Leveraged resources and systems changes in community collaboration.
Harper, Christopher R; Kuperminc, Gabriel P; Weaver, Scott R; Emshoff, Jim; Erickson, Steve
2014-12-01
Most models of community collaboration emphasize the ability of diverse partners to come together to enact systematic changes that improve the health of individuals and communities. The ability of these groups to leverage resources is thought to be an important marker of successful collaboration and eventual improvements in community health. However, there is a paucity of research addressing linkages between systems change activities and leveraged resources. This study used a sample of collaboratives (N = 157) that received technical assistance and funding through the Georgia Family Connection Partnership (GaFCP) between 2006 and 2007. Data were collected from collaborative report of activities and funding, member ratings of collaborative functioning, and characteristics of the communities served by the collaboratives drawn from US Census data. Cross-lagged regression models tested longitudinal associations between systems change activities and leveraged dollars. The results indicated that systems change activities predict increased leveraging of resources from state/federal and private partners. However, there was no evidence that systems changes were linked with leveraging resources from local groups and agencies. These findings have important implications for providing technical assistance and training to health partnerships. Furthermore, future research should consider the relative strength of different systems change activities in relation to the ability of coalitions to leverage resources. PMID:25267252
Leveraged resources and systems changes in community collaboration.
Harper, Christopher R; Kuperminc, Gabriel P; Weaver, Scott R; Emshoff, Jim; Erickson, Steve
2014-12-01
Most models of community collaboration emphasize the ability of diverse partners to come together to enact systematic changes that improve the health of individuals and communities. The ability of these groups to leverage resources is thought to be an important marker of successful collaboration and eventual improvements in community health. However, there is a paucity of research addressing linkages between systems change activities and leveraged resources. This study used a sample of collaboratives (N = 157) that received technical assistance and funding through the Georgia Family Connection Partnership (GaFCP) between 2006 and 2007. Data were collected from collaborative report of activities and funding, member ratings of collaborative functioning, and characteristics of the communities served by the collaboratives drawn from US Census data. Cross-lagged regression models tested longitudinal associations between systems change activities and leveraged dollars. The results indicated that systems change activities predict increased leveraging of resources from state/federal and private partners. However, there was no evidence that systems changes were linked with leveraging resources from local groups and agencies. These findings have important implications for providing technical assistance and training to health partnerships. Furthermore, future research should consider the relative strength of different systems change activities in relation to the ability of coalitions to leverage resources.
Leveraging Resources to Close the Divide
ERIC Educational Resources Information Center
Rourke, James R.
2007-01-01
A host of real and perceived chasms divide students who achieve high academic standards and those who fail to meet them: varying expectations, economic status, resources, cultural and racial preconceptions, inappropriate standards, and so on. Yet as with all human endeavors throughout history, inventors, innovators, and risk takers rise to the…
Financing Community Schools: Leveraging Resources to Support Student Success
ERIC Educational Resources Information Center
Blank, Martin J.; Jacobson, Reuben; Melaville, Atelia; Pearson, Sarah S.
2010-01-01
Community schools are one of the most efficient and effective strategies to improve outcomes for students as well as families and communities. Community schools leverage public and private investments by generating additional financial resources from partners and other sources. This report looks at how community schools finance their work. It…
Shared resources, shared costs--leveraging biocuration resources.
Orchard, Sandra; Hermjakob, Henning
2015-01-01
The manual curation of the information in biomedical resources is an expensive task. This article argues the value of this approach in comparison with other apparently less costly options, such as automated annotation or text-mining, then discusses ways in which databases can make cost savings by sharing infrastructure and tool development. Sharing curation effort is a model already being adopted by several data resources. Approaches taken by two of these, the Gene Ontology annotation effort and the IntAct molecular interaction database, are reviewed in more detail. These models help to ensure long-term persistence of curated data and minimizes redundant development of resources by multiple disparate groups.
Route Instruction Mechanism for Mobile Users Leveraging Distributed Wireless Resources
NASA Astrophysics Data System (ADS)
Kakehi, Takeshi; Shinkuma, Ryoichi; Murase, Tutomu; Motoyoshi, Gen; Yamori, Kyoko; Takahashi, Tatsuro
The market growths of smart-phones and thin clients have been significantly increasing communication traffic in mobile networks. To handle the increased traffic, network operators should consider how to leverage distributed wireless resources such as distributed spots of wireless local access networks. In this paper, we consider the system where multiple moving users share distributed wireless access points on their traveling routes between their start and goal points and formulate as an optimization problem. Then, we come up with three algorithms as a solution for the problem. The key idea here is ‘longcut route instruction’, in which users are instructed to choose a traveling route where less congested access points are available; even if the moving distance increases, the throughput for users in the system would improve. In this paper, we define the gain function. Moreover, we analyze the basic characteristics of the system using as a simple model as possible.
Hydraulic machine with non-uniform cascade
NASA Astrophysics Data System (ADS)
Haluza, M.; Pochylý, F.; Habán, V.
2012-11-01
In this article is introduced the sentence of an extension of operational zone of hydraulic machines. The problems of its extending is based on the design of non-uniform cascade. The non-uniform cascade is connected with other factors. The change of own frequency of the runner of a hydraulic machine and pressure pulsations. The suitable construction of non-uniform cascade is introduced on the results of computational simulation and experiment.
2009-04-01
This report documents implementation strategies to leverage public and private resources for the development of an adequate national security workforce as part of the National Security Preparedness Project (NSPP), being performed under a U.S. Department of Energy (DOE)/National Nuclear Security Administration (NNSA) grant. There are numerous efforts across the United States to develop a properly skilled and trained national security workforce. Some of these efforts are the result of the leveraging of public and private dollars. As budget dollars decrease and the demand for a properly skilled and trained national security workforce increases, it will become even more important to leverage every education and training dollar. This report details some of the efforts that have been implemented to leverage public and private resources, as well as implementation strategies to further leverage public and private resources.
A system simulation development project: Leveraging resources through partnerships
NASA Technical Reports Server (NTRS)
Drummond, Colin K.; Owen, A. Karl; Davis, Milt W.
1995-01-01
Partnerships between government agencies are an intellectually attractive method of conducting scientific research; the goal is to establish mutually beneficial participant roles for technology exchange that ultimately pays-off in a stronger R&D program for each partner. Anticipated and current aerospace research budgetary pressures through the 90's provide additional impetus for Government research agencies to candidly assess their R&D for those simulation activities no longer unique enough to warrant 'going it alone,' or for those elements where partnerships or teams can offset development costs. This paper describes a specific inter-agency system simulation activity that leverages the development cost of mutually beneficial R&D. While the direct positive influence of partnerships on complex technology developments is our main thesis, we also address on-going teaming issues and hope to impart to the reader the immense indirect (sometimes immeasurable) benefits that meaningful interagency partnerships can produce.
Think Tank on Metabolomics and Prospective Cohorts: How to Leverage Resources
This Think Tank identified resources that can be used collaboratively across prospective cohorts; developed strategies to leverage resources for advancing the use of metabolomics in prospective cohort studies; identified the best strategies for performing analyses using metabolomics data across multiple studies; and, established a collaborative group that will identify and tackle research projects that cannot be effectively investigated by one independent group.
2009-02-01
This report documents the identification of strategies to leverage public and private resources for the development of an adequate national security workforce as part of the National Security Preparedness Project (NSPP).There are numerous efforts across the United States to develop a properly skilled and trained national security workforce. Some of these efforts are the result of the leveraging of public and private dollars. As budget dollars decrease and the demand for a properly skilled and trained national security workforce increases, it will become even more important to leverage every education and training dollar. The leveraging of dollars serves many purposes. These include increasing the amount of training that can be delivered and therefore increasing the number of people reached, increasing the number and quality of public/private partnerships, and increasing the number of businesses that are involved in the training of their future workforce.
Leveraging R&D Resources via the Joint LLC Model
NASA Astrophysics Data System (ADS)
Ganz, Matthew W.
2008-03-01
government and commercial entities. The central themes to HRL’s business model are innovation, value and leverage. Leverage is key to the company’s success. HRL’s business model has been carefully honed to allow its parent companies to perform proprietary R&D in certain areas and joint, collaborative R&D among the LLC members in others. The intellectual property arrangements are skillfully organized so that the LLC Members receive a greater than 4:1 leverage of their research dollars in terms of the IP rights gained. This briefing will describe an overview of the current industrial research environment, HRL’s business model, and challenges to future success.
Dynamic Pathfinders: Leveraging Your OPAC to Create Resource Guides
ERIC Educational Resources Information Center
Hunter, Ben
2008-01-01
Library pathfinders are a time-tested method of leading library users to important resources. However, paper-based pathfinders suffer from space limitations, and both paper-based and Web-based pathfinders require frequent updates to keep up with new library acquisitions. This article details a step-by-step method to create an online dynamic…
Financing Community Schools: Leveraging Resources to Support Student Success. Executive Summary
ERIC Educational Resources Information Center
Coalition for Community Schools, 2010
2010-01-01
Community schools are one of the most efficient and effective strategies to improve outcomes for students as well as families and communities. Community schools leverage public and private investments by generating additional financial resources from partners and other sources. This report looks at how community schools finance their work. It…
Diverse Language Profiles: Leveraging Resources of Potential Bilingual Teachers of Color
ERIC Educational Resources Information Center
Athanases, Steven Z.; Banes, Leslie C.; Wong, Joanna W.
2015-01-01
Bilingual prospective teachers of color may possess experiences and knowledge particularly suitable for teaching linguistically diverse students but may need guidance and support to leverage such resources for teaching. In a class of 76 undergraduates, with a focus on bilingual students of color intending to teach, this study used self-reflexive…
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.
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.
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.
The non-uniformity of fossil preservation.
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
The non-uniformity of fossil preservation.
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'.
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.
Non-uniform lateral current distribution in quantum cascade lasers.
Huang, Xue; Dikmelik, Yamac; Gmachl, Claire
2014-03-10
Non-uniform lateral current distribution in quantum cascade (QC) lasers is investigated, as a result of stimulated-optical-emission-assisted electron transport, the rate of which depends on the local photon density and is comparable to the longitudinal optical (LO) phonon scattering rate. A microscopic model based on rate equations is built to study the self-consistent process of interaction between local electrons and photons in QC lasers. The non-uniform distribution of lateral current and the corresponding spatial hole burning are simulated from this model. Moreover, multi-transverse-mode operation in QC lasers is also investigated.
Effect of non-uniform exchange field in ferromagnetic graphene
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.
Detector non-uniformity in scanning transmission electron microscopy.
Findlay, S D; LeBeau, J M
2013-01-01
A non-uniform response across scanning transmission electron microscope annular detectors has been found experimentally, but is seldom incorporated into simulations. Through case study simulations, we establish the nature and scale of the discrepancies which may arise from failing to account for detector non-uniformity. If standard detectors are used at long camera lengths such that the detector is within or near to the bright field region, we find errors in contrast of the order of 10%, sufficiently small for qualitative work but non-trivial as experiments become more quantitative. In cases where the detector has been characterized in advance, we discuss the detector response normalization and how it may be incorporated in simulations.
Equilibrium states for random non-uniformly expanding maps
NASA Astrophysics Data System (ADS)
Arbieto, Alexander; Matheus, Carlos; Oliveira, Krerley
2004-03-01
We show that for a robust (C2-open) class of random non-uniformly expanding maps there exist equilibrium states for a large class of potentials. In particular, these sytems have measures of maximal entropy. These results also give a partial answer to a question posed by Liu-Zhao. The proof of the main result uses an extension of techniques in recent works by Alves-Araújo, Alves-Bonatti-Viana and Oliveira.
Direct analytical solutions to non-uniform beam problems
NASA Technical Reports Server (NTRS)
Bailey, C. D.
1978-01-01
The direct analytical solution to the vibration of non-uniform beams with and without discontinuities and with various boundary conditions is presented. Results are compared to results from the exact solution for certain cases where the exact solution has been obtained. It is shown that the direct solution converges to the exact solution, in fact, with 'indefinite accuracy' just as Hamilton stated that it would.
Detection of lateral non-uniformities in fluidized bed combustors
Ramayya, A.V.; Thiyagarajan, A.; Ahmed, S.A.
1997-12-01
This paper addresses the detection of lateral non-Uniformities in fluidized bed combustors by a novel probe technique not reported so far, by using the horizontal differential pressure fluctuations associated with bubble flow. The salient features of these fluctuations are highlighted utilizing the simulated records obtained by considering the Davidson`s pressure field around a bubble. The simulation approach is validated by a comparison with the measured vertical and horizontal differential fluctuations in a freely bubbling fluidized bed.
Leveraging limited research and development (R&D) resources in the public sector
Senglaub, M.
1995-08-01
Mission-directed public-sector research facilities are experiencing increasingly severe budget environments while seeing expanding missions and responsibilities. In an effort to identify research leveraging methodologies an information search was conducted in conjunction with some efforts to find the proper links to systems engineering fundamentals. The result is an initial model for use in a preconcept/phase-1 engineering design organization, with a goal of improving the organizations performance.
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.
Naturalness preserved enhancement algorithm for non-uniform illumination images.
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
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.
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.
Compensation for Non-Uniformity in a Meshed Electrical Network
NASA Astrophysics Data System (ADS)
Survilo, J.
2009-01-01
Non-uniform electrical networks (meshed included), providing more reliable supply of electric energy to consumers, have greater losses than uniform ones. To upgrade such a network by reducing losses, special measures are provided, which should be done at the least cost. An effective measure of the kind would be introduction of opposing voltage or complementary reactances in some branches of the network. In this case, to determine the required parameters, a non-uniform meshed network should be disintegrated into separate cells - closed loops with equivalent node loads, which are the sum of node loads and the flows not belonging to a given cell. Then the circulating power of all cells is calculated, and the cell with the maximum circulating power is selected to be upgraded. For this purpose, in this cell the pre-defined opposing voltage or complementary reactance is brought. If the total power loss in the network after the first step of upgrading is not satisfactory, a next similar step should be taken, and a next cell singled out for upgrading. Such cell upgrading should be continued until the total losses stop decreasing.
Leveraging biospecimen resources for discovery or validation of markers for early cancer detection.
Schully, Sheri D; Carrick, Danielle M; Mechanic, Leah E; Srivastava, Sudhir; Anderson, Garnet L; Baron, John A; Berg, Christine D; Cullen, Jennifer; Diamandis, Eleftherios P; Doria-Rose, V Paul; Goddard, Katrina A B; Hankinson, Susan E; Kushi, Lawrence H; Larson, Eric B; McShane, Lisa M; Schilsky, Richard L; Shak, Steven; Skates, Steven J; Urban, Nicole; Kramer, Barnett S; Khoury, Muin J; Ransohoff, David F
2015-04-01
Validation of early detection cancer biomarkers has proven to be disappointing when initial promising claims have often not been reproducible in diagnostic samples or did not extend to prediagnostic samples. The previously reported lack of rigorous internal validity (systematic differences between compared groups) and external validity (lack of generalizability beyond compared groups) may be effectively addressed by utilizing blood specimens and data collected within well-conducted cohort studies. Cohort studies with prediagnostic specimens (eg, blood specimens collected prior to development of clinical symptoms) and clinical data have recently been used to assess the validity of some early detection biomarkers. With this background, the Division of Cancer Control and Population Sciences (DCCPS) and the Division of Cancer Prevention (DCP) of the National Cancer Institute (NCI) held a joint workshop in August 2013. The goal was to advance early detection cancer research by considering how the infrastructure of cohort studies that already exist or are being developed might be leveraged to include appropriate blood specimens, including prediagnostic specimens, ideally collected at periodic intervals, along with clinical data about symptom status and cancer diagnosis. Three overarching recommendations emerged from the discussions: 1) facilitate sharing of existing specimens and data, 2) encourage collaboration among scientists developing biomarkers and those conducting observational cohort studies or managing healthcare systems with cohorts followed over time, and 3) conduct pilot projects that identify and address key logistic and feasibility issues regarding how appropriate specimens and clinical data might be collected at reasonable effort and cost within existing or future cohorts. PMID:25688116
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.
Coupled Serial and Parallel Non-uniform SQUIDs
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.
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.
Effective electrodiffusion equation for non-uniform nanochannels
NASA Astrophysics Data System (ADS)
Marconi, Umberto Marini Bettolo; Melchionna, Simone; Pagonabarraga, Ignacio
2013-06-01
We derive a one-dimensional formulation of the Planck-Nernst-Poisson equation to describe the dynamics of a symmetric binary electrolyte in channels whose section is nanometric and varies along the axial direction. The approach is in the spirit of the Fick-Jacobs diffusion equation and leads to a system of coupled equations for the partial densities which depends on the charge sitting at the walls in a non-trivial fashion. We consider two kinds of non-uniformities, those due to the spatial variation of charge distribution and those due to the shape variation of the pore and report one- and three-dimensional solutions of the electrokinetic equations.
Passive nanofluidic diode using non-uniform nanochannels
NASA Astrophysics Data System (ADS)
Mo, Jingwen; Li, Chu; Li, Long; Wang, Jun; Li, Zhigang
2016-08-01
In this work, we propose a nanofluidic diode for simple fluids using non-uniform nanochannels. Molecular dynamics simulations show that the fluidic diode allows water flows in the forward direction and blocks flows in the backward direction in a wide range of pressure drops. The unidirectional water flows are owing to the distinct activation pressures in different directions. In the forward (converging) direction, the activation pressure is small because of the relatively low capillary pressure and the water coalescence at the exit. In the backward direction, the activation pressure is high due to the high infiltration pressure. The pressure drop range for the fluidic diode can be varied by modifying the surface wettability, channel height, and/or the tilt angle of the channel. The fluidic diode can be used for flow control in integrated micro- and nanofluidic devices.
Effect on Non-Uniform Heat Generation on Thermionic Reactions
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.
Compensation for non-uniform attenuation in SPECT brain imaging
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%.
Gridding and fast Fourier transformation on non-uniformly sparse sampled multidimensional NMR data.
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
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.
STUDY OF NON-UNIFORMITY COEFFICIENT CONSIDERING MICROTOPOGRAPHY FOR SEISMIC DESIGN OF WATER PIPELINE
NASA Astrophysics Data System (ADS)
Shichiroumaru, Kazutaka; Miyajima, Masakatsu
This study is focusing on a non-uniformity coefficient of ground in the earthquake-resistant of a water pipeline. A lot of earthquake damage occurs at high non-uniformity ground. Therefore it is necessary to consider non-uniformity at the earthquake-resistant of the underground pipeline. By using a microtopography classification, non-uniformity coefficient in the boundary in the microtopography is studied. As a result, earthquake damage rate of underground pipeline at the boundary of the microtopography tends to be high. Therefore, the non-uniformity at the boundary can be obtained from a kind of microtopography and the boundary condition.
Preservation of network degree distributions from non-uniform failures
NASA Astrophysics Data System (ADS)
Karrer, B.; Ghoshal, G.
2008-03-01
There has been a considerable amount of interest in recent years on the robustness of networks to failures. Many previous studies have concentrated on the effects of node and edge removals on the connectivity structure of a static network; the networks are considered to be static in the sense that no compensatory measures are allowed for recovery of the original structure. Real world networks such as the world wide web, however, are not static and experience a considerable amount of turnover, where nodes and edges are both added and deleted. Considering degree-based node removals, we examine the possibility of preserving networks from these types of disruptions. We recover the original degree distribution by allowing the network to react to the attack by introducing new nodes and attaching their edges via specially tailored schemes. We focus particularly on the case of non-uniform failures, a subject that has received little attention in the context of evolving networks. Using a combination of analytical techniques and numerical simulations, we demonstrate how to preserve the exact degree distribution of the studied networks from various forms of attack.
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.
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.
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.
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.
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.
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.
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".
Leveraging human decision making through the optimal management of centralized resources
NASA Astrophysics Data System (ADS)
Hyden, Paul; McGrath, Richard G.
2016-05-01
Combining results from mixed integer optimization, stochastic modeling and queuing theory, we will advance the interdisciplinary problem of efficiently and effectively allocating centrally managed resources. Academia currently fails to address this, as the esoteric demands of each of these large research areas limits work across traditional boundaries. The commercial space does not currently address these challenges due to the absence of a profit metric. By constructing algorithms that explicitly use inputs across boundaries, we are able to incorporate the advantages of using human decision makers. Key improvements in the underlying algorithms are made possible by aligning decision maker goals with the feedback loops introduced between the core optimization step and the modeling of the overall stochastic process of supply and demand. A key observation is that human decision-makers must be explicitly included in the analysis for these approaches to be ultimately successful. Transformative access gives warfighters and mission owners greater understanding of global needs and allows for relationships to guide optimal resource allocation decisions. Mastery of demand processes and optimization bottlenecks reveals long term maximum marginal utility gaps in capabilities.
Green, Rebekah
2014-01-01
Universities and colleges provide students with an opportunity to grow personally and professionally through a structured series of learning experiences. Yet disasters can interrupt traditional place-based education and prove to be intractable policy problems. The challenges of developing robust plans and drilling them extensively are most pronounced among smaller public colleges and universities. This article describes how three small- to moderate-sized higher education institutions formed a consortium to better prepare for emergencies, despite limited resources. Together the institutions built common templates, hired joint staff, and created a suit of joint exercises appropriate for their small size and campus-specific needs. In the process, they shared unique perspectives that improved resilience across the institutions.
Liquid jets injected into non-uniform crossflow
NASA Astrophysics Data System (ADS)
Tambe, Samir
An experimental study has been conducted with liquid jets injected transversely into a crossflow to study the effect of non-uniformities in the crossflow velocity distribution to the jet behavior. Two different non-uniform crossflows were created during this work, a shear-laden crossflow and a swirling crossflow. The shear-laden crossflow was generated by merging two independent, co-directional, parallel airstreams creating a shear mixing layer at the interface between them. The crossflow exhibited a quasi-linear velocity gradient across the height of the test chamber. By varying the velocities of the two airstreams, the sense and the slope of the crossflow velocity gradient could be changed. Particle Image Velocimetry (PIV) studies were conducted to characterize the crossflow. The parameter, UR, is defined as the ratio of the velocities of the two streams and governs the velocity gradient. A positive velocity gradient was observed for UR > 1 and a negative velocity gradient for UR < 1. PIV and Phase Doppler Particle Anemometry (PDPA) studies were conducted to study the penetration and atomization of 0.5 mm diameter water jets injected into this crossflow. The crossflow velocity gradient was observed to have a significant effect on jet penetration as well as the post breakup spray. For high UR (> 1), jet penetration increased and the Sauter Mean Diameter (SMD) distribution became more uniform. For low UR (< 1), low penetration, higher droplet velocities and better atomization were observed. The second crossflow tested was a swirling flow generated using in-house designed axial swirlers. Three swirlers were used, with vane exit angles of 30°, 45° and 60°. Laser Doppler Velocimetry (LDV) was used to study the crossflow velocities. The axial (Ux) and the tangential (Utheta) components of the crossflow velocity were observed to decrease with increasing radial distance away from the centerbody. The flow angle of the crossflow was smaller than the vane exit angle
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
Mu, John C; Tootoonchi Afshar, Pegah; Mohiyuddin, Marghoob; Chen, Xi; Li, Jian; Bani Asadi, Narges; Gerstein, Mark B; Wong, Wing H; Lam, Hugo Y K
2015-09-28
A high-confidence, comprehensive human variant set is critical in assessing accuracy of sequencing algorithms, which are crucial in precision medicine based on high-throughput sequencing. Although recent works have attempted to provide such a resource, they still do not encompass all major types of variants including structural variants (SVs). Thus, we leveraged the massive high-quality Sanger sequences from the HuRef genome to construct by far the most comprehensive gold set of a single individual, which was cross validated with deep Illumina sequencing, population datasets, and well-established algorithms. It was a necessary effort to completely reanalyze the HuRef genome as its previously published variants were mostly reported five years ago, suffering from compatibility, organization, and accuracy issues that prevent their direct use in benchmarking. Our extensive analysis and validation resulted in a gold set with high specificity and sensitivity. In contrast to the current gold sets of the NA12878 or HS1011 genomes, our gold set is the first that includes small variants, deletion SVs and insertion SVs up to a hundred thousand base-pairs. We demonstrate the utility of our HuRef gold set to benchmark several published SV detection tools.
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.
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.
Non-uniformity correction of infrared focal plane array in point target surveillance systems
NASA Astrophysics Data System (ADS)
Hu, Jing; Xu, Zhenzhen; Wan, Qinqin
2014-09-01
We discuss the influence of non-uniformity and non-uniformity correction on point target detection in infrared surveillance system, and propose a non-uniformity correction approach which is based on signal intensity and sensor characteristics. Theoretical models are used to derive the combined effect of background clutter, sensor random noise, target, non-uniformity and correction error on the signal-to-noise-and-clutter ratio. From our analysis, it can be noted that background clutter intensity is successively modulated by sensor non-uniformity and non-uniformity correction, while sensor random noise is modulated by the non-uniformity correction process only. Furthermore, background clutter and sensor random noise are the key factors that affect the performance of a surveillance system, when it is used to detect point targets. The method presented in this paper takes all of the above into account, moreover, it considers the difference between scanning and staring focal plane array. The experimental results demonstrate the effectiveness of the proposed method.
An enhanced non-uniformity correction algorithm for IRFPA based on neural network
NASA Astrophysics Data System (ADS)
Wang, BingJian; Liu, ShangQian; Bai, LiPing
2008-04-01
Influenced by detector materials' non-uniformity, growth and etching techniques, etc., every detector's responsivity of infrared focal plane arrays (IRFPA) is different, which results in non-uniformity of IRFPA. And non-uniformity of IRFPA generates fixed pattern noises (FPN) that are superposed on infrared image. And it may degrade the infrared image quality, which greatly limits the application of IRFPA. Non-uniformity correction (NUC) is an important technique for IRFPA. The traditional non-uniformity correction algorithm based on neural network and its modified algorithms are analyzed in this paper. And a new improved non-uniformity correction algorithm based on neural network is proposed in this paper. In this algorithm, the desired image is estimated by using three successive images in an infrared sequence. And blurring effect caused by motion is avoided by applying implicit motion detection and edge detection. So the estimation image is closer to real image than the estimation image estimated by other algorithms, which results in fast convergence speed of correction parameters. A comparison is made to these algorithms in this paper. And experimental results show that the algorithm proposed in this paper can correct the non-uniformity of IRFPA effectively and it prevails over other algorithms based on neural network.
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.
NASA Astrophysics Data System (ADS)
Vovk, Uros; Pernus, Franjo; Likar, Bostjan
2003-05-01
In MRI, image intensity non-uniformity is an adverse phenomenon that increases inter-tissue overlapping. The aim of this study was to provide a novel general framework, named regularized feature condensing (RFC), for condensing the distribution of image features and apply it to correct intensity non-uniformity via spatial regularization. The proposed RCF method is an iterative procedure, which consists of four basic steps. First, creation of a feature space, which consists of multi-spectral image intensities and corresponding second derivatives. Second, estimation of the intensity condensing map in feature space, i.e. the estimation of the increase of feature probability densities by a well-established mean shift procedure. Third, regularization of intensity condensing map in image space, which yields the estimation of intensity non-uniformity. Fourth, applying the estimation of non-uniformity correction to the input image. In this way, the intensity distributions of distinct tissues are gradually condensed via spatial regularization. The method was tested on simulated and real MR brain images for which gold standard segmentations were available. The results showed that the method did not induce additional intensity variations in simulated uniform images and efficiently removed intensity non-uniformity in real MR brain images. The proposed RCF method is a powerful fully automated intensity non-uniformity correction method that makes no a prior assumptions on the image intensity distribution and provides non-parametric non-uniformity correction.
NASA Astrophysics Data System (ADS)
Yan, Wanfeng; Woodard, Ryan; Sornette, Didier
2012-01-01
Leverage is strongly related to liquidity in a market and lack of liquidity is considered a cause and/or consequence of the recent financial crisis. A repurchase agreement is a financial instrument where a security is sold simultaneously with an agreement to buy it back at a later date. Repurchase agreement (repo) market size is a very important element in calculating the overall leverage in a financial market. Therefore, studying the behavior of repo market size can help to understand a process that can contribute to the birth of a financial crisis. We hypothesize that herding behavior among large investors led to massive over-leveraging through the use of repos, resulting in a bubble (built up over the previous years) and subsequent crash in this market in early 2008. We use the Johansen-Ledoit-Sornette (JLS) model of rational expectation bubbles and behavioral finance to study the dynamics of the repo market that led to the crash. The JLS model qualifies a bubble by the presence of characteristic patterns in the price dynamics, called log-periodic power law (LPPL) behavior. We show that there was significant LPPL behavior in the market before that crash and that the predicted range of times predicted by the model for the end of the bubble is consistent with the observations.
