cadence with which fields are re-imaged. In the case of the Palomar Transient Factory (PTF), several sub-surveys are conducted in parallel, leading to non-uniform sampling over its ∼20,000 deg{sup 2} footprint. While the median 7.26 deg{sup 2} PTF field has been imaged ∼40 times in the R band, ∼2300 deg{sup 2} have been observed >100 times. We use PTF data to study the trade off between searching for microlensing events in a survey whose footprint is much larger than that of typical microlensing searches, but with far-from-optimal time sampling. To examine the probability that microlensing events can be recovered in these data, we test statistics used on uniformly sampled data to identify variables and transients. We find that the von Neumann ratio performs best for identifying simulated microlensing events in our data. We develop a selection method using this statistic and apply it to data from fields with >10 R-band observations, 1.1 × 10{sup 9} light curves, uncovering three candidate microlensing events. We lack simultaneous, multi-color photometry to confirm these as microlensing events. However, their number is consistent with predictions for the event rate in the PTF footprint over the survey's three years of operations, as estimated from near-field microlensing models. This work can help constrain all-sky event rate predictions and tests microlensing signal recovery in large data sets, which will be useful to future time-domain surveys, such as that planned with the Large Synoptic Survey Telescope.

  13. Minimum quench power dissipation and current non-uniformity in international thermonuclear experimental reactor type NbTi cable-in-conduit conductor samples under direct current conditions

    NASA Astrophysics Data System (ADS)

    Rolando, G.; van Lanen, E. P. A.; Nijhuis, A.

    2012-05-01

    The level of current non-uniformity in NbTi cable-in-conduit conductors (CICCs) sections near the joints in combination with the magnetic field profile needs attention in view of proper joint design. The strand joule power and current distribution at quench under DC conditions of two samples of ITER poloidal field coil conductors, as tested in the SULTAN facility, and of the so called PFCI model coil insert, have been analyzed with the numerical cable model JackPot. The precise trajectories of all individual strands, joint design, cabling configuration, spatial distribution of the magnetic field, sample geometry, and experimentally determined interstrand resistance distributions have been taken into account. Although unable to predict the quench point due to the lack of a thermal-hydraulic routine, the model allows to assess the instantaneous strand power at quench and its local distribution in the cable once the quench conditions in terms of current and temperature are experimentally known. The analysis points out the relation of the above mentioned factors with the DC quench stability of both short samples and coils. The possible small scale and local electrical-thermal interactions were ignored in order to examine the relevance of such effects in the overall prediction of the CICC performance. The electromagnetic code shows an excellent quantitative predictive potential for CICC transport properties, excluding any freedom for matching the results. The influence of the local thermal effects in the modeling is identified as being marginal and far less than the generally accepted temperature margin for safe operation.

  14. Reduction of the effect of non-uniform backscatter from an E-type support arm of a Varian a-Si EPID used for dosimetry

    NASA Astrophysics Data System (ADS)

    Rowshanfarzad, Pejman; Sabet, Mahsheed; O'Connor, Daryl J.; Greer, Peter B.

    2010-11-01

    Backscatter from the metallic components in the support arm is one of the sources of inaccuracy in dosimetry with Varian amorphous silicon electronic portal imaging devices (a-Si EPIDs). In this study, the non-uniform arm backscatter is blocked by adding lead sheets between the EPID and an E-type support arm. By comparing the EPID responses on and off the arm, with and without lead and considering the extra weight on the imager, 2 mm of lead was determined as the optimum thickness for both 6 and 18 MV beam energies. The arm backscatter at the central axis with the 2 mm lead in place decreased to 0.1% and 0.2% for the largest field size of 30 × 30 cm2 using 6 and 18 MV beams, from 2.3% and 1.3% without lead. Changes in the source-to-detector distance (SDD) did not affect the backscatter component more than 1%. The symmetry of the in-plane profiles improved for all field sizes for both beam energies. The addition of lead decreased the contrast-to-noise ratio and resolution by 1.3% and 0.84% for images taken in 6 MV and by 0.5% and 0.38% for those in 18 MV beams. The displacement of the EPID central pixel was measured during a 360° gantry rotation with and without lead which was 1 pixel different. While the backscatter reduces with increasing lead thickness, a 2 mm lead sheet seems sufficient for acceptable dosimetry results without any major degradation to the routine performance of the imager. No increase in patient skin dose was detected.

  15. Effect of topograohy and a water repelleny layer on the non-uniform developmemt of planted trees in a sandy arid area

    NASA Astrophysics Data System (ADS)

    Yair, Aaron; Arbel, Youval

    2015-04-01

    A Tamarix aphylla forest was planted on arid sand dunes in the northern Negev, where average annual rainfall is 150 mm. Field observations, 40 years after planting, revealed a non-uniform spatial survival and development of planted trees. Trees planted over the crest of the dunes are well developed with large canopies and a high survival rate, whereas trees planted in the interdune flat corridors are small, thin and scattered. A thick litter layer, underlain by a sandy repellent layer, developed below the large trees. The water repellent layer is absent in the area of the small trees. The study focused on the role of the water repellent layer on the water regime over the steep and the low angle dunes. Water repellency was determined by the Water Penetration Time Method. The monitoring of rainfall-runoff relationships was based on runoff plots established in both areas. Samples for soil water content were taken following rain events. Data obtained show a striking difference between the steep and long dunes in all aspects studied. Results obtained show that two opposite feedback mechanisms occurred after tree plantation. The large trees shed a substantial amount of leaves, whose decay developed a water repellent layer. Runoff generation enhanced deep water penetration, through the phenomenon of finger flow. At the same time, due to the lack of a water repellent layer, runoff did not develop in the interdune area; eliminating the positive effect of water concentration. In addition, the soil in the interdune areas is richer in fine grained particle than the active dune crests, limiting thus the depth of water penetration and water availability for planted trees.

