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.
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…
Terminology access methods leveraging LDAP resources.
Solbrig, Harold R; Chute, Christopher G
2004-01-01
Health terminologies have become more complex, more massive, and more ubiquitous in the modern healthcare enterprise. Present technology makes the use of these terminologies by humans, unaided by machines, virtually impossible. However, system and message interoperability can be severely compromised if the software services deploying terminology content and interfaces are themselves non-standard. We review some characteristics for good terminology services and introduce an open-source, robust, widely deployed and widely available software resource to underpin terminology service implementations. The Lightweight Directory Access Protocol, or LDAP, is compared with alternative technologies. We describe a reference implementation of terminology services built around the HL7 Common Terminology Services using LDAP methods. We propose that LDAP is well suited as a common platform for federated, synchronized, and algorithmically distributed terminology content from multiple sources.
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.
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.
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.
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.
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…
Leveraging Resources and Sustaining Partnerships in Tough Economic Times
ERIC Educational Resources Information Center
Booth, Cheryl N.; Vaidya, Shruti J.; Farrell, Patricia A.; Bokemeier, Janet L.
2004-01-01
During times of economic uncertainty, how can universities develop and sustain resources for engagement efforts? This article focuses on how a university-wide research and outreach coalition at Michigan State University called Families and Communities Together (FACT) is exploring a variety of funding approaches and implementing successful…
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…
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…
Elastic stability of non-uniform columns
NASA Astrophysics Data System (ADS)
Lee, S. Y.; Kuo, Y. H.
1991-07-01
A simple and efficient method is proposed to investigate the elastic stability of three different tapered columns subjected to uniformly distributed follower forces. The influences of the boundary conditions and taper ratio on critical buckling loads are investigated. The critical buckling loads of columns of rectangular cross section with constant depth and linearly varied width ( T1), constant width and linearly varied depth ( T2) and double taper ( T3) are investigated. Among the three different non-uniform columns considered, taper ratio has the greatest influence on the critical buckling load of column T3 and the lowest influence on that of column T1. The types of instability mechanisms for hinged-hinged and cantilever non-uniform columns are divergence and flutter respectively. However, for clamped-hinged and clamped-clamped non-uniform columns, the type of instability mechanism for column T1 is divergence, while that for columns T2 and T3 is divergence only when the taper ratio of the columns is greater than certain critical values and flutter for the rest value of taper ratio. When the type of instability mechanism changes from divergence to flutter, there is a finite jump for the critical buckling load. The influence of taper ratio on the elastic stability of cantilever column T3 is very sensitive for small values of the taper ratio and there also exist some discontinieties in the critical buckling loads of flutter instability. For a hinged-hinged non-uniform column ( T2 or T3) with a rotational spring at the left end of the column, when the taper ratio is less than the critical value the instability mechanism changes from divergence to flutter as the rotational spring constant is increased. For a clamped-elastically supported non-uniform column, when the taper ratio is greater than the critical value the instability mechanism changes from flutter to divergence as the translational spring constant is increased.
Non-uniform space charge controlled KTN beam deflector
NASA Astrophysics Data System (ADS)
Chao, Ju-Hung; Zhu, Wenbin; Chen, Chang-Jiang; Yin, Stuart; Hoffman, Robert C.
2016-09-01
A non-uniform space charge-controlled KTN beam deflector is presented and analyzed. We found that a non-uniform space charge can result in a non-uniform beam deflection angles. This effect can be useful for some applications such as electric field controlled beam separation. However, a non-uniform space charge needs to be avoided if one wants uniform beam deflection throughout the entire crystal.
Leveraging External Resources To Grow and Sustain Your Palliative Care Program: A Call to Action
Kerr, Kathleen M.; Kutner, Jean S.; Ferris, Frank D.; Rathfon, Megan A.; Rabow, Michael W.
2012-01-01
Abstract Hospital-based palliative care is becoming increasingly prevalent. There is growing evidence that it is having a positive impact on patients and their loved ones. In 2008, national data indicated that 58.5% of hospitals with 50 or more beds had a palliative care program. Data from a 2008 survey of California acute care hospitals showed that although 33% of sites had inpatient consultation services, one in five had been operational for only one year. As nascent palliative care programs grow, new issues arise and needs and plans change. Just as palliative care programs benefit from marketing and education plans, they also benefit from a plan to leverage external resources. Largely a missed opportunity, external resources such as organizations, networks, and experts can help palliative care service (PCS) leaders and team members gain information on everything from best practices to funding opportunities, while serving as sources for personal and professional support. The growing number of active PCSs and the increasing availability of support and expertise ensure that new programs no longer have to face challenges alone. Further, the steady increase in the number of new programs has created opportunities for those who are more experienced to serve as mentors for peers who are navigating the challenges of growing and sustaining a clinical service. The authors encourage both mentors and mentees to seek support from or provide support to others in the field. Leveraging the collective expertise and experiences in our field can ensure that palliative care continues to thrive and grow. PMID:22165898
A non-uniform grid for triangular differential quadrature
NASA Astrophysics Data System (ADS)
Zhong, HongZhi; Xu, Jia
2016-12-01
The triangular differential quadrature method based on a non-uniform grid is proposed in the paper. Explicit expressions of the non-uniform grid point coordinates are given and the weighting coefficients of the triangular differential quadrature method are determined with the aid of area coordinates. Two typical examples are presented to testify the effectiveness of the non-uniform grid. It is shown that rapid convergence is achieved under the non-uniform grid in comparison with those from the uniform grid with the same order of approximation.
Hale-Gallardo, Jennifer; Jia, Huanguang; Delisle, Tony; Levy, Charles E; Osorio, Valentina; Smith, Jennifer A; Hannold, Elizabeth M
2017-01-01
The number of US veterans with disabilities has increased in recent years as service members have returned home with extensive injuries and veterans from previous wars acquire functional limitations as a consequence of aging with chronic diseases. Veterans with severe disabilities need assistance and support to maintain independence at home and to avoid institutionalization. The US Department of Veterans Affairs (VA) strives to network with community organizations to achieve the best possible outcomes for veterans. Key community resources in the US for individuals with disabilities are Centers for Independent Living (CILs) that provide a wide range of services, promoting independent living and well-being for people across disabilities. The widespread availability and services of CILs nationwide suggest their potential as a community-based resource for veterans, particularly for those with limited access to VA care. In this article, we discuss long-term needs of veterans with disabilities, efforts to address veterans’ rehabilitation needs at the VA and opportunities for leveraging the strengths of community-based organizations for veterans. More research is warranted to investigate CIL services and potential for CIL–VA partnerships. PMID:28182140
Lomb-Wech periodogram for non-uniform sampling.
Thong, Tran; McNames, James; Aboy, Mateo
2004-01-01
The Lomb-Scargle transform has been proposed for the direct evaluation, namely without interpolation, of non-uniformly sampled signals. In its current form, it is suitable only for single transform evaluation due to the implicit normalization. Enhancements of this transform are proposed to allow the evaluation of shorter transforms, combined with windows and averaging of overlapped records. This requires a de-normalization of the transform by a factor of 2(sigma)/sup 2//N, the use of equal time duration records, and multiplication by windows sampled at corresponding non-uniform time instances. This results in a Welch-like periodogram for non-uniform sampling.
Non-uniform beam vibration using Differential Transform Method
NASA Astrophysics Data System (ADS)
Shali, S.; Nagaraja, S. R.; Jafarali, P.
2016-09-01
The paper focuses on the vibration characteristics of non-uniform Euler- Bernoulli beam using Differential Transform Method (DTM). DTM is a numerical method to solve differential equations where the governing equations are reduced into a set of polynomials. Non-uniformity is considered corresponding to linear variation in breadth and height of the beam. The effect of taper ratio on the fundamental frequency of tapered beams is also analysed. The method has proved to be accurate, simple and effective for eigenvalue analysis. For the two cases of non-uniform beam analysed, the frequency computed by the method of differential transform is found to be comparable with the previously available results.
ERIC Educational Resources Information Center
Ellinger, Alexander E.; Ellinger, Andrea D.
2014-01-01
Purpose: There is an ongoing shortage of talented supply chain managers with the necessary skills and business-related competencies to manage increasingly complex and strategically important supply chain processes. The purpose of this paper is to propose that organizations can create and maintain competitive advantage by leveraging the expertise…
GaAs MESFET with lateral non-uniform doping
NASA Technical Reports Server (NTRS)
Wang, Y. C.; Bahrami, M.
1983-01-01
An analytical model of the GaAs MESFET with arbitrary non-uniform doping is presented. Numerical results for linear lateral doping profile are given as a special case. Theoretical considerations predict that better device linearity and improved F(T) can be obtained by using linear lateral doping when doping density increases from source to drain.
Dorsey, Susan G.; Schiffman, Rachel; Redeker, Nancy S.; Heitkemper, Margaret; McCloskey, Donna Jo; Weglicki, Linda S.; Grady, Patricia A.
2014-01-01
The 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 a 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. PMID:25085328
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.
Spin Wave Propagation in Non-Uniform Magnetic Fields
2006-11-01
set-up. The yttrium iron garnet ( YIG ) film strip is magnetized to saturation by a z − dependent static field ( )H z . The microstrip transducer is...time- and space-resolved measurements of spin wave pulse propagation properties in a magnetic film strip magnetized to saturation with non-uniform...EXPERIMENT Figure 1 shows a schematic of the experimental set- up. The magnetic medium was a yttrium iron garnet ( YIG ) film strip cut from a
Non-Uniform Electromagnetic Fields in the SAMURAI TPC
NASA Astrophysics Data System (ADS)
Estee, J.; Barney, J.; Chajecki, Z.; Chan, C. F.; Dunn, J. W.; Gilbert, J.; Lu, F.; Lynch, W. G.; Shane, R.; Tsang, M. B.; McIntosh, A. B.; Yennello, S. J.; Famiano, M.; Isobe, T.; Sakurai, H.; Taketani, A.; Murakami, T.; Samurai-Tpc Collaboration
2011-10-01
A Time Projection Chamber (TPC) is being developed for the SAMURAI dipole magnet at RIKEN. The main scientific objective for the TPC is to provide constraints on the nuclear symmetry at supra-saturation density. The poster presentation will discuss the design of the TPC field cage and the external electrodes that shape the high electric fields near the cathode. Garfield calculations of the electric field as well as TOSCA calculations of the magnetic field of the SAMURAI dipole will be shown and the impact of the non-uniformity of both fields on electron transport will be discussed. These non-uniformities can introduce components into the electron drift velocity in directions other than the expected vertical direction. This poster presentation will discuss the initial design of a laser calibration system, which will be used to calibrate away the influence of these non-uniformities in the electric and magnetic fields. This work is supported by the DOE under Grant DE-SC0004835.
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.
Wave modeling in a cylindrical non-uniform helicon discharge
Chang, L.; Hole, M. J.; Caneses, J. F.; Blackwell, B. D.; Corr, C. S.; Chen, G.
2012-08-15
A radio frequency field solver based on Maxwell's equations and a cold plasma dielectric tensor is employed to describe wave phenomena observed in a cylindrical non-uniform helicon discharge. The experiment is carried out on a recently built linear plasma-material interaction machine: The magnetized plasma interaction experiment [Blackwell et al., Plasma Sources Sci. Technol. (submitted)], in which both plasma density and static magnetic field are functions of axial position. The field strength increases by a factor of 15 from source to target plate, and the plasma density and electron temperature are radially non-uniform. With an enhancement factor of 9.5 to the electron-ion Coulomb collision frequency, a 12% reduction in the antenna radius, and the same other conditions as employed in the experiment, the solver produces axial and radial profiles of wave amplitude and phase that are consistent with measurements. A numerical study on the effects of axial gradient in plasma density and static magnetic field on wave propagations is performed, revealing that the helicon wave has weaker attenuation away from the antenna in a focused field compared to a uniform field. This may be consistent with observations of increased ionization efficiency and plasma production in a non-uniform field. We find that the relationship between plasma density, static magnetic field strength, and axial wavelength agrees well with a simple theory developed previously. A numerical scan of the enhancement factor to the electron-ion Coulomb collision frequency from 1 to 15 shows that the wave amplitude is lowered and the power deposited into the core plasma decreases as the enhancement factor increases, possibly due to the stronger edge heating for higher collision frequencies.
Non-uniform impact excitation of a cylindrical bar
NASA Astrophysics Data System (ADS)
Karp, Baruch; Dorogoy, Avraham; Wang, Zonggang
2009-06-01
An experimental and numerical study of a non-uniform impact excitation of a circular bar is reported. In experiments, nine strikers with different contact area were accelerated against a circular bar. Axial surface strain of the impacted bar was measured at several distances from the impinged end to include the near and the far fields. The same experimental conditions were solved numerically using a commercial finite element code. It was demonstrated that the far-field response is insensitive to both the size and the form of the striker's colliding end. The distance at which such insensitivity is set is estimated to be approximately one and a half bar diameters.
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.
Elastic deformations driven by non-uniform lubrication flows
NASA Astrophysics Data System (ADS)
Rubin, Shimon; Tulchinsky, Arie; Gat, Amir D.; Bercovici, Moran
2017-02-01
The ability to create dynamic deformations of micron-sized structures is relevant to a wide variety of applications such as adaptable optics, soft robotics, and reconfigurable microfluidic devices. In this work we examine non-uniform lubrication flow as a mechanism to create complex deformation fields in an elastic plate. We consider a Kirchoff-Love elasticity model for the plate and Hele-Shaw flow in a narrow gap between the plate and a parallel rigid surface. Based on linearization of the Reynolds equation, we obtain a governing equation which relates elastic deformations to gradients in non-homogenous physical properties of the fluid (e.g. body forces, viscosity, and slip velocity). We then focus on a specific case of non-uniform Helmholtz-Smoluchowski electroosmotic slip velocity, and provide a method for determining the zeta-potential distribution necessary to generate arbitrary static and quasi-static deformations of the elastic plate. Extending the problem to time-dependent solutions, we analyze transient effects on asymptotically static solutions, and finally provide a closed form solution for a Green's function for time periodic actuations.
Longitudinal oscillations in a non-uniform spatially dispersive plasma
Calogeracos, Alex
2015-03-15
Longitudinal oscillations of the electron fluid in the hydrodynamic model of a metal are examined with pressure effects taken into account. It is well-known that this entails spatial dispersion. The equilibrium electron number density is taken to be non-uniform and a non-self-adjoint fourth order differential equation obeyed by the electric potential is derived. A velocity potential necessary for the description of sound waves is introduced in the standard fashion and the generalized version of Bloch orthogonality appropriate to a non-uniform background is deduced. We observe a duality between electric and velocity potentials in the sense that the respective differential operators are adjoint to each other. The spectrum is calculated in the special case of an exponential profile for the equilibrium electron number density. The surface plasmons are connected with the analytic properties of the scattering amplitude in the complex plane. The phase shift at threshold is expressed in terms of the number of surface plasmon modes via an expression reminiscent of Levinson’s statement in quantum mechanics.
Expanding Window Compressed Sensing for Non-Uniform Compressible Signals
Liu, Yu; Zhu, Xuqi; Zhang, Lin; Cho, Sung Ho
2012-01-01
Many practical compressible signals like image signals or the networked data in wireless sensor networks have non-uniform support distribution in their sparse representation domain. Utilizing this prior information, a novel compressed sensing (CS) scheme with unequal protection capability is proposed in this paper by introducing a windowing strategy called expanding window compressed sensing (EW-CS). According to the importance of different parts of the signal, the signal is divided into several nested subsets, i.e., the expanding windows. Each window generates its own measurements using a random sensing matrix. The more significant elements are contained by more windows, so they are captured by more measurements. This design makes the EW-CS scheme have more convenient implementation and better overall recovery quality for non-uniform compressible signals than ordinary CS schemes. These advantages are theoretically analyzed and experimentally confirmed. Moreover, the EW-CS scheme is applied to the compressed acquisition of image signals and networked data where it also has superior performance than ordinary CS and the existing unequal protection CS schemes. PMID:23201984
Vibration analysis of multiple-cracked non-uniform beams
NASA Astrophysics Data System (ADS)
Mazanoglu, K.; Yesilyurt, I.; Sabuncu, M.
2009-03-01
This paper presents the energy-based method for the vibration identification of non-uniform Euler-Bernoulli beams having multiple open cracks. The method includes significant modifications for the energy-based method presented by Yang et al. [Crack identification in vibrating beams using the energy method, Journal of Sound and Vibration 244 (2) (2001) 339-357.] The distribution of the energy consumed is determined by taking into account not only the strain change at the cracked beam surface as in general but also the considerable effect of the stress field caused by the angular displacement of the beam due to bending. The Rayleigh-Ritz approximation method is used in the analysis. The method is adapted to the cases of multiple cracks with an approach based on the definition of strain disturbance variation along the beam. Examples are presented on cantilever beams having different truncation factors. When the results are compared with a commercial finite element program and with the results of Zheng and Fan [Natural frequencies of a non-uniform beam with multiple cracks via modified Fourier series, Journal of Sound and Vibration 242 (4) (2001) 701-717], good agreements are obtained. The effects of truncation factors and positions of cracks on the natural frequency ratios are presented in graphics.
Steady solutions for plumes in non-uniform stratifications
NASA Astrophysics Data System (ADS)
Kaye, Nigel; Scase, Matthew
2010-11-01
The plume conservation equations of Morton et al. (1956) are recast in terms of the plume radius, flux balance parameter γ, and a dimensionless parameter that characterizes the stratification. This set of equations lead to simple analytic solutions for steady straight sided plumes in non-uniformly stratified environments. Steady plumes in non-uniform stratification can occur for both stable (Caulfield & Woods 1998) and unstable (Batchelor 1954) stratifications whose strength has a power law variation with height. We present analytic solutions for the range of stratification power-law decay rates κ for which straight sided plumes are possible. The approach used provides significant physical insight into the limits on κ that permit straight sided solutions. We also present analytic solutions for the power law behaviour with height of the fluxes of volume, momentum and buoyancy. This result demonstrates that the models of Batchelor and Caulfield & Woods are two halves of the same continuum of solutions. The flux power law behavior explains the transition between the Batchelor solutions and the Caulfield & Woods solutions that occurs when κ=-8/3. For κ<-8/3 the buoyancy flux decays with height and, therefore, the stratification must be stable. Whereas for κ>-8/3 the buoyancy flux must increase with height, requiring an unstable stratification.
Electrostatic adhesion of multiple non-uniformly charged dielectric particles
NASA Astrophysics Data System (ADS)
Kemp, B. A.; Whitney, J. G.
2013-01-01
Charged particle adhesion measurements can be as much as one order of magnitude higher than theoretical calculations. This discrepancy has ignited a debate as to the nature of the physics occurring with microscopic particle adhesion. Attempts to bring calculations closer to measured results have produced models that include multiple particle interactions, dielectric polarization, and non-uniform charge. Individually, each of these models can only produce a 2× to 5× enhancement in predicted adhesion force over simple Coulombic attraction. In this correspondence, an analytical model of electrostatic particle forces is developed, which allows for independent assignment of dielectric constant and non-uniform surface charge distribution to an arbitrary number of particles. Because the model can include an image plane, it is ideal for electrostatic adhesion calculations. Application to a monolayer of printed toner particles predicts nearly an order of magnitude increase in adhesion force over Coulombic attraction. These results are the first analytical results to place predictions of charged particle adhesion on the same order of magnitude with measurements.
Non-uniform Evolving Hypergraphs and Weighted Evolving Hypergraphs
Guo, Jin-Li; Zhu, Xin-Yun; Suo, Qi; Forrest, Jeffrey
2016-01-01
Firstly, this paper proposes a non-uniform evolving hypergraph model with nonlinear preferential attachment and an attractiveness. This model allows nodes to arrive in batches according to a Poisson process and to form hyperedges with existing batches of nodes. Both the number of arriving nodes and that of chosen existing nodes are random variables so that the size of each hyperedge is non-uniform. This paper establishes the characteristic equation of hyperdegrees, calculates changes in the hyperdegree of each node, and obtains the stationary average hyperdegree distribution of the model by employing the Poisson process theory and the characteristic equation. Secondly, this paper constructs a model for weighted evolving hypergraphs that couples the establishment of new hyperedges, nodes and the dynamical evolution of the weights. Furthermore, what is obtained are respectively the stationary average hyperdegree and hyperstrength distributions by using the hyperdegree distribution of the established unweighted model above so that the weighted evolving hypergraph exhibits a scale-free behavior for both hyperdegree and hyperstrength distributions. PMID:27845334
Asynchronous signal-dependent non-uniform sampler
NASA Astrophysics Data System (ADS)
Can-Cimino, Azime; Chaparro, Luis F.; Sejdić, Ervin
2014-05-01
Analog sparse signals resulting from biomedical and sensing network applications are typically non-stationary with frequency-varying spectra. By ignoring that the maximum frequency of their spectra is changing, uniform sampling of sparse signals collects unnecessary samples in quiescent segments of the signal. A more appropriate sampling approach would be signal-dependent. Moreover, in many of these applications power consumption and analog processing are issues of great importance that need to be considered. In this paper we present a signal dependent non-uniform sampler that uses a Modified Asynchronous Sigma Delta Modulator which consumes low-power and can be processed using analog procedures. Using Prolate Spheroidal Wave Functions (PSWF) interpolation of the original signal is performed, thus giving an asynchronous analog to digital and digital to analog conversion. Stable solutions are obtained by using modulated PSWFs functions. The advantage of the adapted asynchronous sampler is that range of frequencies of the sparse signal is taken into account avoiding aliasing. Moreover, it requires saving only the zero-crossing times of the non-uniform samples, or their differences, and the reconstruction can be done using their quantized values and a PSWF-based interpolation. The range of frequencies analyzed can be changed and the sampler can be implemented as a bank of filters for unknown range of frequencies. The performance of the proposed algorithm is illustrated with an electroencephalogram (EEG) signal.
Andela, Valentine B
2006-01-01
In developing countries, low levels of awareness, cost and organizational constraints on access to specialized care contribute to inadequate patient help-seeking behavior. As much as 95% of cancer patients in developing countries are diagnosed at late to end stage disease. Consequently, treatment outcome is dismally poor and a vicious cycle sets in, with public mystification of cancer and the admonishment of cancer medicine as a futile effort, all, to the further detriment of patient help-seeking behavior and treatment engagement. The situation spirals down, when the practice of cancer medicine is not gratifying to the medical practitioner and does not appeal as a medical specialty to those in training. The future of cancer medicine in developing countries thus hinges on the demystification of cancer through positive information, coupled to an effective organization that allows for the optimal use of available resources, facilitates access to specialized care and promotes the flow of knowledge and technology amongst various stakeholders. This paper strives to make a cogent argument and highlight the capital importance of information and communication technologies in organizing and leveraging scarce resources for cancer education, research and practice in developing countries. PMID:16390555
Martin, S.W.
1995-02-01
Review domestic and international policy, US Intellectual Property (IP) and Technology Transfer (TT) legislation, and related Department of Energy (DOE) programs to ensure Department resources are leveraged to the benefit of the US economy. Mapping such processes should determine if/how foreign governments and/or foreign owned or controlled enterprises, specifically Japanese and to a lessor extent other Pacific Rim nations, are able to access and at times leverage US technology to their benefit. This process will also generate lessons learned that should be useful to government and industry alike in the area of TT. The review will concentrate on technology innovations developed or funded by the Department.
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.
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.
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.
Longitudinal image registration with non-uniform appearance change.
Csapo, Istvan; Davis, Brad; Shi, Yundi; Sanchez, Mar; Styner, Martin; Niethammer, Marc
2012-01-01
Longitudinal imaging studies are frequently used to investigate temporal changes in brain morphology. Image intensity may also change over time, for example when studying brain maturation. However, such intensity changes are not accounted for in image similarity measures for standard image registration methods. Hence, (i) local similarity measures, (ii) methods estimating intensity transformations between images, and (iii) metamorphosis approaches have been developed to either achieve robustness with respect to intensity changes or to simultaneously capture spatial and intensity changes. For these methods, longitudinal intensity changes are not explicitly modeled and images are treated as independent static samples. Here, we propose a model-based image similarity measure for longitudinal image registration in the presence of spatially non-uniform intensity change.
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.
Acoustic power in non-uniform lined ducts
NASA Astrophysics Data System (ADS)
Eversman, Walter
2008-06-01
A definition of acoustic power in conservation form in lined infinitely long uniform ducts is extended to include axially symmetric non-uniform ducts with potential mean flow and finite length lining. The definition includes a contribution at the lined boundary. Benchmarking is accomplished by verification of acoustic power conservation in the case of a purely reactive lining. Calculations in the case of reactively lined ducts show that intense acoustic gradients near the lined surface can occur, and contributions to acoustic power from the boundary power term become relatively large. This observed behavior diminishes as the resistive component of lining impedance is increased. Power calculations for propagation and radiation from a typical turbo-fan inlet and equivalent calculations for an infinite duct propagation model of the same inlet contour are compared. Results are remarkably similar for the case considered, though it is noted that this conclusion is geometry dependent.
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.
Coupled Serial and Parallel Non-uniform SQUIDs
NASA Astrophysics Data System (ADS)
Longhini, Patrick; Berggren, Susan; Palacios, Antonio; de Escobar, Anna Leese; In, Visarath
2011-04-01
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.
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%.
Restoration of non-uniform exposure motion blurred image
NASA Astrophysics Data System (ADS)
Luo, Yuanhong; Xu, Tingfa; Wang, Ningming; Liu, Feng
2014-11-01
Restoring motion-blurred image is the key technologies in the opto-electronic detection system. The imaging sensors such as CCD and infrared imaging sensor, which are mounted on the motion platforms, quickly move together with the platforms of high speed. As a result, the images become blur. The image degradation will cause great trouble for the succeeding jobs such as objects detection, target recognition and tracking. So the motion-blurred images must be restoration before detecting motion targets in the subsequent images. On the demand of the real weapon task, in order to deal with targets in the complex background, this dissertation uses the new theories in the field of image processing and computer vision to research the new technology of motion deblurring and motion detection. The principle content is as follows: 1) When the prior knowledge about degradation function is unknown, the uniform motion blurred images are restored. At first, the blur parameters, including the motion blur extent and direction of PSF(point spread function), are estimated individually in domain of logarithmic frequency. The direction of PSF is calculated by extracting the central light line of the spectrum, and the extent is computed by minimizing the correction between the fourier spectrum of the blurred image and a detecting function. Moreover, in order to remove the strip in the deblurred image, windows technique is employed in the algorithm, which makes the deblurred image clear. 2) According to the principle of infrared image non-uniform exposure, a new restoration model for infrared blurred images is developed. The fitting of infrared image non-uniform exposure curve is performed by experiment data. The blurred images are restored by the fitting curve.
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.
An immersed boundary method for non-uniform Cartesian grids
NASA Astrophysics Data System (ADS)
Jang, Juwon; Lee, Changhoon
2016-11-01
Many kinds of immersed boundary method have been developed, but most of them have been used in uniform grids with discrete Dirac delta functions. Therefore, the distribution of Lagrangian points over the immersed surface is usually made uniformly. However, when any immersed boundary method is to be applied to non-uniform grids, uniform distribution might not be optimum for good performance. Recently, Akiki and Balachandar (2016) proposed a method to distribute the Lagrangian points nonuniformly over the surface of a sphere near the wall, but it cannot not be extended to more general shape of immersed surface. We propose a method that is capable for properly distributing the Lagrangian points over any kind of surface by considering the size of nearby Eulerian grids. Present method first finds intersection points between immersed surface and nonuniform Cartesian grids. Then, the centroid of the intersection points is projected on the immersed surface to be designated by Lagrangian point. This procedure guarantees one Lagrangian point per the Eulerian grid cell. This method is validated for various problems such as flows around a settling sphere, a moving sphere in the near-wall region and a tilted ellipsoid near the wall.
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.
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.
Coupled non-uniform bi-squid: A numerical investigation
NASA Astrophysics Data System (ADS)
Longhini, Patrick; Berggren, Susan; Palacios, Antonio; In, Visarath; Leese de Escobar, Anna
2012-06-01
This work investigates through numerical simulations a novel device that improvesdynamic range and linearity. The standard DC SQUID can increase in linearity by adding athird junction, changing to a device known as the bi-SQUID. It is known that the dynamicrange can increase by connecting SQUIDs in series, and it has been shown that nonuniformityin the loops sizes in arrays of SQUIDs can produce a unique 'anti'-peak at thezero magnetic flux (device know as a SQIF). Thus, combining these ideas we can improvethe dynamic range and design a highly linear device with a unique 'anti'-peak. Hence, this device can be referred to as a bi-SQIF or non-uniform bi-SQUID array. Results have shown that the maximum voltage swing increase proportional to N, where N is the number of loops connected in series. The spur free dynamic range also improves as N increases, which is directly related to the linearity of the device. Therefore, we have designed a device which can lead to improvements which can be applicable to low noise amplifier (LNA), and provide a platform for creating "electrically" small antennas.
Generalized quantum counting algorithm for non-uniform amplitude distribution
NASA Astrophysics Data System (ADS)
Tan, Jianing; Ruan, Yue; Li, Xi; Chen, Hanwu
2017-03-01
We give generalized quantum counting algorithm to increase universality of quantum counting algorithm. Non-uniform initial amplitude distribution is possible due to the diversity of situations on counting problems or external noise in the amplitude initialization procedure. We give the reason why quantum counting algorithm is invalid on this situation. By modeling in three-dimensional space spanned by unmarked state, marked state and free state to the entire Hilbert space of n qubits, we find Grover iteration can be regarded as improper rotation in the space. This allows us to give formula to solve counting problem. Furthermore, we express initial amplitude distribution in the eigenvector basis of improper rotation matrix. This is necessary to obtain mathematical analysis of counting problem on various situations. Finally, we design four simulation experiments, the results of which show that compared with original quantum counting algorithm, generalized quantum counting algorithm wins great satisfaction from three aspects: (1) Whether initial amplitude distribution is uniform; (2) the diversity of situations on counting problems; and (3) whether phase estimation technique can get phase exactly.
2011-11-01
Crowd Sourcing for the Creation of a Large Scale Annotated Resource for Hindi English Code Switched Data: A Pilot Annotation Mona Diab Center for...We target Hindi English (Hinglish) LCS. We investigate the feasibility of leverag- ing crowd sourcing as a means for anno- tating the data on the...countries like India where Hindi is a common first language (L1) and English acts as a second language (L2) among na- tive Hindi speakers. For
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
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.
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.
Influence of non-uniform intensity distribution of deformed pellicle for N7 patterning
NASA Astrophysics Data System (ADS)
Kim, In-Seon; Kim, Guk-Jin; Yeung, Michael; Barouch, Eytan; Kim, Min-Su; Park, Jin-Goo; Oh, Hye-Keun
2016-09-01
For protecting mask from debris, EUV pellicle is considered as a most effective solution. EUV pellicle can avoid contamination on mask by covering mask. Usage of EUV pellicle can reduce mask damage caused by contamination but the pellicle involves transmission loss due to absorption of EUV light. To get high transmission, pellicle made with thin thickness but it can be deformed easily due to weak structure. Deformation of pellicle such as wrinkle leads transmission non-uniformity and transmission non-uniformity will involve CD non-uniformity. For real-application at lithography process, the optical study of deformed pellicle is required to avoid degradation of CD uniformity. In this paper, we discuss transmission non-uniformity with various off-axis-illumination (OAI) conditions. Then we studied CD nonuniformity caused by wrinkled pellicle with various patterns. By increasing spatial coherence, transmission nonuniformity is decrease at small wrinkle region. However, transmission non-uniformity variation is independent with illumination conditions at large wrinkle which has large period. Not only wrinkled pellicle imaging but also CD variation caused by non-uniform transmission is also dependent on illumination conditions. In contrast with transmission nonuniformity, CD non-uniformity with high coherent light is smaller than the result with low coherent light. With all of results, we find that the allowable local tilt angle is varied with wrinkle size and illumination conditions and smallest size of allowable local tilt angle is about 250 mrad for both illuminations.
