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Sample records for multilevel fwd loads

  1. New self-magnetically insulated connection of multilevel accelerators to a common load

    NASA Astrophysics Data System (ADS)

    VanDevender, J. Pace; Langston, William L.; Pasik, Michael F.; Coats, Rebecca S.; Pointon, Timothy D.; Seidel, David B.; McKee, G. Randal; Schneider, Larry X.

    2015-03-01

    A new way to connect pulsed-power modules to a common load is presented. Unlike previous connectors, the clam shell magnetically insulated transmission line (CSMITL) has magnetic nulls only at large radius where the cathode electric field is kept below the threshold for emission, has only a simply connected magnetic topology to avoid plasma motion along magnetic field lines into highly stressed gaps, and has electron injectors that ensure efficient electron flow even in the limiting case of self-limited MITLs. Multilevel magnetically insulated transmission lines with a posthole convolute are the standard solution but associated losses limit the performance of state-of-the-art accelerators. Mitigating these losses is critical for the next generation of pulsed-power accelerators. A CSMITL has been successfully implemented on the Saturn accelerator. A reference design for the Z accelerator is derived and presented. The design conservatively meets the design requirements and shows excellent transport efficiency in three simulations of increasing complexity: circuit simulations, electromagnetic fields only with Emphasis, fields plus electron and ion emission with Quicksilver.

  2. Teacher Education: Coming Up Empty. Fwd: Arresting Insights in Education. Volume 3, Number 1

    ERIC Educational Resources Information Center

    Walsh, Kate

    2006-01-01

    Kate Walsh, president of the National Council on Teacher Quality, takes on teacher education in this essay published for the Thomas B. Fordham Foundation's white paper series "Fwd: Arresting Insights in Education." Walsh highlights a 2005 study, "Studying Teacher Education," a nearly 800-page report by a panel of the American Educational Research…

  3. Comparison of Intervertebral ROM in Multi-Level Cadaveric Lumbar Spines Using Distinct Pure Moment Loading Approaches

    PubMed Central

    Santoni, Brandon; Cabezas, Andres F; Cook, Daniel J; Yeager, Matthew S; Billys, James B; Whiting, Benjamin

    2015-01-01

    Background Pure-moment loading is the test method of choice for spinal implant evaluation. However, the apparatuses and boundary conditions employed by laboratories in performing spine flexibility testing vary. The purpose of this study was to quantify the differences, if they exist, in intervertebral range of motion (ROM) resulting from different pure-moment loading apparatuses used in two laboratories. Methods Twenty-four (laboratory A) and forty-two (laboratory B) intact L1-S1 specimens were loaded using pure moments (±7.5 Nm) in flexion-extension (FE), lateral bending (LB) and axial torsion (AT). At laboratory A, pure moments were applied using a system of cables, pulleys and suspended weights in 1.5 Nm increments. At laboratory B, specimens were loaded in a pneumatic biaxial test frame mounted with counteracting stepper-motor-driven biaxial gimbals. ROM was obtained in both labs using identical optoelectronic systems and compared. Results In FE, total L1-L5 ROM was similar, on average, between the two laboratories (lab A: 37.4° ± 9.1°; lab B: 35.0° ± 8.9°, p=0.289). Larger apparent differences, on average, were noted between labs in AT (lab A: 19.4° ± 7.3°; lab B: 15.7° ± 7.1°, p=0.074), and this finding was significant for combined right and left LB (lab A: 45.5° ± 11.4°; lab B: 35.3° ± 8.5°, p < 0.001). Conclusions To our knowledge, this is the first study comparing ROM of multi-segment lumbar spines between laboratories utilizing different apparatuses. The results of this study show that intervertebral ROM in multi-segment lumbar spine constructs are markedly similar in FE loading. Differences in boundary conditions are likely the source of small and sometimes statistically significant differences between the two techniques in LB and AT ROM. The relative merits of each testing strategy with regard to the physiologic conditions that are to be simulated should be considered in the design of a study including LB and AT modes of loading. An

  4. Multilevel Model Prediction

    ERIC Educational Resources Information Center

    Frees, Edward W.; Kim, Jee-Seon

    2006-01-01

    Multilevel models are proven tools in social research for modeling complex, hierarchical systems. In multilevel modeling, statistical inference is based largely on quantification of random variables. This paper distinguishes among three types of random variables in multilevel modeling--model disturbances, random coefficients, and future response…

  5. Multilevel and Diverse Classrooms

    ERIC Educational Resources Information Center

    Baurain, Bradley, Ed.; Ha, Phan Le, Ed.

    2010-01-01

    The benefits and advantages of classroom practices incorporating unity-in-diversity and diversity-in-unity are what "Multilevel and Diverse Classrooms" is all about. Multilevel classrooms--also known as mixed-ability or heterogeneous classrooms--are a fact of life in ESOL programs around the world. These classrooms are often not only multilevel…

  6. Multilevel Mixture Factor Models

    ERIC Educational Resources Information Center

    Varriale, Roberta; Vermunt, Jeroen K.

    2012-01-01

    Factor analysis is a statistical method for describing the associations among sets of observed variables in terms of a small number of underlying continuous latent variables. Various authors have proposed multilevel extensions of the factor model for the analysis of data sets with a hierarchical structure. These Multilevel Factor Models (MFMs)…

  7. Multilevel filtering elliptic preconditioners

    NASA Technical Reports Server (NTRS)

    Kuo, C. C. Jay; Chan, Tony F.; Tong, Charles

    1989-01-01

    A class of preconditioners is presented for elliptic problems built on ideas borrowed from the digital filtering theory and implemented on a multilevel grid structure. They are designed to be both rapidly convergent and highly parallelizable. The digital filtering viewpoint allows the use of filter design techniques for constructing elliptic preconditioners and also provides an alternative framework for understanding several other recently proposed multilevel preconditioners. Numerical results are presented to assess the convergence behavior of the new methods and to compare them with other preconditioners of multilevel type, including the usual multigrid method as preconditioner, the hierarchical basis method and a recent method proposed by Bramble-Pasciak-Xu.

  8. Multilevel ensemble Kalman filtering

    DOE PAGESBeta

    Hoel, Hakon; Law, Kody J. H.; Tempone, Raul

    2016-06-14

    This study embeds a multilevel Monte Carlo sampling strategy into the Monte Carlo step of the ensemble Kalman filter (EnKF) in the setting of finite dimensional signal evolution and noisy discrete-time observations. The signal dynamics is assumed to be governed by a stochastic differential equation (SDE), and a hierarchy of time grids is introduced for multilevel numerical integration of that SDE. Finally, the resulting multilevel EnKF is proved to asymptotically outperform EnKF in terms of computational cost versus approximation accuracy. The theoretical results are illustrated numerically.

  9. Three simultaneous, food-borne, multi-country outbreaks of hepatitis A virus infection reported in EPIS-FWD in 2013: what does it mean for the European Union?

    PubMed

    Gossner, C M; Severi, E

    2014-01-01

    Between March and May 2013, three multi-country outbreaks of hepatitis A virus (HAV) infection were reported through the Epidemic Intelligence Information System for Food- and Water-borne diseases (EPIS-FWD) of the European Centre for Disease Prevention and Control (ECDC). The aim of this work is to put these outbreaks into a European Union (EU) and European Economic Area (EEA) perspective and highlight opportunities for improving detection and investigation of such outbreaks. Although HAV outbreaks are not unusual in the EU/EEA, having three large food-borne multi-country outbreaks declared within three months is an unexpected event, particularly when at least two of these outbreaks are associated with frozen berries. Factors influencing the occurrence of these events include the increased number of susceptible Europeans, the limited coverage of HAV vaccination, the global trade of potentially contaminated products introduced in the EU/EEA, and the 'awareness chain effect' leading to a wave of notifications. Further studies should be conducted to understand the risk posed by frozen berries. Laboratory capacity and surveillance of viral infections in the EU/EEA, as well as HAV vaccination recommendations to travellers to endemic countries should be strengthened. Finally, timely reporting food-borne events through EPIS-FWD, to ensure timely response. PMID:25375903

  10. Multilevel Interventions: Measurement and Measures

    PubMed Central

    Charns, Martin P.; Alligood, Elaine C.; Benzer, Justin K.; Burgess, James F.; Mcintosh, Nathalie M.; Burness, Allison; Partin, Melissa R.; Clauser, Steven B.

    2012-01-01

    Background Multilevel intervention research holds the promise of more accurately representing real-life situations and, thus, with proper research design and measurement approaches, facilitating effective and efficient resolution of health-care system challenges. However, taking a multilevel approach to cancer care interventions creates both measurement challenges and opportunities. Methods One-thousand seventy two cancer care articles from 2005 to 2010 were reviewed to examine the state of measurement in the multilevel intervention cancer care literature. Ultimately, 234 multilevel articles, 40 involving cancer care interventions, were identified. Additionally, literature from health services, social psychology, and organizational behavior was reviewed to identify measures that might be useful in multilevel intervention research. Results The vast majority of measures used in multilevel cancer intervention studies were individual level measures. Group-, organization-, and community-level measures were rarely used. Discussion of the independence, validity, and reliability of measures was scant. Discussion Measurement issues may be especially complex when conducting multilevel intervention research. Measurement considerations that are associated with multilevel intervention research include those related to independence, reliability, validity, sample size, and power. Furthermore, multilevel intervention research requires identification of key constructs and measures by level and consideration of interactions within and across levels. Thus, multilevel intervention research benefits from thoughtful theory-driven planning and design, an interdisciplinary approach, and mixed methods measurement and analysis. PMID:22623598

  11. Recent developments in multilevel optimization

    NASA Technical Reports Server (NTRS)

    Vanderplaats, Garret N.; Kim, D.-S.

    1989-01-01

    Recent developments in multilevel optimization are briefly reviewed. The general nature of the multilevel design task, the use of approximations to develop and solve the analysis design task, the structure of the formal multidiscipline optimization problem, a simple cantilevered beam which demonstrates the concepts of multilevel design and the basic mathematical details of the optimization task and the system level are among the topics discussed.

  12. Voltage balanced multilevel voltage source converter system

    DOEpatents

    Peng, F.Z.; Lai, J.S.

    1997-07-01

    Disclosed is a voltage balanced multilevel converter for high power AC applications such as adjustable speed motor drives and back-to-back DC intertie of adjacent power systems. This converter provides a multilevel rectifier, a multilevel inverter, and a DC link between the rectifier and the inverter allowing voltage balancing between each of the voltage levels within the multilevel converter. The rectifier is equipped with at least one phase leg and a source input node for each of the phases. The rectifier is further equipped with a plurality of rectifier DC output nodes. The inverter is equipped with at least one phase leg and a load output node for each of the phases. The inverter is further equipped with a plurality of inverter DC input nodes. The DC link is equipped with a plurality of rectifier charging means and a plurality of inverter discharging means. The plurality of rectifier charging means are connected in series with one of the rectifier charging means disposed between and connected in an operable relationship with each adjacent pair of rectifier DC output nodes. The plurality of inverter discharging means are connected in series with one of the inverter discharging means disposed between and connected in an operable relationship with each adjacent pair of inverter DC input nodes. Each of said rectifier DC output nodes are individually electrically connected to the respective inverter DC input nodes. By this means, each of the rectifier DC output nodes and each of the inverter DC input nodes are voltage balanced by the respective charging and discharging of the rectifier charging means and the inverter discharging means. 15 figs.

  13. Voltage balanced multilevel voltage source converter system

    DOEpatents

    Peng, Fang Zheng; Lai, Jih-Sheng

    1997-01-01

    A voltage balanced multilevel converter for high power AC applications such as adjustable speed motor drives and back-to-back DC intertie of adjacent power systems. This converter provides a multilevel rectifier, a multilevel inverter, and a DC link between the rectifier and the inverter allowing voltage balancing between each of the voltage levels within the multilevel converter. The rectifier is equipped with at least one phase leg and a source input node for each of the phases. The rectifier is further equipped with a plurality of rectifier DC output nodes. The inverter is equipped with at least one phase leg and a load output node for each of the phases. The inverter is further equipped with a plurality of inverter DC input nodes. The DC link is equipped with a plurality of rectifier charging means and a plurality of inverter discharging means. The plurality of rectifier charging means are connected in series with one of the rectifier charging means disposed between and connected in an operable relationship with each adjacent pair of rectifier DC output nodes. The plurality of inverter discharging means are connected in series with one of the inverter discharging means disposed between and connected in an operable relationship with each adjacent pair of inverter DC input nodes. Each of said rectifier DC output nodes are individually electrically connected to the respective inverter DC input nodes. By this means, each of the rectifier DC output nodes and each of the inverter DC input nodes are voltage balanced by the respective charging and discharging of the rectifier charging means and the inverter discharging means.

  14. A Primer on Multilevel Modeling

    ERIC Educational Resources Information Center

    Hayes, Andrew F.

    2006-01-01

    Multilevel modeling (MLM) is growing in use throughout the social sciences. Although daunting from a mathematical perspective, MLM is relatively easy to employ once some basic concepts are understood. In this article, I present a primer on MLM, describing some of these principles and applying them to the analysis of a multilevel data set on…

  15. Multilevel Modeling of Social Segregation

    ERIC Educational Resources Information Center

    Leckie, George; Pillinger, Rebecca; Jones, Kelvyn; Goldstein, Harvey

    2012-01-01

    The traditional approach to measuring segregation is based upon descriptive, non-model-based indices. A recently proposed alternative is multilevel modeling. The authors further develop the argument for a multilevel modeling approach by first describing and expanding upon its notable advantages, which include an ability to model segregation at a…

  16. Multilevel optimisation of aerospace and lightweight structures incorporating postbuckling effects

    NASA Astrophysics Data System (ADS)

    Qu, Shuang

    The optimisation of aerospace structures is a very complex problem, due to the hundreds of design variables a multidisciplinary optimisation may contain, so that multilevel optimisation is required. This thesis presents the recent developments to the multilevel optimisation software VICONOPT MLO, which is a multilevel optimisation interface between the well established analysis and design software packages VICONOPT and MSC/NASTRAN. The software developed is called VICONOPT MLOP (Multilevel Optimisation with Postbuckling), and allows for postbuckling behaviour, using analysis based on the Wittrick-Williams algorithm. The objective of this research is to enable a more detailed insight into the multilevel optimisation and postbuckling behaviour of a complex structure. In VICONOPT MLOP optimisation problems, individual panels of the structural model are allowed to buckle before the design load is reached. These panels continue to carry load with differing levels of reduced stiffness. VICONOPT MLOP creates new MSC/NASTRAN data files based on this reduced stiffness data and iterates through analysis cycles to converge on an appropriate load re-distribution. Once load convergence has been obtained with an appropriate criterion, the converged load distribution is used as a starting point in the optimisation of the constituent panels, i.e. a new design cycle is started, in which the updated ply thicknesses for each panel are calculated by VICONOPT and returned to MSC/NASTRAN through VICONOPT MLOP. Further finite element analysis of the whole structure is then carried out to determine the new stress distributions in each panel. The whole process is repeated until a mass convergence criterion is met. A detailed overview of the functionality of VICONOPT MLOP is presented in the thesis. A case study is conducted into the multilevel optimisation of a composite aircraft wing, to demonstrate the capabilities of VICONOPT MLOP and identify areas for future studies. The results of

  17. Multilevel DC link inverter

    DOEpatents

    Su, Gui-Jia

    2003-06-10

    A multilevel DC link inverter and method for improving torque response and current regulation in permanent magnet motors and switched reluctance motors having a low inductance includes a plurality of voltage controlled cells connected in series for applying a resulting dc voltage comprised of one or more incremental dc voltages. The cells are provided with switches for increasing the resulting applied dc voltage as speed and back EMF increase, while limiting the voltage that is applied to the commutation switches to perform PWM or dc voltage stepping functions, so as to limit current ripple in the stator windings below an acceptable level, typically 5%. Several embodiments are disclosed including inverters using IGBT's, inverters using thyristors. All of the inverters are operable in both motoring and regenerating modes.

  18. Parallel multilevel preconditioners

    SciTech Connect

    Bramble, J.H.; Pasciak, J.E.; Xu, Jinchao.

    1989-01-01

    In this paper, we shall report on some techniques for the development of preconditioners for the discrete systems which arise in the approximation of solutions to elliptic boundary value problems. Here we shall only state the resulting theorems. It has been demonstrated that preconditioned iteration techniques often lead to the most computationally effective algorithms for the solution of the large algebraic systems corresponding to boundary value problems in two and three dimensional Euclidean space. The use of preconditioned iteration will become even more important on computers with parallel architecture. This paper discusses an approach for developing completely parallel multilevel preconditioners. In order to illustrate the resulting algorithms, we shall describe the simplest application of the technique to a model elliptic problem.

  19. Multilevel techniques for nonelliptic problems

    NASA Technical Reports Server (NTRS)

    Jespersen, D. C.

    1981-01-01

    Multigrid and multilevel methods are extended to the solution of nonelliptic problems. A framework for analyzing these methods is established. A simple nonelliptic problem is given, and it is shown how a multilevel technique can be used for its solution. Emphasis is on smoothness properties of eigenvectors and attention is drawn to the possibility of conditioning the eigensystem so that eigenvectors have the desired smoothness properties.

  20. Multilevel fusion exploitation

    NASA Astrophysics Data System (ADS)

    Lindberg, Perry C.; Dasarathy, Belur V.; McCullough, Claire L.

    1996-06-01

    This paper describes a project that was sponsored by the U.S. Army Space and Strategic Defense Command (USASSDC) to develop, test, and demonstrate sensor fusion algorithms for target recognition. The purpose of the project was to exploit the use of sensor fusion at all levels (signal, feature, and decision levels) and all combinations to improve target recognition capability against tactical ballistic missile (TBM) targets. These algorithms were trained with simulated radar signatures to accurately recognize selected TBM targets. The simulated signatures represent measurements made by two radars (S-band and X- band) with the targets at a variety of aspect and roll angles. Two tests were conducted: one with simulated signatures collected at angles different from those in the training database and one using actual test data. The test results demonstrate a high degree of recognition accuracy. This paper describes the training and testing techniques used; shows the fusion strategy employed; and illustrates the advantages of exploiting multi-level fusion.

  1. Multilevel turbulence simulations

    SciTech Connect

    Tziperman, E.

    1994-12-31

    The authors propose a novel method for the simulation of turbulent flows, that is motivated by and based on the Multigrid (MG) formalism. The method, called Multilevel Turbulence Simulations (MTS), is potentially more efficient and more accurate than LES. In many physical problems one is interested in the effects of the small scales on the larger ones, or in a typical realization of the flow, and not in the detailed time history of each small scale feature. MTS takes advantage of the fact that the detailed simulation of small scales is not needed at all times, in order to make the calculation significantly more efficient, while accurately accounting for the effects of the small scales on the larger scale of interest. In MTS, models of several resolutions are used to represent the turbulent flow. The model equations in each coarse level incorporate a closure term roughly corresponding to the tau correction in the MG formalism that accounts for the effects of the unresolvable scales on that grid. The finer resolution grids are used only a small portion of the simulation time in order to evaluate the closure terms for the coarser grids, while the coarse resolution grids are then used to accurately and efficiently calculate the evolution of the larger scales. The methods efficiency relative to direct simulations is of the order of the ratio of required integration time to the smallest eddies turnover time, potentially resulting in orders of magnitude improvement for a large class of turbulence problems.

  2. Multilevel codes and multistage decoding

    NASA Astrophysics Data System (ADS)

    Calderbank, A. R.

    1989-03-01

    Imai and Hirakawa have proposed (1977) a multilevel coding method based on binary block codes that admits a staged decoding procedure. Here the coding method is extended to coset codes and it is shown how to calculate minimum squared distance and path multiplicity in terms of the norms and multiplicities of the different cosets. The multilevel structure allows the redundancy in the coset selection procedure to be allocated efficiently among the different levels. It also allows the use of suboptimal multistage decoding procedures that have performance/complexity advantages over maximum-likelihood decoding.

  3. Multilevel Ensemble Transform Particle Filtering

    NASA Astrophysics Data System (ADS)

    Gregory, Alastair; Cotter, Colin; Reich, Sebastian

    2016-04-01

    This presentation extends the Multilevel Monte Carlo variance reduction technique to nonlinear filtering. In particular, Multilevel Monte Carlo is applied to a certain variant of the particle filter, the Ensemble Transform Particle Filter (ETPF). A key aspect is the use of optimal transport methods to re-establish correlation between coarse and fine ensembles after resampling; this controls the variance of the estimator. Numerical examples present a proof of concept of the effectiveness of the proposed method, demonstrating significant computational cost reductions (relative to the single-level ETPF counterpart) in the propagation of ensembles.

  4. A General Multilevel SEM Framework for Assessing Multilevel Mediation

    ERIC Educational Resources Information Center

    Preacher, Kristopher J.; Zyphur, Michael J.; Zhang, Zhen

    2010-01-01

    Several methods for testing mediation hypotheses with 2-level nested data have been proposed by researchers using a multilevel modeling (MLM) paradigm. However, these MLM approaches do not accommodate mediation pathways with Level-2 outcomes and may produce conflated estimates of between- and within-level components of indirect effects. Moreover,…

  5. Multilevel Modeling with Correlated Effects

    ERIC Educational Resources Information Center

    Kim, Jee-Seon; Frees, Edward W.

    2007-01-01

    When there exist omitted effects, measurement error, and/or simultaneity in multilevel models, explanatory variables may be correlated with random components, and standard estimation methods do not provide consistent estimates of model parameters. This paper introduces estimators that are consistent under such conditions. By employing generalized…

  6. Multilevel algorithms for nonlinear optimization

    NASA Technical Reports Server (NTRS)

    Alexandrov, Natalia; Dennis, J. E., Jr.

    1994-01-01

    Multidisciplinary design optimization (MDO) gives rise to nonlinear optimization problems characterized by a large number of constraints that naturally occur in blocks. We propose a class of multilevel optimization methods motivated by the structure and number of constraints and by the expense of the derivative computations for MDO. The algorithms are an extension to the nonlinear programming problem of the successful class of local Brown-Brent algorithms for nonlinear equations. Our extensions allow the user to partition constraints into arbitrary blocks to fit the application, and they separately process each block and the objective function, restricted to certain subspaces. The methods use trust regions as a globalization strategy, and they have been shown to be globally convergent under reasonable assumptions. The multilevel algorithms can be applied to all classes of MDO formulations. Multilevel algorithms for solving nonlinear systems of equations are a special case of the multilevel optimization methods. In this case, they can be viewed as a trust-region globalization of the Brown-Brent class.

  7. Generalized Multilevel Structural Equation Modeling

    ERIC Educational Resources Information Center

    Rabe-Hesketh, Sophia; Skrondal, Anders; Pickles, Andrew

    2004-01-01

    A unifying framework for generalized multilevel structural equation modeling is introduced. The models in the framework, called generalized linear latent and mixed models (GLLAMM), combine features of generalized linear mixed models (GLMM) and structural equation models (SEM) and consist of a response model and a structural model for the latent…

  8. Cascaded H-bridge multilevel inverter for renewable energy generation

    NASA Astrophysics Data System (ADS)

    Pandey, Ravikant; Nath Tripathi, Ravi; Hanamoto, Tsuyoshi

    2016-04-01

    In this paper cascaded H-bridge multilevel inverter (CHBMLI) has been investigated for the application of renewable energy generation. Energy sources like solar, wind, hydro, biomass or combination of these can be manipulated to obtain alternative sources for renewable energy generation. These renewable energy sources have different electrical characteristics like DC or AC level so it is challenging to use generated power by connecting to grid or load directly. The renewable energy source require specific power electronics converter as an interface for conditioning generated power .The multilevel inverter can be utilized for renewable energy sources in two different modes, the power generation mode (stand-alone mode), and compensator mode (statcom). The performance of the multilevel inverter has been compared with two level inverter. In power generation mode CHBMLI supplies the active and reactive power required by the different loads. For operation in compensator mode the indirect current control based on synchronous reference frame theory (SRFT) ensures the grid operating in unity power factor and compensate harmonics and reactive power.

  9. A multilevel stochastic collocation method for SPDEs

    SciTech Connect

    Gunzburger, Max; Jantsch, Peter; Teckentrup, Aretha; Webster, Clayton

    2015-03-10

    We present a multilevel stochastic collocation method that, as do multilevel Monte Carlo methods, uses a hierarchy of spatial approximations to reduce the overall computational complexity when solving partial differential equations with random inputs. For approximation in parameter space, a hierarchy of multi-dimensional interpolants of increasing fidelity are used. Rigorous convergence and computational cost estimates for the new multilevel stochastic collocation method are derived and used to demonstrate its advantages compared to standard single-level stochastic collocation approximations as well as multilevel Monte Carlo methods.

  10. Experimental Model of Proximal Junctional Fracture after Multilevel Posterior Spinal Instrumentation

    PubMed Central

    Levasseur, Annie; Parent, Stefan; Petit, Yvan

    2016-01-01

    There is a high risk of proximal junctional fractures (PJF) with multilevel spinal instrumentation, especially in the osteoporotic spine. This problem is associated with significant morbidity and possibly the need for reoperation. Various techniques have been proposed in an attempt to decrease the risk of PJF but there is no experimental model described for in vitro production of PJF after multilevel instrumentation. The objective of this study is to develop an experimental model of PJF after multilevel posterior instrumentation. Initially, four porcine specimens including 4 vertebrae and instrumented at the 3 caudal vertebrae using a pedicle screw construct were subjected to different loading conditions. Loading conditions on porcine specimens involving cyclic loading along the axis of the center vertebral body line, with constrained flexion between 0° and 15° proximally, and fully constraining the specimen distally resulted in a fracture pattern most representative of a PJF seen clinically in humans, so to undergo human cadaveric testing with similar loading conditions was decided. Clinically relevant PJF were produced in all 3 human specimens. The experimental model described in this study will allow the evaluation of different parameters influencing the incidence and prevention of PJF after multilevel posterior spinal instrumentation. PMID:27610381

  11. Experimental Model of Proximal Junctional Fracture after Multilevel Posterior Spinal Instrumentation.

    PubMed

    Mac-Thiong, Jean-Marc; Levasseur, Annie; Parent, Stefan; Petit, Yvan

    2016-01-01

    There is a high risk of proximal junctional fractures (PJF) with multilevel spinal instrumentation, especially in the osteoporotic spine. This problem is associated with significant morbidity and possibly the need for reoperation. Various techniques have been proposed in an attempt to decrease the risk of PJF but there is no experimental model described for in vitro production of PJF after multilevel instrumentation. The objective of this study is to develop an experimental model of PJF after multilevel posterior instrumentation. Initially, four porcine specimens including 4 vertebrae and instrumented at the 3 caudal vertebrae using a pedicle screw construct were subjected to different loading conditions. Loading conditions on porcine specimens involving cyclic loading along the axis of the center vertebral body line, with constrained flexion between 0° and 15° proximally, and fully constraining the specimen distally resulted in a fracture pattern most representative of a PJF seen clinically in humans, so to undergo human cadaveric testing with similar loading conditions was decided. Clinically relevant PJF were produced in all 3 human specimens. The experimental model described in this study will allow the evaluation of different parameters influencing the incidence and prevention of PJF after multilevel posterior spinal instrumentation. PMID:27610381

  12. Conducting Multilevel Analyses in Medical Education

    ERIC Educational Resources Information Center

    Zyphur, Michael J.; Kaplan, Seth A.; Islam, Gazi; Barsky, Adam P.; Franklin, Michael S.

    2008-01-01

    A significant body of education literature has begun using multilevel statistical models to examine data that reside at multiple levels of analysis. In order to provide a primer for medical education researchers, the current work gives a brief overview of some issues associated with multilevel statistical modeling. To provide an example of this…

  13. A Multilevel Assessment of Differential Item Functioning.

    ERIC Educational Resources Information Center

    Shen, Linjun

    A multilevel approach was proposed for the assessment of differential item functioning and compared with the traditional logistic regression approach. Data from the Comprehensive Osteopathic Medical Licensing Examination for 2,300 freshman osteopathic medical students were analyzed. The multilevel approach used three-level hierarchical generalized…

  14. Multilevel Interventions: Study Design and Analysis Issues

    PubMed Central

    Gross, Cary P.; Zaslavsky, Alan M.; Taplin, Stephen H.

    2012-01-01

    Multilevel interventions, implemented at the individual, physician, clinic, health-care organization, and/or community level, increasingly are proposed and used in the belief that they will lead to more substantial and sustained changes in behaviors related to cancer prevention, detection, and treatment than would single-level interventions. It is important to understand how intervention components are related to patient outcomes and identify barriers to implementation. Designs that permit such assessments are uncommon, however. Thus, an important way of expanding our knowledge about multilevel interventions would be to assess the impact of interventions at different levels on patients as well as the independent and synergistic effects of influences from different levels. It also would be useful to assess the impact of interventions on outcomes at different levels. Multilevel interventions are much more expensive and complicated to implement and evaluate than are single-level interventions. Given how little evidence there is about the value of multilevel interventions, however, it is incumbent upon those arguing for this approach to do multilevel research that explicates the contributions that interventions at different levels make to the desired outcomes. Only then will we know whether multilevel interventions are better than more focused interventions and gain greater insights into the kinds of interventions that can be implemented effectively and efficiently to improve health and health care for individuals with cancer. This chapter reviews designs for assessing multilevel interventions and analytic ways of controlling for potentially confounding variables that can account for the complex structure of multilevel data. PMID:22623596

  15. Structural optimization by multilevel decomposition

    NASA Technical Reports Server (NTRS)

    Sobieszczanski-Sobieski, J.; James, B.; Dovi, A.

    1983-01-01

    A method is described for decomposing an optimization problem into a set of subproblems and a coordination problem which preserves coupling between the subproblems. The method is introduced as a special case of multilevel, multidisciplinary system optimization and its algorithm is fully described for two level optimization for structures assembled of finite elements of arbitrary type. Numerical results are given for an example of a framework to show that the decomposition method converges and yields results comparable to those obtained without decomposition. It is pointed out that optimization by decomposition should reduce the design time by allowing groups of engineers, using different computers to work concurrently on the same large problem.

  16. Planarization of metal films for multilevel interconnects

    DOEpatents

    Tuckerman, D.B.

    1989-03-21

    In the fabrication of multilevel integrated circuits, each metal layer is planarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration. 6 figs.

  17. Planarization of metal films for multilevel interconnects

    DOEpatents

    Tuckerman, David B.

    1987-01-01

    In the fabrication of multilevel integrated circuits, each metal layer is anarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

  18. Planarization of metal films for multilevel interconnects

    DOEpatents

    Tuckerman, David B.

    1989-01-01

    In the fabrication of multilevel integrated circuits, each metal layer is anarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

  19. Planarization of metal films for multilevel interconnects

    DOEpatents

    Tuckerman, D.B.

    1985-08-23

    In the fabrication of multilevel integrated circuits, each metal layer is planarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

  20. Planarization of metal films for multilevel interconnects

    DOEpatents

    Tuckerman, D.B.

    1985-06-24

    In the fabrication of multilevel integrated circuits, each metal layer is planarized by heating to momentarily melt the layer. The layer is melted by sweeping lase pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

  1. Scalable Adaptive Multilevel Solvers for Multiphysics Problems

    SciTech Connect

    Xu, Jinchao

    2014-12-01

    In this project, we investigated adaptive, parallel, and multilevel methods for numerical modeling of various real-world applications, including Magnetohydrodynamics (MHD), complex fluids, Electromagnetism, Navier-Stokes equations, and reservoir simulation. First, we have designed improved mathematical models and numerical discretizaitons for viscoelastic fluids and MHD. Second, we have derived new a posteriori error estimators and extended the applicability of adaptivity to various problems. Third, we have developed multilevel solvers for solving scalar partial differential equations (PDEs) as well as coupled systems of PDEs, especially on unstructured grids. Moreover, we have integrated the study between adaptive method and multilevel methods, and made significant efforts and advances in adaptive multilevel methods of the multi-physics problems.

  2. Impact of Not Addressing Partially Cross-Classified Multilevel Structure in Testing Measurement Invariance: A Monte Carlo Study

    PubMed Central

    Im, Myung H.; Kim, Eun S.; Kwok, Oi-Man; Yoon, Myeongsun; Willson, Victor L.

    2016-01-01

    In educational settings, researchers are likely to encounter multilevel data with cross-classified structure. However, due to the lack of familiarity and limitations of statistical software for cross-classified modeling, most researchers adopt less optimal approaches to analyze cross-classified multilevel data in testing measurement invariance. We conducted two Monte Carlo studies to investigate the performances of testing measurement invariance with cross-classified multilevel data when the noninvarinace is at the between-level: (a) the impact of ignoring crossed factor using conventional multilevel confirmatory factor analysis (MCFA) which assumes hierarchical multilevel data in testing measurement invariance and (b) the adequacy of the cross-classified multiple indicators multiple causes (MIMIC) models with cross-classified data. We considered two design factors, intraclass correlation (ICC) and magnitude of non-invariance. Generally, MCFA demonstrated very low statistical power to detect non-invariance. The low power was plausibly related to the underestimated factor loading differences and the underestimated ICC due to the redistribution of the variance component from the ignored crossed factor. The results demonstrated possible incorrect statistical inferences with conventional MCFA analyses that assume multilevel data as hierarchical structure for testing measurement invariance with cross-classified data (non-hierarchical structure). On the contrary, the cross-classified MIMIC model demonstrated acceptable performance with cross-classified data. PMID:27047404

  3. Alternative Methods for Assessing Mediation in Multilevel Data: The Advantages of Multilevel SEM

    ERIC Educational Resources Information Center

    Preacher, Kristopher J.; Zhang, Zhen; Zyphur, Michael J.