  16. Single-particle characterization of biomass burning organic aerosol (BBOA): evidence for non-uniform mixing of high molecular weight organics and potassium

    NASA Astrophysics Data System (ADS)

    Lee, Alex K. Y.; Willis, Megan D.; Healy, Robert M.; Wang, Jon M.; Jeong, Cheol-Heon; Wenger, John C.; Evans, Greg J.; Abbatt, Jonathan P. D.

    2016-05-01

    Biomass burning organic aerosol (BBOA) can be emitted from natural forest fires and human activities such as agricultural burning and domestic energy generation. BBOA is strongly associated with atmospheric brown carbon (BrC) that absorbs near-ultraviolet and visible light, resulting in significant impacts on regional visibility degradation and radiative forcing. The mixing state of BBOA can play a critical role in the prediction of aerosol optical properties. In this work, single-particle measurements from a Soot-Particle Aerosol Mass Spectrometer coupled with a light scattering module (LS-SP-AMS) were performed to examine the mixing state of BBOA, refractory black carbon (rBC), and potassium (K, a tracer for biomass burning aerosol) in an air mass influenced by wildfire emissions transported from northern Québec to Toronto, representing aged biomass burning plumes. Cluster analysis of single-particle measurements identified five BBOA-related particle types. rBC accounted for 3-14 wt % of these particle types on average. Only one particle type exhibited a strong ion signal for K+, with mass spectra characterized by low molecular weight organic species. The remaining four particle types were classified based on the apparent molecular weight of the BBOA constituents. Two particle types were associated with low potassium content and significant amounts of high molecular weight (HMW) organic compounds. Our observations indicate non-uniform mixing of particles within a biomass burning plume in terms of molecular weight and illustrate that HMW BBOA can be a key contributor to low-volatility BrC observed in BBOA particles. The average mass absorption efficiency of low-volatility BBOA is about 0.8-1.1 m2 g-1 based on a theoretical closure calculation. Our estimates indicate that low-volatility BBOA contributes ˜ 33-44 % of thermo-processed particle absorption at 405 nm; and almost all of the BBOA absorption was associated with low-volatility organics.

  17. SU-E-T-549: A Combinatorial Optimization Approach to Treatment Planning with Non-Uniform Fractions in Intensity Modulated Proton Therapy

    SciTech Connect

    Papp, D; Unkelbach, J

    2014-06-01

    Purpose: Non-uniform fractionation, i.e. delivering distinct dose distributions in two subsequent fractions, can potentially improve outcomes by increasing biological dose to the target without increasing dose to healthy tissues. This is possible if both fractions deliver a similar dose to normal tissues (exploit the fractionation effect) but high single fraction doses to subvolumes of the target (hypofractionation). Optimization of such treatment plans can be formulated using biological equivalent dose (BED), but leads to intractable nonconvex optimization problems. We introduce a novel optimization approach to address this challenge. Methods: We first optimize a reference IMPT plan using standard techniques that delivers a homogeneous target dose in both fractions. The method then divides the pencil beams into two sets, which are assigned to either fraction one or fraction two. The total intensity of each pencil beam, and therefore the physical dose, remains unchanged compared to the reference plan. The objectives are to maximize the mean BED in the target and to minimize the mean BED in normal tissues, which is a quadratic function of the pencil beam weights. The optimal reassignment of pencil beams to one of the two fractions is formulated as a binary quadratic optimization problem. A near-optimal solution to this problem can be obtained by convex relaxation and randomized rounding. Results: The method is demonstrated for a large arteriovenous malformation (AVM) case treated in two fractions. The algorithm yields a treatment plan, which delivers a high dose to parts of the AVM in one of the fractions, but similar doses in both fractions to the normal brain tissue adjacent to the AVM. Using the approach, the mean BED in the target was increased by approximately 10% compared to what would have been possible with a uniform reference plan for the same normal tissue mean BED.

  18. Erratum for the Appendix of "Measuring small compartment dimensions by probing diffusion dynamics via Non-uniform Oscillating-Gradient Spin-Echo (NOGSE) NMR" [J. Magn. Reson. 247 (2014) 110

    NASA Astrophysics Data System (ADS)

    Shemesh, Noam; Álvarez, Gonzalo A.; Frydman, Lucio

    2015-05-01

    This corrects a typo of Eq. (A4) in the Erratum [J. Magn. Reson. 247 (2014) 110] for the Appendix of "Measuring small compartment dimensions by probing diffusion dynamics via Non-uniform Oscillating-Gradient Spin-Echo (NOGSE) NMR". The Erratum should have read as follow:

  19. Coupling of Carbon Monoxide with Nitrogen Monoxide at a Frustrated Lewis Pair Template.

    PubMed

    Ye, Ke-Yin; Kehr, Gerald; Daniliuc, Constantin G; Liu, Lei; Grimme, Stefan; Erker, Gerhard

    2016-08-01

    Coupling of carbon monoxide with nitrogen monoxide was achieved at a frustrated Lewis pair template. This unique reaction uses hydride as an auxiliary, which reductively activates carbon monoxide at the frustrated Lewis pair. The CO/NO coupling reaction then takes place through a pathway involving a radical reaction in which the hydrogen atom auxiliary is eventually removed again. PMID:27328914

  20. Mars - Microwave detection of carbon monoxide

    NASA Technical Reports Server (NTRS)

    Kakar, R. K.; Walters, J. W.; Wilson, W. J.