Use of Channel Non-uniformity in River Restoration Across Spatial Scales
NASA Astrophysics Data System (ADS)
Pasternack, G. B.
2005-12-01
Linked abiotic-biotic processes in rivers are highly nonlinear and tuned to specific conditions across all spatio-temporal scales. A key aspect of the nonlinearity that has been undervalued in both river science and restoration is the role of channel non-uniformity. As the water depth to bed grain size ratio decreases, channel non-uniformity takes over as a dominant control on hydraulic, geomorphic, and ecologic processes in rivers. Field-based and numerical experiments incorporating channel non-uniformity in hypothesis-driven river restoration projects were conducted to quantify associated aspects of abiotic-biotic linkages. Examples of key non-uniform dynamics relevant to river restoration across a basin that were evaluated include channel-unit self-sustainability, spatial patterns of physical habitat, organism utilization of physical habitat, knickpoint dynamics, and woody debris dynamics. A significant ecological response to restoration projects that incorporated channel non-uniformity was observed. Although inclusion of non-uniformity in river restoration design involves more sophisticated methods than currently practiced, rapid advancements in data collection, management, and analysis methods already enable use of non-uniformity at the sub-reach scale, and will soon enable systemic evaluation over tens of kilometers at the same resolution at which organisms experience a river.
On Shape Normalization for Non-Uniformly Active Catalyst Pellets. III.
1981-10-01
ON SHAPE NORMALIZATION FOR NON-UNIFORMLY ACTIVE CATALYST PELLET--ETC(U) OCT Al M4 MORBIDELLI . A VARMA DAA629 RI C 001 UNCLASSIFIED MRC-TSR-2289 NL 7...RESEARCH CENTRR ON SHAPE NORMALIZATION FOR NON-UNIFORMLY ACTIVE CATALYST PELLETS - III M. Morbidelli and A. Varma Technical Summary Report #2289 October...lies with N4RC, and not with the authors of this report. ON SHAPE NORMALIZATION FOR NON-UNIFORMLY ACTIVE CATALYST PELLETS - III M. Morbidelli and A
The magnetostriction in a superconductor-magnet system under non-uniform magnetic field
NASA Astrophysics Data System (ADS)
Li, Xueyi; Jiang, Lang; Wu, Hao; Gao, Zhiwen
2017-03-01
This paper describes a numerical model to examine the magnetostriction of bulk high-temperature superconductor (HTS) under non-uniform magnetic field in conjunction with finite element analysis. Through this model, the magnetostriction of homogeneous and nonhomogeneous HTS can be implemented under non-uniform magnetic field. Further, the effects of critical current density, applied field frequency and amplitude are also considered. The computational study can provide a fundamental mechanistic understanding the effects of non-uniform magnetic field on magnetostriction of HTS.
Johnston, Kaleena; Jinha, Azim; Herzog, Walter
2016-03-01
The sarcomere length non-uniformity theory (SLNT) is a widely accepted explanation for residual force enhancement (RFE). RFE is the increase in steady-state isometric force following active muscle stretching. The SLNT predicts that active stretching of a muscle causes sarcomere lengths (SL) to become non-uniform, with some sarcomeres stretched beyond actin-myosin filament overlap (popping), causing RFE. Despite being widely known, this theory has never been directly tested. We performed experiments on isolated rabbit muscle myofibrils (n = 12) comparing SL non-uniformities for purely isometric reference contractions (I-state) and contractions following active stretch producing RFE (FE-state). Myofibrils were activated isometrically along the descending limb of the force-length relationship (mean ± 1 standard deviation (SD) = 2.8 ± 0.3 µm sarcomere(-1)). Once the I-state was reached, myofibrils were shortened to an SL on the plateau of the force-length relationship (2.4 µm sarcomere(-1)), and then were actively stretched to the reference length (2.9 ± 0.3 µm sarcomere(-1)). We observed RFE in all myofibrils (39 ± 15%), and saw varying amounts of non-uniformity (1 SD = 0.9 ± 0.5 µm) that was not significantly correlated with the amount of RFE, but through pairwise comparisons was found to be significantly greater than the non-uniformity measured for the I-state (0.7 ± 0.4 µm). Three myofibrils exhibited no increase in non-uniformity. Active stretching was accompanied by sarcomere popping in four myofibrils, and seven had popped sarcomeres in the I-state. These results suggest that, while non-uniformities are present with RFE, they are also present in the I-state. Furthermore, non-uniformity is not associated with the magnitude of RFE, and myofibrils that had no increase in non-uniformity with stretch still showed normal RFE. Therefore, it appears that SL non-uniformity is a normal associate of muscle
Endothelial dysfunction and monocyte recruitment in cells exposed to non-uniform shear stress.
Cicha, Iwona; Goppelt-Struebe, Margarete; Yilmaz, Atilla; Daniel, Werner G; Garlichs, Christoph D
2008-01-01
Atherosclerosis results from a combination of local blood flow patterns and systemic risk factors. We investigated whether non-uniform shear stress at bifurcations induces pro-atherogenic endothelial dysfunction and monocyte recruitment. Bifurcating flow-through cell culture slides were used to expose HUVECs to laminar or non-uniform shear stress for 18 h at 10 dyne/cm(2). For the adhesion assay, HUVECs were subsequently perfused with medium containing THP-1 monocytes for 1 h. Protein expression was determined by immunofluorescence. In areas exposed to laminar shear stress, alignment of endothelial cells with the flow was observed, accompanied by upregulation of eNOS and downregulation of connective tissue growth factor (CTGF). In contrast, cells exposed to non-uniform shear stress near the outer walls of bifurcations were characterized by irregular, unaligned shape, induction of endothelin-1 and CTGF, as well as reduced eNOS expression. These atherogenic effects of non-uniform shear stress were prevented when cells were treated with statins (1 mumol/l) during flow. Under non-uniform shear stress, a slight induction of VCAM-1, ICAM-1, and E-/P-selectin was observed. In agreement with this, monocyte recruitment, which was nearly undetectable under laminar shear stress, was moderately induced by non-uniform shear stress (P<0.02). In conclusion, inhibition of antioxidative eNOS and upregulation of atherogenic proteins is the first step in non-uniform shear stress-mediated endothelial dysfunction, which in vivo in the presence of atherogenic risk factors may further enhance monocyte recruitment into the artery wall.
Non-uniform sampling knife-edge method for camera modulation transfer function measurement
NASA Astrophysics Data System (ADS)
Duan, Yaxuan; Xue, Xun; Chen, Yongquan; Tian, Liude; Zhao, Jianke; Gao, Limin
2016-11-01
Traditional slanted knife-edge method experiences large errors in the camera modulation transfer function (MTF) due to tilt angle error in the knife-edge resulting in non-uniform sampling of the edge spread function. In order to resolve this problem, a non -uniform sampling knife-edge method for camera MTF measurement is proposed. By applying a simple direct calculation of the Fourier transform of the derivative for the non-uniform sampling data, the camera super-sampled MTF results are obtained. Theoretical simulations for images with and without noise under different tilt angle errors are run using the proposed method. It is demonstrated that the MTF results are insensitive to tilt angle errors. To verify the accuracy of the proposed method, an experimental setup for camera MTF measurement is established. Measurement results show that the proposed method is superior to traditional methods, and improves the universality of the slanted knife-edge method for camera MTF measurement.
Modeling and Analysis of Non-Uniform Honeycomb Structures Based on Topology Optimization
NASA Astrophysics Data System (ADS)
Jin, Xin; Li, Guoxi; Zhang, Meng; Gong, Jingzhong
2017-03-01
Honeycomb structure infilling is an important way to achieve lightweight. Focusing on the deficiency of the non-optimized macro-material distribution in uniform honeycomb structures, a modeling method of non-uniform honeycomb structures based on topology optimization was proposed. The loaded component was topology-optimized and the density results were mapped to the relative density matrix of cells. The rapid and automatic modeling of non-uniform honeycomb structures was realized with the using of User-Defined Features and the cyclic definitions of the reference datums. The simulation results show that the mechanic performance of non-uniform honeycomb structures is better than uniform honeycomb structures and the efficiency of the proposed method is validated.
Flux avalanche in a superconducting film with non-uniform critical current density
NASA Astrophysics Data System (ADS)
Lu, Yurong; Jing, Ze; Yong, Huadong; Zhou, Youhe
2016-10-01
The flux avalanche in type-II superconducting thin film is numerically simulated in this paper. We mainly consider the effect of non-uniform critical current density on the thermomagnetic stability. The nonlinear electromagnetic constitutive relation of the superconductor is adopted. Then, Maxwell's equations and heat diffusion equation are numerically solved by the fast Fourier transform technique. We find that the non-uniform critical current density can remarkably affect the behaviour of the flux avalanche. The external magnetic field ramp rate and the environmental temperature have been taken into account. The results are compared with a film with uniform critical current density. The flux avalanche first appears at the interface where the critical current density is discontinuous. Under the same environmental temperature or magnetic field, the flux avalanche occurs more easily for the film with the non-uniform critical current density. The avalanche structure is a finger-like pattern rather than a dendritic structure at low environmental temperatures.
A curvature filter and PDE based non-uniformity correction algorithm
NASA Astrophysics Data System (ADS)
Cheng, Kuanhong; Zhou, Huixin; Qin, Hanlin; Zhao, Dong; Qian, Kun; Rong, Shenghui; Yin, Shimin
2016-10-01
In this paper, a curvature filter and PDE based non-uniformity correction algorithm is proposed, the key point of this algorithm is the way to estimate FPN. We use anisotropic diffusion to smooth noise and Gaussian curvature filter to extract the details of original image. Then combine these two parts together by guided image filter and subtract the result from original image to get the crude approximation of FPN. After that, a Temporal Low Pass Filter (TLPF) is utilized to filter out random noise and get the accurate FPN. Finally, subtract the FPN from original image to achieve non-uniformity correction. The performance of this algorithm is tested with two infrared image sequences, and the experimental results show that the proposed method achieves a better non-uniformity correction performance.
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.
Quasi-mode damping in two-dimensional fully non-uniform coronal loops.
Arregui, I; Van Doorsselaere, T; Andries, J; Goossens, M; Kimpe, D
2006-02-15
Resonantly damped fast kink quasi-modes are computed in fully resistive magnetohydrodynamics for fully non-uniform two-dimensional equilibrium models. The equilibrium model is a straight cylindrically symmetric flux tube with a plasma density that is non-uniform both across and along the loop. The variation of density across the loop can cover the whole loop. Our results indicate that the period and damping of coronal loop oscillations mainly depend on the density contrast and the inhomogeneity length-scale and are independent of the details of longitudinal stratification. This study extends previous studies on coronal loop oscillations, and allows for a better comparison between observations and theory.
NASA Astrophysics Data System (ADS)
Shemer, A.; Schwarz, A.; Gur, E.; Cohen, E.; Zalevsky, Z.
2015-04-01
In this paper, the authors describe a novel technique for image nonlinearity and non-uniformity corrections in imaging systems based on gamma detectors. The limitation of the gamma detector prevents the producing of high quality images due to the radionuclide distribution. This problem causes nonlinearity and non-uniformity distortions in the obtained image. Many techniques have been developed to correct or compensate for these image artifacts using complex calibration processes. The presented method is based on the Papoulis - Gerchberg(PG) iterative algorithm and is obtained without need of detector calibration, tuning process or using any special test phantom.
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.
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.
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
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...
An integral formulation for wave propagation on weakly non-uniform potential flows
NASA Astrophysics Data System (ADS)
Mancini, Simone; Astley, R. Jeremy; Sinayoko, Samuel; Gabard, Gwénaël; Tournour, Michel
2016-12-01
An integral formulation for acoustic radiation in moving flows is presented. It is based on a potential formulation for acoustic radiation on weakly non-uniform subsonic mean flows. This work is motivated by the absence of suitable kernels for wave propagation on non-uniform flow. The integral solution is formulated using a Green's function obtained by combining the Taylor and Lorentz transformations. Although most conventional approaches based on either transform solve the Helmholtz problem in a transformed domain, the current Green's function and associated integral equation are derived in the physical space. A dimensional error analysis is developed to identify the limitations of the current formulation. Numerical applications are performed to assess the accuracy of the integral solution. It is tested as a means of extrapolating a numerical solution available on the outer boundary of a domain to the far field, and as a means of solving scattering problems by rigid surfaces in non-uniform flows. The results show that the error associated with the physical model deteriorates with increasing frequency and mean flow Mach number. However, the error is generated only in the domain where mean flow non-uniformities are significant and is constant in regions where the flow is uniform.
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.
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.
Non-linear effects in a cold electron plasma with non-uniform density profile
NASA Astrophysics Data System (ADS)
Gradov, O. M.; Stenflo, L.; Shukla, P. K.
2008-05-01
A new step forward on the theory for two-dimensional wave propagation is outlined for a non-uniform plasma with a smooth density profile. A way to excite envelope solitary waves with certain shapes is described. The corresponding wave space structure is calculated, and the restrictions on the wave profile along the direction of wave propagation are noticed.
The electrostatic eigenmodes of a cold plasma with a two-dimensional density non-uniformity
NASA Astrophysics Data System (ADS)
Naslund, E.; Gradov, O. M.
1985-10-01
A new kind of surface oscillation, which can exist when the usual surface waves are absent because of resonant absorption, has been studied for a non-uniform plasma slab. Special attention is paid to the influence of the boundaries on the eigenfrequency spectrum.
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.
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, 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, 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...
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...
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.
2009-03-01
DEVELOPMENT OF NON-UNIFORM RADIATION SOLUTION METHODS FOR ATMOSPHERIC RE-ENTRY USING DETAILED THERMAL MODELING THESIS Jeffrey R. Komives, Captain...of the United States Air Force, Department of Defense, or the United States Government. AFIT/GAE/ENY/09-M13 DEVELOPMENT OF NON-UNIFORM RADIATION ...public release; distribution unlimited AFIT/GAE/ENY/ 09-M13 DEVELOPMENT OF NON-UNIFORM RADIATION SOLUTION METHODS FOR ATMOSPHERIC RE-ENTRY USING
An non-uniformity voltage model for proton exchange membrane fuel cell
NASA Astrophysics Data System (ADS)
Li, Kelei; Li, Yankun; Liu, Jiawei; Guo, Ai
2017-01-01
The fuel cell used in transportation has environmental protection, high efficiency and no line traction power system which can greatly reduce line construction investment. That makes it a huge potential. The voltage uniformity is one of the most important factors affecting the operation life of proton exchange membrane fuel cell (PEMFC). On the basis of principle and classical model of the PEMFC, single cell voltage is calculated and the location coefficients are introduced so as to establish a non-uniformity voltage model. These coefficients are estimated with the experimental datum at stack current 50 A. The model is validated respectively with datum at 60 A and 100 A. The results show that the model reflects the basic characteristics of voltage non-uniformity and provides the beneficial reference for fuel cell control and single cell voltage detection.
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
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
1999-01-01
Flame propagation through non-uniformly premixed gases occurs in several common combustion situations. As summarized in a previous conference paper, non-uniform premixed gas combustion has received scant attention compared to the more usual limiting cases of diffusion or uniformly premixed flames. It is the goal of this research to further our knowledge of layered combustion, in which a fuel concentration gradient exists normal to the direction of flame spread, in particular by focusing on the role that gravity plays. Gravity can affect flame propagation in at least three ways: through a hydrostatic pressure gradient, by altering the initial distribution of fuel vapor, and through buoyantly induced flows once ignition has occurred. An understanding of the phenomena involved is important to fire safety, especially aboard spacecraft since no microgravity data exist. The data obtained will also be useful to verify theoretical models of this problem, which are easier to implement if buoyancy is neglected.
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.
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
Atmospheric effects on remote sensing of non-uniform temperature sources
NASA Technical Reports Server (NTRS)
Mcneill, W. A.; Dixon, B. P.
1974-01-01
The effects are considered of an absorbing, emitting, and scattering atmosphere upon the remote sensing of surface areas having non-uniform intensity. These atmospheric effects may be significant in determination, by remote sensing, of non-uniform surface temperature distributions, and the results of the investigation are applicable in such cases. Analytical methods and a digital computational program are presented, expressing the results in terms of contrast and contrast transmittance between two adjacent emitting areas having unequal intensities, in the presence of a additional disturbing emitters. In the computational procedure, emitting areas are replaced by point-source emitters, each assigned and effective intensity based upon the intensity of the area it replaces. Absorbing, emitting, and scattering behavior of the atmosphere may be specified in the computational procedure either by means of analytical atmospheric models or by means of calibrating ground level emitters.
Peristaltic Flow of Couple Stress Fluid in a Non-Uniform Rectangular Duct Having Compliant Walls
NASA Astrophysics Data System (ADS)
Ellahi, R.; Mubashir Bhatti, M.; Fetecau, C.; Vafai, K.
2016-01-01
The present study investigates the peristaltic flow of couple stress fluid in a non-uniform rectangular duct with compliant walls. Mathematical modeling is based upon the laws of mass and linear momentum. Analytic solutions are carried out by the eigen function expansion method under long-wavelength and low-Reynolds number approximations. The features of the flow characteristics are analyzed by plotting the graphs of various values of physical parameters of interest. Trapping bolus scheme is also presented through streamlines.
Lücken, Leonhard; Yanchuk, Serhiy; Popovych, Oleksandr V; Tass, Peter A
2013-01-01
Several brain diseases are characterized by abnormal neuronal synchronization. Desynchronization of abnormal neural synchrony is theoretically compelling because of the complex dynamical mechanisms involved. We here present a novel type of coordinated reset (CR) stimulation. CR means to deliver phase resetting stimuli at different neuronal sub-populations sequentially, i.e., at times equidistantly distributed in a stimulation cycle. This uniform timing pattern seems to be intuitive and actually applies to the neural network models used for the study of CR so far. CR resets the population to an unstable cluster state from where it passes through a desynchronized transient, eventually resynchronizing if left unperturbed. In contrast, we show that the optimal stimulation times are non-uniform. Using the model of weakly pulse-coupled neurons with phase response curves, we provide an approach that enables to determine optimal stimulation timing patterns that substantially maximize the desynchronized transient time following the application of CR stimulation. This approach includes an optimization search for clusters in a low-dimensional pulse coupled map. As a consequence, model-specific non-uniformly spaced cluster states cause considerably longer desynchronization transients. Intriguingly, such a desynchronization boost with non-uniform CR stimulation can already be achieved by only slight modifications of the uniform CR timing pattern. Our results suggest that the non-uniformness of the stimulation times can be a medically valuable parameter in the calibration procedure for CR stimulation, where the latter has successfully been used in clinical and pre-clinical studies for the treatment of Parkinson's disease and tinnitus.
Complex Ginzburg-Landau equation on networks and its non-uniform dynamics
NASA Astrophysics Data System (ADS)
Nakao, Hiroya
2014-10-01
Dynamics of the complex Ginzburg-Landau equation describing networks of diffusively coupled limit-cycle oscillators near the Hopf bifurcation is reviewed. It is shown that the Benjamin-Feir instability destabilizes the uniformly synchronized state and leads to non-uniform pattern dynamics on general networks. Nonlinear dynamics on several network topologies, i.e., local, nonlocal, global, and random networks, are briefly illustrated by numerical simulations.
Gyrokinetic simulations of collisionless reconnection in turbulent non-uniform plasmas
Kobayashi, Sumire; Rogers, Barrett N.; Numata, Ryusuke
2014-04-15
We present nonlinear gyrokinetic simulations of collisionless magnetic reconnection with non-uniformities in the plasma density, the electron temperature, and the ion temperature. The density gradient can stabilize reconnection due to diamagnetic effects but destabilize driftwave modes that produce turbulence. The electron temperature gradient triggers microtearing modes that drive rapid small-scale reconnection and strong electron heat transport. The ion temperature gradient destabilizes ion temperature gradient modes that, like the driftwaves, may enhance reconnection in some cases.
Generalized solutions for a class of non-uniformly elliptic equations in divergence form
Gregori, G.
1997-11-01
We study a general class of quasilinear non-uniformly elliptic pdes in divergence form with linear growth in the gradient. We examine the notions of BV and viscosity solutions and derive for such generalized solutions various a priori pointwise and integral estimates, including a Harnack inequality. In particular we prove that viscosity solutions are unique (on strictly convex domains), are contained in the space BV{sub loc} and are C{sup 1,{alpha}} almost everywhere. 10 refs.
Eigenfrequencies of a bounded plasma with non-uniform density along the boundary
NASA Astrophysics Data System (ADS)
Gradov, O. M.; Stenflo, L.
1984-05-01
The electrostatic surface waves in a cold bounded plasma have been studied for the case where the plasma density is non-uniform in a direction which is parallel to the boundary. It is shown that the eigenmode spectrum then is discrete. The eigenfrequencies, which are functions of the density gradient, are calculated for plane as well as cylindrical geometries. Special attention is paid to the particular case where the density profile is linear.
Non-uniform coupling model of the frustrated chromium-based ring Cr8Ni
NASA Astrophysics Data System (ADS)
Antkowiak, Michał; Kucharski, Łukasz; Kamieniarz, Grzegorz
2014-07-01
A numerically exact spin-Hamiltonian approach has been proposed for the frustrated Cr8Ni molecule. The non-uniform exchange couplings parameters, improving the fit of the experimental magnetic susceptibility data, have been obtained, using a genetic algorithm search procedure. The energy intervals between the lowest multiplets, relevant for envisaged transitions observable in the INS spectra, have been determined and the critical fields corresponding to the first-level crossing have been estimated in agreement with experiment.
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.
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.
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.
[Baseline Correction Algorithm for Raman Spectroscopy Based on Non-Uniform B-Spline].
Fan, Xian-guang; Wang, Hai-tao; Wang, Xin; Xu, Ying-jie; Wang, Xiu-fen; Que, Jing
2016-03-01
As one of the necessary steps for data processing of Raman spectroscopy, baseline correction is commonly used to eliminate the interference of fluorescence spectra. The traditional baseline correction algorithm based on polynomial fitting is simple and easy to implement, but its flexibility is poor due to the uncertain fitting order. In this paper, instead of using polynomial fitting, non-uniform B-spline is proposed to overcome the shortcomings of the traditional method. Based on the advantages of the traditional algorithm, the node vector of non-uniform B-spline is fixed adaptively using the peak position of the original Raman spectrum, and then the baseline is fitted with the fixed order. In order to verify this algorithm, the Raman spectra of parathion-methyl and colza oil are detected and their baselines are corrected using this algorithm, the result is made comparison with two other baseline correction algorithms. The experimental results show that the effect of baseline correction is improved by using this algorithm with a fixed fitting order and less parameters, and there is no over or under fitting phenomenon. Therefore, non-uniform B-spline is proved to be an effective baseline correction algorithm of Raman spectroscopy.
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.
CHF multiplier of subcooled flow boiling for non-uniform heating conditions in swirl tube
Inasaka, F.; Nariai, H.
1994-12-31
The high heat flux components of fusion reactors, such as divertor plates and beam dumps of neutral beam injectors, are estimated to be subjected to very high heat loads more than 10 MW/m{sup 2}. Critical heat flux (CHF), which determines the upper limit of heat removal, is one of the most important problems in designing cooling systems. For practical applications in cooling systems, subcooled flow boiling in water combined with swirl-flow in tubes with internal twisted tape is thought to be the most superior for CHF characteristics in fusion reactor components, heat by irradiation comes in from one side of the wall, and cooling channel is then under circumferentially non-uniform heating condition. Authors have conducted the experiments on the CHF with internal twisted tapes under circumferentially non-uniform heating conditions and showed that when the intensity of non-uniformity increased, q{sub cH} (peak heat flux at burnout under nonuniform heating condition) in tube with internal twisted tape increased above the q{sub c,unif} (CHF under uniform heating condition), though the average qualities were the same for both cases. They also showed that this CHF enhancement was not seen in smooth tubes without tape under the same average qualities.
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.
Non-uniform cosine modulated filter banks using meta-heuristic algorithms in CSD space
Kalathil, Shaeen; Elias, Elizabeth
2014-01-01
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
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%.
A scheme for coupling land surface processes using mutliple non-uniform grid scales
NASA Astrophysics Data System (ADS)
Miller, N. L.; Bastidas, L. A.; Yatheendradas, Y.; Jin, J.; Sorooshian, S.
2003-04-01
Land surface processes respond differently at a range of scales, depending on the sensitivity and the available information for characterizing the parameter space. A multi-scale procedure for coupling a Land Surface Model (LSM) with atmospheric and subsurface processes has been developed. The Non-uniform Grid Scheme (NGS) utilizes hierarchical sub-grids with a high degree of characterization, that are nested within grid-matched coarser grids preserving spatial location. Conservation of mass and momentum is maintained across the grids and aggregated fluxes are computed for the larger scale, which will bi-directionally coupled to a fine-scale regional atmospheric model. Initial studies have shown a shift in the latent and sensible heating rates as the degree of land surface heterogeneity is increased. The Non-uniform Grid Scheme was setup for the NCEP Noah LSM over the San Pedro River Basin in Arizona as a sensitivity study. An analysis using the Noah LSM, in offline fashion, driven with outputs from the NCAR Mesoscale Model (MM5) is presented. Initially, uniform grids with 1, 4, and 9 km resolution are used throughout the domain. This is followed by a multiple resolution grid structure defined by the degree of land surface and sub-surface characteristics of the San Pedro Basin. The influence of the parameter values is also assessed using the default values for semi-arid conditions (uniform for the entire domain) as a benchmark. Grid-dependent non-uniform parameterization is based on a multi-criteria approach using the MOCOM-UA optimization algorithm. Parameter values derived from remote sensing, and values obtained from a combination of remote sensing and parameter optimization techniques are also presented.
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.
Particle size selection in post-spark dusty plasma in non-uniform electric field
NASA Astrophysics Data System (ADS)
Kim, Woongsik; Pikhitsa, Peter V.; Choi, Mansoo
2016-11-01
We report a strong size-selective effect of the non-uniform external electric field on unitary charged nanoparticles in a residual dusty plasma generated by spark discharge. It has been found that the field influences the outcome particle size distribution function considerably by expelling smaller particles out of the residual plasma cloud so that they cannot neutralize or agglomerate. Meantime, larger particles being dragged by the plasma cloud neutralize and disappear at walls; therefore, the particle size distribution function shifts to small sizes. We give a simple theory explaining the field effect and suggest its application for a patterning technique.
The impact of non-uniform capsid charge density on virus assembly
NASA Astrophysics Data System (ADS)
Li, Siyu; Erdemci-Tandogan, Gonca; Wagner, Jef; Zandi, Roya
Many spherical viruses efficiently encapsulate their genome into shells (capsids) with icosahedral symmetry. Under many circumstances, this process is spontaneous and is primarily driven by the electrostatic interaction between positively charged capsid proteins and negatively charged genome. Through the free energy minimization of a generic potential, we calculate the optimal encapsulated genome length. In this talk, I will present our results due to a non-uniform charge distribution on the shell and its impact on the optimal size of encapsulated genome. This work was supported by the National Science Foundation through Grant No. DMR-13-10687.
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.
Accuracy of schemes for the Euler equations with non-uniform meshes
NASA Technical Reports Server (NTRS)
Turkel, E.; Yaniv, S.; Landau, U.
1985-01-01
The effect of non-uniform grids on the solution of the Euler equations is analyzed. A Runge-Kutta type scheme based on a finite volume formulation is considered. It is shown that for arbitrary grids the scheme can be inconsistent even though it is second-order accurate for uniform grids. An improvement is suggested which leads to at least first-order accuracy for general grids. Test cases are presented in both two- and three-space dimensions. Applications to finite difference and implicit algorithms are also given.
A finite volume method for two-sided fractional diffusion equations on non-uniform meshes
NASA Astrophysics Data System (ADS)
Simmons, Alex; Yang, Qianqian; Moroney, Timothy
2017-04-01
We derive a finite volume method for two-sided fractional diffusion equations with Riemann-Liouville derivatives in one spatial dimension. The method applies to non-uniform meshes, with arbitrary nodal spacing. The discretisation utilises the integral definition of the fractional derivatives, and we show that it leads to a diagonally dominant matrix representation, and a provably stable numerical scheme. Being a finite volume method, the numerical scheme is fully conservative, and the ability to locally refine the mesh can produce solutions with more accuracy for the same number of nodes compared to a uniform mesh, as we demonstrate numerically.
Matheny, M.D.; Brown, C.G.; Dyer, S.G.
1994-08-01
DOE Order 5480.11 requires calculation of the effective dose equivalent (EDE) due to non-uniform radiation fields using ICRP-26 weighting factors. To comply with this requirement, Westinghouse Savannah River Company (WSRC) developed a simple dose calculation scheme based on a draft report by the External Dosimetry Working Group of the Health Physics Society Standards Committee. The calculations involved are fairly simple and provide a conservative dose estimate. The resulting EDE estimate provides a much better representation of the risk to the monitored individual than the more prevalent practice of assigning the highest measured dose. Details of the dose assessment methodology are included as an attachment.
A computational model of rat cerebral blood flow using non-uniform rational B-splines.
Pushkin, Sergey V; Podoprigora, Guennady I; Comas, Laurent; Boulahdour, Hatem; Cardot, Jean-Claude; Baud, Michel; Nartsissov, Yaroslav R; Blagosklonov, Oleg
2007-01-01
Non-Uniform Rational B-splines (NURBS) surfaces can be used for a computer simulation of shapes. Some anatomical models of human or animal structures have been recently developed on that basis. We used positron-emission tomography (PET) and computed tomography (CT) data for NURBS modeling of anatomical structures and isotope uptake in the rat brain. Our simplified model of the rat cerebral blood flow is the first step in a larger project aiming a simulation of PET scans in small animals followed by its validation in vivo.
A front-end ASIC design for non-uniformity correction
NASA Astrophysics Data System (ADS)
Shen, X.; Ding, R. J.; Lin, J. M.; Liu, F.
2008-12-01
A front-end design of an ASIC that implements calibration and correction for IRFPA non-uniformity is presented. An algorithm suitable for ASIC implementation is introduced, and one kind of architecture that implements this algorithm has been designed. We map the architecture to TSMC 0.25um process. After evaluating the chip area and operation speed, we confirm that this architect will also be effective when the FPA scale in enlarged to 1Kby1K. Finally the flow of circuit implementation and method of verification are introduced briefly.
Buckling of elastomer sheets under non-uniform electro-actuation.
Bense, Hadrien; Trejo, Miguel; Reyssat, Etienne; Bico, José; Roman, Benoît
2017-04-12
Dielectric elastomer sheets undergo in-plane expansion when stimulated by a transverse electric field. We study experimentally how dielectric plates subjected to a non-uniform voltage distribution undergo buckling instabilities. Two different configurations involving circular plates are investigated: plates freely floating on a bath of water, and plates clamped on a frame. We describe theoretically the out-of-plane deformation of the plates within the framework of weakly non-linear plate equations. This study constitutes a first step of a route to control the 3D activation of dielectric elastomers.
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.
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.
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.