    2011-01-01

    Multilevel modeling (MLM) is a popular way of assessing mediation effects with clustered data. Two important limitations of this approach have been identified in prior research and a theoretical rationale has been provided for why multilevel structural equation modeling (MSEM) should be preferred. However, to date, no empirical evidence of MSEM's…

  4. Applications of cascade multilevel inverters.

    PubMed

    Peng, Fang-zen; Qian, Zhao-ming

    2003-01-01

    Cascade multilevel inverters have been developed for electric utility applications. A cascade M-level inverter consists of (M-1)/2 H-bridges in which each bridge's dc voltage is supported by its own dc capacitor. The new inverter can: (1) generate almost sinusoidal waveform voltage while only switching one time per fundamental cycle; (2) dispense with multi-pulse inverters' transformers used in conventional utility interfaces and static var compensators; (3) enables direct parallel or series transformer-less connection to medium- and high-voltage power systems. In short, the cascade inverter is much more efficient and suitable for utility applications than traditional multi-pulse and pulse width modulation (PWM) inverters. The authors have experimentally demonstrated the superiority of the new inverter for power supply, (hybrid) electric vehicle (EV) motor drive, reactive power (var) and harmonic compensation. This paper summarizes the features, feasibility, and control schemes of the cascade inverter for utility applications including utility interface of renewable energy, voltage regulation, var compensation, and harmonic filtering in power systems. Analytical, simulated, and experimental results demonstrated the superiority of the new inverters. PMID:14566981

  5. Multilevel Complex Networks and Systems

    NASA Astrophysics Data System (ADS)

    Caldarelli, Guido

    2014-03-01

    Network theory has been a powerful tool to model isolated complex systems. However, the classical approach does not take into account the interactions often present among different systems. Hence, the scientific community is nowadays concentrating the efforts on the foundations of new mathematical tools for understanding what happens when multiple networks interact. The case of economic and financial networks represents a paramount example of multilevel networks. In the case of trade, trade among countries the different levels can be described by the different granularity of the trading relations. Indeed, we have now data from the scale of consumers to that of the country level. In the case of financial institutions, we have a variety of levels at the same scale. For example one bank can appear in the interbank networks, ownership network and cds networks in which the same institution can take place. In both cases the systemically important vertices need to be determined by different procedures of centrality definition and community detection. In this talk I will present some specific cases of study related to these topics and present the regularities found. Acknowledged support from EU FET Project ``Multiplex'' 317532.

  6. Multilevel sequential Monte Carlo samplers

    DOE PAGESBeta

    Beskos, Alexandros; Jasra, Ajay; Law, Kody; Tempone, Raul; Zhou, Yan

    2016-08-24

    Here, we study the approximation of expectations w.r.t. probability distributions associated to the solution of partial differential equations (PDEs); this scenario appears routinely in Bayesian inverse problems. In practice, one often has to solve the associated PDE numerically, using, for instance finite element methods and leading to a discretisation bias, with the step-size level hL. In addition, the expectation cannot be computed analytically and one often resorts to Monte Carlo methods. In the context of this problem, it is known that the introduction of the multilevel Monte Carlo (MLMC) method can reduce the amount of computational effort to estimate expectations, for a given level of error. This is achieved via a telescoping identity associated to a Monte Carlo approximation of a sequence of probability distributions with discretisation levelsmore » $${\\infty}$$ >h0>h1 ...>hL. In many practical problems of interest, one cannot achieve an i.i.d. sampling of the associated sequence of probability distributions. A sequential Monte Carlo (SMC) version of the MLMC method is introduced to deal with this problem. In conclusion, it is shown that under appropriate assumptions, the attractive property of a reduction of the amount of computational effort to estimate expectations, for a given level of error, can be maintained within the SMC context.« less

  7. GPU-based Multilevel Clustering.

    PubMed

    Chiosa, Iurie; Kolb, Andreas

    2010-04-01

    The processing power of parallel co-processors like the Graphics Processing Unit (GPU) are dramatically increasing. However, up until now only a few approaches have been presented to utilize this kind of hardware for mesh clustering purposes. In this paper we introduce a Multilevel clustering technique designed as a parallel algorithm and solely implemented on the GPU. Our formulation uses the spatial coherence present in the cluster optimization and hierarchical cluster merging to significantly reduce the number of comparisons in both parts . Our approach provides a fast, high quality and complete clustering analysis. Furthermore, based on the original concept we present a generalization of the method to data clustering. All advantages of the meshbased techniques smoothly carry over to the generalized clustering approach. Additionally, this approach solves the problem of the missing topological information inherent to general data clustering and leads to a Local Neighbors k-means algorithm. We evaluate both techniques by applying them to Centroidal Voronoi Diagram (CVD) based clustering. Compared to classical approaches, our techniques generate results with at least the same clustering quality. Our technique proves to scale very well, currently being limited only by the available amount of graphics memory. PMID:20421676

  8. A multilevel preconditioner for domain decomposition boundary systems

    SciTech Connect

    Bramble, J.H.; Pasciak, J.E.; Xu, Jinchao.

    1991-12-11

    In this note, we consider multilevel preconditioning of the reduced boundary systems which arise in non-overlapping domain decomposition methods. It will be shown that the resulting preconditioned systems have condition numbers which be bounded in the case of multilevel spaces on the whole domain and grow at most proportional to the number of levels in the case of multilevel boundary spaces without multilevel extensions into the interior.

  9. Multi-level block permutation

    PubMed Central

    Winkler, Anderson M.; Webster, Matthew A.; Vidaurre, Diego; Nichols, Thomas E.; Smith, Stephen M.

    2015-01-01

    Under weak and reasonable assumptions, mainly that data are exchangeable under the null hypothesis, permutation tests can provide exact control of false positives and allow the use of various non-standard statistics. There are, however, various common examples in which global exchangeability can be violated, including paired tests, tests that involve repeated measurements, tests in which subjects are relatives (members of pedigrees) — any dataset with known dependence among observations. In these cases, some permutations, if performed, would create data that would not possess the original dependence structure, and thus, should not be used to construct the reference (null) distribution. To allow permutation inference in such cases, we test the null hypothesis using only a subset of all otherwise possible permutations, i.e., using only the rearrangements of the data that respect exchangeability, thus retaining the original joint distribution unaltered. In a previous study, we defined exchangeability for blocks of data, as opposed to each datum individually, then allowing permutations to happen within block, or the blocks as a whole to be permuted. Here we extend that notion to allow blocks to be nested, in a hierarchical, multi-level definition. We do not explicitly model the degree of dependence between observations, only the lack of independence; the dependence is implicitly accounted for by the hierarchy and by the permutation scheme. The strategy is compatible with heteroscedasticity and variance groups, and can be used with permutations, sign flippings, or both combined. We evaluate the method for various dependence structures, apply it to real data from the Human Connectome Project (HCP) as an example application, show that false positives can be avoided in such cases, and provide a software implementation of the proposed approach. PMID:26074200

  10. Mediation from Multilevel to Structural Equation Modeling

    PubMed Central

    MacKinnon, David P.; Valente, Matthew J.

    2016-01-01

    Background/Aims The purpose of this article is to outline multilevel structural equation modeling (MSEM) for mediation analysis of longitudinal data. The introduction of mediating variables can improve experimental and nonexperimental studies of child growth in several ways as discussed throughout this article. Single-mediator individual-level and multilevel mediation models illustrate several current issues in the estimation of mediation with longitudinal data. The strengths of incorporating structural equation modeling (SEM) with multilevel mediation modeling are described. Summary and Key Messages Longitudinal mediation models are pervasive in many areas of research including child growth. Longitudinal mediation models are ideally modeled as repeated measurements clustered within individuals. Further, the combination of MSEM and SEM provides an ideal approach for several reasons, including the ability to assess effects at different levels of analysis, incorporation of measurement error and possible random effects that vary across individuals. PMID:25413658

  11. Automatic multilevel medical image annotation and retrieval.

    PubMed

    Mueen, A; Zainuddin, R; Baba, M Sapiyan

    2008-09-01

    Image retrieval at the semantic level mostly depends on image annotation or image classification. Image annotation performance largely depends on three issues: (1) automatic image feature extraction; (2) a semantic image concept modeling; (3) algorithm for semantic image annotation. To address first issue, multilevel features are extracted to construct the feature vector, which represents the contents of the image. To address second issue, domain-dependent concept hierarchy is constructed for interpretation of image semantic concepts. To address third issue, automatic multilevel code generation is proposed for image classification and multilevel image annotation. We make use of the existing image annotation to address second and third issues. Our experiments on a specific domain of X-ray images have given encouraging results. PMID:17846834

  12. Multilevel modeling in psychosomatic medicine research.

    PubMed

    Myers, Nicholas D; Brincks, Ahnalee M; Ames, Allison J; Prado, Guillermo J; Penedo, Frank J; Benedict, Catherine

    2012-01-01

    The primary purpose of this study is to provide an overview of multilevel modeling for Psychosomatic Medicine readers and contributors. The article begins with a general introduction to multilevel modeling. Multilevel regression modeling at two levels is emphasized because of its prevalence in psychosomatic medicine research. Simulated data sets based on some core ideas from the Familias Unidas effectiveness study are used to illustrate key concepts including communication of model specification, parameter interpretation, sample size and power, and missing data. Input and key output files from Mplus and SAS are provided. A cluster randomized trial with repeated measures (i.e., three-level regression model) is then briefly presented with simulated data based on some core ideas from a cognitive-behavioral stress management intervention in prostate cancer. PMID:23107843

  13. Multilevel Modeling in Psychosomatic Medicine Research

    PubMed Central

    Myers, Nicholas D.; Brincks, Ahnalee M.; Ames, Allison J.; Prado, Guillermo J.; Penedo, Frank J.; Benedict, Catherine

    2012-01-01

    The primary purpose of this manuscript is to provide an overview of multilevel modeling for Psychosomatic Medicine readers and contributors. The manuscript begins with a general introduction to multilevel modeling. Multilevel regression modeling at two-levels is emphasized because of its prevalence in psychosomatic medicine research. Simulated datasets based on some core ideas from the Familias Unidas effectiveness study are used to illustrate key concepts including: communication of model specification, parameter interpretation, sample size and power, and missing data. Input and key output files from Mplus and SAS are provided. A cluster randomized trial with repeated measures (i.e., three-level regression model) is then briefly presented with simulated data based on some core ideas from a cognitive behavioral stress management intervention in prostate cancer. PMID:23107843

  14. Formulation and Application of the Generalized Multilevel Facets Model

    ERIC Educational Resources Information Center

    Wang, Wen-Chung; Liu, Chih-Yu

    2007-01-01

    In this study, the authors develop a generalized multilevel facets model, which is not only a multilevel and two-parameter generalization of the facets model, but also a multilevel and facet generalization of the generalized partial credit model. Because the new model is formulated within a framework of nonlinear mixed models, no efforts are…

  15. Multilevel transport solution of LWR reactor cores

    SciTech Connect

    Jose Ignacio Marquez Damian; Cassiano R.E. de Oliveira; HyeonKae Park

    2008-09-01

    This work presents a multilevel approach for the solution of the transport equation in typical LWR assemblies and core configurations. It is based on the second-order, even-parity formulation of the transport equation, which is solved within the framework provided by the finite element-spherical harmonics code EVENT. The performance of the new solver has been compared with that of the standard conjugate gradient solver for diffusion and transport problems on structured and unstruc-tured grids. Numerical results demonstrate the potential of the multilevel scheme for realistic reactor calculations.

  16. Constructions of Factorizable Multilevel Hadamard Matrices

    NASA Astrophysics Data System (ADS)

    Matsufuji, Shinya; Fan, Pingzhi

    Factorization of Hadamard matrices can provide fast algorithm and facilitate efficient hardware realization. In this letter, constructions of factorizable multilevel Hadamard matrices, which can be considered as special case of unitary matrices, are inverstigated. In particular, a class of ternary Hadamard matrices, together with its application, is presented.

  17. BER estimation for multilevel modulation formats

    NASA Astrophysics Data System (ADS)

    Louchet, Hadrien; Kuzmin, Konstantin; Koltchanov, Igor; Richter, André

    2009-11-01

    We review existing BER estimation methods and propose alternative methods to assess the performance of multilevel modulation formats with both direct and coherent detection. The impact of digital signal processing (DSP) on the BER estimation procedure is discussed for the latter case. The different approaches are illustrated by simulating exemplary transmission systems.

  18. Single-Level and Multilevel Mediation Analysis

    ERIC Educational Resources Information Center

    Tofighi, Davood; Thoemmes, Felix

    2014-01-01

    Mediation analysis is a statistical approach used to examine how the effect of an independent variable on an outcome is transmitted through an intervening variable (mediator). In this article, we provide a gentle introduction to single-level and multilevel mediation analyses. Using single-level data, we demonstrate an application of structural…

  19. New multilevel codes over GF(q)

    NASA Technical Reports Server (NTRS)

    Wu, Jiantian; Costello, Daniel J., Jr.

    1992-01-01

    Set partitioning to multi-dimensional signal spaces over GF(q), particularly GF sup q-1(q) and GF sup q (q), and show how to construct both multi-level block codes and multi-level trellis codes over GF(q). Two classes of multi-level (n, k, d) block codes over GF(q) with block length n, number of information symbols k, and minimum distance d sub min greater than or = d, are presented. These two classes of codes use Reed-Solomon codes as component codes. They can be easily decoded as block length q-1 Reed-Solomon codes or block length q or q + 1 extended Reed-Solomon codes using multi-stage decoding. Many of these codes have larger distances than comparable q-ary block codes, as component codes. Low rate q-ary convolutional codes, work error correcting convolutional codes, and binary-to-q-ary convolutional codes can also be used to construct multi-level trellis codes over GF(q) or binary-to-q-ary trellis codes, some of which have better performance than the above block codes. All of the new codes have simple decoding algorithms based on hard decision multi-stage decoding.

  20. Engineering applications of heuristic multilevel optimization methods

    NASA Technical Reports Server (NTRS)

    Barthelemy, Jean-Francois M.

    1989-01-01

    Some engineering applications of heuristic multilevel optimization methods are presented and the discussion focuses on the dependency matrix that indicates the relationship between problem functions and variables. Coordination of the subproblem optimizations is shown to be typically achieved through the use of exact or approximate sensitivity analysis. Areas for further development are identified.

  1. Engineering applications of heuristic multilevel optimization methods

    NASA Technical Reports Server (NTRS)

    Barthelemy, Jean-Francois M.

    1988-01-01

    Some engineering applications of heuristic multilevel optimization methods are presented and the discussion focuses on the dependency matrix that indicates the relationship between problem functions and variables. Coordination of the subproblem optimizations is shown to be typically achieved through the use of exact or approximate sensitivity analysis. Areas for further development are identified.

  2. Using Multilevel Modeling in Counseling Research

    ERIC Educational Resources Information Center

    Lynch, Martin F.

    2012-01-01

    This conceptual and practical overview of multilevel modeling (MLM) for researchers in counseling and development provides guidelines on setting up SPSS to perform MLM and an example of how to present the findings. It also provides a discussion on how counseling and developmental researchers can use MLM to address their own research questions.…

  3. Multilevel Factor Models for Ordinal Variables

    ERIC Educational Resources Information Center

    Grilli, Leonardo; Rampichini, Carla

    2007-01-01

    This article tackles several issues involved in specifying, fitting, and interpreting the results of multilevel factor models for ordinal variables. First, the problem of model specification and identification is addressed, outlining parameter interpretation. Special attention is devoted to the consequences on interpretation stemming from the…

  4. Efficiently Exploring Multilevel Data with Recursive Partitioning

    ERIC Educational Resources Information Center

    Martin, Daniel P.; von Oertzen, Timo; Rimm-Kaufman, Sara E.

    2015-01-01

    There is an increasing number of datasets with many participants, variables, or both, in education and other fields that often deal with large, multilevel data structures. Once initial confirmatory hypotheses are exhausted, it can be difficult to determine how best to explore the dataset to discover hidden relationships that could help to inform…

  5. A Practical Guide to Multilevel Modeling

    ERIC Educational Resources Information Center

    Peugh, James L.

    2010-01-01

    Collecting data from students within classrooms or schools, and collecting data from students on multiple occasions over time, are two common sampling methods used in educational research that often require multilevel modeling (MLM) data analysis techniques to avoid Type-1 errors. The purpose of this article is to clarify the seven major steps…

  6. Multilevel training of binary morphological operators.

    PubMed

    Hirata, Nina S T

    2009-04-01

    The design of binary morphological operators that are translation-invariant and locally defined by a finite neighborhood window corresponds to the problem of designing Boolean functions. As in any supervised classification problem, morphological operators designed from training sample also suffer from overfitting. Large neighborhood tends to lead to performance degradation of the designed operator. This work proposes a multi-level design approach to deal with the issue of designing large neighborhood based operators. The main idea is inspired from stacked generalization (a multi-level classifier design approach) and consists in, at each training level, combining the outcomes of the previous level operators. The final operator is a multi-level operator that ultimately depends on a larger neighborhood than of the individual operators that have been combined. Experimental results show that two-level operators obtained by combining operators designed on subwindows of a large window consistently outperforms the single-level operators designed on the full window. They also show that iterating two-level operators is an effective multi-level approach to obtain better results. PMID:19229085

  7. The Economic Cost of Homosexuality: Multilevel Analyses

    ERIC Educational Resources Information Center

    Baumle, Amanda K.; Poston, Dudley, Jr.

    2011-01-01

    This article builds on earlier studies that have examined "the economic cost of homosexuality," by using data from the 2000 U.S. Census and by employing multilevel analyses. Our findings indicate that partnered gay men experience a 12.5 percent earnings penalty compared to married heterosexual men, and a statistically insignificant earnings…

  8. Constrained Multi-Level Algorithm for Trajectory Optimization

    NASA Astrophysics Data System (ADS)

    Adimurthy, V.; Tandon, S. R.; Jessy, Antony; Kumar, C. Ravi

    The emphasis on low cost access to space inspired many recent developments in the methodology of trajectory optimization. Ref.1 uses a spectral patching method for optimization, where global orthogonal polynomials are used to describe the dynamical constraints. A two-tier approach of optimization is used in Ref.2 for a missile mid-course trajectory optimization. A hybrid analytical/numerical approach is described in Ref.3, where an initial analytical vacuum solution is taken and gradually atmospheric effects are introduced. Ref.4 emphasizes the fact that the nonlinear constraints which occur in the initial and middle portions of the trajectory behave very nonlinearly with respect the variables making the optimization very difficult to solve in the direct and indirect shooting methods. The problem is further made complex when different phases of the trajectory have different objectives of optimization and also have different path constraints. Such problems can be effectively addressed by multi-level optimization. In the multi-level methods reported so far, optimization is first done in identified sub-level problems, where some coordination variables are kept fixed for global iteration. After all the sub optimizations are completed, higher-level optimization iteration with all the coordination and main variables is done. This is followed by further sub system optimizations with new coordination variables. This process is continued until convergence. In this paper we use a multi-level constrained optimization algorithm which avoids the repeated local sub system optimizations and which also removes the problem of non-linear sensitivity inherent in the single step approaches. Fall-zone constraints, structural load constraints and thermal constraints are considered. In this algorithm, there is only a single multi-level sequence of state and multiplier updates in a framework of an augmented Lagrangian. Han Tapia multiplier updates are used in view of their special role in

  9. A grid-connected photovoltaic power conversion system with single-phase multilevel inverter

    SciTech Connect

    Beser, Ersoy; Arifoglu, Birol; Camur, Sabri; Beser, Esra Kandemir

    2010-12-15

    This paper presents a grid-connected photovoltaic (PV) power conversion system based on a single-phase multilevel inverter. The proposed system fundamentally consists of PV arrays and a single-phase multilevel inverter structure. First, configuration and structural parts of the PV assisted inverter system are introduced in detail. To produce reference output voltage waves, a simple switching strategy based on calculating switching angles is improved. By calculated switching angles, the reference signal is produced as a multilevel shaped output voltage wave. The control algorithm and operational principles of the proposed system are explained. Operating PV arrays in the same load condition is a considerable point; therefore a simulation study is performed to arrange the PV arrays. After determining the number and connection types of the PV arrays, the system is configured through the arrangement of the PV arrays. The validity of the proposed system is verified through simulations and experimental study. The results demonstrate that the system can achieve lower total harmonic distortion (THD) on the output voltage and load current, and it is capable of operating synchronous and transferring power values having different characteristic to the grid. Hence, it is suitable to use the proposed configuration as a PV power conversion system in various applications. (author)

  10. Research of Real-time Data Warehouse Storage Strategy Based on Multi-level Caches

    NASA Astrophysics Data System (ADS)

    YiChuan, Shao; Yao, Xingjia

    Real-time data warehouse extend the application of traditional data warehouse. It can not only support tactical queries for enterprise but also provide much variable tactical decision support effectively. For these reasons, it is very meaningful to research on the structure of real-time data warehouses. This paper introduced the background of real-time data warehouse and proposed the strategy of real-time data warehouse which is based on double mirror replication mechanism. The strategy is composed of double steps. First we used double mirror replication mechanism to enable continuous loading data in the real-time data warehouse with minimum impact in query execution time. Second we proposed incorporating multi-level caches into the data warehouse structure which is based on real-time partition and gave the process of design and implementation with details. We differentiated between queries with various data freshness requirements, and used multi-level caches to satisfy these different requirements.

  11. Efficiency Improvements to the Displacement Based Multilevel Structural Optimization Algorithm

    NASA Technical Reports Server (NTRS)

    Plunkett, C. L.; Striz, A. G.; Sobieszczanski-Sobieski, J.

    2001-01-01

    Multilevel Structural Optimization (MSO) continues to be an area of research interest in engineering optimization. In the present project, the weight optimization of beams and trusses using Displacement based Multilevel Structural Optimization (DMSO), a member of the MSO set of methodologies, is investigated. In the DMSO approach, the optimization task is subdivided into a single system and multiple subsystems level optimizations. The system level optimization minimizes the load unbalance resulting from the use of displacement functions to approximate the structural displacements. The function coefficients are then the design variables. Alternately, the system level optimization can be solved using the displacements themselves as design variables, as was shown in previous research. Both approaches ensure that the calculated loads match the applied loads. In the subsystems level, the weight of the structure is minimized using the element dimensions as design variables. The approach is expected to be very efficient for large structures, since parallel computing can be utilized in the different levels of the problem. In this paper, the method is applied to a one-dimensional beam and a large three-dimensional truss. The beam was tested to study possible simplifications to the system level optimization. In previous research, polynomials were used to approximate the global nodal displacements. The number of coefficients of the polynomials equally matched the number of degrees of freedom of the problem. Here it was desired to see if it is possible to only match a subset of the degrees of freedom in the system level. This would lead to a simplification of the system level, with a resulting increase in overall efficiency. However, the methods tested for this type of system level simplification did not yield positive results. The large truss was utilized to test further improvements in the efficiency of DMSO. In previous work, parallel processing was applied to the

  12. Translating multilevel theory into multilevel research: Challenges and opportunities for understanding the social determinants of psychiatric disorders

    PubMed Central

    Dunn, Erin C.; Masyn, Katherine E.; Yudron, Monica; Jones, Stephanie M.; Subramanian, S.V.

    2014-01-01

    The observation that features of the social environment, including family, school, and neighborhood characteristics, are associated with individual-level outcomes has spurred the development of dozens of multilevel or ecological theoretical frameworks in epidemiology, public health, psychology, and sociology, among other disciplines. Despite the widespread use of such theories in etiological, intervention, and policy studies, challenges remain in bridging multilevel theory and empirical research. This paper set out to synthesize these challenges and provide specific examples of methodological and analytical strategies researchers are using to gain a more nuanced understanding of the social determinants of psychiatric disorders, with a focus on children’s mental health. To accomplish this goal, we begin by describing multilevel theories, defining their core elements, and discussing what these theories suggest is needed in empirical work. In the second part, we outline the main challenges researchers face in translating multilevel theory into research. These challenges are presented for each stage of the research process. In the third section, we describe two methods being used as alternatives to traditional multilevel modeling techniques to better bridge multilevel theory and multilevel research. These are: (1) multilevel factor analysis and multilevel structural equation modeling; and (2) dynamic systems approaches. Through its review of multilevel theory, assessment of existing strategies, and examination of emerging methodologies, this paper offers a framework to evaluate and guide empirical studies on the social determinants of child psychiatric disorders as well as health across the lifecourse. PMID:24469555

  13. Computational modeling and multilevel cancer control interventions.

    PubMed

    Morrissey, Joseph P; Lich, Kristen Hassmiller; Price, Rebecca Anhang; Mandelblatt, Jeanne

    2012-05-01

    This chapter presents an overview of computational modeling as a tool for multilevel cancer care and intervention research. Model-based analyses have been conducted at various "beneath the skin" or biological scales as well as at various "above the skin" or socioecological levels of cancer care delivery. We review the basic elements of computational modeling and illustrate its applications in four cancer control intervention areas: tobacco use, colorectal cancer screening, cervical cancer screening, and racial disparities in access to breast cancer care. Most of these models have examined cancer processes and outcomes at only one or two levels. We suggest ways these models can be expanded to consider interactions involving three or more levels. Looking forward, a number of methodological, structural, and communication barriers must be overcome to create useful computational models of multilevel cancer interventions and population health. PMID:22623597

  14. Multilevel Inverters for Electric Vehicle Applications

    SciTech Connect

    Habetler, T.G.; Peng, F.Z.; Tolbert, L.M.

    1998-10-22

    This paper presents multilevel inverters as an application for all-electric vehicle (EV) and hybrid-electric vehicle (HEV) motor drives. Diode-clamped inverters and cascaded H-bridge inverters, (1) can generate near-sinusoidal voltages with only fundamental frequency switching; (2) have almost no electromagnetic interference (EMI) and common-mode voltage; and (3) make an EV more accessible/safer and open wiring possible for most of an EV'S power system. This paper explores the benefits and discusses control schemes of the cascade inverter for use as an EV motor drive or a parallel HEV drive and the diode-clamped inverter as a series HEV motor drive. Analytical, simulated, and experimental results show the superiority of these multilevel inverters for this new niche.

  15. Load cell

    DOEpatents

    Spletzer, Barry L.

    2001-01-01

    A load cell combines the outputs of a plurality of strain gauges to measure components of an applied load. Combination of strain gauge outputs allows measurement of any of six load components without requiring complex machining or mechanical linkages to isolate load components. An example six axis load cell produces six independent analog outputs which can be combined to determine any one of the six general load components.

  16. Load cell

    DOEpatents

    Spletzer, B.L.

    1998-12-15

    A load cell combines the outputs of a plurality of strain gauges to measure components of an applied load. Combination of strain gauge outputs allows measurement of any of six load components without requiring complex machining or mechanical linkages to isolate load components. An example six axis load cell produces six independent analog outputs, each directly proportional to one of the six general load components. 16 figs.

  17. Load cell

    DOEpatents

    Spletzer, Barry L.

    1998-01-01

    A load cell combines the outputs of a plurality of strain gauges to measure components of an applied load. Combination of strain gauge outputs allows measurement of any of six load components without requiring complex machining or mechanical linkages to isolate load components. An example six axis load cell produces six independent analog outputs, each directly proportional to one of the six general load components.

  18. Multilevel resistive information storage and retrieval

    DOEpatents

    Lohn, Andrew; Mickel, Patrick R.

    2016-08-09

    The present invention relates to resistive random-access memory (RRAM or ReRAM) systems, as well as methods of employing multiple state variables to form degenerate states in such memory systems. The methods herein allow for precise write and read steps to form multiple state variables, and these steps can be performed electrically. Such an approach allows for multilevel, high density memory systems with enhanced information storage capacity and simplified information retrieval.

  19. Automatic Multilevel Parallelization Using OpenMP

    NASA Technical Reports Server (NTRS)

    Jin, Hao-Qiang; Jost, Gabriele; Yan, Jerry; Ayguade, Eduard; Gonzalez, Marc; Martorell, Xavier; Biegel, Bryan (Technical Monitor)

    2002-01-01

    In this paper we describe the extension of the CAPO parallelization support tool to support multilevel parallelism based on OpenMP directives. CAPO generates OpenMP directives with extensions supported by the NanosCompiler to allow for directive nesting and definition of thread groups. We report first results for several benchmark codes and one full application that have been parallelized using our system.

  20. Automatic Multilevel Parallelization Using OpenMP

    NASA Technical Reports Server (NTRS)

    Jin, Hao-Qiang; Jost, Gabriele; Yan, Jerry; Ayguade, Eduard; Gonzalez, Marc; Martorell, Xavier; Biegel, Bryan (Technical Monitor)

    2002-01-01

    In this paper we describe the extension of the CAPO (CAPtools (Computer Aided Parallelization Toolkit) OpenMP) parallelization support tool to support multilevel parallelism based on OpenMP directives. CAPO generates OpenMP directives with extensions supported by the NanosCompiler to allow for directive nesting and definition of thread groups. We report some results for several benchmark codes and one full application that have been parallelized using our system.

  1. On the effectiveness of multilevel selection.

    PubMed

    Goodnight, Charles J

    2016-01-01

    Experimental studies of group selection show that higher levels of selection act on indirect genetic effects, making the response to group and community selection qualitatively different from that of individual selection. This suggests that multilevel selection plays a key role in the evolution of supersocial societies. Experiments showing the effectiveness of community selection indicate that we should consider the possibility that selection among communities may be important in the evolution of supersocial species. PMID:27562604

  2. Multilevel sparse functional principal component analysis.

    PubMed

    Di, Chongzhi; Crainiceanu, Ciprian M; Jank, Wolfgang S

    2014-01-29

    We consider analysis of sparsely sampled multilevel functional data, where the basic observational unit is a function and data have a natural hierarchy of basic units. An example is when functions are recorded at multiple visits for each subject. Multilevel functional principal component analysis (MFPCA; Di et al. 2009) was proposed for such data when functions are densely recorded. Here we consider the case when functions are sparsely sampled and may contain only a few observations per function. We exploit the multilevel structure of covariance operators and achieve data reduction by principal component decompositions at both between and within subject levels. We address inherent methodological differences in the sparse sampling context to: 1) estimate the covariance operators; 2) estimate the functional principal component scores; 3) predict the underlying curves. Through simulations the proposed method is able to discover dominating modes of variations and reconstruct underlying curves well even in sparse settings. Our approach is illustrated by two applications, the Sleep Heart Health Study and eBay auctions. PMID:24872597

  3. Multilevel sparse functional principal component analysis

    PubMed Central

    Di, Chongzhi; Crainiceanu, Ciprian M.; Jank, Wolfgang S.

    2014-01-01

    We consider analysis of sparsely sampled multilevel functional data, where the basic observational unit is a function and data have a natural hierarchy of basic units. An example is when functions are recorded at multiple visits for each subject. Multilevel functional principal component analysis (MFPCA; Di et al. 2009) was proposed for such data when functions are densely recorded. Here we consider the case when functions are sparsely sampled and may contain only a few observations per function. We exploit the multilevel structure of covariance operators and achieve data reduction by principal component decompositions at both between and within subject levels. We address inherent methodological differences in the sparse sampling context to: 1) estimate the covariance operators; 2) estimate the functional principal component scores; 3) predict the underlying curves. Through simulations the proposed method is able to discover dominating modes of variations and reconstruct underlying curves well even in sparse settings. Our approach is illustrated by two applications, the Sleep Heart Health Study and eBay auctions. PMID:24872597

  4. Alternatives to Multilevel Modeling for the Analysis of Clustered Data

    ERIC Educational Resources Information Center

    Huang, Francis L.

    2016-01-01

    Multilevel modeling has grown in use over the years as a way to deal with the nonindependent nature of observations found in clustered data. However, other alternatives to multilevel modeling are available that can account for observations nested within clusters, including the use of Taylor series linearization for variance estimation, the design…

  5. Matching Strategies for Observational Data with Multilevel Structure

    ERIC Educational Resources Information Center

    Steiner, Peter M.

    2011-01-01

    Given the different possibilities of matching in the context of multilevel data and the lack of research on corresponding matching strategies, the author investigates two main research questions. The first research question investigates the advantages and disadvantages of different matching strategies that can be pursued with multilevel data…

  6. A Multilevel Analysis of Parental Discipline and Child Antisocial Behavior

    ERIC Educational Resources Information Center

    Stoolmiller, Mike; Snyder, Jim

    2004-01-01

    We demonstrate graphical and analytical methods for multilevel (2- and 3-level) models using the analysis of observed microsocial interaction between parent-child dyads as an example. We also present multilevel path diagrams and argue that while not as compact as equations, path diagrams may communicate results better to a wider audience. The…

  7. Multilevel Higher-Order Item Response Theory Models

    ERIC Educational Resources Information Center

    Huang, Hung-Yu; Wang, Wen-Chung

    2014-01-01

    In the social sciences, latent traits often have a hierarchical structure, and data can be sampled from multiple levels. Both hierarchical latent traits and multilevel data can occur simultaneously. In this study, we developed a general class of item response theory models to accommodate both hierarchical latent traits and multilevel data. The…

  8. How does psychotherapy work? A case study in multilevel explanation.

    PubMed

    Roache, Rebecca

    2015-01-01

    Multilevel explanations abound in psychiatry. However, formulating useful such explanations is difficult or (some argue) impossible. I point to several ways in which Lane et al. successfully use multilevel explanations to advance understanding of psychotherapeutic effectiveness. I argue that the usefulness of an explanation depends largely on one's purpose, and conclude that this point has been inadequately recognised in psychiatry. PMID:26050687

  9. Suspended Load

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The suspended load of rivers and streams consists of the sediments that are kept in the water column by the upward components of the flow velocity. Suspended load may be divided into cohesive and non-cohesive loads which are primarily discriminated by sediment particle size. Non-cohesive sediment ...

  10. Multilevel converters for large electric drives

    SciTech Connect

    Tolbert, L.M.; Peng, F.Z.