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.
Non-uniformity correction for division of focal plane polarimeters with a calibration method.
Zhang, Junchao; Luo, Haibo; Hui, Bin; Chang, Zheng
2016-09-10
Division of focal plane polarimeters are composed of nanometer polarization elements overlaid upon a focal plane array (FPA) sensor. The manufacturing flaws of the polarization grating and each detector in the FPA having a different photo response can introduce non-uniformity errors when reconstructing the polarization image without correction. A new calibration method is proposed to mitigate non-uniformity errors in the visible waveband. We correct non-uniformity in the form of a vector. The correction matrix and offset vector are calculated for the following correction. The performance of the proposed method is compared with state-of-the-art techniques by employing simulated data and real scenes. The experimental results showed that the proposed method can effectively mitigate non-uniformity errors and achieve better visual results. PMID:27661358
Locally adaptive regression filter-based infrared focal plane array non-uniformity correction
NASA Astrophysics Data System (ADS)
Li, Jia; Qin, Hanlin; Yan, Xiang; Huang, He; Zhao, Yingjuan; Zhou, Huixin
2015-10-01
Due to the limitations of the manufacturing technology, the response rates to the same infrared radiation intensity in each infrared detector unit are not identical. As a result, the non-uniformity of infrared focal plane array, also known as fixed pattern noise (FPN), is generated. To solve this problem, correcting the non-uniformity in infrared image is a promising approach, and many non-uniformity correction (NUC) methods have been proposed. However, they have some defects such as slow convergence, ghosting and scene degradation. To overcome these defects, a novel non-uniformity correction method based on locally adaptive regression filter is proposed. First, locally adaptive regression method is used to separate the infrared image into base layer containing main scene information and the detail layer containing detailed scene with FPN. Then, the detail layer sequence is filtered by non-linear temporal filter to obtain the non-uniformity. Finally, the high quality infrared image is obtained by subtracting non-uniformity component from original image. The experimental results show that the proposed method can significantly eliminate the ghosting and the scene degradation. The results of correction are superior to the THPF-NUC and NN-NUC in the aspects of subjective visual and objective evaluation index.
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.
Dorsey, Susan G; Schiffman, Rachel; Redeker, Nancy S; Heitkemper, Margaret; McCloskey, Donna Jo; Weglicki, Linda S; Grady, Patricia A
2014-01-01
The National Institute of Nursing Research (NINR) Centers of Excellence program is a catalyst enabling institutions to develop infrastructure and administrative support for creating cross-disciplinary teams that bring multiple strategies and expertise to bear on common areas of science. Centers are increasingly collaborative with campus partners and reflect an integrated team approach to advance science and promote the development of scientists in these areas. The purpose of this paper is to present the NINR Logic Model for Center Sustainability. The components of the logic model were derived from the presentations and robust discussions at the 2013 NINR center directors' meeting focused on best practices for leveraging resources and collaboration as methods to promote center sustainability. Collaboration through development and implementation of cross-disciplinary research teams is critical to accelerate the generation of new knowledge for solving fundamental health problems. Sustainability of centers as a long-term outcome beyond the initial funding can be enhanced by thoughtful planning of inputs, activities, and leveraging resources across multiple levels.
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.
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.
On natural frequencies of non-uniform beams modulated by finite periodic cells
NASA Astrophysics Data System (ADS)
Xu, Yanlong; Zhou, Xiaoling; Wang, Wei; Wang, Longqi; Peng, Fujun; Li, Bin
2016-09-01
It is well known that an infinite periodic beam can support flexural wave band gaps. However, in real applications, the number of the periodic cells is always limited. If a uniform beam is replaced by a non-uniform beam with finite periodicity, the vibration changes are vital by mysterious. This paper employs the transfer matrix method (TMM) to study the natural frequencies of the non-uniform beams with modulation by finite periodic cells. The effects of the amounts, cross section ratios, and arrangement forms of the periodic cells on the natural frequencies are explored. The relationship between the natural frequencies of the non-uniform beams with finite periodicity and the band gap boundaries of the corresponding infinite periodic beam is also investigated. Numerical results and conclusions obtained here are favorable for designing beams with good vibration control ability.
NASA Astrophysics Data System (ADS)
Li, Hong; Zhang, Wei; Zhang, Zhenguo; Chen, Xiaofei
2015-07-01
A discontinuous grid finite-difference (FD) method with non-uniform time step Runge-Kutta scheme on curvilinear collocated-grid is developed for seismic wave simulation. We introduce two transition zones: a spatial transition zone and a temporal transition zone, to exchange wavefield across the spatial and temporal discontinuous interfaces. A Gaussian filter is applied to suppress artificial numerical noise caused by down-sampling the wavefield from the finer grid to the coarser grid. We adapt the non-uniform time step Runge-Kutta scheme to a discontinuous grid FD method for further increasing the computational efficiency without losing the accuracy of time marching through the whole simulation region. When the topography is included in the modelling, we carry out the discontinuous grid method on a curvilinear collocated-grid to obtain a sufficiently accurate free-surface boundary condition implementation. Numerical tests show that the proposed method can sufficiently accurately simulate the seismic wave propagation on such grids and significantly reduce the computational resources consumption with respect to regular grids.
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.
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.
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.
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.
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.
Face recognition across non-uniform motion blur, illumination, and pose.
Punnappurath, Abhijith; Rajagopalan, Ambasamudram Narayanan; Taheri, Sima; Chellappa, Rama; Seetharaman, Guna
2015-07-01
Existing methods for performing face recognition in the presence of blur are based on the convolution model and cannot handle non-uniform blurring situations that frequently arise from tilts and rotations in hand-held cameras. In this paper, we propose a methodology for face recognition in the presence of space-varying motion blur comprising of arbitrarily-shaped kernels. We model the blurred face as a convex combination of geometrically transformed instances of the focused gallery face, and show that the set of all images obtained by non-uniformly blurring a given image forms a convex set. We first propose a non-uniform blur-robust algorithm by making use of the assumption of a sparse camera trajectory in the camera motion space to build an energy function with l1 -norm constraint on the camera motion. The framework is then extended to handle illumination variations by exploiting the fact that the set of all images obtained from a face image by non-uniform blurring and changing the illumination forms a bi-convex set. Finally, we propose an elegant extension to also account for variations in pose. PMID:25775493
SoPC implementation of combined real-time non-uniformity correction of IRFPA
NASA Astrophysics Data System (ADS)
Gao, Kun; Nie, Zhao-jun; Yang, Hu; Ni, Guoqiang
2009-11-01
With the increase of pixel density and scale of IRFPA (Infrared Focal Plane Array), NUC (Non-Uniformity Correction) technology becomes more and more important to access high quality infrared images. However, traditional one-point or two-point NUC methods based on calibration technology can't achieve ideal performance because they can't overcome the non-linearity and drift of the detector response parameters in both spatial and temporal regions effectively. A novel combined real-time non-uniformity correction method is proposed based on FPGA (Field Programmable Gate Array) technology, which adopts SoPC (System-on-a-Programmable Chip) architecture based on Nios II processor core to implement the total NUC processing functions inside only one chip. The NUC processing chooses the reference-based binomial fitting algorithm to remove the main non-uniformity of the detector, and the remained non-uniformity is compensated by using the improved scene-based temporal high-pass filter algorithm. The experiment results show that the combined method based on SoPC architecture can access the ideal efforts with IRFPA size of 320×240×14bit @ 25 frames per second. The block diagram of hardware circuit and the processing flow are described in details.
Free vibration of non-uniform nanobeams using Rayleigh-Ritz method
NASA Astrophysics Data System (ADS)
Chakraverty, S.; Behera, Laxmi
2015-03-01
In this article, boundary characteristic orthogonal polynomials have been implemented in the Rayleigh-Ritz method to investigate free vibration of non-uniform Euler-Bernoulli nanobeams based on nonlocal elasticity theory. Non-uniform cross section of nanobeams has been considered by taking linear as well as quadratic variations of Young's modulus and density along the space coordinate. Detailed analysis has been reported for all the possible cases of such variations. The objective of the present study is to analyze the effects of nonlocal parameter, boundary condition, length-to-diameter ratio and non-uniform parameter on the frequency parameters. It is found that clamped nanobeams are having highest frequency parameters than other types of boundary conditions for a particular set of parameters. It is also observed that frequency parameters decrease with increase in scaling effect parameter. First four deflection shapes of non-uniform nanobeams have also been incorporated. In this analysis, some of the new results in terms of boundary conditions have also been included.
Differential orientation of 10T1/2 mesenchymal cells on non-uniform stretch environments.
Richardson, W J; van der Voort, D D; Wilson, E; Moore, J E
2013-09-01
Non-uniform stress and strain fields are prevalent in many tissues in vivo, and often exacerbated by disease or injury. These mechanical gradients potentially play a role in contributing to pathological conditions, presenting a need for experimental tools to allow investigation of cell behavior within non-uniformly stimulated environments. Herein, we employ two in vitro cell-stretching devices (one previously published; one newly presented) capable of subjecting cells to cyclic, non-uniform stretches upon the surface of either a circular elastomeric membrane or a cylindrical PDMS tube. After 24 hours of cyclic stretch, 10T1/2 cells on both devices showed marked changes in long-axis orientation, with tendencies to align parallel to the direction of minimal deformation. The degree of this response varied depending on location within the stretch gradients. These results demonstrated the feasibility of conducting cell mechanobiology investigations with the two novel devices, while also highlighting the experimental capabilities of non-uniform mechanical environments for these types of studies. Such capabilities include robust data collection for developing mechanobiological dose-response curves, signal threshold identification, and potential spatial targeting for drug delivery. PMID:24396979
Co-evolving non-uniform cellular automata to perform computations
NASA Astrophysics Data System (ADS)
Sipper, Moshe
A major impediment of cellular automata (CA) stems from the difficulty of utilizing their complex behavior to perform useful computations. Recent studies by Packard and Mitchell et al. have shown that CAs can be evolved to perform a computational task. In this paper non-uniform CAs are studied, where each cell may contain a different rule, in contrast to the original, uniform model. We describe experiments in which non-uniform CAs are evolved to perform the computational task using a local, co-evolutionary algorithm. For radius r = 3 we attain peak performance values of 0.92 comparable to those obtained for uniform CAs (0.93-0.95). This is notable considering the huge search spaces involved, much larger than the uniform case. Smaller radius CAs (previously unstudied in this context) attain performance values of 0.93-0.94. For r = 1 this is considerably higher than the maximal possible uniform CA performance of 0.83, suggesting that non-uniformity reduces connectivity requirements. We thus demonstrate that: (1) non-uniform CAs can attain high computational performance, and (2) such systems can be evolved rather than designed.
A DSP-based neural network non-uniformity correction algorithm for IRFPA
NASA Astrophysics Data System (ADS)
Liu, Chong-liang; Jin, Wei-qi; Cao, Yang; Liu, Xiu
2009-07-01
An effective neural network non-uniformity correction (NUC) algorithm based on DSP is proposed in this paper. The non-uniform response in infrared focal plane array (IRFPA) detectors produces corrupted images with a fixed-pattern noise(FPN).We introduced and analyzed the artificial neural network scene-based non-uniformity correction (SBNUC) algorithm. A design of DSP-based NUC development platform for IRFPA is described. The DSP hardware platform designed is of low power consumption, with 32-bit fixed point DSP TMS320DM643 as the kernel processor. The dependability and expansibility of the software have been improved by DSP/BIOS real-time operating system and Reference Framework 5. In order to realize real-time performance, the calibration parameters update is set at a lower task priority then video input and output in DSP/BIOS. In this way, calibration parameters updating will not affect video streams. The work flow of the system and the strategy of real-time realization are introduced. Experiments on real infrared imaging sequences demonstrate that this algorithm requires only a few frames to obtain high quality corrections. It is computationally efficient and suitable for all kinds of non-uniformity.
10 CFR 835.205 - Determination of compliance for non-uniform exposure of the skin.
Code of Federal Regulations, 2014 CFR
2014-01-01
... the skin. 835.205 Section 835.205 Energy DEPARTMENT OF ENERGY OCCUPATIONAL RADIATION PROTECTION... of the skin. (a) Non-uniform exposures of the skin from X-rays, beta radiation, and/or radioactive material on the skin are to be assessed as specified in this section. (b) For purposes of...
10 CFR 835.205 - Determination of compliance for non-uniform exposure of the skin.
Code of Federal Regulations, 2010 CFR
2010-01-01
... the skin. 835.205 Section 835.205 Energy DEPARTMENT OF ENERGY OCCUPATIONAL RADIATION PROTECTION... of the skin. (a) Non-uniform exposures of the skin from X-rays, beta radiation, and/or radioactive material on the skin are to be assessed as specified in this section. (b) For purposes of...
10 CFR 835.205 - Determination of compliance for non-uniform exposure of the skin.
Code of Federal Regulations, 2013 CFR
2013-01-01
... the skin. 835.205 Section 835.205 Energy DEPARTMENT OF ENERGY OCCUPATIONAL RADIATION PROTECTION... of the skin. (a) Non-uniform exposures of the skin from X-rays, beta radiation, and/or radioactive material on the skin are to be assessed as specified in this section. (b) For purposes of...
10 CFR 835.205 - Determination of compliance for non-uniform exposure of the skin.
Code of Federal Regulations, 2012 CFR
2012-01-01
... the skin. 835.205 Section 835.205 Energy DEPARTMENT OF ENERGY OCCUPATIONAL RADIATION PROTECTION... of the skin. (a) Non-uniform exposures of the skin from X-rays, beta radiation, and/or radioactive material on the skin are to be assessed as specified in this section. (b) For purposes of...
10 CFR 835.205 - Determination of compliance for non-uniform exposure of the skin.
Code of Federal Regulations, 2011 CFR
2011-01-01
... the skin. 835.205 Section 835.205 Energy DEPARTMENT OF ENERGY OCCUPATIONAL RADIATION PROTECTION... of the skin. (a) Non-uniform exposures of the skin from X-rays, beta radiation, and/or radioactive material on the skin are to be assessed as specified in this section. (b) For purposes of...
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.
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
Assessment of heating rate and non-uniform heating in domestic microwave ovens.
Pitchai, Krishnamoorthy; Birla, Sohan L; Jones, David; Subbiah, Jeyamkondan
2012-01-01
Due to the inherent nature of standing wave patterns of microwaves inside a domestic microwave oven cavity and varying dielectric properties of different food components, microwave heating produces non-uniform distribution of energy inside the food. Non-uniform heating is a major food safety concern in not-ready-to-eat (NRTE) microwaveable foods. In this study, we present a method for assessing heating rate and non-uniform heating in domestic microwave ovens. In this study a custom designed container was used to assess heating rate and non-uniform heating of a range of microwave ovens using a hedgehog of 30 T-type thermocouples. The mean and standard deviation of heating rate along the radial distance and sector of the container were measured and analyzed. The effect of the location of rings and sectors was analyzed using ANOVA to identify the best location for placing food on the turntable. The study suggested that the best location to place food in a microwave oven is not at the center but near the edge of the turntable assuming uniform heating is desired. The effect of rated power and cavity size on heating rate and non-uniform heating was also studied for a range of microwave ovens. As the rated power and cavity size increases, heating rate increases while non-uniform heating decreases. Sectors in the container also influenced heating rate (p < 0.0001), even though it did not have clear trend on heating rate. In general, sectors close to the magnetron tend to heat slightly faster than sectors away from the magnetron. However, the variation in heating rate among sectors was only 2 degrees C/min and considered not practically important. Overall heating performance such as mean heating rate and non-uniform heating did not significantly vary between the two replications that were performed 4 h apart. However, microwave ovens were inconsistent in producing the same heating patterns between the two replications that were performed 4 h apart.
Extension of the modal wave-front reconstruction algorithm to non-uniform illumination.
Ma, Xiaoyu; Mu, Jie; Rao, ChangHui; Yang, Jinsheng; Rao, XueJun; Tian, Yu
2014-06-30
Attempts are made to eliminate the effects of non-uniform illumination on the precision of wave-front measurement. To achieve this, the relationship between the wave-front slope at a single sub-aperture and the distributions of the phase and light intensity of the wave-front were first analyzed to obtain the relevant theoretical formulae. Then, based on the principle of modal wave-front reconstruction, the influence of the light intensity distribution on the wave-front slope is introduced into the calculation of the reconstruction matrix. Experiments were conducted to prove that the corrected modal wave-front reconstruction algorithm improved the accuracy of wave-front reconstruction. Moreover, the correction is conducive to high-precision wave-front measurement using a Hartmann wave-front sensor in the presence of non-uniform illumination.
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.
Energy-Efficient Algorithm for Sensor Networks with Non-Uniform Maximum Transmission Range
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
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
Node Non-Uniform Deployment Based on Clustering Algorithm for Underwater Sensor Networks.
Jiang, Peng; Liu, Jun; Wu, Feng
2015-12-01
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.
Non-Uniform Dose Mapping Controlled by Modulated Vertical and Horizontal Scans
Ninomiya, S.; Kimura, Y.; Kudo, T.; Ochi, A.; Toda, R.; Tsukihara, M.; Sato, F.; Fuse, G.; Ueno, K.; Sugitani, M.
2008-11-03
Since geometries of semi-conductor devices continue to shrink, the requirement for each process becomes severer to keep uniformity of electrical parameters of the semi-conductor devices. A larger wafer also causes larger variations. Thus it has been strongly required for ion implantation process to compensate for the variations from other processes because of its good dose controllability. A newly developed mapping of intentional non-uniform dosage system, which is named 'MIND system', is implemented in SEN's single-wafer-type implanters. The MIND system controls both horizontal and vertical scan speed simultaneously. Intentional two-dimensional non-uniform profiles of sheet resistance, such as concentric and eccentric profiles, are obtained only by single-step ion implantation.
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.
Node Non-Uniform Deployment Based on Clustering Algorithm for Underwater Sensor Networks.
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
Node Non-Uniform Deployment Based on Clustering Algorithm for Underwater Sensor Networks
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
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.
The development of non-uniform deposition of holes in gate oxides
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.
Asymptotic Governing Equation for Wave Propagation Along Weakly Non-Uniform EULER-BERNOULLI Beams
NASA Astrophysics Data System (ADS)
BURR, K. P.; TRIANTAFYLLOU, M. S.; YUE, D. K. P.
2001-11-01
Non-uniformity in beams arises either from manufacturing imperfections or by design, and can have a singular impact on the qualitative properties of the vibratory response of the beam. To describe the mechanism causing such large changes on the dynamics of the beam, we derived asymptotically a simpler equation, in the formχss+Q (s) χ (s)=0. The coefficient function Q (s) is given by equation (52) herein in terms of the beam flexural rigidity, the mass per unit length and the tensile force applied to the beam. The equation is asymptotic to the non-uniformity of the beam, but under certain restrictions, namely of having constant tension and a constant product of the beam mass per unit length and flexural rigidity, it is an exact governing equation for wave propagation along Bernoulli-Euler beams and it has a Helmholtz-like form. The behavior of the equation is systematically explored and illustrated through numerical results.
Extension of the non-uniform warping theory to an orthotropic composite beam
NASA Astrophysics Data System (ADS)
Ghazouani, Nejib; El Fatmi, Rached
2010-12-01
This Note proposes an extension to composite section of the non-uniform (out-of-plane) warping beam theory recently established for homogeneous and isotropic beam by R. El Fatmi (C. R. Mecanique 335 (2007) 467-474). For the present work, which constitutes a first step of this extension, the cross-section is assumed to be symmetric and made by orthotropic materials; however, Poisson's effects (called here in-plane warping) are also taken into account. Closed form results are given for the structural behavior of the composite beam and for the expressions of the 3D stresses; these ones, easy to compare with 3D Saint Venant stresses, make clear the additional contribution of the new internal forces induced by the non-uniformity of the (in and out) warpings. As first numerical applications, results on torsion and shear-bending of a cantilever sandwich beam are presented.
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.
Dr. Louis Nadelson; Anne Louise Seifert; Meagan McKinney
2014-06-01
Business, industry, parks, nature settings, government infrastructure, and people, can be invaluable resources for connecting STEM curriculum within context which results in conditions ideal for promoting purposeful learning of authentic STEM content. Thus, community-based STEM resources offer ideal context for teaching STEM content. A benefit of focusing teacher attention on these contextual, content aligned resources is that they are in every community; making place-based STEM education a possibility, regardless of the location of STEM teaching and learning. Further, associating STEM teaching and learning with local resources addresses workforce development and the STEM pipeline by exposing students to STEM careers and applications in their local communities. The desire to align STEM teaching and learning with local STEM related resources guided the design of our week-long integrated STEM K-12 teacher professional development (PD) program, i-STEM. We have completed four years of our i-STEM PD program and have made place-based STEM a major emphasis of our curriculum. This report focuses on the data collected in the fourth year of our program. Our week-long i-STEM PD served over 425 educators last summer (2013), providing them with in depth theme-based integrated STEM short courses which were limited to an average of 15 participants and whole group plenary sessions focused around placed based integrated STEM, inquiry, engineering design, standards and practices of Common Core and 21st Century skills. This state wide PD was distributed in five Idaho community colleges and took place over two weeks. The STEM short courses included topics on engineering for sustainability, using engineering to spark interest in STEM, municipal water systems, health, agriculture, food safety, mining, forestry, energy, and others. Integral to these short courses were field trips designed to connect the K-12 educators to the resources in their local communities that could be leveraged
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.
An introduction to the theory of NON-uniformity of hygrothermal constituent of the environment.
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
Non-uniform composite representation of hydroelectric systems for long-term hydrothermal scheduling
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.
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
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.
Upscaling of Solute Transport in Heterogeneous Media with Non-uniform Flow and Dispersion Fields
Xu, Zhijie; Meakin, Paul
2013-10-01
An analytical and computational model for non-reactive solute transport in periodic heterogeneous media with arbitrary non-uniform flow and dispersion fields within the unit cell of length ε is described. The model lumps the effect of non-uniform flow and dispersion into an effective advection velocity Ve and an effective dispersion coefficient De. It is shown that both Ve and De are scale-dependent (dependent on the length scale of the microscopic heterogeneity, ε), dependent on the Péclet number Pe, and on a dimensionless parameter α that represents the effects of microscopic heterogeneity. The parameter α, confined to the range of [-0.5, 0.5] for the numerical example presented, depends on the flow direction and non-uniform flow and dispersion fields. Effective advection velocity Ve and dispersion coefficient De can be derived for any given flow and dispersion fields, and . Homogenized solutions describing the macroscopic variations can be obtained from the effective model. Solutions with sub-unit-cell accuracy can be constructed by homogenized solutions and its spatial derivatives. A numerical implementation of the model compared with direct numerical solutions using a fine grid, demonstrated that the new method was in good agreement with direct solutions, but with significant computational savings.
Non-uniform cosine modulated filter banks using meta-heuristic algorithms in CSD space.
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
Rapid analysis of non-uniformly sampled pulsed field gradient data for velocity estimation.
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
Measurement and analysis of non-uniformities in CdTe solar cells
NASA Astrophysics Data System (ADS)
Sites, James R.
2011-09-01
CdTe and other thin-film polycrystalline solar cells have potential spatial non-uniformities in their photovoltaic response that can both lower their performance and complicate the analysis of their current-voltage curves. Polycrystalline cells have inherent non-uniformities associated with their grain structure, but there are a variety of other possibilities including thickness variations, local shunts, and weak-diode areas. Additionally, there are possible issues associated with the fabrication process due to cleaning residues, scratches, thermal variations, and particulate inclusions. The primary measurements described here to map the non-uniformities of CdTe cells are light-beam-induced current (LBIC), which gives a direct measure of the local PV response, and electroluminescence (EL), which is the inverse of the PV effect. The former is attractive, because it can be used to deduce the local current-voltage curve, but data collection is time consuming. The latter though the use of modern CCD cameras takes only a few seconds and is compatible with production-line screening.
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%.
NASA Astrophysics Data System (ADS)
Krupiński, Michał; Bareła, Jaroslaw; Firmanty, Krzysztof; Kastek, Mariusz
2013-10-01
Uneven response of particular detectors (pixels) to the same incident power of infrared radiation is an inherent feature of microbolometer focal plane arrays. As a result an image degradation occurs, known as Fixed Pattern Noise (FPN), which distorts the thermal representation of an observed scene and impairs the parameters of a thermal camera. In order to compensate such non-uniformity, several NUC correction methods are applied in digital data processing modules implemented in thermal cameras. Coefficients required to perform the non-uniformity correction procedure (NUC coefficients) are determined by calibrating the camera against uniform radiation sources (blackbodies). Non-uniformity correction is performed in a digital processing unit in order to remove FPN pattern in the registered thermal images. Relevant correction coefficients are calculated on the basis of recorded detector responses to several values of radiant flux emitted from reference IR radiation sources (blackbodies). The measurement of correction coefficients requires specialized setup, in which uniform, extended radiation sources with high temperature stability are one of key elements. Measurement stand for NUC correction developed in Institute of Optoelectronics, MUT, comprises two integrated extended blackbodies with the following specifications: area 200×200 mm, stabilized absolute temperature range +15 °C÷100 °C, and uniformity of temperature distribution across entire surface +/-0.014 °C. Test stand, method used for the measurement of NUC coefficients and the results obtained during the measurements conducted on a prototype thermal camera will be presented in the paper.
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.
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.
NASA Astrophysics Data System (ADS)
Wang, Tingting; Yu, Junsheng; Zhou, Yun; Xing, Yanmin; Jiang, Yadong
2010-10-01
Non-uniformity response of detectors based on infrared focal plane array (IRFPA) result in fixed pattern noise (FPN) due to detector materials' non-uniformity and fabrication technology. Once fixed pattern noise added to the infrared image, focal plane image quality will have a serious impact. So non-uniformity correction (NUC) is a key technology in IRFPA application. This paper briefly introduces the traditional neural network algorithm and puts forward an improved algorithm for the neural network algorithm for NUC of infrared focal plane arrays. The main improvement is focused on the estimation method of desired image. The algorithm is used to analyze the image array, correcting data on the array both in space and in time. The correction image in the text is from the infrared data sequence which is more successful of three frames of data obtained. It was found that the estimated image corrected by new algorithm is closer to real image than the estimated image corrected by other algorithm. Moreover, we simulated the new proposed algorithm using Matlab. The results showed that the method of spatial and temporal co-correction of the images is more realistic than the original image.
A Variational Principle For MHD Waves In Non-Uniform Flows
NASA Astrophysics Data System (ADS)
Webb, G. M.; Zank, G. P.; Kagashvili, E. K.; Ratkiewicz, R. E.
2003-12-01
A variational approach for the propagation of linear MHD waves in a non-uniform background flow, such as the solar wind is developed. The analysis is based on the work of Dewar (1970) who used an averaged Lagrangian method to describe the interaction of WKB, MHD waves with a non-uniform background flow. Dewar's variational principle is used to describe non-WKB, MHD waves in a non-uniform background flow,including the effects of gravity and entropy wave disturbances.The equations consist of coupled wave equations for the Lagrangian fluid displacement, ξ , representing the Alfvén and magnetoacoustic waves, and the entropy advection equation for the Lagrangian entropy perturbation Δ S. In the case of steady background flows, with no entropy wave perturbations, the equations reduce to related equations used by Frieman and Rotenberg (1960) to study the stability of steady MHD flows.The characteristics of the equations are obtained by determining the characteristic manifolds on which the Cauchy problem for the waves does not have a unique solution. The characteristics are used to discuss the characteristics and Mach cone for steady MHD flows. A discussion is also given of stress energy tensors for the waves and background flow.
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.