    1977-01-01

    The 115-gigahertz microwave line of carbon monoxide has been detected in the spectrum of Mars. The measurement is sensitive to carbon monoxide between the surface and an altitude of approximately 50 kilometers in the Martian atmosphere. This extends the altitude region to well above that previously sensed.

  1. 29 CFR 1917.24 - Carbon monoxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... using gas detector tube units certified by NIOSH under 30 CFR part 11 or other measuring instruments... 29 Labor 7 2012-07-01 2012-07-01 false Carbon monoxide. 1917.24 Section 1917.24 Labor Regulations...) MARINE TERMINALS Marine Terminal Operations § 1917.24 Carbon monoxide. (a) Exposure limits. The...

  2. 29 CFR 1917.24 - Carbon monoxide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... using gas detector tube units certified by NIOSH under 30 CFR part 11 or other measuring instruments... 29 Labor 7 2011-07-01 2011-07-01 false Carbon monoxide. 1917.24 Section 1917.24 Labor Regulations...) MARINE TERMINALS Marine Terminal Operations § 1917.24 Carbon monoxide. (a) Exposure limits. The...

  3. 29 CFR 1917.24 - Carbon monoxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... using gas detector tube units certified by NIOSH under 30 CFR part 11 or other measuring instruments... 29 Labor 7 2013-07-01 2013-07-01 false Carbon monoxide. 1917.24 Section 1917.24 Labor Regulations...) MARINE TERMINALS Marine Terminal Operations § 1917.24 Carbon monoxide. (a) Exposure limits. The...

  4. 29 CFR 1917.24 - Carbon monoxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... using gas detector tube units certified by NIOSH under 30 CFR part 11 or other measuring instruments... 29 Labor 7 2014-07-01 2014-07-01 false Carbon monoxide. 1917.24 Section 1917.24 Labor Regulations...) MARINE TERMINALS Marine Terminal Operations § 1917.24 Carbon monoxide. (a) Exposure limits. The...

  5. 29 CFR 1917.24 - Carbon monoxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... using gas detector tube units certified by NIOSH under 30 CFR part 11 or other measuring instruments... 29 Labor 7 2010-07-01 2010-07-01 false Carbon monoxide. 1917.24 Section 1917.24 Labor Regulations...) MARINE TERMINALS Marine Terminal Operations § 1917.24 Carbon monoxide. (a) Exposure limits. The...

  6. Method of removing carbon monoxide from gases

    DOEpatents

    Gerstein, Bernard C.; Macaulay, David B.

    1976-06-01

    A process and catalyst are disclosed for purifying an atmosphere containing carbon monoxide by passing the atmosphere through a bed of a catalyst of TbO.sub.x, where x = 1.8 to 1.5, which oxidizes the carbon monoxide to carbon dioxide.

  7. Compartment Syndrome Resulting from Carbon Monoxide Poisoning.

    PubMed

    Serbest, Sancar; Belhan, Oktay; Gürger, Murat; Tosun, Haci Bayram

    2015-12-01

    Every year, especially in the cooler Fall and Winter months, hundreds of people die because of carbon monoxide poisoning. This occurs usually as an accident. It is a significant cause of poisoning worldwide. We present a case of compartment syndrome in both lower extremities with accompanying acute renal failure and systemic capillary leakage syndrome because of carbon monoxide poisoning. PMID:26588033

  8. Ignition limits of mixtures containing carbon monoxide

    SciTech Connect

    El'natanov, A.I.; Andreeva, N.V.; Strizhevskii, I.I.

    1983-05-01

    Much attention is being given to methods of production of carbon monoxide because of the need for savings of hydrocarbon feedstocks for industrial synthesis. Besides the traditional method of production of carbon monoxide (coal gasification), it can also be extracted from industrial discharges, which contain oxygen and other gases. For safe technological recovery processes it is necessary to know the ignition limits of mixtures which contain carbon monoxide, oxygen and an inert gas. The available data are quite limited: the ignition limits of mixtures of carbon monoxide with air or oxygen and also with air in which part of the nitrogen has been replaced by carbon dioxide. For this reason, a study was undertaken of the ignition limits of mixtures of carbon monoxide and air with carbon dioxide and argon - as substances having quite varied heat value - over a broad range.

  9. Room-temperature carbon monoxide oxidation by oxygen over Pt/Al2O3 mediated by reactive platinum carbonates

    NASA Astrophysics Data System (ADS)

    Newton, Mark A.; Ferri, Davide; Smolentsev, Grigory; Marchionni, Valentina; Nachtegaal, Maarten

    2015-10-01

    Room-temperature carbon monoxide oxidation, important for maintaining clean air among other applications, is challenging even after a century of research into carbon monoxide oxidation. Here we report using time-resolved diffuse reflectance infrared spectroscopy, X-ray absorption fine structure spectroscopy and mass spectrometry a platinum carbonate-mediated mechanism for the room-temperature oxidation of carbon monoxide. By applying a periodic reduction-oxidation mode of operation we further show that this behaviour is reversible and can be formed into a catalytic cycle that requires molecular communication between metallic platinum nanoparticles and highly dispersed oxidic platinum centres. A new possibility for the attainment of low-temperature oxidation of carbon monoxide is therefore demonstrated.