Non-Conservative Instability of Non-uniform Beams Resting on an Elastic Foundation
NASA Astrophysics Data System (ADS)
Lee, S. Y.; Yang, C. C.
1994-01-01
The influence of a Winkler elastic foundation and the slenderness ratio on the non-conservative instability of cantilever non-uniform beams of rectangular cross-section with constant height and linearly varied breadth (T1), constant breadth and linearly varied height (T2) and double taper (T3), subjected to an end concentrated follower force is investigated. It is found that without the elastic foundation the critical flutter load of the non-uniform beam decreases as the taper ratio of the beam is increased. However, when the elastic foundation modulus is greater than a critical value, the critical flutter load of the taper beams is always greater than that of uniform beams. Within the domain considered, when the taper ratio of the beam lies in a certain range, several critical turning points, including a jump phenomenon, may exist for the critical flutter load. The jump mechanism and the influence of the elastic foundation modulus and the slenderness ratio on the jump phenomenon of Timoshenko beams is explored.
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. This work also indicates that to design irradiation-resistant materials, we can avoid void-interface overlap via tuning the configurations of interfaces.
Non-Uniform Contrast and Noise Correction for Coded Source Neutron Imaging
Santos-Villalobos, Hector J; Bingham, Philip R
2012-01-01
Since the first application of neutron radiography in the 1930s, the field of neutron radiography has matured enough to develop several applications. However, advances in the technology are far from concluded. In general, the resolution of scintillator-based detection systems is limited to the $10\\mu m$ range, and the relatively low neutron count rate of neutron sources compared to other illumination sources restricts time resolved measurement. One path toward improved resolution is the use of magnification; however, to date neutron optics are inefficient, expensive, and difficult to develop. There is a clear demand for cost-effective scintillator-based neutron imaging systems that achieve resolutions of $1 \\mu m$ or less. Such imaging system would dramatically extend the application of neutron imaging. For such purposes a coded source imaging system is under development. The current challenge is to reduce artifacts in the reconstructed coded source images. Artifacts are generated by non-uniform illumination of the source, gamma rays, dark current at the imaging sensor, and system noise from the reconstruction kernel. In this paper, we describe how to pre-process the coded signal to reduce noise and non-uniform illumination, and how to reconstruct the coded signal with three reconstruction methods correlation, maximum likelihood estimation, and algebraic reconstruction technique. We illustrates our results with experimental examples.
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.
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
Development and application of a braided river model with non-uniform sediment transport
NASA Astrophysics Data System (ADS)
Sun, Jian; Lin, Binliang; Yang, Haiyan
2015-07-01
This paper presents the development and application of a physics-based morphological model for simulating the evolution processes of braided channels. This model comprises a depth-integrated hydrodynamic sub-model for rapidly varying unsteady flows and a bed load sediment transport sub-model for non-uniform sediments. The sheltering effects of non-uniform particles and the lateral sediment transport due to bed slope and secondary flow are taken into account in the sediment sub-model. Channel bed level change is calculated according to the erosion/deposition rate, and the bank movement is modelled according to the submerged angle of repose, which is valid for braided rivers in natural and experimental conditions. The model has been applied to a braided river produced in a flume experiment, and the numerical model-predicted channel patterns are shown to generally well resemble the experimental river. Most of the morphodynamic processes observed in the experiment can be found in the numerical predictions, including the evolution of the channel from a single straight channel to a multi-thread pattern and local morphologic changes. The mechanisms of the morphodynamic evolution of multi-thread flows are investigated, in which the process of grain sorting occurs under the interaction of fluid and sand, and the effect on channel migration is identified.
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.
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.
Performance tuning non-uniform sampling for sensitivity enhancement of signal-limited biological NMR
Palmer, Melissa R.; Wenrich, Broc R.; Stahlfeld, Phillip
2014-01-01
Non-uniform sampling (NUS) has been established as a route to obtaining true sensitivity enhancements when recording indirect dimensions of decaying signals in the same total experimental time as traditional uniform incrementation of the indirect evolution period. Theory and experiments have shown that NUS can yield up to two-fold improvements in the intrinsic signal-to-noise ratio (SNR) of each dimension, while even conservative protocols can yield 20–40 % improvements in the intrinsic SNR of NMR data. Applications of biological NMR that can benefit from these improvements are emerging, and in this work we develop some practical aspects of applying NUS nD-NMR to studies that approach the traditional detection limit of nD-NMR spectroscopy. Conditions for obtaining high NUS sensitivity enhancements are considered here in the context of enabling 1H,15N-HSQC experiments on natural abundance protein samples and 1H,13C-HMBC experiments on a challenging natural product. Through systematic studies we arrive at more precise guidelines to contrast sensitivity enhancements with reduced line shape constraints, and report an alternative sampling density based on a quarter-wave sinusoidal distribution that returns the highest fidelity we have seen to date in line shapes obtained by maximum entropy processing of non-uniformly sampled data. PMID:24682944
Free-surface flow of liquid oxygen under non-uniform magnetic field
NASA Astrophysics Data System (ADS)
Bao, Shi-Ran; Zhang, Rui-Ping; Wang, Kai; Zhi, Xiao-Qin; Qiu, Li-Min
2017-01-01
The paramagnetic property of oxygen makes it possible to control the two-phase flow at cryogenic temperatures by non-uniform magnetic fields. The free-surface flow of vapor-liquid oxygen in a rectangular channel was numerically studied using the two-dimensional phase field method. The effects of magnetic flux density and inlet velocity on the interface deformation, flow pattern and pressure drop were systematically revealed. The liquid level near the high-magnetic channel center was lifted upward by the inhomogeneous magnetic field. The interface height difference increased almost linearly with the magnetic force. For all inlet velocities, pressure drop under 0.25 T was reduced by 7-9% due to the expanded local cross-sectional area, compared to that without magnetic field. This work demonstrates the effectiveness of employing non-uniform magnetic field to control the free-surface flow of liquid oxygen. This non-contact method may be used for promoting the interface renewal, reducing the flow resistance, and improving the flow uniformity in the cryogenic distillation column, which may provide a potential for enhancing the operating efficiency of cryogenic air separation.
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.
2015-01-01
Interface engineering has become an important strategy for designing radiation-resistant materials. Critical to its success is fundamental understanding of the interactions between interfaces and radiation-induced defects, such as voids. Using transmission electron microscopy, here we report an interesting phenomenon in their interaction, wherein voids adhere to only one side of the bimetal interfaces rather than overlapping them. We show that this asymmetrical void-interface interaction is a consequence of differing surface energies of the two metals and non-uniformity in their interface formation energy. Specifically, voids grow within the phase of lower surface energy and wet only the high-interface energy regions. Furthermore, because this outcome cannot be accounted for by wetting of interfaces with uniform internal energy, our report provides experimental evidence that bimetal interfaces contain non-uniform internal energy distributions. This work also indicates that to design irradiation-resistant materials, we can avoid void-interface overlap via tuning the configurations of interfaces. PMID:26486278
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.
Adhesion of voids to bimetal interfaces with non-uniform energies
Zheng, Shijian; Shao, Shuai; Zhang, Jian; ...
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
Finite volume analysis the thermal behavior of electrode non-uniformity
NASA Astrophysics Data System (ADS)
Ye, Wei-Biao
2017-03-01
Non-uniformity in electrode thickness can result in quality control defectively. To quantitatively detect the non-uniformity of electrode thickness during the manufacturing processes. A heat transfer model based on heat conduction equation has been employed to provide the computational study. The effects of boundary conditions of adiabatic and periodic walls along coating direction, electrode thickness changes from 3.9 to 30.0 %, and two types of located region in thickness changes, as well as anode and cathode material properties on temperature change percents are analyzed and discussed in detail. The relationship between thickness changes percents and temperature change percents of electrode is established. It is found that the thickness changes have a sensitivity of 1 % changes in electrode thickness will result in 1 % in temperature changes at an inherent time point. The selected time points are 0.008 or 0.01 s for cathode and 0.004 s for anode. The minimum thickness change percent 3.9 % will be detected. Further, the comparison of the computational results with experimental ones shows the validity of the heat conduction model.
Shen, Rui; Suuberg, Eric M.
2014-01-01
The transport of volatile organic vapors from subsurface to building involves complex processes. Since the release of the draft subsurface vapor intrusion guidance by the U.S. EPA in 2002, great progress has been made in understanding these processes in various field and modeling studies. In these studies, the importance of analyzing and predicting the subslab volatile organic vapor concentration was noted. To quantitatively predict subslab vapor concentration is, however, complicated, especially for sites located over non-uniform vapor sources. This manuscript provides a method to estimate the vapor concentration beneath the subslab using a closed-form analytical solution that can approximate full three-dimensional modeling results, but does not require the use of advanced numerical simulation. This method allows prediction of the subslab vapor concentration profile beneath the slab for various source configurations, given inputs of building slab dimension and source depth. The interaction of the influences of non-uniform source and the slab capping effect on the subslab vapor concentration is addressed. PMID:24639604
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.
Kong, Xiangqiang; Luo, Zhen; Dong, Hezhong; Eneji, A Egrinya; Li, Weijiang
2012-03-01
A new split-root system was established through grafting to study cotton response to non-uniform salinity. Each root half was treated with either uniform (100/100 mM) or non-uniform NaCl concentrations (0/200 and 50/150 mM). In contrast to uniform control, non-uniform salinity treatment improved plant growth and water use, with more water absorbed from the non- and low salinity side. Non-uniform treatments decreased Na(+) concentrations in leaves. The [Na(+)] in the '0' side roots of the 0/200 treatment was significantly higher than that in either side of the 0/0 control, but greatly decreased when the '0' side phloem was girdled, suggesting that the increased [Na(+)] in the '0' side roots was possibly due to transportation of foliar Na(+) to roots through phloem. Plants under non-uniform salinity extruded more Na(+) from the root than those under uniform salinity. Root Na(+) efflux in the low salinity side was greatly enhanced by the higher salinity side. NaCl-induced Na(+) efflux and H(+) influx were inhibited by amiloride and sodium orthovanadate, suggesting that root Na(+) extrusion was probably due to active Na(+)/H(+) antiport across the plasma membrane. Improved plant growth under non-uniform salinity was thus attributed to increased water use, reduced leaf Na(+) concentration, transport of excessive foliar Na(+) to the low salinity side, and enhanced Na(+) efflux from the low salinity root.
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
Free vibrations of non-uniform CNT/fiber/polymer nanocomposite beams
NASA Astrophysics Data System (ADS)
Seidi, J.; Kamarian, S.
2017-01-01
In this paper, free vibrations of non-uniform multi-scale nanocomposite beams reinforced by carbon nanotubes (CNTs) are studied. Mori-Tanaka (MT) technique is employed to estimate the effective mechanical properties of three-phase CNT/fiber/polymer composite (CNTFPC) beam. In order to obtain the natural frequencies of structure, the governing equation is solved by means of Generalized Differential Quadrature (GDQ) approach. The accuracy and efficiency of the applied methods are studied and compared with some experimental data reported in previous published works. The influences of volume fraction and agglomeration of nanotubes, volume fraction of long fibers, and different laminate lay-ups on the natural frequency response of structure are examined.
Tuning of non-uniform switch toughening in ferroelectric composites by an electric field
NASA Astrophysics Data System (ADS)
Xia, Xiaodong; Zhong, Zheng
2016-10-01
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.
Electromagnetohydrodynamic (EMHD) micropumps under a spatially non-uniform magnetic field
NASA Astrophysics Data System (ADS)
Jian, Yongjun; Chang, Long
2015-05-01
As an effective driven mechanism proved experimentally, magnetohydrodynamic (MHD) micropump has attracted the attentions of many researchers in recent years. In this article, an analytical solution of EMHD velocity of an electrically conducting, incompressible and viscous fluid through a slit microchannel in presence of a lateral uniform electrical field and a spatially non-uniform vertical magnetic field is obtained by using the variation of parameter approach and Gauss numerical integration. In order to verify the validity of the exact solution, Chebyshev spectral collocation method is employed to give the numerical solutions. A very well agreement is reached when the analytical solutions are compared to those obtained by numerical simulation. The dependence of velocity profiles on Hartmann number Ha, electrical field strength parameter S and decay factor A of the magnetic field is interpreted graphically in detail. In addition, the comparison of our analytical results with available experimental data is presented.
Non-uniform spatial response of the LCoS spatial light modulator
NASA Astrophysics Data System (ADS)
Lopez, Víctor; González-Vega, Arturo; Aguilar, Alberto; Landgrave, J. E. A.; García-Márquez, Jorge
2016-05-01
Liquid crystal on silicon (LCoS) spatial light modulators have been considered for a wide variety of scientific applications, due to their phase modulation capability and high spatial resolution. Nevertheless, their intrinsic characteristics, like the extensively studied depolarization and phase shift fluctuations, can make their behavior significantly distant from the ideal and somewhat unpredictable. Here, we present the characterization of a different source of uncertainty: the non-uniform spatial response of the LCoS, which is fundamentally different to the static aberrations of the panel. We measured local deviations of ±22% from the expected phase shift, resulting in non-negligible effects for phase modulation measurements, phase shifting interferometry, wavefront correction, and speckle interferometry.
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.
Generation of Non-Uniform Pulses by an Eight Microstructured Optical Fiber Laser
NASA Astrophysics Data System (ADS)
Ennejah, Tarek; Bahloul, Faouzi; Attia, Rabah
2011-06-01
Mode locking mechanisms in fiber laser have been an active and rich research field in optical communication. In this paper we study the behaviour of an 8FL (eight fiber laser) totally made out of MOF (Microstructured Optical Fiber). We demonstrate that even output from a fiber laser is not necessarily uniform. Due to its ring cavity and NALM (Non linear Amplifying Loop Mirror) transmission properties, the laser generates randomly different non-uniform output pulses. It follows three states of operation: single, bound and multiple pulses were observed. We report the formation of bound pulses where side peaks are higher than the central one. We report also the formation of bound and multiple pulses which damage their bindings and alter their pulses width and separations.
Tunnel FET with non-uniform gate capacitance for improved device and circuit level performance
NASA Astrophysics Data System (ADS)
Alper, C.; De Michielis, L.; Dağtekin, N.; Lattanzio, L.; Bouvet, D.; Ionescu, A. M.
2013-06-01
We report the significant improvement obtained by a non-uniform gate capacitance made by appropriate combination of high-k and low-k regions over the tunneling and the channel regions of a heterostucture TFET (called HKLKTFET). In addition to significantly enhanced ION and subthreshold swing, we find that this structure offers great improvements for the dynamic switching energy (66% saving) and propagation delay (˜3× fast operation) compared to a heterostructure TFET (HeTFET) due to the reduction of the Miller effect. We compare and benchmark the proposed device against a 65 nm low stand-by power (LSTP) CMOS technology, and we show that at a supply voltage of VDD = 0.4 V, TFETs can have smaller propagation delays compared to CMOS operating in the subthreshold region. Higher cut-off frequency (˜3×) and bandwidth for analog applications is observed in circuit-level simulations.
Optimising SD and LSD in Presence of Non-uniform Probabilities of Revocation
NASA Astrophysics Data System (ADS)
D'Arco, Paolo; de Santis, Alfredo
Some years ago two efficient broadcast encryption schemes for stateless receivers, referred to as SD (Subset Difference Method) [NNL01] and LSD (Layered Subset Difference Method) [HS02] , were proposed. They represent one of the most suitable solution to broadcast encryption. In this paper we focus on the following issue: both schemes assume uniform probabilities of revocation of the receivers. However, in some applications, such an assumption might not hold: receivers in a certain area, due to historical and legal reasons, can be considered trustworthy, while receivers from others might exhibit more adversarial behaviours. Can we modify SD and LSD to better fit settings in which the probabilities of revocation are non-uniform?
Faes, Luca; Nollo, Giandomenico; Porta, Alberto
2012-03-01
The complexity of the short-term cardiovascular control prompts for the introduction of multivariate (MV) nonlinear time series analysis methods to assess directional interactions reflecting the underlying regulatory mechanisms. This study introduces a new approach for the detection of nonlinear Granger causality in MV time series, based on embedding the series by a sequential, non-uniform procedure, and on estimating the information flow from one series to another by means of the corrected conditional entropy. The approach is validated on short realizations of linear stochastic and nonlinear deterministic processes, and then evaluated on heart period, systolic arterial pressure and respiration variability series measured from healthy humans in the resting supine position and in the upright position after head-up tilt.
Faes, Luca; Nollo, Giandomenico; Erla, Silvia; Papadelis, Christos; Braun, Christoph; Porta, Alberto
2010-01-01
This study introduces a new approach for the detection of nonlinear Granger causality between dynamical systems. The approach is based on embedding the multivariate (MV) time series measured from the systems X and Y by means of a sequential, non-uniform procedure, and on using the corrected conditional entropy (CCE) as unpredictability measure. The causal coupling from X to Y is quantified as the relative decrease of CCE measured after allowing the series of X to enter the embedding procedure for the description of Y. The ability of the approach to quantify nonlinear causality is assessed on MV time series measured from simulated dynamical systems with unidirectional coupling (the Rössler-Lorenz deterministic system) and bidirectional coupling (two coupled stochastic systems). The method is then applied to real magnetoencephalographic data measured during a visuo-tactile cognitive experiment, showing values of causal coupling consistent with the hypothesis of a cross-processing of different sensory modalities.
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.
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.
Non-uniform Sampling and J-UNIO Automation for Efficient Protein NMR Structure Determination
Didenko, Tatiana; Proudfoot, Andrew; Dutta, Samit Kumar; Serrano, Pedro; Wüthrich, Kurt
2015-01-01
High-resolution structure determination of small proteins in solution is one of the big assets of NMR spectroscopy in structural biology. Improvements in efficiency of NMR structure determination by advances in NMR experiments and automation of data handling therefore attracts continued interest. Here, non-uniform sampling (NUS) of 3D heteronuclear-resolved [1H,1H]-NOESY data yielded two- to three-fold savings of instrument time for structure determinations of soluble proteins. With the 152-residue protein NP_372339.1 from Staphylococcus aureus and the 71-residue protein NP_346341.1 from Streptococcus pneumonia we show that high-quality structures can be obtained with NUS NMR data, which are equally well amenable to robust automated analysis as the corresponding uniformly sampled data. PMID:26227870
Particle-in-Cell Simulations of Collisionless Magnetic Reconnection with a Non-Uniform Guide Field
NASA Astrophysics Data System (ADS)
Wilson, Fiona; Neukirch, Thomas; Hesse, Michael
2016-04-01
Results are presented of a first study of collisionless magnetic reconnection starting from a recently found exact nonlinear force-free Vlasov-Maxwell equilibrium. The initial state has a Harris sheet magnetic field profile in one direction and a non-uniform guide field in a second direction, resulting in a spatially constant magnetic field strength as well as a constant initial plasma density and plasma pressure. It is found that the reconnection process initially resembles guide field reconnection, but that a gradual transition to anti-parallel reconnection happens as the system evolves. The time evolution of a number of plasma parameters is investigated, and the results are compared with simulations starting from a Harris sheet equilibrium and a Harris sheet plus constant guide field equilibrium.
Particle-in-cell simulations of collisionless magnetic reconnection with a non-uniform guide field
NASA Astrophysics Data System (ADS)
Wilson, F.; Neukirch, T.; Hesse, M.; Harrison, M. G.; Stark, C. R.
2016-03-01
Results are presented of a first study of collisionless magnetic reconnection starting from a recently found exact nonlinear force-free Vlasov-Maxwell equilibrium. The initial state has a Harris sheet magnetic field profile in one direction and a non-uniform guide field in a second direction, resulting in a spatially constant magnetic field strength as well as a constant initial plasma density and plasma pressure. It is found that the reconnection process initially resembles guide field reconnection, but that a gradual transition to anti-parallel reconnection happens as the system evolves. The time evolution of a number of plasma parameters is investigated, and the results are compared with simulations starting from a Harris sheet equilibrium and a Harris sheet plus constant guide field equilibrium.
Numerical prediction of marine propeller noise in non-uniform inflow
NASA Astrophysics Data System (ADS)
Pan, Yu-cun; Zhang, Huai-xin
2013-03-01
A numerical study on the acoustic radiation of a propeller interacting with non-uniform inflow has been conducted. Real geometry of a marine propeller DTMB 4118 is used in the calculation, and sliding mesh technique is adopted to deal with the rotational motion of the propeller. The performance of the DES (Detached Eddy Simulation) approach at capturing the unsteady forces and moments on the propeller is compared with experiment. Far-field sound radiation is predicted by the formation 1A developed by Farassat, an integral solution of FW-H (Ffowcs Williams-Hawkings) equation in time domain. The sound pressure and directivity patterns of the propeller operating in two specific velocity distributions are discussed.
Novel cone lasing emission in a non-uniform one-dimensional photonic crystal
NASA Astrophysics Data System (ADS)
Li, Yi; Zhou, Wen-Yuan; Ying, Cui-Feng; Yang, Na; Chen, Shao-Jie; Ye, Qing; Tian, Jian-Guo
2015-06-01
Novel cone lasing emission is observed from a photonic crystal (PC) with graded layers, which is fabricated by two-beam holographic interference in dichromated gelatin. The cone lasing is composed of one lasing spot and one concentric lasing ring. The good agreement between the experimental results and a numerical simulation performed using the transfer matrix method demonstrates that this lasing ring is induced by the coupling between the band edge and minigap, which is represented as some oscillations near the band edge in the passband of the reflection spectrum. The cone lasing may be useful for multi-wavelength fluorescence detection since the dual-colour directional enhanced fluorescence can be achieved without the mutual interference of lasing modes. Moreover, this readily observable cone lasing provides a direct visualization of the dispersion relation of non-uniform PCs.
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.
Slow polarization relaxation in non-uniform telluric acid ammonium phosphate crystals.
Matyjasek, K; Rogowski, R Z
2006-08-16
The characteristic features of polarization and spontaneous depolarization kinetics in non-uniform telluric acid ammonium phosphate (TAAP) crystals are investigated by observation of the domain structure using a nematic liquid crystal method. We present experimental results showing the correlation between the internal bias field, responsible for the offset of the hysteresis loop and the backswitching process. The internal field caused by structural disorder accounts for a broad spectrum of energy barriers for domain nucleation. The switching kinetics was analysed in the framework of the nucleation and growth model based on Avrami statistical theory, using the modified Kolmogorov-Avrami-Ishibashi (KAI) model. It has been found that the switching kinetics in TAAP crystals can be approximated by averaging the KAI model over a broad distribution of characteristic domain growth times. The spectra of the distribution of the characteristic domain growth times are derived from the experimental data.
NASA Astrophysics Data System (ADS)
Tepegoz, Murat; Akin, Tayfun
2007-04-01
This paper proposes a new resistance non-uniformity correction method for microbolometer-type uncooled thermal detector focal plane arrays (FPAs) that suffer from pixel-to-pixel resistance variation, which is conventionally corrected by applying a specific bias voltage to each detector by the use on-chip DACs. The proposed method uses the heating of the detector with electrical bias, where the detector is heated-up for a pre-determined period of time before the read-out phase. The proposed method uses only a heat-up signal source and simple digital blocks for each column, eliminating the need for DACs that occupy large area, contribute to the noise floor of the system, and dissipate extra power. The proposed method provides a detector current resolution of 14.5 nA with 9-bit digital data, which corresponds to the resolution of 12-bit DAC used in conventional methods.
Improvement of brain segmentation accuracy by optimizing non-uniformity correction using N3.
Zheng, Weili; Chee, Michael W L; Zagorodnov, Vitali
2009-10-15
Smoothly varying and multiplicative intensity variations within MR images that are artifactual, can reduce the accuracy of automated brain segmentation. Fortunately, these can be corrected. Among existing correction approaches, the nonparametric non-uniformity intensity normalization method N3 (Sled, J.G., Zijdenbos, A.P., Evans, A.C., 1998. Nonparametric method for automatic correction of intensity nonuniformity in MRI data. IEEE Trans. Med. Imag. 17, 87-97.) is one of the most frequently used. However, at least one recent study (Boyes, R.G., Gunter, J.L., Frost, C., Janke, A.L., Yeatman, T., Hill, D.L.G., Bernstein, M.A., Thompson, P.M., Weiner, M.W., Schuff, N., Alexander, G.E., Killiany, R.J., DeCarli, C., Jack, C.R., Fox, N.C., 2008. Intensity non-uniformity correction using N3 on 3-T scanners with multichannel phased array coils. NeuroImage 39, 1752-1762.) suggests that its performance on 3 T scanners with multichannel phased-array receiver coils can be improved by optimizing a parameter that controls the smoothness of the estimated bias field. The present study not only confirms this finding, but additionally demonstrates the benefit of reducing the relevant parameter values to 30-50 mm (default value is 200 mm), on white matter surface estimation as well as the measurement of cortical and subcortical structures using FreeSurfer (Martinos Imaging Centre, Boston, MA). This finding can help enhance precision in studies where estimation of cerebral cortex thickness is critical for making inferences.
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.
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.
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
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.
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.
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
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
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
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
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)
Gladilin, Evgeny; Eils, Roland
2009-02-01
Unsupervised analysis of time-series of live-cell images is one of the important tools of quantitative biology. Due to permanent cell motility or displacements of subcellular structures, microscopic images exhibit intrinsic non-uniform motion. In this article, we present a novel approach for detection of non-uniform multi-body motion which is based on combination of the Fourier-phase correlation with iterative probing target and background image regions similar to the strategy known from saccadic eye movements. We derive theoretical expressions that yield plausible explanation why this strategy turns out to be advantageous for tracking particular image pattern. Our experiments with synthetic and live-cell images demonstrate that the proposed approach is capable of accurately detecting non-uniform motion in synthetic and live-cell images.
Schunk, Peter Randall; King, William P. (Georgia Institute of Technology, Atlanta, GA); Sun, Amy Cha-Tien; Rowland, Harry D.
2007-08-01
This paper presents continuum simulations of viscous polymer flow during nanoimprint lithography (NIL) for embossing tools having irregular spacings and sizes. Simulations varied non-uniform embossing tool geometry to distinguish geometric quantities governing cavity filling order, polymer peak deformation, and global mold filling times. A characteristic NIL velocity predicts cavity filling order. In general, small cavities fill more quickly than large cavities, while cavity spacing modulates polymer deformation mode. Individual cavity size, not total filling volume, dominates replication time, with large differences in individual cavity size resulting in non-uniform, squeeze flow filling. High density features can be modeled as a solid indenter in squeeze flow to accurately predict polymer flow and allow for optimization of wafer-scale replication. The present simulations make it possible to design imprint templates capable of distributing pressure evenly across the mold surface and facilitating symmetric polymer flow over large areas to prevent mold deformation and non-uniform residual layer thickness.
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.
A new splitting scheme to the discrete Boltzmann equation for non-ideal gases on non-uniform meshes
NASA Astrophysics Data System (ADS)
Patel, Saumil; Lee, Taehun
2016-12-01
We present a novel numerical procedure for solving the discrete Boltzmann equations (DBE) on non-uniform meshes. Our scheme is based on the Strang splitting method where we seek to investigate two-phase flow applications. In this note, we investigate the onset of parasitic currents which arise in many computational two-phase algorithms. To the best of our knowledge, the results presented in this work show, for the first time, a spectral element discontinuous Galerkin (SEDG) discretization of a discrete Boltzmann equation which successfully eliminates parasitic currents on non-uniform meshes. With the hope that this technique can be used for applications in complex geometries, calculations are performed on non-uniform mesh distributions by using high-order (spectral), body-fitting quadrilateral elements. Validation and verification of our work is carried out by comparing results against the classical 2D Young-Laplace law problem for a static drop.
NASA Astrophysics Data System (ADS)
Chen, Qicheng; Ma, Jie; Wang, Bingbing; Zhang, Yingjin
2016-11-01
Molecular dynamics simulations are performed to investigate the nano-droplets coalescence process in a non-uniform electric field. Coalescence of droplets driven by dielectrophoresis (DEP) could be observed clearly in a strong electric field. The efficiency of coalescence is remarkably improved about 2 times for non-uniform electric field as much as the efficiency for the uniform electric field. Increasing the gradient of the field, it is found that the DEP force will accelerate the droplets motion of coalescence. But when the gradient of the field increases to a certain degree, the DEP force acting on the droplets presents strongly and rapidly nonlinear increasing and induces the droplets forming the chain structure due to intensively elongating. Moreover, the average operating voltages is much lower in non-uniform electric field.
Ying, Jinfa; Delaglio, Frank; Torchia, Dennis A; Bax, Ad
2016-11-19
Implementation of a new algorithm, SMILE, is described for reconstruction of non-uniformly sampled two-, three- and four-dimensional NMR data, which takes advantage of the known phases of the NMR spectrum and the exponential decay of underlying time domain signals. The method is very robust with respect to the chosen sampling protocol and, in its default mode, also extends the truncated time domain signals by a modest amount of non-sampled zeros. SMILE can likewise be used to extend conventional uniformly sampled data, as an effective multidimensional alternative to linear prediction. The program is provided as a plug-in to the widely used NMRPipe software suite, and can be used with default parameters for mainstream application, or with user control over the iterative process to possibly further improve reconstruction quality and to lower the demand on computational resources. For large data sets, the method is robust and demonstrated for sparsities down to ca 1%, and final all-real spectral sizes as large as 300 Gb. Comparison between fully sampled, conventionally processed spectra and randomly selected NUS subsets of this data shows that the reconstruction quality approaches the theoretical limit in terms of peak position fidelity and intensity. SMILE essentially removes the noise-like appearance associated with the point-spread function of signals that are a default of five-fold above the noise level, but impacts the actual thermal noise in the NMR spectra only minimally. Therefore, the appearance and interpretation of SMILE-reconstructed spectra is very similar to that of fully sampled spectra generated by Fourier transformation.
Hu, Zheng; Lin, Jun; Chen, Zhong-Sheng; Yang, Yong-Min; Li, Xue-Jun
2015-01-22
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.
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
NASA Astrophysics Data System (ADS)
Bury, Tomasz; Składzień, Jan; Widziewicz, Katarzyna
2010-10-01
The work deals with experimental and numerical thermodynamic analyses of cross-flow finned tube heat exchangers of the gas-liquid type. The aim of the work is to determine an impact of the gas non-uniform inlet on the heat exchangers performance. The measurements have been carried out on a special testing rig and own numerical code has been used for numerical simulations. Analysis of the experimental and numerical results has shown that the range of the non-uniform air inlet to the considered heat exchangers may be significant and it can significantly affect the heat exchanger efficiency.
Non-uniform Composition Profiles in Inorganic Thin Films from Aqueous Solutions.
Fairley, Kurtis C; Merrill, Devin R; Woods, Keenan N; Ditto, Jeffrey; Xu, Can; Oleksak, Richard P; Gustafsson, Torgny; Johnson, Darren W; Garfunkel, Eric L; Herman, Gregory S; Johnson, David C; Page, Catherine J
2016-01-13
A variety of metal oxide films (InGaOx, AlOx, "HafSOx") prepared from aqueous solutions were found to have non-uniform electron density profiles using X-ray reflectivity. The inhomogeneity in HafSOx films (Hf(OH)4-2x-2y(O2)x(SO4)y·zH2O), which are currently under investigation as inorganic resists, were studied in more detail by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and medium-energy ion scattering (MEIS). The HAADF-STEM images show a greater concentration of heavy atoms near the surface of a single-layer film. MEIS data confirm the aggregation of Hf at the film surface. The denser "crust" layer in HafSOx films may directly impact patterning resolution. More generally, the phenomenon of surface-layer inhomogeneity in solution-deposited films likely influences film properties and may have consequences in other thin-film systems under investigation as resists, dielectrics, and thin-film transistor components.