Compact wideband antenna above a wideband non-uniform artificial magnetic conductor
NASA Astrophysics Data System (ADS)
Damaj, Lana; Lepage, Anne-Claire; Begaud, Xavier
2014-08-01
A compact wideband antenna place above a non-uniform artificial magnetic conductor (AMC) is presented. The antenna is composed of a wideband coplanar waveguide fed antenna, with wideband harmonic suppression characteristic using non-uniform defected ground structure. Besides, a non-uniform wideband AMC is designed. The AMC unit cell is composed of a square patch into which a four arms spiral shape is etched. It exhibits a wider ±90° bandwidth than the spiral unit cell and a smaller size than the square patch unit cell. The antenna is placed above the proposed AMC structure formed by 6 × 5 unit cells. The overall dimensions of the complete structure are 0.7 × 0.6 λ {0/2}, where λ 0 is the free-space wavelength at the lowest frequency. It offers a low-profile configuration with a total thickness of λ 0/14.3, and it is matched between 2.5 and 5.4 GHz (73.5 %). Furthermore, it has a stable main lobe radiation pattern in the E- and H-planes within the operating frequency band. Moreover, compared with the antenna without AMC, the broadside realized gain is significantly increased. A prototype has been realized, and there is a good agreement between simulated and measured results. Furthermore, the proposed structure presents a size reduction of about 34 %, and better radiation characteristics in comparison with the conventional square AMC.
NASA Astrophysics Data System (ADS)
Sharma, Pratibha; Walker, Alex; Wheeldon, Jeff; Schriemer, Henry; Hinzer, Karin
2013-10-01
Concentrator photovoltaic (CPV) technology has come a long way, with multi-junction solar cell efficiencies now reaching up to 44.4%. Front contact grid design, crucial for improving efficiency, is typically performed for uniform illumination, but this does not account for the real world conditions of non-homogeneous irradiance distributions. In this work, we aim to optimize finger spacing for a linear grid under non-uniform illumination by using Simulation Program with Integrated Circuit Emphasis (SPICE) analysis. A two-dimensional distributed resistance model is used to simulate a lattice matched, triple-junction solar cell whose design parameters are determined by curve-fitting current-voltage curves from each sub-cell to a two-diode equivalent-circuit model. Cell efficiency is considered to be a unimodal function that varies with finger spacing so a golden-section search optimization algorithm is used to determine the optimal spacing. Various Gaussian profiles are used to simulate non-uniform illumination and their effects on device performance. Designs based on optimal spacing for non-uniform illumination show an efficiency increase of more than 0.5% absolute at concentrations greater than 500 suns.
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.
In vitro response of tumour cells to non-uniform irradiation
NASA Astrophysics Data System (ADS)
Suchowerska, N.; Ebert, M. A.; Zhang, M.; Jackson, M.
2005-07-01
This study examines differences in tumour cellular response using clonogenic cell survival between uniform and non-uniform irradiation. Cells were irradiated with a 6 MV x-ray intensity-modulated beam, in a single large flask (i.e. intercellular communication is possible) or in three small flasks (i.e. intercellular communication is inhibited across the dose gradient). For non-small-cell lung cancer and melanoma cell lines, the dose response over the entire cell culture was significantly different between freely communicating cell cultures and those with inhibited communication across the dose non-uniformity. Communicating cells exhibited poorer survival in the low dose region of the field but improved survival in the high dose region. In general, the response to non-uniform irradiation appeared to 'average out' over the entire cell culture. This was not seen when intercellular communication was inhibited. The results add strength to the body of evidence regarding bystander effects and the inter-dependence of cellular response.
NASA Astrophysics Data System (ADS)
Hoover, J. H.; Brideau, J. M.; Voigt, B. G.; Vorosmarty, C. J.
2010-12-01
The complexity of water resource issues in the Northeast United States is engendered by multiple causal factors and interdependent relationships. Here, we present research that utilized spatial statistics to identify coincident areas of statistically high values (spatial autocorrelation) for biophysical variables such as nutrient loading, population growth, water withdrawals and others in the Northeast United States. The goals of this project were to identify sub-regions in the Northeastern United States that were spatially autocorrelated for multiple variables, and to relate these hotspots to social movements in an historical context. The data employed in this research were point (e.g., wastewater treatment plant location) and county level information for socioeconomic, hydrologic, and water usage variables. We used Local Indicators of Spatial Association, a spatial statistic, to identify county clusters of positive spatial autocorrelation for the region. These clusters were simultaneously overlaid onto a single map to identify areas of positive spatial autocorrelation among multiple variables. Preliminary spatial analysis results suggest that, between 1970 and 2000, positive spatial autocorrelation occurred among nutrient loads, wastewater treatment plant construction, population growth, and dam construction in the Chesapeake Bay area. The New York/New Jersey corridor also showed positive spatial autocorrelation among groundwater withdrawals, thermoelectric power generation, population growth, and wastewater treatment plant construction. Additionally, evaluation of these spatial clusters within their historical context suggests a regional linkage between surface water pollution, environmental regulation, and wastewater treatment plant construction. The results of this project indicate that spatial autocorrelation metrics can be employed in the creation of an historical narrative to more comprehensively understand the interplay between regional socioeconomic
Mobilization of phenol and dichlorophenol in unsaturated soils by non-uniform electrokinetics.
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
Comparison of FBP and Iterative Algorithms with Non-Uniform Angular Sampling
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
A crosstalk and non-uniformity correction method for the space-borne Compton polarimeter POLAR
NASA Astrophysics Data System (ADS)
Xiao, Hualin; Hajdas, Wojtek; Wu, Bobing; Produit, Nicolas; Bao, Tianwei; Batsch, Tadeusz; Cadoux, Franck; Chai, Junying; Dong, Yongwei; Kong, Minnan; Kong, Siwei; Rybka, Dominik K.; Leluc, Catherine; Li, Lu; Liu, Jiangtao; Liu, Xin; Marcinkowski, Radoslaw; Paniccia, Mercedes; Pohl, Martin; Rapin, Divic; Shi, Haoli; Song, Liming; Sun, Jianchao; Szabelski, Jacek; Wang, Ruijie; Wen, Xing; Xu, Hanhui; Zhang, Laiyu; Zhang, Li; Zhang, Shuangnan; Zhang, Xiaofeng; Zhang, Yongjie; Zwolinska, Ania
2016-10-01
In spite of extensive observations and numerous theoretical studies in the past decades several key questions related with Gamma-Ray Bursts (GRB) emission mechanisms are still to be answered. Precise detection of the GRB polarization carried out by dedicated instruments can provide new data and be an ultimate tool to unveil their real nature. A novel space-borne Compton polarimeter POLAR onboard the Chinese space station TG2 is designed to measure linear polarization of gamma-rays arriving from GRB prompt emissions. POLAR uses plastics scintillator bars (PS) as gamma-ray detectors and multi-anode photomultipliers (MAPMTs) for readout of the scintillation light. Inherent properties of such detection systems are crosstalk and non-uniformity. The crosstalk smears recorded energy over multiple channels making both non-uniformity corrections and energy calibration more difficult. Rigorous extraction of polarization observables requires to take such effects properly into account. We studied influence of the crosstalk on energy depositions during laboratory measurements with X-ray beams. A relation between genuine and recorded energy was deduced using an introduced model of data analysis. It postulates that both the crosstalk and non-uniformities can be described with a single matrix obtained in calibrations with mono-energetic X- and gamma-rays. Necessary corrections are introduced using matrix based equations allowing for proper evaluation of the measured GRB spectra. Validity of the method was established during dedicated experimental tests. The same approach can be also applied in space utilizing POLAR internal calibration sources. The introduced model is general and with some adjustments well suitable for data analysis from other MAPMT-based instruments.
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.
Forensic use of photo response non-uniformity of imaging sensors and a counter method.
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
Non-uniform absorption of terahertz radiation on superconducting hot electron bolometer microbridges
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.
[Role of spatio-temporal non uniformities in blood coagulation regulation].
Shibeko, A M; Ataullakhanov, F I
2013-01-01
This paper reviews some contemporary researches of thrombosis and hemostasis process that consider its spatio-temporal dynamics. Among them, there are platelet distribution in the blood vessel and the dependence of the platelet plug growth on the hematocrit level; influence of the tissue factor density on the blood coagulation onset and on the efficacy of some drugs, designed for the hemostasis improvement; regulation of blood coagulation by the flow rate. Mechanisms controlling the mentioned processes are described. Clinical significance and novel diagnostic and therapeutic approaches are discussed from the position of the spatio-temporal non uniformities of thrombosis and hemosatsis.
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.
A dispersion relation in bidust acoustic wave in non uniform stratified plasma
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.
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.
Lee, Hua
2016-04-01
The main focus of this paper is the design and formulation of a computationally efficient approach to the estimation of the angle of arrival with non-uniform reconfigurable receiver arrays. Subsequent to demodulation and matched filtering, the main signal processing task is a double-integration operation. The simplicity of this algorithm enables the implementation of the estimation procedure with simple operational amplifier (op-amp) circuits for real-time realization. This technique does not require uniform and structured array configurations, and is most effective for the estimation of angle of arrival with dynamically reconfigurable receiver arrays.
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
Numerical modelling and simulation of non-uniformly doped channel 6H-silicon carbide MOSFET
NASA Astrophysics Data System (ADS)
Kaushik, Navneet; Haldar, Subhasis; Gupta, Mridula; Gupta, R. S.
2004-03-01
An improved model for the non-uniformly doped channel 6H-SiC MOSFET incorporating the incomplete ionization of the dopant impurities using the Fermi-Dirac statistics is developed. The charge-sheet approach is used to evaluate the surface potential, quasi-fermi level, drain current and transconductance for all regions of operation, i.e. subthreshold, linear and saturation. Results so obtained are matched well with the simulated data for two different doping profiles. The improved model will be suitable for CAD (computer aided design) applications to predict the behaviour of the 6H-SiC MOSFET prior to actual device fabrication.
Forensic use of photo response non-uniformity of imaging sensors and a counter method.
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.
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.
Effects of magnetic field on the interaction between terahertz wave and non-uniform plasma slab
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.
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.
Non-uniform space charge limited current injection into a nano contact solid
Zhu, Y. B.; Ang, L. K.
2015-01-01
We have developed a two-dimensional (2D) non-uniform model to study the space charge limited (SCL) current injection into a trap-filled solid of nano-contact, such as organic materials and dielectrics. Assuming a solid of length D with a contact of width W, the enhancement over the well-known 1D uniform model is calculated as a function of W/D for different material properties, such as the dielectric constant (ε) and the trap distribution. The non-uniform current density profile due to edge effect is predicted. The findings reported here are different from the prior uniform 2D models, which are significant for small W/D when the size of the contact reaching nanometer scale, i.e. W = 50 nm for D = 1 μm. This model will be useful for the characterization of carrier mobility and properties of traps, which are critical to many novel devices (with small nano-contact) operating in the space charge limited condition reporting in novel device and its applications. Empirical formulas are given for future comparison with experimental results. PMID:25779769
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.
NASA Astrophysics Data System (ADS)
Lazar, Markus; Pellegrini, Yves-Patrick
2016-11-01
This work introduces original explicit solutions for the elastic fields radiated by non-uniformly moving, straight, screw or edge dislocations in an isotropic medium, in the form of time-integral representations in which acceleration-dependent contributions are explicitly separated out. These solutions are obtained by applying an isotropic regularization procedure to distributional expressions of the elastodynamic fields built on the Green tensor of the Navier equation. The obtained regularized field expressions are singularity-free, and depend on the dislocation density rather than on the plastic eigenstrain. They cover non-uniform motion at arbitrary speeds, including faster-than-wave ones. A numerical method of computation is discussed, that rests on discretizing motion along an arbitrary path in the plane transverse to the dislocation, into a succession of time intervals of constant velocity vector over which time-integrated contributions can be obtained in closed form. As a simple illustration, it is applied to the elastodynamic equivalent of the Tamm problem, where fields induced by a dislocation accelerated from rest beyond the longitudinal wave speed, and thereafter put to rest again, are computed. As expected, the proposed expressions produce Mach cones, the dynamic build-up and decay of which is illustrated by means of full-field calculations.
Filippov, Alexander E.; Gorb, Stanislav N.
2015-01-01
One of the important problems appearing in experimental realizations of artificial adhesives inspired by gecko foot hair is so-called clusterization. If an artificially produced structure is flexible enough to allow efficient contact with natural rough surfaces, after a few attachment–detachment cycles, the fibres of the structure tend to adhere one to another and form clusters. Normally, such clusters are much larger than original fibres and, because they are less flexible, form much worse adhesive contacts especially with the rough surfaces. Main problem here is that the forces responsible for the clusterization are the same intermolecular forces which attract fibres to fractal surface of the substrate. However, arrays of real gecko setae are much less susceptible to this problem. One of the possible reasons for this is that ends of the seta have more sophisticated non-uniformly distributed three-dimensional structure than that of existing artificial systems. In this paper, we simulated three-dimensional spatial geometry of non-uniformly distributed branches of nanofibres of the setal tip numerically, studied its attachment–detachment dynamics and discussed its advantages versus uniformly distributed geometry. PMID:25657843
Adhesion of voids to bimetal interfaces with non-uniform energies
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
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.
Vibrations of rectangular plates with arbitrary non-uniform elastic edge restraints
NASA Astrophysics Data System (ADS)
Zhang, X.; Li, Wen L.
2009-09-01
Arbitrary non-uniform elastic edge restraints represent the most general class of boundary conditions for plate problems, and are encountered in many real-world applications. The vibrations of plates with this kind of boundary conditions, however, are rarely studied in the literature perhaps because there is a lack of suitable analytical or numerical techniques. In this investigation, a general analytical method is derived for the vibration analysis of rectangular plates with elastic edge restraints of varying stiffness. Both rotational and translational restraints can be arbitrarily applied to an edge, and their stiffness distributions are generally described in terms of a set of invariants, cosine functions. The displacement solution is sought simply as a linear combination of several one- and two-dimensional Fourier cosine series expansions. All the unknown Fourier coefficients are treated equally as a set of independent generalized coordinates and solved directly from the Rayleigh-Ritz formulation. Unlike the existing techniques, the current method does not require any special procedures or schemes to deal with different boundary conditions. A few "classical" problems involving non-uniform rotational restraints are first solved and used to check the current solution against some of the existing techniques. The modal results are also presented for plates with more complicated boundary conditions in which an edge is no longer completely restrained in the translational direction. The accuracy and reliability of the current method are repeatedly demonstrated through all these examples.
Non-uniform Neutron Source Approximation for Iterative Reconstruction of Coded Source Images
Gregor, Jens; Bingham, Philip R
2016-01-01
X-ray and neutron optics both lack ray focusing capabilities. An x-ray source can be made small and powerful enough to facilitate high-resolution imaging while providing adequate flux. This is not yet possible for neutrons. One remedy is to employ a computational imaging technique such as magnified coded source imaging. The greatest challenge associated with successful reconstruction of high-resolution images from such radiographs is to precisely model the flux distribution for complex non-uniform neutron sources. We have developed a framework based on Monte Carlo simulation and iterative reconstruction that facilitates high- resolution coded source neutron imaging. In this paper, we define a methodology to empirically measure and approximate the flux profile of a non-uniform neutron source, and we show how to incorporate the result within the forward model of an iterative reconstruction algorithm. We assess improvement in image quality by comparing reconstructions based respectively on the new empirical forward model and our previous analytic models.
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.
Adhesion of voids to bimetal interfaces with non-uniform energies
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.
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.
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.
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.
Filippov, Alexander E; Gorb, Stanislav N
2015-02-01
One of the important problems appearing in experimental realizations of artificial adhesives inspired by gecko foot hair is so-called clusterization. If an artificially produced structure is flexible enough to allow efficient contact with natural rough surfaces, after a few attachment-detachment cycles, the fibres of the structure tend to adhere one to another and form clusters. Normally, such clusters are much larger than original fibres and, because they are less flexible, form much worse adhesive contacts especially with the rough surfaces. Main problem here is that the forces responsible for the clusterization are the same intermolecular forces which attract fibres to fractal surface of the substrate. However, arrays of real gecko setae are much less susceptible to this problem. One of the possible reasons for this is that ends of the seta have more sophisticated non-uniformly distributed three-dimensional structure than that of existing artificial systems. In this paper, we simulated three-dimensional spatial geometry of non-uniformly distributed branches of nanofibres of the setal tip numerically, studied its attachment-detachment dynamics and discussed its advantages versus uniformly distributed geometry.
Uniform and Non-uniform Thermoelement Subject to Lateral Heat Convection
NASA Astrophysics Data System (ADS)
Hameed, Amar Hasan; Kafafy, Raed
2013-03-01
A general energy equation of quasi-one-dimensional heat flow in a longitudinal thermoelement (TE) of a curved side that is subjected to an electric field and convection heat transfer on the curved surface is developed. The energy equation is solved for the temperature distribution in two cases; uniform cross-section TE and non-uniform cross-section TE. Analytical solutions for a uniform cross-section TE with uniform electrical and thermophysical properties are obtained, whereas numerical solutions are provided for a non-uniform cross-section TE. Two parameters playing a vital role in the thermal performance of the TE are identified: the heat resistance ratio ( HRR) and the energy growing ratio ( EGR). The HRR represents the ratio of the longitudinal conduction maximum thermal resistance to the lateral convection maximum thermal resistance. The EGR represents the ratio of Joule's electrical heating to Fourier's heat conduction. The effects of varying these two parameters, as well as the TE geometry, have been thoroughly investigated.
Spatially variant red blood cell crenation in alternating current non-uniform fieldsa
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
Non-uniform space charge limited current injection into a nano contact solid.
Zhu, Y B; Ang, L K
2015-01-01
We have developed a two-dimensional (2D) non-uniform model to study the space charge limited (SCL) current injection into a trap-filled solid of nano-contact, such as organic materials and dielectrics. Assuming a solid of length D with a contact of width W, the enhancement over the well-known 1D uniform model is calculated as a function of W/D for different material properties, such as the dielectric constant (ε) and the trap distribution. The non-uniform current density profile due to edge effect is predicted. The findings reported here are different from the prior uniform 2D models, which are significant for small W/D when the size of the contact reaching nanometer scale, i.e. W = 50 nm for D = 1 μm. This model will be useful for the characterization of carrier mobility and properties of traps, which are critical to many novel devices (with small nano-contact) operating in the space charge limited condition reporting in novel device and its applications. Empirical formulas are given for future comparison with experimental results. PMID:25779769
Calibration of EBT2 film by the PDD method with scanner non-uniformity correction
NASA Astrophysics Data System (ADS)
Chang, Liyun; Chui, Chen-Shou; Ding, Hueisch-Jy; Hwang, Ing-Ming; Ho, Sheng-Yow
2012-09-01
The EBT2 film together with a flatbed scanner is a convenient dosimetry QA tool for verification of clinical radiotherapy treatments. However, it suffers from a relatively high degree of uncertainty and a tedious film calibration process for every new lot of films, including cutting the films into several small pieces, exposing with different doses, restoring them back and selecting the proper region of interest (ROI) for each piece for curve fitting. In this work, we present a percentage depth dose (PDD) method that can accurately calibrate the EBT2 film together with the scanner non-uniformity correction and provide an easy way to perform film dosimetry. All films were scanned before and after the irradiation in one of the two homemade 2 mm thick acrylic frames (one portrait and the other landscape), which was located at a fixed position on the scan bed of an Epson 10 000XL scanner. After the pre-irradiated scan, the film was placed parallel to the beam central axis and sandwiched between six polystyrene plates (5 cm thick each), followed by irradiation of a 20 × 20 cm2 6 MV photon beam. Two different beams on times were used on two different films to deliver a dose to the film ranging from 32 to 320 cGy. After the post-irradiated scan, the net optical densities for a total of 235 points on the beam central axis on the films were auto-extracted and compared with the corresponding depth doses that were calculated through the measurement of a 0.6 cc farmer chamber and the related PDD table to perform the curve fitting. The portrait film location was selected for routine calibration, since the central beam axis on the film is parallel to the scanning direction, where non-uniformity correction is not needed (Ferreira et al 2009 Phys. Med. Biol. 54 1073-85). To perform the scanner non-uniformity calibration, the cross-beam profiles of the film were analysed by referencing the measured profiles from a Profiler™. Finally, to verify our method, the films were
NASA Astrophysics Data System (ADS)
Kim, Kyoung-Bo; Park, Hye-Hyang; Kwon, Ohseob; Kim, Moojin; Lee, Ki-Yong; Park, Yongwoo; Choi, JongHyun; Yu, CheolHo; Kim, Hye-Dong; Kim, Sung Chul; Chung, Ho-Kyoon
2008-01-01
We recently improved the brightness non-uniformity in active-matrix organic light-emitting diode (AMOLED) regarding non-uniform laser energy distribution by applying a “shot mixing” technique in sequential lateral solidification (SLS) method. Although the new SLS technique was employed, another brightness non-uniformity that appeared as oblique lines on AMOLED panels became a crucial issue. In this work, we attempted to investigate the origins of the non-uniformity. Our systematic analysis on the oblique lines revealed that the line type non-uniformity was attributed to both the SLS process and the thin-film transistor (TFT) fabrication processes. In particular, we found that such oblique patterns might be related to moiré patterns that appear when primary grain boundaries aligned in a repetitive pattern is placed over other repetitive TFT patterns such as metal lines. We adopted a method to diminish the moiré pattern type non-uniformity by applying top emission TFT structure.
Line profiles of water for the non-uniform density distribution in a cometary coma
NASA Astrophysics Data System (ADS)
Szutowicz, S.
2014-07-01
Observations and modeling of the molecular lines provide powerful diagnostics of the physical conditions in a cometary coma such as the density and the velocity structure. The pure rotational transitions of ortho- and para-water for several comets has been recently successfully provided by the Herschel space telescope. The rotational lines of water are optically thick. The water line shapes and the OTF maps taken with the high-resolution instrument Herschel/HIFI allowed to localize an active region on the nucleus of comet 10P/Tempel 2, close to its pole [1]. The evidence of anisotropic outgassing of comets may be interpreted with models of non-uniform distribution of activity. A numerical model for the simulation of water line emission in cometary coma is presented. The model is based on a non-uniform density distribution and the escape probability method for treating radiative transfer. The excitation model includes collisions with water and electrons, and infrared pumping. The equations of statistical equilibrium are solved in all cells of the coma with constant properties like density, temperature, and expansion velocity. The gas density profile in the regions of enhanced activity is described by a density function for emission into the cone. The density within the cone can be constant or vary as a function of the angle with respect to the outgassing axis. The outgassing pattern model assumes also the isotropic emission or uniform emission outside the cone where the temperature, the density and the expansion velocity can differ from those within the cone. Two different parts of the coma (material inside the cone and outside it) are radiatively coupled, thus the integrated mean intensity depends also on the non-local contributions to the radiation field. Synthetic line profiles of water (ground-level rotational transition) as seen with different telescope beams (e.g., Herschel, or MIRO - the Microwave Instrument for the Rosetta Orbiter) are computed at various
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
Improved photo response non-uniformity (PRNU) based source camera identification.
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
NASA Astrophysics Data System (ADS)
Choi, Y.; Ju, S.; Chae, S. H.; Jun, S.; Park, S. M.; Lee, S.; Lee, H. W.; Ji, C.-H.
2013-12-01
We present a non-resonant vibration energy harvesting device using springless spherical permanent magnet with non-uniform mass distribution as a proof mass. The magnet has its center-of-mass below the geometrical center, which generates a roly-poly-like motion in response to external vibrations. Two different types of magnet assemblies with different center-of-mass position have been fabricated and tested. Using the roly-poly-like magnets, proof-of-concept electromagnetic energy harvesters have been fabricated and tested. Moreover, effect of ferrofluid as a lubricant has been tested with the fabricated energy harvester. Maximum open-circuit voltage of 154.4mV and output power of 4.53μW have been obtained at 3g vibration at 12Hz with the fabricated device.
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.
Elliptical metallic hollow fiber inner-coated with non-uniform dielectric layer.
Tang, Xiaoli; Yu, Zhuzheng; Tu, Xuecou; Chen, Jian; Argyros, Alexander; Kuhlmey, Boris T; Shi, Yiwei
2015-08-24
We report on the fabrication and characterization of an elliptical hollow fiber inner coated with a silver layer and a dielectric layer for polarization maintaining and low loss transmission of terahertz (THz) radiation. The primary purpose of adding the dielectric layer is to prevent the silver layer from oxidation. The thickness of the dielectric layer is non-uniform owing to the surface tension of the coating, which was initially applied as a liquid. Transmission loss and polarization maintenance are experimentally characterized. Effects of the dielectric layer on transmission properties are analyzed by comparing the fiber to Ag-only fiber. Results show that a dielectric layer with thickness less than λ/10 can effectively decreases the power distributed on the metal surface and thus can practically reduce loss resulting from roughness of the silver layer. Bending effects on transmission loss and polarization maintenance are also investigated.
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.
Online blind calibration of non-uniform photodetectors: application to endomicroscopy.
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
Non-uniform shrinkage of multiple-walled carbon nanotubes under in situ electron beam irradiation
NASA Astrophysics Data System (ADS)
Li, Lunxiong; Su, Jiangbin; Zhu, Xianfang
2016-10-01
Instability of multiple-walled carbon nanotubes (MWCNTs) was investigated by in situ transmission electron microscopy at room temperature. Specially, the non-uniform shrinkage of tubes was found: The pristine MWCNT shrank preferentially in its axial direction from the most curved free cap end of the tube, but the shrinkage of the tube diameter was offset by the axial shrinkage: For the complex MWCNT, the two inner MWCNTs also preferentially axially shrank from their most curved cap ends and separated from each other. However, for the effect of the radial pressure from the out walls which enveloped the two inner tubes and the tube amorphization, the two inner tubes were extruded to come close to each other and finally touched again. The new "evaporation" and "diffusion" mechanisms of carbon atoms as driven by the nano-curvature of CNT and the electron beam-induced athermal activation were suggested to explain the above phenomena.
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.
Investigation of non-uniform radiation damage observed in the ZEUS Beam Pipe Calorimeter at HERA
NASA Astrophysics Data System (ADS)
Bohnet, I.; Fricke, U.; Surrow, B.; Wick, K.
1999-08-01
The ZEUS Beam Pipe Calorimeter (BPC) is a small tungsten/scintillator sampling calorimeter. It is positioned at a distance of approximately 4 cm from the HERA beams and approximately 3 m from the interaction point. The accumulated doses measured at the front side of the BPC during the HERA runs 1995, 1996 and 1997 were 12 kGy, 11 kGy and 2.5 kGy, respectively. The radiation dose influenced the optical components of the BPC. The degradation of some of the scintillators due to radiation damage has been examined using different monitoring systems. A simulation code was developed which describes quantitatively the effects of non-uniform radiation damage. The following report describes the radiation monitoring, the effects on the scintillator material and the impact on the energy linearity of the BPC.
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.
Distribution of non-uniform demagnetization fields in paramagnetic bulk solids
NASA Astrophysics Data System (ADS)
Dickinson, Ross; Royappa, A. Timothy; Tone, Florentina; Ujj, Laszlo; Wu, Guoqing
2011-07-01
A general calculation for the distribution of non-uniform demagnetization fields in paramagnetic bulk solids is described and the fields for various sample geometries are calculated. Cones, ellipsoids, paraboloids, and hyperboloids with similar sample aspect ratios are considered. Significant differences in their demagnetization fields are observed. The calculation shows that the demagnetization field magnitudes decrease along the axis of symmetry (along z) where an externally applied magnetic field is aligned, and increase in the vicinity of the lateral surfaces with the largest field values found in the cone and the narrowest field distributions found in the hyperboloid. An application is made to the theoretical modeling of the 1H-NMR spectra of a single crystal of field-induced superconductor λ-(BETS)/>2 FeCl4 with a rectangular sample geometry, providing a good fit to the measured NMR spectra.
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.
Low voltage transflective blue-phase liquid crystal display with a non-uniform etching substrate
NASA Astrophysics Data System (ADS)
Wang, Jian; Mao, Jiang-Lin; Fan, Hao-Xiang; Wang, Qiong-Hua
2016-09-01
A transflective polymer-stabilized blue-phase liquid crystal display (BP-LCD) with a non-uniform etching substrate is proposed. In-plane switching (IPS) electrodes on the bottom substrate are put on the different gaps, and the bottom substrate between the electrodes is etched into different depths in transmissive (T) and reflective (R) regions. This structure can balance the optical phase retardation in the two regions and is helpful to achieve well-matched voltag-dependent transmittance and reflectance curves. This transflective display has high optical efficiency, a wide viewing angle, and low operating voltage (approximately 6 V). Project supported by the National Natural Science Foundation of China (Grant Nos. 61535007 and 61320106015) and the National Basic Research Program of China (Grant No. 2013CB328802).
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.
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.