  10. Room-temperature carbon monoxide oxidation by oxygen over Pt/Al2O3 mediated by reactive platinum carbonates

    PubMed Central

    Newton, Mark A.; Ferri, Davide; Smolentsev, Grigory; Marchionni, Valentina; Nachtegaal, Maarten

    2015-01-01

    Room-temperature carbon monoxide oxidation, important for maintaining clean air among other applications, is challenging even after a century of research into carbon monoxide oxidation. Here we report using time-resolved diffuse reflectance infrared spectroscopy, X-ray absorption fine structure spectroscopy and mass spectrometry a platinum carbonate-mediated mechanism for the room-temperature oxidation of carbon monoxide. By applying a periodic reduction–oxidation mode of operation we further show that this behaviour is reversible and can be formed into a catalytic cycle that requires molecular communication between metallic platinum nanoparticles and highly dispersed oxidic platinum centres. A new possibility for the attainment of low-temperature oxidation of carbon monoxide is therefore demonstrated. PMID:26489669

  11. Room-temperature carbon monoxide oxidation by oxygen over Pt/Al2O3 mediated by reactive platinum carbonates.

    PubMed

    Newton, Mark A; Ferri, Davide; Smolentsev, Grigory; Marchionni, Valentina; Nachtegaal, Maarten

    2015-01-01

    Room-temperature carbon monoxide oxidation, important for maintaining clean air among other applications, is challenging even after a century of research into carbon monoxide oxidation. Here we report using time-resolved diffuse reflectance infrared spectroscopy, X-ray absorption fine structure spectroscopy and mass spectrometry a platinum carbonate-mediated mechanism for the room-temperature oxidation of carbon monoxide. By applying a periodic reduction-oxidation mode of operation we further show that this behaviour is reversible and can be formed into a catalytic cycle that requires molecular communication between metallic platinum nanoparticles and highly dispersed oxidic platinum centres. A new possibility for the attainment of low-temperature oxidation of carbon monoxide is therefore demonstrated. PMID:26489669

  12. The Carbon Monoxide Tape Recorder

    NASA Technical Reports Server (NTRS)

    Schoeberl, M. R.; Duncan, B. N.; Douglass, A. R.; Waters, J.; Livesey, N.; Read, W.; Filipiak, M.

    2006-01-01

    Using Aura MLS data we have identified the stratospheric tape recorder in carbon monoxide (CO). Unlike the water vapor tape recorder, which is controlled by upper troposphere processes, the CO tape recorder is linked to seasonal biomass burning. Since CO has a lifetime of only a few months, the CO tape recorder barely extends above 20 km. The tape head for CO appears to be close to 360K near the same location as the water vapor tape head [Read et al, 20041. Both tape heads are below the equatorial cold point tropopause but above the base of the tropical tropopause layer. The tape recorder signal becomes more distinct from 360K to 380K suggesting that convective detrainment of plays a decreasingly important role with altitude. The Global Modeling Initiative chemical transport model forced by the climatology of biomass burning reproduces the CO tape recorder.

  13. Carbon monoxide and the burning earth

    SciTech Connect

    Newell, R.E.; Reichle, H.G. Jr.; Seiler, W.

    1989-10-01

    Carbon monoxide is one of many gases whose presence in the atmosphere is blamed largely on industrial activity in the Northern Hemisphere. Data collected by the authors show that the gas is also abundant in the Southern Hemisphere, where it comes mainly from the burning of tropical rain forests and savannas. The high levels of carbon monoxide confirm other evidence that the rain forests are being diminished rapidly, which may affect the climates of these regions as well as globally. Increases in carbon monoxide could also encourage the accumulation of pollutant gases such as ozone and methane. The first is highly toxic to plants and the second would add to the greenhouse effect.

  14. Engineering evidence for carbon monoxide toxicity cases.

    PubMed

    Galatsis, Kosmas

    2016-07-01

    Unintentional carbon monoxide poisonings and fatalities lead to many toxicity cases. Given the unusual physical properties of carbon monoxide-in that the gas is odorless and invisible-unorganized and erroneous methods in obtaining engineering evidence as required during the discovery process often occurs. Such evidence gathering spans domains that include building construction, appliance installation, industrial hygiene, mechanical engineering, combustion and physics. In this paper, we attempt to place a systematic framework that is relevant to key aspects in engineering evidence gathering for unintentional carbon monoxide poisoning cases. Such a framework aims to increase awareness of this process and relevant issues to help guide legal counsel and expert witnesses. PMID:26137848

  15. Tests confirm gas heat as monoxide source

    SciTech Connect

    Besch, E.

    1984-03-01

    Six tests were conducted to demonstrate the potential for natural gas or oil-fired forced warm air heating equipment to produce carbon monoxide emission when the combustion process is impeded by typical causes found in households. In the case of the gas-fired units, impeded combustion produced a smell of aldehyde and various levels of carbon monoxide emission; all within the level dangerous to health. It was concluded that oil-fired warm air systems do not pose a carbon monoxide danger but that natural gas warm air systems do pose a real danger and should be so identified.

  16. 40 CFR 52.1237 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 4 2012-07-01 2012-07-01 false Control strategy: Carbon monoxide. 52... strategy: Carbon monoxide. (a) The base year carbon monoxide emission inventory requirement of section 187... Metropolitan Area and Minneapolis-St. Paul Metropolitan Area. (b) Approval—The 1993 carbon monoxide...

  17. 40 CFR 91.317 - Carbon monoxide analyzer calibration.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 20 2011-07-01 2011-07-01 false Carbon monoxide analyzer calibration... Provisions § 91.317 Carbon monoxide analyzer calibration. (a) Calibrate the NDIR carbon monoxide analyzer... service and annually thereafter, check the NDIR carbon monoxide analyzer for response to water vapor...