Large sized non-uniform sediment transport at high capacity on steep slopes
NASA Astrophysics Data System (ADS)
Fu, X.; Zhang, L.; Duan, J. G.
2015-12-01
Transport of large-sized particles such as cobbles in steep streams still remains poorly understood in spite of its importance in mountain stream morphdynamics. Here we explored the law of cobble transport and the effect of cobble existence on gravel bed material transport, using flume experiments with a steep slope (4.9%) and water and sediment constantly supplying. The experiments were conducted in an 8 m long and 0.6 m wide circulating flume with the maximal size up to 90 mm and cobble concentrations in the sediment bed ranging from 22 percent to 6 percent. The sediment transport rate is on the order of 1000 g/m/s, which could be taken as high rate transport compared with existing researches. Bed load transport rate and flow variables were measured after the flume reached an equilibrium state. Bed surface topography was also measured by applying Kinect range camera before and after each run in order to analyze the fractal characteristics of the bed surface under different flow conditions. Critical shear stress of each size friction was estimated from the reference transport method (RTM) and a new hiding function was recommended. Preliminary results show that the bed was nearly in an equal mobility transport regime. We then plot dimensionless fractional transport rate versus dimensionless shear stress and assess the existing bed load transport formulas of non-uniform sediments for their applicability at high sediment transport capacity. This study contributes to the comprehension of high rate sediment transport on steep slopes.
Spontaneous formation of non-uniform double helices for elastic rods under torsion
NASA Astrophysics Data System (ADS)
Li, Hongyuan; Zhao, Shumin; Xia, Minggang; He, Siyu; Yang, Qifan; Yan, Yuming; Zhao, Hanqiao
2017-02-01
The spontaneous formation of double helices for filaments under torsion is common and significant. For example, the research on the supercoiling of DNA is helpful for understanding the replication and transcription of DNA. Similar double helices can appear in carbon nanotube yarns, cables, telephone wires and so forth. We noticed that non-uniform double helices can be produced due to the surface friction induced by the self-contact. Therefore an ideal model was presented to investigate the formation of double helices for elastic rods under torque. A general equilibrium condition which is valid for both the smooth surface and the rough surface situations is derived by using the variational method. By adding further constraints, the smooth and rough surface situations are investigated in detail respectively. Additionally, the model showed that the specific process of how to twist and slack the rod can determine the surface friction and hence influence the configuration of the double helix formed by rods with rough surfaces. Based on this principle, a method of manufacturing double helices with designed configurations was proposed and demonstrated. Finally, experiments were performed to verify the model and the results agreed well with the theory.
Regional paleofire regimes affected by non-uniform climate, vegetation and human drivers
NASA Astrophysics Data System (ADS)
Blarquez, Olivier; Ali, Adam A.; Girardin, Martin P.; Grondin, Pierre; Fréchette, Bianca; Bergeron, Yves; Hély, Christelle
2015-09-01
Climate, vegetation and humans act on biomass burning at different spatial and temporal scales. In this study, we used a dense network of sedimentary charcoal records from eastern Canada to reconstruct regional biomass burning history over the last 7000 years at the scale of four potential vegetation types: open coniferous forest/tundra, boreal coniferous forest, boreal mixedwood forest and temperate forest. The biomass burning trajectories were compared with regional climate trends reconstructed from general circulation models, tree biomass reconstructed from pollen series, and human population densities. We found that non-uniform climate, vegetation and human drivers acted on regional biomass burning history. In the open coniferous forest/tundra and dense coniferous forest, the regional biomass burning was primarily shaped by gradual establishment of less climate-conducive burning conditions over 5000 years. In the mixed boreal forest an increasing relative proportion of flammable conifers in landscapes since 2000 BP contributed to maintaining biomass burning constant despite climatic conditions less favourable to fires. In the temperate forest, biomass burning was uncoupled with climatic conditions and the main driver was seemingly vegetation until European colonization, i.e. 300 BP. Tree biomass and thus fuel accumulation modulated fire activity, an indication that biomass burning is fuel-dependent and notably upon long-term co-dominance shifts between conifers and broadleaf trees.
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.
Comprehensive analysis of particle motion under non-uniform AC electric fields in a microchannel.
Oh, Jonghyun; Hart, Robert; Capurro, Jorge; Noh, Hongseok Moses
2009-01-07
AC electrokinetics is rapidly becoming a foundational tool for lab-on-a-chip systems due to its versatility and the simplicity of the components capable of generating them. Predicting the behavior of fluids and particles under non-uniform AC electric fields is important for the design of next generation devices. Though there are several important phenomena that contribute to the overall behavior of particles and fluids, current predictive techniques consider special conditions where only a single phenomenon may be considered. We report a 2D numerical simulation, using COMSOL Multiphysics, which incorporates the three major AC electrokinetic phenomena (dielectrophoresis, AC electroosmosis and electrothermal effect) and is valid for a wide range of operational conditions. Corroboration has been performed using experimental conditions that mimic those of the simulation and shows good qualitative agreement. Furthermore, a broad range of experiments has been performed using four of the most widely reported devices under varying conditions in order to show their behavior as it relates to the simulation. The large number of experimental conditions reported, together with the comprehensive numerical simulation, will help provide guidelines for scientists and engineers interested in incorporating AC electrokinetics into their lab-on-a-chip systems.
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.
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
NASA Astrophysics Data System (ADS)
Mourtzios, Ch.; Siakavara, K.
2015-08-01
A method to design hybrid antenna configurations with very low profile, suitable for smart and Multiple Input-Multiple Output antenna systems is proposed. The antennas are incorporated with novel Electromagnetic Band Gap (EBG) surfaces with non-similar cells. These non-uniform EBG surfaces have been properly designed to cause focusing, of the incident waves, thus enhancing the characteristics of operation of antenna elements positioned in close proximity to the surface and also to increase the isolation between them. Theoretical analysis of the reflection mechanism of this type of lattices as well as the prediction of the resulting performance of the antenna is presented. All these considerations are validated with implementation and simulation of the hybrid structures inside the Universal Mobile Telecommunications System frequency band. The results show that increment of the gain and isolation between the antenna elements can be obtained. Moreover, results for the correlation coefficient between the elements, for Gaussian distribution of the incoming waves have been received and the tolerance of the antennas to the variation of the polarization characteristics of the incoming waves has been investigated. A Genetic Algorithm has been constructed and applied to find the proper geometry of the hybrid antennas in order the correlation coefficient to be minimized and get almost independent from the polarization of incident waves.
Fermionic and Majorana bound states in hybrid nanowires with non-uniform spin-orbit interaction
NASA Astrophysics Data System (ADS)
Klinovaja, Jelena; Loss, Daniel
2015-03-01
We study intragap bound states in the topological phase of a Rashba nanowire in the presence of a magnetic field and with non-uniform spin orbit interaction (SOI) and proximity-induced superconductivity gap. We show that fermionic bound states (FBS) can emerge inside the proximity gap. They are localized at the junction between two wire sections characterized by different directions of the SOI vectors, and they coexist with Majorana bound states (MBS) localized at the nanowire ends. The energy of the FBS is determined by the angle between the SOI vectors and the lengthscale over which the SOI changes compared to the Fermi wavelength and the localization length. We also consider double-junctions and show that the two emerging FBSs can hybridize and form a double quantum dot-like structure inside the gap. We find explicit analytical solutions of the bound states and their energies for certain parameter regimes such as weak and strong SOI. The analytical results are confirmed and complemented by an independent numerical tight-binding model approach. Such FBS can act as quasiparticle traps and thus can have implications for topological quantum computing schemes based on braiding MBSs.
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. PMID:27601981
Intensity non-uniformity correction of aerothermal images via ℓ_{p}-regularized minimization.
Liu, Li; Zhang, Tianxu
2016-11-01
Aerothermal-induced intensity non-uniformity (NU) effects severely influence the effective performance of infrared (IR) imaging systems in high-speed flight. In this paper we propose a ℓ_{p}-regularized minimization method to remove intensity NU in IR images. Different from the existing NU correction methods, we consider and study important priors from the NU noise and the IR image, respectively. We assume spatial smoothness of the NU noise and piecewise continuity of the IR image, where the ℓ_{p} regularization term is employed in the correction model. A computationally efficient numerical algorithm based on half-quadratic regularization is adopted to solve the optimization problem. To tackle the non-convex ℓ_{p}-norm minimization sub-problem in this scheme, a generalized iterated shrinkage algorithm is used. Significant improvement on the image quality is obtained on both simulation and experimental studies. Both quantitative and qualitative comparisons to specialized state-of-the-art algorithms demonstrate its superiority.
PDEGEM: Modeling non-uniform read distribution in RNA-Seq data
2015-01-01
Background RNA-Seq is a powerful new technology to comprehensively analyze the transcriptome of any given cells. An important task in RNA-Seq data analysis is quantifying the expression levels of all transcripts. Although many methods have been introduced and much progress has been made, a satisfactory solution remains be elusive. Results In this article, we borrow the idea from the Positional Dependent Nearest Neighborhood (PDNN) model, originally developed for analyzing microarray data, to model the non-uniformity of read distribution in RNA-seq data. We propose a robust nonlinear regression model named PDEGEM, a Positional Dependent Energy Guided Expression Model to estimate the abundance of transcripts. Using real data, we find that the PDEGEM fits the data better than mseq in all three real datasets we tested. We also find that the expression measure obtained using PDEGEM showed higher correlation with that obtained from alterative assays for quantifying gene and isoform expressions. Conclusions Based on these results, we believe that our PDEGEM can improve the accuracy in modeling and estimating the transcript abundance and isoform expression in RNA-Seq data. Additionally, although the stacking energy and positional weight of the PDEGEM are relatively related to sequencing platforms and species, they share some common trends, which indicates that the PDEGEM could partly reflect the mechanism of DNA binding between the template strain and the new synthesized read. The PDEGEM model can be freely downloaded at: http://www.math.pku.edu.cn/teachers/dengmh/PDEGEM. PMID:26044773
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
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.
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
Non-Maxwellian effects in underdense plasmas heated by non-uniform laser beams
NASA Astrophysics Data System (ADS)
Matte, Jean-Pierre
2005-10-01
The collisionl heating of plasmas by intense laser beams is known to drive the electron distribution function into a super-Gaussian [1] or ``DLM'' [2] shape. This reduces the absorption [1], and the reduction is stronger if the beam is very non-uniform, for a given average intensity, as there is a depletion of slow electrons, compared to a Maxwellian of the same density and average energy. If the beam irradiates most or a good fraction of the plasma volume, these non-Maxwellian effects also imply a depletion of high energy electrons, with the resulting strong reduction of Landau damping of Langmuir waves [2], contrary to the results of Brunner and Valeo [3] which were obtained in the limit of a narrow beam heating a wide plasma. The depletion of fast electrons depends essentially on the average laser intensity. We will show how these two aspects vary with the laser and plasma parameters.[1] A.B. Langdon, Phys. Rev. Lett. 44, 575 (1980) [2] B.B. Afeyan, A.E. Chou, J.P. Matte et al., Phys. Rev. Lett. 80, 2322 (1998). [3] S. Brunner and E. Valeo, Phys. Plasmas 9, 923 (2002).
Deformations of a pre-stretched elastic membrane driven by non-uniform electroosmotic flow
NASA Astrophysics Data System (ADS)
Bercovici, Moran; Boyko, Evgeniy; Gat, Amir
2016-11-01
We study viscous-elastic dynamics of fluid confined between a rigid plate and a pre-stretched elastic membrane subjected to non-uniform electroosmotic flow, and focus on the case of a finite-size membrane clamped at its boundaries. Considering small deformations of a strongly pre-stretched membrane, and applying the lubrication approximation for the flow, we derive a linearized leading-order non-homogenous 4th order diffusion equation governing the deformation and pressure fields. We derive a time-dependent Green's function for a rectangular domain, and use it to obtain several basic solutions for the cases of constant and time varying electric fields. In addition, defining an asymptotic expansion where the small parameter is the ratio of the induced to prescribed tension, we obtain a set of four one-way coupled equations providing a first order correction for the deformation field. Funded by the European Research Council (ERC) under the Horizon 2020 Research and Innovation Programme, Grant agreement No. 678734 (MetamorphChip).
Laminar mixed convection in horizontal concentric annuli with non-uniform circumferential heating
NASA Astrophysics Data System (ADS)
Habib, M. A.; Negm, A. A. A.
Steady, laminar, mixed convection in the fully developed region of horizontal concentric annuli has been investigated numerically for the case of non-uniform circumferential heating. Two heating conditions were studied, one in which a 180∘ arc encompassing the top half of inner surface of the inner cylinder is uniformly heated while the bottom half is kept insulated, and the other in which the heated and the insulated surfaces were reversed. The fluid flow and heat transfer characteristics were found to be affected by the heating conditions. For the investigated range of the governing buoyancy parameter, the modified Grashof number (Gr*), it was found that bottom heating arrangement gives rise to a vigorous secondary flow, with the result that the average Nusselt numbers are much higher than those for pure forced convection. On the other hand, the local Nusselt numbers are nearly circumferentially uniform. In the case of top heating arrangement, a less vigorous secondary flow is induced because of temperature stratification, with average Nusselt numbers that are substantially lower than those for bottom heating and with large circumferential variation of the local Nusselt number.
Spectral non-uniform temperature and non-local heat transfer in the spin Seebeck effect.
Tikhonov, Konstantin S; Sinova, Jairo; Finkel'stein, Alexander M
2013-01-01
Recently discovered spin-dependent thermoelectric effects have merged spin, charge, and thermal physics, known as spin caloritronics, of which the spin Seebeck effect is its most puzzling. Here we present a theory of this effect driven by subthermal non-local phonon heat transfer and spectral non-uniform temperature. The theory explains its non-local behaviour from the fact that phonons that store the energy (thermal) and the phonons that transfer it (subthermal) are located in different parts of the spectrum and have different kinetics. This gives rise to a spectral phonon distribution that deviates from local equilibrium along the substrate and is sensitive to boundary conditions. The theory also predicts a non-magnon origin of the effect in ferromagnetic metals in agreement with observations in recent experiments. Equilibration of the heat flow from the substrate to the Pt probe and backwards leads to a vertical spin current produced by the spin-polarized electrons dragged by the thermal phonons.
Lattice Boltzmann Explicit Schemes for 3D MHD on Non-Uniform Grids
NASA Astrophysics Data System (ADS)
Schleif, C.; Vahala, G.; Vahala, L.; Macnab, A.; Soe, M.; Carter, J.
2004-11-01
Lattice-Boltzmann Model (LBM) is a very promising alternative computational approach to MHD and to other nonlinear macroscopic systems because of its simplicity, ease of imposition of geometric boundary conditions and ideal parallelization on multi-PE (and especially vector) platforms. For example, on the Earth Simulator our 2D explicit LBM-MHD code has achieved over 3.6 TFlops/sec. The disparate length and time scales that appear in the solutions of dissipative MHD require careful treatment of ill-conditioned matrices in direct solvers. In LBM-MHD one introduces a scalar distribution function for the velocity field and a vector distribution function for the magnetic field. Since the magnetic evolution equation is obtained at the 1st moment closures, less speeds are needed than to recover the momentum equation. We are also investigating the least square LBM for non-uniform spatial grids. In one approach, the standard LBM is applied to the fine scales while the least square LBM is applied to the large scales. Since the least square algorithm involves matrices that are only grid-dependent, these matrices need only be calculated once leading to an efficient algorithm. Our algorithm will be applied to the 3D Orszag-Tang vortex and compare our results to the 3D pseudo-spectral results of Poquet et. al.
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.
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.
Neural network based near- lossless compression of EEG signals with non uniform quantization.
Sriraam, N
2007-01-01
Efficient compression technique is highly essential for the transmission and storage of large amount of biomedical signals. In this paper, a near- lossless scheme for the compression of EEG signals using artificial neural networks is proposed. The error (residue) signals which is obtained due to the difference between the original and the predicted EEG signals are thresolded based on a term referred as absolute error limit (AEL) such that, any error samples above the limit require more number of bits than the samples below the limit that require less number of bits. The thresholded error samples are quantized in a non-uniform manner by varying the actual bits assigned to the error samples. An arithmetic encoder is further used to improve the compression efficiency. Three adaptive neural network models, namely, single and multilayer perceptrons and Elman neural network and two classical adaptive predictors such as autoregressive model(AR) and normalized least mean-square FIR filter are used. EEG signals recorded under different physiological conditions are considered and the performance of the proposed scheme is evaluated in terms of compression ratio and the fidelity parameter, percent of root-mean-square-difference (PRD). It is found from the experimental results that the variation of error limit and quantization step decides the overall compression performance. Single- layer perceptron yields the best compression results in terms of utilizing less bit rate as well achieving low PRD values compared to other predictors.
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.
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
Dynamic strain measurements of marine propellers under non-uniform inflow
NASA Astrophysics Data System (ADS)
Tian, Jin; Croaker, Paul; Zhang, Zhiyi; Hua, Hongxing
2016-09-01
An experimental investigation was conducted to determine the dynamic strain characteristics of marine propellers under non-uniform inflow. Two 7-bladed highly skewed model propellers of identical geometries, but different elastic characteristics were tested at various rotational speeds and free stream velocities in the water tunnel. Two kinds of wire mesh wake screens located 400mm upstream of the propeller plane were used to generate four-cycle and six-cycle inflows. A laser doppler velocimetry (LDV) system located 100mm downstream of the wake screen plane was used to measure the axial velocity distributions produced by the wake screens. Strain gauges were bonded onto the propeller blades in different positions. A customized underwater data acquisition system which can record data off-line was used to record the dynamic strain. The results show that the frequency properties of the blade dynamic strain are determined by the harmonics of the inflow and that the stiffness of the propeller has an essential effect on the dynamic strain amplitudes.
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.
Non-uniform muscle fat replacement along the proximodistal axis in Duchenne muscular dystrophy.
Hooijmans, M T; Niks, E H; Burakiewicz, J; Anastasopoulos, C; van den Berg, S I; van Zwet, E; Webb, A G; Verschuuren, J J G M; Kan, H E
2017-02-21
The progressive replacement of muscle tissue by fat in Duchenne muscular dystrophy (DMD) has been studied using quantitative MRI between, but not within, individual muscles. We studied fat replacement along the proximodistal muscle axis using the Dixon technique on a 3T MR scanner in 22 DMD patients and 12 healthy controls. Mean fat fractions per muscle per slice for seven lower and upper leg muscles were compared between and within groups assuming a parabolic distribution. Average fat fraction for a small central slice stack and a large coverage slice stack were compared to the value when the stack was shifted one slice (15 mm) up or down. Higher fat fractions were observed in distal and proximal muscle segments compared to the muscle belly in all muscles of the DMD subjects (p <0.001). A shift of 15 mm resulted in a difference in mean fat fraction which was on average 1-2% ranging up to 12% (p <0.01). The muscle end regions are exposed to higher mechanical strain, which points towards mechanical disruption of the sarcolemma as one of the key factors in the pathophysiology. Overall, this non-uniformity in fat replacement needs to be taken into account to prevent sample bias when applying quantitative MRI as biomarker in clinical trials for DMD.
Blaya, S; Acebal, P; Carretero, L; Murciano, A; Madrigal, R F; Fimia, A
2010-01-18
The recent results reported in reference 1 have produced an increased interest in explaining deviations from the ideal behavior of the energetic variation of the diffraction efficiency of holographic gratings. This ideal behavior occurs when uniform gratings are recorded, and the index modulation is proportional to the energetic exposure. As a result, a typical sin(2) curve is obtained reaching a maximum diffraction efficiency and saturation at or below this value. However, linear deviations are experimentally observed when the first maximum on the curve is lower than the second. This effect does not correspond to overmodulation and recently in PVA/acrylamide photopolymers of high thickness it has been explained by the dye concentration in the layer and the resulting molecular weight of the polymer chains generated in the polymerization process. In this work, new insights into these deviations are gained from the analysis of the non-uniform gratings recorded. Therefore, we show that deviations from the linear response can be explained by taking into account the energetic evolution of the index modulation as well as the fringe bending in the grating.
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.
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.
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.
Modelling of non-uniform electrical potential barriers for metal surfaces with chemisorbed oxygen
NASA Astrophysics Data System (ADS)
Sun, Chang Q.; Bai, Chunli
1997-07-01
A modelling approximation regarding the behaviour of electrons on metal surfaces with chemisorbed oxygen is presented. It is suggested that, as consequences of O - metal surface bonding, ionization, polarization and removal of metal atoms cause the non-uniformity in the surface potential barrier (SPB). The inelastic potential is formulated by using a Fermi-type spatial decay and the work function that depends on the occupied density of state. This formulation takes into account that, at energies below the plasma excitation energy, electron excitation dominates and that the electron excitation occurs in the electron-occupied space with any energy greater than the work function. The present modelling method is an improvement in that (i) the elastic potential, the spatial decay and the energy dependence of the inelastic potential are associated with the electron distribution, 0953-8984/9/27/013/img5 (ii) all the SPB parameters are functionalized as dependents of the origin of the image plane, 0953-8984/9/27/013/img6, or the boundary of the region occupied by electrons; (iii) the spatial localization and the variation in energy state are taken into account; and (iv) the single-variable parameterized SPB simplifies the very-low-energy electron diffraction calculations and ensures the uniqueness of the solutions. This method allows us to optimize crystal structures by uniquely comparing the shapes of the geometry-dependent 0953-8984/9/27/013/img7 curves that exhibit joint features of topography and spectroscopy revealed by STM/STS.
Change of Tensile Strength due to Non-uniform Thermal Deterioration of XLPE Sheets
NASA Astrophysics Data System (ADS)
Kurihara, Takashi; Takahashi, Toshihiro; Homma, Hiroya; Okamoto, Tatsuki
Cross-linked polyethylene (XLPE) sheets were thermally deteriorated in atmospheric air at 180°C for at most 100 hours, and their depth profiles of the oxidation degrees were investigated with a micro FT-IR, and the relationships between the oxidation degree and mechanical properties such as tensile strength and elongation at break were examined. The oxidation degree was defined as the ratio of the IR absorption peak for the C=O bond to that for the C-H bond. When tensile strength and elongation at break of XLPE sheets decreased, the oxidation degree increased and the oxidation degree distributed non-uniformly with depth. That is, the oxidation degree was the largest on the upper surface of XLPE sheets where air supply was sufficient during heating, and it was the smallest on the lower surface that contacted with a metal plate during heating. Since the mechanical characteristics such as the hardness and the Young's modulus decreased in the oxidized region of XLPE sheets, it was pointed out that the oxidized region became a weak point against the mechanical stress. It was also pointed out that the micro FT-IR was useful in evaluating the depth profile of oxidation in polymer materials.
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.
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.
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).
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.
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, we describe the necessary adaptations for the development of a NURBs-based metamodel called a Hyperdimensional Performance Model or HyPerModel. HyPerModels are capable of accurately and reliably modeling nonlinear hyperdimensional objects defined by both continuous and discontinuous variables of a wide variety of topologies, such as those that define typical engineering design spaces. We demonstrate this ability by successfully generating accurate HyPerModels of 10 trial functions laying the foundation for future work with N-dimensional NURBs in design space applications.
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.
NASA Astrophysics Data System (ADS)
Zupančič, Matevž; Može, Matic; Gregorčič, Peter; Golobič, Iztok
2017-03-01
Microstructured uniformly and non-uniformly wettable surfaces were created on 25-μm-thin stainless steel foils by laser texturing using a marking nanosecond Nd:YAG laser (λ = 1064 nm) and utilizing various laser fluences and scan line separations. High-speed photography and high-speed IR thermography were used to investigate nucleate boiling heat transfer on the microstructured surfaces. The most pronounced results were obtained on a surface with non-uniform microstructure and non-uniform wettability. The obtained results show up to a 110% higher heat transfer coefficients and 20-40 times higher nucleation site densities compared to the untextured surface. We show that the number of active nucleation sites is significantly increased in the vicinity of microcavities that appeared in areas with the smallest (10 μm) scan line separation. Furthermore, this confirms the predictions of nucleation criteria and proves that straightforward, cost-effective nanosecond laser texturing allows the production of cavities with diameters of up to a few micrometers and surfaces with non-uniform wettability. Additionally, this opens up important possibilities for a more deterministic control over the complex boiling process.
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.
a Study on the Squeal of a Drum Brake which has Shoes of Non-Uniform Cross-Section
NASA Astrophysics Data System (ADS)
LEE, J. M.; YOO, S. W.; KIM, J. H.; AHN, C. G.
2001-03-01
A stability analysis of a drum brake, which has shoes of non-uniform cross-section, is performed to find a simple and effective method of reducing the squeal of the drum brake by partially changing the shapes of the shoes. The squeal is considered as a noise induced by the self-excited vibration of the drum brake which makes the brake unstable. Shoes of non-uniform cross-section are often used for the drum brake of current passenger cars to reduce the squeal. However, the influence of this non-uniformity upon the squeal has not been analyzed theoretically. In this study, the drum and the shoes are assumed as a uniform ring and non-uniform arches, respectively, for modelling the brake. For a reasonable method of modelling, the vibration characteristics of the brake and their relations to the squeal are discussed based on the results of modal tests. The influences of brake design parameters upon the squeal are investigated, and a minor change of the cross-section is proposed to reduce the squeal. The effect of the minor change is verified through noise dynamometer tests. In addition, the effect of asymmetry of the drum, which can be built by mass addition, is presented.
2015-12-01
V/L applications over the last 10 to 15 years. The commercial Computer Aided Design (CAD) industry, which didn’t really exist when CSG was...CAD Computer Aided Design CSG Constructive Solid Geometry FY fiscal year NIST National Institute of Standards and Technology NURBS Non-Uniform
Nonlinear Dynamics of Non-uniform Current-Vortex Sheets in Magnetohydrodynamic Flows
NASA Astrophysics Data System (ADS)
Matsuoka, C.; Nishihara, K.; Sano, T.
2017-04-01
A theoretical model is proposed to describe fully nonlinear dynamics of interfaces in two-dimensional MHD flows based on an idea of non-uniform current-vortex sheet. Application of vortex sheet model to MHD flows has a crucial difficulty because of non-conservative nature of magnetic tension. However, it is shown that when a magnetic field is initially parallel to an interface, the concept of vortex sheet can be extended to MHD flows (current-vortex sheet). Two-dimensional MHD flows are then described only by a one-dimensional Lagrange parameter on the sheet. It is also shown that bulk magnetic field and velocity can be calculated from their values on the sheet. The model is tested by MHD Richtmyer-Meshkov instability with sinusoidal vortex sheet strength. Two-dimensional ideal MHD simulations show that the nonlinear dynamics of a shocked interface with density stratification agrees fairly well with that for its corresponding potential flow. Numerical solutions of the model reproduce properly the results of the ideal MHD simulations, such as the roll-up of spike, exponential growth of magnetic field, and its saturation and oscillation. Nonlinear evolution of the interface is found to be determined by the Alfvén and Atwood numbers. Some of their dependence on the sheet dynamics and magnetic field amplification are discussed. It is shown by the model that the magnetic field amplification occurs locally associated with the nonlinear dynamics of the current-vortex sheet. We expect that our model can be applicable to a wide variety of MHD shear flows.
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.
Analysis of non-uniform current distribution effects in multistage cable-in-conduit conductors
NASA Astrophysics Data System (ADS)
Mitchell, N.
1999-09-01
An analysis procedure has been developed for non-uniform current effects in superconducting cables that contain many individual strands in limited electrical contact with each other. The procedure uses an approximation to the electrical diffusion equation to produce a lumped circuit model of the cable and a simplified zero dimensional heat balance equation to provide overall predictions of the cable stability to external disturbances. It is fast enough to be applied to the multistage cables (>1000 individual strands) that are required for large high field magnets. A model for the initial current distribution in such cables assumes that in steady state or slow ramp-up conditions the current in individual strands is limited to the critical value by the strand resistance. The distribution of current carrying strands is determined by the resistance distribution at the terminations, the cable transverse conductivity and variations in inductive coupling between individual strands. This model is applied to consider the effect of these parameters on the stability to short thermal disturbances. The particular case of the ITER Nb 3Sn CS model coil 13T, 40 kA cable-in-conduit conductor is analysed and it is shown that above a certain current level the cables can sometimes show a sharp drop in stability, qualitatively consistent with results observed on short sample tests. This stability drop is much more severe than that characterised by the conventional `well-cooled to ill-cooled' transition and represents the limit of steady state or slow ramp-up operation. The stability cut-off current is shown to be a function of the copper fraction in the cable, the uniformity of the current carrying strand distribution and the cable transverse conductance distribution. NbTi conductors with a similar configuration show the same behaviour.
Low-salinity plume detachment under non-uniform summer wind off the Changjiang Estuary
NASA Astrophysics Data System (ADS)
Ge, Jianzhong; Ding, Pingxing; Chen, Changsheng
2015-04-01
In the past, two physical mechanisms, baroclinic instability (BI) and strong asymmetric tidal mixing (SATM) during the spring tidal period, were proposed for the offshore detachment of the low-salinity plume over the inner shelf of the East China Sea (ECS). These two mechanisms were re-examined using both observations and a fully three-dimensional (3-D), high-resolution, unstructured-grid, free-surface, primitive-equation, Finite-Volume Community Ocean Model (FVCOM). The observed currents and salinities showed that the plume was characterized by a two-layer system, in which the upper layer is mainly driven by the river discharge-induced buoyancy flow and the lower layer is predominantly controlled by tidal mixing and rectification. The SATM mechanism was based on the model run without calibration against observed currents and salinity around the plume region, so that it should be applied with caution to a realistic condition observed on the inner shelf of the ECS. The BI mechanism was derived under a condition without consideration of tidal mixing. Although BI could still occur along the frontal zone when tides were included, it was unable to produce a single, large, detached low-salinity lens observed on the inner shelf of the ECS. The process-oriented model experiment results suggest that for a given river discharge and realistic tidal flow, the spatially non-uniform southwesterly surface wind during the southeast monsoon-dominant summer could increase frontal spatial variability and thus produce a significant offshore detachment of low-salinity water on the inner shelf of East China Sea.
Accurate determination of rates from non-uniformly sampled relaxation data.
Stetz, Matthew A; Wand, A Joshua
2016-08-01
The application of non-uniform sampling (NUS) to relaxation experiments traditionally used to characterize the fast internal motion of proteins is quantitatively examined. Experimentally acquired Poisson-gap sampled data reconstructed with iterative soft thresholding are compared to regular sequentially sampled (RSS) data. Using ubiquitin as a model system, it is shown that 25 % sampling is sufficient for the determination of quantitatively accurate relaxation rates. When the sampling density is fixed at 25 %, the accuracy of rates is shown to increase sharply with the total number of sampled points until eventually converging near the inherent reproducibility of the experiment. Perhaps contrary to some expectations, it is found that accurate peak height reconstruction is not required for the determination of accurate rates. Instead, inaccuracies in rates arise from inconsistencies in reconstruction across the relaxation series that primarily manifest as a non-linearity in the recovered peak height. This indicates that the performance of an NUS relaxation experiment cannot be predicted from comparison of peak heights using a single RSS reference spectrum. The generality of these findings was assessed using three alternative reconstruction algorithms, eight different relaxation measurements, and three additional proteins that exhibit varying degrees of spectral complexity. From these data, it is revealed that non-linearity in peak height reconstruction across the relaxation series is strongly correlated with errors in NUS-derived relaxation rates. Importantly, it is shown that this correlation can be exploited to reliably predict the performance of an NUS-relaxation experiment by using three or more RSS reference planes from the relaxation series. The RSS reference time points can also serve to provide estimates of the uncertainty of the sampled intensity, which for a typical relaxation times series incurs no penalty in total acquisition time.