Analytical and experimental study on mild steel dampers with non-uniform vertical slits
NASA Astrophysics Data System (ADS)
Zheng, Jie; Li, Aiqun; Guo, Tong
2015-03-01
This study proposes a novel mild steel damper with non-uniform vertical slits. The influence of different shapes of vertical slits of the core energy plate on the energy dissipation and buckling resistance capacities is analyzed. Based on the theoretical analysis, formulas of key parameters of the dampers, including the elastic lateral stiffness, shear bearing capacity and yield displacement, are derived. The effectiveness of the proposed damper is demonstrated through pseudo static tests on four 0.25-scale specimens. Performance of these dampers, i.e. cyclic deformation, stress distribution, energy dissipation capacity, etc., are presented and discussed. Using the numerical models of dampers calibrated through test data, earthquake time-history analyses were conducted, and it is observed that the dampers significantly reduce the seismic responses of the prototype frame and have a desirable energy dissipation capacity.
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.
Optoacoustic tomography with varying illumination and non-uniform detection patterns.
Jetzfellner, Thomas; Rosenthal, Amir; Buehler, Andreas; Dima, Alexander; Englmeier, Karl-Hans; Ntziachristos, Vasilis; Razansky, Daniel
2010-11-01
Quantification of tissue morphology and biomarker distribution by means of optoacoustic tomography is an important and longstanding challenge, mainly caused by the complex heterogeneous structure of biological tissues as well as the lack of accurate and robust reconstruction algorithms. The recently introduced model-based inversion approaches were shown to mitigate some of reconstruction artifacts associated with the commonly used back-projection schemes, while providing an excellent platform for obtaining quantified maps of optical energy deposition in experimental configurations of various complexity. In this work, we introduce a weighted model-based approach, capable of overcoming reconstruction challenges caused by per-projection variations of object's illumination and other partial illumination effects. The universal weighting procedure is equally shown to reduce reconstruction artifacts associated with other experimental imperfections, such as non-uniform transducer sensitivity fields. Significant improvements in image fidelity and quantification are showcased both numerically and experimentally on tissue phantoms and mice.
Robust engineering design optimization with non-uniform rational B-splines-based metamodels
NASA Astrophysics Data System (ADS)
Steuben, John C.; Turner, Cameron J.; Crawford, Richard H.
2013-07-01
Non-uniform rational B-splines (NURBs) demonstrate properties that make them attractive as metamodels, or surrogate models, for engineering design purposes. Previous research has resulted in the development of algorithms capable of fitting NURBs-based metamodels to engineering design spaces, and optimizing these models. This article presents an approach to robust optimization that employs NURBs-based metamodels. This robust optimization technique exploits the unique structure of NURBs-based metamodels to derive a simple but effective robustness metric. An algorithm is demonstrated that uses this metric to weigh robustness against optimality, and visualizes the trade-offs between these metamodel properties. This approach is demonstrated with test problems of increasing dimensionality, including several practical design challenges.
Tuning of non-uniform switch toughening in ferroelectric composites by an electric field
NASA Astrophysics Data System (ADS)
Xia, Xiaodong; Zhong, Zheng
2016-09-01
This paper deals with a mode III interfacial crack subject to anti-plane stress and in-plane electric fields. The analysis concentrates on the tuning of fracture toughness from non-uniform ferroelectric-ferroelastic domain switching by an electric field. The electric loading changes the size of the asymmetric switching zone. Employing the weight function method, we obtain the electrically-dependent switch toughening for stationary and quasi-static growing interfacial cracks, respectively. Multi-domain solutions are derived for non-poled and fully-poled ferroelectric composites. Numerical results are presented on the electric field tuning of the critical applied stress intensity factor. The research provides ways to optimize fracture properties of ferroelectric composites by altering the electric field.
Probing Invisible, Excited Protein States by Non-Uniformly Sampled Pseudo-4D CEST Spectroscopy.
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
Ni, Saihua; Sun, Wenye; Sun, Baoyin; Zhou, Qiang; Wang, Qiang; Wang, Zhenming; Gu, Jihua; Tao, Zhi
2014-06-01
To enhance speech recognition, as well as Mandarin tone recognition in noice, we proposed a speech coding strategy called zero-crossing of fine structure in low frequency (LFFS) for cochlear implant based on low frequency non-uniform sampling (LFFS for short). In the range of frequency perceived boundary of human ear, we used zero-crossing time of the fine structure to generate the stimulus pulse sequences based on the frequency selection rule. Acoustic simulation results showed that although on quiet background the performance of LFFS was similar to continuous interleaved sampling (CIS), on the noise background the performance of LFFS in Chinese tones, words and sentences were significantly better than CIS. In addition to this, we also got better Mandarin recognition factors distribution by using the improved index distribution model. LFFS contains more tonal information which was able to effectively improve Mandarin recognition of the cochlear implant. PMID:25219227
Non-uniform dispersion of the source-sink relationship alters wavefront curvature.
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
An analytical approach to quantitative reconstruction of non-uniform attenuated brain SPECT.
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
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.
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.
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.
NASA Astrophysics Data System (ADS)
Lebedev, Yu A.
2015-10-01
Microwave discharges (MD) are widely used as a source of non-equilibrium low pressure plasma for different applications. This paper reviews the methods of microwave plasma generation at pressures from 10-2 approximately to 30 kPa with centimeter-millimeter wavelength microwaves on the basis of scientific publications since 1950 up to the present. The review consists of 16 sections. A general look at MDs and their application is given in the introduction, together with a description of a typical block-schema of the microwave plasma generator, classification of MD, and attractive features of MD. Sections 2-12 describe the different methods of microwave plasma generators on the basis of cavity and waveguide discharges, surface and slow wave discharges, discharges with distributed energy input, initiated and surface discharges, discharges in wave beams, discharges with stochastically jumping phases of microwaves, discharges in an external magnetic field and discharges with a combination of microwave field and dc and RF fields. These methods provide the possibility of producing nonequilibriun high density plasma in small and large chambers for many applications. Plasma chemical activity of nonequilibrium microwave plasma is analyzed in section 13. A short consideration of the history and status of the problem is given. The main areas of microwave plasma application are briefly described in section 14. Non-uniformity is the inherent property of the majority of electrical discharges and MDs are no exception. Peculiarities of physical-chemical processes in strongly non-uniform MDs are demonstrated placing high emphasis on the influence of small noble gas additions to the main plasma gas (section 15). The review is illustrated by 80 figures. The list of references contains 350 scientific publications.
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.
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.
Current localization, non-uniform heating, and failures of ZnO varistors
Bartkowiak, M. |
1997-11-01
Metal oxide varistors have highly nonlinear electrical characteristics and are widely used as devices for over-voltage protection. Varistor applications range from the use of small varistors to protect delicate electronic components to the use of much larger varistors for the protection of electrical-power-distribution systems. Non-uniform heating of ZnO varistors by electrical pulses occurs on three different spatial scales: (1) microscopic (sub-micron), (2) intermediate (sub-millimeter), and (3) macroscopic (of order of millimeters or centimeters). Heating on these scales has different origins and different consequences for device failure in large and small varistors. On the microscopic scale, the heating localizes in strings of tiny hot spots. They occur at the grain boundaries in a conducting path where the potential is dropped across Schottky-type barriers. These observations are interpreted by applying transport theory and using computer simulations. It is shown that the heat transfer on a scale of the grain size is too fast to permit temperature differences that could cause a varistor failure. On an intermediate size scale, the heating is most intense along localized electrical paths. The high electrical conductivity of these paths has microstructural origin, i.e., it derives from the statistical fluctuations of grain sizes and grain boundary properties. Current localization on the intermediate size scale appears to be significant only in small varistors. On the macroscopic scale, current localization in large blocks can be attributed to inhomogeneities in the electrical properties which originate during ceramic processing. The resulting non-uniform heating is shown to cause destructive failures of large varistor blocks.
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
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.
Modeling and reconfiguration of solar photovoltaic arrays under non-uniform shadow conditions
NASA Astrophysics Data System (ADS)
Nguyen, Dung Duc
Mass production and use of electricity generated from solar energy has become very common recently because of the environmental threats arising from the production of electricity from fossil fuels and nuclear power. The obvious benefits of solar energy are clean energy production and infinite supply of daylight. The main disadvantage is the high cost. In these photovoltaic systems, semiconductor materials convert the solar light into electrical energy. Current versus voltage characteristics of the solar cells are nonlinear, thus leading to technical control challenges. In the first order approximation, output power of a solar array is proportional to the irradiance of sunlight. However, in many applications, such as solar power plants, building integrated photovoltaic or solar tents, the solar photovoltaic arrays might be illuminated non-uniformly. The cause of non-uniform illumination may be the shadow of clouds, the trees, booms, neighbor's houses, or the shadow of one solar array on the other, etc. This further leads to nonlinearities in characteristics. Because of the nature of the electrical characteristics of solar cells, the maximum power losses are not proportional to the shadow, but magnify nonlinearly [1]. Further, shadows of solar PV array can cause other undesired effects: (1) The power actually generated from the solar PV array is much less than designed. At some systems, the annual losses because of the shadow effects can be reached 10%. Thus, the probability for "loss of load" increases [2]. (2) The local hot spot in the shaded part of the solar PV array can damage the solar cells. The shaded solar cells may be work on the negative voltage region and become a resistive load and absorb power. Bypass diodes are sometimes connected parallel to solar cells to protect them from damage. However, in most cases, just one diode is connected in parallel to group of solar cells [3], and this hidden the potential power output of the array. This proposed research
Flow instabilities in non-uniformly heated helium jet arrays used for divertor PFCs
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/m^{2} off-normal heat flux applied over a 25 mm^{2} area in addition to the nominal 5 MW/m^{2} applied over a 75 mm^{2} 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 mm^{2} 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
Flow instabilities in non-uniformly heated helium jet arrays used for divertor PFCs
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
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
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
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
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.
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.
45 CFR 96.87 - Leveraging incentive program.
Code of Federal Regulations, 2012 CFR
2012-10-01
... under section 2607A(c)(2) of Public Law 97-35 (42 U.S.C. 8626a(c)(2)). (iv) State the net dollar value... based on the final net value of countable leveraged resources provided to low-income households during... net value of the countable leveraged resources provided by all grantees during the base...
45 CFR 96.87 - Leveraging incentive program.
Code of Federal Regulations, 2010 CFR
2010-10-01
... under section 2607A(c)(2) of Public Law 97-35 (42 U.S.C. 8626a(c)(2)). (iv) State the net dollar value... based on the final net value of countable leveraged resources provided to low-income households during... net value of the countable leveraged resources provided by all grantees during the base...
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
Strategy as stretch and leverage.
Hamel, G; Prahalad, C K
1993-01-01
Global competition is not just product versus product or company versus company. It is mind-set versus mind-set. Driven to understand the dynamics of competition, we have learned a lot about what makes one company more successful than another. But to find the root of competitiveness--to understand why some companies create new forms of competitive advantage while others watch and follow--we must look at strategic mind-sets. For many managers, "being strategic" means pursuing opportunities that fit the company's resources. This approach is not wrong, Gary Hamel and C.K. Prahalad contend, but it obscures an approach in which "stretch" supplements fit and being strategic means creating a chasm between ambition and resources. Toyota, CNN, British Airways, Sony, and others all displaced competitors with stronger reputations and deeper pockets. Their secret? In each case, the winner had greater ambition than its well-endowed rivals. Winners also find less resource-intensive ways of achieving their ambitious goals. This is where leverage complements the strategic allocation of resources. Managers at competitive companies can get a bigger bang for their buck in five basic ways: by concentrating resources around strategic goals; by accumulating resources more efficiently; by complementing one kind of resource with another; by conserving resources whenever they can; and by recovering resources from the market-place as quickly as possible. As recent competitive battles have demonstrated, abundant resources can't guarantee continued industry leadership.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:10124635
n-dimensional non uniform rational b-splines for metamodeling
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.
Non-uniform sampling: post-Fourier era of NMR data collection and processing.
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.
Regional paleofire regimes affected by non-uniform climate, vegetation and human drivers.
Blarquez, Olivier; Ali, Adam A; Girardin, Martin P; Grondin, Pierre; Fréchette, Bianca; Bergeron, Yves; Hély, Christelle
2015-09-02
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.
The importance of non-uniformities in mechano-electric coupling for ventricular arrhythmias.
Quinn, T Alexander
2014-01-01
Cardiac mechanical and electrical activities are tightly linked through an intra-cardiac regulatory loop (mechano-electric coupling). This connection is essential for normal heart function and auto-regulation. In diseases associated with altered myocardial mechanical properties or function, however, feedback from the mechanical environment to the origin and spread of excitation can result in deadly cardiac arrhythmias. Ventricular tachyarrhythmias, especially, are encountered in cardiac diseases associated with volume and pressure overload or changes in tissue mechanics. Little is known about the influence of changes in mechano-electric coupling on cardiac rhythm in these settings or the potential therapeutic benefit of its manipulation. Improved understanding may be central to explaining the origin of arrhythmias that occur with these pathologies and to the development of novel mechanics-based therapies. The present review explores the potential role of mechano-electric coupling in ventricular arrhythmogenesis, with a focus on the importance of non-uniformity in mechanical function for the induction and sustenance of ventricular tachyarrhythmias.
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.
Effect of Non-Uniform Divertor Target Properties on Scrape-off Layer Plasma Equilibrium
NASA Astrophysics Data System (ADS)
Subba, Fabio; Tskhakaya, David; Holzmueller-Steinacker, Ulrike; Schupfer, Nikolaus; Stanojevic, Mladen; Kuhn, Siegbert
2000-10-01
It is well known that plasma in contact with a solid wall develops a boundary layer, which typically consists of a thin Debye sheath adjacent to the wall and a more extended presheath providing the transition to the unperturbed plasma [1,2]. As the physical interaction of the plasma with the surrounding universe is mainly localized in this region, it may be expected that this boundary layer, which sensitively controls particle and energy fluxes to and from the plasma, plays an important role in determining the properties of the overall plasma equilibrium. On the other hand, it is generally assumed that the details of the adopted boundary-layer models do not influence dramatically the overall SOL behavior. However, little quantitative literature is actually available on the subject [3]. The purpose of this paper is to make a contribution towards clarifying this issue. In particular, we will use the B2.5 code [4] for studying the influence of non-uniformity of the effective secondary-electron emission coefficient (ESEEC) on the plasma parameters in the SOL.
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.
Bed Slope Effect on Non-uniform Flow through Porous Media
NASA Astrophysics Data System (ADS)
Bhanu Prakasham Reddy, N.; Krishnaiah, S.; Ramakrishna Reddy, M.
2016-08-01
The tilting angle or bed slope (φ) effect on piezometric head was studied in a tilting angle converging permeameter for different rate of flows and for different bed slopes or tilting angles (φ) and the equipotential lines of piezometric head are depicted pictorially to establish the suitability of the convergent flow assumption and have a proper insight into the subject of seepage flow. The porosity effect is considered while computing seepage velocity (V), linear parameter, non-linear parameter, increases with decrease of porosity (N) and increases with decrease of angle of inclination. In order to meet the objective of this study, a crushed rock of size 7.30 mm was used as media and water as fluid, to develop curves relating friction factor (FR) and Reynolds number (RR) for different ratios of width using hydraulic radius (R) as characteristic length for different bed slopes or tilting angles (φ). The effect of varying tilting angles (φ) on head loss of fluid flow through porous media when packed between convergent boundaries for different ratios of width (B1/B2) was studied and inferred that tilting angles (φ) have a significant effect on the non uniform flow.
Accurate scoring of non-uniform sampling schemes for quantitative NMR
Aoto, Phillip C.; Fenwick, R. Bryn; Kroon, Gerard J. A.; Wright, Peter E.
2014-01-01
Non-uniform sampling (NUS) in NMR spectroscopy is a recognized and powerful tool to minimize acquisition time. Recent advances in reconstruction methodologies are paving the way for the use of NUS in quantitative applications, where accurate measurement of peak intensities is crucial. The presence or absence of NUS artifacts in reconstructed spectra ultimately determines the success of NUS in quantitative NMR. The quality of reconstructed spectra from NUS acquired data is dependent upon the quality of the sampling scheme. Here we demonstrate that the best performing sampling schemes make up a very small percentage of the total randomly generated schemes. A scoring method is found to accurately predict the quantitative similarity between reconstructed NUS spectra and those of fully sampled spectra. We present an easy-to-use protocol to batch generate and rank optimal Poisson-gap NUS schedules for use with 2D NMR with minimized noise and accurate signal reproduction, without the need for the creation of synthetic spectra. PMID:25063954
NASA Astrophysics Data System (ADS)
Connell, Mark A.; Bowyer, Paul J.; Adam Bone, P.; Davis, Adrian L.; Swanson, Alistair G.; Nilsson, Mathias; Morris, Gareth A.
2009-05-01
Pulsed field gradient NMR is a well-established technique for the determination of self-diffusion coefficients. However, a significant source of systematic error exists in the spatial variation of the applied pulsed field gradient. Non-uniform pulsed field gradients cause the decay of peak amplitudes to deviate from the expected exponential dependence on gradient squared. This has two undesirable effects: the apparent diffusion coefficient will deviate from the true value to an extent determined by the choice of experimental parameters, and the error estimated by the nonlinear least squares fitting will contain a significant systematic contribution. In particular, the apparent diffusion coefficient determined by exponential fitting of the diffusional attenuation of NMR signals will depend both on the exact pulse widths used and on the range of gradient amplitudes chosen. These problems can be partially compensated for if experimental attenuation data are fitted to a function corrected for the measured spatial dependence of the gradient and signal strength. This study describes a general alternative to existing methods for the calibration of NMR diffusion measurements. The dominant longitudinal variation of the pulsed field gradient amplitude and the signal strength are mapped by measuring pulsed field gradient echoes in the presence of a weak read gradient. These data are then used to construct a predicted signal decay function for the whole sample, which is parameterised as the exponential of a power series. Results are presented which compare diffusion coefficients obtained using the new calibration method with previous literature values.
Temperature model for process impact non-uniformity in genipin recovery by high pressure processing.
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.
Non-uniform velocity profile mechanism for flame stabilization in a porous radiant burner
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)
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
Modeling and Compensating Temperature-Dependent Non-Uniformity Noise in IR Microbolometer Cameras.
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
Non-uniformity correction with temperature influence compensation in microbolometer detector
NASA Astrophysics Data System (ADS)
Krupiński, Michał; Bieszczad, Grzegorz; Gogler, Sławomir; Madura, Henryk
2015-05-01
Because of a significant impact of the microbolometer array temperature on the infrared image quality, it is necessary to compensate the influence of the temperature on the NUC process. In the most common applications two approaches are used: the first is a stabilization of the microbolometer array temperature by a thermoelectric cooler, the second is updating correction coefficients obtained from reference source, for example a shutter [14]. Both of the most common approaches have theirs disadvantages. The first case needs a considerable amount of energy for temperature stabilisation. The second one needs a reference target and a mechanical procedure to place the target at the front of the detector. Additionally, during calibration the reference target is blocking radiation from the scene, thus interrupting measurements with the thermal camera. In the article a non-uniformity correction method is presented which allows to compensate for the influence of detector's temperature drift. For this purpose, dependency between output signal value and the temperature of the detector array was investigated. Additionally the influence of the temperature on the Offset and Gain coefficients was measured. Presented method utilizes estimated dependency between output signal of detectors and their temperature. In the presented method, the dependency between output signal value and the temperature of the detector is estimated during time of starting detector. The coefficients are estimated for every pixel. In the article proposed method allows to compensate the influence of detectors temperature fluctuation and increase a time between shutter actuation process.
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.
Generation of kinetic Alfven waves by beam-plasma interaction in non-uniform plasma
Hong, M. H.; Lin, Y.; Wang, X. Y.
2012-07-15
This work reports a novel mechanism of the generation of kinetic Alfven waves (KAWs) using a two-dimensional hybrid simulation: the KAWs are generated by ion beam-plasma interaction in a non-uniform plasma boundary layer, in which the bulk velocity of the ion beam is assumed to be parallel to the ambient magnetic field. As a result of the beam-plasma interaction, strong shear Alfven waves as well as fast mode compressional waves are first generated on the side of the boundary layer with a high density and thus a low Alfven speed, propagating along the background magnetic field. Later, Alfven waves also form inside the boundary layer with a continuous spectrum. As the perpendicular wave number k{sub Up-Tack} of these unstably excited waves increases with time, large-amplitude, short wavelength KAWs with k{sub Up-Tack } Much-Greater-Than k{sub ||} clearly form in the boundary layer. The physics for the generation of KAWs is discussed.
Optimized design of thermo-mechanically loaded non-uniform bars by using a variational method
NASA Astrophysics Data System (ADS)
Nayak, P.; Saha, K. N.
2016-08-01
The present paper evaluates the axial strain and stress of a thermo-mechanically loaded non-uniform bar by using a numerical method based on a variational principle. The solutions are obtained up to the elastic limit of the material based on the assumptions that material properties are independent of temperature variation and plane cross-sections remain plane maintaining axisymmetry. This approximation is carried out by Galerkin's principle, using a linear combination of sets of orthogonal co-ordinate functions which satisfy prescribed boundary conditions. The solution algorithm is implemented with the help of MATLAB® computational simulation software. Some numerical results of thermoelastic field are presented and discussed for different bar materials such as mild steel, copper, aluminium alloy 6061 (Al alloy 6061), aluminium alloy 7075 (Al alloy 7075) and diamond. The effect of geometry parameters like aspect ratio, slenderness ratio and the type of taperness is investigated and the relevant results are obtained in dimensional form. The term bar used in this paper is in generic sense and hence the formulation is applicable for all one dimensional elements, e.g., rods, pipes, truss members, etc.
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.
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).
Non-uniform sampling: post-Fourier era of NMR data collection and processing.
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
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.
Bed Slope Effect on Non-uniform Flow through Porous Media
NASA Astrophysics Data System (ADS)
Bhanu Prakasham Reddy, N.; Krishnaiah, S.; Ramakrishna Reddy, M.
2016-09-01
The tilting angle or bed slope (φ) effect on piezometric head was studied in a tilting angle converging permeameter for different rate of flows and for different bed slopes or tilting angles (φ) and the equipotential lines of piezometric head are depicted pictorially to establish the suitability of the convergent flow assumption and have a proper insight into the subject of seepage flow. The porosity effect is considered while computing seepage velocity (V), linear parameter, non-linear parameter, increases with decrease of porosity (N) and increases with decrease of angle of inclination. In order to meet the objective of this study, a crushed rock of size 7.30 mm was used as media and water as fluid, to develop curves relating friction factor (FR) and Reynolds number (RR) for different ratios of width using hydraulic radius (R) as characteristic length for different bed slopes or tilting angles (φ). The effect of varying tilting angles (φ) on head loss of fluid flow through porous media when packed between convergent boundaries for different ratios of width (B1/B2) was studied and inferred that tilting angles (φ) have a significant effect on the non uniform flow.
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.
The lateral line is necessary for blind cavefish rheotaxis in non-uniform flow.
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
Regional paleofire regimes affected by non-uniform climate, vegetation and human drivers
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
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.
Phase separation dynamics of simple liquids in non-uniform electric fields.
Galanis, Jennifer; Tsori, Yoav
2014-03-28
Spatially non-uniform electric fields can phase separate initially homogeneous mixtures of liquids. Here, we investigate the dynamics of phase separation using a modified Cahn-Hilliard equation and find three kinetically distinct regimes in the phase diagram: (1) discontinuous and (2) continuous interface formation kinetics and (3) a metastable state. By considering all possible solutions of the free energy density, we are able to map the time behavior in the vicinity of the interface as a series of equilibrium interfaces "moving" in the parameter space of the equilibrium phase diagram. The kinetic phase diagram, consequently, contains an "emergence line" that delineates the experimental conditions where a non-equilibrium interface can be forbidden from forming close to a charged surface. When the interface can form on the charged surface, an abrupt transition occurs that produces electrical signatures which distinguish the discontinuous from the continuous transition region. The third kinetic regime describes non-spontaneous phase separation and potential metastable states, and is bounded by the "electrostatic spinodal" line. The equivalent kinetic regimes exist in closed systems and can be found by considering an effective concentration in an open system. PMID:24697457
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.
Size Distribution Imaging by Non-Uniform Oscillating-Gradient Spin Echo (NOGSE) MRI.
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
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
Proposal for a Domain Wall Nano-Oscillator driven by Non-uniform Spin Currents
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
The effect of a non-uniform turning kernel on ant trail morphology.
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
Computational imaging from non-uniform degradation of staggered TDI thermal infrared imager.
Sun, Tao; Liu, Jian Guo; Shi, Yan; Chen, Wangli; Qin, Qianqing; Zhang, Zijian
2015-09-21
For the Time Delay Integration (TDI) staggered line-scanning thermal infrared imager, a Computational Imaging (CI) approach is developed to achieve higher spatial resolution images. After a thorough analysis of the causes of non-uniform image displacement and degradation for multi-channel staggered TDI arrays, the study aims to approach one-dimensional (1D) sub-pixel displacement estimation and superposition of images from time-division multiplexing scanning lines. Under the assumption that a thermal image is 2D piecewise C(2) smooth, a sparse-and-smooth deconvolution algorithm with L1-norm regularization terms combining the first and second order derivative operators is proposed to restore high frequency components and to suppress aliasing simultaneously. It is theoretically and experimentally demonstrated, with simulation and airborne thermal infrared images, that this is a state-of-the-art practical CI method to reconstruct clear images with higher frequency components from raw thermal images that are subject to instantaneous distortion and blurring. PMID:26406660
Modeling and Compensating Temperature-Dependent Non-Uniformity Noise in IR Microbolometer Cameras
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
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.
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.
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.
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.
Evaluation of rapid cell division in non-uniform cell cycles.
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.
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.
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.
New method for solving inductive electric fields in the non-uniformly conducting ionosphere
NASA Astrophysics Data System (ADS)
Vanhamäki, H.; Amm, O.; Viljanen, A.
2006-10-01
We present a new calculation method for solving inductive electric fields in the ionosphere. The time series of the potential part of the ionospheric electric field, together with the Hall and Pedersen conductances serves as the input to this method. The output is the time series of the induced rotational part of the ionospheric electric field. The calculation method works in the time-domain and can be used with non-uniform, time-dependent conductances. In addition, no particular symmetry requirements are imposed on the input potential electric field. The presented method makes use of special non-local vector basis functions called the Cartesian Elementary Current Systems (CECS). This vector basis offers a convenient way of representing curl-free and divergence-free parts of 2-dimensional vector fields and makes it possible to solve the induction problem using simple linear algebra. The new calculation method is validated by comparing it with previously published results for Alfvén wave reflection from a uniformly conducting ionosphere.
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.
Improvement of the growth and yield of lettuce plants by non-uniform magnetic fields.
De Souza, Angel; Sueiro, Lilita; González, Luis Manuel; Licea, Luis; Porras, Elia Porras; Gilart, Fidel
2008-01-01
Influence of pre-sowing magnetic treatments on plant growth and final yield of lettuce (cv. Black Seeded Simpson) were studied under organoponic conditions. Lettuce seeds were exposed to full-wave rectified sinusoidal non uniform magnetic fields (MFs) induced by an electromagnet at 120 mT (rms) for 3 min, 160 mT (rms) for 1 min, and 160 mT (rms) for 5 min. Non treated seeds were considered as controls. Plants were grown in experimental stonemasons (25.2 m(2)) of an organoponic and cultivated according to standard agricultural practices. During nursery and vegetative growth stages, samples were collected at regular intervals for growth analyses. At physiological maturity, the plants were harvested from each stonemason and the final yield and yield parameters were determined. In the nursery stage, the magnetic treatments induced a significant increase of root length and shoot height in plants derived from magnetically treated seeds. In the vegetative stage, the relative growth rates of plants derived from magnetically exposed seeds were greater than those shown by the control plants. At maturity stage, all magnetic treatments increased significantly (p < 0.05)--plant height, leaf area per plant, final yield per area, and fresh mass per plant--in comparison with the controls. Pre-sowing magnetic treatments would enhance the growth and final yield of lettuce crop. PMID:18568935
Modeling and Compensating Temperature-Dependent Non-Uniformity Noise in IR Microbolometer Cameras.
Wolf, Alejandro; Pezoa, Jorge E; Figueroa, Miguel
2016-07-19
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.
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.
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.
State Estimation for a Class of Non-Uniform Sampling Systems with Missing Measurements
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
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.
Regional paleofire regimes affected by non-uniform climate, vegetation and human drivers.
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
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).