  18. 40 CFR 91.317 - Carbon monoxide analyzer calibration.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 21 2012-07-01 2012-07-01 false Carbon monoxide analyzer calibration... Provisions § 91.317 Carbon monoxide analyzer calibration. (a) Calibrate the NDIR carbon monoxide analyzer... service and annually thereafter, check the NDIR carbon monoxide analyzer for response to water vapor...

  19. 40 CFR 52.2353 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. Determination. EPA has determined that the Provo carbon monoxide “moderate” nonattainment area attained the carbon monoxide national ambient air quality standard by December 31, 1995....

  20. 40 CFR 52.2353 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 4 2011-07-01 2011-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. Determination. EPA has determined that the Provo carbon monoxide “moderate” nonattainment area attained the carbon monoxide national ambient air quality standard by December 31, 1995....

  1. 40 CFR 52.1682 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. (a) Approval—The November 13, 1992 revision to the carbon monoxide state implementation... attainment of the National Ambient Air Quality Standard for carbon monoxide through the year 2003....

  2. 40 CFR 91.317 - Carbon monoxide analyzer calibration.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 20 2014-07-01 2013-07-01 true Carbon monoxide analyzer calibration... Provisions § 91.317 Carbon monoxide analyzer calibration. (a) Calibrate the NDIR carbon monoxide analyzer... service and annually thereafter, check the NDIR carbon monoxide analyzer for response to water vapor...

  3. 40 CFR 52.1237 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 4 2011-07-01 2011-07-01 false Control strategy: Carbon monoxide. 52... strategy: Carbon monoxide. (a) The base year carbon monoxide emission inventory requirement of section 187... Metropolitan Area and Minneapolis-St. Paul Metropolitan Area. (b) Approval—The 1993 carbon monoxide...

  4. 40 CFR 52.1682 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 4 2013-07-01 2013-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. (a) Approval—The November 13, 1992 revision to the carbon monoxide state implementation... attainment of the National Ambient Air Quality Standard for carbon monoxide through the year 2003....

  5. 40 CFR 52.1237 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Control strategy: Carbon monoxide. 52... strategy: Carbon monoxide. (a) The base year carbon monoxide emission inventory requirement of section 187... Metropolitan Area and Minneapolis-St. Paul Metropolitan Area. (b) Approval—The 1993 carbon monoxide...

  6. 40 CFR 52.1237 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 4 2013-07-01 2013-07-01 false Control strategy: Carbon monoxide. 52... strategy: Carbon monoxide. (a) The base year carbon monoxide emission inventory requirement of section 187... Metropolitan Area and Minneapolis-St. Paul Metropolitan Area. (b) Approval—The 1993 carbon monoxide...

  7. 40 CFR 52.1682 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 4 2012-07-01 2012-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. (a) Approval—The November 13, 1992 revision to the carbon monoxide state implementation... attainment of the National Ambient Air Quality Standard for carbon monoxide through the year 2003....

  8. 40 CFR 52.2353 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 5 2013-07-01 2013-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. Determination. EPA has determined that the Provo carbon monoxide “moderate” nonattainment area attained the carbon monoxide national ambient air quality standard by December 31, 1995....

  9. 40 CFR 52.2353 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 5 2012-07-01 2012-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. Determination. EPA has determined that the Provo carbon monoxide “moderate” nonattainment area attained the carbon monoxide national ambient air quality standard by December 31, 1995....

  10. 40 CFR 52.1682 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 4 2014-07-01 2014-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. (a) Approval—The November 13, 1992 revision to the carbon monoxide state implementation... attainment of the National Ambient Air Quality Standard for carbon monoxide through the year 2003....

  11. 40 CFR 52.1237 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 4 2014-07-01 2014-07-01 false Control strategy: Carbon monoxide. 52... strategy: Carbon monoxide. (a) The base year carbon monoxide emission inventory requirement of section 187... Metropolitan Area and Minneapolis-St. Paul Metropolitan Area. (b) Approval—The 1993 carbon monoxide...

  12. 40 CFR 52.1682 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 4 2011-07-01 2011-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. (a) Approval—The November 13, 1992 revision to the carbon monoxide state implementation... attainment of the National Ambient Air Quality Standard for carbon monoxide through the year 2003....

  13. 40 CFR 91.317 - Carbon monoxide analyzer calibration.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Carbon monoxide analyzer calibration... Provisions § 91.317 Carbon monoxide analyzer calibration. (a) Calibrate the NDIR carbon monoxide analyzer... service and annually thereafter, check the NDIR carbon monoxide analyzer for response to water vapor...

  14. 40 CFR 52.2353 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 5 2014-07-01 2014-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. Determination. EPA has determined that the Provo carbon monoxide “moderate” nonattainment area attained the carbon monoxide national ambient air quality standard by December 31, 1995....

  15. Protecting Children from Carbon Monoxide Poisoning

    MedlinePlus

    ... monoxide poisoning increases after disasters when gasoline- or diesel-powered generators may be more frequently used to ... can mimic symptoms of sea sickness. Schedule regular engine and exhaust system maintenance. Consider installing a carbon ...

  16. Polymer-Based Carbon Monoxide Sensors

    NASA Technical Reports Server (NTRS)

    Homer, M. L.; Shevade, A. V.; Zhou, H.; Kisor, A. K.; Lara, L. M.; Yen, S.-P. S.; Ryan, M. A.