Zhuchkova, Ekaterina; Remme, Michiel W. H.; Schreiber, Susanne
2013-01-01
Synaptic inputs to neurons are processed in a frequency-dependent manner, with either low-pass or resonant response characteristics. These types of filtering play a key role in the frequency-specific information flow in neuronal networks. While the generation of resonance by specific ionic conductances is well investigated, less attention has been paid to the spatial distribution of the resonance-generating conductances across a neuron. In pyramidal neurons – one of the major excitatory cell-types in the mammalian brain – a steep gradient of resonance-generating h-conductances with a 60-fold increase towards distal dendrites has been demonstrated experimentally. Because the dendritic trees of these cells are large, spatial compartmentalization of resonant properties can be expected. Here, we use mathematical descriptions of spatially extended neurons to investigate the consequences of such a distal, dendritic localization of h-conductances for signal processing. While neurons with short dendrites do not exhibit a pronounced compartmentalization of resonance, i.e. the filter properties of dendrites and soma are similar, we find that neurons with longer dendrites ( space constant) can show distinct filtering of dendritic and somatic inputs due to electrotonic segregation. Moreover, we show that for such neurons, experimental classification as resonant versus nonresonant can be misleading when based on somatic recordings, because for these morphologies a dendritic resonance could easily be undetectable when using somatic input. Nevertheless, noise-driven membrane-potential oscillations caused by dendritic resonance can propagate to the soma where they can be recorded, hence contrasting with the low-pass filtering at the soma. We conclude that non-uniform distributions of active conductances can underlie differential filtering of synaptic input in neurons with spatially extended dendrites, like pyramidal neurons, bearing relevance for the localization
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
Computationally efficient real-time interpolation algorithm for non-uniform sampled biosignals.
Guven, Onur; Eftekhar, Amir; Kindt, Wilko; Constandinou, Timothy G
2016-06-01
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.
NASA Astrophysics Data System (ADS)
Wu, C.; de Jong, J. R.; Gratama van Andel, H. A.; van der Have, F.; Vastenhouw, B.; Laverman, P.; Boerman, O. C.; Dierckx, R. A. J. O.; Beekman, F. J.
2011-09-01
Attenuation of photon flux on trajectories between the source and pinhole apertures affects the quantitative accuracy of reconstructed single-photon emission computed tomography (SPECT) images. We propose a Chang-based non-uniform attenuation correction (NUA-CT) for small-animal SPECT/CT with focusing pinhole collimation, and compare the quantitative accuracy with uniform Chang correction based on (i) body outlines extracted from x-ray CT (UA-CT) and (ii) on hand drawn body contours on the images obtained with three integrated optical cameras (UA-BC). Measurements in phantoms and rats containing known activities of isotopes were conducted for evaluation. In 125I, 201Tl, 99mTc and 111In phantom experiments, average relative errors comparing to the gold standards measured in a dose calibrator were reduced to 5.5%, 6.8%, 4.9% and 2.8%, respectively, with NUA-CT. In animal studies, these errors were 2.1%, 3.3%, 2.0% and 2.0%, respectively. Differences in accuracy on average between results of NUA-CT, UA-CT and UA-BC were less than 2.3% in phantom studies and 3.1% in animal studies except for 125I (3.6% and 5.1%, respectively). All methods tested provide reasonable attenuation correction and result in high quantitative accuracy. NUA-CT shows superior accuracy except for 125I, where other factors may have more impact on the quantitative accuracy than the selected attenuation correction.
PARTIAL ERUPTION OF A FILAMENT WITH TWISTING NON-UNIFORM FIELDS
Bi, Yi; Jiang, Yunchun; Yang, Jiayan; Xiang, Yongyuan; Cai, Yunfang; Liu, Weiwei
2015-05-20
The eruption of a filament in a kinklike fashion is often regarded as a signature of kink instability. However, the kink instability threshold for the filament’s magnetic structure is not widely understood. Using Hα observations from the New Vacuum Solar Telescope, we present a partial eruptive filament. During the eruption, the filament thread appeared to split from its middle and to break out in a kinklike fashion. In this period, the remaining filament material stayed below and erupted without the kinking motion later on. The coronal magnetic field lines associated with the filament are obtained from nonlinear force-free field extrapolations using the twelve-minute-cadence vector magnetograms of the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamic Observatory. We studied the extrapolated field lines passing through the magnetic dips which are in good agreement with the observed filament. The field lines are non-uniformly twisted and appear to be composed of two twisted flux ropes winding around each other. One of them has a higher twist than the other, and the flux rope with the higher twist has its dips aligned with the kinking eruptive thread at the beginning of its eruption. Before the eruption, moreover, the flux rope with the higher twist was found to expand with an approximately constant field twist. In addition, the helicity flux maps deduced from the HMI magnetograms show that some helicity is injected into the overlying magnetic arcade, but no significant helicity is injected into the flux ropes. Accordingly, we suggest that the highly twisted flux rope became kink unstable when the instability threshold declined with the expansion of the flux rope.
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).
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
Leverage and Evaluation Effectiveness.
ERIC Educational Resources Information Center
Caro, Francis G.
Weakness in evaluations often can be traced to structural limitations in the positions of evaluation researchers. Conventional human relations techniques often are an insufficient basis for securing strong support for evaluation research. Strategies for increasing evaluation research leverage are reviewed. Alignment of evaluation research with…
Theoretical/numerical model for the transport of non-uniform suspended sediment in open channels
NASA Astrophysics Data System (ADS)
Jha, Sanjeev K.; Bombardelli, Fabián A.
2011-05-01
In this paper, we address the transport of multi-disperse suspended sediment mixtures in open channels, via the use of the two-fluid model. To that end, we extend previously developed frameworks for the dilute and non-dilute transport of suspended sediment. Within the scope of the Reynolds-averaged Navier-Stokes (RANS) equations, these modeling frameworks comprise mass and momentum equations for both phases (water and sediment). Here, we calculate the distribution of total volumetric concentration of sediment using two approaches: (1) by considering the mixture as represented by a single size; we call this approach Partial two-fluid model for uniform sediments (PTFMU); and (2) by combining the volumetric concentration of the sediment corresponding to several particle size classes; we call this approach Partial two-fluid model for non-uniform sediments (PTFMNU). In the second approach, we propose a methodology for the computation of the overall velocity of the disperse phase as a function of the velocities of each size class. k- ɛ type closures to account for the turbulence in the carrier phase (water) are applied. We also consider the coupling between the two phases through the drag force. Velocities of the carrier and disperse phases, and concentrations for each sediment class size are numerically solved by integrating the differential equations over control volumes. In order to validate our models, we compare numerical results to experimental data of Einstein and Chien [H.A. Einstein, N. Chien, Effects of heavy sediment concentration near the bed on velocity and sediment distribution, MRD sediment series report, University of California, Berkley, 1955] and Taggart et al. [W.C. Taggart, C.A. Yermoli, S. Montes, A. Ippen, Effects of sediment size and gradation on concentration profiles for turbulent flow, Massachusetts Institute of Technology, 1972]. Results of mean velocity of the carrier phase are in close agreement with the experimental data. For the prediction
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
Flame balls in non-uniform mixtures: existence and finite activation energy effects
NASA Astrophysics Data System (ADS)
Daou, Remi; Pearce, Philip; Daou, Joel
2016-01-01
The paper's broad motivation, shared by a recent theoretical investigation [Daou and Daou, "Flame balls in mixing layers," Combustion and Flame, Vol. 161 (2014), pp. 2015-2024], is a fundamental but apparently untouched combustion question; specifically, 'What are the critical conditions insuring the successful ignition of a diffusion flame by means of an external energy deposit (spark), after mixing of cold reactants has occurred in a mixing layer?' The approach is based on a generalisation of the concept of Zeldovich flame balls, well known in premixed reactive mixtures, to non-uniform mixtures. This generalisation leads to a free boundary problem (FBP) for axisymmetric flame balls in a two-dimensional mixing layer in the distinguished limit β → ∞ with εL = O(1); here β is the Zeldovich number and εL is a non-dimensional measure of the stoichiometric premixed flame thickness. The existence of such flame balls is the main object of current investigation. Several original contributions are presented. First, an analytical contribution is made by carrying out the analysis of Daou and Daou (2014) in the asymptotic limit εL → 0 to higher order. The results capture, in particular, the dependence of the location of the flame ball centre (argued to represent the optimal ignition location which differs from the stoichiometric location) on εL. Second, two detailed numerical studies of the axisymmetric flame balls are presented for arbitrary values of εL. The first study addresses the infinite-β FBP and the second one the original finite-β problem based on the constant density reaction-diffusion equations. In particular, it is shown that solutions to the FBP exist for arbitrary values of εL while actual finite-β flame balls exist in a specific domain of the β-εL plane, namely for εL less than a maximum value proportional to ?; this scaling is consistent with the existence of solutions to the FBP for arbitrary εL. In fact, the flame ball existence domain
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.
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)
Khaghani, Morteza; Mehmandoost-Khajeh-Dad, Ali Akbar
2017-04-01
Ortho-positronium (o-Ps) annihilation lifetime was calculated in non-uniform cylinder-shaped pores by solving Schrodinger equation using a well-known multi-physics program called COMSOL. The o-Ps annihilation lifetime variation in terms of temperature was calculated on the basis of ETE model via a numerical method. The COMSOL simulations indicate that as long as the pore is uniform cylinder-shaped, the results agree with those of two-dimensional ETE model, whereas deformations in the cylinder shape (indentation or protrusion) change the temperature behavior of ETE model and, thereby, higher values are predicted for o-Ps lifetime in the pore at lower temperatures. The geometry of the non-uniform cylinder-shaped pores, which is accompanied by empirical evidence, can be used for the analysis of empirical results obtained from positron lifetime spectroscopy in different temperatures.
Matronchik, A Y; Belyaev, I Y
2008-01-01
Recent data show that microwaves (MW) and extremely low-frequency (ELF) magnetic fields at low intensities affect conformation of nucleoids in bacterial E. coli cells and human lymphocytes. Experimental data suggest that magnitude of the effects of both MW and ELF depend on frequency and static magnetic field. We have previously proposed the physical model for the effects of combined ELF/static magnetic fields on the charged DNA-domain/nucleoid. In this article, we present the model of slow non uniform rotation of the charged DNA-domain/nucleoid for the combined effects of MW and static magnetic field. The solution of this model suggests that the combined action of MW and static magnetic field results in slow non uniform rotation of nucleoid with angular speed that depends on Larmor frequency. The model predicts that non thermal effects of MW are dependent on carrier frequency and also static magnetic field in the area of exposure.
Guldiken, Rasim O.; Zahorian, Jaime; Yamaner, F. Y.; Degertekin, F. L.
2010-01-01
In this paper, we report measurement results on dual-electrode CMUT demonstrating electromechanical coupling coefficient (k2) of 0.82 at 90% of collapse voltage as well as 136% 3 dB one-way fractional bandwidth at the transducer surface around the design frequency of 8 MHz. These results are within 5% of the predictions of the finite element simulations. The large bandwidth is achieved mainly by utilizing a non-uniform membrane, introducing center mass to the design, whereas the dual-electrode structure provides high coupling coefficient in a large dc bias range without collapsing the membrane. In addition, the non-uniform membrane structure improves the transmit sensitivity of the dual-electrode CMUT by about 2dB as compared with a dual electrode CMUT with uniform membrane. PMID:19574135
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.
Guldiken, Rasim O; Zahorian, Jaime; Yamaner, F Y; Degertekin, F Levent
2009-06-01
In this paper, we report measurement results on dual-electrode CMUT demonstrating electromechanical coupling coefficient (k(2)) of 0.82 at 90% of collapse voltage as well as 136% 3 dB one-way fractional bandwidth at the transducer surface around the design frequency of 8 MHz. These results are within 5% of the predictions of the finite element simulations. The large bandwidth is achieved mainly by utilizing a non-uniform membrane, introducing center mass to the design, whereas the dual-electrode structure provides high coupling coefficient in a large dc bias range without collapsing the membrane. In addition, the non-uniform membrane structure improves the transmit sensitivity of the dual-electrode CMUT by about 2dB as compared with a dual electrode CMUT with uniform membrane.
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)
Vodák, J.; Nečas, D.; Ohlídal, M.; Ohlídal, I.
2017-02-01
In this paper an imaging spectroscopic reflectometer with enhanced spatial resolution is presented. Main features of its design, experimental data acquisition, i.e. maps of thin film spectral dependencies of local reflectance and the local thickness map determination are described. The ability of this instrument to characterize thin film thickness non-uniformity with high gradients is demonstrated on measurements of thin film edges. A comparison with an older device is also presented.
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 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.
NASA Astrophysics Data System (ADS)
Park, Yong Min; Kim, Byeong Hee; Seo, Young Ho
2016-06-01
This paper presents a selective aluminum anodization technique for the fabrication of microstructures covered by nanoscale dome structures. It is possible to fabricate bulging microstructures, utilizing the different growth rates of anodic aluminum oxide in non-uniform electric fields, because the growth rate of anodic aluminum oxide depends on the intensity of electric field, or current density. After anodizing under a non-uniform electric field, bulging microstructures covered by nanostructures were fabricated by removing the residual aluminum layer. The non-uniform electric field induced by insulative micropatterns was estimated by computational simulations and verified experimentally. Utilizing computational simulations, the intensity profile of the electric field was calculated according to the ratio of height and width of the insulative micropatterns. To compare computational simulation results and experimental results, insulative micropatterns were fabricated using SU-8 photoresist. The results verified that the shape of the bottom topology of anodic alumina was strongly dependent on the intensity profile of the applied electric field, or current density. The one-step fabrication of nanostructure-covered microstructures can be applied to various fields, such as nano-biochip and nano-optics, owing to its simplicity and cost effectiveness.
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)
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 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)
Rau, G. C.; Andersen, M. S.; Acworth, R. I.
2012-12-01
In recent years tracing water movement using heat has seen a revival, in particular methods that utilize the natural diel temperature fluctuations. However, research has mainly focused on field applications and numerical modeling with little laboratory testing. In this study heat tracing was experimentally tested for a 1D flow field through water saturated sand considered homogeneous (d_50~2 mm). Uniform pressure gradients were applied to a tank with the dimensions 0.4 x 0.4 x 1 m inducing Darcy velocities between 0 and 25 m/d (Re<0.45). As heat input either a point source with a step change or a sinusoidally varying area source were applied. The temperature response was recorded by multiple temperature probes at various locations. A number of observations indicate a significant degree of non-uniform flow in the sand, which in a hydrogeological context should be considered homogeneous. Color dye experiments were performed to visually verify the functionality of the hydraulic setup. Surprisingly, the propagation of the color dye front revealed fingering which increased with travel distance. The possibility of density fingering could be excluded because: (1) the possible density difference was well below the threshold required for density fingering, (2) the non-uniform flow phenomenon could be observed for both upward and downward flow. The thermal response to a step heat input from a point source showed a systematically increasing difference in the steady-state response at off-center line probes for increasing flow velocities. Contrary to the case of only heat conduction, the variability of temperatures measured at different locations, but at similar distances was indicative of the thermal plume spreading non-uniformly around the source. For the area heat forcing experiments flow velocities were separately calculated from amplitude damped and phase shifted temperature-depth responses recorded by vertically arranged pairs of probes using 1D analytical heat transport
Non-uniform thickness in Europa's icy shell: implications for astrobiology mission design
NASA Astrophysics Data System (ADS)
Fairén, A.; Amils, R.
zero shell thickness [12]) with liquid water at shallow depths [5], allowing for bolide penetration, diapirism and the extrusion of water to the surface. The heterogeneity in shell's thickness may be originated in spatial variations in tidal heating [13] and/or warm water upwellings from the silicate interior capable of melt-through the ice from below [12,14]. This thickness heterogeneity can be embedded in a general equatorward thickening trending, due to tidal dissipation and surface temperature variations [15]. A major constraint must be addressed at this point: the dynamism of ductile ice near the base of the shell may drive to decay in lateral thickness contrasts. But this effect has been examined both assuming ice as a Newtonian [16,17,18] and a non-Newtonian material [19], broadly reaching to similar conclusions: global shell thickness variations may survive for up to 100 Myr. In addition, lateral pressure gradients may not decay if they comprise only shallow depths [19]. Therefore, our results point to a dynamic non-uniform Europa's icy shell, displaying some regional and temporal heterogeneity in thickness. As thin/thick ice distribution is as time dependent as the surface ice features are (both are reshaped in periods ˜ 100 Myr), the analysis performed here offers an estimation of the current thickness distribution in the ice shell, estimation that cannot be extrapolated to ancient (e.g., >100 Myr) times. The astrobiological potential the shell and ocean below possess is highlighted by these results: a somewhere thin outer crust allows the possibility for some exogenous materials delivered by asteroids and comets to reach the inner liquid water ocean by breaching the brittle lithosphere [20], and so join to those generated in the interior of Europa via volcanic and hydrothermal activity [21]. In addition, pressure gradients driving the ductile ice at the base of the shell to flow laterally may help to redistribute such materials among the inner ice shell and
Lucas, Kelsey N; Thornycroft, Patrick J M; Gemmell, Brad J; Colin, Sean P; Costello, John H; Lauder, George V
2015-10-08
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.
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.
A criterion to determine uniform and non-uniform stratified liquid-gas flow through horizontal tubes
Bishop, A.A.; Deshpande, S.D.
1986-04-01
Non-uniform liquid-gas stratified flow (i.e. flow with an interfacial level gradient, ILG) can exist when high viscosity liquids and/or large diameter tubes are used. The available data, covering a wide range of liquid viscosities (0.8 to 310 mPa.s) and tube diameters (0.0254 m to 0.216 m), are analyzed. It is shown that the Lockhart-Martinelli parameter, X less than or equal to 1 is a criterion to determine uniform stratified flow and disappearance of ILG. In addition, interfacial shear stress relationships are also shown to be indicative of different types of stratified flow.
NASA Astrophysics Data System (ADS)
Hu, Changmiao; Bai, Yang; Tang, Ping
2016-06-01
We present a denoising algorithm for the pixel-response non-uniformity correction of a scientific complementary metal-oxide-semiconductor (CMOS) image sensor, which captures images under extremely low-light conditions. By analyzing the integrating sphere experimental data, we present a pixel-by-pixel flat-field denoising algorithm to remove this fixed pattern noise, which occur in low-light conditions and high pixel response readouts. The response of the CMOS image sensor imaging system to the uniform radiance field shows a high level of spatial uniformity after the denoising algorithm has been applied.
Hasegawa, Sho; Shibata, Maki; Mochizuki, Makoto; Katsuki, Takashi; Tada, Manami; Hinoshita, Fumihiko
2017-01-01
Although patients with anorexia nervosa (anorexia) are known to show tubulointerstitial nephritis (TIN), the pathophysiology of its progression is not fully understood. We herein report a 31-year-old woman with anorexia who showed acute exacerbation of chronic kidney disease. Renal biopsy showed non-uniform chronic TIN; some areas were obsolete lesions and other areas were active lesions. In addition, many calcium-containing crystals were widely deposited in the distal tubules. The results suggest that chronic TIN in the setting of anorexia does not uniformly progress and that not only TIN but also widespread calcification of distal tubules might aggravate the renal function of anorexia patients.
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.
Underwood, Jonathan G; Procino, I; Christiansen, L; Maurer, J; Stapelfeldt, H
2015-07-01
We present a method for inverting charged particle velocity map images which incorporates a non-uniform detection function. This method is applied to the specific case of extracting molecular axis alignment from Coulomb explosion imaging probes in which the probe itself has a dependence on molecular orientation which often removes cylindrical symmetry from the experiment and prevents the use of standard inversion techniques for the recovery of the molecular axis distribution. By incorporating the known detection function, it is possible to remove the angular bias of the Coulomb explosion probe process and invert the image to allow quantitative measurement of the degree of molecular axis alignment.
NASA Astrophysics Data System (ADS)
Herrero, Rebeca; Victoria, Marta; Domínguez, César; Askins, Stephen; Antón, Ignacio; Sala, Gabriel
2015-09-01
This paper presents the mechanisms of efficiency losses that have to do with the non-uniformity of the irradiance over the multi-junction solar cells and different measurement techniques used to investigate them. To show the capabilities of the presented techniques, three different concentrators (that consist of an acrylic Fresnel lens, different SOEs and a lattice matched multi-junction cell) are evaluated. By employing these techniques is possible to answer some critical questions when designing concentrators as for example which degree of non-uniformity the cell can withstand, how critical the influence of series resistance is, or what kind of non-uniformity (spatial or spectral) causes more losses.
17 CFR 31.10 - Repurchase and resale of leverage contracts by leverage transaction merchants.
Code of Federal Regulations, 2012 CFR
2012-04-01
... customers any long leverage contract, involving the same leverage commodity previously purchased or sold by... sell or sell a long leverage contract involving a leverage commodity to any leverage customer at any... customers any long leverage contract, and is not offering to resell to any of its leverage customers...
NASA Astrophysics Data System (ADS)
Vašina, P; Hytková, T; Eliáš, M
2009-05-01
The majority of current models of the reactive magnetron sputtering assume a uniform shape of the discharge current density and the same temperature near the target and the substrate. However, in the real experimental set-up, the presence of the magnetic field causes high density plasma to form in front of the cathode in the shape of a toroid. Consequently, the discharge current density is laterally non-uniform. In addition to this, the heating of the background gas by sputtered particles, which is usually referred to as the gas rarefaction, plays an important role. This paper presents an extended model of the reactive magnetron sputtering that assumes the non-uniform discharge current density and which accommodates the gas rarefaction effect. It is devoted mainly to the study of the behaviour of the reactive sputtering rather that to the prediction of the coating properties. Outputs of this model are compared with those that assume uniform discharge current density and uniform temperature profile in the deposition chamber. Particular attention is paid to the modelling of the radial variation of the target composition near transitions from the metallic to the compound mode and vice versa. A study of the target utilization in the metallic and compound mode is performed for two different discharge current density profiles corresponding to typical two pole and multipole magnetics available on the market now. Different shapes of the discharge current density were tested. Finally, hysteresis curves are plotted for various temperature conditions in the reactor.
NASA Astrophysics Data System (ADS)
Lee, Junsu; Park, June; Koo, Joonhoi; Jhon, Young Min; Lee, Ju Han
2016-03-01
We investigated the feasibility of using a WS2-deposited side-polished fiber as a harmonic mode-locker to produce a femtosecond fiber laser with a frequency of 1.51 GHz. Our work focuses on using a side-polished fiber platform with non-uniform WS2 particles prepared through liquid phase exfoliation method without centrifugation. Femtosecond optical pulses were generated from an all-fiberized erbium-doped fiber-based ring cavity by increasing the pump power to achieve a tunable pulse repetition rate from 14.57 MHz to 1.51 GHz (104th harmonic). The characteristics of the output pulse were systematically investigated to analyze the pulse repetition rate, harmonic order, average output power, pulse energy, and pulse width as a function of the pump power. The output performance of the laser was compared to that of a laser based on a microfiber-based WS2 film SA described in (Yan et al 2015 Opt. Mater. Express 5 479-89). This experimental demonstration reaffirms that a side-polished fiber is an effective platform to implement an ultrafast harmonic mode-locker, and non-uniform WS2 particles prepared via simple liquid phase exfoliation method without centrifugation provide a suitable saturable absorption response at 1.55 μm.
Investigation of the novel 4Hsbnd SiC trench MOSFET with non-uniform doping floating islands
NASA Astrophysics Data System (ADS)
Song, Qingwen; Tang, Xiaoyan; Tian, Ruiyan; Zhang, Yimeng; Guo, Tao; Tang, Guannan; Yang, Shuai; Yuan, Hao; He, Yanjing
2016-11-01
In this paper, a novel 4Hsbnd SiC trench metal-oxide-semiconductor field-effect transistor (MOSFET) with non-uniform doping floating islands is proposed, using a Gaussian doping profile in the floating islands. The feature of the non-uniform doping floating island is that the doping concentration of upper part is higher than the lower part. The electric field between the floating island and drift region can be reduced by the decrease in the doping concentration of the lower part. At the same time, the high doping concentration for the upper part of the floating island is utilized, so that gate oxide layer at the sharp corner of the trench gate bottom cannot be broken down in advance. The simulation results indicate that the breakdown voltage of the novel structure can increase by 48%, compared with the structure with the uniform doping (6 × 1017 cm-3) floating island. Furthermore, the switching and gate charge characteristics of the UMOSFETs with uniform and Gaussian doping floating islands have been simulated using two simple switching circuits. The results indicate that changing the doping concentration of the floating islands has no negative effect on the switching characteristics.
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)
Ma, Liu Hao; Lau, Lok Yin; Ren, Wei
2017-03-01
We report in situ measurements of non-uniform temperature, H2O and CO2 concentration distributions in a premixed methane-air laminar flame using tunable diode laser absorption spectroscopy (TDLAS). A mid-infrared, continuous-wave, room-temperature interband cascade laser (ICL) at 4183 nm was used for the sensitive detection of CO2 at high temperature.The H2O absorption lines were exploited by one distributed feedback (DFB) diode laser at 1343 nm and one ICL at 2482 nm to achieve multi-band absorption measurements with high species concentration sensitivity, high temperature sensitivity, and immunity to variations in ambient conditions. A novel profile-fitting function was proposed to characterize the non-uniform temperature and species concentrations along the line-of-sight in the flame by detecting six absorption lines of CO2 and H2O simultaneously. The flame temperature distribution was measured at different heights above the burner (5-20 mm), and compared with the thermocouple measurement with heat-transfer correction. Our TDLAS measured temperature of the central flame was in excellent agreement (<1.5% difference) with the thermocouple data.The TDLAS results were also compared with the CFD simulations using a detailed chemical kinetics mechanism (GRI 3.0) and considering the heat loss to the surroundings.The current CFD simulation overpredicted the flame temperature in the gradient region, but was in excellent agreement with the measured temperature and species concentration in the core of the flame.
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.
NASA Astrophysics Data System (ADS)
Huang, Sheng; Zhao, Yixi; He, Chunfeng
2013-12-01
The phenomenon "Shear fracture" is often observed in the stretch-bending process of stamping over small radius with advanced high strength steels (AHSS). It occurs parallel to and near the die radius in the stretch-bending test. Since traditional Forming Limit Diagram (FLD) is unable to describe this type of failure, experimental and simulation works were constructed in this paper to investigate and predict the shear fracture. Fracture experiments were carried out through a stretch-bending test system, and failure mode was observed. There is no obviously thinning at the shear fracture surface. Further research shows that the initial crack of shear fracture occurs at the outer layer of specimen at die radius position. Finite element (FE) models were built for stretch-bending test with 3D element. The non-uniform local deformation through thickness corresponding to bending position was obtained and analyzed. Cockcroft & Latham fracture criterion is used. The outer layer of specimen at bending position reaches the critical fracture state firstly, which agrees well with experiments. Different fracture criteria are also compared and selected to determine this fracture. Results show that based on the non-uniform local deformation, the initial crack location of shear fracture at small radius can be effectively predicted by fracture criteria related to the maximum principle stress.
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.
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.
Kim, Donghwan; Pal, Debashish; Thibault, Jean-Baptiste; Fessler, Jeffrey A.
2013-01-01
Statistical image reconstruction algorithms in X-ray CT provide improved image quality for reduced dose levels but require substantial computation time. Iterative algorithms that converge in few iterations and that are amenable to massive parallelization are favorable in multiprocessor implementations. The separable quadratic surrogate (SQS) algorithm is desirable as it is simple and updates all voxels simultaneously. However, the standard SQS algorithm requires many iterations to converge. This paper proposes an extension of the SQS algorithm that leads to spatially non-uniform updates. The non-uniform (NU) SQS encourages larger step sizes for the voxels that are expected to change more between the current and the final image, accelerating convergence, while the derivation of NU-SQS guarantees monotonic descent. Ordered subsets (OS) algorithms can also accelerate SQS, provided suitable “subset balance” conditions hold. These conditions can fail in 3D helical cone-beam CT due to incomplete sampling outside the axial region-of-interest (ROI). This paper proposes a modified OS algorithm that is more stable outside the ROI in helical CT. We use CT scans to demonstrate that the proposed NU-OS-SQS algorithm handles the helical geometry better than the conventional OS methods and “converges” in less than half the time of ordinary OS-SQS. PMID:23751959
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
Louša, Petr; Nedozrálová, Hana; Župa, Erik; Nováček, Jiří; Hritz, Jozef
2017-04-01
Human tyrosine hydroxylase 1 (hTH1) activity is regulated by phosphorylation of its regulatory domain (RD-hTH1) and by an interaction with the 14-3-3 protein. The RD-hTH1 is composed of a structured region (66-169) preceded by an intrinsically disordered protein region (IDP, hTH1_65) containing two phosphorylation sites (S19 and S40) which are highly relevant for its increase in activity. The NMR signals of the IDP region in the non-phosphorylated, singly phosphorylated (pS40) and doubly phosphorylated states (pS19_pS40) were assigned by non-uniformly sampled spectra with increased dimensionality (5D). The structural changes induced by phosphorylation were analyzed by means of secondary structure propensities. The phosphorylation kinetics of the S40 and S19 by kinases PKA and PRAK respectively were monitored by non-uniformly sampled time-resolved NMR spectroscopy followed by their quantitative analysis.
NASA Astrophysics Data System (ADS)
Bongolan, Vena Pearl; Lupiano, Valeria; D'Ambrosio, Donato; Rongo, Rocco; Spataro, William; Iovine, Giulio
2013-04-01
The hazard induced by dangerous flow-type phenomena - e.g. lava flows, earth flows, debris flows, and debris avalanches - can be assessed by analysing a proper set of simulations of hypothetical events. Non-uniform grids are commonly used to study particular areas of interest in computational domains. Examples of application concern, for instance, the turbulence in a boundary layer. While non-uniform grids frequently appear in adaptive methods, they may also be used in a "static" environment. A purposive sampling method, based on a non-uniform grid of sources coupled with numerical simulations of independent events, has recently been employed to evaluate the hazard induced by flow-type phenomena. An example of application to lava-flows at Mount Etna (Italy) is described in this study. The method aims at refining the spatial distribution of hypothetical eruptive vents with respect to an original uniform grid. The density of eruptive vents has been determined by considering the historical distribution of lateral and eccentric vents, and the distribution of the main faults/structures on the volcano. A higher number of sources marks higher-probability zones of vent opening, based on classes of activation: the number of vents in each class has been set proportionally to the probability of activation of the class. By considering the different types of eruption expected from the considered volcano, based on the historical activity of the past 400 years, a set of simulations per each vent has been performed. The employed model is SCIARA-fv2, a Cellular Automata numerical code recently applied to the same study area for preliminary hazard analyses. In this work, calibration could therefore be skipped, by taking advantage from such experience of tuning of the parameters. Performed simulations have been analysed by a GIS, to verify the number of events affecting each cell of the domain. A probability of occurrence could be assigned to each simulation, based on statistics of
45 CFR 96.87 - Leveraging incentive program.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 97-35 (42 U.S.C. 8626a). (2)(i) The only entities eligible to receive leveraging incentive funds from... (42 U.S.C. 8621(b)) in both the base period for which leveraged resources are reported, and the award... section 2602(b) of Public Law 97-35 (42 U.S.C. 8621(b)) through a directly-funded tribal organization...