In-flight Density Profiles and Areal Density Non-uniformities of ICF Implosions
NASA Astrophysics Data System (ADS)
Tommasini, Riccardo
2014-10-01
Implosion efficiency depends on keeping the in-flight ablator and fuel as close as possible to spherical at all times while maintaining the required implosion velocity and in-flight aspect ratio. Asymmetries and areal density non-uniformities seeded by time-dependent drive variations and target imperfections grow in time as the capsule implodes, with growth rates that are amplified by instabilities. One way to diagnose them is by imaging the self-emission from the implosion core. However this technique, besides only providing direct information of the shape of the hot emission region at final assembly, presents complications due to competition between emission gradients and reabsorption. Time resolved radiographic imaging, being insensitive to this effect, is therefore an important tool for diagnosing the ablator and the shell in inertial confinement fusion (ICF) implosions. Experiments aimed at measuring the density, areal density and areal density asymmetries of the shell in ICF implosions have been performed using two different radiography techniques on the National Ignition Facility. We will report the results from both 1D and 2D geometries using slit and pinhole imaging coupled to area backlighting and as close as 150 ps to peak compression. We will focus in particular on comparisons of the in-flight shell thicknesses and ablation front scale lengths between low- and high-adiabat implosions, and the perturbations on areal density seeded both by time dependent drive asymmetries and by the membranes used to hold the capsule within the hohlraum in indirect drive ICF targets. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Computationally efficient real-time interpolation algorithm for non-uniform sampled biosignals
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
Ice friction: Role of non-uniform frictional heating and ice premelting.
Persson, B N J
2015-12-14
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.
Size Distribution Imaging by Non-Uniform Oscillating-Gradient Spin Echo (NOGSE) MRI
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
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.
Investigation of non-uniform airflow signal oscillation during high frequency chest compression
Sohn, Kiwon; Warwick, Warren J; Lee, Yong W; Lee, Jongwon; Holte, James E
2005-01-01
Background High frequency chest compression (HFCC) is a useful and popular therapy for clearing bronchial airways of excessive or thicker mucus. Our observation of respiratory airflow of a subject during use of HFCC showed the airflow oscillation by HFCC was strongly influenced by the nonlinearity of the respiratory system. We used a computational model-based approach to analyse the respiratory airflow during use of HFCC. Methods The computational model, which is based on previous physiological studies and represented by an electrical circuit analogue, was used for simulation of in vivo protocol that shows the nonlinearity of the respiratory system. Besides, airflow was measured during use of HFCC. We compared the simulation results to either the measured data or the previous research, to understand and explain the observations. Results and discussion We could observe two important phenomena during respiration pertaining to the airflow signal oscillation generated by HFCC. The amplitudes of HFCC airflow signals varied depending on spontaneous airflow signals. We used the simulation results to investigate how the nonlinearity of airway resistance, lung capacitance, and inertance of air characterized the respiratory airflow. The simulation results indicated that lung capacitance or the inertance of air is also not a factor in the non-uniformity of HFCC airflow signals. Although not perfect, our circuit analogue model allows us to effectively simulate the nonlinear characteristics of the respiratory system. Conclusion We found that the amplitudes of HFCC airflow signals behave as a function of spontaneous airflow signals. This is due to the nonlinearity of the respiratory system, particularly variations in airway resistance. PMID:15904523
Topographic viscous fingering: fluid-fluid displacement in a channel of non-uniform gap width.
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
Chen, Jui-Sheng; Liu, Chen-Wuing
2004-08-01
A reactive fluid circulating within a porous medium can dissolve minerals with which it is out of equilibrium and modify the porosity and permeability. The positive feedback between fluid transport and mineral dissolution causes complex reaction front morphologies such as fingers or wormholes. This study presents a numerical model to investigate reaction front instability, temporal aquifer porosity, and species concentration evolution during reactive transport in a homogeneous porous medium with two small, initially local non-uniformities. Simulation results indicate that a stable planar front develops for a small upstream pressure gradient while the growth of two non-uniformities becomes unstable for a large upstream pressure gradient. Moreover, the unstable reaction front may be either double- or single-finger in shape. Reaction front shape selection depends on the spacing of the two local non-uniformities and the upstream pressure gradients. A behavior diagram is constructed to identify a planar, single- or double-front morphology. The critical non-uniformities spacing at which a reaction front begins to merge into a single-finger decreases with increasing upstream pressure gradient.
Advanced GF(3^{2}) nonbinary LDPC coded modulation with non-uniform 9-QAM outperforming star 8-QAM.
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(3^{2}) 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(2^{3}) nonbinary LDPC coded 9-QAM scheme outperforms nonbinary LDPC coded uniform 8-QAM by at least 0.8dB.
Quantum efficiency of energy transfers in non-uniformly doped crystals of Er, Yb: LiNbO3
NASA Astrophysics Data System (ADS)
Nalbantov, N. N.; Stroganova, E. V.; Galutskiy, V. V.
2016-08-01
Spatial and temporal distribution of quantum efficiency of energy transfers in crystals of lithium niobate with non-uniform concentration profiles of Er3+ and Yb3+ ions has been studied for the cases of Yb3+-Er3+ Foerster transfer and radiative decay of upper energy levels of erbium ions (green and red luminescence).
Advanced GF(3^{2}) nonbinary LDPC coded modulation with non-uniform 9-QAM outperforming star 8-QAM.
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(3^{2}) 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(2^{3}) nonbinary LDPC coded 9-QAM scheme outperforms nonbinary LDPC coded uniform 8-QAM by at least 0.8dB. PMID:27410549
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.
NASA Astrophysics Data System (ADS)
Gutiérrez, Rebeca; Just, Dieter
2013-10-01
The METEOSAT Third Generation (MTG) Programme will provide the geostationary platforms for operational meteorological data acquisitions over Europe in 2018-2030. The Flexible Combined Imager (FCI) instrument is one of the MTG imager instruments and has a heritage from SEVIRI flown on the current METEOSAT Second Generation (MSG) satellites. It is a radiometer providing measurements in 16 spectral bands with a full Earth coverage every 10 minutes. For the Level 2 processing of FCI datasets the measurements have to be re-sampled on a constant reference grid in a geostationary projection - this process is referred to as rectification. The use of a three-axis stabilised platform and the scanning scheme applied to the FCI make rectification in MTG more challenging than in the MSG/SEVIRI case. Classical interpolation formulas assume a uniform sampling spacing of the measurements. However, non-uniform sampling may occur in the FCI sampling acquisition due to platform dynamics, micro-vibrations, thermo-elastic focal plane and optical distortions. In such a case, classical methods can cause significant rectification errors and interpolation algorithms, which can cope with non-uniform sampling, are required. This paper analyses the effect of non-uniform sampling in the FCI rectification process and aims to select and assess suitable resampling algorithms for the FCI L1 processing chain. Several techniques tailored to non-uniform resampling have been implemented. Performances of both uniform and non-uniform interpolation algorithms have been evaluated and compared using simulated FCI-like data samples. The analysis has been done for a nominal and a worst-case sample acquisition scenario. The presentation will show the results of our simulations with respect to the MTG requirements.
Managing tradeoffs in geoengineering through optimal choice of non-uniform radiative forcing
NASA Astrophysics Data System (ADS)
MacMartin, D. G.; Keith, D.; Kravitz, B.; Caldeira, K.
2012-12-01
reduced to a single "global thermostat"The trade-off between minimizing the global-rms normalized temperature and precipitation changes, and minimizing the worst-case change over any grid-cell, both expressed in number of standard deviations of inter-annual variability. Curves are plotted for uniform and non-uniform solar insolation reduction (SIR).
TH-A-BRF-11: Image Intensity Non-Uniformities Between MRI Simulation and Diagnostic MRI
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
Reducing seed dependent variability of non-uniformly sampled multidimensional NMR data.
Mobli, Mehdi
2015-07-01
The application of NMR spectroscopy to study the structure, dynamics and function of macromolecules requires the acquisition of several multidimensional spectra. The one-dimensional NMR time-response from the spectrometer is extended to additional dimensions by introducing incremented delays in the experiment that cause oscillation of the signal along "indirect" dimensions. For a given dimension the delay is incremented at twice the rate of the maximum frequency (Nyquist rate). To achieve high-resolution requires acquisition of long data records sampled at the Nyquist rate. This is typically a prohibitive step due to time constraints, resulting in sub-optimal data records to the detriment of subsequent analyses. The multidimensional NMR spectrum itself is typically sparse, and it has been shown that in such cases it is possible to use non-Fourier methods to reconstruct a high-resolution multidimensional spectrum from a random subset of non-uniformly sampled (NUS) data. For a given acquisition time, NUS has the potential to improve the sensitivity and resolution of a multidimensional spectrum, compared to traditional uniform sampling. The improvements in sensitivity and/or resolution achieved by NUS are heavily dependent on the distribution of points in the random subset acquired. Typically, random points are selected from a probability density function (PDF) weighted according to the NMR signal envelope. In extreme cases as little as 1% of the data is subsampled. The heavy under-sampling can result in poor reproducibility, i.e. when two experiments are carried out where the same number of random samples is selected from the same PDF but using different random seeds. Here, a jittered sampling approach is introduced that is shown to improve random seed dependent reproducibility of multidimensional spectra generated from NUS data, compared to commonly applied NUS methods. It is shown that this is achieved due to the low variability of the inherent sensitivity of the
Reducing seed dependent variability of non-uniformly sampled multidimensional NMR data
NASA Astrophysics Data System (ADS)
Mobli, Mehdi
2015-07-01
The application of NMR spectroscopy to study the structure, dynamics and function of macromolecules requires the acquisition of several multidimensional spectra. The one-dimensional NMR time-response from the spectrometer is extended to additional dimensions by introducing incremented delays in the experiment that cause oscillation of the signal along "indirect" dimensions. For a given dimension the delay is incremented at twice the rate of the maximum frequency (Nyquist rate). To achieve high-resolution requires acquisition of long data records sampled at the Nyquist rate. This is typically a prohibitive step due to time constraints, resulting in sub-optimal data records to the detriment of subsequent analyses. The multidimensional NMR spectrum itself is typically sparse, and it has been shown that in such cases it is possible to use non-Fourier methods to reconstruct a high-resolution multidimensional spectrum from a random subset of non-uniformly sampled (NUS) data. For a given acquisition time, NUS has the potential to improve the sensitivity and resolution of a multidimensional spectrum, compared to traditional uniform sampling. The improvements in sensitivity and/or resolution achieved by NUS are heavily dependent on the distribution of points in the random subset acquired. Typically, random points are selected from a probability density function (PDF) weighted according to the NMR signal envelope. In extreme cases as little as 1% of the data is subsampled. The heavy under-sampling can result in poor reproducibility, i.e. when two experiments are carried out where the same number of random samples is selected from the same PDF but using different random seeds. Here, a jittered sampling approach is introduced that is shown to improve random seed dependent reproducibility of multidimensional spectra generated from NUS data, compared to commonly applied NUS methods. It is shown that this is achieved due to the low variability of the inherent sensitivity of the
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.
Grain velocity of bedload movement in an armored non-uniform mobile bed
NASA Astrophysics Data System (ADS)
Liu, C.
2015-12-01
The velocity of bedload particles, which directly reflects the interaction between flow and sediment, is one of the important parameters to predict sediment transport rate, is also one of the fundamental problems for sediment transport. Many excellent works have been accomplished in this filed. However, the existing researches are mostly based on the artificial fixed bed, few moveable bed studies are focus on uniform sediment bed, these boundary conditions are different from a real river. In this research, an experiment on non-uniform sediment with an armored, moveable bed were carried out in a flume, the range of bed material is from 0.2mm to 20mm. With a special hanging glass and illumination system, the motion particles in the bed were clearly shoot on top of the flume by a video camera, avoiding the interference of waves at the flow surface. The speed of the camera is 50 frames per second. About 7000 unique coordinates of moving particles were determined from 3000 frames of successive pictures, the particle velocity of longitudinal and crosswise directions were obtained from the coordinates. The results show that, the probability density distribution of grain velocities of both directions are similar to that in the uniform sediment, which have an exponent decay trend, whereas the value of cross velocity of particles is clearly greater than that in the uniform sediment condition. Negative particle velocity was recognized in the experiment, it is shown that these negative may occur at two conditions, one is the backflow of fine particles behind the coarser particles, and the other is a state of movement change, such as a particle from static state to motion or vice versa. Furthermore, the particle movement was strongly affected by the arrangement of local coarse particles. The influence of coarser particles to the movement of fine particles also identified by two opposite effects, one is the acceleration effects in a 'tunnel' between pair of series particles, the
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
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
The Complexity of Leveraging University Program Change
ERIC Educational Resources Information Center
Crow, Gary M.; Arnold, Noelle Witherspoon; Reed, Cynthia J.; Shoho, Alan R.
2012-01-01
This article identifies four elements of complexity that influence how university educational leadership programs can leverage program change: faculty reward systems, faculty governance, institutional resources, and state-level influence on leadership preparation. Following the discussion of the elements of complexity, the article provides a…
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.
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.
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.
Shibata, T; Koga, S; Terasaki, R; Inoue, T; Dairaku, M; Kashiwagi, M; Taniguchi, M; Tobari, H; Tsuchida, K; Umeda, N; Watanabe, K; Hatayama, A
2012-02-01
Spatially non-uniform electron energy distribution function (EEDF) in an arc driven negative ion source (JAEA 10A negative ion source: 10 A NIS) is calculated numerically by a three-dimensional Monte Carlo kinetic model for electrons to understand spatial distribution of plasma production (such as atomic and ionic hydrogen (H(0)∕H(+)) production) in source chamber. The local EEDFs were directly calculated from electron orbits including electromagnetic effects and elastic∕inelastic collision forces. From the EEDF, spatial distributions of H(0)∕H(+) production rate were obtained. The results suggest that spatial non-uniformity of H(0)∕H(+) productions is enhanced by high energy component of EEDF.
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.
NASA Astrophysics Data System (ADS)
Cetkin, Erdal; Oliani, Alessandro
2015-07-01
Here, we show that the peak temperature on a non-uniformly heated domain can be decreased by embedding a high-conductivity insert in it. The trunk of the high-conductivity insert is in contact with a heat sink. The heat is generated non-uniformly throughout the domain or concentrated in a square spot of length scale 0.1 L0, where L0 is the length scale of the non-uniformly heated domain. Peak and average temperatures are affected by the volume fraction of the high-conductivity material and by the shape of the high-conductivity pathways. This paper uncovers how varying the shape of the symmetric and asymmetric high-conductivity trees affects the overall thermal conductance of the heat generating domain. The tree-shaped high-conductivity inserts tend to grow toward where the heat generation is concentrated in order to minimize the peak temperature, i.e., in order to minimize the resistances to the heat flow. This behaviour of high-conductivity trees is alike with the root growth of the plants and trees. They also tend to grow towards sunlight, and their roots tend to grow towards water and nutrients. This paper uncovers the similarity between biological trees and high-conductivity trees, which is that trees should grow asymmetrically when the boundary conditions are non-uniform. We show here even though all the trees have the same objectives (minimum flow resistance), their shape should not be the same because of the variation in boundary conditions. To sum up, this paper shows that there is a high-conductivity tree design corresponding to minimum peak temperature with fixed constraints and conditions. This result is in accord with the constructal law which states that there should be an optimal design for a given set of conditions and constraints, and this design should be morphed in order to ensure minimum flow resistances as conditions and constraints change.
An, Ran; Massa, Katherine
2014-01-01
AC Faradaic reactions have been reported as a mechanism inducing non-ideal phenomena such as flow reversal and cell deformation in electrokinetic microfluidic systems. Prior published work described experiments in parallel electrode arrays below the electrode charging frequency (fc), the frequency for electrical double layer charging at the electrode. However, 2D spatially non-uniform AC electric fields are required for applications such as in plane AC electroosmosis, AC electrothermal pumps, and dielectrophoresis. Many microscale experimental applications utilize AC frequencies around or above fc. In this work, a pH sensitive fluorescein sodium salt dye was used to detect [H+] as an indicator of Faradaic reactions in aqueous solutions within non-uniform AC electric fields. Comparison experiments with (a) parallel (2D uniform fields) electrodes and (b) organic media were employed to deduce the electrode charging mechanism at 5 kHz (1.5fc). Time dependency analysis illustrated that Faradaic reactions exist above the theoretically predicted electrode charging frequency. Spatial analysis showed [H+] varied spatially due to electric field non-uniformities and local pH changed at length scales greater than 50 μm away from the electrode surface. Thus, non-uniform AC fields yielded spatially varied pH gradients as a direct consequence of ion path length differences while uniform fields did not yield pH gradients; the latter is consistent with prior published data. Frequency dependence was examined from 5 kHz to 12 kHz at 5.5 Vpp potential, and voltage dependency was explored from 3.5 to 7.5 Vpp at 5 kHz. Results suggest that Faradaic reactions can still proceed within electrochemical systems in the absence of well-established electrical double layers. This work also illustrates that in microfluidic systems, spatial medium variations must be considered as a function of experiment time, initial medium conditions, electric signal potential, frequency, and spatial
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.
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.
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
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
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.
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.
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.
Chen, Changhua; Xiao, Renzhen; Sun, Jun; Song, Zhimin; Huo, Shaofei; Bai, Xianchen; Shi, Yanchao; Liu, Guozhi
2013-11-15
This paper provides a fresh insight into the effect of non-uniform slow wave structure (SWS) used in a relativistic backward wave oscillator (RBWO) with a resonant reflector. Compared with the uniform SWS, the reflection coefficient of the non-uniform SWS is higher, leading to a lower modulating electric field in the resonant reflector and a larger distance to maximize the modulation current. Moreover, for both types of RBWOs, stronger standing-wave field takes place at the rear part of the SWS. In addition, besides Cerenkov effects, the energy conversion process in the RBWO strongly depends on transit time effects. Thus, the matching condition between the distributions of harmonic current and standing wave field provides a profound influence on the beam-wave interaction. In the non-uniform RBWO, the region with a stronger standing wave field corresponds to a higher fundamental harmonic current distribution. Particle-in-cell simulations show that with a diode voltage of 1.02 MV and beam current of 13.2 kA, a microwave power of 4 GW has been obtained, compared to that of 3 GW in the uniform RBWO.
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).
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
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
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
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.
Venturini, Marco
2007-06-29
Use of a one-dimensional model of longitudinal space-charge(SC) impedance has been proposed for studying the microbunchinginstability in single-pass delivery systems relevant for the nextgeneration of FELs. For beams with uniform transverse density andcircular cross-section of radius r_b the SC impedance can be expressed ina handy analytical form, making this model particularly convenient. Inthis report we show how with an appropriate choice of r_b one can usethis as an effective-beam model to approximate beams with non-axissymmetric and non-uniform transverse densities.
NASA Astrophysics Data System (ADS)
Semkin, A. O.; Sharangovich, S. N.
2016-08-01
In this work the theoretical model of two-dimensional Bragg diffraction of quasimonochromatic light beams on amplitude- and phase- inhomogeneous holographic photonic PDLC structures under the impact of spatially non-uniform electric field is proposed. The selfconsistent solutions for the light diffraction on PDLC structure with uniform amplitude and quasi-quadratic profiles are obtained for the case of influence of linearly varying electric field. The possibility to compensate the PDLC structure response inhomogeneity by the impact of non-unifrom external field is shown.
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.
Qian, Shizhi; Joo, Sang W; Ai, Ye; Cheney, Marcos A; Hou, Wensheng
2009-01-15
The electrokinetic ionic-current rectification in a conical nanopore with linearly varying surface-charge distributions is studied theoretically by using a continuum model composed of a coupled system of the Nernst-Planck equations for the ionic-concentration field and the Poisson equation for the electric potential in the electrolyte solution. The numerical analysis includes the electrochemistry inside reservoirs connected to the nanopore, neglected in previous studies, and more precise accounts of the ionic current are provided. The surface-charge distribution, especially near the tip of the nanopore, significantly affects the ionic enrichment and depletion, which, in turn, influence the resulting ionic current and the rectification. It is shown that non-uniform surface-charge distribution can reverse the direction, or sense, of the rectification. Further insights into the ionic-current rectification are provided by discussing the intriguing details of the electric potential and ionic-concentration fields, leading to the rectification. Rationale for future studies on ionic-current rectification, associated with other non-uniform surface-charge distributions and electroosmotic convection for example, is discussed.
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.
Nowik-Boltyk, P; Dzyapko, O; Demidov, V E; Berloff, N G; Demokritov, S O
2012-01-01
A gas of magnons in magnetic films differs from all other known systems demonstrating Bose-Einstein condensation (BEC), since it possesses two energetically degenerate lowest-energy quantum states with non-zero wave vectors ±k(BEC). Therefore, BEC in this system results in a spontaneously formed two-component Bose-Einstein condensate described by a linear combination of two spatially non-uniform wave-functions ∝exp(±ik(BEC)z), while condensates found in other physical systems are characterized by spatially uniform wave-functions. Here we report a study of BEC of magnons with sub-micrometer spatial resolution. We experimentally confirm the existence of the two wave-functions and show that their interference results in a non-uniform ground state of the condensate with the density oscillating in space. Additionally, we observe stable topological defects in the condensate. By comparing the experimental results with predictions of a theoretical model based on the Ginzburg-Landau equation, we identify these defects as quantized vortices.
Nowik-Boltyk, P.; Dzyapko, O.; Demidov, V. E.; Berloff, N. G.; Demokritov, S. O.
2012-01-01
A gas of magnons in magnetic films differs from all other known systems demonstrating Bose-Einstein condensation (BEC), since it possesses two energetically degenerate lowest-energy quantum states with non-zero wave vectors ±kBEC. Therefore, BEC in this system results in a spontaneously formed two-component Bose-Einstein condensate described by a linear combination of two spatially non-uniform wave-functions ∝exp(±ikBECz), while condensates found in other physical systems are characterized by spatially uniform wave-functions. Here we report a study of BEC of magnons with sub-micrometer spatial resolution. We experimentally confirm the existence of the two wave-functions and show that their interference results in a non-uniform ground state of the condensate with the density oscillating in space. Additionally, we observe stable topological defects in the condensate. By comparing the experimental results with predictions of a theoretical model based on the Ginzburg-Landau equation, we identify these defects as quantized vortices. PMID:22761990
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.
Tian, Pengyi; Tao, Dashuai; Yin, Wei; Zhang, Xiangjun; Meng, Yonggang; Tian, Yu
2016-01-01
Comprehension of stick-slip motion is very important for understanding tribological principles. The transition from creep-dominated to inertia-dominated stick-slip as the increase of sliding velocity has been described by researchers. However, the associated micro-contact behavior during this transition has not been fully disclosed yet. In this study, we investigated the stick-slip behaviors of two polymethyl methacrylate blocks actively modulated from the creep-dominated to inertia-dominated dynamics through a non-uniform loading along the interface by slightly tilting the angle of the two blocks. Increasing the tilt angle increases the critical transition velocity from creep-dominated to inertia-dominated stick-slip behaviors. Results from finite element simulation disclosed that a positive tilt angle led to a higher normal stress and a higher temperature on blocks at the opposite side of the crack initiating edge, which enhanced the creep of asperities during sliding friction. Acoustic emission (AE) during the stick-slip has also been measured, which is closely related to the different rupture modes regulated by the distribution of the ratio of shear to normal stress along the sliding interface. This study provided a more comprehensive understanding of the effect of tilted non-uniform loading on the local stress ratio, the local temperature, and the stick-slip behaviors.
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).
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
NASA Astrophysics Data System (ADS)
Jing, Ze; Yong, Huadong; Zhou, Youhe
2016-10-01
In this paper, the anisotropic flux avalanche processes in thin square-shaped type-II superconducting films are numerically investigated by solving the coupled nonlinear Maxwell’s equations and the thermal diffusion equations. Influences of the non-uniformities and intrinsic critical current density anisotropies originate from the manufacturing process are considered in the simulation. In addition, we also studied the effect of the extrinsic anisotropy induced by the in-plane magnetic field. The results demonstrate that the non-uniformities and anisotropies of the critical current density play significant roles in the flux avalanche process of the thin film superconductors. Slight anisotropy (either intrinsic or extrinsic) can dramatically change the propagation direction of avalanches in the superconducting film, which is consistent with the experimental results. Simulations on the thin square-shaped isotropic superconducting films show that the threshold magnetic field for the flux avalanches increases with the angle between the applied field and the superconducting film-plane. In addition, the flux avalanche patterns change with the angular variation of the in-plane component of external magnetic field. When the in-plane magnetic field component is along the diagonal lines of the superconducting square, symmetric flux avalanche penetration patterns occur to the film.
NASA Astrophysics Data System (ADS)
Chan, Poh Kam; Oikawa, Shun-ichi; Kosaka, Wataru
2016-08-01
We have solved the Heisenberg equation of motion for the time evolution of the position and momentum operators for a non-relativistic spinless charged particle in the presence of a weakly non-uniform electric and magnetic field. It is shown that the drift velocity operator obtained in this study agrees with the classical counterpart, and that, using the time dependent operators, the variances in position and momentum grow with time. The expansion rate of variance in position and momentum are dependent on the magnetic gradient scale length, however, independent of the electric gradient scale length. In the presence of a weakly non-uniform electric and magnetic field, the theoretical expansion rates of variance expansion are in good agreement with the numerical analysis. It is analytically shown that the variance in position reaches the square of the interparticle separation, which is the characteristic time much shorter than the proton collision time of plasma fusion. After this time, the wavefunctions of the neighboring particles would overlap, as a result, the conventional classical analysis may lose its validity. The broad distribution of individual particle in space means that their Coulomb interactions with other particles become weaker than that expected in classical mechanics.
Tian, Pengyi; Tao, Dashuai; Yin, Wei; Zhang, Xiangjun; Meng, Yonggang; Tian, Yu
2016-01-01
Comprehension of stick-slip motion is very important for understanding tribological principles. The transition from creep-dominated to inertia-dominated stick-slip as the increase of sliding velocity has been described by researchers. However, the associated micro-contact behavior during this transition has not been fully disclosed yet. In this study, we investigated the stick-slip behaviors of two polymethyl methacrylate blocks actively modulated from the creep-dominated to inertia-dominated dynamics through a non-uniform loading along the interface by slightly tilting the angle of the two blocks. Increasing the tilt angle increases the critical transition velocity from creep-dominated to inertia-dominated stick-slip behaviors. Results from finite element simulation disclosed that a positive tilt angle led to a higher normal stress and a higher temperature on blocks at the opposite side of the crack initiating edge, which enhanced the creep of asperities during sliding friction. Acoustic emission (AE) during the stick-slip has also been measured, which is closely related to the different rupture modes regulated by the distribution of the ratio of shear to normal stress along the sliding interface. This study provided a more comprehensive understanding of the effect of tilted non-uniform loading on the local stress ratio, the local temperature, and the stick-slip behaviors. PMID:27641908
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.
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.
Tian, Pengyi; Tao, Dashuai; Yin, Wei; Zhang, Xiangjun; Meng, Yonggang; Tian, Yu
2016-01-01
Comprehension of stick-slip motion is very important for understanding tribological principles. The transition from creep-dominated to inertia-dominated stick-slip as the increase of sliding velocity has been described by researchers. However, the associated micro-contact behavior during this transition has not been fully disclosed yet. In this study, we investigated the stick-slip behaviors of two polymethyl methacrylate blocks actively modulated from the creep-dominated to inertia-dominated dynamics through a non-uniform loading along the interface by slightly tilting the angle of the two blocks. Increasing the tilt angle increases the critical transition velocity from creep-dominated to inertia-dominated stick-slip behaviors. Results from finite element simulation disclosed that a positive tilt angle led to a higher normal stress and a higher temperature on blocks at the opposite side of the crack initiating edge, which enhanced the creep of asperities during sliding friction. Acoustic emission (AE) during the stick-slip has also been measured, which is closely related to the different rupture modes regulated by the distribution of the ratio of shear to normal stress along the sliding interface. This study provided a more comprehensive understanding of the effect of tilted non-uniform loading on the local stress ratio, the local temperature, and the stick-slip behaviors. PMID:27641908
NASA Astrophysics Data System (ADS)
Tian, Pengyi; Tao, Dashuai; Yin, Wei; Zhang, Xiangjun; Meng, Yonggang; Tian, Yu
2016-09-01
Comprehension of stick-slip motion is very important for understanding tribological principles. The transition from creep-dominated to inertia-dominated stick-slip as the increase of sliding velocity has been described by researchers. However, the associated micro-contact behavior during this transition has not been fully disclosed yet. In this study, we investigated the stick-slip behaviors of two polymethyl methacrylate blocks actively modulated from the creep-dominated to inertia-dominated dynamics through a non-uniform loading along the interface by slightly tilting the angle of the two blocks. Increasing the tilt angle increases the critical transition velocity from creep-dominated to inertia-dominated stick-slip behaviors. Results from finite element simulation disclosed that a positive tilt angle led to a higher normal stress and a higher temperature on blocks at the opposite side of the crack initiating edge, which enhanced the creep of asperities during sliding friction. Acoustic emission (AE) during the stick-slip has also been measured, which is closely related to the different rupture modes regulated by the distribution of the ratio of shear to normal stress along the sliding interface. This study provided a more comprehensive understanding of the effect of tilted non-uniform loading on the local stress ratio, the local temperature, and the stick-slip behaviors.