    1997-11-01

    Traditional two-level high frequency pulse width modulation (PWM) inverters for motor drives have several problems associated with their high frequency switching which produces common-mode voltage and high voltage change (dV/dt) rates to the motor windings. Multilevel inverters solve these problems because their devices can switch at a much lower frequency. Two different multilevel topologies are identified for use as a converter for electric drives, a cascade inverter with separate dc sources and a back-to-back diode clamped converter. The cascade inverter is a natural fit for large automotive all electric drives because of the high VA ratings possible and because it uses several levels of dc voltage sources which would be available from batteries or fuel cells. The back to back diode damped converter is ideal where a source of ac voltage is available such as a hybrid electric vehicle. Simulation and experimental results show the superiority of these two converters over PWM based drives.

  11. Multilevel analysis in road safety research.

    PubMed

    Dupont, Emmanuelle; Papadimitriou, Eleonora; Martensen, Heike; Yannis, George

    2013-11-01

    Hierarchical structures in road safety data are receiving increasing attention in the literature and multilevel (ML) models are proposed for appropriately handling the resulting dependences among the observations. However, so far no empirical synthesis exists of the actual added value of ML modelling techniques as compared to other modelling approaches. This paper summarizes the statistical and conceptual background and motivations for multilevel analyses in road safety research. It then provides a review of several ML analyses applied to aggregate and disaggregate (accident) data. In each case, the relevance of ML modelling techniques is assessed by examining whether ML model formulations (i) allow improving the fit of the model to the data, (ii) allow identifying and explaining random variation at specific levels of the hierarchy considered, and (iii) yield different (more correct) conclusions than single-level model formulations with respect to the significance of the parameter estimates. The evidence reviewed offers different conclusions depending on whether the analysis concerns aggregate data or disaggregate data. In the first case, the application of ML analysis techniques appears straightforward and relevant. The studies based on disaggregate accident data, on the other hand, offer mixed findings: computational problems can be encountered, and ML applications are not systematically necessary. The general recommendation concerning disaggregate accident data is to proceed to a preliminary investigation of the necessity of ML analyses and of the additional information to be expected from their application. PMID:23769622

  12. The treatment for multilevel noncontiguous spinal fractures

    PubMed Central

    Lian, Xiao Feng; Hou, Tie Sheng; Yuan, Jian Dong; Jin, Gen Yang; Li, Zhong Hai

    2006-01-01

    We report the outcome of 30 patients with multilevel noncontiguous spinal fractures treated between 2000 and 2005. Ten cases were treated conservatively (group A), eight cases were operated on at only one level (group B), and 12 cases were treated surgically at both levels (group C). All cases were followed up for 14–60 months (mean 32 months). Initial mobilisation with a wheelchair or crutches in group A was 9.2±1.1 weeks, which was significantly longer than groups B and C with 6.8±0.7 weeks and 3.1±0.4 weeks, respectively. Operative time and blood loss in group C were significantly more than group B. The neurological deficit improved in six cases in group A (60%), six in group B (75%) and eight in group C (80%). Correction of kyphotic deformity was significantly superior in groups C and B at the operated level, and increasing deformity occurred in groups A and B at the non-operated level. From the results we believe that three treatment strategies were suitable for multilevel noncontiguous spinal fractures, and individualised treatment should be used in these patients. In the patients treated surgically, the clinical and radiographic outcomes are much better. PMID:17043863

  13. Fault diagnosis method based on FFT-RPCA-SVM for Cascaded-Multilevel Inverter.

    PubMed

    Wang, Tianzhen; Qi, Jie; Xu, Hao; Wang, Yide; Liu, Lei; Gao, Diju

    2016-01-01

    Thanks to reduced switch stress, high quality of load wave, easy packaging and good extensibility, the cascaded H-bridge multilevel inverter is widely used in wind power system. To guarantee stable operation of system, a new fault diagnosis method, based on Fast Fourier Transform (FFT), Relative Principle Component Analysis (RPCA) and Support Vector Machine (SVM), is proposed for H-bridge multilevel inverter. To avoid the influence of load variation on fault diagnosis, the output voltages of the inverter is chosen as the fault characteristic signals. To shorten the time of diagnosis and improve the diagnostic accuracy, the main features of the fault characteristic signals are extracted by FFT. To further reduce the training time of SVM, the feature vector is reduced based on RPCA that can get a lower dimensional feature space. The fault classifier is constructed via SVM. An experimental prototype of the inverter is built to test the proposed method. Compared to other fault diagnosis methods, the experimental results demonstrate the high accuracy and efficiency of the proposed method. PMID:26626623

  14. Direct handling of equality constraints in multilevel optimization

    NASA Technical Reports Server (NTRS)

    Renaud, John E.; Gabriele, Gary A.

    1990-01-01

    In recent years there have been several hierarchic multilevel optimization algorithms proposed and implemented in design studies. Equality constraints are often imposed between levels in these multilevel optimizations to maintain system and subsystem variable continuity. Equality constraints of this nature will be referred to as coupling equality constraints. In many implementation studies these coupling equality constraints have been handled indirectly. This indirect handling has been accomplished using the coupling equality constraints' explicit functional relations to eliminate design variables (generally at the subsystem level), with the resulting optimization taking place in a reduced design space. In one multilevel optimization study where the coupling equality constraints were handled directly, the researchers encountered numerical difficulties which prevented their multilevel optimization from reaching the same minimum found in conventional single level solutions. The researchers did not explain the exact nature of the numerical difficulties other than to associate them with the direct handling of the coupling equality constraints. The coupling equality constraints are handled directly, by employing the Generalized Reduced Gradient (GRG) method as the optimizer within a multilevel linear decomposition scheme based on the Sobieski hierarchic algorithm. Two engineering design examples are solved using this approach. The results show that the direct handling of coupling equality constraints in a multilevel optimization does not introduce any problems when the GRG method is employed as the internal optimizer. The optimums achieved are comparable to those achieved in single level solutions and in multilevel studies where the equality constraints have been handled indirectly.

  15. Multilevel Dynamic Generalized Structured Component Analysis for Brain Connectivity Analysis in Functional Neuroimaging Data.

    PubMed

    Jung, Kwanghee; Takane, Yoshio; Hwang, Heungsun; Woodward, Todd S

    2016-06-01

    We extend dynamic generalized structured component analysis (GSCA) to enhance its data-analytic capability in structural equation modeling of multi-subject time series data. Time series data of multiple subjects are typically hierarchically structured, where time points are nested within subjects who are in turn nested within a group. The proposed approach, named multilevel dynamic GSCA, accommodates the nested structure in time series data. Explicitly taking the nested structure into account, the proposed method allows investigating subject-wise variability of the loadings and path coefficients by looking at the variance estimates of the corresponding random effects, as well as fixed loadings between observed and latent variables and fixed path coefficients between latent variables. We demonstrate the effectiveness of the proposed approach by applying the method to the multi-subject functional neuroimaging data for brain connectivity analysis, where time series data-level measurements are nested within subjects. PMID:25697370

  16. Towards the development of multilevel-multiagent diagnostic aids

    SciTech Connect

    Stratton, R.C.; Jarrell, D.B.

    1991-10-01

    Presented here is our methodology for developing automated aids for diagnosing faults in complex systems. We have designed these aids as multilevel-multiagent diagnostic aids based on principles that should be generally applicable to any complex system. In this methodology, multilevel'' refers to information models described at successful levels of abstraction that are tied together in such a way that reasoning is directed to the appropriate level as determined by the problem solving requirements. The concept of multiagent'' refers to the method of information processing within the multilevel model network; each model in the network is an independent information processor, i.e., an intelligent agent. 19 refs., 15 figs., 9 tabs.

  17. A parallel algorithm for multi-level logic synthesis using the transduction method. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Lim, Chieng-Fai

    1991-01-01

    The Transduction Method has been shown to be a powerful tool in the optimization of multilevel networks. Many tools such as the SYLON synthesis system (X90), (CM89), (LM90) have been developed based on this method. A parallel implementation is presented of SYLON-XTRANS (XM89) on an eight processor Encore Multimax shared memory multiprocessor. It minimizes multilevel networks consisting of simple gates through parallel pruning, gate substitution, gate merging, generalized gate substitution, and gate input reduction. This implementation, called Parallel TRANSduction (PTRANS), also uses partitioning to break large circuits up and performs inter- and intra-partition dynamic load balancing. With this, good speedups and high processor efficiencies are achievable without sacrificing the resulting circuit quality.

  18. Multilevel domain decomposition for electronic structure calculations

    SciTech Connect

    Barrault, M. . E-mail: maxime.barrault@edf.fr; Cances, E. . E-mail: cances@cermics.enpc.fr; Hager, W.W. . E-mail: hager@math.ufl.edu; Le Bris, C. . E-mail: lebris@cermics.enpc.fr

    2007-03-01

    We introduce a new multilevel domain decomposition method (MDD) for electronic structure calculations within semi-empirical and density functional theory (DFT) frameworks. This method iterates between local fine solvers and global coarse solvers, in the spirit of domain decomposition methods. Using this approach, calculations have been successfully performed on several linear polymer chains containing up to 40,000 atoms and 200,000 atomic orbitals. Both the computational cost and the memory requirement scale linearly with the number of atoms. Additional speed-up can easily be obtained by parallelization. We show that this domain decomposition method outperforms the density matrix minimization (DMM) method for poor initial guesses. Our method provides an efficient preconditioner for DMM and other linear scaling methods, variational in nature, such as the orbital minimization (OM) procedure.

  19. Cantilevered multilevel LIGA devices and methods

    DOEpatents

    Morales, Alfredo Martin; Domeier, Linda A.

    2002-01-01

    In the formation of multilevel LIGA microstructures, a preformed sheet of photoresist material, such as polymethylmethacrylate (PMMA) is patterned by exposure through a mask to radiation, such as X-rays, and developed using a developer to remove the exposed photoresist material. A first microstructure is then formed by electroplating metal into the areas from which the photoresist has been removed. Additional levels of microstructure are added to the initial microstructure by covering the first microstructure with a conductive polymer, machining the conductive polymer layer to reveal the surface of the first microstructure, sealing the conductive polymer and surface of the first microstructure with a metal layer, and then forming the second level of structure on top of the first level structure. In such a manner, multiple layers of microstructure can be built up to allow complex cantilevered microstructures to be formed.

  20. Structural optimization by generalized, multilevel decomposition

    NASA Technical Reports Server (NTRS)

    Sobieszczanski-Sobieski, J.; James, B. B.; Riley, M. F.

    1985-01-01

    The developments toward a general multilevel optimization capability and results for a three-level structural optimization are described. The method partitions a structure into a number of substructuring levels where each substructure corresponds to a subsystem in the general case of an engineering system. The method is illustrated by a portal framework that decomposes into individual beams. Each beam is a box that can be further decomposed into stiffened plates. Substructuring for this example spans three different levels: (1) the bottom level of finite elements representing the plates; (2) an intermediate level of beams treated as substructures; and (3) the top level for the assembled structure. The three-level case is now considered to be qualitatively complete.

  1. Evolution of cooperation by multilevel selection.

    PubMed

    Traulsen, Arne; Nowak, Martin A

    2006-07-18

    We propose a minimalist stochastic model of multilevel (or group) selection. A population is subdivided into groups. Individuals interact with other members of the group in an evolutionary game that determines their fitness. Individuals reproduce, and offspring are added to the same group. If a group reaches a certain size, it can split into two. Faster reproducing individuals lead to larger groups that split more often. In our model, higher-level selection emerges as a byproduct of individual reproduction and population structure. We derive a fundamental condition for the evolution of cooperation by group selection: if b/c > 1 + n/m, then group selection favors cooperation. The parameters b and c denote the benefit and cost of the altruistic act, whereas n and m denote the maximum group size and the number of groups. The model can be extended to more than two levels of selection and to include migration. PMID:16829575

  2. Discrete fluorescent saturation regimes in multilevel systems

    NASA Technical Reports Server (NTRS)

    Kastner, S. O.; Bhatia, A. K.

    1988-01-01

    Using models of multilevel atoms, the fluorescent process was examined for the ratio of the photooxidation rate, Pij, to the collisional oxidation rate, Cij, in the pumped resonance transition i-j. It is shown that, in the full range of the parameter Pij/Cij, there exist three distinct regimes (I, II, and III) which may be usefully exploited. These regimes are defined, respectively, by the following conditions: Pij/Cij smaller than about 1; Pij/Cij much greater than 1 and Pij much lower than Cki; and Pij/Cij much greater than 1 and Pij much higher than Cki, where Cki is the collisional rate populating the source level i. The only regime which is characterized by the sensitivity of fluorescent-fluorescent line intensity ratios to Pij is regime I. If regime III is reached, even fluorescent-nonfluorescent line ratios become independent of Pij. The analysis is applied to the resonant photoexcitation of a carbonlike ion.

  3. ADAPTIVE MULTILEVEL SPLITTING IN MOLECULAR DYNAMICS SIMULATIONS*

    PubMed Central

    Aristoff, David; Lelièvre, Tony; Mayne, Christopher G.; Teo, Ivan

    2014-01-01

    Adaptive Multilevel Splitting (AMS) is a replica-based rare event sampling method that has been used successfully in high-dimensional stochastic simulations to identify trajectories across a high potential barrier separating one metastable state from another, and to estimate the probability of observing such a trajectory. An attractive feature of AMS is that, in the limit of a large number of replicas, it remains valid regardless of the choice of reaction coordinate used to characterize the trajectories. Previous studies have shown AMS to be accurate in Monte Carlo simulations. In this study, we extend the application of AMS to molecular dynamics simulations and demonstrate its effectiveness using a simple test system. Our conclusion paves the way for useful applications, such as molecular dynamics calculations of the characteristic time of drug dissociation from a protein target. PMID:26005670

  4. Multi-level coupled cluster theory

    SciTech Connect

    Myhre, Rolf H.; Koch, Henrik; Sánchez de Merás, Alfredo M. J.

    2014-12-14

    We present a general formalism where different levels of coupled cluster theory can be applied to different parts of the molecular system. The system is partitioned into subsystems by Cholesky decomposition of the one-electron Hartree-Fock density matrix. In this way the system can be divided across chemical bonds without discontinuities arising. The coupled cluster wave function is defined in terms of cluster operators for each part and these are determined from a set of coupled equations. The total wave function fulfills the Pauli-principle across all borders and levels of electron correlation. We develop the associated response theory for this multi-level coupled cluster theory and present proof of principle applications. The formalism is an essential tool in order to obtain size-intensive complexity in the calculation of local molecular properties.

  5. Earning potential in multilevel marketing enterprises

    NASA Astrophysics Data System (ADS)

    Legara, Erika Fille; Monterola, Christopher; Juanico, Dranreb Earl; Litong-Palima, Marisciel; Saloma, Caesar

    2008-08-01

    Government regulators and other concerned citizens warily view multilevel marketing enterprises (MLM) because of their close operational resemblance to exploitative pyramid schemes. We analyze two types of MLM network architectures - the unilevel and binary, in terms of growth behavior and earning potential among members. We show that network growth decelerates after reaching a size threshold, contrary to claims of unrestricted growth by MLM recruiters. We have also found that the earning potential in binary MLM’s obey the Pareto “80-20” rule, implying an earning opportunity that is strongly biased against the most recent members. On the other hand, unilevel MLM’s do not exhibit the Pareto earning distribution and earning potential is independent of member position in the network. Our analytical results agree well with field data taken from real-world MLM’s in the Philippines. Our analysis is generally valid and can be applied to other MLM architectures.

  6. Novel multilevel inverter carrier-based PWM method

    SciTech Connect

    Tolbert, L.M.; Habetler, T.G.

    1999-10-01

    The advent of the transformerless multilevel inverter topology has brought forth various pulsewidth modulation (PWM) schemes as a means to control the switching of the active devices in each of the multiple voltage levels in the inverter. An analysis of how existing multilevel carrier-based PWM affects switch utilization for the different levels of a diode-clamped inverter is conducted. Two novel carrier-based multilevel PWM schemes are presented which help to optimize or balance the switch utilization in multilevel inverters. A 10-kW prototype six-level diode-clamped inverter has been built and controlled with the novel PWM strategies proposed in this paper to act as a voltage-source inverter for a motor drive.

  7. Squeezed light from conventionally pumped multi-level lasers

    NASA Technical Reports Server (NTRS)

    Ralph, T. C.; Savage, C. M.

    1992-01-01

    We have calculated the amplitude squeezing in the output of several conventionally pumped multi-level lasers. We present results which show that standard laser models can produce significantly squeezed outputs in certain parameter ranges.

  8. Integrated structure/control law design by multilevel optimization

    NASA Technical Reports Server (NTRS)

    Gilbert, Michael G.; Schmidt, David K.

    1989-01-01

    A new approach to integrated structure/control law design based on multilevel optimization is presented. This new approach is applicable to aircraft and spacecraft and allows for the independent design of the structure and control law. Integration of the designs is achieved through use of an upper level coordination problem formulation within the multilevel optimization framework. The method requires the use of structure and control law design sensitivity information. A general multilevel structure/control law design problem formulation is given, and the use of Linear Quadratic Gaussian (LQG) control law design and design sensitivity methods within the formulation is illustrated. Results of three simple integrated structure/control law design examples are presented. These results show the capability of structure and control law design tradeoffs to improve controlled system performance within the multilevel approach.

  9. Multilevel Atomic Coherent States and Atomic Holomorphic Representation

    NASA Technical Reports Server (NTRS)

    Cao, Chang-Qi; Haake, Fritz

    1996-01-01

    The notion of atomic coherent states is extended to the case of multilevel atom collective. Based on atomic coherent states, a holomorphic representation for atom collective states and operators is defined. An example is given to illustrate its application.

  10. Metal complex modified azo polymers for multilevel organic memories

    NASA Astrophysics Data System (ADS)

    Ma, Yong; Chen, Hong-Xia; Zhou, Feng; Li, Hua; Dong, Huilong; Li, You-Yong; Hu, Zhi-Jun; Xu, Qing-Feng; Lu, Jian-Mei

    2015-04-01

    Multilevel organic memories have attracted considerable interest due to their high capacity of data storage. Despite advances, the search for multilevel memory materials still remains a formidable challenge. Herein, we present a rational design and synthesis of a class of polymers containing an azobenzene-pyridine group (PAzo-py) and its derivatives, for multilevel organic memory storage. In this design, a metal complex (M(Phen)Cl2, M = Cu, Pd) is employed to modify the HOMO-LUMO energy levels of azo polymers, thereby converting the memory state from binary to ternary. More importantly, this approach enables modulating the energy levels of azo polymers by varying the coordination metal ions. This makes the achievement of high performance multilevel memories possible. The ability to tune the bandgap energy of azo polymers provides new exciting opportunities to develop new materials for high-density data storage.Multilevel organic memories have attracted considerable interest due to their high capacity of data storage. Despite advances, the search for multilevel memory materials still remains a formidable challenge. Herein, we present a rational design and synthesis of a class of polymers containing an azobenzene-pyridine group (PAzo-py) and its derivatives, for multilevel organic memory storage. In this design, a metal complex (M(Phen)Cl2, M = Cu, Pd) is employed to modify the HOMO-LUMO energy levels of azo polymers, thereby converting the memory state from binary to ternary. More importantly, this approach enables modulating the energy levels of azo polymers by varying the coordination metal ions. This makes the achievement of high performance multilevel memories possible. The ability to tune the bandgap energy of azo polymers provides new exciting opportunities to develop new materials for high-density data storage. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00871a

  11. Multi-level bandwidth efficient block modulation codes

    NASA Technical Reports Server (NTRS)

    Lin, Shu

    1989-01-01

    The multilevel technique is investigated for combining block coding and modulation. There are four parts. In the first part, a formulation is presented for signal sets on which modulation codes are to be constructed. Distance measures on a signal set are defined and their properties are developed. In the second part, a general formulation is presented for multilevel modulation codes in terms of component codes with appropriate Euclidean distances. The distance properties, Euclidean weight distribution and linear structure of multilevel modulation codes are investigated. In the third part, several specific methods for constructing multilevel block modulation codes with interdependency among component codes are proposed. Given a multilevel block modulation code C with no interdependency among the binary component codes, the proposed methods give a multilevel block modulation code C which has the same rate as C, a minimum squared Euclidean distance not less than that of code C, a trellis diagram with the same number of states as that of C and a smaller number of nearest neighbor codewords than that of C. In the last part, error performance of block modulation codes is analyzed for an AWGN channel based on soft-decision maximum likelihood decoding. Error probabilities of some specific codes are evaluated based on their Euclidean weight distributions and simulation results.

  12. Multilevel psychometric properties of the AHRQ hospital survey on patient safety culture

    PubMed Central

    2010-01-01

    Background The Agency for Healthcare Research and Quality (AHRQ) Hospital Survey on Patient Safety Culture was designed to assess staff views on patient safety culture in hospital settings. The purpose of this study was to examine the multilevel psychometric properties of the survey. Methods Survey data from 331 U.S. hospitals with 2,267 hospital units and 50,513 respondents were analyzed to examine the psychometric properties of the survey's items and composites. Item factor loadings, intraclass correlations (ICCs), design effects, internal consistency reliabilities, and multilevel confirmatory factor analyses (MCFA) were examined as well as intercorrelations among the survey's composites. Results Psychometric analyses confirmed the multilevel nature of the data at the individual, unit and hospital levels of analysis. Results provided overall evidence supporting the 12 dimensions and 42 items included in the AHRQ Hospital Survey on Patient Safety Culture as having acceptable psychometric properties at all levels of analysis, with a few exceptions. The Staffing composite fell slightly below cutoffs in a number of areas, but is conceptually important given its impact on patient safety. In addition, one hospital-level model fit indicator for the Supervisor/Manager Expectations & Actions Promoting Patient Safety composite was low (CFI = .82), but all other psychometrics for this scale were good. Average dimension intercorrelations were moderate at .42 at the individual level, .50 at the unit level, and .56 at the hospital level. Conclusions Psychometric analyses conducted on a very large database of hospitals provided overall support for the patient safety culture dimensions and items included in the AHRQ Hospital Survey on Patient Safety Culture. The survey's items and dimensions overall are psychometrically sound at the individual, unit, and hospital levels of analysis and can be used by researchers and hospitals interested in assessing patient safety culture

  13. Biomechanics of Cervical ‘Skip’ Corpectomy versus Standard Multilevel Corpectomy

    PubMed Central

    Yilmaz, Murat; Yüksel, K. Zafer; Baek, Seungwon; Sawa, Anna G.U.; Dalbayrak, Sedat; Sonntag, Volker K.H.; Crawford, Neil R.

    2012-01-01

    Study Design In vitro biomechanical study of flexibility with finite element simulation to estimate screw stresses. Objective To compare cervical spinal stability after a standard plated three-level corpectomy with stability after a plated three-level “skip” corpectomy where the middle vertebra is left intact (i.e., two one-level corpectomies), and to quantify pullout forces acting on the screws during various loading modes. Summary of Background Data Clinically, three-level cervical plated corpectomy has a high rate of failure, partially because only four contact points affix the plate to the upper and lower intact vertebrae. Leaving the intermediate vertebral body intact for additional fixation points may overcome this problem while still allowing dural sac decompression. Methods Quasistatic nonconstraining torque (maximum 1 Nm) induced flexion, extension, lateral bending, and axial rotation while angular motion was recorded stereophotogrammetrically. Specimens were tested intact and after corpectomy with standard plated and strut-grafted three-level corpectomy (7 specimens) or ‘skip’ corpectomy (7 specimens). Screw stresses were quantified using a validated finite element model of C3–C7 mimicking experimentally tested groups. Skip corpectomy with C5 screws omitted was also simulated. Results Plated skip corpectomy tended to be more stable than plated standard corpectomy, but the difference was not significant. Compared to standard plated corpectomy, plated skip corpectomy reduced peak screw pull-out force during axial rotation (mode of loading of highest peak force) by 15% (4-screw attachment) and 19% (6-screw attachment). Conclusions Skip corpectomy is a good alternative to standard three-level corpectomy to improve stability, especially during lateral bending. Under pure moment loading, the screws of a cervical multilevel plate experience the highest pullout forces during axial rotation. Thus, limiting this movement in patients undergoing plated

  14. Multilevel multitrait-multimethod latent analysis of structurally different and interchangeable raters of school climate.

    PubMed

    Konold, Timothy; Cornell, Dewey

    2015-09-01

    Informant-based systems of assessment are common platforms for measuring a variety of educational and psychological constructs where the use of multiple informants is considered best practice. In many instances, structurally different informant types (e.g., students and teachers) are solicited on the basis of their unique roles with the target of measurement. The use of multiple informants provides an opportunity to evaluate the degree to which the obtained ratings are influenced by the trait of focus and extraneous sources that can be attributed to the rater. Data from a multilevel multitrait-multimethod design in which students (N = 35,565) and teachers (N = 9,112), from 340 middle schools, responded to items measuring 3 dimensions of school climate were evaluated through a multilevel correlated trait-correlated method latent variable model. Results indicated that ratings of school climate obtained by students and teachers demonstrated high levels of convergent validity, and that school-level ratings obtained by students and teachers were equitable in the assessment of teasing and bullying. Student ratings of support and structure yielded somewhat stronger evidence of convergent validity than ratings obtained by teachers as revealed by their respective trait factor loadings. This was explained in part by the higher levels of common method effects that were observed for teachers. PMID:25751606

  15. Analysis of a transformer-less, multi-level DC-DC converter for HVDC operation

    SciTech Connect

    Karady, G.G.; Devarajan, S.

    1998-12-31

    HVDC systems require DC step up and DC step down units. The traditional approach is the application of twelve-pulse thyristor bridges with transformers. The developments of fast switching IGBT devices permit the development of transformer-less, multi-level converters. A multi-level circuit was suggested by Limpaecher. This paper presents a detailed simulation of the proposed circuit together with the analysis of its performance. The converter consists of a set of capacitors, air core inductors and solid state switches arranged in a ladder network. In the step-up mode, the closing of solid state switches resonantly charges the capacitors in parallel through an air-cored inductor. Then solid state switches resonantly charges the capacitors in parallel through an air-cored inductor. Then solid state switches connect the capacitors in series and discharge them through an air-core inductor to the load. In the step-down mode the capacitors are charged in series and discharged in parallel. The circuit has three modes of operation in each cycle: charge, inversion, and discharge. The circuit operation is analyzed in each mode using SPICE simulations. The selection of the components is discussed and output voltage regulation is analyzed. The results show that the proposed circuit promises significant reduction of losses, because of the zero current switching. The investment cost is reduced because of the elimination of transformers.

  16. Multilevel Confirmatory Factor Analysis of a Scale Measuring Interagency Collaboration of Children's Mental Health Agencies.

    PubMed

    Dedrick, Robert F; Greenbaum, Paul E

    2011-03-01

    Multilevel confirmatory factor analysis was used to evaluate the factor structure underlying the 12-item, three-factor Interagency Collaboration Activities Scale (IACS) at the informant level and at the agency level. Results from 378 professionals (104 administrators, 201 service providers, and 73 case managers) from 32 children's mental health service agencies supported a correlated three-factor model at each level and indicated that the item loadings were not significantly (p < .05) different across levels. Reliability estimates of the three factors (Financial and Physical Resource Activities, Program Development and Evaluation Activities, and Collaborative Policy Activities) at the agency level were .81, .60, and .72, respectively, while these estimates were .79, .82, and .85 at the individual level. These multilevel results provide support for the construct validity of the scores from the IACS. When the IACS was examined in relation to level-1 and level-2 covariates, results showed that participants' characteristics (i.e., age, job role, gender, educational level, and number of months employed) and agency characteristics (i.e., state location and number of employees) were not significantly (p > .05) related to levels of interagency collaboration. PMID:21528103

  17. Multilevel Cross-dependent Binary Longitudinal Data

    PubMed Central

    Staicu, Ana-Maria; Carroll, Raymond J.

    2013-01-01

    We provide insights into new methodology for the analysis of multilevel binary data observed longitudinally, when the repeated longitudinal measurements are correlated. The proposed model is logistic functional regression conditioned on three latent processes describing the within- and between-variability, and describing the cross-dependence of the repeated longitudinal measurements. We estimate the model components without employing mixed-effects modeling but assuming an approximation to the logistic link function. The primary objectives of this paper are to highlight the challenges in the estimation of the model components, to compare two approximations to the logistic regression function, linear and exponential, and to discuss their advantages and limitations. The linear approximation is computationally efficient whereas the exponential approximation applies for rare events functional data. Our methods are inspired by and applied to a scientific experiment on spectral backscatter from long range infrared light detection and ranging (LIDAR) data. The models are general and relevant to many new binary functional data sets, with or without dependence between repeated functional measurements. PMID:24131242

  18. Gaussian translation operator in a multilevel scheme

    NASA Astrophysics Data System (ADS)

    Hansen, Thorkild B.; Borries, Oscar

    2015-08-01

    A multilevel computation scheme for time-harmonic fields in three dimensions will be formulated with a new Gaussian translation operator that decays exponentially outside a circular cone centered on the line connecting the source and observation groups. This Gaussian translation operator is directional and diagonal with its sharpness determined by a beam parameter. When the beam parameter is set to zero, the Gaussian translation operator reduces to the standard fast multipole method translation operator. The directionality of the Gaussian translation operator makes it possible to reduce the number of plane waves required to achieve a given accuracy. The sampling rate can be determined straightforwardly to achieve any desired accuracy. The use of the computation scheme will be illustrated through a near-field scanning problem where the far-field pattern of a source is determined from near-field measurements with a known probe. Here the Gaussian translation operator improves the condition number of the matrix equation that determines the far-field pattern. The Gaussian translation operator can also be used when the probe pattern is known only in one hemisphere, as is common in practice. Also, the Gaussian translation operator will be used to solve the scattering problem of the perfectly conducting sphere.

  19. Multilevel Monte Carlo simulation of Coulomb collisions

    DOE PAGESBeta

    Rosin, M. S.; Ricketson, L. F.; Dimits, A. M.; Caflisch, R. E.; Cohen, B. I.

    2014-05-29

    We present a new, for plasma physics, highly efficient multilevel Monte Carlo numerical method for simulating Coulomb collisions. The method separates and optimally minimizes the finite-timestep and finite-sampling errors inherent in the Langevin representation of the Landau–Fokker–Planck equation. It does so by combining multiple solutions to the underlying equations with varying numbers of timesteps. For a desired level of accuracy ε , the computational cost of the method is O(ε–2) or (ε–2(lnε)2), depending on the underlying discretization, Milstein or Euler–Maruyama respectively. This is to be contrasted with a cost of O(ε–3) for direct simulation Monte Carlo or binary collision methods.more » We successfully demonstrate the method with a classic beam diffusion test case in 2D, making use of the Lévy area approximation for the correlated Milstein cross terms, and generating a computational saving of a factor of 100 for ε=10–5. Lastly, we discuss the importance of the method for problems in which collisions constitute the computational rate limiting step, and its limitations.« less

  20. Multilevel Monte Carlo simulation of Coulomb collisions

    SciTech Connect

    Rosin, M. S.; Ricketson, L. F.; Dimits, A. M.; Caflisch, R. E.; Cohen, B. I.

    2014-05-29

    We present a new, for plasma physics, highly efficient multilevel Monte Carlo numerical method for simulating Coulomb collisions. The method separates and optimally minimizes the finite-timestep and finite-sampling errors inherent in the Langevin representation of the Landau–Fokker–Planck equation. It does so by combining multiple solutions to the underlying equations with varying numbers of timesteps. For a desired level of accuracy ε , the computational cost of the method is O(ε–2) or (ε–2(lnε)2), depending on the underlying discretization, Milstein or Euler–Maruyama respectively. This is to be contrasted with a cost of O(ε–3) for direct simulation Monte Carlo or binary collision methods. We successfully demonstrate the method with a classic beam diffusion test case in 2D, making use of the Lévy area approximation for the correlated Milstein cross terms, and generating a computational saving of a factor of 100 for ε=10–5. Lastly, we discuss the importance of the method for problems in which collisions constitute the computational rate limiting step, and its limitations.

  1. Multilevel relaxation phenomena and population trapping

    SciTech Connect

    Hioe, F.T.

    1991-11-01

    This final report summarizes the main results of our work supported by DOE since 1982. A list of 45 publications supported by this DOE Grant is attached at the end of this report. The use and exploitation of the SU(N) dynamic symmetry to the study of the dynamics of laser-atom interaction was the starting point of our research work under this DOE Grant, and is our most original contribution to the field of quantum electrodynamics. Many results of general and special interests have been derived and developed from this starting point and the following is a summary of them: (1) We have introduced a set of simple relations based on the principle of unitary invariance which has proved to be useful for the study of the dynamics of a quantum system involving coupling. (2) We have found various specific conditions under which (a) we may have trapped population, or (b) we may send laser pulses through a multilevel atomic medium without attenuation. (3) We have found a remarkably efficient method for optimal state selective multiphoton population transfer, that employs two or more spatially overlapping lasers arranged in an unconventional sequence which we called counterintuitive''. A recent suggestion by Profs. P. Marte, P. Zoller and J.L. Hall to use this counterintuitive method for atomic beam deflections promises to make this remarkably effective procedure to become an important method in atomic interferometry.

  2. Experiments in encoding multilevel images as quadtrees

    NASA Technical Reports Server (NTRS)

    Lansing, Donald L.

    1987-01-01

    Image storage requirements for several encoding methods are investigated and the use of quadtrees with multigray level or multicolor images are explored. The results of encoding a variety of images having up to 256 gray levels using three schemes (full raster, runlength and quadtree) are presented. Although there is considerable literature on the use of quadtrees to store and manipulate binary images, their application to multilevel images is relatively undeveloped. The potential advantage of quadtree encoding is that an entire area with a uniform gray level may be encoded as a unit. A pointerless quadtree encoding scheme is described. Data are presented on the size of the quadtree required to encode selected images and on the relative storage requirements of the three encoding schemes. A segmentation scheme based on the statistical variation of gray levels within a quadtree quadrant is described. This parametric scheme may be used to control the storage required by an encoded image and to preprocess a scene for feature identification. Several sets of black and white and pseudocolor images obtained by varying the segmentation parameter are shown.