    2010-01-01

    Polymer-based sensors have been used primarily to detect volatile organics and inorganics; they are not usually used for smaller, gas phase molecules. We report the development and use of two types of polymer-based sensors for the detection of carbon monoxide. Further understanding of the experimental results is also obtained by performing molecular modeling studies to investigate the polymer-carbon monoxide interactions. The first type is a carbon-black-polymer composite that is comprised of a non-conducting polymer base that has been impregnated with carbon black to make it conducting. These chemiresistor sensors show good response to carbon monoxide but do not have a long lifetime. The second type of sensor has a non-conducting polymer base but includes both a porphyrin-functionalized polypyrrole and carbon black. These sensors show good, repeatable and reversible response to carbon monoxide at room temperature.

  17. A Fluorescent Source NDIR Carbon Monoxide Analyzer

    NASA Technical Reports Server (NTRS)

    Link, W. T.; McClatchie, E. A.; Watson, D. A.; Compher, A. B.

    1971-01-01

    This paper describes a new technique for measuring trace quantities of carbon monoxide by the nondispersive infrared (NDIR) methods. The technique uses the property of infrared fluorescence in a gas to generate a specific source of radiation which is an exact match of the absorption spectrum of the fundamental band of carbon monoxide. This results in an instrument with high sensitivity and specificity for CO. A novel method of referencing using an isotopic species of CO confers great stability on the instrument.

  18. An unusual case of carbon monoxide poisoning.

    PubMed Central

    Auger, P L; Levesque, B; Martel, R; Prud'homme, H; Bellemare, D; Barbeau, C; Lachance, P; Rhainds, M

    1999-01-01

    Carbon monoxide, a gas originating from incomplete combustion of carbon-based fuels, is an important cause of human deaths. In this paper, we describe an unusual carbon monoxide poisoning in a dwelling without obvious sources of combustion gases, for which two adults had to be treated in a hyperbaric chamber. Carbon monoxide readings were taken in the house and in the neighboring homes. Methane gas and nitrogen oxide levels were also monitored in the house air. Soil samples were collected around the house and tested for hydrocarbon residues. The investigation revealed the presence of a pocket of carbon monoxide under the foundation of the house. The first readings revealed carbon monoxide levels of 500 ppm in the basement. The contamination lasted for a week. The investigation indicated that the probable source of contamination was the use of explosives at a nearby rain sewer construction site. The use of explosives in a residential area can constitute a major source of carbon monoxide for the neighboring populations. This must be investigated, and public health authorities, primary-care physicians, governmental authorities, and users and manufacturers of explosives must be made aware of this problem. Images Figure 1 Figure 2 PMID:10379009

  19. Device for staged carbon monoxide oxidation

    DOEpatents

    Vanderborgh, Nicholas E.; Nguyen, Trung V.; Guante, Jr., Joseph

    1993-01-01

    A method and apparatus for selectively oxidizing carbon monoxide in a hydrogen rich feed stream. The method comprises mixing a feed stream consisting essentially of hydrogen, carbon dioxide, water and carbon monoxide with a first predetermined quantity of oxygen (air). The temperature of the mixed feed/oxygen stream is adjusted in a first the heat exchanger assembly (20) to a first temperature. The mixed feed/oxygen stream is sent to reaction chambers (30,32) having an oxidation catalyst contained therein. The carbon monoxide of the feed stream preferentially absorbs on the catalyst at the first temperature to react with the oxygen in the chambers (30,32) with minimal simultaneous reaction of the hydrogen to form an intermediate hydrogen rich process stream having a lower carbon monoxide content than the feed stream. The elevated outlet temperature of the process stream is carefully controlled in a second heat exchanger assembly (42) to a second temperature above the first temperature. The process stream is then mixed with a second predetermined quantity of oxygen (air). The carbon monoxide of the process stream preferentially reacts with the second quantity of oxygen in a second stage reaction chamber (56) with minimal simultaneous reaction of the hydrogen in the process stream. The reaction produces a hydrogen rich product stream having a lower carbon monoxide content than the process stream. The product stream is then cooled in a third heat exchanger assembly (72) to a third predetermined temperature. Three or more stages may be desirable, each with metered oxygen injection.

  20. Therapeutic Applications of Carbon Monoxide

    PubMed Central

    Knauert, Melissa; Vangala, Sandeep; Haslip, Maria; Lee, Patty J.

    2013-01-01

    Heme oxygenase-1 (HO-1) is a regulated enzyme induced in multiple stress states. Carbon monoxide (CO) is a product of HO catalysis of heme. In many circumstances, CO appears to functionally replace HO-1, and CO is known to have endogenous anti-inflammatory, anti-apoptotic, and antiproliferative effects. CO is well studied in anoxia-reoxygenation and ischemia-reperfusion models and has advanced to phase II trials for treatment of several clinical entities. In alternative injury models, laboratories have used sepsis, acute lung injury, and systemic inflammatory challenges to assess the ability of CO to rescue cells, organs, and organisms. Hopefully, the research supporting the protective effects of CO in animal models will translate into therapeutic benefits for patients. Preclinical studies of CO are now moving towards more complex damage models that reflect polymicrobial sepsis or two-step injuries, such as sepsis complicated by acute respiratory distress syndrome. Furthermore, co-treatment and post-treatment with CO are being explored in which the insult occurs before there is an opportunity to intervene therapeutically. The aim of this review is to discuss the potential therapeutic implications of CO with a focus on lung injury and sepsis-related models. PMID:24648866

  1. Catalytic hydrogenation of carbon monoxide

    SciTech Connect

    Wayland, B.B.