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
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
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.
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.
NASA Astrophysics Data System (ADS)
Khajeh Salehani, Mahdi
Using the method of analytic continuation in an equivariant differential geometric setting, we exhibit two interesting families of vanishing angular momentum periodic orbits for the Newtonian three-body problem with non-uniform mass distributions having two equal masses which connect at the celebrated figure-8 orbit, exhibited by A. Chenciner and R. Montgomery (2000) in the case of equal masses, and yield a continuous family of periodic three-body motions in the plane. At one end of the family, when the two equal masses are infinitesimal and the third one reaches the value of +1, we arrive at a solution of a double Kepler problem; at the other end of the family, when the third mass is infinitesimal, we have a special case of periodic solution of a restricted three-body problem.
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)
Coral, W.; Rossi, C.; Curet, O. M.
2015-12-01
This paper presents a Differential Quadrature Element Method for free transverse vibration of a robotic fish based on a continuous and non-uniform flexible backbone with distributed masses (fish ribs). The proposed method is based on the theory of a Timoshenko cantilever beam. The effects of the masses (number, magnitude and position) on the value of natural frequencies are investigated. Governing equations, compatibility and boundary conditions are formulated according to the Differential Quadrature rules. The convergence, efficiency and accuracy are compared to other analytical solution proposed in the literature. Moreover, the proposed method has been validate against the physical prototype of a flexible fish backbone. The main advantages of this method, compared to the exact solutions available in the literature are twofold: first, smaller computational cost and second, it allows analysing the free vibration in beams whose section is an arbitrary function, which is normally difficult or even impossible with other analytical methods.
NASA Astrophysics Data System (ADS)
Dandapat, B. S.; Layek, G. C.
1999-10-01
The development of a thin liquid film under non-uniform rotation and in the presence of transverse magnetic field has been studied numerically by using the finite-difference technique under the assumption of a planar interface. Similarity variables were used to transform the axisymmetric Navier-Stokes equations into a set of coupled, nonlinear, unsteady, partial differential equations. The time-dependent free surface was mapped into a finite fixed computational domain. It is shown that the rate of film thinning slowed down by increasing either the Hartmann or Eckman number. It is also observed that a small change in the Eckman number has a stronger effect in film thinning than that for the Hartmann number. Furthermore, it is found that a faster rate of thinning can be obtain if the spinner starts impulsively and then increases its spinning rate continuously.
Research on Flow Non-Uniformity in Main Circulation Loop of a CFB Boiler with Multiple Cyclones
NASA Astrophysics Data System (ADS)
Yang, S.; Yang, H. R.; Liu, Q.; Zhang, H.; Wu, Y. X.; Yue, G. X.; Wang, Y. Z.
Maldistribution of gas-solid tow-phase flow field in circulating fluidized bed (CFB) can cause a series of problems, such as thermal deviation, wear of water walls, etc. In this study, a cold model CFB facility, which was scaled down from a commercial 300MWe CFB boiler with three cyclones placed in an array, was built up and a series of experiments were conducted the flow non-uniformity. The results showed that in CFB boiler with multiple cyclones, the distribution of bed material in the circulation loops is different and uncertain. The gas-solid two-phase flow in the furnace is unbiased, even the circulating rates in the circulation loops are different. The circulating rate in the middle loop is larger than that in the side loops. The difference is less than 10%.
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)
Zhu, Dianwen; Li, Changqing
2015-03-01
Fluorescence molecular tomography (FMT) is a significant preclinical imaging modality that has been actively studied in the past two decades. However, it remains a challenging task to obtain fast and accurate reconstruction of fluorescent probe distribution in small animals due to the large computational burden and the ill-posed nature of the inverse problem. We have recently studied a non-uniform multiplicative updating algorithm, and obtained some further speed gain with the ordered subsets (OS) method. However, increasing the number of OS leads to larger approximation errors and the speed gain from larger number of OS is marginal. In this paper, we propose to further enhance the convergence speed by incorporating the first order momentum method that uses previous iterations to achieve a quadratic convergence rate. Using cubic phantom experiment, we have shown that the proposed method indeed leads to a much faster convergence.
NASA Astrophysics Data System (ADS)
Zhu, Chunzhang; Guo, Wanlin
2011-07-01
The mechanism of phase transition and evolution in graphite under uniform compression and spherical nanoindentation along the c-direction is investigated through systematical molecular dynamics simulations. Under both the loading conditions, the soft graphite phase can sustain pressure up to 16-20 GPa, beyond which it transforms into a new phase characterized by a much higher stiffness. More and more interlayer bonds will be created in the new hard phase with the increase of the pressure until an unstable state is reached. The critical pressure to produce the quenchable hard phase with a permanent sp 3 bonding remaining after unloading is shown to be as high as ∼880 GPa under uniform compression, as opposed to only ∼75 GPa under nanoindentation. Therefore, application of non-uniform pressure is significantly more helpful for creating diamond-like sp 3 structures in graphite by cold-compressive technique.
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.
NASA Astrophysics Data System (ADS)
Swain, Ratnakar; Sahoo, Bhabagrahi
2015-11-01
In this study, the fully volume conservative simplified hydrodynamic-based variable parameter McCarthy-Muskingum (VPMM) flow transport model advocated by Perumal and Price in 2013 is extended to exclusively incorporate the distributed non-uniform lateral flow in the routing scheme accounting for compound river channel flows. The revised VPMM formulation is exclusively derived from the combined form of the de Saint-Venant's continuity and momentum equations with the spatiotemporally distributed lateral flow which is solved using the finite difference box scheme. This revised model could address the earlier model limitations of: (i) non-accounting non-uniformly distributed lateral flow, (ii) ignoring floodplain flow, and (iii) non-consideration of catchment dynamics of lateral flow generation restricting its real-time application. The efficacy of the revised formulation is tested to simulate 16 years (1980-1995) river runoff from real-time storm events under scarce morpho-hydrological data conditions in a tropical monsoon-type 48 km Bolani-Gomlai reach of the Brahmani River in eastern India. The spatiotemporally distributed lateral flows generated in real-time is computed by water balance approach accounting for catchment characteristics of normalized network area function, land use land cover classes, and soil textural classes; and hydro-meteorological variables of precipitation, soil moisture, minimum and maximum temperatures, wind speed, relative humidity, and solar radiation. The multiple error measures used in this study and the simulation results reveal that the revised VPMM model has a greater practical utility in estimating the event-based and long-term meso-scale river runoff (both discharge and its stage) at any ungauged site, enhancing its application for real-time flood estimation.
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.
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.
ter Keurs, Henk E D J; Shinozaki, Tsuyoshi; Zhang, Ying Ming; Zhang, Mei Luo; Wakayama, Yuji; Sugai, Yoshinao; Kagaya, Yutaka; Miura, Masahito; Boyden, Penelope A; Stuyvers, Bruno D M; Landesberg, Amir
2008-01-01
Starling's Law and the well-known end-systolic pressure-volume relationship (ESPVR) of the left ventricle reflect the effect of sarcomere length (SL) on stress (sigma) development and shortening by myocytes in the uniform ventricle. We show here that tetanic contractions of rat cardiac trabeculae exhibit a sigma-SL relationship at saturating [Ca2+] that depends on sarcomere geometry in a manner similar to skeletal sarcomeres and the existence of opposing forces in cardiac muscle shortened below slack length. The sigma-SL-[Ca2+]free relationships (sigma-SL-CaR) at submaximal [Ca2+] in intact and skinned trabeculae were similar, albeit that the sensitivity for Ca2+ of intact muscle was higher. We analyzed the mechanisms underlying the sigma-SL-CaR using a kinetic model where we assumed that the rates of Ca2+ binding by Troponin-C (Tn-C) and/or cross-bridge (XB) cycling are determined by SL, [Ca2+] or stress. We analyzed the correlation between the model results and steady state stress measurements at varied SL and [Ca2+] from skinned rat cardiac trabeculae to test the hypotheses that: (i) the dominant feedback mechanism is SL, stress or [Ca2+]-dependent; and (ii) the feedback mechanism regulates: Tn-C-Ca2+ affinity, XB kinetics or, unitary XB-force. The analysis strongly suggests that feedback of the number of strong XBs to cardiac Tn-C-Ca2+ affinity is the dominant mechanism that regulates XB recruitment. Application of this concept in a mathematical model of twitch-stress accurately reproduced the sigma-SL-CaR and the time course of twitch-stress as well as the time course of intracellular [Ca2+]i. Modeling of the response of the cardiac twitch to rapid stress changes using the above feedback model uniquely predicted the occurrence of [Ca2+]i transients as a result of accelerated Ca2+ dissociation from Tn-C. The above concept has important repercussions for the non-uniformly contracting heart in which arrhythmogenic Ca2+ waves arise from weakened areas in cardiac
ERIC Educational Resources Information Center
Young, Caprice
2012-01-01
Charter public schools serve a variety of roles in education reform: innovation labs, havens from failing traditional schools; and competitors for pubic resources. Education leaders have the opportunity to use high quality charter schooling to innovate not only in developing transformative schools but, more importantly, in creating great public…
NASA Astrophysics Data System (ADS)
Kawashima, I.; Toh, H.; Satake, K.
2013-12-01
A seafloor geomagnetic observatory in the northwest Pacific detected clear electromagnetic (EM) variations associated with tsunami passage from two earthquakes that occurred along the Kuril Trench (Toh et al., 2011). Previous seismological analyses indicated that the M8.3 earthquake on 15 November 2006 was an underthrust type on the landward slope of the trench, while the M8.1 earthquake on 13 January 2007 was a normal fault type on the seaward side (Ammon et al., 2008). Here we report the simulation results on the frequency dependence of those tsunami-induced EM signals observed at the seafloor, using a three-dimensional (3-D) non-uniform thin-sheet approximation by Dawson and Weaver (1979) and McKirdy, Weaver, & Dawson (1985), which can accommodate not only the inducing non-uniform source fields caused by particle motions of conducting seawater at the time of tsunami passage but also the self-induction effect within the ocean and its conductive substrata. Horizontal particle motions were calculated by Fujii and Satake (2008) with two types of hydrodynamic approximation, viz., the Boussinesq approximation and the long-wave approximation. Because the dispersion effect of each tsunami was more remarkable in the 2007 event, the observed EM variations were expected to be more compatible with the simulated EM signals using the Boussinesq approximation than the long-wave approximation. We calculated EM variations after we confirmed that synthetic plane waves in a flat ocean produced theoretically predicted harmonic EM variations well. In both approximations, the calculated EM variations associated with the initial wave of the tsunami at the time of the 2006 event are consistent with the observed ones, but the agreement became worse for the subsequent tsunami phases. As for the 2007 event, the calculated EM variations were less consistent compared with the 2006 event irrespective to the hydrodynamic approximations used. This can be due to the current limitation of thin
NASA Astrophysics Data System (ADS)
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" (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
NASA Astrophysics Data System (ADS)
Riauka, Terence A.; Hooper, H. Richard; Gortel, Zbigniew W.
1996-07-01
Experimental tests for non-uniform attenuating media are performed to validate theoretical expressions for the photon detection kernel, obtained from a recently proposed analytical theory of photon propagation and detection for SPECT. The theoretical multi-dimensional integral expressions for the photon detection kernel, which are computed numerically, describe the probability that a photon emitted from a given source voxel will trigger detection of a photon at a particular projection pixel. The experiments were performed using a cylindrical water-filled phantom with large cylindrical air-filled inserts to simulate inhomogeneity of the medium. A point-like, a short thin cylindrical and a large cylindrical radiation source of were placed at various positions within the phantom. The values numerically calculated from the theoretical kernel expressions are in very good agreement with the experimentally measured data. The significance of Compton-scattered photons in planar image formation is discussed and highlighted by these results. Using both experimental measurements and the calculated values obtained from the theory, the kernel's size is investigated. This is done by determining the square pixel neighbourhood of the gamma camera that must be connected to a particular radiation source voxel to account for a specific fraction of all counts recorded at all camera pixels. It is shown that the kernel's size is primarily dependent upon the source position and the properties of the attenuating medium through Compton scattering events, with 3D depth-dependent collimator resolution playing an important but secondary role, at least for imaging situations involving parallel hole collimation. By considering small point-like sources within a non-uniform elliptical phantom, approximating the human thorax, it is demonstrated
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
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
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
NASA Astrophysics Data System (ADS)
Kim, Jaecheon; Kim, Yong Kyun; Kim, Soon Young; Kim, Jong Kyung
2007-09-01
A new analytic approach considering both electric field and ion-pair non-uniformity has been proposed to accurately analyze the design characteristics of an ionization chamber and to interpret measurements. It is commonly assumed that ion-pairs are generated uniformly in the air volume, but such an assumption ignores various source and geometry conditions. The new approach was applied to angular dependence analysis and to polarity effect assessment in an ionization chamber. For the angular dependence analysis, whole, uniform, and non-uniform output currents were calculated as a function of the irradiation angle for an 241Am gamma-ray source. The non-uniform output current proposed in this paper was found to be closer to the measured one. This is because the non-uniform output current takes into account the ion-pair distribution in the air volume as well as the active volume determined by the electric field. For the polarity effect assessment, the amount of field distortion due to potential difference and actual current difference was calculated. Previous methods cannot appropriately estimate the variation of polarity effect because they ignore the influence of the ion-pair distribution. The polarity effect assessment using the non-uniform output current can be more useful for obtaining the practical current difference, because this assessment considers both the variation of active volume and the ion-pair non-uniformity according to source conditions such as the irradiation angle and the distance. It is important to precisely calculate not only the active volume, but also the variation in the ion-pair distribution.
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.
Van de Wyer, Nicolas; Schram, Christophe; Van Dyck, Dries; Dierckx, Marc
2015-07-01
SCK.CEN, the Belgian Nuclear Research Center, is developing MYRRHA, a generation IV liquid metal cooled nuclear research reactor. As the liquid metal coolant is opaque to light, normal visual feedback during fuel manipulations is not available and must therefore be replaced by a system that is not hindered by the opacity of the coolant. In this respect ultrasonic based instrumentation is under development at SCK.CEN to provide feedback during operations under liquid metal. One of the tasks that will be tackled using ultrasound is the detection and localization of a potentially lost fuel assembly. In this application, the distance between ultrasonic sensor and target may be as large as 2.5 m. At these distances, non uniform velocity and temperature fields in the liquid metal potentially influence the propagation of the ultrasonic signals, affecting the performance of the ultrasonic systems. In this paper, we investigate how relevant temperature and velocity gradients inside the liquid metal influence the propagation of ultrasonic waves. The effect of temperature and velocity gradients are simulated by means of a newly developed numerical ray-tracing model. The performance of the model is validated by dedicated water experiments. The setup is capable of creating velocity and temperature gradients representative for MYRRHA conditions. Once validated in water, the same model is used to make predictions for the effect of gradients in the MYRRHA liquid metal environment. (authors)
NASA Astrophysics Data System (ADS)
Chen, Zaigao; Wang, Jianguo; Wang, Yue
2015-01-01
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 TM020 mode of reflector to higher-order TM021 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.
Lapelosa, Mauro; Abrams, Cameron F
2013-10-01
Rare events between states in complex systems are fundamental in many scientific fields and can be studied by building reaction pathways. A theoretical framework to analyze reaction pathways is provided by transition-path theory (TPT). The central object in TPT is the committor function, which is found by solution of the backward-Kolmogorov equation on a given potential. Once determined, the committor can be used to calculate reactive fluxes and rates, among other important quantities. We demonstrate here that the committor can be calculated using the method of finite elements on non-uniform meshes. We show that this approach makes it feasible to perform TPT calculations on 3D potentials because it requires many fewer degrees of freedom than a regular-mesh finite-difference approach. In various illustrative 2D and 3D problems, we calculate the committor function and reaction rates at different temperatures, and we discuss effects of temperatures and simple entropic barriers on the structure of the committor and the reaction rate constants.
Donor impurity states in a non-uniform quantum strip: Geometrical and electro-magnetic field effects
NASA Astrophysics Data System (ADS)
Suaza, Y. A.; Fonnegra-García, D.; Fulla, M. R.; Salazar-Santa, J. D.; Marín, J. H.
2017-03-01
The neutral donor energy structure in non-uniform height quantum strip under the presence of crossed electric and magnetic fields is studied. The quantum strip height has been modeled by including a phenomenological two-parametric function. The first of these parameters is related to the number of structural hills present on the nano-strip, while the second one allows us to control the hills height. We solve the Schrödinger equation by considering specific quantum strips whose height-to-base aspect ratio is very small, which makes possible to calculate numerically the energy structure trough the adiabatic approximation and the exact diagonalization method. In limit cases, our results are in good agreement with those ones previously reported. Periodic oscillations of the ground state energy with magnetic field strength can be tuned by applied electric field which also yields an anti-crossing of the energy levels in a quantum strip with two hills. The energy level structure are strongly sensitive to changes of nano-strip geometrical factors.
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
2015-08-15
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.
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.
NASA Astrophysics Data System (ADS)
Gamba, Mirko; Miller, Victor A.; Mungal, M. Godfrey; Hanson, Ronald K.
2015-08-01
Single-excitation, dual-band-collection toluene planar laser-induced fluorescence (PLIF) is used to measure temperature and number density (or partial pressure) fields in non-uniform supersonic complex flows in the presence of mixing and compressibility. The study provides a quantitative evaluation of the technique in transverse jets in supersonic crossflow (JISCF). It is found that toluene PLIF is highly effective in visualizing the structure of supersonic flows and that temperature can be accurately inferred with acceptable signal-to-noise ratios (of order 30) even when mixing occurs. The technique was applied to several JISCFs that differ by jet fluid properties with resulting different structures. In the presence of compressibility and mixing, it is found that the PLIF signal is non-unique, a feature that is used to identify the mixing region of the transverse jet. Measurement errors due to camera registration errors have also been quantified. Because of the complexity of the flowfield, it is found that minute misalignment (<0.1 pixels) between the two PLIF images can introduce measurable errors on the order of tens of Kelvins and significant errors in temperature gradients.
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.
Fanning Out of the Solar f-mode in the Presence of Non-uniform Magnetic Fields?
NASA Astrophysics Data System (ADS)
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.
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)
Kubiak, K. J.; Wilson, M. C. T.; Castrejón-Pita, J. R.; Hutchings, I. M.
2011-11-01
Contact Angle Hysteresis (CAH) is usually attributed to surface heterogeneity, contact line pinning, adsorption or interdiffusion. A model of CAH developed recently by Kubiak & Wilson is demonstrated using the lattice Boltzmann method. The model is based on the dynamic surface heterogeneity, reorientation of surface molecules under wetting liquid, physical roughness, chemical heterogeneity and liquid adhesion and evaporation. Once the surface is wetted, the local static contact angle (CA) changes from its advancing value to match the receding static CA over time Ta. When the contact line retracts, the surface recovers its initial properties corresponding to the advancing static CA over time period Te, which corresponds to the physical evaporation. Further development of the model to include surface roughness and chemical heterogeneity is presented. The model shows good agreement with experimental results for several practical configurations i.e. droplet impact and coalescence, drops on tilted surface, and drops on superhydrophobic and non-uniform surfaces etc. The extended model exhibits great potential for predictive modelling using the lattice Boltzmann method, but can be also implemented in other schemes. Research supported by EPSRC EP/F065019/1 and EP/H018913/1.
NASA Astrophysics Data System (ADS)
Givli, Sefi; Bhattacharya, Kaushik
2009-02-01
A theoretical framework for predicting the macroscopic behavior of a muscle myofibril based on the collective behavior of sarcomeres is presented. The analysis is accomplished by rigorously transforming the nonlinear dynamics of an assemblage of sarcomeres into a partial differential equation for the probability distribution function of sarcomere lengths in the presence of stochastic temporal fluctuations and biological variability. This enables the study of biologically relevant specimens with reasonable computational effort. The model is validated by a comparison to quantitative experimental results. Further, it reproduces experimental observations that cannot be explained by standard single sarcomere models, and provides new insights into muscle function and muscle damage during cyclic loading. We show that the accumulation of overstretched sarcomeres, which is related to muscle damage, depends on a delicate interplay between the dynamics of a large number of sarcomeres and the load characteristics, such as its magnitude and frequency. Further, we show that biological variability rather than stochastic fluctuations are the main source for sarcomere non-uniformities.
NASA Astrophysics Data System (ADS)
Hsuen, Hsiao-Kuo
The performance equations for cathodes of polymer electrolyte fuel cells (PEFCs) that describe the dependence of cathode potential on current density are developed. Formulation of the performance equations starts from the reduction of a one-dimensional model that considers, in detail, the potential losses pertinent to the limitations of electron conduction, oxygen diffusion, proton migration, and the oxygen reduction reaction. In particular, non-uniform accumulation of liquid water in the gas diffuser, which partially blocks the gas channels and imposes a greater resistance for oxygen transport, is taken into account. Reduction of the one-dimensional model is implemented by approximating the oxygen concentration profile in the catalyst layer with a parabolic polynomial or a piecewise parabolic one determined by the occurrence of oxygen depletion. The final forms of the equations are obtained by applying the method of weighted residuals over the catalyst layer. The weighting function is selected in such a way that the weighted residuals can be analytically integrated. Potential losses caused by the various limiting processes can be quantitatively estimated by the performance equations. Thus, they provide a convenient diagnostic tool for the cathode performance. Computational results reveal that the performance equations agree well with the original one-dimensional model over an extensive range of parameter values. This indicates that the present performance equations can be used as a substitute for the one-dimensional model to provide quantitatively correct predictions for the cathode performance of PEFCs.
NASA Astrophysics Data System (ADS)
Xia, Huanxiong; Xiang, Dong; Yang, Wang; Mou, Peng
2014-12-01
Low-temperature plasma technique is one of the critical techniques in IC manufacturing process, such as etching and thin-film deposition, and the uniformity greatly impacts the process quality, so the design for the plasma uniformity control is very important but difficult. It is hard to finely and flexibly regulate the spatial distribution of the plasma in the chamber via controlling the discharge parameters or modifying the structure in zero-dimensional space, and it just can adjust the overall level of the process factors. In the view of this problem, a segmented non-uniform dielectric module design solution is proposed for the regulation of the plasma profile in a CCP chamber. The solution achieves refined and flexible regulation of the plasma profile in the radial direction via configuring the relative permittivity and the width of each segment. In order to solve this design problem, a novel simulation-based auto-design approach is proposed, which can automatically design the positional sequence with multi independent variables to make the output target profile in the parameterized simulation model approximate the one that users preset. This approach employs an idea of quasi-closed-loop control system, and works in an iterative mode. It starts from initial values of the design variable sequences, and predicts better sequences via the feedback of the profile error between the output target profile and the expected one. It never stops until the profile error is narrowed in the preset tolerance.
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
Graichen, Uwe; Eichardt, Roland; Fiedler, Patrique; Strohmeier, Daniel; Zanow, Frank; Haueisen, Jens
2015-01-01
Important requirements for the analysis of multichannel EEG data are efficient techniques for signal enhancement, signal decomposition, feature extraction, and dimensionality reduction. We propose a new approach for spatial harmonic analysis (SPHARA) that extends the classical spatial Fourier analysis to EEG sensors positioned non-uniformly on the surface of the head. The proposed method is based on the eigenanalysis of the discrete Laplace-Beltrami operator defined on a triangular mesh. We present several ways to discretize the continuous Laplace-Beltrami operator and compare the properties of the resulting basis functions computed using these discretization methods. We apply SPHARA to somatosensory evoked potential data from eleven volunteers and demonstrate the ability of the method for spatial data decomposition, dimensionality reduction and noise suppression. When employing SPHARA for dimensionality reduction, a significantly more compact representation can be achieved using the FEM approach, compared to the other discretization methods. Using FEM, to recover 95% and 99% of the total energy of the EEG data, on average only 35% and 58% of the coefficients are necessary. The capability of SPHARA for noise suppression is shown using artificial data. We conclude that SPHARA can be used for spatial harmonic analysis of multi-sensor data at arbitrary positions and can be utilized in a variety of other applications. PMID:25885290
Shao, Chenxi; Liu, Qingqing; Wang, Tingting; Yin, Peifeng; Wang, Binghong
2013-09-01
Time series is widely exploited to study the innate character of the complex chaotic system. Existing chaotic models are weak in modeling accuracy because of adopting either error minimization strategy or an acceptable error to end the modeling process. Instead, interpolation can be very useful for solving differential equations with a small modeling error, but it is also very difficult to deal with arbitrary-dimensional series. In this paper, geometric theory is considered to reduce the modeling error, and a high-precision framework called Series-NonUniform Rational B-Spline (S-NURBS) model is developed to deal with arbitrary-dimensional series. The capability of the interpolation framework is proved in the validation part. Besides, we verify its reliability by interpolating Musa dataset. The main improvement of the proposed framework is that we are able to reduce the interpolation error by properly adjusting weights series step by step if more information is given. Meanwhile, these experiments also demonstrate that studying the physical system from a geometric perspective is feasible.
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.
Ray-tracing WKB analysis of Whistler waves in non-uniform magnetic fields applied to space thrusters
NASA Astrophysics Data System (ADS)
Cardinali, A.; Melazzi, D.; Manente, M.; Pavarin, D.
2014-02-01
Radiofrequency magnetized cylindrical plasma sources are proposed for the development of space thrusters, whose thrust efficiency and specific impulse depend on the power coupled into the plasma. At this stage of research, emphasis has been on the absorption of Whistler wave energy by non-uniform plasmas but not much on the role played by the magneto-static confinement field, considered uniform, constant and aligned with the axis of the source. We present RAYWh (RAY-tracing Whistler), a three-dimensional (3D) ray-tracing solver for electromagnetic propagation and power deposition in cylindrical plasma sources for space plasma thrusters, where actual magnetic confinement configurations along with plasma density profiles are included. The propagation and absorption of Whistler waves are investigated by solving the 3D Maxwell-Vlasov model equations by a Wentzel-Kramers-Brillouin (WKB) asymptotic expansion. The reduced set of equations for the wave phase and for the square amplitude of the electric field is solved numerically by means of a modified Runge-Kutta algorithm. Unexpected cut-offs, resonances, radial reflections, mode conversions and power deposition profile of the excited waves are found, when realistic confinement magnetic fields are considered. An analysis of the influence of axial wavenumbers and the axial length of the system on the power deposition is presented.
Leverage points for sustainability transformation.
Abson, David J; Fischer, Joern; Leventon, Julia; Newig, Jens; Schomerus, Thomas; Vilsmaier, Ulli; von Wehrden, Henrik; Abernethy, Paivi; Ives, Christopher D; Jager, Nicolas W; Lang, Daniel J
2017-02-01
Despite substantial focus on sustainability issues in both science and politics, humanity remains on largely unsustainable development trajectories. Partly, this is due to the failure of sustainability science to engage with the root causes of unsustainability. Drawing on ideas by Donella Meadows, we argue that many sustainability interventions target highly tangible, but essentially weak, leverage points (i.e. using interventions that are easy, but have limited potential for transformational change). Thus, there is an urgent need to focus on less obvious but potentially far more powerful areas of intervention. We propose a research agenda inspired by systems thinking that focuses on transformational 'sustainability interventions', centred on three realms of leverage: reconnecting people to nature, restructuring institutions and rethinking how knowledge is created and used in pursuit of sustainability. The notion of leverage points has the potential to act as a boundary object for genuinely transformational sustainability science.
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…
NASA Astrophysics Data System (ADS)
Smith, E.; Wilding, M. J.
EXPERIMENTAL results on the stability of circumferential growth of through-wall cracks in brass tubes, show that non-uniform bending can adversely affect the crack stability criterion. The results are relevant to the important technological problem of crack stability in 304 stainless steel pipes used in Boiling Water Reactors.
NASA Astrophysics Data System (ADS)
Assuncao, Charles Sostenes; Tavares, Roberto Parreiras; Oliveira, Guilherme; Pereira, Luiz Carlos
2015-02-01
In the present work, the water flux densities of nozzles with flat jet and full cone jet were experimentally measured using an apparatus in industrial scale that reproduces the secondary cooling of the continuous casting of round billets of Vallourec Tubos do Brasil. A mathematical function was defined to express the water flux density in both longitudinal and angular directions of the strand. A mathematical model for heat transfer and solidification for the continuous casting of round billets was developed applying the experimental water flux density profile, establishing a non-uniform water distribution approach. The mathematical model was validated by experimental measurements of the billet superficial temperature, performed at the industrial plant. The results of the mathematical model using both uniform and non-uniform water flux density approaches were compared. The non-uniform water distribution approach enabled to identify important variations of the heat transfer coefficients and the billet temperatures, especially in the first cooling zones where the steel temperature is higher, and to assess more accurately the local effects of the water distribution on the thermal behavior of the strand. The non-uniform water flux density approach applied to the mathematical model was a useful and more accurate tool to improve the comprehension of the thermal behavior of the steel along the secondary cooling.
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)
Wietholt, Christian; Hsiao, Ing-Tsung; Chen, Chin-Tu
2007-03-01
Small animal SPECT using low energy photons of I-125 and approaching resolutions of microscopic levels, imaging parameters such as pinhole edge penetration, detector blur, geometric response, detector and pinhole misalignment, and gamma photon attenuation and scatter can have increasingly noticeable and/or adverse effects on reconstructed image quality. Iterative reconstruction algorithms, the widelyaccepted standard for emission tomography, allow modeling of such parameters through a system matrix. For this Monte Carlo simulation study, non-uniform attenuation correction was added to the existing system model. The model was constructed using ray-tracing and further included corrections for edge penetration, detector blur, and geometric aperture response. For each ray passing through different aperture locations, this method attenuates a voxel's contribution to a detector element along the photon path, which is then weighted according to a pinhole penetration model. To lower the computational and memory expenses, symmetry along the detector axes and an incremental storage scheme for the system model were used. For evaluating the nonuniform attenuation correction method, 3 phantoms were designed of which projection images were simulated using Monte Carlo methods. The first phantom was used to examined skin artifacts, the second to simulate attenuation by bone, and the third to generate artifacts of an air-filled space surrounded by soft tissue. In reconstructions without attenuation correction, artifacts were observed with up to a 40% difference in activity. These could be corrected using the implemented method, although in one case overcorrection occurred. Overall, attenuation correction improved reconstruction accuracy of the radioisotope distribution in the presence of structural differences.
NASA Astrophysics Data System (ADS)
Omidi, N.; Russell, C. T.; Jian, L.; Isenberg, P. A.; Wei, H.
2013-12-01
The presence of ions with perpendicular temperature larger than parallel in the corona is expected to result in the generation of ion cyclotron waves. Spacecraft observations in the interplanetary medium provide evidence for the presence of ion cyclotron waves generated near the Sun. In this presentation we examine the possibility that the observed ion cyclotron waves are generated in the corona and propagate into the interplanetary medium. To this end, we perform 2.5-D electromagnetic hybrid (kinetic ions, fluid electrons) simulations with non-uniform magnetic field. By initializing ions with perpendicular temperature larger than parallel in a finite region of space, we investigate the generation of ion cyclotron waves in the high magnetic field region and their propagation to larger radial distances with weaker magnetic field strength. Specifically, we examine the propagation properties of the waves and the extent to which they are impacted by the presence of non-uninform magnetic field and nonlinear processes. Results show that at least in some cases, wave propagation is coupled to the outward motion (along the magnetic field) of the ions responsible for the generation of the waves. In such cases, wave generation may be ongoing for regions much larger than the initial source region where ions with temperature anisotropy are initialized. In this study we examine how the properties of ion cyclotron waves (e.g. spectral power, polarization) and their radial dependence vary with changes in the magnetic field model, level of temperature anisotropy, the nature of source ions (e.g. O5+; He++) and relative speed between the various ion species.