  3. Analysis of biomedical data with multilevel glyphs

    PubMed Central

    2014-01-01

    Background This paper presents multilevel data glyphs optimized for the interactive knowledge discovery and visualization of large biomedical data sets. Data glyphs are three- dimensional objects defined by multiple levels of geometric descriptions (levels of detail) combined with a mapping of data attributes to graphical elements and methods, which specify their spatial position. Methods In the data mapping phase, which is done by a biomedical expert, meta information about the data attributes (scale, number of distinct values) are compared with the visual capabilities of the graphical elements in order to give a feedback to the user about the correctness of the variable mapping. The spatial arrangement of glyphs is done in a dimetric view, which leads to high data density, a simplified 3D navigation and avoids perspective distortion. Results We show the usage of data glyphs in the disease analyser a visual analytics application for personalized medicine and provide an outlook to a biomedical web visualization scenario. Conclusions Data glyphs can be successfully applied in the disease analyser for the analysis of big medical data sets. Especially the automatic validation of the data mapping, selection of subgroups within histograms and the visual comparison of the value distributions were seen by experts as an important functionality. PMID:25079119

  4. The genetical theory of multilevel selection

    PubMed Central

    Gardner, A

    2015-01-01

    The theory of multilevel selection (MLS) is beset with conceptual difficulties. Although it is widely agreed that covariance between group trait and group fitness may arise in the natural world and drive a response to ‘group selection’, ambiguity exists over the precise meaning of group trait and group fitness and as to whether group selection should be defined according to changes in frequencies of different types of individual or different types of group. Moreover, the theory of MLS has failed to properly engage with the problem of class structure, which greatly limits its empirical application to, for example, social insects whose colonies are structured into separate age, sex, caste and ploidy classes. Here, I develop a genetical theory of MLS, to address these problems. I show that taking a genetical approach facilitates a decomposition of group-level traits – including reproductive success – into the separate contributions made by each constituent individual, even in the context of so-called emergence. However, I uncover a novel problem with the group-oriented approach: in many scenarios, it may not be possible to express a meaningful covariance between trait and fitness at the level of the social group, because the group's constituents belong to separate, irreconcilable classes. PMID:25475922

  5. Dispersion retrieval from multi-level ultra-deep reactive-ion-etched microstructures for terahertz slow-wave circuits

    SciTech Connect

    Baik, Chan-Wook Young Ahn, Ho; Kim, Yongsung; Lee, Jooho; Hong, Seogwoo; Hee Choi, Jun; Kim, Sunil; Hun Lee, Sang; Min Kim, Jong; Hwang, Sungwoo; Yeon Jun, So; Yu, SeGi; Lawrence Ives, R.

    2014-01-13

    A multi-level microstructure is proposed for terahertz slow-wave circuits, with dispersion relation retrieved by scattering parameter measurements. The measured return loss shows strong resonances above the cutoff with negligible phase shifts compared with finite element analysis. Splitting the circuit into multi levels enables a low aspect ratio configuration that alleviates the loading effect of deep-reactive-ion etching on silicon wafers. This makes it easier to achieve flat-etched bottom and smooth sidewall profiles. The dispersion retrieved from the measurement, therefore, corresponds well to the theoretical estimation. The result provides a straightforward way to the precise determination of dispersions in terahertz vacuum electronics.

  6. LOADING DEVICE

    DOEpatents

    Ohlinger, L.A.

    1958-10-01

    A device is presented for loading or charging bodies of fissionable material into a reactor. This device consists of a car, mounted on tracks, into which the fissionable materials may be placed at a remote area, transported to the reactor, and inserted without danger to the operating personnel. The car has mounted on it a heavily shielded magazine for holding a number of the radioactive bodies. The magazine is of a U-shaped configuration and is inclined to the horizontal plane, with a cap covering the elevated open end, and a remotely operated plunger at the lower, closed end. After the fissionable bodies are loaded in the magazine and transported to the reactor, the plunger inserts the body at the lower end of the magazine into the reactor, then is withdrawn, thereby allowing gravity to roll the remaining bodies into position for successive loading in a similar manner.

  7. Multilevel Workflow System in the ATLAS Experiment

    NASA Astrophysics Data System (ADS)

    Borodin, M.; De, K.; Garcia Navarro, J.; Golubkov, D.; Klimentov, A.; Maeno, T.; Vaniachine, A.; ATLAS Collaboration

    2015-05-01

    The ATLAS experiment is scaling up Big Data processing for the next LHC run using a multilevel workflow system comprised of many layers. In Big Data processing ATLAS deals with datasets, not individual files. Similarly a task (comprised of many jobs) has become a unit of the ATLAS workflow in distributed computing, with about 0.8M tasks processed per year. In order to manage the diversity of LHC physics (exceeding 35K physics samples per year), the individual data processing tasks are organized into workflows. For example, the Monte Carlo workflow is composed of many steps: generate or configure hard-processes, hadronize signal and minimum-bias (pileup) events, simulate energy deposition in the ATLAS detector, digitize electronics response, simulate triggers, reconstruct data, convert the reconstructed data into ROOT ntuples for physics analysis, etc. Outputs are merged and/or filtered as necessary to optimize the chain. The bi-level workflow manager - ProdSys2 - generates actual workflow tasks and their jobs are executed across more than a hundred distributed computing sites by PanDA - the ATLAS job-level workload management system. On the outer level, the Database Engine for Tasks (DEfT) empowers production managers with templated workflow definitions. On the next level, the Job Execution and Definition Interface (JEDI) is integrated with PanDA to provide dynamic job definition tailored to the sites capabilities. We report on scaling up the production system to accommodate a growing number of requirements from main ATLAS areas: Trigger, Physics and Data Preparation.

  8. Multilevel summation method for electrostatic force evaluation.

    PubMed

    Hardy, David J; Wu, Zhe; Phillips, James C; Stone, John E; Skeel, Robert D; Schulten, Klaus

    2015-02-10

    The multilevel summation method (MSM) offers an efficient algorithm utilizing convolution for evaluating long-range forces arising in molecular dynamics simulations. Shifting the balance of computation and communication, MSM provides key advantages over the ubiquitous particle–mesh Ewald (PME) method, offering better scaling on parallel computers and permitting more modeling flexibility, with support for periodic systems as does PME but also for semiperiodic and nonperiodic systems. The version of MSM available in the simulation program NAMD is described, and its performance and accuracy are compared with the PME method. The accuracy feasible for MSM in practical applications reproduces PME results for water property calculations of density, diffusion constant, dielectric constant, surface tension, radial distribution function, and distance-dependent Kirkwood factor, even though the numerical accuracy of PME is higher than that of MSM. Excellent agreement between MSM and PME is found also for interface potentials of air–water and membrane–water interfaces, where long-range Coulombic interactions are crucial. Applications demonstrate also the suitability of MSM for systems with semiperiodic and nonperiodic boundaries. For this purpose, simulations have been performed with periodic boundaries along directions parallel to a membrane surface but not along the surface normal, yielding membrane pore formation induced by an imbalance of charge across the membrane. Using a similar semiperiodic boundary condition, ion conduction through a graphene nanopore driven by an ion gradient has been simulated. Furthermore, proteins have been simulated inside a single spherical water droplet. Finally, parallel scalability results show the ability of MSM to outperform PME when scaling a system of modest size (less than 100 K atoms) to over a thousand processors, demonstrating the suitability of MSM for large-scale parallel simulation. PMID:25691833

  9. A robust multilevel simultaneous eigenvalue solver

    NASA Technical Reports Server (NTRS)

    Costiner, Sorin; Taasan, Shlomo

    1993-01-01

    Multilevel (ML) algorithms for eigenvalue problems are often faced with several types of difficulties such as: the mixing of approximated eigenvectors by the solution process, the approximation of incomplete clusters of eigenvectors, the poor representation of solution on coarse levels, and the existence of close or equal eigenvalues. Algorithms that do not treat appropriately these difficulties usually fail, or their performance degrades when facing them. These issues motivated the development of a robust adaptive ML algorithm which treats these difficulties, for the calculation of a few eigenvectors and their corresponding eigenvalues. The main techniques used in the new algorithm include: the adaptive completion and separation of the relevant clusters on different levels, the simultaneous treatment of solutions within each cluster, and the robustness tests which monitor the algorithm's efficiency and convergence. The eigenvectors' separation efficiency is based on a new ML projection technique generalizing the Rayleigh Ritz projection, combined with a technique, the backrotations. These separation techniques, when combined with an FMG formulation, in many cases lead to algorithms of O(qN) complexity, for q eigenvectors of size N on the finest level. Previously developed ML algorithms are less focused on the mentioned difficulties. Moreover, algorithms which employ fine level separation techniques are of O(q(sub 2)N) complexity and usually do not overcome all these difficulties. Computational examples are presented where Schrodinger type eigenvalue problems in 2-D and 3-D, having equal and closely clustered eigenvalues, are solved with the efficiency of the Poisson multigrid solver. A second order approximation is obtained in O(qN) work, where the total computational work is equivalent to only a few fine level relaxations per eigenvector.

  10. Multilevel Summation Method for Electrostatic Force Evaluation

    PubMed Central

    2015-01-01

    The multilevel summation method (MSM) offers an efficient algorithm utilizing convolution for evaluating long-range forces arising in molecular dynamics simulations. Shifting the balance of computation and communication, MSM provides key advantages over the ubiquitous particle–mesh Ewald (PME) method, offering better scaling on parallel computers and permitting more modeling flexibility, with support for periodic systems as does PME but also for semiperiodic and nonperiodic systems. The version of MSM available in the simulation program NAMD is described, and its performance and accuracy are compared with the PME method. The accuracy feasible for MSM in practical applications reproduces PME results for water property calculations of density, diffusion constant, dielectric constant, surface tension, radial distribution function, and distance-dependent Kirkwood factor, even though the numerical accuracy of PME is higher than that of MSM. Excellent agreement between MSM and PME is found also for interface potentials of air–water and membrane–water interfaces, where long-range Coulombic interactions are crucial. Applications demonstrate also the suitability of MSM for systems with semiperiodic and nonperiodic boundaries. For this purpose, simulations have been performed with periodic boundaries along directions parallel to a membrane surface but not along the surface normal, yielding membrane pore formation induced by an imbalance of charge across the membrane. Using a similar semiperiodic boundary condition, ion conduction through a graphene nanopore driven by an ion gradient has been simulated. Furthermore, proteins have been simulated inside a single spherical water droplet. Finally, parallel scalability results show the ability of MSM to outperform PME when scaling a system of modest size (less than 100 K atoms) to over a thousand processors, demonstrating the suitability of MSM for large-scale parallel simulation. PMID:25691833

  11. Multilevel animal societies can emerge from cultural transmission.

    PubMed

    Cantor, Maurício; Shoemaker, Lauren G; Cabral, Reniel B; Flores, César O; Varga, Melinda; Whitehead, Hal

    2015-01-01

    Multilevel societies, containing hierarchically nested social levels, are remarkable social structures whose origins are unclear. The social relationships of sperm whales are organized in a multilevel society with an upper level composed of clans of individuals communicating using similar patterns of clicks (codas). Using agent-based models informed by an 18-year empirical study, we show that clans are unlikely products of stochastic processes (genetic or cultural drift) but likely originate from cultural transmission via biased social learning of codas. Distinct clusters of individuals with similar acoustic repertoires, mirroring the empirical clans, emerge when whales learn preferentially the most common codas (conformism) from behaviourally similar individuals (homophily). Cultural transmission seems key in the partitioning of sperm whales into sympatric clans. These findings suggest that processes similar to those that generate complex human cultures could not only be at play in non-human societies but also create multilevel social structures in the wild. PMID:26348688

  12. Parametric Multi-Level Tiling of Imperfectly Nested Loops

    SciTech Connect

    Hartono, Albert; Baskaran, Muthu M.; Bastoul, Cedric; Cohen, Albert; Krishnamoorthy, Sriram; Norris, Boyana; Ramanujam, J.; Sadayappan, Ponnuswamy

    2009-05-18

    Tiling is a critical loop transformation for generating high-performance code on modern architectures. Efficient generation of multilevel tiled code is essential to exploit several levels of parallelism and/or to maximize data reuse in deep memory hierarchies. Tiled loops with parameterized tile sizes (not compile time constants) facilitate runtime feedback and dynamic optimizations used in iterative compilation and automatic tuning. The existing parametric multilevel tiling approach has focused on transformation for perfectly nested loops, where all assignment statements are contained inside the innermost loop of a loop nest. Previous solutions to tiling for imperfect loop nests are limited to the case where tile sizes are fixed. In this paper, we present an approach to parameterized multilevel tiling for imperfectly nested loops. Our tiling algorithm generates loops that iterate over full rectangular tiles that are amenable for potential compiler optimizations such as register tiling. Experimental results using a number of computational benchmarks demonstrate the effectiveness of our tiling approach.

  13. A multilevel memetic algorithm for large SAT-encoded problems.

    PubMed

    Bouhmala, Noureddine

    2012-01-01

    Many researchers have focused on the satisfiability problem and on many of its variants due to its applicability in many areas of artificial intelligence. This NP-complete problem refers to the task of finding a satisfying assignment that makes a Boolean expression evaluate to True. In this work, we introduce a memetic algorithm that makes use of the multilevel paradigm. The multilevel paradigm refers to the process of dividing large and difficult problems into smaller ones, which are hopefully much easier to solve, and then work backward toward the solution of the original problem, using a solution from a previous level as a starting solution at the next level. Results comparing the memetic with and without the multilevel paradigm are presented using problem instances drawn from real industrial hardware designs. PMID:22540191

  14. Multilevel animal societies can emerge from cultural transmission

    PubMed Central

    Cantor, Maurício; Shoemaker, Lauren G.; Cabral, Reniel B.; Flores, César O.; Varga, Melinda; Whitehead, Hal

    2015-01-01

    Multilevel societies, containing hierarchically nested social levels, are remarkable social structures whose origins are unclear. The social relationships of sperm whales are organized in a multilevel society with an upper level composed of clans of individuals communicating using similar patterns of clicks (codas). Using agent-based models informed by an 18-year empirical study, we show that clans are unlikely products of stochastic processes (genetic or cultural drift) but likely originate from cultural transmission via biased social learning of codas. Distinct clusters of individuals with similar acoustic repertoires, mirroring the empirical clans, emerge when whales learn preferentially the most common codas (conformism) from behaviourally similar individuals (homophily). Cultural transmission seems key in the partitioning of sperm whales into sympatric clans. These findings suggest that processes similar to those that generate complex human cultures could not only be at play in non-human societies but also create multilevel social structures in the wild. PMID:26348688

  15. Multi-level Hierarchical Poly Tree computer architectures

    NASA Technical Reports Server (NTRS)

    Padovan, Joe; Gute, Doug

    1990-01-01

    Based on the concept of hierarchical substructuring, this paper develops an optimal multi-level Hierarchical Poly Tree (HPT) parallel computer architecture scheme which is applicable to the solution of finite element and difference simulations. Emphasis is given to minimizing computational effort, in-core/out-of-core memory requirements, and the data transfer between processors. In addition, a simplified communications network that reduces the number of I/O channels between processors is presented. HPT configurations that yield optimal superlinearities are also demonstrated. Moreover, to generalize the scope of applicability, special attention is given to developing: (1) multi-level reduction trees which provide an orderly/optimal procedure by which model densification/simplification can be achieved, as well as (2) methodologies enabling processor grading that yields architectures with varying types of multi-level granularity.

  16. The Effect of Perceived Instructional Effectiveness on Student Loyalty: A Multilevel Structural Equation Model

    ERIC Educational Resources Information Center

    Simsek, Gulhayat Golbasi; Noyan, Fatma

    2009-01-01

    Social sciences research often entails the analysis of data with a multilevel structure. An example of multilevel data is containing measurement on university students nested within instructors. This paper concentrates on multilevel analysis of structural equation modeling with educational data. Data used in this study were gathered from 17647…

  17. Multilevel Modeling: Applications to Research on the Assessment of Student Learning, Engagement, and Developmental Outcomes

    ERIC Educational Resources Information Center

    Chen, Pu-Shih Daniel; Cragg, Kristina

    2012-01-01

    Understanding the suitability of multilevel modeling in the context of institutional research (IR) may ease the doubts of some IR professionals. However, the need for training on how to conduct and report multilevel modeling analysis remains. A major roadblock hindering the proliferation of multilevel modeling in IR is the perception that…

  18. Multilevel SEM Strategies for Evaluating Mediation in Three-Level Data

    ERIC Educational Resources Information Center

    Preacher, Kristopher J.

    2011-01-01

    Strategies for modeling mediation effects in multilevel data have proliferated over the past decade, keeping pace with the demands of applied research. Approaches for testing mediation hypotheses with 2-level clustered data were first proposed using multilevel modeling (MLM) and subsequently using multilevel structural equation modeling (MSEM) to…

  19. A Multilevel Algorithm for the Solution of Second Order Elliptic Differential Equations on Sparse Grids

    NASA Technical Reports Server (NTRS)

    Pflaum, Christoph

    1996-01-01

    A multilevel algorithm is presented that solves general second order elliptic partial differential equations on adaptive sparse grids. The multilevel algorithm consists of several V-cycles. Suitable discretizations provide that the discrete equation system can be solved in an efficient way. Numerical experiments show a convergence rate of order Omicron(1) for the multilevel algorithm.

  20. Carbohydrate Loading.

    ERIC Educational Resources Information Center

    Csernus, Marilyn

    Carbohydrate loading is a frequently used technique to improve performance by altering an athlete's diet. The objective is to increase glycogen stored in muscles for use in prolonged strenuous exercise. For two to three days, the athlete consumes a diet that is low in carbohydrates and high in fat and protein while continuing to exercise and…

  1. Element Agglomeration Algebraic Multilevel Monte-Carlo Library

    SciTech Connect

    2015-02-19

    ElagMC is a parallel C++ library for Multilevel Monte Carlo simulations with algebraically constructed coarse spaces. ElagMC enables Multilevel variance reduction techniques in the context of general unstructured meshes by using the specialized element-based agglomeration techniques implemented in ELAG (the Element-Agglomeration Algebraic Multigrid and Upscaling Library developed by U. Villa and P. Vassilevski and currently under review for public release). The ElabMC library can support different type of deterministic problems, including mixed finite element discretizations of subsurface flow problems.

  2. Element Agglomeration Algebraic Multilevel Monte-Carlo Library

    Energy Science and Technology Software Center (ESTSC)

    2015-02-19

    ElagMC is a parallel C++ library for Multilevel Monte Carlo simulations with algebraically constructed coarse spaces. ElagMC enables Multilevel variance reduction techniques in the context of general unstructured meshes by using the specialized element-based agglomeration techniques implemented in ELAG (the Element-Agglomeration Algebraic Multigrid and Upscaling Library developed by U. Villa and P. Vassilevski and currently under review for public release). The ElabMC library can support different type of deterministic problems, including mixed finite element discretizationsmore » of subsurface flow problems.« less

  3. Unconventional Coding Technique Applied to Multi-Level Polarization Modulation

    NASA Astrophysics Data System (ADS)

    Rutigliano, G. G.; Betti, S.; Perrone, P.

    2016-05-01

    A new technique is proposed to improve information confidentiality in optical-fiber communications without bandwidth consumption. A pseudorandom vectorial sequence was generated by a dynamic system algorithm and used to codify a multi-level polarization modulation based on the Stokes vector. Optical-fiber birefringence, usually considered as a disturbance, was exploited to obfuscate the signal transmission. At the receiver end, the same pseudorandom sequence was generated and used to decode the multi-level polarization modulated signal. The proposed scheme, working at the physical layer, provides strong information security without introducing complex processing and thus latency.

  4. Dynamic load balancing data centric storage for wireless sensor networks.

    PubMed

    Song, Seokil; Bok, Kyoungsoo; Kwak, Yun Sik; Goo, Bongeun; Kwak, Youngsik; Ko, Daesik

    2010-01-01

    In this paper, a new data centric storage that is dynamically adapted to the work load changes is proposed. The proposed data centric storage distributes the load of hot spot areas to neighboring sensor nodes by using a multilevel grid technique. The proposed method is also able to use existing routing protocols such as GPSR (Greedy Perimeter Stateless Routing) with small changes. Through simulation, the proposed method enhances the lifetime of sensor networks over one of the state-of-the-art data centric storages. We implement the proposed method based on an operating system for sensor networks, and evaluate the performance through running based on a simulation tool. PMID:22163472

  5. LOADED WAVEGUIDES

    DOEpatents

    Mullett, L.B.; Loach, B.G.; Adams, G.L.

    1958-06-24

    >Loaded waveguides are described for the propagation of electromagnetic waves with reduced phase velocities. A rectangular waveguide is dimensioned so as to cut-off the simple H/sub 01/ mode at the operating frequency. The waveguide is capacitance loaded, so as to reduce the phase velocity of the transmitted wave, by connecting an electrical conductor between directly opposite points in the major median plane on the narrower pair of waveguide walls. This conductor may take a corrugated shape or be an aperature member, the important factor being that the electrical length of the conductor is greater than one-half wavelength at the operating frequency. Prepared for the Second U.N. International ConferThe importance of nuclear standards is duscussed. A brief review of the international callaboration in this field is given. The proposal is made to let the International Organization for Standardization (ISO) coordinate the efforts from other groups. (W.D.M.)

  6. The Pitfalls of Ignoring Multilevel Design in National Datasets.

    ERIC Educational Resources Information Center

    Roberts, J. Kyle

    This paper examines the differences between multilevel modeling and weighted ordinary least squares (OLS) regression for analyzing data from the National Educational Longitudinal Study 1988 (NELS:88). The final sample consisted of 718 students in 298 schools. Eighteen variables from the NELS:88 dataset were used, with the dependent variable being…

  7. Multiple Imputation of Multilevel Missing Data-Rigor versus Simplicity

    ERIC Educational Resources Information Center

    Drechsler, Jörg

    2015-01-01

    Multiple imputation is widely accepted as the method of choice to address item-nonresponse in surveys. However, research on imputation strategies for the hierarchical structures that are typically found in the data in educational contexts is still limited. While a multilevel imputation model should be preferred from a theoretical point of view if…

  8. Multilevel Mediation Modeling in Group-Based Intervention Studies.

    ERIC Educational Resources Information Center

    Krull, Jennifer L.; MacKinnon, David P.

    1999-01-01

    Proposes and evaluates a method to test for mediation in multilevel data sets formed when an intervention administered to groups is designed to produce change in individual mediator and outcome variables. Applies the method to the ATLAS intervention designed to decrease steroid use among high school football players. (SLD)

  9. Attachment, Autonomy, and Emotional Reliance: A Multilevel Model

    ERIC Educational Resources Information Center

    Lynch, Martin F.

    2013-01-01

    This article reports a test of a multilevel model investigating how attachment security and autonomy contribute to emotional reliance, or the willingness to seek interpersonal support. Participants ("N" = 247) completed online measures of attachment, autonomy, emotional reliance, and vitality with respect to several everyday…

  10. School Climate and Psychosomatic Health: A Multilevel Analysis

    ERIC Educational Resources Information Center

    Modin, Bitte; Ostberg, Viveca

    2009-01-01

    This study examined the importance of aspects of the school climate for adolescents' psychosomatic health using multilevel modelling. Analyses were based on 18,571 ninth-grade students distributed over 1,026 classes and 284 schools in the greater Stockholm area in 2004 and 2006. Both individual- and contextual-level associations between aspects of…

  11. Examining Elementary Social Studies Marginalization: A Multilevel Model

    ERIC Educational Resources Information Center

    Fitchett, Paul G.; Heafner, Tina L.; Lambert, Richard G.

    2014-01-01

    Utilizing data from the National Center for Education Statistics Schools and Staffing Survey (SASS), a multilevel model (Hierarchical Linear Model) was developed to examine the association of teacher/classroom and state level indicators on reported elementary social studies instructional time. Findings indicated that state testing policy was a…

  12. Service Learning: An Example of Multilevel School Social Work Practice

    ERIC Educational Resources Information Center

    McKay, Cassandra; Johnson, Annette

    2010-01-01

    School social work interventions that address social and emotional learning are often confined to micro-level practice. Yet the social work profession thrives on multilevel practice in all settings (micro, as well as macro). School social workers can play a pivotal role in engaging youth to become prosocial participants of their school and…

  13. Hierarchical Data Structures, Institutional Research, and Multilevel Modeling

    ERIC Educational Resources Information Center

    O'Connell, Ann A.; Reed, Sandra J.

    2012-01-01

    Multilevel modeling (MLM), also referred to as hierarchical linear modeling (HLM) or mixed models, provides a powerful analytical framework through which to study colleges and universities and their impact on students. Due to the natural hierarchical structure of data obtained from students or faculty in colleges and universities, MLM offers many…

  14. Handling Correlations between Covariates and Random Slopes in Multilevel Models

    ERIC Educational Resources Information Center

    Bates, Michael David; Castellano, Katherine E.; Rabe-Hesketh, Sophia; Skrondal, Anders

    2014-01-01

    This article discusses estimation of multilevel/hierarchical linear models that include cluster-level random intercepts and random slopes. Viewing the models as structural, the random intercepts and slopes represent the effects of omitted cluster-level covariates that may be correlated with included covariates. The resulting correlations between…

  15. Concorde and Discord: The Art of Multilevel Modelling

    ERIC Educational Resources Information Center

    Hutchison, Dougal; Schagen, Ian

    2008-01-01

    A recent issue of "International Journal of Research & Methods in Education" (IJRME) contained a challenging article by Stephen Gorard ["The Dubious Benefits of Multi-Level Modelling," "International Journal of Research & Method in Education," Vol. 30 (2), p221-236 (2007)] in which he attacks aspects of current practice in statistical modelling,…

  16. Smart RTI: A Next-Generation Approach to Multilevel Prevention

    ERIC Educational Resources Information Center

    Fuchs, Douglas; Fuchs, Lynn S.; Compton, Donald L.

    2012-01-01

    During the past decade, responsiveness to intervention (RTI) has become popular among many practitioners as a means of transforming schooling into a multilevel prevention system. Popularity aside, its successful implementation requires ambitious intent, a comprehensive structure, and coordinated service delivery. An effective RTI also depends on…

  17. New multi-level codes over GF(q)

    NASA Technical Reports Server (NTRS)

    Wu, Jiantian; Costello, Daniel J., Jr.

    1990-01-01

    Set partitioning to multi-dimensional signal spaces over GF(q), particularly GF sup q-1(q) and GF sup q (q), and show how to construct both multi-level block codes and multi-level trellis codes over GF(q). Two classes of multi-level (n, k, d) block codes over GF(q) with block length n, number of information symbols k, and minimum distance d sub min greater than or = d, are presented. These two classes of codes use Reed-Solomon codes as component codes. They can be easily decoded as block length q-1 Reed-Solomon codes or block length q or q + 1 extended Reed-Solomon codes using multi-stage decoding. Many of these codes have larger distances than comparable q-ary block codes, as component codes. Low rate q-ary convolutional codes, work error correcting convolutional codes, and binary-to-q-ary convolutional codes can also be used to construct multi-level trellis codes over GF(q) or binary-to-q-ary trellis codes, some of which have better performance than the above block codes. All of the new codes have simple decoding algorithms based on hard decision multi-stage decoding.

  18. Exploring the Nature of Divergent Thinking: A Multilevel Analysis

    ERIC Educational Resources Information Center

    Kuhn, Jorg-Tobias; Holling, Heinz

    2009-01-01

    In this study, a large sample with a clustered data structure from an educational context was utilized to analyze the relationship between cognitive abilities, school type, gender, and divergent thinking. The sample comprised 1098 students in 55 classrooms. A sequence of nested multilevel regression analyses revealed that processing capacity, as a…

  19. Criminal Victimization and Crime Risk Perception: A Multilevel Longitudinal Study

    ERIC Educational Resources Information Center

    Russo, Silvia; Roccato, Michele; Vieno, Alessio

    2013-01-01

    In a national sample of the Italian population, surveyed four times between October 2002 and January 2007 (N = 2,008), we performed a multilevel longitudinal study aimed at predicting the increase in crime risk perception as a function of three families of independent variables, respectively lying at the within individual level (direct…

  20. Social Capital and Health: A Review of Prospective Multilevel Studies

    PubMed Central

    Murayama, Hiroshi; Fujiwara, Yoshinori; Kawachi, Ichiro

    2012-01-01

    Background This article presents an overview of the concept of social capital, reviews prospective multilevel analytic studies of the association between social capital and health, and discusses intervention strategies that enhance social capital. Methods We conducted a systematic search of published peer-reviewed literature on the PubMed database and categorized studies according to health outcome. Results We identified 13 articles that satisfied the inclusion criteria for the review. In general, both individual social capital and area/workplace social capital had positive effects on health outcomes, regardless of study design, setting, follow-up period, or type of health outcome. Prospective studies that used a multilevel approach were mainly conducted in Western countries. Although we identified some cross-sectional multilevel studies that were conducted in Asian countries, including Japan, no prospective studies have been conducted in Asia. Conclusions Prospective evidence from multilevel analytic studies of the effect of social capital on health is very limited at present. If epidemiologic findings on the association between social capital and health are to be put to practical use, we must gather additional evidence and explore the feasibility of interventions that build social capital as a means of promoting health. PMID:22447212

  1. The Formation of Parent-School Trust: A Multilevel Analysis

    ERIC Educational Resources Information Center

    Adams, Curt M.; Forsyth, Patrick B.; Mitchell, Roxanne M.

    2009-01-01

    Purpose: The authors' focus was on understanding antecedents of parent trust toward schools. Two questions guided the inquiry: Is there a systematic difference in parent-school trust across schools? If so, what organizational conditions predict between-school variability in parent-school trust? Research Methods/Approach: Using multilevel modeling,…

  2. Sex Differences in Science Achievement: A Multilevel Analysis.

    ERIC Educational Resources Information Center

    Young, Deidra J.; Fraser, Barry J.

    The assertion that girls and boys in single-sex schools outperform their peers attending coeducational schools was investigated in this study with particular reference to physics achievement. The relationship between the school, the home and the student's performance in physics was also explored tentatively using multilevel analysis. The average…

  3. Multilevel Analysis of Student Pathways to Higher Education

    ERIC Educational Resources Information Center

    You, Sukkyung; Nguyen, Julie

    2012-01-01

    This study examined the relationship between academic preparation and post-secondary educational outcomes. To uncover the factors that influence secondary-level school course-taking patterns and outcomes, multi-level modelling was conducted using data from a nationally representative sample of US secondary-level school students from the Education…

  4. Neighborhoods and Child Maltreatment: A Multi-Level Study.

    ERIC Educational Resources Information Center

    Coulton, Claudia; Korbin, Jill; Su, Marilyn

    This study explores the influence of neighborhood conditions on child maltreatment. Unlike previous studies conducted with protective services data aggregated to neighborhoods, this study uses a self-report measure of child abuse potential and controls for individual risk factors in a multilevel model. The survey was completed by an adult residing…

  5. The Dubious Benefits of Multi-Level Modeling

    ERIC Educational Resources Information Center

    Gorard, Stephen

    2007-01-01

    This paper presents an argument against the wider adoption of complex forms of data analysis, using multi-level modeling (MLM) as an extended case study. MLM was devised to overcome some deficiencies in existing datasets, such as the bias caused by clustering. The paper suggests that MLM has an unclear theoretical and empirical basis, has not led…

  6. Multilevel Analysis Methods for Partially Nested Cluster Randomized Trials

    ERIC Educational Resources Information Center

    Sanders, Elizabeth A.

    2011-01-01

    This paper explores multilevel modeling approaches for 2-group randomized experiments in which a treatment condition involving clusters of individuals is compared to a control condition involving only ungrouped individuals, otherwise known as partially nested cluster randomized designs (PNCRTs). Strategies for comparing groups from a PNCRT in the…

  7. A Multilevel Evaluation of a Comprehensive Child Abuse Prevention Program

    ERIC Educational Resources Information Center

    Lawson, Michael A.; Alameda-Lawson, Tania; Byrnes, Edward C.

    2012-01-01

    Objectives: The purpose of this study is to examine the extent to which participation in a county-wide prevention program leads to improvements in protective factors associated with child abuse prevention (CAP) and whether improvements in measured protective factors relate to decreased odds of child abuse. Method: Using multilevel growth modeling,…

  8. Gender, Reasoning Ability, and Scholastic Achievement: A Multilevel Mediation Analysis

    ERIC Educational Resources Information Center

    Kuhn, Jorg-Tobias; Holling, Heinz

    2009-01-01

    The present study investigated gender differences in scholastic achievement (school grades in sciences and languages) as mediated by reasoning ability in a large sample with a clustered data structure from an educational context. Whereas girls outperformed boys in languages, boys excelled in sciences and reasoning. Multilevel analyses indicated a…

  9. Determinants of Academic Entrepreneurship Behavior: A Multilevel Model

    ERIC Educational Resources Information Center

    Llano, Joseph Anthony

    2010-01-01

    It is well established that universities encourage the acquisition and dissemination of new knowledge among university community members and beyond. However, what is less well understood is how universities encourage entrepreneurial (opportunity discovery, evaluation, and exploiting) behavior. This research investigated a multilevel model of the…

  10. Multilevel metallization method for fabricating a metal oxide semiconductor device

    NASA Technical Reports Server (NTRS)

    Hollis, B. R., Jr.; Feltner, W. R.; Bouldin, D. L.; Routh, D. E. (Inventor)

    1978-01-01

    An improved method is described of constructing a metal oxide semiconductor device having multiple layers of metal deposited by dc magnetron sputtering at low dc voltages and low substrate temperatures. The method provides multilevel interconnections and cross over between individual circuit elements in integrated circuits without significantly reducing the reliability or seriously affecting the yield.

  11. People Are Variables Too: Multilevel Structural Equations Modeling

    ERIC Educational Resources Information Center

    Mehta, Paras D.; Neale, Michael C.