    1992-12-01

    This project is focused on developing strategies to accomplish the reduction and hydrogenation of carbon monoxide to produce organic oxygenates at mild conditions. Our approaches to this issue are based on the recognition that rhodium macrocycles have unusually favorable thermodynamic values for producing a series of intermediate implicated in the catalytic hydrogenation of CO. Observations of metalloformyl complexes produced by reactions of H{sub 2} and CO, and reductive coupling of CO to form metallo {alpha}-diketone species have suggested a multiplicity of routes to organic oxygenates that utilize these species as intermediates. Thermodynamic and kinetic-mechanistic studies are used in constructing energy profiles for a variety of potential pathways, and these schemes are used in guiding the design of new metallospecies to improve the thermodynamic and kinetic factors for individual steps in the overall process. Variation of the electronic and steric effects associated with the ligand arrays along with the influences of the reaction medium provide the chemical tools for tuning these factors. Emerging knowledge of the factors that contribute to M-H, M-C and M-O bond enthalpies is directing the search for ligand arrays that will expand the range of metal species that have favorable thermodynamic parameters to produce the primary intermediates for CO hydrogenation. Studies of rhodium complexes are being extended to non-macrocyclic ligand complexes that emulate the favorable thermodynamic features associated with rhodium macrocycles, but that also manifest improved reaction kinetics. Multifunctional catalyst systems designed to couple the ability of rhodium complexes to produce formyl and diketone intermediates with a second catalyst that hydrogenates these imtermediates are promising approaches to accomplish CO hydrogenation at mild conditions.

  2. [Carbon monoxide contamination: an environmental health problem].

    PubMed

    Téllez, Jairo; Rodríguez, Alba; Fajardo, Alvaro

    2006-01-01

    Carbon monoxide is considered to be a major factor contaminating earth's atmosphere. The main sources producing this contamination are cars using gasoline or diesel fuel and industrial processes using carbon compounds; these two are responsible for 80% of carbon monoxide being emitted to the atmosphere. This substance has a well-known toxic effect on human beings and its acute poisonous effects (including death) have been widely studied; however, its long-term chronic effects are still not known. During the last few years, experimental research on animals and studies of human epidemiology have established the relationship between chronic exposure to low and middle levels of carbon monoxide in breathable air and adverse effects on human health, especially on organs consuming large amounts of oxygen such as the heart and brain. Harmful cardiovascular and neuropsychological effects have been documented in carbon monoxide concentration in air of less than 25 ppm and in carboxyhaemoglobin levels in blood of less than 10%. The main cardiac damage described to date has been high blood pressure, cardiac arrhythm and electrocardiograph signs of ischemia. Lack of memory, attention, concentration and Parkinson-type altered movement are the neuropsychological changes most frequently associated with chronic exposure to low levels of carbon monoxide and carboxyhaemoglobin. PMID:16703967

  3. Anisotropic thermal conductivity of semiconducting graphene monoxide

    NASA Astrophysics Data System (ADS)

    Pu, H. H.; Rhim, S. H.; Hirschmugl, C. J.; Gajdardziska-Josifovska, M.; Weinert, M.; Chen, J. H.

    2013-06-01

    The intrinsic thermal conductivity of monolayer graphene monoxide is determined via first-principles calculations. The phonon transport in graphene monoxide is anisotropic, with the lattice thermal conductivity along the armchair direction (…C-2O-C…) about five times higher than that along the zigzag (…C-C…) direction. The predicted thermal conductivity (>3000 Wm-1K-1 at 300 K) of graphene monoxide is 80% of that of graphene along the armchair direction for large sample lateral sizes (>5 μm). In addition, heat is predominantly carried by longitudinal acoustic phonons along the armchair direction, while the contribution from the transverse acoustic phonon mode is prevalent along the zigzag direction.

  4. Carbon monoxide sensor and method of use

    DOEpatents

    Dutta, Prabir K.; Swartz, Scott L.; Holt, Christopher T.; Revur, Ramachandra Rao

    2006-01-10

    A sensor and method of use for detection of low levels of carbon monoxide in gas mixtures. The approach is based on the change in an electrical property (for example: resistance) that occurs when carbon monoxide is selectively absorbed by a film of copper chloride (or other metal halides). The electrical property change occurs rapidly with both increasing and decreasing CO contents, varies with the amount of CO from the gas stream, and is insensitive to the presence of hydrogen. To make a sensor using this approach, the metal halide film will deposited onto an alumina substrate with electrodes. The sensor may be maintained at the optimum temperature with a thick film platinum heater deposited onto the opposite face of the substrate. When the sensor is operating at an appropriate (and constant) temperature, the magnitude of the electrical property measured between the interdigital electrodes will provide a measure of the carbon monoxide content of the gas.

  5. [Carbon monoxide metabolism by photosynthetic bacteria]. Progress report

    SciTech Connect

    Not Available

    1989-12-31

    Research continued on the metabolism of carbon monoxide by Rhodospirillum rubrum. This report discusses progress on the activity, induction, inhibition, and spectroscopic analysis of the enzyme Carbon Monoxide Dehydrogenase. (CBS)

  6. CPSC Warns of Carbon Monoxide Poisoning with Camping Equipment

    MedlinePlus

    ... Warns of Carbon Monoxide Poisoning Hazard with Camping Equipment The U.S. Consumer Product Safety Commission (CPSC) warns ... about the carbon monoxide (CO) hazard with camping equipment. CO can kill you! From 2002–2006, CPSC ...