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
NASA Astrophysics Data System (ADS)
Shintaku, Hirofumi; Kobayashi, Takayuki; Zusho, Kazuki; Kotera, Hidetoshi; Kawano, Satoyuki
2013-11-01
In this study, we have demonstrated the fabrication of a microbeam array (MBA) with various thicknesses and investigated the suitability it for an acoustic sensor with wide-range frequency selectivity. For this, an MBA composed of 64 beams, with thicknesses varying from 2.99-142 µm, was fabricated by using single gray-scale lithography and a thick negative photoresist. The vibration of the beams in air was measured using a laser Doppler vibrometer; the resonant frequencies of the beams were measured to be from 11.5 to 290 kHz. Lastly, the frequency range of the MBA with non-uniform thickness was 10.9 times that of the MBA with uniform thickness.
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.
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.
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.
Otake, H; Yukihiro, M; Fukushima, Y; Imai, T; Hosono, K; Hatori, N; Watanabe, N; Hirano, T; Inoue, T; Takahashi, M; Ban, R; Endo, K
1996-03-01
Simultaneous transmission emission protocol (STEP), developed for the non-uniform attenuation correction of single photon emission computed tomography (SPECT) was evaluated using the cardiac phantom prepared with and without a myocardial wall defect. Emission computed tomography (ECT) of the cardiac phantom using 201Tl was acquired. Transmission data (TCT) were taken using a line source of 99mTc. Myocardial images with STEP method were superior in the homogeneity of intramyocardial radioactivity and spatial resolution to the conventional SPECT images. This is an excellent method because of the accurate matching position between TCT and ECT images and shortening the examination time by simultaneous data acquisition. It would be clinically useful for diagnosing various myocardial diseases.
NASA Astrophysics Data System (ADS)
Kalisch, Michael; Ansorg, Marcus
2016-11-01
In this paper, we describe in detail a scheme for the construction of highly accurate numerical solutions to Einstein's field equations in five and six spacetime dimensions, corresponding to non-uniform black strings. The scheme consists of a sophistically adapted multi-domain pseudo-spectral method which incorporates a detailed understanding of the solution's behavior at the domain boundaries and at critical points. In particular, the five-dimensional case is exceedingly demanding, as logarithmic terms appear which need to be treated with special care. Our scheme resolves these issues, and permits the investigation of unprecedentedly strong deformations of the black string horizon. As a consequence, we are able to study in detail the critical regime in phase diagrams displaying characteristic thermodynamic quantities such as mass and entropy. Our results show typical spiral curves in such diagrams which provide strong support for previous numerical works.
García-Zambrana, Antonio; Castillo-Vázquez, Beatriz; Castillo-Vázquez, Carmen
2010-09-13
A new upper bound on the capacity of power- and bandwidth-constrained optical wireless links using selection transmit diversity over exponential atmospheric turbulence channels with intensity modulation and direct detection is derived when non-uniform on-off keying (OOK) formats are used. In this strong turbulence free-space optical (FSO) scenario, average capacity is investigated subject to an average optical power constraint and not only to an average electrical power constraint when the transmit diversity technique assumed is based on the selection of the optical path with a greater value of irradiance. Simulation results for the mutual information are further demonstrated to confirm the analytical results for different diversity orders.
NASA Astrophysics Data System (ADS)
Jentschura, Ulrich D.
2007-03-01
Two-photon decay rates in simple atoms such as hydrogen-like systems represent rather interesting fundamental problems in atomic physics. The sum of the energies of the two emitted photons has to fulfil an energy conservation condition, the decay takes place via intermediate virtual states, and the total decay rate is obtained after an integration over the energy of one of the emitted photons. Here, we investigate cases with a virtual state having an intermediate energy between the initial and the final states of the decay process, and we show that due to non-uniform convergence, only a careful treatment of the singularities infinitesimally displaced from the photon integration contour leads to consistent and convergent results.
Zhang, Yuning; Du, Xiaoze
2015-09-01
Predictions of the propagation of the acoustic waves in bubbly liquids is of great importance for bubble dynamics and related applications (e.g. sonochemistry, sonochemical reactor design, biomedical engineering). In the present paper, an approach for modeling the propagation of the acoustic waves in dilute bubbly liquids is proposed through considering the non-uniform pressure field outside the bubbles. This approach is validated through comparing with available experimental data in the literature. Comparing with the previous models, our approach mainly improves the predictions of the attenuation of acoustic waves in the regions with large kR0 (k is the wave number and R0 is the equilibrium bubble radius). Stability of the oscillating bubbles under acoustic excitation are also quantitatively discussed based on the analytical solution.
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.
1RXS J180834.7+101041 is a new cataclysmic variable with non-uniform disc
NASA Astrophysics Data System (ADS)
Yakin, D. G.; Suleimanov, V. F.; Shimansky, V. V.; Borisov, N. V.; Bikmaev, I. F.; Sakhibullin, N. A.
2010-11-01
Results of photometric and spectroscopic investigations of the recently discovered disc cataclysmic variable star 1RXS J180834.7+101041 are presented. Emission spectra of the system show broad double peaked hydrogen and helium emission lines. Doppler maps for the hydrogen lines demonstrate strongly non-uniform emissivity distribution in the disc, similar to that found in IP Peg. It means that the system is a new cataclysmic variable with a spiral density wave in the disc. Masses of the components (MWD = 0.8+/-0.22 Msolar and MRD = 0.14+/-0.02 Msolar), and the orbit inclination (i = 78°+/- 1.°5) were estimated using the various well-known relations for cataclysmic variables.
NASA Astrophysics Data System (ADS)
Cailing, Wang; Renke, Kang; Zhuji, Jin; Dongming, Guo
2010-12-01
Based on the Preston equation, the mathematical model of the material removal rate (MRR), aiming at a line-orbit chemical mechanical polisher, is established. The MRR and the material removal non-uniformity (MRNU) are numerically calculated by MATLAB, and the effects of the reciprocating parameters on the MRR and the MRNU are discussed. It is shown that the smaller the inclination angle and the larger the amplitude, the higher the MRR and the lower the MRNU. The reciprocating speed of the carrier plays a minor role to improve the MRR and decrease the MRNU. The results provide a guide for the design of a polisher and the determination of a process in line-orbit chemical mechanical polishing.
NASA Astrophysics Data System (ADS)
Brock, L. M.
A S A BASIS for obtaining insight into both plastic flow in terms of dislocation motion and dynamic crack extension, the general problem of non-uniform motion of largely arbitrary dislocation distributions by climb and by glide along non-planar paths is considered. An exact solution is found in two forms: one form, vectorial in nature, shows that the essential distribution and path properties are contained in a symmetric tensor. The other form, consisting of complex functions, shows that the solution involves the inner product of the displacement discontinuity vector and complex vectors whose components normal and tangential to the path contour are related through tangent angle derivatives. Both forms illustrate that the solution has two components, one arising from the velocity discontinuity along the contour, the other arising from the displacement discontinuity at its edge and the edge speed.
NASA Astrophysics Data System (ADS)
Cao, Yanpeng; Tisse, Christel-Loic
2013-06-01
In uncooled LWIR microbolometer imaging systems, temperature fluctuations of FPA (Focal Plane Array) as well as lens and mechanical components placed along the optical path result in thermal drift and spatial non-uniformity. These non-idealities generate undesirable FPN (Fixed-Pattern-Noise) that is difficult to remove using traditional, individual shutterless and TEC-less (Thermo-Electric Cooling) techniques. In this paper we introduce a novel single-image based processing approach that marries the benefits of both statistical scene-based and calibration-based NUC algorithms, without relying neither on extra temperature reference nor accurate motion estimation, to compensate the resulting temperature-dependent non-uniformities. Our method includes two subsequent image processing steps. Firstly, an empirical behavioral model is derived by calibrations to characterize the spatio-temporal response of the microbolometric FPA to environmental and scene temperature fluctuations. Secondly, we experimentally establish that the FPN component caused by the optics creates a spatio-temporally continuous, low frequency, low-magnitude variation of the image intensity. We propose to make use of this property and learn a prior on the spatial distribution of natural image gradients to infer the correction function for the entire image. The performance and robustness of the proposed temperature-adaptive NUC method are demonstrated by showing results obtained from a 640×512 pixels uncooled LWIR microbolometer imaging system operating over a broad range of temperature and with rapid environmental temperature changes (i.e. from -5°C to 65°C within 10 minutes).
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.
A model to non-uniform Ni Schottky contact on SiC annealed at elevated temperatures
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.
Federal Register 2010, 2011, 2012, 2013, 2014
2010-05-13
... Federal Student Aid; Leveraging Educational Assistance Partnership, Special Leveraging Educational... Leveraging Educational Assistance Partnership (LEAP), Special Leveraging Educational Assistance Partnership... in providing aid to students with substantial financial need to help them pay for their...
Leveraging the Shapley Lectures
NASA Astrophysics Data System (ADS)
Howard, S.
1998-05-01
The Shapley Lectureships are both an honor and a privilege. The program has long provided the non-specialist a rare glimpse of the latest result of astronomical investigations. Shapley Lecturers carry the banner for the most interesting of all the sciences. They share the beauty and strength of astronomy by representing the discipline to non-specialists. It is important that we contribute what we can to this program. One might benefit from the frequent travel of most astronomers. Most research trips are now covered by grant money, by university money, and by Government money. Leverage this travel. For example, many meetings are held near places with small colleges. Consider sending a Shapley brochure to the science departments before your trip. Such trips may often be used to elicit a Shapley visit. Advertise the program. When we talk about astronomy to others we help all of us to keep this science alive. I will share the results of my Shapley Visits made in the last four years while traveling for NASA and NSF.
Leveraging the national cyberinfrastructure for biomedical research
LeDuc, Richard; Vaughn, Matthew; Fonner, John M; Sullivan, Michael; Williams, James G; Blood, Philip D; Taylor, James; Barnett, William
2014-01-01
In the USA, the national cyberinfrastructure refers to a system of research supercomputer and other IT facilities and the high speed networks that connect them. These resources have been heavily leveraged by scientists in disciplines such as high energy physics, astronomy, and climatology, but until recently they have been little used by biomedical researchers. We suggest that many of the ‘Big Data’ challenges facing the medical informatics community can be efficiently handled using national-scale cyberinfrastructure. Resources such as the Extreme Science and Discovery Environment, the Open Science Grid, and Internet2 provide economical and proven infrastructures for Big Data challenges, but these resources can be difficult to approach. Specialized web portals, support centers, and virtual organizations can be constructed on these resources to meet defined computational challenges, specifically for genomics. We provide examples of how this has been done in basic biology as an illustration for the biomedical informatics community. PMID:23964072
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
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
NASA Astrophysics Data System (ADS)
Van Reeth, T.; Tkachenko, A.; Aerts, C.; Pápics, P. I.; Degroote, P.; Debosscher, J.; Zwintz, K.; Bloemen, S.; De Smedt, K.; Hrudkova, M.; Raskin, G.; Van Winckel, H.
2015-02-01
Context. The analysis of stellar oscillations is one of the most reliable ways to probe stellar interiors. Recent space missions such as Kepler have provided us with an opportunity to study these oscillations with unprecedented detail. For many multi-periodic pulsators such as γ Doradus stars, this led to the detection of dozens to hundreds of oscillation frequencies that could not be found from ground-based observations. Aims: We aim to detect non-uniform period spacings in the Fourier spectra of a sample of γ Doradus stars observed by Kepler. Such detection is complicated by both the large number of significant frequencies in the space photometry and by overlapping non-equidistant rotationally split multiplets. Methods: Guided by theoretical properties of gravity-mode oscillation of γ Doradus stars, we developed a period-spacing detection method and applied it to Kepler observations of a few stars, after having tested the performance from simulations. Results: The application of the technique resulted in the clear detection of non-uniform period spacing series for three out of the five treated Kepler targets. Disadvantages of the technique are also discussed, and include the disability to distinguish between different values of the spherical degree and azimuthal order of the oscillation modes without additional theoretical modelling. Conclusions: Despite the shortcomings, the method is shown to allow solid detections of period spacings for γ Doradus stars, which will allow future asteroseismic analyses of these stars. Based on data gathered with the NASA Discovery mission Kepler and the HERMES spectrograph, which is installed at the Mercator Telescope, operated on the island of La Palma by the Flemish Community at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, and supported by the Fund for Scientific Research of Flanders (FWO), Belgium, the Research Council of KU Leuven, Belgium, the Fonds National de la
NASA Astrophysics Data System (ADS)
Riihimaki, C. A.; Anderson, R. S.; Safran, E. B.
2001-12-01
The Laramide ranges and the intervening sedimentary basins stretch across ~300,000 km2 of Wyoming, Colorado, Montana, Utah, and South Dakota, forming some of the most dramatic mountain landscapes of the North American continental interior. Interpretations of the late Cenozoic geophysical and climatic history of the entire western U. S. hinge on assumptions about Laramide landscape evolution, and yet this evolution is ill-understood. The confusion stems from conflicting interpretations of non-uniform erosion rates across the Laramide region, which previous researchers have tried to correlate directly with regional episodes of tectonic or climatic forcing. Erosion in this region is largely driven by downcutting of a fluvial network linking a series of easily eroded sedimentary basins across relatively resistant crystalline cores. It is therefore likely that even a simple climatic or geophysical forcing event may result in a complex temporal and spatial pattern of erosion. We use a two-dimensional numerical model of stream power-based fluvial erosion and the associated flexural isostatic response to test two proposed mechanisms for extensive late Cenozoic exhumation in the Laramide region: regional uplift - for example, uplift driven by the passage of the subducted Farallon slab (e.g., Mitrovica et al., 1989) - which drives changes in stream gradient distributions; and climatic cooling and aridification, which drive changes in the frequency and intensity of floods (e.g., Molnar and England, 1990). We find that four factors dominate the spatial and temporal pattern of sub-regional landscape evolution: 1) the time since the forcing was imposed; 2) the along-drainage distance from baselevel to a basin or range; 3) the distribution of relatively resistant bedrock within the region; and 4) the regionalized pattern of isostatic response to sequential basin exhumation. In particular, we show that each type of forcing produces a predictable, non-uniform pattern of erosion
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
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Hsu, Wei-Lun; Harvie, Dalton J E; Davidson, Malcolm R; Jeong, Helen; Goldys, Ewa M; Inglis, David W
2014-09-21
The simultaneous concentration gradient focusing and separation of proteins in a silica nanofluidic channel of various geometries is investigated experimentally and theoretically. Previous modelling of a similar device [Inglis et al., Angew. Chem. Int. Ed., 2011, 50, 7546] assumed a uniform velocity profile along the length of the nanochannel. Using detailed numerical analysis incorporating charge regulation and viscoelectric effects, we show that in reality the varying axial electric field and varying electric double layer thickness caused by the concentration gradient, induce a highly non-uniform velocity profile, fundamentally altering the protein trapping mechanism: the direction of the local electroosmotic flow reverses and two local vortices are formed near the centreline of the nanochannel at the low salt concentration end, enhancing trapping efficiency. Simulation results for yellow/red fluorescent protein R-PE concentration enhancement, peak focusing position and peak focusing width are in good agreement with experimental measurements, validating the model. The predicted separation of yellow/red (R-PE) from green (Dyl-Strep) fluorescent proteins mimics that from a previous experiment [Inglis et al., Angew. Chem. Int. Ed., 2011, 50, 7546] conducted in a slightly different geometry. The results will inform the design of new class of matrix-free particle focusing and separation devices. PMID:25027204
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.
Imai, Kuniharu; Ikeda, Mitsuru; Enchi, Yukihiro; Niimi, Takanaga
2010-01-01
By using the CT images obtained by subtracting two CT images acquired under the same conditions and slice locations, we have devised a method for detecting streak artifacts in non-uniform regions and only radiological noise components in CT images. A chest phantom was scanned using 16- and 64-multidetector row helical CT scanners with various mAs values at 120kVp. The upper lung slice image was employed as a target image for evaluating the streak artifacts and radiological noise. One hundred parallel line segments with a length of 80 pixels were placed on the subtracted CT image, and the largest CT value in each CT value profile was employed as a feature variable of the streak artifacts; these feature variables were analyzed with the extreme value theory (Gumbel distribution). To detect only the radiological noise, all CT values contained in the 100 line profile were plotted on normal probability paper and the standard deviation was estimated from the inclination of its fitted line for the CT value plots. The two detection methods devised in this study were able to evaluate the streak artifacts and radiological noise in the CT images with high accuracy.
Log-linear non-uniform association models for agreement between two ratings on an ordinal scale.
Valet, Fabien; Guinot, Christiane; Mary, Jean Yves
2007-02-10
In agreement studies, when objects are rated independently by two raters (or twice by the same rater), an association between their ratings on two categories arises, reflecting the distinguishability of these two categories for these raters. When ratings are performed on an ordinal scale, this association between ratings on two categories increases when the distance between these categories increases on the ordinal scale. Goodman's log-linear models derived for the analysis of agreement between two raters on an ordinal scale assume that distinguishabilities between adjacent categories are either constant, or a priori fixed. Log-non-linear models that allow variations of the distinguishabilities between adjacent categories along the scale, may lead to difficulties in parameter estimation. This paper describes a new class of log-linear non-uniform association models. These models extend the log-linear uniform association model by allowing variations of distinguishability between adjacent categories (along the scale). These new models are used to analyse ordinal agreement between dermatologists when assessing the severity of different cutaneous signs of ageing on women faces.
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.
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
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.
NASA Astrophysics Data System (ADS)
Rossi, Alessandro; Diani, Marco; Corsini, Giovanni
2009-09-01
In this work we analyze the problem of the ghosting artifacts coming out from non-uniformity correction (NUC) in infrared focal-plane array (IRFPA) imaging systems. We have employed a well-established least mean square (LMS) - based NUC technique which was first introduced by D.A. Scribner. Slow global motion and edges in the scene are the main responsible of the generated ghosting artifacts that can be very damaging especially in target detection and tracking applications. To mitigate the effects of ghosting we propose to replace the linear spatial filter of the analyzed NUC scheme with a non-linear one, known in the literature as bilateral filter, which is able to preserve edges. The proposed technique has been evaluated over an infrared (IR) image sequence with simulated fixed-pattern noise (FPN). A detailed analysis of the results has shown the advantages of the novel deghosting method in terms of accuracy of the calibration and quality of the corrected frames.
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.
NASA Astrophysics Data System (ADS)
Wiggins, Brenden; Tupitsyn, Eugene; Bhattacharya, Pijush; Rowe, Emmanuel; Lukosi, Eric; Chvala, Ondrej; Burger, Arnold; Stowe, Ashley
2013-09-01
Impurity analysis and compositional distribution studies have been conducted on a crystal of LiInSe2, a compound semiconductor which recently has been shown to respond to ionizing radiation. IR microscopy and laser induced breakdown spectroscopy (LIBS) revealed the presence of inclusions within the crystal lattice. These precipitates were revealed to be alkali and alkaline earth elemental impurities with non-uniform spatial distribution in the crystal. LIBS compositional maps correlate the presence of these impurities with visual color differences in the crystal as well as a significant shift of the band gap. Further, LIBS revealed variation in the ratio of I-III-VI2 elemental constituents throughout the crystal. Analysis of compositional variation and impurities will aid in discerning optimal synthesis and crystal growth parameters to maximize the mobility-lifetime product and charge collection efficiency in the LiInSe2 crystal. Preliminary charge trapping calculations have also been conducted with the Monte Carlo N-particle eXtended (MCNPx) package indicating preferential trapping of holes during irradiation with thermal neutrons.
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.
Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties.
Mehdizadeh Dehkordi, Arash; Bhattacharya, Sriparna; Darroudi, Taghi; Zeng, Xiaoyu; Alshareef, Husam N; Tritt, Terry M
2015-08-15
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.
FANNING OUT OF THE SOLAR f-MODE IN THE PRESENCE OF NON-UNIFORM MAGNETIC FIELDS?
Singh, Nishant K.; Brandenburg, Axel; Rheinhardt, Matthias
2014-11-01
We show that in the presence of a magnetic field that is varying harmonically in space, the fundamental mode, or f-mode, in a stratified layer is altered in such a way that it fans out in the diagnostic kω diagram, with mode power also within the fan. In our simulations, the surface is defined by a temperature and density jump in a piecewise isothermal layer. Unlike our previous work (Singh et al. 2014), where a uniform magnetic field was considered, here we employ a non-uniform magnetic field together with hydromagnetic turbulence at length scales much smaller than those of the magnetic field. The expansion of the f-mode is stronger for fields confined to the layer below the surface. In some of those cases, the kω diagram also reveals a new class of low-frequency vertical stripes at multiples of twice the horizontal wavenumber of the background magnetic field. We argue that the study of the f-mode expansion might be a new and sensitive tool to determine subsurface magnetic fields with azimuthal or other horizontal periodicity.
NASA Astrophysics Data System (ADS)
Price-Whelan, Adrian M.; Agueros, M. A.; Fournier, A.; Street, R.; Ofek, E.; Levitan, D. B.; PTF Collaboration
2013-01-01
Many current photometric, time-domain surveys are driven by specific goals such as searches for supernovae or transiting exoplanets, or studies of stellar variability. These goals in turn set the cadence with which individual fields are re-imaged. In the case of the Palomar Transient Factory (PTF), several such sub-surveys are being conducted in parallel, leading to extremely non-uniform sampling over the survey's nearly 20,000 sq. deg. footprint. While the typical 7.26 sq. deg. PTF field has been imaged 20 times in R-band, ~2300 sq. deg. have been observed more than 100 times. We use the existing PTF data 6.4x107 light curves) to study the trade-off that occurs when searching for microlensing events when one has access to a large survey footprint with irregular sampling. To examine the probability that microlensing events can be recovered in these data, we also test previous statistics used on uniformly sampled data to identify variables and transients. We find that one such statistic, the von Neumann ratio, performs best for identifying simulated microlensing events. We develop a selection method using this statistic and apply it to data from all PTF fields with >100 observations to uncover a number of interesting candidate events. This work can help constrain all-sky event rate predictions and tests microlensing signal recovery in large datasets, both of which will be useful to future wide-field, time-domain surveys such as the LSST.
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.
Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties.
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
NASA Astrophysics Data System (ADS)
Ai, Yu-hua; Zhou, Huai-chun
2005-02-01
For visualizing non-uniform absorbing, emitting, non-scattering, axisymmetric sooting flames, because conventional two-color emission methods are no longer suitable, a three-color emission method for the simultaneous estimation of temperature and soot volume fraction distributions in these flames is studied in this paper. The spectral radiation intensities at wavelengths of red, green, and blue, which may be derived from color flame images, are simulated for the inverse analysis. Then the simultaneous estimation is carried out from the spectral radiation intensities by using a Newton-type iteration algorithm and the least-squares method. In this method, a factor is used to balance the wide variation of spectral radiation intensities due to both the wide ranges of temperature and wavelength of the flame radiation. The results indicate that the three-color method is suited for the reconstruction of flame structures with single or double peaks with small difference between the peak and valley. For a double-peaked flame structure with larger peak and valley difference, reasonable result can be obtained just when the mean square deviations of measurement data are small, for example, not more than 0.01.
Investigation of beam non-uniformity after cross-beam energy transfer in a gas filled hohlraum
NASA Astrophysics Data System (ADS)
Schneider, M. B.; Hinkel, D. E.; Rosen, M. D.; Callahan, D. A.; Michel, P. A.; Moore, A. S.; Moody, J. D.
2015-11-01
Control of hotspot symmetry in an ignition capsule imploded by the x-ray drive in a high gas-filled cylindrical hohlraum at the NIF currently requires cross-beam energy transfer (CBET) from the outer beams to the inner beams. CBET occurs in the central region of the laser entrance hole (LEH) where the laser beams overlap. Linear gain models applied to individual rays indicate that CBET is not uniform across the beam profile, producing a non-uniform spatial distribution on the beams that varies in time. This changing spatial distribution could introduce asymmetries in the x-ray drive applied to the ignition capsule and should be quantified. We are investigating the effects of CBET using the Quartraum experimental platform. This platform uses an LEH-only target designed to isolate the effect of CBET on the spatial-intensity distribution of the inner beams by minimizing the effect of absorption and backscatter. A time resolved image of two inner beams is captured on a high Z witness plate. Experimental results showing how the beam's x-ray foot print on the witness plate changes as a function of Δλ will be shown and compared to models.
Shahvaran, Zahra; Kazemi, Kamran; Helfroush, Mohammad Sadegh; Jafarian, Nassim; Noorizadeh, Negar
2012-08-15
Noise and intensity non-uniformity are causing major difficulties in magnetic resonance (MR) image segmentation. This paper introduces a variational level set approach for simultaneous MR image segmentation and intensity non-uniformity correction. The proposed energy functional is based on local Gaussian intensity fitting with local means and variances. Furthermore, the proposed model utilizes Markov random fields to model the spatial correlation between neighboring pixels/voxels. The improvements achieved with our method are demonstrated by brain segmentation experiments with simulated and real magnetic resonance images with different noise and bias level. In particular, it is superior in term of accuracy as compared to LGDF and FSL-FAST methods.
Shahvaran, Zahra; Kazemi, Kamran; Helfroush, Mohammad Sadegh; Jafarian, Nassim
2012-01-01
This paper represents a new region-based active contour model that can be used to segment images with intensity non-uniformity and high-level noise. The main idea of our proposed method is to use Gaussian distributions with different means and variances with incorporation of intensity non-uniformity model for image segmentation. In order to integrate the spatial information between neighboring pixels in our proposed method, we use Markov Random Field. Our experiments on synthetic images and cerebral magnetic resonance images show the advantages of the proposed method over state-of-art methods, i.e. local Gaussian distribution fitting.
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.
NASA Astrophysics Data System (ADS)
Aziz, Tariq; Kumar, Manoj
2001-11-01
We present a three-point finite-difference method based on non-uniform mesh for a class of singular two-point boundary value problem(x[alpha]y')'=f(x,y)y(0)=A, y(1)=B, 0[less-than-or-equals, slant][alpha]<1.We show that the method, based on non-uniform mesh, provides O(h4)-convergent approximations. This method is illustrated by two numerical examples, one is linear and the other is non-linear.
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
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
NASA Astrophysics Data System (ADS)
Shemesh, Noam; Álvarez, Gonzalo A.; Frydman, Lucio
2013-12-01
Noninvasive measurements of microstructure in materials, cells, and in biological tissues, constitute a unique capability of gradient-assisted NMR. Diffusion-diffraction MR approaches pioneered by Callaghan demonstrated this ability; Oscillating-Gradient Spin-Echo (OGSE) methodologies tackle the demanding gradient amplitudes required for observing diffraction patterns by utilizing constant-frequency oscillating gradient pairs that probe the diffusion spectrum, D(ω). Here we present a new class of diffusion MR experiments, termed Non-uniform Oscillating-Gradient Spin-Echo (NOGSE), which dynamically probe multiple frequencies of the diffusion spectral density at once, thus affording direct microstructural information on the compartment's dimension. The NOGSE methodology applies N constant-amplitude gradient oscillations; N - 1 of these oscillations are spaced by a characteristic time x, followed by a single gradient oscillation characterized by a time y, such that the diffusion dynamics is probed while keeping (N - 1)x + y ≡ TNOGSE constant. These constant-time, fixed-gradient-amplitude, multi-frequency attributes render NOGSE particularly useful for probing small compartment dimensions with relatively weak gradients - alleviating difficulties associated with probing D(ω) frequency-by-frequency or with varying relaxation weightings, as in other diffusion-monitoring experiments. Analytical descriptions of the NOGSE signal are given, and the sequence's ability to extract small compartment sizes with a sensitivity towards length to the sixth power, is demonstrated using a microstructural phantom. Excellent agreement between theory and experiments was evidenced even upon applying weak gradient amplitudes. An MR imaging version of NOGSE was also implemented in ex vivo pig spinal cords and mouse brains, affording maps based on compartment sizes. The effects of size distributions on NOGSE are also briefly analyzed.