    2005-01-01

    The article uses confirmatory factor analysis (CFA) as a template to explain didactically multilevel structural equation models (ML-SEM) and to demonstrate the equivalence of general mixed-effects models and ML-SEM. An intuitively appealing graphical representation of complex ML-SEMs is introduced that succinctly describes the underlying model and…

  12. Organizational Design in High Schools: A Multilevel Analysis.

    ERIC Educational Resources Information Center

    Rowan, Brian; And Others

    1991-01-01

    Reviews research on the effectiveness of supportive leadership, teacher participation in decision making, and staff collaboration. Investigates conditions that promote or impede the implementation of these practices by using a multilevel statistical model. Finds significant variance between public and Catholic schools, as well as within-school…

  13. Help Seeking in Online Collaborative Groupwork: A Multilevel Analysis

    ERIC Educational Resources Information Center

    Du, Jianxia; Xu, Jianzhong; Fan, Xitao

    2015-01-01

    This study examined predictive models for students' help seeking in the context of online collaborative groupwork. Results from multilevel analysis revealed that most of the variance in help seeking was at the individual student level, and multiple variables at the individual level were predictive of help-seeking behaviour. Help seeking was…

  14. Multilevel Modeling: Overview and Applications to Research in Counseling Psychology

    ERIC Educational Resources Information Center

    Kahn, Jeffrey H.

    2011-01-01

    Multilevel modeling (MLM) is rapidly becoming the standard method of analyzing nested data, for example, data from students within multiple schools, data on multiple clients seen by a smaller number of therapists, and even longitudinal data. Although MLM analyses are likely to increase in frequency in counseling psychology research, many readers…

  15. Illustration of a Multilevel Model for Meta-Analysis

    ERIC Educational Resources Information Center

    de la Torre, Jimmy; Camilli, Gregory; Vargas, Sadako; Vernon, R. Fox

    2007-01-01

    In this article, the authors present a multilevel (or hierarchical linear) model that illustrates issues in the application of the model to data from meta-analytic studies. In doing so, several issues are discussed that typically arise in the course of a meta-analysis. These include the presence of non-zero between-study variability, how multiple…

  16. Needs-Based Curriculum Development Process: A Multilevel Conception

    ERIC Educational Resources Information Center

    Mehrmohammadi, Mahmoud

    2005-01-01

    Needs assessment has been regarded as a critical stage in the curriculum development process. However, theoretical efforts aiming at proper formulation of this stage are disappointingly rare in the curriculum literature. This article is based on the recognition of this fact and proposes a multilevel conception of needs assessment in the curriculum…

  17. Performance Analysis of Multilevel Parallel Applications on Shared Memory Architectures

    NASA Technical Reports Server (NTRS)

    Biegel, Bryan A. (Technical Monitor); Jost, G.; Jin, H.; Labarta J.; Gimenez, J.; Caubet, J.

    2003-01-01

    Parallel programming paradigms include process level parallelism, thread level parallelization, and multilevel parallelism. This viewgraph presentation describes a detailed performance analysis of these paradigms for Shared Memory Architecture (SMA). This analysis uses the Paraver Performance Analysis System. The presentation includes diagrams of a flow of useful computations.

  18. Time to the Doctorate: Multilevel Discrete-Time Hazard Analysis

    ERIC Educational Resources Information Center

    Wao, Hesborn O.

    2010-01-01

    Secondary data on 1,028 graduate students nested within 24 programs and admitted into either a Ph. D. or Ed. D. program between 1990 and 2006 at an American public university were used to illustrate the benefits of employing multilevel discrete-time hazard analysis in understanding the timing of doctorate completion in Education and the factors…

  19. Homework Purposes Reported by Secondary School Students: A Multilevel Analysis

    ERIC Educational Resources Information Center

    Xu, Jianzhong

    2010-01-01

    The author examined purposes for doing homework as perceived by 969 eighth-grade students from 52 classes and 831 11th-grade students from 45 classes. Through an exploratory factor analysis, 15 homework purposes were reduced to a 3-factor structure: peer-oriented, adult-oriented, and learning-oriented reasons. A series of 3 multilevel models were…

  20. Outward Bound Outcome Model Validation and Multilevel Modeling

    ERIC Educational Resources Information Center

    Luo, Yuan-Chun

    2011-01-01

    This study was intended to measure construct validity for the Outward Bound Outcomes Instrument (OBOI) and to predict outcome achievement from individual characteristics and course attributes using multilevel modeling. A sample of 2,340 participants was collected by Outward Bound USA between May and September 2009 using the OBOI. Two phases of…

  1. Hierarchical Logistic Regression: Accounting for Multilevel Data in DIF Detection

    ERIC Educational Resources Information Center

    French, Brian F.; Finch, W. Holmes

    2010-01-01

    The purpose of this study was to examine the performance of differential item functioning (DIF) assessment in the presence of a multilevel structure that often underlies data from large-scale testing programs. Analyses were conducted using logistic regression (LR), a popular, flexible, and effective tool for DIF detection. Data were simulated…

  2. Multilevel Modeling of Science Achievement in the Timss Participating Countries

    ERIC Educational Resources Information Center

    Mohammadpour, Ebrahim; Shekarchizadeh, Ahmadreza; Kalantarrashidi, Shojae Aldin

    2015-01-01

    The authors aimed to investigate the variability in science achievement as a function of student-, school- and country-level factors. Achievement scores of 134,123 eighth-grade students from 4,511 schools of 29 countries who participated in the 2007 Trends in International Mathematics and Science Study were analyzed. Multilevel modeling results…

  3. Cross-Classification Multilevel Logistic Models in Psychometrics

    ERIC Educational Resources Information Center

    Van den Noortgate, Wim; De Boeck, Paul; Meulders, Michel

    2003-01-01

    In IRT models, responses are explained on the basis of person and item effects. Person effects are usually defined as a random sample from a population distribution. Regular IRT models therefore can be formulated as multilevel models, including a within-person part and a between-person part. In a similar way, the effects of the items can be…

  4. Using Multilevel Modeling in Language Assessment Research: A Conceptual Introduction

    ERIC Educational Resources Information Center

    Barkaoui, Khaled

    2013-01-01

    This article critiques traditional single-level statistical approaches (e.g., multiple regression analysis) to examining relationships between language test scores and variables in the assessment setting. It highlights the conceptual, methodological, and statistical problems associated with these techniques in dealing with multilevel or nested…

  5. Nonlinear resonant phenomena in multilevel quantum systems

    NASA Astrophysics Data System (ADS)

    Hicke, Christian

    We study nonlinear resonant phenomena in two-level and multilevel quantum systems. Our results are of importance for applications in the areas of quantum control, quantum computation, and quantum measurement. We present a method to perform fault-tolerant single-qubit gate operations using Landau-Zener tunneling. In a single Landau-Zoner pulse, the qubit transition frequency is varied in time so that it passes through the frequency of a radiation field. We show that a simple three-pulse sequence allows eliminating errors in the gate up to the third order in errors in the qubit energies or the radiation frequency. We study the nonlinear transverse response of a spin S > 1/2 with easy-axis anisotropy. The coherent transverse response displays sharp dips or peaks when the modulation frequency is adiabatically swept through multiphoton resonance. The effect is a consequence of a certain conformal property of the spin dynamics in a magnetic field for the anisotropy energy ∝ S2z . The occurrence of the dips or peaks is determined by the spin state. Their shape strongly depends on the modulation amplitude. Higher-order anisotropy breaks the symmetry, leading to sharp steps in the transverse response as function of frequency. The results bear on the dynamics of molecular magnets in a static magnetic field. We show that a modulated large-spin system has special symmetry. In the presence of dissipation it leads to characteristic nonlinear effects. They include abrupt switching between transverse magnetization branches with varying modulating field without hysteresis and a specific pattern of switching in the presence of multistability and hysteresis. Along with steady forced vibrations the transverse spin components can display transient vibrations at a combination of the Larmor frequency and a slower frequency determined by the anisotropy energy. The analysis is based on a microscopic theory that takes into account relaxation mechanisms important for single

  6. Detailed Modeling, Design, and Evaluation of a Scalable Multi-level Checkpointing System

    SciTech Connect

    Moody, A T; Bronevetsky, G; Mohror, K M; de Supinski, B R

    2010-04-09

    High-performance computing (HPC) systems are growing more powerful by utilizing more hardware components. As the system mean-time-before-failure correspondingly drops, applications must checkpoint more frequently to make progress. However, as the system memory sizes grow faster than the bandwidth to the parallel file system, the cost of checkpointing begins to dominate application run times. A potential solution to this problem is to use multi-level checkpointing, which employs multiple types of checkpoints with different costs and different levels of resiliency in a single run. The goal is to design light-weight checkpoints to handle the most common failure modes and rely on more expensive checkpoints for less common, but more severe failures. While this approach is theoretically promising, it has not been fully evaluated in a large-scale, production system context. To this end we have designed a system, called the Scalable Checkpoint/Restart (SCR) library, that writes checkpoints to storage on the compute nodes utilizing RAM, Flash, or disk, in addition to the parallel file system. We present the performance and reliability properties of SCR as well as a probabilistic Markov model that predicts its performance on current and future systems. We show that multi-level checkpointing improves efficiency on existing large-scale systems and that this benefit increases as the system size grows. In particular, we developed low-cost checkpoint schemes that are 100x-1000x faster than the parallel file system and effective against 85% of our system failures. This leads to a gain in machine efficiency of up to 35%, and it reduces the the load on the parallel file system by a factor of two on current and future systems.

  7. Multilevel Methods for the Poisson-Boltzmann Equation

    NASA Astrophysics Data System (ADS)

    Holst, Michael Jay

    We consider the numerical solution of the Poisson -Boltzmann equation (PBE), a three-dimensional second order nonlinear elliptic partial differential equation arising in biophysics. This problem has several interesting features impacting numerical algorithms, including discontinuous coefficients representing material interfaces, rapid nonlinearities, and three spatial dimensions. Similar equations occur in various applications, including nuclear physics, semiconductor physics, population genetics, astrophysics, and combustion. In this thesis, we study the PBE, discretizations, and develop multilevel-based methods for approximating the solutions of these types of equations. We first outline the physical model and derive the PBE, which describes the electrostatic potential of a large complex biomolecule lying in a solvent. We next study the theoretical properties of the linearized and nonlinear PBE using standard function space methods; since this equation has not been previously studied theoretically, we provide existence and uniqueness proofs in both the linearized and nonlinear cases. We also analyze box-method discretizations of the PBE, establishing several properties of the discrete equations which are produced. In particular, we show that the discrete nonlinear problem is well-posed. We study and develop linear multilevel methods for interface problems, based on algebraic enforcement of Galerkin or variational conditions, and on coefficient averaging procedures. Using a stencil calculus, we show that in certain simplified cases the two approaches are equivalent, with different averaging procedures corresponding to different prolongation operators. We also develop methods for nonlinear problems based on a nonlinear multilevel method, and on linear multilevel methods combined with a globally convergent damped-inexact-Newton method. We derive a necessary and sufficient descent condition for the inexact-Newton direction, enabling the development of extremely

  8. Computerized multilevel analysis for multilayered fiber composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1972-01-01

    A FORTRAN 4 computer code for the micromechanics, macromechanics, and laminate analysis of multilayered fiber composite structural components is described. The code can be used either individually or as a subroutine within a complex structural analysis/synthesis program. The inputs to the code are constituent materials properties, composite geometry, and loading conditions. The outputs are various properties for ply and composite; composite structural response, including bending-stretching coupling; and composite stress analysis, including comparisons with failure criteria for combined stress. The code was used successfully in the analysis and structural synthesis of flat panels, in the buckling analysis of flat panels, in multilayered composite material failure studies, and lamination residual stresses analysis.

  9. Performance analysis of cascaded h-bridge multilevel inverter using mixed switching frequency with various dc-link voltages

    NASA Astrophysics Data System (ADS)

    Citarsa, I. B. F.; Satiawan, I. N. W.; Wiryajati, I. K.; Supriono

    2016-01-01

    Multilevel inverters have been widely used in many applications since the technology is advantageous to increase the converter capability as well as to improve the output voltage quality. According to the applied switching frequency, multilevel modulations can be subdivided into three classes, i.e: fundamental switching frequency, high switching frequency and mixed switching frequency. This paper investigates the performance of cascaded H-bridge (CHB) multilevel inverter that is modulated using mixed switching frequency (MSF) PWM with various dc-link voltage ratios. The simulation results show the nearly sinusoidal load output voltages are successfully achieved. It is revealed that there is improvement in output voltages quality in terms of THD and low-order harmonics content. The CHB inverter that is modulated using MSF PWM with equal dc-link voltage ratio (½ Vdc: ½ Vdc) produces output voltage with the lowest low-order harmonics (less than 1% of fundamental) while the CHB inverter that is modulated using MSF PWM with un-equal dc-link voltage ratio (2/3 Vdc: 1/3 Vdc) produces a 7-level output voltage with the lowest THD (16.31%) compared to the other PWM methods. Improvement of the output voltage quality here is also in line with improvement of the number of available levels provided in the output voltage. Here only 2 cells H-bridge inverter (contain 8 switches) are needed to produce a 7- level output voltage, while in the conventional CHB inverter at least 3 cells of H-bridge inverter (contain 12 switches) are needed to produce a 7-level output voltage. Hence it is valuable in term of saving number of component.

  10. The Importance of Isomorphism for Conclusions about Homology: A Bayesian Multilevel Structural Equation Modeling Approach with Ordinal Indicators

    PubMed Central

    Guenole, Nigel

    2016-01-01

    We describe a Monte Carlo study examining the impact of assuming item isomorphism (i.e., equivalent construct meaning across levels of analysis) on conclusions about homology (i.e., equivalent structural relations across levels of analysis) under varying degrees of non-isomorphism in the context of ordinal indicator multilevel structural equation models (MSEMs). We focus on the condition where one or more loadings are higher on the between level than on the within level to show that while much past research on homology has ignored the issue of psychometric isomorphism, psychometric isomorphism is in fact critical to valid conclusions about homology. More specifically, when a measurement model with non-isomorphic items occupies an exogenous position in a multilevel structural model and the non-isomorphism of these items is not modeled, the within level exogenous latent variance is under-estimated leading to over-estimation of the within level structural coefficient, while the between level exogenous latent variance is overestimated leading to underestimation of the between structural coefficient. When a measurement model with non-isomorphic items occupies an endogenous position in a multilevel structural model and the non-isomorphism of these items is not modeled, the endogenous within level latent variance is under-estimated leading to under-estimation of the within level structural coefficient while the endogenous between level latent variance is over-estimated leading to over-estimation of the between level structural coefficient. The innovative aspect of this article is demonstrating that even minor violations of psychometric isomorphism render claims of homology untenable. We also show that posterior predictive p-values for ordinal indicator Bayesian MSEMs are insensitive to violations of isomorphism even when they lead to severely biased within and between level structural parameters. We highlight conditions where poor estimation of even correctly specified

  11. Nonresonant interaction of ultrashort electromagnetic pulses with multilevel quantum systems

    NASA Technical Reports Server (NTRS)

    Belenov, E.; Isakov, V.; Nazarkin, A.

    1994-01-01

    Some features of the excitation of multilevel quantum systems under the action of electromagnetic pulses which are shorter than the inverse frequency of interlevel transitions are considered. It is shown that the interaction is characterized by a specific type of selectivity which is not connected with the resonant absorption of radiation. The simplest three-level model displays the inverse population of upper levels. The effect of an ultrashort laser pulse on a multilevel molecule was regarded as an instant reception of the oscillation velocity by the oscillator and this approach showed an effective excitation and dissociation of the molecule. The estimations testify to the fact that these effects can be observed using modern femtosecond lasers.

  12. Improved Bat Algorithm Applied to Multilevel Image Thresholding

    PubMed Central

    2014-01-01

    Multilevel image thresholding is a very important image processing technique that is used as a basis for image segmentation and further higher level processing. However, the required computational time for exhaustive search grows exponentially with the number of desired thresholds. Swarm intelligence metaheuristics are well known as successful and efficient optimization methods for intractable problems. In this paper, we adjusted one of the latest swarm intelligence algorithms, the bat algorithm, for the multilevel image thresholding problem. The results of testing on standard benchmark images show that the bat algorithm is comparable with other state-of-the-art algorithms. We improved standard bat algorithm, where our modifications add some elements from the differential evolution and from the artificial bee colony algorithm. Our new proposed improved bat algorithm proved to be better than five other state-of-the-art algorithms, improving quality of results in all cases and significantly improving convergence speed. PMID:25165733

  13. On the Multilevel Solution Algorithm for Markov Chains

    NASA Technical Reports Server (NTRS)

    Horton, Graham

    1997-01-01

    We discuss the recently introduced multilevel algorithm for the steady-state solution of Markov chains. The method is based on an aggregation principle which is well established in the literature and features a multiplicative coarse-level correction. Recursive application of the aggregation principle, which uses an operator-dependent coarsening, yields a multi-level method which has been shown experimentally to give results significantly faster than the typical methods currently in use. When cast as a multigrid-like method, the algorithm is seen to be a Galerkin-Full Approximation Scheme with a solution-dependent prolongation operator. Special properties of this prolongation lead to the cancellation of the computationally intensive terms of the coarse-level equations.

  14. Learning in multilevel games with incomplete information. II.

    PubMed

    Zhou, J; Billard, E; Lakshmivarahan, S

    1999-01-01

    Multilevel games are abstractions of situations where decision makers are distributed in a network environment. In Part I of this paper, the authors present several of the challenging problems that arise in the analysis of multilevel games. In this paper a specific set up is considered where the two games being played are zero-sum games and where the decision makers use the linear reward-inaction algorithm of stochastic learning automata. It is shown that the effective game matrix is decided by the willingness and the ability to cooperate and is a convex combination of two zero-sum game matrices. Analysis of the properties of this effective game matrix and the convergence of the decision process shows that players tend toward noncooperation in these specific environments. Simulation results illustrate this noncooperative behavior. PMID:18252309

  15. Multi-level Hybrid Cache: Impact and Feasibility

    SciTech Connect

    Zhang, Zhe; Kim, Youngjae; Ma, Xiaosong; Shipman, Galen M; Zhou, Yuanyuan

    2012-02-01

    Storage class memories, including flash, has been attracting much attention as promising candidates fitting into in today's enterprise storage systems. In particular, since the cost and performance characteristics of flash are in-between those of DRAM and hard disks, it has been considered by many studies as an secondary caching layer underneath main memory cache. However, there has been a lack of studies of correlation and interdependency between DRAM and flash caching. This paper views this problem as a special form of multi-level caching, and tries to understand the benefits of this multi-level hybrid cache hierarchy. We reveal that significant costs could be saved by using Flash to reduce the size of DRAM cache, while maintaing the same performance. We also discuss design challenges of using flash in the caching hierarchy and present potential solutions.

  16. Multilevel Research and the Challenges of Implementing Genomic Medicine

    PubMed Central

    Coates, Ralph J.; Fennell, Mary L.; Glasgow, Russell E.; Scheuner, Maren T.; Schully, Sheri D.; Williams, Marc S.; Clauser, Steven B.

    2012-01-01

    Advances in genomics and related fields promise a new era of personalized medicine in the cancer care continuum. Nevertheless, there are fundamental challenges in integrating genomic medicine into cancer practice. We explore how multilevel research can contribute to implementation of genomic medicine. We first review the rapidly developing scientific discoveries in this field and the paucity of current applications that are ready for implementation in clinical and public health programs. We then define a multidisciplinary translational research agenda for successful integration of genomic medicine into policy and practice and consider challenges for successful implementation. We illustrate the agenda using the example of Lynch syndrome testing in newly diagnosed cases of colorectal cancer and cascade testing in relatives. We synthesize existing information in a framework for future multilevel research for integrating genomic medicine into the cancer care continuum. PMID:22623603

  17. Multilevel factors affecting quality: examples from the cancer care continuum.

    PubMed

    Zapka, Jane; Taplin, Stephen H; Ganz, Patricia; Grunfeld, Eva; Sterba, Katherine

    2012-05-01

    The complex environmental context must be considered as we move forward to improve cancer care and, ultimately, patient and population outcomes. The cancer care continuum represents several care types, each of which includes multiple technical and communication steps and interfaces among patients, providers, and organizations. We use two case scenarios to 1) illustrate the variability, diversity, and interaction of factors from multiple levels that affect care quality and 2) discuss research implications and provide hypothetical examples of multilevel interventions. Each scenario includes a targeted literature review to illustrate contextual influences upon care and sets the stage for theory-informed interventions. The screening case highlights access issues in older women, and the survivorship case illustrates the multiple transition challenges faced by patients, families, and organizations. Example interventions show the potential gains of implementing intervention strategies that work synergistically at multiple levels. While research examining multilevel intervention is a priority, it presents numerous study design, measurement, and analytic challenges. PMID:22623591

  18. Improved bat algorithm applied to multilevel image thresholding.

    PubMed

    Alihodzic, Adis; Tuba, Milan

    2014-01-01

    Multilevel image thresholding is a very important image processing technique that is used as a basis for image segmentation and further higher level processing. However, the required computational time for exhaustive search grows exponentially with the number of desired thresholds. Swarm intelligence metaheuristics are well known as successful and efficient optimization methods for intractable problems. In this paper, we adjusted one of the latest swarm intelligence algorithms, the bat algorithm, for the multilevel image thresholding problem. The results of testing on standard benchmark images show that the bat algorithm is comparable with other state-of-the-art algorithms. We improved standard bat algorithm, where our modifications add some elements from the differential evolution and from the artificial bee colony algorithm. Our new proposed improved bat algorithm proved to be better than five other state-of-the-art algorithms, improving quality of results in all cases and significantly improving convergence speed. PMID:25165733

  19. On the multi-level solution algorithm for Markov chains

    SciTech Connect

    Horton, G.

    1996-12-31

    We discuss the recently introduced multi-level algorithm for the steady-state solution of Markov chains. The method is based on the aggregation principle, which is well established in the literature. Recursive application of the aggregation yields a multi-level method which has been shown experimentally to give results significantly faster than the methods currently in use. The algorithm can be reformulated as an algebraic multigrid scheme of Galerkin-full approximation type. The uniqueness of the scheme stems from its solution-dependent prolongation operator which permits significant computational savings in the evaluation of certain terms. This paper describes the modeling of computer systems to derive information on performance, measured typically as job throughput or component utilization, and availability, defined as the proportion of time a system is able to perform a certain function in the presence of component failures and possibly also repairs.

  20. Multilevel interventions and racial/ethnic health disparities.

    PubMed

    Gorin, Sherri Sheinfeld; Badr, Hoda; Krebs, Paul; Prabhu Das, Irene

    2012-05-01

    To examine the impact of multilevel interventions (with three or more levels of influence) designed to reduce health disparities, we conducted a systematic review and meta-analysis of interventions for ethnic/racial minorities (all except non-Hispanic whites) that were published between January 2000 and July 2011. The primary aims were to synthesize the findings of studies evaluating multilevel interventions (three or more levels of influence) targeted at ethnic and racial minorities to reduce disparities in their health care and obtain a quantitative estimate of the effect of multilevel interventions on health outcomes among these subgroups. The electronic database PubMed was searched using Medical Subject Heading terms and key words. After initial review of abstracts, 26 published studies were systematically reviewed by at least two independent coders. Those with sufficient data (n = 12) were assessed by meta-analysis and examined for quality using a modified nine-item Physiotherapy Evidence Database coding scheme. The findings from this descriptive review suggest that multilevel interventions have positive effects on several health behavior outcomes, including cancer prevention and screening, as well improving the quality of health-care system processes. The weighted average effect size across studies for all health behavior outcomes reported at the individual participant level (k = 17) was odds ratio (OR) = 1.27 (95% confidence interval [CI] = 1.11 to 1.44); for the outcomes reported by providers or organizations, the weighted average effect size (k = 3) was OR = 2.53 (95% CI = 0.82 to 7.81). Enhanced application of theories to multiple levels of change, novel design approaches, and use of cultural leveraging in intervention design and implementation are proposed for this nascent field. PMID:22623602

  1. Integrated control/structure optimization by multilevel decomposition

    NASA Technical Reports Server (NTRS)

    Zeiler, Thomas A.; Gilbert, Michael G.

    1990-01-01

    A method for integrated control/structure optimization by multilevel decomposition is presented. It is shown that several previously reported methods were actually partial decompositions wherein only the control was decomposed into a subsystem design. One of these partially decomposed problems was selected as a benchmark example for comparison. The present paper fully decomposes the system into structural and control subsystem designs and produces an improved design. Theory, implementation, and results for the method are presented and compared with the benchmark example.

  2. Integrated control/structure optimization by multilevel decomposition

    NASA Technical Reports Server (NTRS)

    Zeiler, Thomas A.; Gilbert, Michael G.

    1990-01-01

    A method for integrated control/structure optimization by multilevel decomposition is presented. It is shown that several previously reported methods were actually partial decompositions wherein only the control was decomposed into a subsystem design. One of these partially decomposed problems was selected as a benchmark example for comparison. The system is fully decomposed into structural and control subsystem designs and an improved design is produced. Theory, implementation, and results for the method are presented and compared with the benchmark example.

  3. An efficient multilevel optimization method for engineering design

    NASA Technical Reports Server (NTRS)

    Vanderplaats, G. N.; Yang, Y. J.; Kim, D. S.

    1988-01-01

    An efficient multilevel deisgn optimization technique is presented. The proposed method is based on the concept of providing linearized information between the system level and subsystem level optimization tasks. The advantages of the method are that it does not require optimum sensitivities, nonlinear equality constraints are not needed, and the method is relatively easy to use. The disadvantage is that the coupling between subsystems is not dealt with in a precise mathematical manner.

  4. Organolead Halide Perovskites for Low Operating Voltage Multilevel Resistive Switching.

    PubMed

    Choi, Jaeho; Park, Sunghak; Lee, Joohee; Hong, Kootak; Kim, Do-Hong; Moon, Cheon Woo; Park, Gyeong Do; Suh, Junmin; Hwang, Jinyeon; Kim, Soo Young; Jung, Hyun Suk; Park, Nam-Gyu; Han, Seungwu; Nam, Ki Tae; Jang, Ho Won

    2016-08-01

    Organolead halide perovskites are used for low-operating-voltage multilevel resistive switching. Ag/CH3 NH3 PbI3 /Pt cells exhibit electroforming-free resistive switching at an electric field of 3.25 × 10(3) V cm(-1) for four distinguishable ON-state resistance levels. The migration of iodine interstitials and vacancies with low activation energies is responsible for the low-electric-field resistive switching via filament formation and annihilation. PMID:27192161

  5. Doubly Latent Multilevel Analyses of Classroom Climate: An Illustration

    ERIC Educational Resources Information Center

    Morin, Alexandre J. S.; Marsh, Herbert W.; Nagengast, Benjamin; Scalas, L. Francesca

    2014-01-01

    Many classroom climate studies suffer from 2 critical problems: They (a) treat climate as a student-level (L1) variable in single-level analyses instead of a classroom-level (L2) construct in multilevel analyses; and (b) rely on manifest-variable models rather than on latent-variable models that control measurement error at L1 and L2, and sampling…

  6. Sericin for resistance switching device with multilevel nonvolatile memory.

    PubMed

    Wang, Hong; Meng, Fanben; Cai, Yurong; Zheng, Liyan; Li, Yuangang; Liu, Yuanjun; Jiang, Yueyue; Wang, Xiaotian; Chen, Xiaodong

    2013-10-11

    Resistance switching characteristics of natural sericin protein film is demonstrated for nonvolatile memory application for the first time. Excellent memory characteristics with a resistance OFF/ON ratio larger than 10(6) have been obtained and a multilevel memory based on sericin has been achieved. The environmentally friendly high performance biomaterial based memory devices may hold a place in the future of electronic device development. PMID:23893500

  7. A multi-level method for sparse linear systems

    SciTech Connect

    Shapira, Y.

    1997-09-01

    A multi-level method for the solution of sparse linear systems is introduced. The definition of the method is based on data from the coefficient matrix alone. An upper bound for the condition number is available for certain symmetric positive definite (SPD) problems. Numerical experiments confirm the analysis and illustrate the efficiency of the method for diffusion problems with discontinuous coefficients with discontinuities which are not aligned with the coarse meshes.

  8. Multi-level methods and approximating distribution functions

    NASA Astrophysics Data System (ADS)

    Wilson, D.; Baker, R. E.

    2016-07-01

    Biochemical reaction networks are often modelled using discrete-state, continuous-time Markov chains. System statistics of these Markov chains usually cannot be calculated analytically and therefore estimates must be generated via simulation techniques. There is a well documented class of simulation techniques known as exact stochastic simulation algorithms, an example of which is Gillespie's direct method. These algorithms often come with high computational costs, therefore approximate stochastic simulation algorithms such as the tau-leap method are used. However, in order to minimise the bias in the estimates generated using them, a relatively small value of tau is needed, rendering the computational costs comparable to Gillespie's direct method. The multi-level Monte Carlo method (Anderson and Higham, Multiscale Model. Simul. 10:146-179, 2012) provides a reduction in computational costs whilst minimising or even eliminating the bias in the estimates of system statistics. This is achieved by first crudely approximating required statistics with many sample paths of low accuracy. Then correction terms are added until a required level of accuracy is reached. Recent literature has primarily focussed on implementing the multi-level method efficiently to estimate a single system statistic. However, it is clearly also of interest to be able to approximate entire probability distributions of species counts. We present two novel methods that combine known techniques for distribution reconstruction with the multi-level method. We demonstrate the potential of our methods using a number of examples.

  9. On codes with multi-level error-correction capabilities

    NASA Technical Reports Server (NTRS)

    Lin, Shu

    1987-01-01

    In conventional coding for error control, all the information symbols of a message are regarded equally significant, and hence codes are devised to provide equal protection for each information symbol against channel errors. However, in some occasions, some information symbols in a message are more significant than the other symbols. As a result, it is desired to devise codes with multilevel error-correcting capabilities. Another situation where codes with multi-level error-correcting capabilities are desired is in broadcast communication systems. An m-user broadcast channel has one input and m outputs. The single input and each output form a component channel. The component channels may have different noise levels, and hence the messages transmitted over the component channels require different levels of protection against errors. Block codes with multi-level error-correcting capabilities are also known as unequal error protection (UEP) codes. Structural properties of these codes are derived. Based on these structural properties, two classes of UEP codes are constructed.

  10. Flexible Job Shop Scheduling with Multi-level Job Structures

    NASA Astrophysics Data System (ADS)

    Jang, Yang-Ja; Kim, Ki-Dong; Jang, Seong-Yong; Park, Jinwoo

    This paper deals with a scheduling problem in a flexible job shop with multi-level job structures where end products are assembled from sub-assemblies or manufactured components. For such shops MRP (Material Requirement Planning) logic is frequently used to synchronize and pace the production activities for the required parts. However, in MRP, the planning of operational-level activities is left to short term scheduling. So, we need a good scheduling algorithm to generate feasible schedules taking into account shop floor characteristics and multi-level job structures used in MRP. In this paper, we present a GA (Genetic Algorithm) solution for this complex scheduling problem based on a new gene to reflect the machine assignment, operation sequences and the levels of the operations relative to final assembly operation. The relative operation level is the control parameter that paces the completion timing of the components belonging to the same branch in the multi-level job hierarchy. We compare the genetic algorithm with several dispatching rules in terms of total tardiness and the genetic algorithm shows outstanding performance for about forty modified standard job-shop problem instances.

  11. Building Xperience: a multilevel alcohol and drug prevention intervention.

    PubMed

    Diamond, Sarah; Schensul, Jean J; Snyder, Leslie B; Bermudez, Alessandro; D'Alessandro, Nicole; Morgan, Damion Sincere

    2009-06-01

    "Xperience" is an innovative alcohol and drug prevention program that has adopted a multilevel, community-based strategy to promote drug-and-alcohol free social activities, venues and norms among urban youth ages 14-20. The intervention aims to strengthen protective factors and reduce risk factors for alcohol and other substance use among high school age youth by addressing multiple factors at the individual, peer, community and city level. The purpose of this paper is to discuss the process of building the different levels of this intervention during the 3-year formative phase. We will explain: (1) Why we chose to adopt a multilevel and participatory strategy, (2) Formative research leading to the intervention model, (3) The theoretical framework underlying the methodology, (4) Pilot intervention development (Years One and Two), (5) Current program methods and outcome goals, and lastly, (6) Some of the lessons learned, goals achieved, and plans for the future. This descriptive account of building a multilevel intervention aims to serve as a useful guide for others wishing to develop similar approaches, and for theorizing about some of the common challenges involved in this process. PMID:19381797

  12. Variable-speed wind power system with improved energy capture via multilevel conversion

    DOEpatents

    Erickson, Robert W.; Al-Naseem, Osama A.; Fingersh, Lee Jay

    2005-05-31

    A system and method for efficiently capturing electrical energy from a variable-speed generator are disclosed. The system includes a matrix converter using full-bridge, multilevel switch cells, in which semiconductor devices are clamped to a known constant DC voltage of a capacitor. The multilevel matrix converter is capable of generating multilevel voltage wave waveform of arbitrary magnitude and frequencies. The matrix converter can be controlled by using space vector modulation.

  13. Investigation of physical implementation of one-way quantum repeaters with multilevel systems

    NASA Astrophysics Data System (ADS)

    Muralidharan, Sreraman; Zou, Chang-Ling; Li, Linshu; Wen, Jianming; Jiang, Liang

    Error correcting codes of multilevel systems have been shown to be resource efficient for the correction of erasure errors. One way quantum repeaters based on multilevel systems offer ultrafast key generation rates, while consuming lower resources than qubit based schemes (arXiv:1504.08054). On the other hand, they are technologically demanding. Here, we identify the key technological requirements needed for the implementation of quantum repeaters with multilevel systems and propose different experimental techniques that can be used to overcome the difficulties. We propose a generalized Duan-Kimble scheme for the generation of error correcting codes of multilevel systems with time-bin qudits.