  7. Optimal wavelengths obtained from laws analogous to the Wien's law for monospectral and bispectral methods, and general methodology for multispectral temperature measurements taking into account global transfer function including non-uniform emissivity of surfaces

    NASA Astrophysics Data System (ADS)

    Rodiet, Christophe; Remy, Benjamin; Degiovanni, Alain

    2016-05-01

    In this paper, it is shown how to select the optimal wavelengths minimizing the relative error and the standard deviation of the temperature. Furthermore, it is shown that the optimal wavelengths in mono-spectral and bi-spectral methods (for a Planck's law) can be determined by laws analogous to the displacement Wien's law. The simplicity of these laws can thus allow real-time selection of optimal wavelengths for a control/optimization of industrial processes, for example. A more general methodology to obtain the optimal wavelengths selection in a multi-spectral method (taking into account the spectral variations of the global transfer function including the emissivity variations) for temperature measurement of surfaces exhibiting non-uniform emissivity, is also presented. This latter can then find an interest in glass furnaces temperature measurement with spatiotemporal non-uniformities of emissivity, the control of biomass pyrolysis, the surface temperature measurement of buildings or heating devices, for example. The goal consists of minimizing the standard deviation of the estimated temperature (optimal design experiment). For the multi-spectral method, two cases will be treated: optimal global and optimal constrained wavelengths selection (to the spectral range of the detector, for example). The estimated temperature results obtained by different models and for different number of parameters and wavelengths are compared. These different points are treated from theoretical, numerical and experimental points of view.

  8. 21 CFR 868.1430 - Carbon monoxide gas analyzer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Carbon monoxide gas analyzer. 868.1430 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1430 Carbon monoxide gas analyzer. (a) Identification. A carbon monoxide gas analyzer is a device intended to measure the concentration of...

  9. 40 CFR 90.317 - Carbon monoxide analyzer calibration.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 20 2011-07-01 2011-07-01 false Carbon monoxide analyzer calibration... Emission Test Equipment Provisions § 90.317 Carbon monoxide analyzer calibration. (a) Calibrate the NDIR carbon monoxide analyzer as described in this section. (b) Initial and periodic interference. Prior...

  10. 40 CFR 52.1887 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 4 2014-07-01 2014-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. (a) Part D—Approval—The following portions of the Ohio plan are approved: (1) The carbon...) The carbon monoxide attainment and reasonable further progress demonstrations for the following...

  11. 40 CFR 52.1373 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 4 2014-07-01 2014-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. (a) On July 8, 1997, the Governor of Montana submitted revisions to the SIP narrative for the Missoula carbon monoxide control plan. (b) Revisions to the Montana State Implementation...

  12. 40 CFR 52.1887 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 4 2012-07-01 2012-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. (a) Part D—Approval—The following portions of the Ohio plan are approved: (1) The carbon...) The carbon monoxide attainment and reasonable further progress demonstrations for the following...

  13. 40 CFR 52.1132 - Control strategy: Carbon Monoxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 4 2012-07-01 2012-07-01 false Control strategy: Carbon Monoxide. 52... strategy: Carbon Monoxide. (a) Approval—On November 13, 1992, the Massachusetts Department of Environmental Protection submitted a revision to the carbon monoxide State Implementation Plan for the 1990 base...

  14. 40 CFR 86.122-78 - Carbon monoxide analyzer calibration.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 19 2014-07-01 2014-07-01 false Carbon monoxide analyzer calibration... Complete Heavy-Duty Vehicles; Test Procedures § 86.122-78 Carbon monoxide analyzer calibration. The NDIR carbon monoxide analyzer shall receive the following initial and periodic calibrations: (a) Initial...

  15. 40 CFR 52.1528 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Control strategy: Carbon monoxide. 52... strategy: Carbon monoxide. (a) Approval—On February 1, 1999, the New Hampshire Department of Environmental... program for carbon monoxide that ceased operating on January 1, 1995. The Nashua...

  16. 40 CFR 52.1373 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Control strategy: Carbon monoxide. 52...: Carbon monoxide. (a) On July 8, 1997, the Governor of Montana submitted revisions to the SIP narrative for the Missoula carbon monoxide control plan. (b) Revisions to the Montana State Implementation...

  17. 40 CFR 52.1528 - Control strategy: Carbon monoxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 4 2014-07-01 2014-07-01 false Control strategy: Carbon monoxide. 52... strategy: Carbon monoxide. (a) Approval—On February 1, 1999, the New Hampshire Department of Environmental... program for carbon monoxide that ceased operating on January 1, 1995. The Nashua...

  18. 40 CFR 86.122-78 - Carbon monoxide analyzer calibration.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 18 2011-07-01 2011-07-01 false Carbon monoxide analyzer calibration... Complete Heavy-Duty Vehicles; Test Procedures § 86.122-78 Carbon monoxide analyzer calibration. The NDIR carbon monoxide analyzer shall receive the following initial and periodic calibrations: (a) Initial...

  19. 40 CFR 52.1132 - Control strategy: Carbon Monoxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Control strategy: Carbon Monoxide. 52... strategy: Carbon Monoxide. (a) Approval—On November 13, 1992, the Massachusetts Department of Environmental Protection submitted a revision to the carbon monoxide State Implementation Plan for the 1990 base...

  20. 21 CFR 868.1430 - Carbon monoxide gas analyzer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Carbon monoxide gas analyzer. 868.1430 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1430 Carbon monoxide gas analyzer. (a) Identification. A carbon monoxide gas analyzer is a device intended to measure the concentration of...