Falla, D; Farina, D
2008-11-01
The aim of the study was to investigate the adaptations of motor unit discharge rate and additional motor unit recruitment in different regions of the upper trapezius muscle during sustained contraction. Intramuscular EMG signals were recorded from three locations (cranial, middle, and caudal) within the upper trapezius of eleven healthy men during 60-s static shoulder abduction at 25% of the maximal force. Surface EMG signals were recorded concurrently with a 10 x 5 electrode grid. Fifty-one (cranial location), 39 (middle), and 19 (caudal) motor units were identified from the intramuscular EMG signals. Motor unit discharge rates at the beginning of the contraction were greater in the caudal than in the other two locations (cranial: 16.5 +/- 3.4 pps; n = 28, middle: 16.2 +/- 3.4 pps; n = 32, caudal: 19.6 +/- 3.1 pps; n = 13; P < 0.05). Because the decrease in discharge rate over time was larger for the caudal location, at the end of the contraction the discharge rates were comparable at all locations (cranial: 15.7 +/- 3.3 pps; n = 28, middle: 14.9 +/- 2.3 pps; n = 32, caudal: 15.8 +/- 3.6 pps; n = 13). Additional motor unit recruitment was observed in all locations but more frequently in the caudal region (19 motor units recruited after the beginning of the contraction vs. only 4 in each of the other two locations). The mean position of the distribution of surface EMG amplitude over the grid moved by 1.4 +/- 0.7 mm (P < 0.001) in the cranial direction at the end with respect to the beginning of the contraction. The results showed that the neural drive received by the upper trapezius depends on the muscle region, which may indicate non-uniform descending drive to the motor neuron pool.
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.
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.
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…
Grismer, Mark E
2005-01-01
Although constructed wetland treatment systems have been used in a variety of applications, uncertainty in adequately determining flow conditions or hydraulic residence times ("hydraulic efficiencies") and degradation model parameters remains a problem with their design. Breakthrough or impulse-type tracer studies in constructed wetlands often result in residence-time distributions exhibiting long skewed "tails" suggesting multiple flow channels or perhaps unrealistically large dispersion factors. A fractional-flow analysis is developed here to quantify possible flow non-uniformity in a subsurface-flow constructed wetland and is then used to assess the effects of non-uniformity and degradation model parameter variability on constituent (for example, chemical oxygen demand) removal. A model application to tracer data developed previously demonstrates how flow non-uniformity alone can account for significant "tailing" and can be related to even moderate estimated dispersion numbers. From the analysis, it is evident that flow non-uniformity is of greater concern than decay parameter uncertainty, and that, from a constructed wetland design and operation perspective, every effort should be made to ensure relative flow uniformity across the constructed wetland. PMID:16381152
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.
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.
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.
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
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.
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.
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.
Alcusa-Sáez, E P; Díez, A; González-Herráez, M; Andrés, M V
2015-03-23
The time-resolved acousto-optic technique demonstrated recently to be a very useful method for the analysis of fiber axial non-uniformities, able to detect variations of fiber diameter in the nanometric scale with a spatial resolution of few cm. An edge interrogation approach is proposed to improve further the performance of this technique. The detection of subnanometer fiber diameter changes or sub-ppm changes of the core refractive index is demonstrated.
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
NASA Astrophysics Data System (ADS)
Montes Bajo, M.; Dunn, G.; Stephen, A.; Khalid, Ata; Cumming, D. R. S.; Oxley, C. H.; Glover, J.; Kuball, M.
2013-03-01
When biased in the negative differential resistance regime, electroluminescence (EL) is emitted from planar GaAs heterostructure Gunn diodes. This EL is due to the recombination of electrons in the device channel with holes that are generated by impact ionisation when the Gunn domains reach the anode edge. The EL forms non-uniform patterns whose intensity shows short-range intensity variations in the direction parallel to the contacts and decreases along the device channel towards the cathode. This paper employs Monte Carlo models, in conjunction with the experimental data, to analyse these non-uniform EL patterns and to study the carrier dynamics responsible for them. It is found that the short-range lateral (i.e., parallel to the device contacts) EL patterns are probably due to non-uniformities in the doping of the anode contact, illustrating the usefulness of EL analysis on the detection of such inhomogeneities. The overall decreasing EL intensity towards the anode is also discussed in terms of the interaction of holes with the time-dependent electric field due to the transit of the Gunn domains. Due to their lower relative mobility and the low electric field outside of the Gunn domain, freshly generated holes remain close to the anode until the arrival of a new domain accelerates them towards the cathode. When the average over the transit of several Gunn domains is considered, this results in a higher hole density, and hence a higher EL intensity, next to the anode.
NASA Astrophysics Data System (ADS)
Zhang, Wei; Nie, Hong-Bin; Hou, Qing-Yu; Cao, Yi-Ming
2009-11-01
Regarding the appearance of fixed pattern noise (FPN) in the IR images of an IR observation system introduced by errors in assembly, environment, etc. Non-Uniformity Correction (NUC) is an important technique for IRFPA. Because the real radiation response of pixels in the given dynamic range is nonlinear and the existence of 1/f noise, especially the high temperature scaling point changes the thermal balance of the IR observation system, using the traditional linear approximate method (temperature scaling method) is hard to obtain the perfect corrective images. On the other hand, because of Scene-Based Non-Uniformity Correction (SBNUC) does not rely on specialized hardware, SBNUC is very attractive alternative to radiometric calibration for infrared sensors, thereinto, Constant Statistics (CS) is the best known approach, but it lies on the scene content and has intimate correlation with the sample quantity. So, in this paper, we present a novel approach which inherits the rapidity of temperature scaling method and also consider the astringency of CS, using variable-step constant statistics (VSCS) as second non-uniformity correction in the spatial and time domains of infrared images to eliminate the residual fixed pattern noise which resulted from the theoretical and methodological errors of temperature scaling method. The experimental result for the real infrared images data is a solution which effectively eliminates the residual fixed pattern noise, and at the same time, it proved the effectiveness of this algorithm.
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
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.
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.
NASA Astrophysics Data System (ADS)
Qi, Zumin; Zhang, Jun; Zhong, Huihuang; Zhu, Danni; Qiu, Yongfeng
2014-01-01
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.
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.
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.
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
12 CFR 567.8 - Leverage ratio.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 12 Banks and Banking 5 2010-01-01 2010-01-01 false Leverage ratio. 567.8 Section 567.8 Banks and... § 567.8 Leverage ratio. (a) The minimum leverage capital requirement for a savings association assigned... associations not meeting the conditions set forth in paragraph (a) of this section, the minimum...
12 CFR 567.8 - Leverage ratio.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 12 Banks and Banking 6 2013-01-01 2012-01-01 true Leverage ratio. 567.8 Section 567.8 Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements § 567.8 Leverage ratio. (a) The minimum leverage capital requirement for a savings association assigned a composite rating of 1, as defined in...
12 CFR 167.8 - Leverage ratio.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 12 Banks and Banking 1 2013-01-01 2013-01-01 false Leverage ratio. 167.8 Section 167.8 Banks and Banking COMPTROLLER OF THE CURRENCY, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements § 167.8 Leverage ratio. (a) The minimum leverage capital requirement for a Federal savings association assigned a composite rating of 1, as...
12 CFR 167.8 - Leverage ratio.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 12 Banks and Banking 1 2014-01-01 2014-01-01 false Leverage ratio. 167.8 Section 167.8 Banks and Banking COMPTROLLER OF THE CURRENCY, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements § 167.8 Leverage ratio. (a) The minimum leverage capital requirement for a Federal savings association assigned a composite rating of 1, as...
12 CFR 167.8 - Leverage ratio.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 12 Banks and Banking 1 2012-01-01 2012-01-01 false Leverage ratio. 167.8 Section 167.8 Banks and Banking COMPTROLLER OF THE CURRENCY, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements § 167.8 Leverage ratio. (a) The minimum leverage capital requirement for a Federal savings association assigned a composite rating of 1, as...
12 CFR 390.467 - Leverage ratio.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 12 Banks and Banking 5 2014-01-01 2014-01-01 false Leverage ratio. 390.467 Section 390.467 Banks and Banking FEDERAL DEPOSIT INSURANCE CORPORATION REGULATIONS AND STATEMENTS OF GENERAL POLICY REGULATIONS TRANSFERRED FROM THE OFFICE OF THRIFT SUPERVISION Capital § 390.467 Leverage ratio. (a) The minimum leverage capital requirement for a...
Local overfitting control via leverages.
Monari, Gaétan; Dreyfus, Gérard
2002-06-01
We present a novel approach to dealing with overfitting in black box models. It is based on the leverages of the samples, that is, on the influence that each observation has on the parameters of the model. Since overfitting is the consequence of the model specializing on specific data points during training, we present a selection method for nonlinear models based on the estimation of leverages and confidence intervals. It allows both the selection among various models of equivalent complexities corresponding to different minima of the cost function (e.g., neural nets with the same number of hidden units) and the selection among models having different complexities (e.g., neural nets with different numbers of hidden units). A complete model selection methodology is derived.
17 CFR 31.22 - Prohibited trading in leverage contracts.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 17 Commodity and Securities Exchanges 1 2010-04-01 2010-04-01 false Prohibited trading in leverage... LEVERAGE TRANSACTIONS § 31.22 Prohibited trading in leverage contracts. No futures commission merchant or... orders for any leverage contract....
17 CFR 31.6 - Registration of leverage commodities.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 17 Commodity and Securities Exchanges 1 2010-04-01 2010-04-01 false Registration of leverage... LEVERAGE TRANSACTIONS § 31.6 Registration of leverage commodities. (a) Registration of leverage commodities. Each leverage commodity upon which a leverage contract is offered for sale or purchase or is sold...
7 CFR 4290.1130 - Leverage fees payable by RBIC.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 7 Agriculture 15 2010-01-01 2010-01-01 false Leverage fees payable by RBIC. 4290.1130 Section 4290...) PROGRAM Financial Assistance for RBICs (Leverage) General Information About Obtaining Leverage § 4290.1130 Leverage fees payable by RBIC. (a) Leverage fee. You must pay the Secretary a non-refundable leverage...
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.
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.
Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; De Geronimo, G.; Eger, J.; Emerick, A.; Fried, J.; Hossain, A.; Roy, U.; Salwen, C.; et al
2015-09-06
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 pixelmore » 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.« less
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.
2015-09-06
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 mm^{3} 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.
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.
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
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.
Technical Report of Accomplishments of the Weatherization Leveraging Partnership Project
Economic Opportunity Studies
2007-09-30
The Weatherization Leveraging Partnership Project was established to provide three types of technical assistance support to W.A.P. network organizations seeking to achieve the Weatherization Plus goal of expanding their non-federal resources. It provided: (1) Analysis that profiled W.A.P.-eligible household energy characteristics and finances for all in determining efficiency investment targets and goals; (2) Detailed information on leveraged partnerships linked from many sources and created a website with finding aids to meet the needs the network identified. There are five major market segments with related, but different, technical assistance needs; (3) Direct, sustained assistance in preparing strategies, analyses, and communications for a limited set of local network initiatives that were in early stages of initiating or changing their resource expansion strategies. The Project identified trends in the challenges that weatherizers initiatives encountered; it designed materials and tools, including the dynamic www.weatherizationplus.org website, to meet the continuing and the emerging needs.
Protein leverage and energy intake.
Gosby, A K; Conigrave, A D; Raubenheimer, D; Simpson, S J
2014-03-01
Increased energy intakes are contributing to overweight and obesity. Growing evidence supports the role of protein appetite in driving excess intake when dietary protein is diluted (the protein leverage hypothesis). Understanding the interactions between dietary macronutrient balance and nutrient-specific appetite systems will be required for designing dietary interventions that work with, rather than against, basic regulatory physiology. Data were collected from 38 published experimental trials measuring ad libitum intake in subjects confined to menus differing in macronutrient composition. Collectively, these trials encompassed considerable variation in percent protein (spanning 8-54% of total energy), carbohydrate (1.6-72%) and fat (11-66%). The data provide an opportunity to describe the individual and interactive effects of dietary protein, carbohydrate and fat on the control of total energy intake. Percent dietary protein was negatively associated with total energy intake (F = 6.9, P < 0.0001) irrespective of whether carbohydrate (F = 0, P = 0.7) or fat (F = 0, P = 0.5) were the diluents of protein. The analysis strongly supports a role for protein leverage in lean, overweight and obese humans. A better appreciation of the targets and regulatory priorities for protein, carbohydrate and fat intake will inform the design of effective and health-promoting weight loss diets, food labelling policies, food production systems and regulatory frameworks.
Leverage points in a computer model
NASA Astrophysics Data System (ADS)
Janošek, Michal
2016-06-01
This article is focused on the analysis of the leverage points (developed by D. Meadows) in a computer model. The goal is to find out if there is a possibility to find these points of leverage in a computer model (on the example of a predator-prey model) and to determine how the particular parameters, their ranges and monitored variables of the model are associated with the concept of leverage points.
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
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.
NASA Astrophysics Data System (ADS)
Amabili, M.; Pierandrei, R.; Frosali, G.
1997-09-01
The free vibrations of a circular plate having elastic constraints variable according to the angular co-ordinate are investigated. The non-uniform translational and rotational stiffness of the constraints are expanded in the Fourier series; it is assumed that the system presents a symmetry axis. The mode shapes are expanded in a Fourier-Bessel series by using the Rayleigh-Ritz method. The eigenfunctions of the free-edge circular plate vibrating in vacuum are assumed as admissible functions. This choice allows one to compute the potential energy of the plate using the kinetic energy of single modes of free-edge plates. The effect of the in-plane load is included and internal constraints are studied. By using the same technique, the free vibrations of a circular plate resting on an annular, non-uniform, Winkler foundation are investigated. Numerical results are given for the cases studied already, in order to validate the proposed method, and for bolted (or riveted) plates fixed by different numbers of bolts.
17 CFR 31.17 - Records of leverage transactions.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 17 Commodity and Securities Exchanges 1 2010-04-01 2010-04-01 false Records of leverage... LEVERAGE TRANSACTIONS § 31.17 Records of leverage transactions. (a) Each leverage transaction merchant receiving a leverage customer's order shall immediately upon receipt thereof prepare a written record...
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
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.
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
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.
NASA Astrophysics Data System (ADS)
Berger, Casey E.; Drut, Joaquín E.; Porter, William J.
2016-11-01
We present in detail two variants of the lattice Monte Carlo method aimed at tackling systems in external trapping potentials: a uniform-lattice approach with hard-wall boundary conditions, and a non-uniform Gauss-Hermite lattice approach. Using those two methods, we compute the ground-state energy and spatial density profile for systems of N = 4- 8 harmonically trapped fermions in one dimension. From the favorable comparison of both energies and density profiles (particularly in regions of low density), we conclude that the trapping potential is properly resolved by the hard-wall basis. Our work paves the way to higher dimensions and finite temperature analyses, as calculations with the hard-wall basis can be accelerated via fast Fourier transforms; the cost of unaccelerated methods is otherwise prohibitive due to the unfavorable scaling with system size. To illustrate this point, we show a brief performance comparison of accelerated versus unaccelerated methods across spatial dimensions.
Mobli, Mehdi; Stern, Alan S.; Bermel, Wolfgang; King, Glenn F.; Hoch, Jeffrey C.
2010-01-01
One of the stiffest challenges in structural studies of proteins using NMR is the assignment of sidechain resonances. Typically, a panel of lengthy 3D experiments are acquired in order to establish connectivities and resolve ambiguities due to overlap. We demonstrate that these experiments can be replaced by a single 4D experiment that is time-efficient, yields excellent resolution, and captures unique carbon-proton connectivity information. The approach is made practical by the use of non-uniform sampling in the three indirect time dimensions and maximum entropy reconstruction of the corresponding 3D frequency spectrum. This 4D method will facilitate automated resonance assignment procedures and it should be particularly beneficial for increasing throughput in NMR-based structural genomics initiatives. PMID:20299257
NASA Astrophysics Data System (ADS)
Mobli, Mehdi; Stern, Alan S.; Bermel, Wolfgang; King, Glenn F.; Hoch, Jeffrey C.
2010-05-01
One of the stiffest challenges in structural studies of proteins using NMR is the assignment of sidechain resonances. Typically, a panel of lengthy 3D experiments are acquired in order to establish connectivities and resolve ambiguities due to overlap. We demonstrate that these experiments can be replaced by a single 4D experiment that is time-efficient, yields excellent resolution, and captures unique carbon-proton connectivity information. The approach is made practical by the use of non-uniform sampling in the three indirect time dimensions and maximum entropy reconstruction of the corresponding 3D frequency spectrum. This 4D method will facilitate automated resonance assignment procedures and it should be particularly beneficial for increasing throughput in NMR-based structural genomics initiatives.
NASA Astrophysics Data System (ADS)
Haiming, Gu; Liyang, Pan; Peng, Zhu; Dong, Wu; Zhigang, Zhang; Jun, Xu
2010-10-01
In order to overcome the bit-to-bit interference of the traditional multi-level NAND type device, this paper firstly proposes a novel multi-bit non-uniform channel charge trapping memory (NUC-CTM) device with virtual-source NAND-type array architecture, which can effectively restrain the second-bit effect (SBE) and provide 3-bit per cell capability. Owing to the n- buffer region, the SBE induced threshold voltage window shift can be reduced to less than 400 mV and the minimum threshold voltage window between neighboring levels is larger than 750 mV for reliable 3-bit operation. A silicon-rich SiON is also investigated as a trapping layer to improve the retention reliability of the NUC-CTM.
NASA Astrophysics Data System (ADS)
Khabaz, Rahim
2013-11-01
A mathematical simulation approach based on the general purpose Monte Carlo N-particle transport code MCNP was developed to calculate the departure in reading of the neutron spectrometer instrument from that expected according to the inverse square law. The calculations were performed to evaluate the effects of beam divergence on the response of a 10 in. spherical device equipped with a long BF3 counter irradiated by 11 mono-energy neutron beams. The necessary geometry correction factor, because of non-uniform illumination, for the calibration of seven polyethylene spheres with several radionuclide neutron sources, i.e. Ra-Be, 241Am-Be, 241Am-B and Po-Be sources was also determined. In all calculations, the displacement of effective center from the geometric center of moderating spheres, when used as an instrument for neutron fluence measurement, was quantified.
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.
Non-uniform oxygen diffusion in epitaxial La0.7Sr0.3MnO3-δ film on SrTiO3 substrate
NASA Astrophysics Data System (ADS)
Nikolaenko, Yu M.; Artemov, A. N.; Medvedev, Yu V.; Efros, N. B.; Zhikharev, I. V.; Reshidova, I. Yu; Tikhii, A. A.; Kara-Murza, S. V.
2016-09-01
The diffusion mechanism of oxygen transport in the epitaxial La0.7Sr0.3MnO3-δ films was examined for different practically significant conditions of annealing. An indirect method based on the interrelation between the phase transition temperature and the oxygen index was used for stepwise monitoring of the oxygen content in the film. Using a serial procedure of film annealing at different temperatures, we have revealed the abnormal behavior of diffusion transport of oxygen. The analysis of experimental data using numerical simulations demonstrates non-uniformity of the diffusion coefficient across the film thickness. The nature of the spatial dependence of the diffusion coefficient is associated with the lattice distortions of the film material.
NASA Astrophysics Data System (ADS)
Rana, Vijay; Gill, Kamaljit; Rudin, Stephen; Bednarek, Daniel R.
2012-03-01
The current version of the real-time skin-dose-tracking system (DTS) we have developed assumes the exposure is contained within the collimated beam and is uniform except for inverse-square variation. This study investigates the significance of factors that contribute to beam non-uniformity such as the heel effect and backscatter from the patient to areas of the skin inside and outside the collimated beam. Dose-calibrated Gafchromic film (XR-RV3, ISP) was placed in the beam in the plane of the patient table at a position 15 cm tube-side of isocenter on a Toshiba Infinix C-Arm system. Separate exposures were made with the film in contact with a block of 20-cm solid water providing backscatter and with the film suspended in air without backscatter, both with and without the table in the beam. The film was scanned to obtain dose profiles and comparison of the profiles for the various conditions allowed a determination of field non-uniformity and backscatter contribution. With the solid-water phantom and with the collimator opened completely for the 20-cm mode, the dose profile decreased by about 40% on the anode side of the field. Backscatter falloff at the beam edge was about 10% from the center and extra-beam backscatter decreased slowly with distance from the field, being about 3% of the beam maximum at 6 cm from the edge. Determination of the magnitude of these factors will allow them to be included in the skin-dose-distribution calculation and should provide a more accurate determination of peak-skin dose for the DTS.
Poinapen, Danny; Brown, Daniel C W; Beeharry, Girish K
2013-09-15
Different factors (e.g., light, humidity, and temperature) including exposure to static magnetic fields (SMFs), referred here as critical factors, can significantly affect horticultural seed performance. However, the link between magnetic field parameters and other interdependent factors affecting seed viability is unclear. The importance of these critical factors affecting tomato (Solanum lycopersicum L.) var. MST/32 seed performance was assessed after performing several treatments based on a L9 (3(4)) (four factors at three levels) orthogonal array (OA) design. The variable factors in the design were magnetic flux density (R1=332.1±37.8mT; R2=108.7±26.9mT; and R3=50.6±10.5mT), exposure time (1, 2, and 24h), seed orientation (North polarity, South polarity, and control - no magnetic field), and relative humidity (RH) (7.0, 25.5, and 75.5%). After seed moisture content stabilisation at the different chosen RH, seeds were exposed in dark under laboratory conditions to several treatments based on the OA design before performance evaluation. Treatments not employing magnetic field exposure were used as controls. Results indicate that electrolyte leakage rate was reduced by a factor of 1.62 times during seed imbibition when non-uniform SMFs were employed. Higher germination (∼11.0%) was observed in magnetically-exposed seeds than in non-exposed ones, although seedlings emerging from SMF treatments did not show a consistent increase in biomass accumulation. The respective influence of the four critical factors tested on seed performance was ranked (in decreasing order) as seed orientation to external magnetic fields, magnetic field strength, RH, and exposure time. This study suggests a significant effect of non-uniform SMFs on seed performance with respect to RH, and more pronounced effects are observed during seed imbibition rather than during later developmental stages. PMID:23759543
Rana, Vijay; Gill, Kamaljit; Rudin, Stephen; Bednarek, Daniel R
2012-02-23
The current version of the real-time skin-dose-tracking system (DTS) we have developed assumes the exposure is contained within the collimated beam and is uniform except for inverse-square variation. This study investigates the significance of factors that contribute to beam non-uniformity such as the heel effect and backscatter from the patient to areas of the skin inside and outside the collimated beam. Dose-calibrated Gafchromic film (XR-RV3, ISP) was placed in the beam in the plane of the patient table at a position 15 cm tube-side of isocenter on a Toshiba Infinix C-Arm system. Separate exposures were made with the film in contact with a block of 20-cm solid water providing backscatter and with the film suspended in air without backscatter, both with and without the table in the beam. The film was scanned to obtain dose profiles and comparison of the profiles for the various conditions allowed a determination of field non-uniformity and backscatter contribution. With the solid-water phantom and with the collimator opened completely for the 20-cm mode, the dose profile decreased by about 40% on the anode side of the field. Backscatter falloff at the beam edge was about 10% from the center and extra-beam backscatter decreased slowly with distance from the field, being about 3% of the beam maximum at 6 cm from the edge. Determination of the magnitude of these factors will allow them to be included in the skin-dose-distribution calculation and should provide a more accurate determination of peak-skin dose for the DTS.
Financing drug discovery via dynamic leverage.
Montazerhodjat, Vahid; Frishkopf, John J; Lo, Andrew W
2016-03-01
We extend the megafund concept for funding drug discovery to enable dynamic leverage in which the portfolio of candidate therapeutic assets is predominantly financed initially by equity, and debt is introduced gradually as assets mature and begin generating cash flows. Leverage is adjusted so as to maintain an approximately constant level of default risk throughout the life of the fund. Numerical simulations show that applying dynamic leverage to a small portfolio of orphan drug candidates can boost the return on equity almost twofold compared with securitization with a static capital structure. Dynamic leverage can also add significant value to comparable all-equity-financed portfolios, enhancing the return on equity without jeopardizing debt performance or increasing risk to equity investors. PMID:26708982
Financing drug discovery via dynamic leverage.
Montazerhodjat, Vahid; Frishkopf, John J; Lo, Andrew W
2016-03-01
We extend the megafund concept for funding drug discovery to enable dynamic leverage in which the portfolio of candidate therapeutic assets is predominantly financed initially by equity, and debt is introduced gradually as assets mature and begin generating cash flows. Leverage is adjusted so as to maintain an approximately constant level of default risk throughout the life of the fund. Numerical simulations show that applying dynamic leverage to a small portfolio of orphan drug candidates can boost the return on equity almost twofold compared with securitization with a static capital structure. Dynamic leverage can also add significant value to comparable all-equity-financed portfolios, enhancing the return on equity without jeopardizing debt performance or increasing risk to equity investors.
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
Leveraging Failure in Design Research
ERIC Educational Resources Information Center
Lobato, Joanne; Walters, C. David; Hohensee, Charles; Gruver, John; Diamond, Jaime Marie
2015-01-01
Even in the resource-rich, more ideal conditions of many design-based classroom interventions, unexpected events can lead to disappointing results in student learning. However, if later iterations in a design research study are more successful, the previous failures can provide opportunities for comparisons to reveal subtle differences in…
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
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.
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).
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.
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
NASA Astrophysics Data System (ADS)
Lehujeur, Maximilien; Vergne, Jérôme; Maggi, Alessia; Schmittbuhl, Jean
2016-10-01
We developed and applied a method for ambient noise surface wave tomography that can deal with noise cross-correlation functions governed to first order by a non-uniform distribution of the ambient seismic noise sources. The method inverts the azimuthal distribution of noise sources that are assumed to be far from the network, together with the spatial variations of the phase and group velocities on an optimized irregular grid. Direct modeling of the two-sided noise correlation functions avoids dispersion curve picking on every station pair and minimizes analyst intervention. The method involves station pairs spaced by distances down to a fraction of a wavelength, thereby bringing additional information for tomography. After validating the method on synthetic data, we applied it to a set of long-term continuous waveforms acquired around the geothermal sites at Soultz-sous-Forêts and Rittershoffen (Northern Alsace, France). For networks with limited aperture, we show that taking the azimuthal variations of the noise energy into account has significant impact on the surface wave dispersion maps. We obtained regional phase and group velocity models in the 1-7 s period range, which is sensitive to the structures encompassing the geothermal reservoirs. The ambient noise in our dataset originates from two main directions, the northern Atlantic Ocean and the Mediterranean Sea, and is dominated by the first Rayleigh wave overtone in the 2 - 5 s period range.
Um, Ji-Yong; Kim, Yoon-Jee; Cho, Seong-Eun; Chae, Min-Kyun; Song, Jongkeun; Kim, Baehyung; Lee, Seunghun; Bang, Jihoon; Kim, Youngil; Cho, Kyungil; Kim, Byungsub; Sim, Jae-Yoon; Park, Hong-June
2014-12-01
To reduce the memory area, a two-stage RX beamformer (BF) chip with 64 channels is proposed for the ultrasound medical imaging with a 2D CMUT array. The chip retrieved successfully two B-mode phantom images with a steering angle from -45 (°) to +45 (°), the maximum delay range of 8 μs, and the delay resolution of 6.25 ns. An analog-digital hybrid BF (HBF) is chosen for the proposed chip to utilize the easy beamforming operation in the digital domain and also to reduce chip area by minimizing the number of ADCs. The chip consists of eight analog beamformers (ABF) for the 1st-stage and a digital beamformer (DBF) for the 2nd-stage. The two-stage architecture reduces the memory area of both ABF and DBF by around four times. The DBF circuit is divided into three steps to further reduce the digital FIFO memory area by around twice. Coupled with the non-uniform sampling scheme, the proposed two-stage HBF chip reduces the total memory area by around 40 times compared to the uniform-sampling single-stage BF chip. The chip fabricated in a 0.13- μm CMOS process occupies the area of 19.4 mm(2), and dissipates 1.14 W with the analog supply of 3.3 V and the digital supply of 1.2 V.
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.
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.