  14. Incorporating a multilevel perspective into occupational stress research: theoretical, methodological, and practical implications.

    PubMed

    Bliese, Paul D; Jex, Steve M

    2002-07-01

    In recent years, scholars in organizational behavior and public health have recognized the value of multilevel modeling. This article draws from both of these fields to illustrate the benefits of incorporating a multilevel perspective into the study of occupational stress. The authors identify key multilevel issues in occupational stress in terms of (a) individual-level analyses, (b) group-level analyses, and (c) cross-level analyses. They integrate the theoretical points with statistical models to help illustrate how one can test multilevel occupational stress propositions. PMID:12148957

  15. High-Density, High-Bandwidth, Multilevel Holographic Memory

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin

    2008-01-01

    A proposed holographic memory system would be capable of storing data at unprecedentedly high density, and its data transfer performance in both reading and writing would be characterized by exceptionally high bandwidth. The capabilities of the proposed system would greatly exceed even those of a state-of-the art memory system, based on binary holograms (in which each pixel value represents 0 or 1), that can hold .1 terabyte of data and can support a reading or writing rate as high as 1 Gb/s. The storage capacity of the state-of-theart system cannot be increased without also increasing the volume and mass of the system. However, in principle, the storage capacity could be increased greatly, without significantly increasing the volume and mass, if multilevel holograms were used instead of binary holograms. For example, a 3-bit (8-level) hologram could store 8 terabytes, or an 8-bit (256-level) hologram could store 256 terabytes, in a system having little or no more size and mass than does the state-of-the-art 1-terabyte binary holographic memory. The proposed system would utilize multilevel holograms. The system would include lasers, imaging lenses and other beam-forming optics, a block photorefractive crystal wherein the holograms would be formed, and two multilevel spatial light modulators in the form of commercially available deformable-mirror-device spatial light modulators (DMDSLMs) made for use in high speed input conversion of data up to 12 bits. For readout, the system would also include two arrays of complementary metal oxide/semiconductor (CMOS) photodetectors matching the spatial light modulators. The system would further include a reference-beam sterring device (equivalent of a scanning mirror), containing no sliding parts, that could be either a liquid-crystal phased-array device or a microscopic mirror actuated by a high-speed microelectromechanical system. Time-multiplexing and the multilevel nature of the DMDSLM would be exploited to enable writing

  16. A Medium-Voltage Motor Drive with a Modular Multilevel PWM Inverter Part II. Startup Method and Performance

    NASA Astrophysics Data System (ADS)

    Nishimura, Kazutoshi; Hagiwara, Makoto; Akagi, Hirofumi

    This paper presents a medium-voltage motor drive with a modular multilevel PWM inverter, and focuses on a startup method and its performance. It is formed by six modular arms, each of which consists of a cascaded stack of multiple bidirectional chopper-cells. The frequency of the dominant ac-voltage fluctuation is equal to the motor (inverter) frequency. These fluctuations occur in the dc capacitor of each chopper-cell, and the magnitude of the fluctuation is inversely proportional to the motor frequency. Because of the increased voltage fluctuation in low-frequency regions, the so-called “volt-per-hertz control” cannot be applied in motor starting. The startup method proposed in this paper is suitable for a motor drive with the modular multilevel PWM inverter. It enables the motor to produce a startup torque loaded on the motor at an initial amplitude and a fixed frequency of the inverter while taking into account constraints on the motor current and the ac-voltage fluctuation. The validity of the startup method as well as the startup performance is confirmed by experiment and simulation.

  17. A reliable energy-efficient multi-level routing algorithm for wireless sensor networks using fuzzy Petri nets.

    PubMed

    Yu, Zhenhua; Fu, Xiao; Cai, Yuanli; Vuran, Mehmet C

    2011-01-01

    A reliable energy-efficient multi-level routing algorithm in wireless sensor networks is proposed. The proposed algorithm considers the residual energy, number of the neighbors and centrality of each node for cluster formation, which is critical for well-balanced energy dissipation of the network. In the algorithm, a knowledge-based inference approach using fuzzy Petri nets is employed to select cluster heads, and then the fuzzy reasoning mechanism is used to compute the degree of reliability in the route sprouting tree from cluster heads to the base station. Finally, the most reliable route among the cluster heads can be constructed. The algorithm not only balances the energy load of each node but also provides global reliability for the whole network. Simulation results demonstrate that the proposed algorithm effectively prolongs the network lifetime and reduces the energy consumption. PMID:22163802

  18. Experimental observation of sub-terahertz backward-wave amplification in a multi-level microfabricated slow-wave circuit

    SciTech Connect

    Baik, Chan-Wook Ahn, Ho Young; Kim, Yongsung; Lee, Jooho; Hong, Seogwoo; Lee, Sang Hun; Choi, Jun Hee; Kim, Sunil; Kim, Jong Min; Hwang, Sungwoo; Jeon, So-Yeon; Yu, SeGi; Collins, George; Read, Michael E.; Lawrence Ives, R.

    2015-11-09

    In our earlier paper dealing with dispersion retrieval from ultra-deep, reactive-ion-etched, slow-wave circuits on silicon substrates, it was proposed that splitting high-aspect-ratio circuits into multilevels enabled precise characterization in sub-terahertz frequency regime. This achievement prompted us to investigate beam-wave interaction through a vacuum-sealed integration with a 15-kV, 85-mA, thermionic, electron gun. Our experimental study demonstrates sub-terahertz, backward-wave amplification driven by an external oscillator. The measured output shows a frequency downshift, as well as power amplification, from beam loading even with low beam perveance. This offers a promising opportunity for the development of terahertz radiation sources, based on silicon technologies.

  19. A Reliable Energy-Efficient Multi-Level Routing Algorithm for Wireless Sensor Networks Using Fuzzy Petri Nets

    PubMed Central

    Yu, Zhenhua; Fu, Xiao; Cai, Yuanli; Vuran, Mehmet C.

    2011-01-01

    A reliable energy-efficient multi-level routing algorithm in wireless sensor networks is proposed. The proposed algorithm considers the residual energy, number of the neighbors and centrality of each node for cluster formation, which is critical for well-balanced energy dissipation of the network. In the algorithm, a knowledge-based inference approach using fuzzy Petri nets is employed to select cluster heads, and then the fuzzy reasoning mechanism is used to compute the degree of reliability in the route sprouting tree from cluster heads to the base station. Finally, the most reliable route among the cluster heads can be constructed. The algorithm not only balances the energy load of each node but also provides global reliability for the whole network. Simulation results demonstrate that the proposed algorithm effectively prolongs the network lifetime and reduces the energy consumption. PMID:22163802

  20. Multi-level Monte Carlo finite volume methods for uncertainty quantification of acoustic wave propagation in random heterogeneous layered medium

    NASA Astrophysics Data System (ADS)

    Mishra, S.; Schwab, Ch.; Šukys, J.

    2016-05-01

    We consider the very challenging problem of efficient uncertainty quantification for acoustic wave propagation in a highly heterogeneous, possibly layered, random medium, characterized by possibly anisotropic, piecewise log-exponentially distributed Gaussian random fields. A multi-level Monte Carlo finite volume method is proposed, along with a novel, bias-free upscaling technique that allows to represent the input random fields, generated using spectral FFT methods, efficiently. Combined together with a recently developed dynamic load balancing algorithm that scales to massively parallel computing architectures, the proposed method is able to robustly compute uncertainty for highly realistic random subsurface formations that can contain a very high number (millions) of sources of uncertainty. Numerical experiments, in both two and three space dimensions, illustrating the efficiency of the method are presented.

  1. Multilevel structural equation models for assessing moderation within and across levels of analysis.

    PubMed

    Preacher, Kristopher J; Zhang, Zhen; Zyphur, Michael J

    2016-06-01

    Social scientists are increasingly interested in multilevel hypotheses, data, and statistical models as well as moderation or interactions among predictors. The result is a focus on hypotheses and tests of multilevel moderation within and across levels of analysis. Unfortunately, existing approaches to multilevel moderation have a variety of shortcomings, including conflated effects across levels of analysis and bias due to using observed cluster averages instead of latent variables (i.e., "random intercepts") to represent higher-level constructs. To overcome these problems and elucidate the nature of multilevel moderation effects, we introduce a multilevel structural equation modeling (MSEM) logic that clarifies the nature of the problems with existing practices and remedies them with latent variable interactions. This remedy uses random coefficients and/or latent moderated structural equations (LMS) for unbiased tests of multilevel moderation. We describe our approach and provide an example using the publicly available High School and Beyond data with Mplus syntax in Appendix. Our MSEM method eliminates problems of conflated multilevel effects and reduces bias in parameter estimates while offering a coherent framework for conceptualizing and testing multilevel moderation effects. (PsycINFO Database Record PMID:26651982

  2. The Consequences of Ignoring Individuals' Mobility in Multilevel Growth Models: A Monte Carlo Study

    ERIC Educational Resources Information Center

    Luo, Wen; Kwok, Oi-man

    2012-01-01

    In longitudinal multilevel studies, especially in educational settings, it is fairly common that participants change their group memberships over time (e.g., students switch to different schools). Participant's mobility changes the multilevel data structure from a purely hierarchical structure with repeated measures nested within individuals and…

  3. Multi-Level Modeling of Dyadic Data in Sport Sciences: Conceptual, Statistical, and Practical Issues

    ERIC Educational Resources Information Center

    Gaudreau, Patrick; Fecteau, Marie-Claude; Perreault, Stephane

    2010-01-01

    The goal of this article is to present a series of conceptual, statistical, and practical issues in the modeling of multi-level dyadic data. Distinctions are made between distinguishable and undistinguishable dyads and several types of independent variables modeled at the dyadic level of analysis. Multi-level modeling equations are explained in a…

  4. Sample Size Limits for Estimating Upper Level Mediation Models Using Multilevel SEM

    ERIC Educational Resources Information Center

    Li, Xin; Beretvas, S. Natasha

    2013-01-01

    This simulation study investigated use of the multilevel structural equation model (MLSEM) for handling measurement error in both mediator and outcome variables ("M" and "Y") in an upper level multilevel mediation model. Mediation and outcome variable indicators were generated with measurement error. Parameter and standard…

  5. MULTILEVEL SELECTION WITH KIN AND NON-KIN GROUPS, EXPERIMENTAL RESULTS WITH JAPANESE QUAIL (COTURNIX JAPONICA)

    PubMed Central

    Muir, William M; Bijma, P; Schinckel, A

    2013-01-01

    An experiment was conducted comparing multilevel selection in Japanese quail for 43 days weight and survival with birds housed in either kin (K) or random (R) groups. Multilevel selection significantly reduced mortality (6.6% K vs. 8.5% R) and increased weight (1.30 g/MG K vs. 0.13 g/MG R) resulting in response an order of magnitude greater with Kin than Random. Thus, multilevel selection was effective in reducing detrimental social interactions, which contributed to improved weight gain. The observed rates of response did not differ significantly from expected, demonstrating that current theory is adequate to explain multilevel selection response. Based on estimated genetic parameters, group selection would always be superior to any other combination of multilevel selection. Further, near optimal results could be attained using multilevel selection if 20% of the weight was on the group component regardless of group composition. Thus, in nature the conditions for multilevel selection to be effective in bringing about social change maybe common. In terms of a sustainability of breeding programs, multilevel selection is easy to implement and is expected to give near optimal responses with reduced rates of inbreeding as compared to group selection, the only requirement is that animals be housed in kin groups. PMID:23730755

  6. Toward A Multilevel Theory of Career Development: Advancing Human Resource Development Theory Building

    ERIC Educational Resources Information Center

    Upton, Matthew G.; Egan, Toby Marshall

    2007-01-01

    The established limitations of career development (CD) theory and human resource development (HRD) theory building are addressed by expanding the framing of these issues to multilevel contexts. Multilevel theory building is an approach most effectively aligned with HRD literature and CD and HRD practice realities. An innovative approach multilevel…

  7. Translating the Social-Ecological Perspective into Multilevel Interventions for Family Planning: How Far Are We?

    ERIC Educational Resources Information Center

    Schölmerich, Vera L. N.; Kawachi, Ichiro

    2016-01-01

    Scholars and practitioners frequently make recommendations to develop family planning interventions that are "multilevel." Such interventions take explicit account of the role of environments by incorporating multilevel or social-ecological frameworks into their design and implementation. However, research on how interventions have…

  8. Bayesian Estimation of Graded Response Multilevel Models Using Gibbs Sampling: Formulation and Illustration

    ERIC Educational Resources Information Center

    Natesan, Prathiba; Limbers, Christine; Varni, James W.

    2010-01-01

    The present study presents the formulation of graded response models in the multilevel framework (as nonlinear mixed models) and demonstrates their use in estimating item parameters and investigating the group-level effects for specific covariates using Bayesian estimation. The graded response multilevel model (GRMM) combines the formulation of…

  9. The Impact of Sample Size and Other Factors When Estimating Multilevel Logistic Models

    ERIC Educational Resources Information Center

    Schoeneberger, Jason A.

    2016-01-01

    The design of research studies utilizing binary multilevel models must necessarily incorporate knowledge of multiple factors, including estimation method, variance component size, or number of predictors, in addition to sample sizes. This Monte Carlo study examined the performance of random effect binary outcome multilevel models under varying…

  10. Translating the Socio-Ecological Perspective into Multilevel Interventions: Gaps between Theory and Practice

    ERIC Educational Resources Information Center

    Schölmerich, Vera L. N.; Kawachi, Ichiro

    2016-01-01

    Multilevel interventions are inspired by socio-ecological models, and seek to create change on various levels--for example by increasing the health literacy of individuals as well as modifying the social norms within a community. Despite becoming a buzzword in public health, actual multilevel interventions remain scarce. In this commentary, we…

  11. Teaching ESL in a Multilevel Classroom. Adult Education Series #13. Refugee Education Guide.

    ERIC Educational Resources Information Center

    Center for Applied Linguistics, Washington, DC. Language and Orientation Resource Center.

    Adult refugee English as a second language (ESL) programs are often mandated to serve all who sign up for instruction, a requirement that results in multilevel classes. This guide describes and discusses this and other factors which contribute to the existence of multilevel and/or heterogeneous classes, and provides some practical approaches and…

  12. Fitting Multilevel Models with Ordinal Outcomes: Performance of Alternative Specifications and Methods of Estimation

    ERIC Educational Resources Information Center

    Bauer, Daniel J.; Sterba, Sonya K.

    2011-01-01

    Previous research has compared methods of estimation for fitting multilevel models to binary data, but there are reasons to believe that the results will not always generalize to the ordinal case. This article thus evaluates (a) whether and when fitting multilevel linear models to ordinal outcome data is justified and (b) which estimator to employ…

  13. Analyzing Faculty Workload Data Using Multilevel Modeling. AIR 2000 Annual Forum Paper.

    ERIC Educational Resources Information Center

    Porter, Stephen R.; Umbach, Paul

    This study used the multilevel modeling method to analyze the research productivity of 1,104 tenured or tenure track faculty from the 1993 National Study of Postsecondary Faculty. The study compared statistical and substantive results of multilevel modeling (or hierarchical linear modeling) to the traditional regression approach. Two dependent…

  14. Validation of Multilevel Constructs: Validation Methods and Empirical Findings for the EDI

    ERIC Educational Resources Information Center

    Forer, Barry; Zumbo, Bruno D.

    2011-01-01

    The purposes of this paper are to highlight the foundations of multilevel construct validation, describe two methodological approaches and associated analytic techniques, and then apply these approaches and techniques to the multilevel construct validation of a widely-used school readiness measure called the Early Development Instrument (EDI;…

  15. The research of multilevel transistor inverter for converting energy of solar panels

    NASA Astrophysics Data System (ADS)

    Taissariyeva, K. N.; Issembergenov, N. T.

    2015-09-01

    This article considers multilevel transistor inverter for converting energy of solar panels into electroenergy. The output of multilevel transistor inverter produces the voltage of almost sinusoidal form. The primary objective of this inverter is to transform solar energy into electroenergy of industrial frequency. The analysis of received output curves of voltage for sinusoidality has been conducted.

  16. The Effects of Autonomy and Empowerment on Employee Turnover: Test of a Multilevel Model in Teams

    ERIC Educational Resources Information Center

    Liu, Dong; Zhang, Shu; Wang, Lei; Lee, Thomas W.

    2011-01-01

    Extending research on voluntary turnover in the team setting, this study adopts a multilevel self-determination theoretical approach to examine the unique roles of individual and social-contextual motivational precursors, autonomy orientation and autonomy support, in reducing team member voluntary turnover. Analysis of multilevel time-lagged data…

  17. Using Visual Analysis to Evaluate and Refine Multilevel Models of Single-Case Studies

    ERIC Educational Resources Information Center

    Baek, Eun Kyeng; Petit-Bois, Merlande; Van den Noortgate, Wim; Beretvas, S. Natasha; Ferron, John M.

    2016-01-01

    In special education, multilevel models of single-case research have been used as a method of estimating treatment effects over time and across individuals. Although multilevel models can accurately summarize the effect, it is known that if the model is misspecified, inferences about the effects can be biased. Concern with the potential for model…

  18. Data Aggregation in Multilevel Analysis: A Review of Conceptual and Statistical Issues

    ERIC Educational Resources Information Center

    Dixon, Marlene A.; Cunningham, George B.

    2006-01-01

    Understanding that the behavior of people takes place within a context, over the past 20 years research in education and the sport sciences has witnessed an increasing development of multilevel frameworks that are both conceptually and methodologically sound. Despite these advances, the use of multilevel models and research designs in education…

  19. Effects of Teacher-Student Relationships on Peer Harassment: A Multilevel Study

    ERIC Educational Resources Information Center

    Lucas-Molina, Beatriz; Williamson, Ariel A.; Pulido, Rosa; Pérez-Albéniz, Alicia

    2015-01-01

    Peer harassment is a major social problem affecting children and adolescents internationally. Much research has focused on student-to-student harassment from either an individual or a multilevel perspective. There is a paucity of multilevel research on students' relationships with the classroom teacher. The purpose of this study was to use a…

  20. Ultrafast effective multilevel atom method for primordial hydrogen recombination

    SciTech Connect

    Ali-Haiemoud, Yacine; Hirata, Christopher M.

    2010-09-15

    Cosmological hydrogen recombination has recently been the subject of renewed attention because of its importance for predicting the power spectrum of cosmic microwave background anisotropies. It has become clear that it is necessary to account for a large number n > or approx. 100 of energy shells of the hydrogen atom, separately following the angular momentum substates in order to obtain sufficiently accurate recombination histories. However, the multilevel atom codes that follow the populations of all these levels are computationally expensive, limiting recent analyses to only a few points in parameter space. In this paper, we present a new method for solving the multilevel atom recombination problem, which splits the problem into a computationally expensive atomic physics component that is independent of the cosmology and an ultrafast cosmological evolution component. The atomic physics component follows the network of bound-bound and bound-free transitions among excited states and computes the resulting effective transition rates for the small set of 'interface' states radiatively connected to the ground state. The cosmological evolution component only follows the populations of the interface states. By pretabulating the effective rates, we can reduce the recurring cost of multilevel atom calculations by more than 5 orders of magnitude. The resulting code is fast enough for inclusion in Markov chain Monte Carlo parameter estimation algorithms. It does not yet include the radiative transfer or high-n two-photon processes considered in some recent papers. Further work on analytic treatments for these effects will be required in order to produce a recombination code usable for Planck data analysis.

  1. Evolution of fairness in the dictator game by multilevel selection.

    PubMed

    Schank, Jeffrey C; Smaldino, Paul E; Miller, Matt L

    2015-10-01

    The most perplexing experimental results on fairness come from the dictator game where one of two players, the dictator, decides how to divide a resource with an anonymous player. The dictator, acting self-interestedly, should offer nothing to the anonymous second player, but in experimental studies, dictators offer much more than nothing. We developed a multilevel selection model to explain why people offer more than nothing in the dictator game. We show that fairness can evolve when population structure emerges from the aggregation and limited dispersal of offspring. We begin with an analytical model that shows how fair behavior can benefit groups by minimizing within-group variance in resources and thereby increasing group fitness. To investigate the generality of this result, we developed an agent-based model with agents that have no information about other agents. We allowed agents to aggregate into groups and evolve different levels of fairness by playing the dictator game for resources to reproduce. This allowed multilevel selection to emerge from the spatiotemporal properties of individual agents. We found that the population structure that emerged under low population densities was most conducive to the evolution of fairness, which is consistent with group selection as a major evolutionary force. We also found that fairness only evolves if resources are not too scarce relative to the lifespan of agents. We conclude that the evolution of fairness could evolve under multilevel selection. Thus, our model provides a novel explanation for the results of dictator game experiments, in which participants often fairly split a resource rather than keeping it all for themselves. PMID:26141644

  2. Multilevel Effects of Wealth on Women's Contraceptive Use in Mozambique

    PubMed Central

    Dias, José G.; de Oliveira, Isabel Tiago

    2015-01-01

    Objective This paper analyzes the impact of wealth on the use of contraception in Mozambique unmixing the contextual effects due to community wealth from the individual effects associated with the women's situation within the community of residence. Methods Data from the 2011 Mozambican Demographic and Health Survey on women who are married or living together are analyzed for the entire country and also for the rural and urban areas separately. We used single level and multilevel probit regression models. Findings A single level probit regression reveals that region, religion, age, previous fertility, education, and wealth impact contraceptive behavior. The multilevel analysis shows that average community wealth and the women’s relative socioeconomic position within the community have significant positive effects on the use of modern contraceptives. The multilevel framework proved to be necessary in rural settings but not relevant in urban areas. Moreover, the contextual effects due to community wealth are greater in rural than in urban areas and this feature is associated with the higher socioeconomic heterogeneity within the richest communities. Conclusion This analysis highlights the need for the studies on contraceptive behavior to specifically address the individual and contextual effects arising from the poverty-wealth dimension in rural and urban areas separately. The inclusion in a particular community of residence is not relevant in urban areas, but it is an important feature in rural areas. Although the women's individual position within the community of residence has a similar effect on contraceptive adoption in rural and urban settings, the impact of community wealth is greater in rural areas and smaller in urban areas. PMID:25786228

  3. Ultrafast effective multilevel atom method for primordial hydrogen recombination

    NASA Astrophysics Data System (ADS)

    Ali-Haïmoud, Yacine; Hirata, Christopher M.

    2010-09-01

    Cosmological hydrogen recombination has recently been the subject of renewed attention because of its importance for predicting the power spectrum of cosmic microwave background anisotropies. It has become clear that it is necessary to account for a large number n≳100 of energy shells of the hydrogen atom, separately following the angular momentum substates in order to obtain sufficiently accurate recombination histories. However, the multilevel atom codes that follow the populations of all these levels are computationally expensive, limiting recent analyses to only a few points in parameter space. In this paper, we present a new method for solving the multilevel atom recombination problem, which splits the problem into a computationally expensive atomic physics component that is independent of the cosmology and an ultrafast cosmological evolution component. The atomic physics component follows the network of bound-bound and bound-free transitions among excited states and computes the resulting effective transition rates for the small set of “interface” states radiatively connected to the ground state. The cosmological evolution component only follows the populations of the interface states. By pretabulating the effective rates, we can reduce the recurring cost of multilevel atom calculations by more than 5 orders of magnitude. The resulting code is fast enough for inclusion in Markov chain Monte Carlo parameter estimation algorithms. It does not yet include the radiative transfer or high-n two-photon processes considered in some recent papers. Further work on analytic treatments for these effects will be required in order to produce a recombination code usable for Planck data analysis.

  4. Multilevel distillation of magic states for quantum computing

    NASA Astrophysics Data System (ADS)

    Jones, Cody

    2013-04-01

    We develop a procedure for distilling magic states used in universal quantum computing that requires substantially fewer initial resources than prior schemes. Our distillation circuit is based on a family of concatenated quantum codes that possess a transversal Hadamard operation, enabling each of these codes to distill the eigenstate of the Hadamard operator. A crucial result of this design is that low-fidelity magic states can be consumed to purify other high-fidelity magic states to even higher fidelity, which we call multilevel distillation. When distilling in the asymptotic regime of infidelity ɛ→0 for each input magic state, the number of input magic states consumed on average to yield an output state with infidelity O(ɛ2r) approaches 2r+1, which comes close to saturating the conjectured bound in another investigation [Bravyi and Haah, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.86.052329 86, 052329 (2012)]. We show numerically that there exist multilevel protocols such that the average number of magic states consumed to distill from error rate ɛin=0.01 to ɛout in the range 10-5-10-40 is about 14log10(1/ɛout)-40; the efficiency of multilevel distillation dominates all other reported protocols when distilling Hadamard magic states from initial infidelity 0.01 to any final infidelity below 10-7. These methods are an important advance for magic-state distillation circuits in high-performance quantum computing and provide insight into the limitations of nearly resource-optimal quantum error correction.

  5. Predicting Group-Level Outcome Variables from Variables Measured at the Individual Level: A Latent Variable Multilevel Model

    ERIC Educational Resources Information Center

    Croon, Marcel A.; van Veldhoven, Marc J. P. M.

    2007-01-01

    In multilevel modeling, one often distinguishes between macro-micro and micro-macro situations. In a macro-micro multilevel situation, a dependent variable measured at the lower level is predicted or explained by variables measured at that lower or a higher level. In a micro-macro multilevel situation, a dependent variable defined at the higher…

  6. A Methodological Review of Statistical Methods for Handling Multilevel Non-Nested Longitudinal Data in Educational Research

    ERIC Educational Resources Information Center

    Sun, Shuyan; Pan, Wei

    2014-01-01

    As applications of multilevel modelling in educational research increase, researchers realize that multilevel data collected in many educational settings are often not purely nested. The most common multilevel non-nested data structure is one that involves student mobility in longitudinal studies. This article provides a methodological review of…

  7. A multilevel method for conductive-radiative heat transfer

    SciTech Connect

    Banoczi, J.M.; Kelley, C.T.

    1996-12-31

    We present a fast multilevel algorithm for the solution of a system of nonlinear integro-differential equations that model steady-state combined radiative-conductive heat transfer. The equations can be formulated as a compact fixed point problem with a fixed point map that requires both a solution of the linear transport equation and the linear heat equation for its evaluation. We use fast transport solvers developed by the second author, to construct an efficient evaluation of the fixed point map and then apply the Atkinson-Brakhage, method, with Newton-GMRES as the coarse mesh solver, to the full nonlinear system.

  8. Multilevel algorithm for flow observables in gauge theories

    NASA Astrophysics Data System (ADS)

    García Vera, Miguel; Schaefer, Stefan

    2016-04-01

    We study the possibility of using multilevel algorithms for the computation of correlation functions of gradient flow observables. For each point in the correlation function, an approximate flow is defined which depends only on links in a subset of the lattice. Together with a local action, this allows for independent updates and consequently a convergence of the Monte Carlo process faster than the inverse square root of the number of measurements. We demonstrate the feasibility of this idea in the correlation functions of the topological charge and the energy density.

  9. Ultraviolet stellar spectral classification using a multilevel tree neural network

    NASA Astrophysics Data System (ADS)

    Gulati, R. K.; Gupta, R.; Gothoskar, P.; Khobragade, S.

    Here we present a pattern classification technique based on an Artificial Neural Network (ANN) in a multi-level tree configuration to classify ultraviolet stellar spectra from the IUE Low-Dispersion Spectra Reference Atlas. Preliminary results of this technique show that 94% of the spectra have been classified correctly with an accuracy of one sub-class. A conventional overlineχ2 minimization scheme has also been applied to the data to compare the classification obtained from these schemes with that of the IUE catalog classification.

  10. Macro-actor execution on multilevel data-driven architectures

    SciTech Connect

    Gaudiot, J.L.; Najjar, W.

    1988-12-31

    The data-flow model of computation brings to multiprocessors high programmability at the expense of increased overhead. Applying the model at a higher level leads to better performance but also introduces loss of parallelism. We demonstrate here syntax directed program decomposition methods for the creation of large macro-actors in numerical algorithms. In order to alleviate some of the problems introduced by the lower resolution interpretation, we describe a multi-level of resolution and analyze the requirements for its actual hardware and software integration.

  11. NOVA: A new multi-level logic simulator

    NASA Technical Reports Server (NTRS)

    Miles, L.; Prins, P.; Cameron, K.; Shovic, J.

    1990-01-01

    A new logic simulator that was developed at the NASA Space Engineering Research Center for VLSI Design was described. The simulator is multi-level, being able to simulate from the switch level through the functional model level. NOVA is currently in the Beta test phase and was used to simulate chips designed for the NASA Space Station and the Explorer missions. A new algorithm was devised to simulate bi-directional pass transistors and a preliminary version of the algorithm is presented. The usage of functional models in NOVA is also described and performance figures are presented.

  12. Efficient multilevel eigensolvers with applications to data analysis tasks.

    PubMed

    Kushnir, Dan; Galun, Meirav; Brandt, Achi

    2010-08-01

    Multigrid solvers proved very efficient for solving massive systems of equations in various fields. These solvers are based on iterative relaxation schemes together with the approximation of the "smooth" error function on a coarser level (grid). We present two efficient multilevel eigensolvers for solving massive eigenvalue problems that emerge in data analysis tasks. The first solver, a version of classical algebraic multigrid (AMG), is applied to eigenproblems arising in clustering, image segmentation, and dimensionality reduction, demonstrating an order of magnitude speedup compared to the popular Lanczos algorithm. The second solver is based on a new, much more accurate interpolation scheme. It enables calculating a large number of eigenvectors very inexpensively. PMID:20558872

  13. Multi-level Full Virtualization of Power Management

    NASA Astrophysics Data System (ADS)

    Liu, Yongpeng; Chi, Wanqing; Liu, Yongyan

    Virtual machine technique is employed to improve system utilization and energy efficiency. However, isolation effect of virtualization imposes challenges to power management. A multi-level power behavior statistic framework is introduced to support power profiling of virtual device, virtual machine and host. Power management mechanisms are virtualized to map power management operations between virtual device and physical device. The power consumption of a virtual device is virtualized according to its performance share from the physical device. The experiments demonstrated that our power management virtualization solution has negligible decline of system performance.

  14. A multilevel optimization of large-scale dynamic systems

    NASA Technical Reports Server (NTRS)

    Siljak, D. D.; Sundareshan, M. K.

    1976-01-01

    A multilevel feedback control scheme is proposed for optimization of large-scale systems composed of a number of (not necessarily weakly coupled) subsystems. Local controllers are used to optimize each subsystem, ignoring the interconnections. Then, a global controller may be applied to minimize the effect of interconnections and improve the performance of the overall system. At the cost of suboptimal performance, this optimization strategy ensures invariance of suboptimality and stability of the systems under structural perturbations whereby subsystems are disconnected and again connected during operation.

  15. Performance Analysis of Multilevel Parallel Applications on Shared Memory Architectures

    NASA Technical Reports Server (NTRS)

    Jost, Gabriele; Jin, Haoqiang; Labarta, Jesus; Gimenez, Judit; Caubet, Jordi; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    In this paper we describe how to apply powerful performance analysis techniques to understand the behavior of multilevel parallel applications. We use the Paraver/OMPItrace performance analysis system for our study. This system consists of two major components: The OMPItrace dynamic instrumentation mechanism, which allows the tracing of processes and threads and the Paraver graphical user interface for inspection and analyses of the generated traces. We describe how to use the system to conduct a detailed comparative study of a benchmark code implemented in five different programming paradigms applicable for shared memory

  16. Bounds on Block Error Probability for Multilevel Concatenated Codes

    NASA Technical Reports Server (NTRS)

    Lin, Shu; Moorthy, Hari T.; Stojanovic, Diana

    1996-01-01

    Maximum likelihood decoding of long block codes is not feasable due to large complexity. Some classes of codes are shown to be decomposable into multilevel concatenated codes (MLCC). For these codes, multistage decoding provides good trade-off between performance and complexity. In this paper, we derive an upper bound on the probability of block error for MLCC. We use this bound to evaluate difference in performance for different decompositions of some codes. Examples given show that a significant reduction in complexity can be achieved when increasing number of stages of decoding. Resulting performance degradation varies for different decompositions. A guideline is given for finding good m-level decompositions.

  17. International students' enrollment in IPTA by using multilevel analysis

    NASA Astrophysics Data System (ADS)

    Wai, Phoong Seuk; Ismail, Mohd Tahir; Karim, Samsul Ariffin Abdul

    2012-09-01

    The increases of demand on knowledge-based and production-based market force the growth of higher education. International students' enrollment contributes to economic growth and increase country's income, university reputation and name; promote the competitive of education and training markets. This paper used multilevel analysis to study the international students' enrollment in Malaysia public university. Student's background variables and institution background variables were study in this paper and the relationship among them also been investigated. Result shows that institution type is a significance factor on international students' enrollment in Malaysia public university.

  18. Laminoplasty Techniques for the Treatment of Multilevel Cervical Stenosis

    PubMed Central

    Mitsunaga, Lance K.; Klineberg, Eric O.; Gupta, Munish C.

    2012-01-01

    Laminoplasty is one surgical option for cervical spondylotic myelopathy. It was developed to avoid the significant risk of complications associated with alternative surgical options such as anterior decompression and fusion and laminectomy with or without posterior fusion. Various laminoplasty techniques have been described. All of these variations are designed to reposition the laminae and expand the spinal canal while retaining the dorsal elements to protect the dura from scar formation and to preserve postoperative cervical stability and alignment. With the right surgical indications, reliable results can be expected with laminoplasty in treating patients with multilevel cervical myelopathy. PMID:22496982

  19. A multilevel approach for minimum weight structural design including local and system buckling constraints

    NASA Technical Reports Server (NTRS)

    Schmit, L. A., Jr.; Ramanathan, R. K.