NASA Astrophysics Data System (ADS)
Nazarian, N.; Kleissl, J. P.
2014-12-01
As urbanization progresses, microclimate modifications are also aggravated and the increasing environmental concerns call for more sophisticated methods of urban microclimate analysis. Comprehensive numerical simulations for a clear summer day in southern California are performed in a compact low-rise urban environment. The effect of realistic unsteady, non-uniform thermal forcing, that is caused by solar insolation and inter-building shadowing on thermal and flow conditions are analyzed based on Algebraic Wall-Modeled Large Eddy Simulation (LES) model. The urban thermal field is influenced by urban density, material properties and local weather conditions, as well as urban canyon flow. Urban canyon conditions are translated into vertical and horizontal bulk Richardson numbers indicating atmospheric instability and solar tilt with respect to the momentum forcing of the canyon vortex, respectively. The effect of roof heating is found to be critical on the vortex formation between buildings when the vertical bulk Richardson number is low. Variations of Convective Heat Transfer Coefficients (CHTCs) along building walls are studied and the street canyon ventilation performance is characterized by the mean of air exchange rate (ACH). It is found that volumetric air exchange from street canyons, as well as the distribution of heat transfer along the wall depends strongly on the three-dimensional orientation of the heated wall in relation to wind direction. For example, air removal increases by surface heating and is larger when the leeward wall is heated. In summary, we demonstrate the importance of considering complex realistic conditions on 3-dimensional thermal and momentum fields in Urban Environments.
NASA Astrophysics Data System (ADS)
Flynn, Ryan
2007-12-01
The distribution of biological characteristics such as clonogen density, proliferation, and hypoxia throughout tumors is generally non-uniform, therefore it follows that the optimal dose prescriptions should also be non-uniform and tumor-specific. Advances in intensity modulated x-ray therapy (IMXT) technology have made the delivery of custom-made non-uniform dose distributions possible in practice. Intensity modulated proton therapy (IMPT) has the potential to deliver non-uniform dose distributions as well, while significantly reducing normal tissue and organ at risk dose relative to IMXT. In this work, a specialized treatment planning system was developed for the purpose of optimizing and comparing biologically based IMXT and IMPT plans. The IMXT systems of step-and-shoot (IMXT-SAS) and helical tomotherapy (IMXT-HT) and the IMPT systems of intensity modulated spot scanning (IMPT-SS) and distal gradient tracking (IMPT-DGT), were simulated. A thorough phantom study was conducted in which several subvolumes, which were contained within a base tumor region, were boosted or avoided with IMXT and IMPT. Different boosting situations were simulated by varying the size, proximity, and the doses prescribed to the subvolumes, and the size of the phantom. IMXT and IMPT were also compared for a whole brain radiation therapy (WBRT) case, in which a brain metastasis was simultaneously boosted and the hippocampus was avoided. Finally, IMXT and IMPT dose distributions were compared for the case of non-uniform dose prescription in a head and neck cancer patient that was based on PET imaging with the Cu(II)-diacetyl-bis(N4-methylthiosemicarbazone (Cu-ATSM) hypoxia marker. The non-uniform dose distributions within the tumor region were comparable for IMXT and IMPT. IMPT, however, was capable of delivering the same non-uniform dose distributions within a tumor using a 180° arc as for a full 360° rotation, which resulted in the reduction of normal tissue integral dose by a factor of
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.
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.
... can be found on the web, through local libraries, your health care provider, and the yellow pages under "social service organizations." AIDS - resources Alcoholism - resources Allergy - resources ...
State Incentive Funding: Leveraging Quality.
ERIC Educational Resources Information Center
Holland, Barbara
1990-01-01
This newsletter summarizes the debate on the use of state-level initiatives as levers to effect fundamental changes in higher education. It provides several perspectives on the use of incentive/enhancement programs to achieve state higher education goals. The concept of budgetary leverage is outlined, and the growth in enhancement programs…
NASA Astrophysics Data System (ADS)
Guha, Abhijit; Sengupta, Sayantan
2014-03-01
In this article, the fluid dynamics of work transfer within the narrow spacing (usually of the order of 100 μm) of multiple concentric discs of a Tesla disc turbomachine (turbine or compressor) has been analysed theoretically and computationally. Both the overall work transfer and its spatial development have been considered. It has been established that the work transfer mechanism in a Tesla disc turbomachine is very different from that in a conventional turbomachine, and the formulation of the Euler's work equation for the disc turbomachine contains several conceptual subtleties because of the existence of complex, three dimensional, non-uniform, viscous flow features. A work equivalence principle has been enunciated, which establishes the equality between the magnitudes of work transfer determined rigorously from two different approaches—one based on the shear stress acting on the disc surfaces and the other based on the change in angular momentum of the fluid. Care is needed in identifying the shear stress components that are responsible for the generation or absorption of useful power. It is shown from the Reynolds transport theorem that mass-flow-averaged tangential velocities (as opposed to the normally used area-averaged values) must be used in determining the change in angular momentum; the calculation has to be carefully formulated since both radial velocity (that determines throughput) and tangential velocity (that generates torque) depend strongly on the coordinate perpendicular to the disc surfaces. The principle of work transfer has been examined both in the absolute and relative frames of reference, revealing the subtle role played by Coriolis force. The concept of a new non-dimensional quantity called the torque potential fraction (Δ tilde H) is introduced. The value of Δ tilde H at any radial position increases with a decrease in inter-disc spacing. The computational fluid dynamic analysis shows that, for small value of inter-disc spacing and
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
12 CFR 567.8 - Leverage ratio.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 12 Banks and Banking 6 2012-01-01 2012-01-01 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 a composite rating of 1, as defined in § 516.3 of this chapter, shall consist of a ratio of...
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... § 167.8 Leverage ratio. (a) The minimum leverage capital requirement for a Federal savings association assigned a composite rating of 1, as defined in § 116.3 of this chapter, shall consist of a ratio of...
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 a composite rating of 1, as defined in § 516.3 of this chapter, shall consist of a ratio of...
12 CFR 567.8 - Leverage ratio.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 12 Banks and Banking 5 2011-01-01 2011-01-01 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 a composite rating of 1, as defined in § 516.3 of this chapter, shall consist of a ratio of...
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... § 167.8 Leverage ratio. (a) The minimum leverage capital requirement for a Federal savings association assigned a composite rating of 1, as defined in § 116.3 of this chapter, shall consist of a ratio of...
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... § 167.8 Leverage ratio. (a) The minimum leverage capital requirement for a Federal savings association assigned a composite rating of 1, as defined in § 116.3 of this chapter, shall consist of a ratio of...
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... § 567.8 Leverage ratio. (a) The minimum leverage capital requirement for a savings association assigned a composite rating of 1, as defined in § 516.3 of this chapter, shall consist of a ratio of...
12 CFR 567.8 - Leverage ratio.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 12 Banks and Banking 6 2014-01-01 2012-01-01 true Leverage ratio. 567.8 Section 567.8 Banks and... § 567.8 Leverage ratio. (a) The minimum leverage capital requirement for a savings association assigned a composite rating of 1, as defined in § 516.3 of this chapter, shall consist of a ratio of...
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.
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.
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.
The Gas Motion Due To Non-Uniform Heating By 3He(n,p)3H Reactions In The Nuclear-Pumped3He -Lasers
Cetin, Fuesun
2007-04-23
In the nuclear pumped-lasers, the passage of these energetic charged particles through gas results in a non-uniform volumetric energy deposition. This spatial non-uniformity induces a gas motion, which results in density and hence refractive index gradients that affects the laser's optical behaviour. The motion of 3He gas in a closed cavity is studied when it experiences transient and spatially non-uniform volumetric heating caused by the passage of 3He(n,p)3H reaction products. Gas motion is described by the radial velocity field of gas flow. Spatial and temporal variations of radial gas velocity are calculated for various tube parameters by using a dynamic energy deposition model. In the calculations, it is assumed that the laser tube is irradiated with neutrons from the pulse at a peak power of 1200 MW corresponding to a maximum thermal neutron flux of 8x1016 n / cm2sn in the central channel of ITU TRIGA Mark II Reactor. Results are examined.
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.
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
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.
Clark, P.E.; Zhu, Q.
1995-12-31
Recently, the flow of fluids into a fracture from a point source has been the subject of several different papers. Cleary and Fonseca first suggested that convective transport should play a major role in the placement of proppant when the flow into a fracture was from a point source. Clark and Courington presented data showing that for non-viscosified fluids convection was the dominant mechanism of transport. However, they showed, that for uniform fractures, viscosifying the fluid made a large difference in the transport mechanism. In a later paper, Clark and Zhu presented data for non-uniform fractures and viscosified fluids weighted with either salt or silica flour that showed that the presence of minor non-uniformities serve to negate the effect of convection even more than viscosifying the fluids. In this work, the authors have extended the work presented in the previous two papers to high viscosity Newtonian fluids and crosslinked fluids. The experiments have all been done with various concentrations of silica flour to simulate added proppant. Both changing the nature of the non-uniformities and crosslinking the polymer solution have a profound affect on the flow into the fracture and the convective process.
7 CFR 4290.1130 - Leverage fees payable by RBIC.
Code of Federal Regulations, 2013 CFR
2013-01-01
...) 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 fee... 7 Agriculture 15 2013-01-01 2013-01-01 false Leverage fees payable by RBIC. 4290.1130 Section...
7 CFR 4290.1130 - Leverage fees payable by RBIC.
Code of Federal Regulations, 2010 CFR
2010-01-01
...) 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 fee... 7 Agriculture 15 2010-01-01 2010-01-01 false Leverage fees payable by RBIC. 4290.1130 Section...
7 CFR 4290.1130 - Leverage fees payable by RBIC.
Code of Federal Regulations, 2012 CFR
2012-01-01
...) 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 fee... 7 Agriculture 15 2012-01-01 2012-01-01 false Leverage fees payable by RBIC. 4290.1130 Section...
7 CFR 4290.1130 - Leverage fees payable by RBIC.
Code of Federal Regulations, 2014 CFR
2014-01-01
...) 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 fee... 7 Agriculture 15 2014-01-01 2014-01-01 false Leverage fees payable by RBIC. 4290.1130 Section...
7 CFR 4290.1130 - Leverage fees payable by RBIC.
Code of Federal Regulations, 2011 CFR
2011-01-01
...) 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 fee... 7 Agriculture 15 2011-01-01 2011-01-01 false Leverage fees payable by RBIC. 4290.1130 Section...
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.
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.
NASA Astrophysics Data System (ADS)
Chen, J.-S.; Lai, G.-X.
2009-04-01
The morphological evolution of a chemical dissolution front is an important topic in geological processes and engineering practices. Although previous studies have extensively presented a number of numerical models which couples a system of nonlinear governing equations of porosity change due to mineral dissolution, the conservations of groundwater flow and transport of chemical species to investigate the morphological pattern of a chemical dissolution front within a fluid-saturated porous medium, whereas the mechanical dispersion effect has generally been neglected in the model development. This study addresses the effects of mechanical dispersion on the morphological evolution of a chemical dissolution front for a variety of cases. Mechanical dispersion processes is incorporated with the coupled nonlinear governing equation system so as to rebuild a newly numerical model. The results of numerical simulations demonstrate that mechanical dispersion has pronounced impacts on the morphological pattern of the chemical dissolution front. For single local non-uniformity case, mechanical dispersion reduces the finger length of an unstable single-fingering front or retains the shape of a stable planar front while speeding up the front advancement. In the case of two local non-uniformities, adding mechanical dispersion with different flow conditions can yield one of the following results: (1) the shape of the stable planar front is maintained but its advancement is accelerated; (2) the shape of the unstable single-fingering front is maintained but its length is reduced; (3) the unstable double-fingering front is merged into an unstable single-fingering front; and (4) the shape of the unstable double-fingering front is preserved but its fingering length is reduced.. A comparison between the behavior diagrams of dissolution front morphology (with and without considering mechanical dispersion) shows that the double-fingering front occurs under condition where the upstream
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)
Rodríguez-González, J.; Billen, M. I.; Negredo, A. M.
2012-12-01
Forces driving plate tectonics are reasonably well known but some factors controlling the dynamics and the geometry of subduction processes are still poorly understood. The effect of the thermal state of the subducting and overriding plates on the slab dip have been systematically studied in previous works by means of 2D and 3D numerical modeling. These models showed that kinematically-driven slabs subducting under a cold overriding plate are affected by an increased hydrodynamic suction, due to the lower temperature of the mantle wedge, which leads to a lower subduction angle, and eventually to the formation of flat slab segments. In these models the subduction is achieved by imposing a constant velocity at the top of the overriding plate, which may lead to unrealistic results. Here we present the results of 3D non-Newtonian thermo-mechanical numerical models, considering a dynamically-driven self-sustained subduction, to test the influence of a non-uniform overriding plate. Variations of the thermal state of the overriding plate along the trench cause variation in the hydrodynamic suction, which lead to variations of the slab dip along strike (Fig. 1) and a significant trench-parallel flow. When the material can flow around the edges of the slab, through the addition of lateral plates, the trench parallel flow is enhanced (Fig. 2), whereas the variations on the slab dip are diminished.; Effect of a non-uniform overriding plate on slab-dip. 3D view of the 1000 C isosurface. ; Effect of a non-uniform overriding plate on trench-parallel flow. Map view of the slab at different depths and times, showing the viscosity (colormap) and the velocity (arrows).
NASA Astrophysics Data System (ADS)
Liu, Fengshan; Rogak, Steven; Snelling, David R.; Saffaripour, Meghdad; Thomson, Kevin A.; Smallwood, Gregory J.
2016-11-01
Multimode pulsed Nd:YAG lasers are commonly used in auto-compensating laser-induced incandescence (AC-LII) measurements of soot in flames and engine exhaust as well as black carbon in the atmosphere. Such lasers possess a certain degree of fluence non-uniformity across the laser beam even with the use of beam shaping optics. Recent research showed that the measured volume fraction of ambient-temperature soot using AC-LII increases significantly, by about a factor of 5-8, with increasing the laser fluence in the low-fluence regime from a very low fluence to a relatively high fluence of near sublimation. The causes of this so-called soot volume fraction anomaly are currently not understood. The effects of laser fluence non-uniformity on the measured soot volume fraction using AC-LII were investigated. Three sets of LII experiments were conducted in the exhaust of a MiniCAST soot generator under conditions of high elemental carbon using Nd:YAG lasers operated at 1064 nm. The laser beams were shaped and relay imaged to achieve a relatively uniform fluence distribution in the measurement volume. To further homogenize the laser fluence, one set of LII experiments was conducted by using a diffractive optical element. The measured soot volume fractions in all three sets of LII experiments increase strongly with increasing the laser fluence before a peak value is reached and then start to decrease at higher fluences. Numerical calculations were conducted using the experimental laser fluence histograms. Laser fluence non-uniformity is found partially responsible for the soot volume fraction anomaly, but is insufficient to explain the degree of soot volume fraction anomaly observed experimentally. Representing the laser fluence variations by a histogram derived from high-resolution images of the laser beam energy profile gives a more accurate definition of inhomogeneity than a simple averaged linear profile across the laser beam.
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.
Meng, L. J.; Li, Nan
2016-01-01
This paper presents a non-uniform object-space pixelation (NUOP) approach for image reconstruction using the penalized maximum likelihood methods. This method was developed for use with a single photon emission microscope (SPEM) system that offers an ultrahigh spatial resolution for a targeted local region inside mouse brain. In this approach, the object-space is divided with non-uniform pixel sizes, which are chosen adaptively based on object-dependent criteria. These include (a) some known characteristics of a target-region, (b) the associated Fisher Information that measures the weighted correlation between the responses of the system to gamma ray emissions occurred at different spatial locations, and (c) the linear distance from a given location to the target-region. In order to quantify the impact of this non-uniform pixelation approach on image quality, we used the Modified Uniform Cramer-Rao bound (MUCRB) to evaluate the local resolution-variance and bias-variance tradeoffs achievable with different pixelation strategies. As demonstrated in this paper, an efficient object-space pixelation could improve the speed of computation by 1–2 orders of magnitude, whilst maintaining an excellent reconstruction for the target-region. This improvement is crucial for making the SPEM system a practical imaging tool for mouse brain studies. The proposed method also allows rapid computation of the first and second order statistics of reconstructed images using analytical approximations, which is the key for the evaluation of several analytical system performance indices for system design and optimization.
Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; ...
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
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.
NASA Astrophysics Data System (ADS)
Hariri, Saman; Mokhtari, Mojtaba; Gerdroodbary, M. Barzegar; Fallah, Keivan
2017-02-01
In this article, a three-dimensional numerical investigation is performed to study the effect of a magnetic field on a ferrofluid inside a tube. This study comprehensively analyzes the influence of a non-uniform magnetic field in the heat transfer of a tube while a ferrofluid (water with 0.86 vol% nanoparticles (Fe3O4) is let flow. The SIMPLEC algorithm is used for obtaining the flow and heat transfer inside the tube. The influence of various parameters, such as concentration of nanoparticles, intensity of the magnetic field, wire distance and Reynolds number, on the heat transfer is investigated. According to the obtained results, the presence of a non-uniform magnetic field significantly increases the Nusselt number (more than 300%) inside the tube. Also, the magnetic field induced by the parallel wire affects the average velocity of the ferrofluid and forms two strong eddies in the tube. Our findings show that the diffusion also raises as the concentration of the nanoparticle is increased.
NASA Astrophysics Data System (ADS)
Okano, Daisuke
1998-11-01
Guided Discharge Path by Weak Ionized Region between Two Plasmas Produced by YAG Laser in Atmospheric Air Gap with Non-Uniform DC Electric Field*, Daisuke Okano, Kyushu Tokai University, 9-1-1 Toroku, Kumamoto, Japan. -----We have studied on guiding discharge path by weak ionized region between plasmas produced by a visible laser, that is, a YAG laser with wavelength 532nm, in an atmospheric air gap with DC non-uniform electric field using a rod-to-plate electrode. We succeeded in capturing the framing images in the temporal evolution on guiding discharge along the YAG laser light path. From the results of experiments, the region between two plasmas produced by a YAG laser can guide a discharge path, and the region between two plasmas on the laser light path is considered as well as a weak ionized one [1] produced by an excimer laser. [1]J.Sasaki, S.Kubodera, R.Ozaki and T.Uchiyama, J. Appl. Phys., 60 (1986) 3845. *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.
Clark, P.E.; Zhu, Q.
1994-12-31
Recently, the flow of fluids into a fracture from a point source has been the subject of several different papers. Cleary and Fonseca first suggested that convective transport should play a major role in the placement of proppant when the flow into a fracture was from a point source. Clark and Courington presented data showing that for non-viscosified fluids convection was the dominant mechanism of transport. However, they showed, that for uniform fractures, viscosifying the fluid made a large difference in the transport mechanism. In a later paper, Clark and Zhu presented data for nonuniform fractures and viscosified fluids weighted with either salt or silica flour that showed that the presence of minor non-uniformities serve to negate the effect of convection even more than viscosifying the fluids. In this work, the authors have extended the work presented in the previous two papers to high viscosity Newtonian fluids and crosslinked fluids. The experiments have all been done with various concentrations of silica flour to simulate added proppant. Both changing the nature of the non-uniformities and crosslinking the polymer solution have a profound affect on the flow into the fracture and the convective process.
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... REGULATIONS TRANSFERRED FROM THE OFFICE OF THRIFT SUPERVISION Capital § 390.467 Leverage ratio. (a) The... defined in this subpart, shall consist of a ratio of core capital to adjusted total assets of 3...
12 CFR 390.467 - Leverage ratio.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 12 Banks and Banking 5 2012-01-01 2012-01-01 false Leverage ratio. 390.467 Section 390.467 Banks... REGULATIONS TRANSFERRED FROM THE OFFICE OF THRIFT SUPERVISION Capital § 390.467 Leverage ratio. (a) The... defined in this subpart, shall consist of a ratio of core capital to adjusted total assets of 3...
12 CFR 390.467 - Leverage ratio.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 12 Banks and Banking 5 2013-01-01 2013-01-01 false Leverage ratio. 390.467 Section 390.467 Banks... REGULATIONS TRANSFERRED FROM THE OFFICE OF THRIFT SUPERVISION Capital § 390.467 Leverage ratio. (a) The... defined in this subpart, shall consist of a ratio of core capital to adjusted total assets of 3...
17 CFR 31.8 - Cover of leverage contracts.
Code of Federal Regulations, 2011 CFR
2011-04-01
... contracts entered into with leverage customers, and must at all times also maintain cover of at least 90... leverage customers. At least 25 percent of the amount of physical commodities subject to open long leverage... entered into with leverage customers: And, provided further, That the leverage transaction...
17 CFR 31.15 - Reporting to leverage customers.
Code of Federal Regulations, 2012 CFR
2012-04-01
..., liquidation, rescission or delivery of a leverage contract, a statement showing the financial result of the... 17 Commodity and Securities Exchanges 1 2012-04-01 2012-04-01 false Reporting to leverage... LEVERAGE TRANSACTIONS § 31.15 Reporting to leverage customers. Each leverage transaction merchant...
7 CFR 4290.1120 - General eligibility requirements for Leverage.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 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 Leverage... 7 Agriculture 15 2013-01-01 2013-01-01 false General eligibility requirements for Leverage....
7 CFR 4290.1120 - General eligibility requirements for Leverage.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 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 Leverage... 7 Agriculture 15 2014-01-01 2014-01-01 false General eligibility requirements for Leverage....
7 CFR 4290.1120 - General eligibility requirements for Leverage.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 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 Leverage... 7 Agriculture 15 2010-01-01 2010-01-01 false General eligibility requirements for Leverage....
7 CFR 4290.1120 - General eligibility requirements for Leverage.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 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 Leverage... 7 Agriculture 15 2011-01-01 2011-01-01 false General eligibility requirements for Leverage....
17 CFR 31.15 - Reporting to leverage customers.
Code of Federal Regulations, 2014 CFR
2014-04-01
..., liquidation, rescission or delivery of a leverage contract, a statement showing the financial result of the... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Reporting to leverage... LEVERAGE TRANSACTIONS § 31.15 Reporting to leverage customers. Each leverage transaction merchant...
17 CFR 31.15 - Reporting to leverage customers.
Code of Federal Regulations, 2013 CFR
2013-04-01
..., liquidation, rescission or delivery of a leverage contract, a statement showing the financial result of the... 17 Commodity and Securities Exchanges 1 2013-04-01 2013-04-01 false Reporting to leverage... LEVERAGE TRANSACTIONS § 31.15 Reporting to leverage customers. Each leverage transaction merchant...
7 CFR 4290.1120 - General eligibility requirements for Leverage.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 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 Leverage... 7 Agriculture 15 2012-01-01 2012-01-01 false General eligibility requirements for Leverage....
17 CFR 31.15 - Reporting to leverage customers.
Code of Federal Regulations, 2011 CFR
2011-04-01
..., liquidation, rescission or delivery of a leverage contract, a statement showing the financial result of the... 17 Commodity and Securities Exchanges 1 2011-04-01 2011-04-01 false Reporting to leverage... LEVERAGE TRANSACTIONS § 31.15 Reporting to leverage customers. Each leverage transaction merchant...
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.
NASA Astrophysics Data System (ADS)
Moulton, D. E.; Lega, J.
2009-11-01
We analyze and classify equilibrium solutions of the one-dimensional thin film equation with no-flux boundary conditions and in the presence of a spatially dependent external forcing. We prove theorems that shed light on the nature of these equilibrium solutions, guarantee their validity, and describe how they depend on the properties of the external forcing. We then apply these results to the reverse draining of a one-dimensional magnetic soap film subject to an external non-uniform magnetic field. Numerical simulations illustrate the convergence of the solutions towards equilibrium configurations. We then present bifurcation diagrams for steady state solutions. We find that multiple stable equilibrium solutions exist for fixed parameters, and uncover a rich bifurcation structure to these solutions, demonstrating the complexity hidden in a relatively simple looking evolution equation. Finally, we provide a simulation describing how numerical solutions traverse the bifurcation diagram, as the amplitude of the forcing is slowly increased and then decreased.
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
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.
NASA Astrophysics Data System (ADS)
Boyko, Evgeniy; Bercovici, Moran; Gat, Amir
2016-11-01
We analyze flow of a non-Newtonian fluid in a Hele-Shaw cell, subjected to spatially non-uniform electroosmotic flow. We specifically focus on power-law fluids with wall depletion properties and derive a p-Poisson equation governing the pressure field, as well as a set of linearized equations representing its asymptotic approximation for weakly non-Newtonian behavior. To investigate the effect of non-Newtonian properties on the resulting fluidic pressure and velocity, we consider several configurations in one and two dimensions, and calculate both exact and approximate solutions. We show that the asymptotic approximation is in good agreement with exact solutions even for fluids with significant non-Newtonian behavior. The asymptotic model thus enables prediction of the flow and pressure fields for non-Newtonian fluids, and may be particularly useful for the analysis and design of microfluidic systems involving electro-kinetic transport of such fluids.
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)
André, Frédéric
2017-03-01
The recently proposed ℓ-distribution/ICE (Iterative Copula Evaluation) method of gas radiation suffers from symmetry issues when applied in highly non-isothermal and non-homogeneous gaseous media. This problem is studied in a detailed theoretical way. The objective of the present paper is: 1/to provide a mathematical analysis of this problem of symmetry and, 2/to suggest a decisive factor, defined in terms of the ratio between the narrow band Planck and Rosseland mean absorption coefficients, to handle this issue. Comparisons of model predictions with reference LBL calculations show that the proposed criterion improves the accuracy of the intuitive ICE method for applications in highly non-uniform gases at high temperatures.
Ogée, J; Cuntz, M; Peylin, P; Bariac, T
2007-04-01
This study focuses on the spatial patterns of transpiration-driven water isotope enrichment (Delta(lw)) along monocot leaves. It has been suggested that these spatial patterns are the result of competing effects of advection and (back-)diffusion of water isotopes along leaf veins and in the mesophyll, but also reflect leaf geometry (e.g. leaf length, interveinal distance) and non-uniform gas-exchange parameters. We therefore developed a two-dimensional model of isotopic leaf water enrichment that incorporates new features, compared with previous models, such as radial diffusion in the xylem, longitudinal diffusion in the mesophyll, non-uniform gas-exchange parameters and non-steady-state effects. The model reproduces well all published measurements of Delta(lw) along monocot leaf blades, except at the leaf tip and given the uncertainties on measurements and model parameters. We show that the longitudinal diffusion in the mesophyll cannot explain the observed reduction in the isotope gradient at the leaf tip. Our results also suggest that the observed differences in Delta(lw) between C(3) and C(4) plants reflect more differences in mesophyll tortuosity rather than in leaf length or interveinal distance. Mesophyll tortuosity is by far the most sensitive parameter and different values are required for different experiments on the same plant species. Finally, using new measurements of non-steady-state, spatially varying leaf water enrichment we show that spatial patterns are in steady state around midday only, just as observed for bulk leaf water enrichment, but can be easily upscaled to the whole leaf level, regardless of their degree of heterogeneity along the leaf.
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.
IPP leveraged financing: Unfair advantage
Naill, R.F.; Dudley, W.C. )
1992-01-15
IPPs normally employ project financing - in which the loans for a project are secured primarily by the assets of the project (and not by the assets of the parent or owner of the project). To support project financing, the IPP developer puts together a package that includes a site, a signed electric contract, a steam contract (if the plant is to be a qualifying facility (QF) under PURPA), a construction contract, and all the necessary environmental permits. The developer then usually attempts to borrow as much of the project's capital costs as possible - ergo the term highly leveraged financing. This is because debt is cheaper than equity (equity is a riskier investment and requires a return significantly higher than debt), and cheaper still when is preferential tax treatment is considered. For this reason, equity is typically used by IPPs only to take risks that lenders are unwilling to assume, and to assure lenders that the developer will not walk away if a project becomes, less profitable. In contrast, a utility finances construction - and all its other capital requirements - by issuing debt or selling equity from the parent company. Its capital needs are typically financed by issuing equity and debt, secured by the assets on the balance sheet, in roughly a 50:50 ratio. The cost of debt depends on the utility's bond rating - with the more risky utilities rated lower and, therefore, paying more for debt. If borrowing new capital would cause the utility to exceed its allowed debt-to-equity ratio, the utility will have to sell equity to raise part of its capital requirements. In the case of utility financing, the debt is secured by all the utility's assets - not just those of the particular construction project needing the investment.
ERIC Educational Resources Information Center
Aviation/Space, 1980
1980-01-01
The resources listed different types of materials related to the aerospace science under specified categories: free materials and inexpensive, selected government publication, audiovisual (government, nongovernment), aviation books, and space books. The list includes the publisher's name and the price for each publication. (SK)
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.
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…
13 CFR 108.1120 - General eligibility requirement for Leverage.
Code of Federal Regulations, 2012 CFR
2012-01-01
... for Leverage. 108.1120 Section 108.1120 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION NEW MARKETS VENTURE CAPITAL (âNMVCâ) PROGRAM SBA Financial Assistance for NMVC Companies (Leverage) General Information About Obtaining Leverage § 108.1120 General eligibility requirement for Leverage....
13 CFR 108.1120 - General eligibility requirement for Leverage.
Code of Federal Regulations, 2014 CFR
2014-01-01
... for Leverage. 108.1120 Section 108.1120 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION NEW MARKETS VENTURE CAPITAL (âNMVCâ) PROGRAM SBA Financial Assistance for NMVC Companies (Leverage) General Information About Obtaining Leverage § 108.1120 General eligibility requirement for Leverage....
13 CFR 108.1120 - General eligibility requirement for Leverage.
Code of Federal Regulations, 2013 CFR
2013-01-01
... for Leverage. 108.1120 Section 108.1120 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION NEW MARKETS VENTURE CAPITAL (âNMVCâ) PROGRAM SBA Financial Assistance for NMVC Companies (Leverage) General Information About Obtaining Leverage § 108.1120 General eligibility requirement for Leverage....
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,...
Saxena, Saurabh; Stanek, Jan; Cevec, Mirko; Plavec, Janez; Koźmiński, Wiktor
2014-11-01
A through bond, C4'/H4' selective, "out and stay" type 4D HC(P)CH experiment is introduced which provides sequential connectivity via H4'(i)-C4'(i)-C4'(i-1)-H4'(i-1) correlations. The (31)P dimension (used in the conventional 3D HCP experiment) is replaced with evolution of better dispersed C4' dimension. The experiment fully utilizes (13)C-labeling of RNA by inclusion of two C4' evolution periods. An additional evolution of H4' is included to further enhance peak resolution. Band selective (13)C inversion pulses are used to achieve selectivity and prevent signal dephasing due to the of C4'-C3' and C4'-C5' homonuclear couplings. For reasonable resolution, non-uniform sampling is employed in all indirect dimensions. To reduce sensitivity losses, multiple quantum coherences are preserved during shared-time evolution and coherence transfer delays. In the experiment the intra-nucleotide peaks are suppressed whereas inter-nucleotide peaks are enhanced to reduce the ambiguities. The performance of the experiment is verified on a fully (13)C, (15)N-labeled 34-nt hairpin RNA comprising typical structure elements.