Musheev, Michael U; Kanoatov, Mirzo; Krylov, Sergey N
2013-05-29
Identical molecules move with identical velocities when placed in a uniform electric field within a uniform electrolyte. Here we report that homogeneous DNA does not obey this fundamental rule. While most DNA moves with similar velocities, a fraction of DNA moves with velocities that vary within a multiple-fold range. The size of this irregular fraction increases several orders of magnitude when exogenous counterions are added to DNA. The irregular fraction decreases several orders of magnitude when DNA counterions are removed by dialysis against deionized water in the presence of a strong electric field (0.6 kV/cm). Dialysis without the field is ineffective in decreasing the size of irregular fraction. These results suggest that (i) DNA can form very stable complexes with counterions, (ii) these complexes can be dissociated by an electric field, and (iii) the observed non-uniform velocity of DNA is caused by electric-field-induced slow dissociation of these stable complexes. Our findings help to better understand a fundamental property of DNA: its interaction with counterions. In addition, these findings suggest a practical way of making electromigration of DNA more uniform: removal of strongly bound DNA counterions by electro-dialysis against deionized water.
7 CFR 4290.1120 - General eligibility requirements for Leverage.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 7 Agriculture 15 2010-01-01 2010-01-01 false General eligibility requirements for Leverage. 4290... INVESTMENT COMPANY (âRBICâ) PROGRAM Financial Assistance for RBICs (Leverage) General Information About Obtaining Leverage § 4290.1120 General eligibility requirements for Leverage. To be eligible for...
17 CFR 31.8 - Cover of leverage contracts.
Code of Federal Regulations, 2011 CFR
2011-04-01
... bullion in the case of leverage contracts on bulk gold coins, bulk gold coins in the case of leverage contracts on gold bullion, silver bullion in the case of leverage contracts on bulk silver coins, bulk silver coins in the case of leverage contracts on silver bullion, one type of bulk gold coins...
17 CFR 31.15 - Reporting to leverage customers.
Code of Federal Regulations, 2010 CFR
2010-04-01
... customers. 31.15 Section 31.15 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION LEVERAGE TRANSACTIONS § 31.15 Reporting to leverage customers. Each leverage transaction merchant shall furnish in writing directly to each leverage customer: (a) Promptly upon the repurchase,...
Resources for International Partners
Learn about NCI's Center for Global Health, which facilitates global collaboration by leveraging research resources with U.S. government agencies, foreign governments, non-government organizations, and pharmaceutical and biotechnology companies.
17 CFR 31.10 - Repurchase and resale of leverage contracts by leverage transaction merchants.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 17 Commodity and Securities Exchanges 1 2010-04-01 2010-04-01 false Repurchase and resale of... Exchanges COMMODITY FUTURES TRADING COMMISSION LEVERAGE TRANSACTIONS § 31.10 Repurchase and resale of... time when such leverage transaction merchant is not offering to repurchase from any of its...
17 CFR 31.10 - Repurchase and resale of leverage contracts by leverage transaction merchants.
Code of Federal Regulations, 2011 CFR
2011-04-01
... 17 Commodity and Securities Exchanges 1 2011-04-01 2011-04-01 false Repurchase and resale of... Exchanges COMMODITY FUTURES TRADING COMMISSION LEVERAGE TRANSACTIONS § 31.10 Repurchase and resale of... time when such leverage transaction merchant is not offering to repurchase from any of its...
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.
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.
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.
Pandithevan, Ponnusamy
2015-02-01
In tissue engineering, the successful modeling of scaffold for the replacement of damaged body parts depends mainly on external geometry and internal architecture in order to avoid the adverse effects such as pain and lack of ability to transfer the load to the surrounding bone. Due to flexibility in controlling the parameters, layered manufacturing processes are widely used for the fabrication of bone tissue engineering scaffold with the given computer-aided design model. This article presents a squared distance minimization approach for weight optimization of non-uniform rational B-spline curve and surface to modify the geometry that exactly fits into the defect region automatically and thus to fabricate the scaffold specific to subject and site. The study showed that though the errors associated in the B-spline curve and surface were minimized by squared distance method than point distance method and tangent distance method, the errors could be minimized further in the rational B-spline curve and surface as the optimal weight could change the shape that desired for the defect site. In order to measure the efficacy of the present approach, the results were compared with point distance method and tangent distance method in optimizing the non-rational and rational B-spline curve and surface fitting for the defect site. The optimized geometry then allowed to construct the scaffold in fused deposition modeling system as an example. The result revealed that the squared distance-based weight optimization of the rational curve and surface in making the defect specific geometry best fits into the defect region than the other methods used.
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.
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.
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.
NASA Astrophysics Data System (ADS)
Price-Whelan, Adrian M.; Agüeros, Marcel A.; Fournier, Amanda P.; Street, Rachel; Ofek, Eran O.; Covey, Kevin R.; Levitan, David; Laher, Russ R.; Sesar, Branimir; Surace, Jason
2014-01-01
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 deg2 footprint. While the median 7.26 deg2 PTF field has been imaged ~40 times in the R band, ~2300 deg2 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 × 109 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.
Leveraging Sociocultural Theory to Create a Mentorship Program for Doctoral Students
ERIC Educational Resources Information Center
Crosslin, Matt; Wakefield, Jenny S.; Bennette, Phyllis; Black, James William, III
2013-01-01
This paper details a proposed doctoral student connections program that is based on sociocultural theory. It is designed to assist new students with starting their educational journey. This program is designed to leverage social interactions, peer mentorship, personal reflection, purposeful planning, and existing resources to assist students in…
ERIC Educational Resources Information Center
Hemp, Richard; Parish, Susan; Braddock, David, Ed.; Smith, Gary, Ed.
2001-01-01
This article discusses using existing state resources not currently used for matching purposes to leverage additional federal Medicaid funding for community services and supports for persons with mental retardation. A table is provided that lists state funds potentially available to match additional federal Medicaid funding. (Contains six…
Leveraging e-learning in medical education.
Lewis, Kadriye O; Cidon, Michal J; Seto, Teresa L; Chen, Haiqin; Mahan, John D
2014-07-01
e-Learning has become a popular medium for delivering instruction in medical education. This innovative method of teaching offers unique learning opportunities for medical trainees. The purpose of this article is to define the present state of e-learning in pediatrics and how to best leverage e-learning for educational effectiveness and change in medical education. Through addressing under-examined and neglected areas in implementation strategies for e-learning, its usefulness in medical education can be expanded. This study used a systematic database review of published studies in the field of e-learning in pediatric training between 2003 and 2013. The search was conducted using educational and health databases: Scopus, ERIC, PubMed, and search engines Google and Hakia. A total of 72 reference articles were suitable for analysis. This review is supplemented by the use of "e-Learning Design Screening Questions" to define e-learning design and development in 10 randomly selected articles. Data analysis used template-based coding themes and counting of the categories using descriptive statistics.Our search for pediatric e-learning (using Google and Hakia) resulted in six well-defined resources designed to support the professional development of doctors, residents, and medical students. The majority of studies focused on instructional effectiveness and satisfaction. There were few studies about e-learning development, implementation, and needs assessments used to identify the institutional and learners' needs. Reviewed studies used various study designs, measurement tools, instructional time, and materials for e-learning interventions. e-Learning is a viable solution for medical educators faced with many challenges, including (1) promoting self-directed learning, (2) providing flexible learning opportunities that would offer continuous (24h/day/7 days a week) availability for learners, and (3) engaging learners through collaborative learning communities to gain
Leveraging e-learning in medical education.
Lewis, Kadriye O; Cidon, Michal J; Seto, Teresa L; Chen, Haiqin; Mahan, John D
2014-07-01
e-Learning has become a popular medium for delivering instruction in medical education. This innovative method of teaching offers unique learning opportunities for medical trainees. The purpose of this article is to define the present state of e-learning in pediatrics and how to best leverage e-learning for educational effectiveness and change in medical education. Through addressing under-examined and neglected areas in implementation strategies for e-learning, its usefulness in medical education can be expanded. This study used a systematic database review of published studies in the field of e-learning in pediatric training between 2003 and 2013. The search was conducted using educational and health databases: Scopus, ERIC, PubMed, and search engines Google and Hakia. A total of 72 reference articles were suitable for analysis. This review is supplemented by the use of "e-Learning Design Screening Questions" to define e-learning design and development in 10 randomly selected articles. Data analysis used template-based coding themes and counting of the categories using descriptive statistics.Our search for pediatric e-learning (using Google and Hakia) resulted in six well-defined resources designed to support the professional development of doctors, residents, and medical students. The majority of studies focused on instructional effectiveness and satisfaction. There were few studies about e-learning development, implementation, and needs assessments used to identify the institutional and learners' needs. Reviewed studies used various study designs, measurement tools, instructional time, and materials for e-learning interventions. e-Learning is a viable solution for medical educators faced with many challenges, including (1) promoting self-directed learning, (2) providing flexible learning opportunities that would offer continuous (24h/day/7 days a week) availability for learners, and (3) engaging learners through collaborative learning communities to gain
NUCLEAR INCIDENT CAPABILITIES, KNOWLEDGE & ENABLER LEVERAGING
Kinney, J.; Newman, J.; Goodwyn, A.; Dewes, J.
2011-04-18
action. Much work needs to be accomplished to enhance nuclear preparedness and to substantially bolster and clarify the capacity to deploy competent resources. Until detailed plans are scripted, and personnel and other resources are postured, and exercised, IND specific planning remains an urgent need requiring attention and action. Although strategic guidance, policies, concepts of operations, roles, responsibilities, and plans governing the response and consequence management for the IND scenario exist, an ongoing integration challenge prevails regarding how best to get capable and competent surge capacity personnel (disaster reservists) and other resources engaged and readied in an up-front manner with pre-scripted assignments to augment the magnitude of anticipated demands of expertise. With the above in mind, Savannah River National Laboratory (SRNL) puts science to work to create and deploy practical, high-value, cost-effective nuclear solutions. As the Department of Energy's (DOE) applied research and development laboratory, SRNL supports Savannah River Site (SRS) operations, DOE, national initiatives, and other federal agencies, across the country and around the world. SRNL's parent at SRS also employs more than 8,000 personnel. The team is a great asset that seeks to continue their service in the interest of national security and stands ready to accomplish new missions. Overall, an integral part of the vision for SRNL's National and Homeland Security Directorate is the establishment of a National Security Center at SRNL, and development of state of the science capabilities (technologies and trained technical personnel) for responding to emergency events on local, regional, or national scales. This entails leveraging and posturing the skills, knowledge and experience base of SRS personnel to deliver an integrated capability to support local, state, and federal authorities through the development of pre-scripted requests for assistance, agreements, and plans. It
Topics in Finance Part III--Leverage
ERIC Educational Resources Information Center
Laux, Judy
2010-01-01
This article investigates operating and financial leverage from the perspective of the financial manager, accenting the relationships to stockholder wealth maximization (SWM), risk and return, and potential agency problems. It also covers some of the pertinent literature related specifically to the implications of operating and financial risk and…
Leveraging the Talent-Driven Organization
ERIC Educational Resources Information Center
Adler, Richard
2010-01-01
This report details how a number of firms are using social networking tools to open up communication, collaboration and learning across boundaries, leveraging these tools to develop new products and real-time solutions for customers. It discusses the qualities of leadership throughout an organization that fosters innovation and learning. And it…
Cultures of Collaboration: Leveraging Classroom Potential
ERIC Educational Resources Information Center
Wilhelm, Jeffrey D., Ed.
2012-01-01
A primary task of teachers is to promote the culture of collaboration in classrooms. That's because we are smarter together than we are alone. But for teachers to leverage the unique social capacity of classrooms, they need to understand how to create situations requiring and rewarding collaboration (like that of inquiry), how to structure groups,…
Leverage Learning in the University Classroom
ERIC Educational Resources Information Center
Becker, Melissa Roberts; Winn, Pam; Erwin, Susan
2013-01-01
Each semester faculty members at a regional university encountered students in their courses who were unprepared for learning. As the demand for rigor continues to increase in all fields of study continues to increase, professors expressed concern regarding preparedness of their students to enter the work-force. In an effort to leverage the…
NASA Astrophysics Data System (ADS)
Cupola, F.; Tanda, M. G.; Zanini, A.
2014-12-01
The interest in approaches that allow the estimation of pollutant source release in groundwater has increased exponentially over the last decades. This is due to the large number of groundwater reclamation procedures that have been carried out: the remediation is expensive and the costs can be easily shared among the different actors if the release history is known. Moreover, a reliable release history can be a useful tool for predicting the plume evolution and for minimizing the harmful effects of the contamination. In this framework, Woodbury and Ulrych (1993, 1996) adopted and improved the minimum relative entropy (MRE) method to solve linear inverse problems for the recovery of the pollutant release history in an aquifer. In this work, the MRE method has been improved to detect the source release history in 2-D aquifer characterized by a non-uniform flow-field. The approach has been tested on two cases: a 2-D homogeneous conductivity field and a strong heterogeneous one (the hydraulic conductivity presents three orders of magnitude in terms of variability). In the latter case the transfer function could not be described with an analytical formulation, thus, the transfer functions were estimated by means of the method developed by Butera et al. (2006). In order to demonstrate its scope, this method was applied with two different datasets: observations collected at the same time at 20 different monitoring points, and observations collected at 2 monitoring points at different times (15-25 monitoring points). The data observed were considered affected by a random error. These study cases have been carried out considering a Boxcar and a Gaussian function as expected value of the prior distribution of the release history. The agreement between the true and the estimated release history has been evaluated through the calculation of the normalized Root Mean Square (nRMSE) error: this has shown the ability of the method of recovering the release history even in the most
Macroeconomic Dynamics of Assets, Leverage and Trust
NASA Astrophysics Data System (ADS)
Rozendaal, Jeroen C.; Malevergne, Yannick; Sornette, Didier
A macroeconomic model based on the economic variables (i) assets, (ii) leverage (defined as debt over asset) and (iii) trust (defined as the maximum sustainable leverage) is proposed to investigate the role of credit in the dynamics of economic growth, and how credit may be associated with both economic performance and confidence. Our first notable finding is the mechanism of reward/penalty associated with patience, as quantified by the return on assets. In regular economies where the EBITA/Assets ratio is larger than the cost of debt, starting with a trust higher than leverage results in the highest long-term return on assets (which can be seen as a proxy for economic growth). Therefore, patient economies that first build trust and then increase leverage are positively rewarded. Our second main finding concerns a recommendation for the reaction of a central bank to an external shock that affects negatively the economic growth. We find that late policy intervention in the model economy results in the highest long-term return on assets. However, this comes at the cost of suffering longer from the crisis until the intervention occurs. The phenomenon that late intervention is most effective to attain a high long-term return on assets can be ascribed to the fact that postponing intervention allows trust to increase first, and it is most effective to intervene when trust is high. These results are derived from two fundamental assumptions underlying our model: (a) trust tends to increase when it is above leverage; (b) economic agents learn optimally to adjust debt for a given level of trust and amount of assets. Using a Markov Switching Model for the EBITA/Assets ratio, we have successfully calibrated our model to the empirical data of the return on equity of the EURO STOXX 50 for the time period 2000-2013. We find that dynamics of leverage and trust can be highly nonmonotonous with curved trajectories, as a result of the nonlinear coupling between the variables. This
A University Center Leverages Resources and Provides Access
ERIC Educational Resources Information Center
Baus, Frederick
2007-01-01
A parade of people composed of young mothers, young professionals, middle-aged men and women and elder South Carolinians are marching across the parking lot into the former McAlister Square Mall. They have access to higher education because higher education has come to them--not in the form of a traditional campus but as the concrete realization…
Leveraging Standards To Enhance the Library's Goals and Resources.
ERIC Educational Resources Information Center
Marriott, Catherine
2002-01-01
Discussion of the use of technology in primary grades focuses on a pilot project in the Orchard Park (New York) elementary schools that used computers to teach a nonfiction unit for English language arts, focusing on the New York State learning standards. Describes the role of school library media specialists and benefits to students. (LRW)
Leveraging Community Resources: Creating Successful Partnerships to Improve Schools
ERIC Educational Resources Information Center
Aidman, Barry; Baray, Sarah Nelson
2016-01-01
Educational leaders increasingly acknowledge the importance of developing partnerships to address pressing and persistent educational concerns. This article reports the results of a qualitative case study that examined an exurban district's efforts to improve educational outcomes through the development of multisector partnerships with community…
Prospective Elementary Teachers Making Sense of Multidigit Multiplication: Leveraging Resources
ERIC Educational Resources Information Center
Whitacre, Ian; Nickerson, Susan D.
2016-01-01
This study examines how collective activity related to multiplication evolved over several class sessions in an elementary mathematics content course that was designed to foster prospective elementary teachers' number-sense development. We document how the class drew on as-if-shared ideas to make sense of multidigit multiplication in terms of…
Leveraging the Libguides Platform for Electronic Resources Access Assistance
ERIC Educational Resources Information Center
Erb, Rachel A.; Erb, Brian
2014-01-01
This case study offers an alternative use of LibGuides beyond its intended purpose to offer course and subject guides. LibGuides have become an integral part of the virtual instruction landscape at Colorado State University (CSU) Libraries. We discovered that the LibGuides platform can also be effectively harnessed to provide support for…
Learning Leverage: Designing Meaningful Professional Development for "All" Teachers
ERIC Educational Resources Information Center
Hunzicker, Jana
2008-01-01
The leverage of National Board candidacy provides a unique opportunity for substantial teacher learning in a way that many professional development experiences do not. The key is learning leverage--an appropriate balance of rigor, reward, and risk. Learning leverage occurs naturally among teachers who choose to pursue National Board certification,…
12 CFR 1807.500 - Leveraged costs-general.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 12 Banks and Banking 9 2013-01-01 2013-01-01 false Leveraged costs-general. 1807.500 Section 1807.500 Banks and Banking COMMUNITY DEVELOPMENT FINANCIAL INSTITUTIONS FUND, DEPARTMENT OF THE TREASURY CAPITAL MAGNET FUND Leveraging and Commitment Requirement § 1807.500 Leveraged costs—general. (a) Each...
12 CFR 1807.500 - Leveraged costs-general.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 12 Banks and Banking 9 2012-01-01 2012-01-01 false Leveraged costs-general. 1807.500 Section 1807.500 Banks and Banking COMMUNITY DEVELOPMENT FINANCIAL INSTITUTIONS FUND, DEPARTMENT OF THE TREASURY CAPITAL MAGNET FUND Leveraging and Commitment Requirement § 1807.500 Leveraged costs—general. (a) Each...
12 CFR 1807.500 - Leveraged costs-general.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 12 Banks and Banking 7 2011-01-01 2011-01-01 false Leveraged costs-general. 1807.500 Section 1807.500 Banks and Banking COMMUNITY DEVELOPMENT FINANCIAL INSTITUTIONS FUND, DEPARTMENT OF THE TREASURY CAPITAL MAGNET FUND Leveraging and Commitment Requirement § 1807.500 Leveraged costs—general. (a) Each...
12 CFR 1807.500 - Leveraged costs-general.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 12 Banks and Banking 10 2014-01-01 2014-01-01 false Leveraged costs-general. 1807.500 Section 1807.500 Banks and Banking COMMUNITY DEVELOPMENT FINANCIAL INSTITUTIONS FUND, DEPARTMENT OF THE TREASURY CAPITAL MAGNET FUND Leveraging and Commitment Requirement § 1807.500 Leveraged costs—general. (a) Each...
Leveraging public private partnerships to innovate under challenging budget times.
Portilla, Lili M; Rohrbaugh, Mark L
2014-01-01
The National Institutes of Health (NIH), academic medical centers and industry have a long and productive history in collaborating together. Decreasing R&D budgets in both the private and public sector have made the need for such collaborations paramount to reduce the risk of further declines in the number of innovative drugs reaching the market to address pressing public health needs. Doing more with less has forced both industry and public sector research institutions (PSRIs) to leverage resources and expertise in order to de-risk projects. In addition, it provides an opportunity to envision and implement new approaches to accomplish these goals. We discuss several of these innovative collaborations and partnerships at the NIH that demonstrate how the NIH and industry are working together to strengthen the drug development pipeline. PMID:24283971
Leveraging Public Private Partnerships to Innovate Under Challenging Budget Times
Portilla, Lili M.; Rohrbaugh, Mark
2014-01-01
The National Institutes of Health (NIH), academic medical centers and industry have a long and productive history in collaborating together. Decreasing R&D budgets both the private and public sector have made the need for such collaborations paramount [critical?] to reduce the risk of [further?] declines in the number of innovative drugs reaching the market to address pressing public health needs. Doing more with less has forced both industry and public sector research institutions (PSRIs) to leverage resources and expertise in order to de-risk projects. In addition, it provides an opportunity to envision and implement new approaches to accomplish these goals. We discuss several of these innovative collaborations and partnerships at the NIH that demonstrate how the NIH and industry are working together to strenghten the drug development pipeline. PMID:24283971
Towards the Use of Space Resources
NASA Technical Reports Server (NTRS)
Martin, Gary L.
2015-01-01
Humans are making technological progress at leveraging resources in space. Ames is a pioneer in In-Situ Resource Utilization (ISRU). ISRU is among the only cost-effective ways to construct habitats off-world.
Leveraging Spatial Model to Improve Indoor Tracking
NASA Astrophysics Data System (ADS)
Liu, L.; Xu, W.; Penard, W.; Zlatanova, S.
2015-05-01
In this paper, we leverage spatial model to process indoor localization results and then improve the track consisting of measured locations. We elaborate different parts of spatial model such as geometry, topology and semantics, and then present how they contribute to the processing of indoor tracks. The initial results of our experiment reveal that spatial model can support us to overcome problems such as tracks intersecting with obstacles and unstable shifts between two location measurements. In the future, we will investigate more exceptions of indoor tracking results and then develop additional spatial methods to reduce errors of indoor tracks.
17 CFR 31.15 - Reporting to leverage customers.
Code of Federal Regulations, 2011 CFR
2011-04-01
... furnish in writing directly to each leverage customer: (a) Promptly upon the repurchase, resale... the terminating transaction involved repurchase, resale, liquidation, rescission, or delivery,...
Adaptations to a Learning Resource
ERIC Educational Resources Information Center
Libbrecht, Paul
2015-01-01
Learning resources have been created to represent digital units of exchangeable materials that teachers and learners can pull from in order to support the learning processes. They resource themselves. Leveraging the web, one can often find these resources. But what characteristics do they need in order to be easily exchangeable? Although several…
Leveraging Gaming Technology to Deliver Effective Training
NASA Technical Reports Server (NTRS)
Cimino, James D.
2011-01-01
The best way to engage a soldier is to present them with training content consistent with their learning preference. Blended Interactive Multimedia Instruction (IMI) can be used to leach soldiers what they need to do, how to do each step, and utilize a COTS game engine to actually practices the skills learned. Blended IMI provides an enjoyable experience for the soldier, thereby increasing retention rates and motivation while decreasing the time to subject mastery. And now mobile devices have emerged as an exciting new platform, literally placing the training into the soldier's hands. In this paper, we will discuss how we leveraged commercial game engine technology, tightly integrated with the Blended IMI, to train soldiers on both laptops and mobile devices. We will provide a recent case study of how this training is being utilized, benefits and student/instructor feedback.
Leveraging object-oriented development at Ames
NASA Technical Reports Server (NTRS)
Wenneson, Greg; Connell, John
1994-01-01
This paper presents lessons learned by the Software Engineering Process Group (SEPG) from results of supporting two projects at NASA Ames using an Object Oriented Rapid Prototyping (OORP) approach supported by a full featured visual development environment. Supplemental lessons learned from a large project in progress and a requirements definition are also incorporated. The paper demonstrates how productivity gains can be made by leveraging the developer with a rich development environment, correct and early requirements definition using rapid prototyping, and earlier and better effort estimation and software sizing through object-oriented methods and metrics. Although the individual elements of OO methods, RP approach and OO metrics had been used on other separate projects, the reported projects were the first integrated usage supported by a rich development environment. Overall the approach used was twice as productive (measured by hours per OO Unit) as a C++ development.
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.
78 FR 17766 - Interagency Guidance on Leveraged Lending
Federal Register 2010, 2011, 2012, 2013, 2014
2013-03-22
.... The number of community banks with substantial involvement in leveraged lending is small; therefore, the agencies generally expect community banks to be largely unaffected by this guidance. DATES: This... INFORMATION. \\1\\ See 77 FR 19417 ``Proposed Guidance on Leveraged Lending'' dated March 30, 2012 at...
17 CFR 31.8 - Cover of leverage contracts.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 17 Commodity and Securities Exchanges 1 2010-04-01 2010-04-01 false Cover of leverage contracts. 31.8 Section 31.8 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION LEVERAGE... of such option is more than the value of the underlying commodity based on the strike price of...
7 CFR 4290.1100 - Type of Leverage and application procedures.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 7 Agriculture 15 2010-01-01 2010-01-01 false Type of Leverage and application procedures. 4290... INVESTMENT COMPANY (âRBICâ) PROGRAM Financial Assistance for RBICs (Leverage) General Information About Obtaining Leverage § 4290.1100 Type of Leverage and application procedures. (a) Type of Leverage...
Leveraging melanocortin pathways to treat glomerular diseases
Gong, Rujun
2013-01-01
The melanocortin system is a neuroimmunoendocrine hormone system that constitutes the fulcrum in the homeostatic control of a diverse array of physiological functions, including melanogenesis, inflammation, immunomodulation, adrenocortical steroidogenesis, hemodynamics, natriuresis, energy homeostasis, sexual function and exocrine secretion. The kidney is a quintessential effector organ of the melanocortin hormone system with melanocortin receptors abundantly expressed by multiple renal paranchymal cells, including podocytes, mesangial cells, glomerular endothelial cells and renal tubular cells. Converging evidence unequivocally demonstrates that the melanocortin based therapy by using the melanocortin peptide adrenocorticotropic hormone (ACTH) is prominently effective in inducing remission of steroid resistant nephrotic syndrome caused by a variety of glomerular diseases, including membranous nephropathy and podocytopathies such as minimal change disease and focal segmental glomerulosclerosis, suggesting a steroidogenic independent melanocortin mechanism. Mechanistically, ACTH and other melanocortin peptides as well as synthetic melanocortin analogues possess potent proteinuria reducing and renoprotective effects that could be attributable to both direct protection of glomerular cells and systemic immunomodulation. Thus, leveraging melanocortin signaling pathways by using either the existing U.S. Food and Drug Administration approved melanocorin peptide ACTH or novel synthetic melanocortin analogues represents a promising and pragmatic therapeutic strategy for glomerular diseases. This review article introduces the biophysiology of melanocortin hormone system with emphasis on the kidney as the target organ, discusses the existing clinical and experimental data on melanocortin treatments for glomerular diseases, elucidates the potential mechanisms of action, and describes the potential side effects of melanocortin based therapy. PMID:24602463
13 CFR 108.1150 - Maximum amount of Leverage for a NMVC Company.
Code of Federal Regulations, 2010 CFR
2010-01-01
... NEW MARKETS VENTURE CAPITAL (âNMVCâ) PROGRAM SBA Financial Assistance for NMVC Companies (Leverage... percent of its Leverageable Capital. Conditional Commitments by SBA To Reserve Leverage for a NMVC Company...
7 CFR 4290.3005 - Qualifications for the Non-leveraged RBIC Program.
Code of Federal Regulations, 2014 CFR
2014-01-01
... applications for Non-leveraged RBICs. (c) Management and ownership diversity requirements. A Non-leveraged RBIC...) Approval of initial Management Expenses. Section 4290.140 does not apply to Non-leveraged RBICs....
Glyavin, M. Yu.; Golubev, S. V.; Izotov, I. V.; Litvak, A. G.; Luchinin, A. G.; Razin, S. V.; Sidorov, A. V.; Skalyga, V. A.; Vodopyanov, A. V.
2014-10-27
The possibility and prospects of extreme ultraviolet (UV) point-like source development are discussed in the present paper. The UV source is based on the discharge sustained by powerful gyrotron radiation of terahertz (THz) frequency band in non-uniform gas flow injected into vacuum volume through a nozzle with diameter less than 1 mm. Recent developments of THz-band gyrotrons with appropriate power level made such discharges possible. First experimental results on a point-like plasma creation by 100 kW radiation of 0.67 THz gyrotron are presented. The possibility of discharge localization within the area less than 1 mm is demonstrated. The discharge emission within the wavelength range from 112 nm to 650 nm was studied. The measured power of light emission in the range of 112–180 nm was measured to be up to 10 kW.