    1977-01-01

    A rational multilevel approach for minimum weight structural design of truss and wing structures including local and system buckling constraints is presented. Overall proportioning of the structure is achieved at the system level subject to strength, displacement and system buckling constraints, while the detailed component designs are carried out separately at the component level satisfying local buckling constraints. Total structural weight is taken to be the objective function at the system level while employing the change in the equivalent system stiffness of the component as the component level objective function. Finite element analysis is used to predict static response while system buckling behavior is handled by incorporating a geometric stiffness matrix capability. Buckling load factors and the corresponding mode shapes are obtained by solving the eigenvalue problem associated with the assembled elastic stiffness and geometric stiffness matrices for the structural system. At the component level various local buckling failure modes are guarded against using semi-empirical formulas. Mathematical programming techniques are employed at both the system and component level.

  20. Synergistic High Charge-Storage Capacity for Multi-level Flexible Organic Flash Memory

    NASA Astrophysics Data System (ADS)

    Kang, Minji; Khim, Dongyoon; Park, Won-Tae; Kim, Jihong; Kim, Juhwan; Noh, Yong-Young; Baeg, Kang-Jun; Kim, Dong-Yu

    2015-07-01

    Electret and organic floating-gate memories are next-generation flash storage mediums for printed organic complementary circuits. While each flash memory can be easily fabricated using solution processes on flexible plastic substrates, promising their potential for on-chip memory organization is limited by unreliable bit operation and high write loads. We here report that new architecture could improve the overall performance of organic memory, and especially meet high storage for multi-level operation. Our concept depends on synergistic effect of electrical characterization in combination with a polymer electret (poly(2-vinyl naphthalene) (PVN)) and metal nanoparticles (Copper). It is distinguished from mostly organic nano-floating-gate memories by using the electret dielectric instead of general tunneling dielectric for additional charge storage. The uniform stacking of organic layers including various dielectrics and poly(3-hexylthiophene) (P3HT) as an organic semiconductor, followed by thin-film coating using orthogonal solvents, greatly improve device precision despite easy and fast manufacture. Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] as high-k blocking dielectric also allows reduction of programming voltage. The reported synergistic organic memory devices represent low power consumption, high cycle endurance, high thermal stability and suitable retention time, compared to electret and organic nano-floating-gate memory devices.

  1. Synergistic High Charge-Storage Capacity for Multi-level Flexible Organic Flash Memory

    PubMed Central

    Kang, Minji; Khim, Dongyoon; Park, Won-Tae; Kim, Jihong; Kim, Juhwan; Noh, Yong-Young; Baeg, Kang-Jun; Kim, Dong-Yu

    2015-01-01

    Electret and organic floating-gate memories are next-generation flash storage mediums for printed organic complementary circuits. While each flash memory can be easily fabricated using solution processes on flexible plastic substrates, promising their potential for on-chip memory organization is limited by unreliable bit operation and high write loads. We here report that new architecture could improve the overall performance of organic memory, and especially meet high storage for multi-level operation. Our concept depends on synergistic effect of electrical characterization in combination with a polymer electret (poly(2-vinyl naphthalene) (PVN)) and metal nanoparticles (Copper). It is distinguished from mostly organic nano-floating-gate memories by using the electret dielectric instead of general tunneling dielectric for additional charge storage. The uniform stacking of organic layers including various dielectrics and poly(3-hexylthiophene) (P3HT) as an organic semiconductor, followed by thin-film coating using orthogonal solvents, greatly improve device precision despite easy and fast manufacture. Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] as high-k blocking dielectric also allows reduction of programming voltage. The reported synergistic organic memory devices represent low power consumption, high cycle endurance, high thermal stability and suitable retention time, compared to electret and organic nano-floating-gate memory devices. PMID:26201747

  2. Complex-valued multistate associative memory with nonlinear multilevel functions for gray-level image reconstruction.

    PubMed

    Tanaka, Gouhei; Aihara, Kazuyuki

    2009-09-01

    A widely used complex-valued activation function for complex-valued multistate Hopfield networks is revealed to be essentially based on a multilevel step function. By replacing the multilevel step function with other multilevel characteristics, we present two alternative complex-valued activation functions. One is based on a multilevel sigmoid function, while the other on a characteristic of a multistate bifurcating neuron. Numerical experiments show that both modifications to the complex-valued activation function bring about improvements in network performance for a multistate associative memory. The advantage of the proposed networks over the complex-valued Hopfield networks with the multilevel step function is more outstanding when a complex-valued neuron represents a larger number of multivalued states. Further, the performance of the proposed networks in reconstructing noisy 256 gray-level images is demonstrated in comparison with other recent associative memories to clarify their advantages and disadvantages. PMID:19643705

  3. A Multi-Level Parallelization Concept for High-Fidelity Multi-Block Solvers

    NASA Technical Reports Server (NTRS)

    Hatay, Ferhat F.; Jespersen, Dennis C.; Guruswamy, Guru P.; Rizk, Yehia M.; Byun, Chansup; Gee, Ken; VanDalsem, William R. (Technical Monitor)

    1997-01-01

    The integration of high-fidelity Computational Fluid Dynamics (CFD) analysis tools with the industrial design process benefits greatly from the robust implementations that are transportable across a wide range of computer architectures. In the present work, a hybrid domain-decomposition and parallelization concept was developed and implemented into the widely-used NASA multi-block Computational Fluid Dynamics (CFD) packages implemented in ENSAERO and OVERFLOW. The new parallel solver concept, PENS (Parallel Euler Navier-Stokes Solver), employs both fine and coarse granularity in data partitioning as well as data coalescing to obtain the desired load-balance characteristics on the available computer platforms. This multi-level parallelism implementation itself introduces no changes to the numerical results, hence the original fidelity of the packages are identically preserved. The present implementation uses the Message Passing Interface (MPI) library for interprocessor message passing and memory accessing. By choosing an appropriate combination of the available partitioning and coalescing capabilities only during the execution stage, the PENS solver becomes adaptable to different computer architectures from shared-memory to distributed-memory platforms with varying degrees of parallelism. The PENS implementation on the IBM SP2 distributed memory environment at the NASA Ames Research Center obtains 85 percent scalable parallel performance using fine-grain partitioning of single-block CFD domains using up to 128 wide computational nodes. Multi-block CFD simulations of complete aircraft simulations achieve 75 percent perfect load-balanced executions using data coalescing and the two levels of parallelism. SGI PowerChallenge, SGI Origin 2000, and a cluster of workstations are the other platforms where the robustness of the implementation is tested. The performance behavior on the other computer platforms with a variety of realistic problems will be included as this on

  4. More on the genetical theory of multilevel selection.

    PubMed

    Gardner, A

    2015-09-01

    In my article The genetical theory of multilevel selection, I provided a synthesis of the theory of multilevel selection (MLS) and the theory of natural selection in class-structured populations. I framed this synthesis within Fisher's genetical paradigm, taking a strictly genetical approach to traits and fitness. I showed that this resolves a number of long-standing conceptual problems that have plagued the MLS literature, including the issues of 'aggregate' vs. 'emergent' group traits, 'collective fitness1 ' vs. 'collective fitness2 ' and 'MLS1' vs. 'MLS2 '. In his commentary, Goodnight suggests this theoretical and conceptual synthesis is flawed in several respects. Here, I show this is incorrect, by: reiterating the theoretical and conceptual goals of my synthesis; clarifying that my genetical approach to traits is necessary for a proper analysis of the action of MLS independently of non-Darwinian factors; emphasizing that the Price-Hamilton approach to MLS provides a consistent, useful and conceptually superior theoretical framework; and explaining the role of reproductive value in the study of natural selection in class-structured populations. I also show that Goodnight's contextual analysis treatment of MLS in a class-structured population is mathematically, biologically and conceptually inadequate. PMID:26264884

  5. Multilevel Summation of Electrostatic Potentials Using Graphics Processing Units*

    PubMed Central

    Hardy, David J.; Stone, John E.; Schulten, Klaus

    2009-01-01

    Physical and engineering practicalities involved in microprocessor design have resulted in flat performance growth for traditional single-core microprocessors. The urgent need for continuing increases in the performance of scientific applications requires the use of many-core processors and accelerators such as graphics processing units (GPUs). This paper discusses GPU acceleration of the multilevel summation method for computing electrostatic potentials and forces for a system of charged atoms, which is a problem of paramount importance in biomolecular modeling applications. We present and test a new GPU algorithm for the long-range part of the potentials that computes a cutoff pair potential between lattice points, essentially convolving a fixed 3-D lattice of “weights” over all sub-cubes of a much larger lattice. The implementation exploits the different memory subsystems provided on the GPU to stream optimally sized data sets through the multiprocessors. We demonstrate for the full multilevel summation calculation speedups of up to 26 using a single GPU and 46 using multiple GPUs, enabling the computation of a high-resolution map of the electrostatic potential for a system of 1.5 million atoms in under 12 seconds. PMID:20161132

  6. Multilevel Latent Class Models with Dirichlet Mixing Distribution

    PubMed Central

    Di, Chong-Zhi; Bandeen-Roche, Karen

    2010-01-01

    Summary Latent class analysis (LCA) and latent class regression (LCR) are widely used for modeling multivariate categorical outcomes in social science and biomedical studies. Standard analyses assume data of different respondents to be mutually independent, excluding application of the methods to familial and other designs in which participants are clustered. In this paper, we consider multilevel latent class models, in which subpopulation mixing probabilities are treated as random effects that vary among clusters according to a common Dirichlet distribution. We apply the Expectation-Maximization (EM) algorithm for model fitting by maximum likelihood (ML). This approach works well, but is computationally intensive when either the number of classes or the cluster size is large. We propose a maximum pairwise likelihood (MPL) approach via a modified EM algorithm for this case. We also show that a simple latent class analysis, combined with robust standard errors, provides another consistent, robust, but less efficient inferential procedure. Simulation studies suggest that the three methods work well in finite samples, and that the MPL estimates often enjoy comparable precision as the ML estimates. We apply our methods to the analysis of comorbid symptoms in the Obsessive Compulsive Disorder study. Our models' random effects structure has more straightforward interpretation than those of competing methods, thus should usefully augment tools available for latent class analysis of multilevel data. PMID:20560936

  7. Fuzzy set applications in engineering optimization: Multilevel fuzzy optimization

    NASA Technical Reports Server (NTRS)

    Diaz, Alejandro R.

    1989-01-01

    A formulation for multilevel optimization with fuzzy objective functions is presented. With few exceptions, formulations for fuzzy optimization have dealt with a one-level problem in which the objective is the membership function of a fuzzy set formed by the fuzzy intersection of other sets. In the problem examined here, the goal set G is defined in a more general way, using an aggregation operator H that allows arbitrary combinations of set operations (union, intersection, addition) on the individual sets Gi. This is a straightforward extension of the standard form, but one that makes possible the modeling of interesting evaluation strategies. A second, more important departure from the standard form will be the construction of a multilevel problem analogous to the design decomposition problem in optimization. This arrangement facilitates the simulation of a system design process in which different components of the system are designed by different teams, and different levels of design detail become relevant at different time stages in the process: global design features early, local features later in the process.

  8. Performance analysis of a multilevel coded modulation system

    NASA Astrophysics Data System (ADS)

    Kofman, Yosef; Zehavi, Ephraim; Shamai, Shlomo

    1994-02-01

    A modified version of the multilevel coded modulation scheme of Imai & Hirakawa is presented and analyzed. In the transmitter, the outputs of the component codes are bit interleaved prior to mapping into 8-PSK channel signals. A multistage receiver is considered, in which the output amplitudes of the Gaussian channel are soft limited before entering the second and third stage decoders. Upper bounds and Gaussian approximations for the bit error probability of every component code, which take into account errors in previously decoded stages, are presented. Aided by a comprehensive computer simulation, it is demonstrated in a specific example that the addition of the interleaver and soft limiter in the third stage improves its performance by 1.1 dB at a bit error probability of 10(exp -5), and that the multilevel scheme improves on an Ungerboeck's code with the same decoding complexity. The rate selection of the component codes is also considered and a simple selection rule, based on information theoretic arguments, is provided.

  9. Negative voltage bandgap reference with multilevel curvature compensation technique

    NASA Astrophysics Data System (ADS)

    Xi, Liu; Qian, Liu; Xiaoshi, Jin; Yongrui, Zhao; Lee, Jong-Ho

    2016-05-01

    A novel high-order curvature compensation negative voltage bandgap reference (NBGR) based on a novel multilevel compensation technique is introduced. Employing an exponential curvature compensation (ECC) term with many high order terms in itself, in a lower temperature range (TR) and a multilevel curvature compensation (MLCC) term in a higher TR, a flattened and better effect of curvature compensation over the TR of 165 °C (‑40 to 125 °C) is realised. The MLCC circuit adds two convex curves by using two sub-threshold operated NMOS. The proposed NBGR implemented in the Central Semiconductor Manufacturing Corporation (CSMC) 0.5 μm BCD technology demonstrates an accurate voltage of ‑1.183 V with a temperature coefficient (TC) as low as 2.45 ppm/°C over the TR of 165 °C at a ‑5.0 V power supply; the line regulation is 3 mV/V from a ‑5 to ‑2 V supply voltage. The active area of the presented NBGR is 370 × 180 μm2. Project supported by the Fund of Liaoning Province Education Department (No. L2013045).

  10. Empowering leaders optimize working conditions for engagement: a multilevel study.

    PubMed

    Tuckey, Michelle R; Bakker, Arnold B; Dollard, Maureen F

    2012-01-01

    Using a multilevel framework, this study examined the role of empowering leadership at the group level by fire brigade captains in facilitating the individual level motivational processes that underpin work engagement in volunteer firefighters. Anonymous mail surveys were completed by 540 volunteer firefighters from 68 fire brigades and, separately, by 68 brigade captains. As predicted on the basis of the Job Demands-Resources model, increased levels of cognitive demands and cognitive resources partially mediated the relationship between empowering leadership and work engagement. In a three-way Leadership × Demands × Resources interaction, empowering leadership also had the effect of optimizing working conditions for engagement by strengthening the positive effect of a work context in which both cognitive demands and cognitive resources were high. Our findings shed light on a process through which leaders can empower workers and enhance well-being: via their influence on and interaction with the work environment. They also underscore the need to examine work engagement from a multilevel theoretical perspective. PMID:22409390

  11. Multilevel selection theory and evidence: a critique of Gardner, 2015.

    PubMed

    Goodnight, C J

    2015-09-01

    Gardner (2015) recently developed a model of a 'Genetical Theory of Multilevel Selection, which is a thoughtfully developed, but flawed model. The model's flaws appear to be symptomatic of common misunderstandings of the multi level selection (MLS) literature and the recent quantitative genetic literature. I use Gardner's model as a guide for highlighting how the MLS literature can address the misconceptions found in his model, and the kin selection literature in general. I discuss research on the efficacy of group selection, the roll of indirect genetic effects in affecting the response to selection and the heritability of group-level traits. I also discuss why the Price multilevel partition should not be used to partition MLS, and why contextual analysis and, by association, direct fitness are appropriate for partitioning MLS. Finally, I discuss conceptual issues around questions concerning the level at which fitness is measured, the units of selection, and I present a brief outline of a model of selection in class-structured populations. I argue that the results derived from the MLS research tradition can inform kin selection research and models, and provide insights that will allow researchers to avoid conceptual flaws such as those seen in the Gardner model. PMID:26265012

  12. Multi-Level Bitmap Indexes for Flash Memory Storage

    SciTech Connect

    Wu, Kesheng; Madduri, Kamesh; Canon, Shane

    2010-07-23

    Due to their low access latency, high read speed, and power-efficient operation, flash memory storage devices are rapidly emerging as an attractive alternative to traditional magnetic storage devices. However, tests show that the most efficient indexing methods are not able to take advantage of the flash memory storage devices. In this paper, we present a set of multi-level bitmap indexes that can effectively take advantage of flash storage devices. These indexing methods use coarsely binned indexes to answer queries approximately, and then use finely binned indexes to refine the answers. Our new methods read significantly lower volumes of data at the expense of an increased disk access count, thus taking full advantage of the improved read speed and low access latency of flash devices. To demonstrate the advantage of these new indexes, we measure their performance on a number of storage systems using a standard data warehousing benchmark called the Set Query Benchmark. We observe that multi-level strategies on flash drives are up to 3 times faster than traditional indexing strategies on magnetic disk drives.

  13. Work-related road traffic injury: a multilevel systems protocol

    PubMed Central

    Newnam, Sharon; Sheppard, Dianne M; Griffin, Mark A; McClure, Roderick J; Heller, Gillian; Sim, Malcolm R; Stevenson, Mark R

    2014-01-01

    Background Although road traffic injury is reported as the leading cause of work-related death in Australia, it is not clear, due to limitations in previous methods used, just how large a burden it is. Many organisations are unaware of the extent of work-related road traffic injury and, importantly, what can be done to reduce the burden. The proposed research will (i) estimate the prevalence of work-related road traffic injury and (ii) identify the organisational determinants associated with work-related road traffic injury. Methods and design The current study is designed to enumerate the problem and identify the individual driver-level, the supervisor-level and organisational-level factors associated with work-related road traffic injury. The multilevel systems protocol will involve a series of cross-sectional surveys administered to drivers of fleet vehicles (n=1200), supervisors of the drivers (n=1200) and senior managers (n=300) within the same organisation. Discussion The novel use of the multilevel systems protocol is critical to be able to accurately assess the specific determinants of driving safety within each context of an organisation. Results The results are expected to highlight that reducing injury in the workplace requires more than just individual compliance with safety procedures. It will also establish, for the first time, an occupational translation taskforce to ensure that the research findings are adopted into work-place practice and thereby directly contribute to reductions in work-related road traffic injury. PMID:24478230

  14. Multilevel Intervention Research: Lessons Learned and Pathways Forward

    PubMed Central

    Taplin, Stephen H.; Foster, Mary K.; Fagan, Pebbles; Kaluzny, Arnold D.

    2012-01-01

    This summary reflects on this monograph regarding multilevel intervention (MLI) research to 1) assess its added value; 2) discuss what has been learned to date about its challenges in cancer care delivery; and 3) identify specific ways to improve its scientific soundness, feasibility, policy relevance, and research agenda. The 12 submitted chapters, and discussion of them at the March 2011 multilevel meeting, were reviewed and discussed among the authors to elicit key findings and results addressing the questions raised at the outset of this effort. MLI research is underrepresented as an explicit focus in the cancer literature but may improve implementation of studies of cancer care delivery if they assess contextual, organizational, and environmental factors important to understanding behavioral and/or system-level interventions. The field lacks a single unifying theory, although several psychological or biological theories are useful, and an ecological model helps conceptualize and communicate interventions. MLI research designs are often complex, involving nonlinear and nonhierarchical relationships that may not be optimally studied in randomized designs. Simulation modeling and pilot studies may be necessary to evaluate MLI interventions. Measurement and evaluation of team and organizational interventions are especially needed in cancer care, as are attention to the context of health-care reform, eHealth technology, and genomics-based medicine. Future progress in MLI research requires greater attention to developing and supporting relevant metrics of level effects and interactions and evaluating MLI interventions. MLI research holds an unrealized promise for understanding how to improve cancer care delivery. PMID:22623606

  15. The application of multilevel modelling to dental caries data.

    PubMed

    Burnside, G; Pine, C M; Williamson, P R

    2007-09-30

    Clinical studies of dental caries experience generate multiple outcome data for each participant, with information collected for each individual tooth surface. This paper investigates multilevel modelling as a method of analysis for dental caries data, allowing for full use of the data collected at surface level. Data from a clinical trial of a caries preventive agent in adolescents are modelled. The effect of tooth position within the mouth on the development of dental caries is investigated, with the results showing the importance of differentiating between the upper and lower arches, when modelling the probabilities of caries developing on teeth. Calculation of the intracluster correlation using the threshold model is suggested for use in multilevel logistic regression modelling of caries data. This model, which assumes that a dichotomous outcome is based on an underlying continuous variable with a threshold point where the outcome changes from zero to one, is identified to be appropriate for the analysis of caries which is a continuous process, but is only identified as present in a clinical trial when it has reached a certain level of severity. PMID:17340596

  16. Multilevel intervention research: lessons learned and pathways forward.

    PubMed

    Clauser, Steven B; Taplin, Stephen H; Foster, Mary K; Fagan, Pebbles; Kaluzny, Arnold D

    2012-05-01

    This summary reflects on this monograph regarding multilevel intervention (MLI) research to 1) assess its added value; 2) discuss what has been learned to date about its challenges in cancer care delivery; and 3) identify specific ways to improve its scientific soundness, feasibility, policy relevance, and research agenda. The 12 submitted chapters, and discussion of them at the March 2011 multilevel meeting, were reviewed and discussed among the authors to elicit key findings and results addressing the questions raised at the outset of this effort. MLI research is underrepresented as an explicit focus in the cancer literature but may improve implementation of studies of cancer care delivery if they assess contextual, organizational, and environmental factors important to understanding behavioral and/or system-level interventions. The field lacks a single unifying theory, although several psychological or biological theories are useful, and an ecological model helps conceptualize and communicate interventions. MLI research designs are often complex, involving nonlinear and nonhierarchical relationships that may not be optimally studied in randomized designs. Simulation modeling and pilot studies may be necessary to evaluate MLI interventions. Measurement and evaluation of team and organizational interventions are especially needed in cancer care, as are attention to the context of health-care reform, eHealth technology, and genomics-based medicine. Future progress in MLI research requires greater attention to developing and supporting relevant metrics of level effects and interactions and evaluating MLI interventions. MLI research holds an unrealized promise for understanding how to improve cancer care delivery. PMID:22623606

  17. Treatment of multilevel degenerative disc disease with intradiscal electrothermal therapy.

    PubMed

    Malik, K

    2007-04-01

    Intradiscal electrothermal therapy is a frequently performed procedure for the pain of internal disc disruption. It is typically performed on one to two discs; the discal treatment is followed by a long period of rest and rehabilitation. In patients with multilevel disc disease, intradiscal electrothermal therapy is either not contemplated or only one to two discs are treated at a time. This approach therefore either denies these patients the potential benefits of intradiscal electrothermal therapy or significantly prolongs the period of pain and disability. A 25-year-old female patient presented with internal disc disruption at four lumbar disc levels, diagnosed by provocative discography and post discography CT scan. All these discs were treated simultaneously by intradiscal electrothermal therapy. The patient tolerated the procedure well and responded favourably with significant and prolonged decrease in her symptoms. She reported sustained reduction in her pain and showed no clinical evidence of early neurological or infectious complications during 18 months of follow-up. This report indicates that intradiscal electrothermal therapy can be performed at multiple levels at a single sitting, compared to intradiscal electrothermal therapy performed at one to two discs at a time, this approach may obviate the need for surgery and may reduce the duration of pain and disability incurred. However, the influence of multilevel intradiscal electrothermal therapy on long-term complications or outcome is not known. PMID:17444324

  18. On decoding of multi-level MPSK modulation codes

    NASA Technical Reports Server (NTRS)

    Lin, Shu; Gupta, Alok Kumar

    1990-01-01

    The decoding problem of multi-level block modulation codes is investigated. The hardware design of soft-decision Viterbi decoder for some short length 8-PSK block modulation codes is presented. An effective way to reduce the hardware complexity of the decoder by reducing the branch metric and path metric, using a non-uniform floating-point to integer mapping scheme, is proposed and discussed. The simulation results of the design are presented. The multi-stage decoding (MSD) of multi-level modulation codes is also investigated. The cases of soft-decision and hard-decision MSD are considered and their performance are evaluated for several codes of different lengths and different minimum squared Euclidean distances. It is shown that the soft-decision MSD reduces the decoding complexity drastically and it is suboptimum. The hard-decision MSD further simplifies the decoding while still maintaining a reasonable coding gain over the uncoded system, if the component codes are chosen properly. Finally, some basic 3-level 8-PSK modulation codes using BCH codes as component codes are constructed and their coding gains are found for hard decision multistage decoding.

  19. Fabrication of multilevel silicon diffractive lenses for terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Walsby, Edward D.; Cheung, R.; Blaikie, Richard J.; Cumming, David R. S.

    1999-08-01

    Multilevel diffractive lenses give much higher efficiencies than simple binary structures by introducing a blaze. We have developed a novel micro-machining process that allows complex multi-level optics to be fabricated in silicon for use at terahertz frequencies. In this paper we demonstrate the fabrication of a four level (quaternary) lens designed for use at 1 THz. The process required two highly anisotropic dry etch stages that both used a SF6/O2 plasma at 173 K. The etch produced smooth etch surfaces with a vertical etch rate of 1 micrometers /min. The lithography for the first etch stage used a conventional positive photoresist process followed by NiCr deposition and lift-off to form an etch mask. For the second etch step the substrate was planarized and over-coated using SU-8, which was also used as a negative resist. The planarized specimen was then exposed to produce the etch mask for the next phase level etch of the lens. The process yielded a silicon:SU-8 etch selectivity of 4:1 which was more than adequate. Between the two etches a total etch depth of 115 micrometers was obtained, with steps at 38 and 77 micrometers and a minimum feature of 84 micrometers . It is anticipated that the process can be extended to give more phase levels with greater optical efficiency.

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

    SciTech Connect

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

    2010-11-01

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

  1. Multi-level approach for parametric roll analysis

    NASA Astrophysics Data System (ADS)

    Kim, Taeyoung; Kim, Yonghwan

    2011-03-01

    The present study considers multi-level approach for the analysis of parametric roll phenomena. Three kinds of computation method, GM variation, impulse response function (IRF), and Rankine panel method, are applied for the multi-level approach. IRF and Rankine panel method are based on the weakly nonlinear formulation which includes nonlinear Froude- Krylov and restoring forces. In the computation result of parametric roll occurrence test in regular waves, IRF and Rankine panel method show similar tendency. Although the GM variation approach predicts the occurrence of parametric roll at twice roll natural frequency, its frequency criteria shows a little difference. Nonlinear roll motion in bichromatic wave is also considered in this study. To prove the unstable roll motion in bichromatic waves, theoretical and numerical approaches are applied. The occurrence of parametric roll is theoretically examined by introducing the quasi-periodic Mathieu equation. Instability criteria are well predicted from stability analysis in theoretical approach. From the Fourier analysis, it has been verified that difference-frequency effects create the unstable roll motion. The occurrence of unstable roll motion in bichromatic wave is also observed in the experiment.

  2. Plutonium immobilization -- Can loading

    SciTech Connect

    Kriikku, E.

    2000-02-17

    The Savannah River Site (SRS) will immobilize excess plutonium in the proposed Plutonium Immobilization Project (PIP). The PIP adds the excess plutonium to ceramic pucks, loads the pucks into cans, and places the cans into DWPF canisters. This paper discusses the PIP process steps, the can loading conceptual design, can loading equipment design, and can loading work completed.

  3. Single Versus Multilevel Fusion, For Single Level Degenerative Spondylolisthesis And Multilevel Lumbar Stenosis. Four-Year Results of the Spine Patient Outcomes Research Trial

    PubMed Central

    Smorgick, Yossi; Park, Daniel K.; Baker, Kevin C; Lurie, Jon D.; Tosteson, Tor D.; Zhao, Wenyan; Herkowitz, Harry; Fischgrund, Jeffrey S; Weinstein, James N.

    2013-01-01

    Study design A subanalysis study. Objective To compare surgical outcomes and complications of multi level decompression and single level fusion to multi level decompression and multi level fusion for patients with multilevel lumbar stenosis and single level degenerative spondylolisthesis. Summary of Background Data In patients with degenerative spondylolisthesis who are treated surgically, decompression and fusion provides a better clinical outcome than decompression alone. Surgical treatment for multilevel lumbar stenosis and degenerative spondylolisthesis typically includes decompression and fusion of the spondylolisthesis segment and decompression with or without fusion for the other stenotic segments. To date, no study has compared the results of these two surgical options for single level degenerative spondylolisthesis with multilevel stenosis. Methods The results from a multicenter randomized and observational study, the Spine Patient Outcomes Research Trial (SPORT) comparing multilevel decompression and single level fusion and multi level decompression and multi level fusion for spinal stenosis with spondylolisthesis, were analyzed. The primary outcomes measures were the Bodily Pain and Physical Function scales of the Medical Outcomes Study 36-item Short-Form General Health Survey (SF-36) and the modified Oswestry Disability Index at 1,2, 3 and 4 years postoperatively. Secondary analysis consisted of stenosis bothersomeness index, low back pain bothersomeness, leg pain, patient satisfaction, and self-rated progress. Results Overall 207 patients were enrolled to the study, 130 had multlilevel decompression with one level fusion and 77 patients had multi level decompression and multi-level fusion. For all primary and secondary outcome measures, there were no statistically significant differences in surgical outcomes between the two surgical techniques. However, operative time and intraoperative blood loss were significantly higher in the multilevel fusion

  4. Introduction: Understanding and Influencing Multilevel Factors Across the Cancer Care Continuum

    PubMed Central

    Anhang Price, Rebecca; Edwards, Heather M.; Foster, Mary K.; Breslau, Erica S.; Chollette, Veronica; Prabhu Das, Irene; Clauser, Steven B.; Fennell, Mary L.; Zapka, Jane

    2012-01-01

    Health care in the United States is notoriously expensive while often failing to deliver the care recommended in published guidelines. There is, therefore, a need to consider our approach to health-care delivery. Cancer care is a good example for consideration because it spans the continuum of health-care issues from primary prevention through long-term survival and end-of-life care. In this monograph, we emphasize that health-care delivery occurs in a multilevel system that includes organizations, teams, and individuals. To achieve health-care delivery consistent with the Institute of Medicine's six quality aims (safety, effectiveness, timeliness, efficiency, patient-centeredness, and equity), we must influence multiple levels of that multilevel system. The notion that multiple levels of contextual influence affect behaviors through interdependent interactions is a well-established ecological view. This view has been used to analyze health-care delivery and health disparities. However, experience considering multilevel interventions in health care is much less robust. This monograph includes 13 chapters relevant to expanding the foundation of research for multilevel interventions in health-care delivery. Subjects include clinical cases of multilevel thinking in health-care delivery, the state of knowledge regarding multilevel interventions, study design and measurement considerations, methods for combining interventions, time as a consideration in the evaluation of effects, measurement of effects, simulations, application of multilevel thinking to health-care systems and disparities, and implementation of the Affordable Care Act of 2010. Our goal is to outline an agenda to proceed with multilevel intervention research, not because it guarantees improvement in our current approach to health care, but because ignoring the complexity of the multilevel environment in which care occurs has not achieved the desired improvements in care quality outlined by the Institute

  5. Building of multilevel stakeholder consensus in radioactive waste repository siting

    SciTech Connect

    Dreimanis, A.

    2007-07-01

    This report considers the problem of multilevel consensus building for siting and construction of shared multinational/regional repositories for radioactive waste (RW) deep disposal. In the siting of a multinational repository there appears an essential innovative component of stakeholder consensus building, namely: to reach consent - political, social, economic, ecological - among international partners, in addition to solving the whole set of intra-national consensus building items. An entire partnering country is considered as a higher-level stakeholder - the national stakeholder, represented by the national government, being faced to simultaneous seeking an upward (international) and a downward (intra-national) consensus in a psychologically stressed environment, possibly being characterized by diverse political, economic and social interests. The following theses as a possible interdisciplinary approach towards building of shared understanding and stakeholder consensus on the international scale of RW disposal are forwarded and developed: a) building of international stakeholder consensus would be promoted by activating and diversifying on the international scale multilateral interactions between intra- and international stakeholders, including web-based networks of the RW disposal site investigations and decision-making, as well as networks for international cooperation among government authorities in nuclear safety, b) gradual progress in intergovernmental consensus and reaching multilateral agreements on shared deep repositories will be the result of democratic dialogue, via observing the whole set of various interests and common resolving of emerged controversies by using advanced synergetic approaches of conflict resolution, c) cross-cultural thinking and world perception, mental flexibility, creativity and knowledge are considered as basic prerogatives for gaining a higher level of mutual understanding and consensus for seeking further consensus, for

  6. Multi-level trellis coded modulation and multi-stage decoding

    NASA Technical Reports Server (NTRS)

    Costello, Daniel J., Jr.; Wu, Jiantian; Lin, Shu

    1990-01-01

    Several constructions for multi-level trellis codes are presented and many codes with better performance than previously known codes are found. These codes provide a flexible trade-off between coding gain, decoding complexity, and decoding delay. New multi-level trellis coded modulation schemes using generalized set partitioning methods are developed for Quadrature Amplitude Modulation (QAM) and Phase Shift Keying (PSK) signal sets. New rotationally invariant multi-level trellis codes which can be combined with differential encoding to resolve phase ambiguity are presented.

  7. A Simple 2/3 Modulation Code for Multi-Level Holographic Data Storage

    NASA Astrophysics Data System (ADS)

    Kim, Soo Youn; Lee, Jaejin

    2013-09-01

    We propose a simple 2/3 modulation code for multi-level holographic data storage (HDS). HDS is a promising method for the optical data storage system. However, two-dimensional (2D) inter-symbol interference (ISI) and inter-page interference (IPI) are weaknesses of HDS systems. Moreover, if multi-level symbols are stored, such systems are more vulnerable to errors. A modulation code can be used to alleviate these problems. Therefore, we introduce a simple 2/3 modulation code for multi-level HDS systems, which is simple and mitigates 2D ISI patterns.

  8. Planarization of metal films for multilevel interconnects by pulsed laser heating

    DOEpatents

    Tuckerman, David B.

    1987-01-01

    In the fabrication of multilevel integrated circuits, each metal layer is planarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

  9. A multilevel perspective on faultlines: Differentiating the effects between group- and organizational-level faultlines.