NASA Astrophysics Data System (ADS)
Lee, A. K. Y.; Willis, M. D.; Healy, R. M.; Wang, J. M.; Jeong, C.-H.; Wenger, J. C.; Evans, G. J.; Abbatt, J. P. D.
2015-11-01
Biomass burning is a major source of black carbon (BC) and primary organic aerosol globally. In particular, biomass burning organic aerosol (BBOA) is strongly associated with atmospheric brown carbon (BrC) that absorbs near ultraviolet and visible light, resulting in significant impacts on regional visibility degradation and radiative forcing. The mixing state of BBOA can play a critical role in the prediction of aerosol optical properties. In this work, single particle measurements from a soot-particle aerosol mass spectrometer coupled with a light scattering module (LS-SP-AMS) were performed to examine the mixing state of BBOA, refractory black carbon (rBC) and potassium (K+, a tracer for biomass burning aerosol) in an air mass influenced by aged biomass burning. Cluster analysis of single particle measurements identified five BBOA-related particle types. rBC accounted for 3-14 w.t. % of these particle types on average. Only one particle type exhibited a strong ion signal for K+, with mass spectra characterized by low molecular weight organic species. The remaining four particle types were classified based on the apparent molecular weight of the BBOA constituents. Two particle types were associated with low potassium content and significant amounts of high molecular weight (HMW) organic compounds. Our observations indicate non-uniform mixing of particles within a biomass burning plume in terms of molecular weight and illustrate that HMW BBOA can be a key contributor to low-volatility BrC observed in BBOA particles.
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)
In Kim, Jong; Jeong, Chan-Yong; Kwon, Hyuck-In; Jung, Keum Dong; Park, Mun Soo; Kim, Ki Hwan; Seo, Mi Seon; Lee, Jong-Ho
2017-03-01
We propose a new local degradation model based on a non-uniform increase in donor-like traps (DLTs) determined by distributions of an electric field and measured device temperature in amorphous In–Ga–Zn–O (a-IGZO) thin film transistors (TFTs). A systematic investigation of the degradation model reveals that vertical field-dependent DLTs are essential for modeling of measured asymmetric electrical characteristics between the source and drain after positive gate and drain bias stressing. An increased temperature due to self-heating is found to play a role in intensifying the asymmetric degradation. From the individual simulation of measured transfer curves at different stress times, the model parameters and an asymmetry index as a function of stress time are extracted. It is expected that this novel methodology will provide new insight into asymmetric degradation and be utilized to predict the influence of electric field and heat on degradation under various bias-stress conditions in a-IGZO TFTs.
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.
NASA Astrophysics Data System (ADS)
Lehujeur, Maximilien; Vergne, Jérôme; Maggi, Alessia; Schmittbuhl, Jean
2017-01-01
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 modelling 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.
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.
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.
Leveraging Human Assets in Law Firms: Human Capital Structures and Organizational Capabilities.
ERIC Educational Resources Information Center
Sherer, Peter D.
1995-01-01
Using the ratio of associates to partners as a measure of human asset leveraging, analysis of data from 312 law firms reveals that the ratio is related to business strategy, human resource management practices, organizational structure, and the competitiveness of the firm. (SK)
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
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
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 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…
Leveraging Resources for Student Success: How School Leaders Build Equity.
ERIC Educational Resources Information Center
Burke, Mary Ann; Baca, Reynaldo; Picus, Lawrence O.; Jones, Cathy E.
As schools become more culturally diverse, it is critical for principals and teachers to enact policies and procedures that ensure effective interactions among students and their teachers. This guide offers ways to ensure equitable access to quality education for all students, regardless of socioeconomic status or cultural heritage. Its intent is…
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 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…
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…
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…
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…
Leveraging Industry Relationships in the Academic Enterprise
ERIC Educational Resources Information Center
Blackney, Kenneth S.; Papadakis, Constantine N.
2004-01-01
Drexel University has maintained a leadership role in academic technology by choosing technology initiatives wisely, timing them effectively and ensuring that they have the greatest value to the community at large while being affordable. Drexel has leveraged vendor relationships to help accomplish these initiatives, and has shared its expertise…
2017-01-01
B-spline functions are widely used in many industrial applications such as computer graphic representations, computer aided design, computer aided manufacturing, computer numerical control, etc. Recently, there exist some demands, e.g. in reverse engineering (RE) area, to employ B-spline curves for non-trivial cases that include curves with discontinuous points, cusps or turning points from the sampled data. The most challenging task in these cases is in the identification of the number of knots and their respective locations in non-uniform space in the most efficient computational cost. This paper presents a new strategy for fitting any forms of curve by B-spline functions via local algorithm. A new two-step method for fast knot calculation is proposed. In the first step, the data is split using a bisecting method with predetermined allowable error to obtain coarse knots. Secondly, the knots are optimized, for both locations and continuity levels, by employing a non-linear least squares technique. The B-spline function is, therefore, obtained by solving the ordinary least squares problem. The performance of the proposed method is validated by using various numerical experimental data, with and without simulated noise, which were generated by a B-spline function and deterministic parametric functions. This paper also discusses the benchmarking of the proposed method to the existing methods in literature. The proposed method is shown to be able to reconstruct B-spline functions from sampled data within acceptable tolerance. It is also shown that, the proposed method can be applied for fitting any types of curves ranging from smooth ones to discontinuous ones. In addition, the method does not require excessive computational cost, which allows it to be used in automatic reverse engineering applications. PMID:28319131
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.
1984-01-01
AI and AII cat retinal amacrine cells have highly varicose non-uniform, neuritic processes. Processes of both types were reconstructed via a computer system using serial electron micrographs. These reconstructions were analyzed for (a) varicosity volume, surface area, and length, (b) "neck" volume, surface area, and length, (c) number of microtubules within the varicosity, (d) number of microtubules within the "neck," and (e) volume and surface area of mitochondria and smooth endoplasmic reticulum and large smooth vesicular bodies within the processes. Correlation of these parameters revealed a linear relationship between the number of microtubules in the necks and mean neck cross-sectional area (rs = 0.780, P less than 0.001), while microtubule number within the varicosities showed no correlation with varicosity volume (rs = 0.239, P greater than 0.2). Varicosity volume did, however, correlate strongly with the summed volume of mitochondria and smooth vesicular bodies contained within the varicosity for both cell types examined. The ratio between membranous organelle volume and varicosity volume for AI amacrine processes of 1:6.97 (rs = 0.927), differed from the ratio of 1:1.80 for the AII amacrine processes (rs = 0.987). Similar relationships were observed in other nonvaricose neurites such as optic tract axons. Membranous organelles appear to contribute an additional obligatory volume to the cytosol that can be as much as seven times the organelles' direct volume. These observations suggest that both the cytoskeletal components, and the membrane organelles play a direct role in determining neurite shape. PMID:6538879
NASA Astrophysics Data System (ADS)
Yair, Aaron; Arbel, Youval
2015-04-01
A Tamarix aphylla forest was planted on arid sand dunes in the northern Negev, where average annual rainfall is 150 mm. Field observations, 40 years after planting, revealed a non-uniform spatial survival and development of planted trees. Trees planted over the crest of the dunes are well developed with large canopies and a high survival rate, whereas trees planted in the interdune flat corridors are small, thin and scattered. A thick litter layer, underlain by a sandy repellent layer, developed below the large trees. The water repellent layer is absent in the area of the small trees. The study focused on the role of the water repellent layer on the water regime over the steep and the low angle dunes. Water repellency was determined by the Water Penetration Time Method. The monitoring of rainfall-runoff relationships was based on runoff plots established in both areas. Samples for soil water content were taken following rain events. Data obtained show a striking difference between the steep and long dunes in all aspects studied. Results obtained show that two opposite feedback mechanisms occurred after tree plantation. The large trees shed a substantial amount of leaves, whose decay developed a water repellent layer. Runoff generation enhanced deep water penetration, through the phenomenon of finger flow. At the same time, due to the lack of a water repellent layer, runoff did not develop in the interdune area; eliminating the positive effect of water concentration. In addition, the soil in the interdune areas is richer in fine grained particle than the active dune crests, limiting thus the depth of water penetration and water availability for planted trees.
NASA Astrophysics Data System (ADS)
Melnikov, Alexey; Razdolski, Ilya; Alekhin, Alexandr; Ilin, Nikita; Meyburg, Jan; Diesing, Detlef; Roddatis, Vladimir; Rungger, Ivan; Stamenova, Maria; Sanvito, Stefano; Bovensiepen, Uwe
2016-10-01
Further development of spintronics requires miniaturization and reduction of characteristic timescales of spin dynamics combining the nanometer spatial and femtosecond temporal ranges. These demands shift the focus of interest towards the fundamental open question of the interaction of femtosecond spin current (SC) pulses with a ferromagnet (FM). The spatio-temporal properties of the spin transfer torque (STT) exerted by ultrashort SC pulses on the FM open the time domain for studying STT fingerprint on spatially non-uniform magnetization dynamics. Using the sensitivity of magneto-induced second harmonic generation to SC, we develop technique for SC monitoring. With 20 fs resolution, we demonstrate the generation of 250 fs-long SC pulses in Fe/Au/Fe/MgO(001) structures. Their temporal profile indicates (i) nearly-ballistic hot electron transport in Au and (ii) that the pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Together with strongly spin-dependent Fe/Au interface transmission calculated for these carriers, this suggests the non-thermal spin-dependent Seebeck effect dominating the generation of ultrashort SC pulses. The analysis of SC transmission/reflection at the Au/Fe interface shows that hot electron spins orthogonal to the Fe magnetization rotate gaining huge parallel (anti-parallel) projection in transmitted (reflected) SC. This is accompanied by a STT-induced perturbation of the magnetization localized at the interface, which excites the inhomogeneous high-frequency spin dynamics in the FM. Time-resolved magneto-optical studies reveal the excitation of several standing spin wave modes in the Fe film with their spectrum extending up to 0.6 THz and indicating the STT spatial confinement to 2 nm.
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)
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.
Marble, J. C.; DiFilippo, E. L.; Zhang, Z.; Tick, G. R.; Brusseau, M. L.
2010-01-01
The use of a lumped-process mathematical model to simulate the complete dissolution of immiscible liquid non-uniformly distributed in physically heterogeneous porous-media systems was investigated. The study focused specifically on systems wherein immiscible liquid was poorly accessible to flowing water. Two representative, idealized scenarios were examined, one wherein immiscible liquid at residual saturation exists within a lower-permeability unit residing in a higher-permeability matrix, and one wherein immiscible liquid at higher saturation (a pool) exists within a higher-permeability unit adjacent to a lower-permeability unit. As expected, effluent concentrations were significantly less than aqueous solubility due to dilution and by-pass flow effects. The measured data were simulated with two mathematical models, one based on a simple description of the system and one based on a more complex description. The permeability field and the distribution of the immiscible-liquid zones were represented explicitly in the more complex, distributed-process model. The dissolution rate coefficient in this case represents only the impact of local-scale (and smaller) processes on dissolution, and the parameter values were accordingly obtained from the results of experiments conducted with one-dimensional, homogeneously-packed columns. In contrast, the system was conceptualized as a pseudo-homogeneous medium with immiscible liquid uniformly distributed throughout the system for the simpler, lumped-process model. With this approach, all factors that influence immiscible-liquid dissolution are incorporated into the calibrated dissolution rate coefficient, which in such cases serves as a composite or lumped term. The calibrated dissolution rate coefficients obtained from the simulations conducted with the lumped-process model were approximately two to three orders of magnitude smaller than the independently-determined values used for the simulations conducted with the
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.
Dung, Van Than; Tjahjowidodo, Tegoeh
2017-01-01
B-spline functions are widely used in many industrial applications such as computer graphic representations, computer aided design, computer aided manufacturing, computer numerical control, etc. Recently, there exist some demands, e.g. in reverse engineering (RE) area, to employ B-spline curves for non-trivial cases that include curves with discontinuous points, cusps or turning points from the sampled data. The most challenging task in these cases is in the identification of the number of knots and their respective locations in non-uniform space in the most efficient computational cost. This paper presents a new strategy for fitting any forms of curve by B-spline functions via local algorithm. A new two-step method for fast knot calculation is proposed. In the first step, the data is split using a bisecting method with predetermined allowable error to obtain coarse knots. Secondly, the knots are optimized, for both locations and continuity levels, by employing a non-linear least squares technique. The B-spline function is, therefore, obtained by solving the ordinary least squares problem. The performance of the proposed method is validated by using various numerical experimental data, with and without simulated noise, which were generated by a B-spline function and deterministic parametric functions. This paper also discusses the benchmarking of the proposed method to the existing methods in literature. The proposed method is shown to be able to reconstruct B-spline functions from sampled data within acceptable tolerance. It is also shown that, the proposed method can be applied for fitting any types of curves ranging from smooth ones to discontinuous ones. In addition, the method does not require excessive computational cost, which allows it to be used in automatic reverse engineering applications.
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)
Takahashi, Tsutomu; Sato, Haruo; Nishimura, Takeshi
2008-05-01
Direct waves of microearthquakes in the high-frequency range (>1 Hz) strongly reflect the random inhomogeneities near their ray paths. This study conducts numerical simulations of envelope broadening of impulsively radiated wavelet assuming spatially non-uniform distribution of random inhomogeneities. We assume plural von Kármán type power spectral density functions (PSDF) for random inhomogeneity to clarify how the non-uniformly distributed random media affect the frequency dependence of envelope broadening. We employ the stochastic ray path method based on the Markov approximation for the mutual coherence function. This method is appropriate to simulate multiple forward scattering during the wave propagation. We mainly examine the travel distance and frequency dependence of the peak delay time in relation to the parameters characterizing the PSDFs. The peak delay time, which is defined as the time lag from the direct-wave onset to the maximum amplitude arrival of its envelope, is the best parameter reflecting the accumulated scattering effect in random media and is quite insensitive to the intrinsic attenuation. According to the numerical simulations in various non-uniform random media, we find some remarkable features in travel distance and frequency dependence, which cannot be found in uniform random media. For example, the frequency dependence in uniform random media is uniquely determined by the spectral gradient of PSDF for arbitrary travel distance; however, that in non-uniform media gradually changes as travel distance increases if the waves have experienced a change of spectral gradient in PSDF. Considering the results of our simulation, we propose a simple recursive formula to calculate the peak delay time in non-uniform random media. This recursive formula can predict the simulation results appropriately and relate the peak delay times to two parameters quantifying the von Kármán type PSDF in short wavelengths. It will become a mathematical base for
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
NASA Astrophysics Data System (ADS)
Shevtsov, S.; Zhilyaev, I.; Oganesyan, P.; Axenov, V.
2017-01-01
The glass/carbon fiber composites are widely used in the design of various aircraft and rotorcraft components such as fairings and cowlings, which have predominantly a shell-like geometry and are made of quasi-isotropic laminates. The main requirements to such the composite parts are the specified mechanical stiffness to withstand the non-uniform air pressure at the different flight conditions and reduce a level of noise caused by the airflow-induced vibrations at the constrained weight of the part. The main objective of present study is the optimization of wall thickness and lay-up of composite shell-like cowling. The present approach assumes conversion of the CAD model of the cowling surface to finite element (FE) representation, then its wind tunnel testing simulation at the different orientation of airflow to find the most stressed mode of flight. Numerical solutions of the Reynolds averaged Navier-Stokes (RANS) equations supplemented by k-w turbulence model provide the spatial distributions of air pressure applied to the shell surface. At the formulation of optimization problem the global strain energy calculated within the optimized shell was assumed as the objective. A wall thickness of the shell had to change over its surface to minimize the objective at the constrained weight. We used a parameterization of the problem that assumes an initiation of auxiliary sphere with varied radius and coordinates of the center, which were the design variables. Curve that formed by the intersection of the shell with sphere defined boundary of area, which should be reinforced by local thickening the shell wall. To eliminate a local stress concentration this increment was defined as the smooth function defined on the shell surface. As a result of structural optimization we obtained the thickness of shell's wall distribution, which then was used to design the draping and lay-up of composite prepreg layers. The global strain energy in the optimized cowling was reduced in2
17 CFR 31.8 - Cover of leverage contracts.
Code of Federal Regulations, 2012 CFR
2012-04-01
... current market value of the commodity represented by each receipt. (ii) Warehouse receipts for gold 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,...
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, 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, 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...
13 CFR 107.1120 - General eligibility requirements for Leverage.
Code of Federal Regulations, 2013 CFR
2013-01-01
... for Leverage. 107.1120 Section 107.1120 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION SMALL BUSINESS INVESTMENT COMPANIES SBA Financial Assistance for Licensees (Leverage) General... profitability and financial viability as SBA deems appropriate. (d) For any Leverage draw that would cause...
12 CFR 325.3 - Minimum leverage capital requirement.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 12 Banks and Banking 4 2011-01-01 2011-01-01 false Minimum leverage capital requirement. 325.3... GENERAL POLICY CAPITAL MAINTENANCE Minimum Capital Requirements § 325.3 Minimum leverage capital requirement. (a) General. Banks must maintain at least the minimum leverage capital requirement set forth...
13 CFR 107.1120 - General eligibility requirements for Leverage.
Code of Federal Regulations, 2011 CFR
2011-01-01
... for Leverage. 107.1120 Section 107.1120 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION SMALL BUSINESS INVESTMENT COMPANIES SBA Financial Assistance for Licensees (Leverage) General... profitability and financial viability as SBA deems appropriate. (d) For any Leverage draw that would cause...
13 CFR 107.1120 - General eligibility requirements for Leverage.
Code of Federal Regulations, 2014 CFR
2014-01-01
... for Leverage. 107.1120 Section 107.1120 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION SMALL BUSINESS INVESTMENT COMPANIES SBA Financial Assistance for Licensees (Leverage) General... profitability and financial viability as SBA deems appropriate. (d) For any Leverage draw that would cause...
45 CFR 96.87 - Leveraging incentive program.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 97-35 (42 U.S.C. 8626a). (2)(i) The only entities eligible to receive leveraging incentive funds from... period for which leveraging incentive funds are sought; and tribes and tribal organizations described in... under section 2602(b) in the award period, will receive leveraging incentive funds allocable to them...
17 CFR 31.17 - Records of leverage transactions.
Code of Federal Regulations, 2012 CFR
2012-04-01
... receiving a leverage customer's order shall immediately upon receipt thereof prepare a written record of... leverage transaction merchant executing the order of a leverage customer shall record on a written record... section, the term “order” shall include, but not be limited to, any order for the purchase,...
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
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.
Leverage technology to improve your revenue cycle.
Larch, Sara M
2012-01-01
Evaluating technology and implementing it effectively can produce major results to your bottom line. These technologies increase automation, which reduces errors and thus increases the clean claim percentage. New technology can enable the medical practice to reduce staff costs through increased productivity. Adding technology can offer medical practices new ways to run their business. Continue to learn about new technologies and the vendors and companies that offer them. Leverage technology in ways to get more money to the bottom line!
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…
NASA Astrophysics Data System (ADS)
Rastegar, Vahid
Nanoscale finishing and planarization are integral process steps in multilevel metallization designs for integrated circuit (IC) manufacturing since it is necessary to ensure local and global surface planarization at each metal layer before depositing the next layer. Chemical mechanical planarization (CMP) has been widely recognized as the most promising technology to eliminate topographic variation and has allowed the construction of multilevel interconnection structures with a more regularly stacked sequence, resulting in better device performance [1]. Understanding fundamental of the CMP mechanisms can offer guidance to the control and optimization of the polishing processes. CMP kinematics based on slurry distribution and particle trajectories have a significant impact on MRR profiles. In this work a mathematical model to describe particle trajectories during chemical mechanical polishing was developed and extended to account for the effect of larger particles, particle location changes due to slurry dispensing and in-situ conditioning. Material removal rate (MRR) and within wafer non-uniformity (WIWNU) were determined based on the calculated particle trajectory densities. Rotary dynamics and reciprocating motion were optimized to obtain best MRR uniformity. Edge-fast MRR profile was discussed based on mechanical aspect of CMP. Using the model, we also investigated the effect of variable rotational speeds of wafer and pad, and of large particles on WIWNU and scratch growth. It was shown that the presence of even a small portion of large particles can deteriorate the WIWNU significantly and also lead to more scratches. Furthermore, it was shown that the in-situ conditioning improves the uniformity of the polished wafers. Furthermore, a combined experimental and computational study of fibrous filters for removal of larger abrasive particles from aqueous dispersions, essential to minimize defects during chemical mechanical polishing, was performed. Dilute aqueous
Identification of high leverage points in binary logistic regression
NASA Astrophysics Data System (ADS)
Fitrianto, Anwar; Wendy, Tham
2016-10-01
Leverage points are those which measures uncommon observations in x space of regression diagnostics. Detection of high leverage points plays a vital role because it is responsible in masking outlier. In regression, high observations which made at extreme in the space of explanatory variables and they are far apart from the average of the data are called as leverage points. In this project, a method for identification of high leverage point in logistic regression was shown using numerical example. We investigate the effects of high leverage point in the logistic regression model. The comparison of the result in the model with and without leverage model is being discussed. Some graphical analyses based on the result of the analysis are presented. We found that the presence of HLP have effect on the hii, estimated probability, estimated coefficients, p-value of variable, odds ratio and regression equation.
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.
Contract leveraging: a strategy for provider groups in managed care.
Mayer, G G; Kuklierus, A
1998-09-01
Using one's leverage in health care negotiation does not mean intimidating, threatening, or even demanding a certain percentage of the premium. Leveraging is not a game of who wins and who loses; rather, it is a negotiation technique. The authors explain how to best use the abilities and proficiencies of a provider group to negotiate contracts with MCOs.
17 CFR 31.6 - Registration of leverage commodities.
Code of Federal Regulations, 2010 CFR
2010-04-01
... regulations thereunder, or that it is necessary or appropriate to ensure the financial solvency of leverage... would be necessary or appropriate to ensure the financial solvency of leverage transactions or prevent... 17 Commodity and Securities Exchanges 1 2010-04-01 2010-04-01 false Registration of...
17 CFR 31.6 - Registration of leverage commodities.
Code of Federal Regulations, 2013 CFR
2013-04-01
... regulations thereunder, or that it is necessary or appropriate to ensure the financial solvency of leverage... would be necessary or appropriate to ensure the financial solvency of leverage transactions or prevent... 17 Commodity and Securities Exchanges 1 2013-04-01 2013-04-01 false Registration of...
17 CFR 31.6 - Registration of leverage commodities.
Code of Federal Regulations, 2014 CFR
2014-04-01
... regulations thereunder, or that it is necessary or appropriate to ensure the financial solvency of leverage... would be necessary or appropriate to ensure the financial solvency of leverage transactions or prevent... 17 Commodity and Securities Exchanges 1 2014-04-01 2014-04-01 false Registration of...
78 FR 17766 - Interagency Guidance on Leveraged Lending
Federal Register 2010, 2011, 2012, 2013, 2014
2013-03-22
... leveraged loan origination business. Therefore, the final guidance addresses mainly the latter type of... elected to adopt a definition of leveraged lending that encompasses all business lines, the agencies do... consistent application across all business lines and that are appropriate to the institution. Therefore,...
17 CFR 31.8 - Cover of leverage contracts.
Code of Federal Regulations, 2010 CFR
2010-04-01
.... 31.8 Section 31.8 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION LEVERAGE... this section. (2) Permissible cover for a long leverage contract is limited to: (i) Warehouse receipts... and accrued interest on any loan against such warehouse receipts does not exceed 70 percent of...
Leveraging Emerging Technology to Maintain Corporate Situational Awareness
2008-06-01
Abstract and Outline for 13th ICCRTS For the paper entitled: Leveraging Emerging Technology to Maintain Corporate...AND SUBTITLE Leveraging Emerging Technology to Maintain Corporate Situational Awareness 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...public release; distribution unlimited 13. SUPPLEMENTARY NOTES 13th International Command and Control Research and Technology Symposia (ICCRTS 2008
12 CFR 325.3 - Minimum leverage capital requirement.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 12 Banks and Banking 4 2010-01-01 2010-01-01 false Minimum leverage capital requirement. 325.3 Section 325.3 Banks and Banking FEDERAL DEPOSIT INSURANCE CORPORATION REGULATIONS AND STATEMENTS OF... requirement. (a) General. Banks must maintain at least the minimum leverage capital requirement set forth...
13 CFR 107.1120 - General eligibility requirements for Leverage.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false General eligibility requirements for Leverage. 107.1120 Section 107.1120 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION SMALL BUSINESS INVESTMENT COMPANIES SBA Financial Assistance for Licensees (Leverage)...
13 CFR 107.1100 - Types of Leverage and application procedures.
Code of Federal Regulations, 2010 CFR
2010-01-01
... BUSINESS INVESTMENT COMPANIES SBA Financial Assistance for Licensees (Leverage) General Information About Obtaining Leverage § 107.1100 Types of Leverage and application procedures. (a) Types of Leverageable... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Types of Leverage and...
7 CFR 4290.1100 - Type of Leverage and application procedures.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 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 available... 7 Agriculture 15 2012-01-01 2012-01-01 false Type of Leverage and application procedures....
13 CFR 107.1100 - Types of Leverage and application procedures.
Code of Federal Regulations, 2014 CFR
2014-01-01
... BUSINESS INVESTMENT COMPANIES SBA Financial Assistance for Licensees (Leverage) General Information About Obtaining Leverage § 107.1100 Types of Leverage and application procedures. (a) Types of Leverageable... 13 Business Credit and Assistance 1 2014-01-01 2014-01-01 false Types of Leverage and...
13 CFR 107.1100 - Types of Leverage and application procedures.
Code of Federal Regulations, 2011 CFR
2011-01-01
... BUSINESS INVESTMENT COMPANIES SBA Financial Assistance for Licensees (Leverage) General Information About Obtaining Leverage § 107.1100 Types of Leverage and application procedures. (a) Types of Leverageable... 13 Business Credit and Assistance 1 2011-01-01 2011-01-01 false Types of Leverage and...
7 CFR 4290.1100 - Type of Leverage and application procedures.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 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 available... 7 Agriculture 15 2010-01-01 2010-01-01 false Type of Leverage and application procedures....
7 CFR 4290.1100 - Type of Leverage and application procedures.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 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 available... 7 Agriculture 15 2011-01-01 2011-01-01 false Type of Leverage and application procedures....
13 CFR 107.1100 - Types of Leverage and application procedures.
Code of Federal Regulations, 2013 CFR
2013-01-01
... BUSINESS INVESTMENT COMPANIES SBA Financial Assistance for Licensees (Leverage) General Information About Obtaining Leverage § 107.1100 Types of Leverage and application procedures. (a) Types of Leverageable... 13 Business Credit and Assistance 1 2013-01-01 2013-01-01 false Types of Leverage and...
13 CFR 107.1100 - Types of Leverage and application procedures.
Code of Federal Regulations, 2012 CFR
2012-01-01
... BUSINESS INVESTMENT COMPANIES SBA Financial Assistance for Licensees (Leverage) General Information About Obtaining Leverage § 107.1100 Types of Leverage and application procedures. (a) Types of Leverageable... 13 Business Credit and Assistance 1 2012-01-01 2012-01-01 false Types of Leverage and...
7 CFR 4290.1100 - Type of Leverage and application procedures.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 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 available... 7 Agriculture 15 2013-01-01 2013-01-01 false Type of Leverage and application procedures....
7 CFR 4290.1100 - Type of Leverage and application procedures.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 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 available... 7 Agriculture 15 2014-01-01 2014-01-01 false Type of Leverage and application procedures....
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.
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
Leveraging HIPAA to support consumer empowerment.
Niedzwiecki, P; Priest, S L; Pivnicny, V C; Ruffino, B C
2000-01-01
The consumer empowerment movement needs to provide consumers with more access and control of their healthcare records. The premise of this article is that there is a fundamental market shift towards consumer empowerment--and technology is the driving force. We contend the results will satisfy the intent of the HIPAA mandate. Two restrictions impede the market from moving toward real consumer empowerment. First, managing one's own health history record is difficult because the complete record is segmented in disparate systems that are difficult to integrate. This is because unique identifiers and consistent coding are nonexistent. Second, security and control of patient identifiable health information is still evolving. There is no consensus among providers for Internet security, as we can see by all the legislative privacy bills trying to address the issue. HIPAA is both a legislative mandate and an enabler of the next healthcare paradigm. Providers must comply with the HIPAA mandates for electronic data interchange (EDI) code sets, administrative simplification, and privacy and confidentiality protocols. By recognizing HIPAA as part of a consumer-driven movement, organizations can incorporate empowerment strategies into a planning process that creates consumer options in healthcare and leverages HIPAA compliance to benefit both providers and consumers. This article suggests methods for meeting HIPAA compliance through innovative consumer empowerment methods.
Leveraging FPGAs for Accelerating Short Read Alignment.
Arram, James; Kaplan, Thomas; Luk, Wayne; Jiang, Peiyong
2016-02-29
One of the key challenges facing genomics today is how to efficiently analyse the massive amounts of data produced by next-generation sequencing platforms. With general-purpose computing systems struggling to address this challenge, specialised processors such as the Field-Programmable Gate Array (FPGA) are receiving growing interest. The means by which to leverage this technology for accelerating genomic data analysis is however largely unexplored. In this paper we present a runtime reconfigurable architecture for accelerating short read alignment using FPGAs. This architecture exploits the reconfigurability of FPGAs to allow the development of fast yet flexible alignment designs. We apply this architecture to develop an alignment design which supports exact and approximate alignment with up to 2 mismatches. Our design is based on the FM-index, with optimisations to improve the alignment performance. In particular, the n-step FM-index, index oversampling, a seedand- compare stage, and bi-directional backtracking are included. Our design is implemented and evaluated on a 1U Maxeler MPC-X2000 dataflow node with 8 Altera Stratix-V FPGAs. Measurements show that our design is 28 times faster than Bowtie2 running with 16 threads on dual Intel Xeon E5-2640 CPUs, and 9 times faster than Soap3-dp running on an NVIDIA Tesla C2070 GPU.
Leveraging systems biology approaches in clinical pharmacology
Melas, Ioannis N; Kretsos, Kosmas; Alexopoulos, Leonidas G
2013-01-01
Computational modeling has been adopted in all aspects of drug research and development, from the early phases of target identification and drug discovery to the late-stage clinical trials. The different questions addressed during each stage of drug R&D has led to the emergence of different modeling methodologies. In the research phase, systems biology couples experimental data with elaborate computational modeling techniques to capture lifecycle and effector cellular functions (e.g. metabolism, signaling, transcription regulation, protein synthesis and interaction) and integrates them in quantitative models. These models are subsequently used in various ways, i.e. to identify new targets, generate testable hypotheses, gain insights on the drug's mode of action (MOA), translate preclinical findings, and assess the potential of clinical drug efficacy and toxicity. In the development phase, pharmacokinetic/pharmacodynamic (PK/PD) modeling is the established way to determine safe and efficacious doses for testing at increasingly larger, and more pertinent to the target indication, cohorts of subjects. First, the relationship between drug input and its concentration in plasma is established. Second, the relationship between this concentration and desired or undesired PD responses is ascertained. Recognizing that the interface of systems biology with PK/PD will facilitate drug development, systems pharmacology came into existence, combining methods from PK/PD modeling and systems engineering explicitly to account for the implicated mechanisms of the target system in the study of drug–target interactions. Herein, a number of popular system biology methodologies are discussed, which could be leveraged within a systems pharmacology framework to address major issues in drug development. PMID:23983165