    PubMed

    Bezrukova, Katerina; Spell, Chester S; Caldwell, David; Burger, Jerry M

    2016-01-01

    Integrating the literature on faultlines, conflict, and pay, we drew on the basic principles of multilevel theory and differentiated between group- and organizational-level faultlines to introduce a novel multilevel perspective on faultlines. Using multisource, multilevel data on 30 Major League Baseball (MLB) teams, we found that group-level faultlines were negatively associated with group performance, and that internally focused conflict exacerbated but externally focused conflict mitigated this effect. Organizational-level faultlines were negatively related to organizational performance, and were most harmful in organizations with high levels of compensation. Implications for groups and teams in the sports/entertainment and other industries are discussed. PMID:26167645

  10. High Power Disk Loaded Guide Load

    SciTech Connect

    Farkas, Z.D.; /SLAC

    2006-02-22

    A method to design a matching section from a smooth guide to a disk-loaded guide, using a variation of broadband matching, [1, 2] is described. Using this method, we show how to design high power loads. The load consists of a disk-loaded coaxial guide operating in the TE{sub 01}-mode. We use this mode because it has no electric field terminating on a conductor, has no axial currents, and has no current at the cylinder-disk interface. A high power load design that has -35 dB reflection and a 200 MHz, -20 dB bandwidth, is presented. It is expected that it will carry the 600 MW output peak power of the pulse compression network. We use coaxial geometry and stainless steel material to increase the attenuation per cell.

  11. Efficient multilevel brain tumor segmentation with integrated bayesian model classification.

    PubMed

    Corso, J J; Sharon, E; Dube, S; El-Saden, S; Sinha, U; Yuille, A

    2008-05-01

    We present a new method for automatic segmentation of heterogeneous image data that takes a step toward bridging the gap between bottom-up affinity-based segmentation methods and top-down generative model based approaches. The main contribution of the paper is a Bayesian formulation for incorporating soft model assignments into the calculation of affinities, which are conventionally model free. We integrate the resulting model-aware affinities into the multilevel segmentation by weighted aggregation algorithm, and apply the technique to the task of detecting and segmenting brain tumor and edema in multichannel magnetic resonance (MR) volumes. The computationally efficient method runs orders of magnitude faster than current state-of-the-art techniques giving comparable or improved results. Our quantitative results indicate the benefit of incorporating model-aware affinities into the segmentation process for the difficult case of glioblastoma multiforme brain tumor. PMID:18450536

  12. Drilling and completion specifications for CA series multilevel piezometers

    SciTech Connect

    Clawson, T.S.

    1986-08-01

    CX Series multilevel piezometer boreholes will provide information on hydraulic heads in the Rosalia, Sentinel Gap, Ginkgo, Rocky Coulee, Cohassett, Birkett, and Umtanum flow tops. The borehole sites will be located adjacent to the reference repository location. In addition, information from the boreholes will provide input data used to determine horizontal and vertical flow rates, and identify possible geologic structures. This specification includes details for drilling, piezometer design, hydrologic testing, and hydrochemical sampling of the boreholes. It includes drilling requirements, design, and installation procedures for the series piezometer nests, intervals selected for head monitoring and schedules for drilling and piezometer installation. Specific drilling and piezometer installation specifications for boreholes DC-24CX and DC-25CX are also included. 27 refs., 5 figs., 3 tabs.

  13. Optical image encryption using multilevel Arnold transform and noninterferometric imaging

    NASA Astrophysics Data System (ADS)

    Chen, Wen; Chen, Xudong

    2011-11-01

    Information security has attracted much current attention due to the rapid development of modern technologies, such as computer and internet. We propose a novel method for optical image encryption using multilevel Arnold transform and rotatable-phase-mask noninterferometric imaging. An optical image encryption scheme is developed in the gyrator transform domain, and one phase-only mask (i.e., phase grating) is rotated and updated during image encryption. For the decryption, an iterative retrieval algorithm is proposed to extract high-quality plaintexts. Conventional encoding methods (such as digital holography) have been proven vulnerably to the attacks, and the proposed optical encoding scheme can effectively eliminate security deficiency and significantly enhance cryptosystem security. The proposed strategy based on the rotatable phase-only mask can provide a new alternative for data/image encryption in the noninterferometric imaging.

  14. A multilevel multiscale mimetic method for an anisotropic infiltration problem

    SciTech Connect

    Lipnikov, Konstantin; Moulton, David; Svyatskiy, Daniil

    2009-01-01

    Modeling of multiphase flow and transport in highly heterogeneous porous media must capture a broad range of coupled spatial and temporal scales. Recently, a hierarchical approach dubbed the Multilevel Multiscale Mimetic (M3) method, was developed to simulate two-phase flow in porous media. The M{sup 3} method is locally mass conserving at all levels in its hierarchy, it supports unstructured polygonal grids and full tensor permeabilities, and it can achieve large coarsening factors. In this work we consider infiltration of water into a two-dimensional layered medium. The grid is aligned with the layers but not the coordinate axes. We demonstrate that with an efficient temporal updating strategy for the coarsening parameters, fine-scale accuracy of prominent features in the flow is maintained by the M{sup 3} method.

  15. A dynamic multilevel model of demographic diversity and misfit effects.

    PubMed

    Sacco, Joshua M; Schmitt, Neal

    2005-03-01

    In this study, the authors proposed and evaluated the linkages of a dynamic multilevel model of demographic diversity and misfit effects in a large sample of quick-service restaurants. Using a cross-level approach, the authors studied an employee's demographic misfit in relation to coworkers' demographics as a predictor of turnover risk over time. At the business-unit level, they studied changes in restaurant demographic diversity in relation to changes in profitability over time and unit turnover rates in relation to profitability. The authors also studied the impact of the match between the racial compositions of the restaurants and their communities on profitability. The results supported linkages between demographic misfit and turnover and partially supported a negative association between racial diversity and changes in profitability. PMID:15769233

  16. Multilevel cascade voltage source inverter with seperate DC sources

    DOEpatents

    Peng, Fang Zheng; Lai, Jih-Sheng

    2002-01-01

    A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

  17. Multilevel cascade voltage source inverter with seperate DC sources

    DOEpatents

    Peng, Fang Zheng; Lai, Jih-Sheng

    1997-01-01

    A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

  18. Ecology and multilevel selection explain aggression in spider colonies.

    PubMed

    Biernaskie, Jay M; Foster, Kevin R

    2016-08-01

    Progress in sociobiology continues to be hindered by abstract debates over methodology and the relative importance of within-group vs. between-group selection. We need concrete biological examples to ground discussions in empirical data. Recent work argued that the levels of aggression in social spider colonies are explained by group-level adaptation. Here, we examine this conclusion using models that incorporate ecological detail while remaining consistent with kin- and multilevel selection frameworks. We show that although levels of aggression are driven, in part, by between-group selection, incorporating universal within-group competition provides a striking fit to the data that is inconsistent with pure group-level adaptation. Instead, our analyses suggest that aggression is favoured primarily as a selfish strategy to compete for resources, despite causing lower group foraging efficiency or higher risk of group extinction. We argue that sociobiology will benefit from a pluralistic approach and stronger links between ecologically informed models and data. PMID:27264438

  19. Development of the Multi-Level Seismic Receiver (MLSR)

    SciTech Connect

    Sleefe, G.E.; Engler, B.P.; Drozda, P.M.; Franco, R.J.; Morgan, J.

    1995-02-01

    The Advanced Geophysical Technology Department (6114) and the Telemetry Technology Development Department (2664) have, in conjunction with the Oil Recovery Technology Partnership, developed a Multi-Level Seismic Receiver (MLSR) for use in crosswell seismic surveys. The MLSR was designed and evaluated with the significant support of many industry partners in the oil exploration industry. The unit was designed to record and process superior quality seismic data operating in severe borehole environments, including high temperature (up to 200{degrees}C) and static pressure (10,000 psi). This development has utilized state-of-the-art technology in transducers, data acquisition, and real-time data communication and data processing. The mechanical design of the receiver has been carefully modeled and evaluated to insure excellent signal coupling into the receiver.

  20. Multilevel models for survival analysis with random effects.

    PubMed

    Yau, K K

    2001-03-01

    A method for modeling survival data with multilevel clustering is described. The Cox partial likelihood is incorporated into the generalized linear mixed model (GLMM) methodology. Parameter estimation is achieved by maximizing a log likelihood analogous to the likelihood associated with the best linear unbiased prediction (BLUP) at the initial step of estimation and is extended to obtain residual maximum likelihood (REML) estimators of the variance component. Estimating equations for a three-level hierarchical survival model are developed in detail, and such a model is applied to analyze a set of chronic granulomatous disease (CGD) data on recurrent infections as an illustration with both hospital and patient effects being considered as random. Only the latter gives a significant contribution. A simulation study is carried out to evaluate the performance of the REML estimators. Further extension of the estimation procedure to models with an arbitrary number of levels is also discussed. PMID:11252624

  1. Multilevel interference resonances in strongly driven three-level systems.

    PubMed

    Danon, Jeroen; Rudner, Mark S

    2014-12-12

    We study multiphoton resonances in a strongly driven three-level quantum system, where one level is periodically swept through a pair of levels with constant energy separation E. Near the multiphoton resonance condition nℏω=E, where n is an integer, we find qualitatively different behavior for n even or odd. We explain this phenomenon in terms of families of interfering trajectories of the multilevel system. Remarkably, the behavior is insensitive to fluctuations of the energy of the driven level, and survives deep into the strong dephasing regime. The setup can be relevant for a variety of solid state and atomic or molecular systems. In particular, it provides a clear mechanism to explain recent puzzling experimental observations in strongly driven double quantum dots. PMID:25541796

  2. Stabilized multilevel Monte Carlo method for stiff stochastic differential equations

    NASA Astrophysics Data System (ADS)

    Abdulle, Assyr; Blumenthal, Adrian

    2013-10-01

    A multilevel Monte Carlo (MLMC) method for mean square stable stochastic differential equations with multiple scales is proposed. For such problems, that we call stiff, the performance of MLMC methods based on classical explicit methods deteriorates because of the time step restriction to resolve the fastest scales that prevents to exploit all the levels of the MLMC approach. We show that by switching to explicit stabilized stochastic methods and balancing the stabilization procedure simultaneously with the hierarchical sampling strategy of MLMC methods, the computational cost for stiff systems is significantly reduced, while keeping the computational algorithm fully explicit and easy to implement. Numerical experiments on linear and nonlinear stochastic differential equations and on a stochastic partial differential equation illustrate the performance of the stabilized MLMC method and corroborate our theoretical findings.

  3. Multi-level adaptive finite element methods. 1: Variation problems

    NASA Technical Reports Server (NTRS)

    Brandt, A.

    1979-01-01

    A general numerical strategy for solving partial differential equations and other functional problems by cycling between coarser and finer levels of discretization is described. Optimal discretization schemes are provided together with very fast general solvers. It is described in terms of finite element discretizations of general nonlinear minimization problems. The basic processes (relaxation sweeps, fine-grid-to-coarse-grid transfers of residuals, coarse-to-fine interpolations of corrections) are directly and naturally determined by the objective functional and the sequence of approximation spaces. The natural processes, however, are not always optimal. Concrete examples are given and some new techniques are reviewed. Including the local truncation extrapolation and a multilevel procedure for inexpensively solving chains of many boundary value problems, such as those arising in the solution of time-dependent problems.

  4. Finding Chemical Reaction Paths with a Multilevel Preconditioning Protocol

    PubMed Central

    2015-01-01

    Finding transition paths for chemical reactions can be computationally costly owing to the level of quantum-chemical theory needed for accuracy. Here, we show that a multilevel preconditioning scheme that was recently introduced (Tempkin et al. J. Chem. Phys.2014, 140, 184114) can be used to accelerate quantum-chemical string calculations. We demonstrate the method by finding minimum-energy paths for two well-characterized reactions: tautomerization of malonaldehyde and Claissen rearrangement of chorismate to prephanate. For these reactions, we show that preconditioning density functional theory (DFT) with a semiempirical method reduces the computational cost for reaching a converged path that is an optimum under DFT by several fold. The approach also shows promise for free energy calculations when thermal noise can be controlled. PMID:25516726

  5. Multilevel Nonvolatile Memristive and Memcapacitive Switching in Stacked Graphene Sheets.

    PubMed

    Park, Minji; Park, Sungjin; Yoo, Kyung-Hwa

    2016-06-01

    We fabricated devices consisting of single and double graphene sheets embedded in organic polymer layers. These devices had binary and ternary nonvolatile resistive switching behaviors, respectively. Capacitance-voltage (C-V) curves and scanning capacitance microscopy (SCM) images were obtained to investigate the switching mechanism. The C-V curves exhibited a large hysteresis, implying that the graphene sheets acted as charging and discharging layers and that resistive switching was caused by charges trapped in the graphene layers. In addition, binary capacitive switching behaviors were observed for the device with a single graphene sheet, and ternary capacitive switching behaviors were observed for the device with the double graphene sheets. These results demonstrated that devices consisting of graphene sheets embedded in the polymer layers can be applied to multilevel nonvolatile memcapacitive devices as well as memristive devices. PMID:27203557

  6. Finding Chemical Reaction Paths with a Multilevel Preconditioning Protocol

    DOE PAGESBeta

    Kale, Seyit; Sode, Olaseni; Weare, Jonathan; Dinner, Aaron R.

    2014-11-07

    Finding transition paths for chemical reactions can be computationally costly owing to the level of quantum-chemical theory needed for accuracy. Here, we show that a multilevel preconditioning scheme that was recently introduced (Tempkin et al. J. Chem. Phys. 2014, 140, 184114) can be used to accelerate quantum-chemical string calculations. We demonstrate the method by finding minimum-energy paths for two well-characterized reactions: tautomerization of malonaldehyde and Claissen rearrangement of chorismate to prephanate. For these reactions, we show that preconditioning density functional theory (DFT) with a semiempirical method reduces the computational cost for reaching a converged path that is an optimum undermore » DFT by several fold. In conclusion, the approach also shows promise for free energy calculations when thermal noise can be controlled.« less

  7. Multigrid and multilevel domain decomposition for unstructured grids

    SciTech Connect

    Chan, T.; Smith, B.

    1994-12-31

    Multigrid has proven itself to be a very versatile method for the iterative solution of linear and nonlinear systems of equations arising from the discretization of PDES. In some applications, however, no natural multilevel structure of grids is available, and these must be generated as part of the solution procedure. In this presentation the authors will consider the problem of generating a multigrid algorithm when only a fine, unstructured grid is given. Their techniques generate a sequence of coarser grids by first forming an approximate maximal independent set of the vertices and then applying a Cavendish type algorithm to form the coarser triangulation. Numerical tests indicate that convergence using this approach can be as fast as standard multigrid on a structured mesh, at least in two dimensions.

  8. Schwarz and multilevel methods for quadratic spline collocation

    SciTech Connect

    Christara, C.C.; Smith, B.

    1994-12-31

    Smooth spline collocation methods offer an alternative to Galerkin finite element methods, as well as to Hermite spline collocation methods, for the solution of linear elliptic Partial Differential Equations (PDEs). Recently, optimal order of convergence spline collocation methods have been developed for certain degree splines. Convergence proofs for smooth spline collocation methods are generally more difficult than for Galerkin finite elements or Hermite spline collocation, and they require stronger assumptions and more restrictions. However, numerical tests indicate that spline collocation methods are applicable to a wider class of problems, than the analysis requires, and are very competitive to finite element methods, with respect to efficiency. The authors will discuss Schwarz and multilevel methods for the solution of elliptic PDEs using quadratic spline collocation, and compare these with domain decomposition methods using substructuring. Numerical tests on a variety of parallel machines will also be presented. In addition, preliminary convergence analysis using Schwarz and/or maximum principle techniques will be presented.

  9. Collaborating for impact: a multilevel early childhood obesity prevention initiative.

    PubMed

    Agrawal, Tara; Hoffman, Jessica A; Ahl, Marilyn; Bhaumik, Urmi; Healey, Christine; Carter, Sonia; Dickerson, Deborah; Nethersole, Shari; Griffin, Daphne; Castaneda-Sceppa, Carmen

    2012-01-01

    This article presents Healthy Kids, Healthy Futures, a multilevel initiative in Boston, Massachusetts, which brings major institutions' missions and resources together to address early childhood obesity prevention. Programming is designed to facilitate healthy eating and physical activity in preschool children's home, school, and community environments by engaging parents and early childhood educators in the places where they live, learn, and play. This article describes how established interventions were implemented in a novel setting to engage the parents of children attending Head Start and staff, and presents pilot data from the first 2 years of the initiative. Healthy Kids, Healthy Futures is a feasible initiative, which has shown concrete, positive results that can be replicated. PMID:22617410

  10. Multi-Level iterative methods in computational plasma physics

    SciTech Connect

    Knoll, D.A.; Barnes, D.C.; Brackbill, J.U.; Chacon, L.; Lapenta, G.

    1999-03-01

    Plasma physics phenomena occur on a wide range of spatial scales and on a wide range of time scales. When attempting to model plasma physics problems numerically the authors are inevitably faced with the need for both fine spatial resolution (fine grids) and implicit time integration methods. Fine grids can tax the efficiency of iterative methods and large time steps can challenge the robustness of iterative methods. To meet these challenges they are developing a hybrid approach where multigrid methods are used as preconditioners to Krylov subspace based iterative methods such as conjugate gradients or GMRES. For nonlinear problems they apply multigrid preconditioning to a matrix-few Newton-GMRES method. Results are presented for application of these multilevel iterative methods to the field solves in implicit moment method PIC, multidimensional nonlinear Fokker-Planck problems, and their initial efforts in particle MHD.

  11. Accelerating particle-in-cell simulations using multilevel Monte Carlo

    NASA Astrophysics Data System (ADS)

    Ricketson, Lee

    2015-11-01

    Particle-in-cell (PIC) simulations have been an important tool in understanding plasmas since the dawn of the digital computer. Much more recently, the multilevel Monte Carlo (MLMC) method has accelerated particle-based simulations of a variety of systems described by stochastic differential equations (SDEs), from financial portfolios to porous media flow. The fundamental idea of MLMC is to perform correlated particle simulations using a hierarchy of different time steps, and to use these correlations for variance reduction on the fine-step result. This framework is directly applicable to the Langevin formulation of Coulomb collisions, as demonstrated in previous work, but in order to apply to PIC simulations of realistic scenarios, MLMC must be generalized to incorporate self-consistent evolution of the electromagnetic fields. We present such a generalization, with rigorous results concerning its accuracy and efficiency. We present examples of the method in the collisionless, electrostatic context, and discuss applications and extensions for the future.

  12. Finding Chemical Reaction Paths with a Multilevel Preconditioning Protocol

    SciTech Connect

    Kale, Seyit; Sode, Olaseni; Weare, Jonathan; Dinner, Aaron R.

    2014-11-07

    Finding transition paths for chemical reactions can be computationally costly owing to the level of quantum-chemical theory needed for accuracy. Here, we show that a multilevel preconditioning scheme that was recently introduced (Tempkin et al. J. Chem. Phys. 2014, 140, 184114) can be used to accelerate quantum-chemical string calculations. We demonstrate the method by finding minimum-energy paths for two well-characterized reactions: tautomerization of malonaldehyde and Claissen rearrangement of chorismate to prephanate. For these reactions, we show that preconditioning density functional theory (DFT) with a semiempirical method reduces the computational cost for reaching a converged path that is an optimum under DFT by several fold. In conclusion, the approach also shows promise for free energy calculations when thermal noise can be controlled.

  13. Multilevel polarization shift keying: Optimum receiver structure and performance evaluation

    SciTech Connect

    Benedetto, S.; Poggiolini, P.T.

    1994-02-01

    Multilevel digital coherent optical modulation schemes based on the state of polarization of a fully polarized lightwave are proposed and analyzed. Based on the complete statistical characterization of the Stokes parameters, extracted though appropriate signal processing in the presence of shot and additive gaussian noise, the optimum maximum likelihood receiver operating symbol by symbol is derived. The exact performance in terms of the average symbol error probability is found. Optimum constellations for the case of equipower 4, 8, 16 and 32 signals are found on the basis of the minimization of the error probability for a given average power. Their performance turns out to be promising as compared to other standard modulation techniques. The spectral analysis of polarization modulated signals is presented. A new receiver structure, which solves the problem of the excess penalties incurred in the presence of channel dichroism, is proposed and analyzed. 22 refs.

  14. Multilevel cascade voltage source inverter with separate DC sources

    DOEpatents

    Peng, F.Z.; Lai, J.S.

    1997-06-24

    A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations. 15 figs.

  15. Multilevel cascade voltage source inverter with seperate DC sources

    DOEpatents

    Peng, Fang Zheng; Lai, Jih-Sheng

    2001-04-03

    A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

  16. Comparison of Estimation Procedures for Multilevel AR(1) Models.

    PubMed

    Krone, Tanja; Albers, Casper J; Timmerman, Marieke E

    2016-01-01

    To estimate a time series model for multiple individuals, a multilevel model may be used. In this paper we compare two estimation methods for the autocorrelation in Multilevel AR(1) models, namely Maximum Likelihood Estimation (MLE) and Bayesian Markov Chain Monte Carlo. Furthermore, we examine the difference between modeling fixed and random individual parameters. To this end, we perform a simulation study with a fully crossed design, in which we vary the length of the time series (10 or 25), the number of individuals per sample (10 or 25), the mean of the autocorrelation (-0.6 to 0.6 inclusive, in steps of 0.3) and the standard deviation of the autocorrelation (0.25 or 0.40). We found that the random estimators of the population autocorrelation show less bias and higher power, compared to the fixed estimators. As expected, the random estimators profit strongly from a higher number of individuals, while this effect is small for the fixed estimators. The fixed estimators profit slightly more from a higher number of time points than the random estimators. When possible, random estimation is preferred to fixed estimation. The difference between MLE and Bayesian estimation is nearly negligible. The Bayesian estimation shows a smaller bias, but MLE shows a smaller variability (i.e., standard deviation of the parameter estimates). Finally, better results are found for a higher number of individuals and time points, and for a lower individual variability of the autocorrelation. The effect of the size of the autocorrelation differs between outcome measures. PMID:27242559

  17. Multilevel Ge-Se Film Based Resist Systems

    NASA Astrophysics Data System (ADS)

    Tai, K. L.; Vadimsky, R. G.; Ong, E.

    1982-06-01

    Multilevel resist systems based on Ge-Se films make possible the use of optical projection printers for printing 0.5-1.0μm features. The four multilevel resist systems considered employ either a photosensitive or a photopassive polymer layer for planarization. In bilevel schemes the surface of the Ge-Se film is reacted in a Ag(CN)i- containing solution to form a Ag2Se imaging layer. No reacted Ge-Se is used as a sacrificial layer in trilevel schemes. Ge-Se films are resistant to attack by oxygen plasma and therefore make good masks for pattern transfer by dry (reactive ion) etching, to a thick underlying photopassive polymer layer. Because of their high absorbance (a 105cm-1) in the ultraviolet and violet, Ge-Se patterns can also be used as exposure masks for transferring images to a thick underlying photosensitive polymer layer. The latter is "flood" exposed through the Ge-Se mask and wet developed. Both dry and wet processes provide steep wall-profile patterns in the polymer layer. The dry process provides superior feature size control while the wet process offers reduced processing cost. The exceptional lithographic performance exhibited by Ge-Se resist systems is attributed to a unique edge-sharpening effect; diffraction is compensated for by lateral silver diffusion in the Ag2Se layer. Patterns having 0.6μm lines and spaces are obtained over lcmXlcm fields with a defocus tolerance of 2.5μm using a standard Zeiss 10:1 reduction lens (N.A.=0.28, λ=436nm). Results indicate that optical lithography can practically print features in the size regime previously reserved for a-beam or x-ray based lithographic technologies.

  18. Multilevel and multi-user sustainability assessment of farming systems

    SciTech Connect

    Van Passel, Steven; Meul, Marijke

    2012-01-15

    Sustainability assessment is needed to build sustainable farming systems. A broad range of sustainability concepts, methodologies and applications already exists. They differ in level, focus, orientation, measurement, scale, presentation and intended end-users. In this paper we illustrate that a smart combination of existing methods with different levels of application can make sustainability assessment more profound, and that it can broaden the insights of different end-user groups. An overview of sustainability assessment tools on different levels and for different end-users shows the complementarities and the opportunities of using different methods. In a case-study, a combination of the sustainable value approach (SVA) and MOTIFS is used to perform a sustainability evaluation of farming systems in Flanders. SVA is used to evaluate sustainability at sector level, and is especially useful to support policy makers, while MOTIFS is used to support and guide farmers towards sustainability at farm level. The combined use of the two methods with complementary goals can widen the insights of both farmers and policy makers, without losing the particularities of the different approaches. To stimulate and support further research and applications, we propose guidelines for multilevel and multi-user sustainability assessments. - Highlights: Black-Right-Pointing-Pointer We give an overview of sustainability assessment tools for agricultural systems. Black-Right-Pointing-Pointer SVA and MOTIFS are used to evaluate the sustainability of dairy farming in Flanders. Black-Right-Pointing-Pointer Combination of methods with different levels broadens the insights of different end-user groups. Black-Right-Pointing-Pointer We propose guidelines for multilevel and multi-user sustainability assessments.

  19. A multilevel perspective to explain recycling behaviour in communities.

    PubMed

    Tabernero, Carmen; Hernández, Bernardo; Cuadrado, Esther; Luque, Bárbara; Pereira, Cícero R

    2015-08-15

    Previous research on the motivation for environmentally responsible behaviour has focused mainly on individual variables, rather than organizational or collective variables. Therefore, the results of those studies are hardly applicable to environmental management. This study considers individual, collective, and organizational variables together that contribute to the management of environmental waste. The main aim is to identify, through the development of a multilevel model, those predictive variables of recycling behaviour that help organizations to increase the recycling rates in their communities. Individual (age, gender, educational level, self-efficacy with respect to residential recycling, individual recycling behaviour), organizational (satisfaction with the quality of the service provided by a recycling company), and collective (community recycling rates, number of inhabitants, community efficacy beliefs) motivational factors relevant to recycling behaviour were analysed. A sample of 1501 residents from 55 localities was surveyed. The results of multilevel analyses indicated that there was significant variability within and between localities. Interactions between variables at the level of the individual (e.g. satisfaction with service quality) and variables at the level of the collective (e.g. community efficacy) predicted recycling behaviour in localities with low and high community recycling rates and large and small populations. The interactions showed that the relationship between self-efficacy and recycling is stronger in localities with weak community efficacy beliefs than in communities with strong beliefs. The findings show that the relationship between satisfaction with service quality and recycling behaviour is stronger in localities with strong community efficacy beliefs than in communities with weaker beliefs and a smaller population. The results are discussed accordingly in relation to theory and possible contribution to waste management

  20. Efficient Multidisciplinary Analysis Procedure Using Multi-Level Parallelization Approach

    NASA Technical Reports Server (NTRS)

    Byun, Chansup; Hatay, Ferhat; Farhangnia, Mehrdad; Guruswamy, Guru; VanDalsem, William R. (Technical Monitor)

    1997-01-01

    Multidisciplinary applications are suitable for parallel computing environment by adopting the domain decomposition method. Immediately, a multidisciplinary application can be parallelized by solving each discipline separately. In order to perform coupled multidisciplinary analysis, coupling of each discipline can be accomplished by exchanging boundary data at the interfaces. This is regarded as discipline-level parallelization. Next level could be a "coarse-grain" parallelization of each discipline, which mainly depends on the physical geometry and nature of each discipline. For example, it is almost impossible for structured-grid based computational fluid dynamics codes to do flow analysis of an aircraft by using a single grid because of the complexity of its configuration. Thus, multi-block grid is commonly used to describe the details of complex geometry. Similarly, in structural analysis, the structure is frequently subdivided into substructures. Thus, the computation of each subdomain can be easily parallelized since each subdomain is solved separately independent of other domains. The parallelization is accomplished by solving each subdomain separately on a separate processor and exchanging the boundary conditions at domain interfaces periodically. However, the physical decomposition of the domain introduces explicit boundary conditions at the domain interfaces. This is not desirable for critical areas such as those containing shock waves or flow separations. Thus, a "fine-grain" parallelization is introduced to overcome this problem. The "fine-grain" parallelization is one that solves exactly the same system of equations of a subdomain by using more than one processors without introducing any explicit boundary conditions. An efficient multidisciplinary analysis procedure can be accomplished by successfully combining the above multi-level parallelism. A multidisciplinary analysis code, ENSAERO developed at NASA Ames Research Center is used in this study to

  1. Politics of innovation in multi-level water governance systems

    NASA Astrophysics Data System (ADS)

    Daniell, Katherine A.; Coombes, Peter J.; White, Ian

    2014-11-01

    Innovations are being proposed in many countries in order to support change towards more sustainable and water secure futures. However, the extent to which they can be implemented is subject to complex politics and powerful coalitions across multi-level governance systems and scales of interest. Exactly how innovation uptake can be best facilitated or blocked in these complex systems is thus a matter of important practical and research interest in water cycle management. From intervention research studies in Australia, China and Bulgaria, this paper seeks to describe and analyse the behind-the-scenes struggles and coalition-building that occurs between water utility providers, private companies, experts, communities and all levels of government in an effort to support or block specific innovations. The research findings suggest that in order to ensure successful passage of the proposed innovations, champions for it are required from at least two administrative levels, including one with innovation implementation capacity, as part of a larger supportive coalition. Higher governance levels can play an important enabling role in facilitating the passage of certain types of innovations that may be in competition with currently entrenched systems of water management. Due to a range of natural biases, experts on certain innovations and disciplines may form part of supporting or blocking coalitions but their evaluations of worth for water system sustainability and security are likely to be subject to competing claims based on different values and expertise, so may not necessarily be of use in resolving questions of "best courses of action". This remains a political values-based decision to be negotiated through the receiving multi-level water governance system.

  2. Multilevel Cortical Processing of Somatosensory Novelty: A Magnetoencephalography Study

    PubMed Central

    Naeije, Gilles; Vaulet, Thibaut; Wens, Vincent; Marty, Brice; Goldman, Serge; De Tiège, Xavier

    2016-01-01

    Using magnetoencephalography (MEG), this study investigates the spatio-temporal dynamics of the multilevel cortical processing of somatosensory change detection. Neuromagnetic signals of 16 healthy adult subjects (7 females and 9 males, mean age 29 ± 3 years) were recorded using whole-scalp-covering MEG while they underwent an oddball paradigm based on simple standard (right index fingertip tactile stimulation) and deviant (simultaneous right index fingertip and middle phalanx tactile stimulation) stimuli gathered into sequences to create and then deviate from stimulus patterns at multiple (local vs. global) levels of complexity. Five healthy adult subjects (3 females and 2 males, mean age 31, 6 ± 2 years) also underwent a similar oddball paradigm in which standard and deviant stimuli were flipped. Local deviations led to a somatosensory mismatch response peaking at 55–130 ms post-stimulus onset with a cortical generator located at the contralateral secondary somatosensory (cSII) cortex. The mismatch response was independent of the deviant stimuli physical characteristics. Global deviants led to a P300 response with cortical sources located bilaterally at temporo-parietal junction (TPJ) and supplementary motor area (SMA). The posterior parietal cortex (PPC) and the SMA were found to generate a contingent magnetic variation (CMV) attributed to top-down expectations. Amplitude of mismatch responses were modulated by top-down expectations and correlated with both the magnitude of the CMV and the P300 amplitude at the right TPJ. These results provide novel empirical evidence for a unified sensory novelty detection system in the human brain by linking detection of salient sensory stimuli in personal and extra-personal spaces to a common framework of multilevel cortical processing. PMID:27313523

  3. Comparison of Estimation Procedures for Multilevel AR(1) Models

    PubMed Central

    Krone, Tanja; Albers, Casper J.; Timmerman, Marieke E.

    2016-01-01

    To estimate a time series model for multiple individuals, a multilevel model may be used. In this paper we compare two estimation methods for the autocorrelation in Multilevel AR(1) models, namely Maximum Likelihood Estimation (MLE) and Bayesian Markov Chain Monte Carlo. Furthermore, we examine the difference between modeling fixed and random individual parameters. To this end, we perform a simulation study with a fully crossed design, in which we vary the length of the time series (10 or 25), the number of individuals per sample (10 or 25), the mean of the autocorrelation (−0.6 to 0.6 inclusive, in steps of 0.3) and the standard deviation of the autocorrelation (0.25 or 0.40). We found that the random estimators of the population autocorrelation show less bias and higher power, compared to the fixed estimators. As expected, the random estimators profit strongly from a higher number of individuals, while this effect is small for the fixed estimators. The fixed estimators profit slightly more from a higher number of time points than the random estimators. When possible, random estimation is preferred to fixed estimation. The difference between MLE and Bayesian estimation is nearly negligible. The Bayesian estimation shows a smaller bias, but MLE shows a smaller variability (i.e., standard deviation of the parameter estimates). Finally, better results are found for a higher number of individuals and time points, and for a lower individual variability of the autocorrelation. The effect of the size of the autocorrelation differs between outcome measures. PMID:27242559

  4. Multilevel Cortical Processing of Somatosensory Novelty: A Magnetoencephalography Study.

    PubMed

    Naeije, Gilles; Vaulet, Thibaut; Wens, Vincent; Marty, Brice; Goldman, Serge; De Tiège, Xavier

    2016-01-01

    Using magnetoencephalography (MEG), this study investigates the spatio-temporal dynamics of the multilevel cortical processing of somatosensory change detection. Neuromagnetic signals of 16 healthy adult subjects (7 females and 9 males, mean age 29 ± 3 years) were recorded using whole-scalp-covering MEG while they underwent an oddball paradigm based on simple standard (right index fingertip tactile stimulation) and deviant (simultaneous right index fingertip and middle phalanx tactile stimulation) stimuli gathered into sequences to create and then deviate from stimulus patterns at multiple (local vs. global) levels of complexity. Five healthy adult subjects (3 females and 2 males, mean age 31, 6 ± 2 years) also underwent a similar oddball paradigm in which standard and deviant stimuli were flipped. Local deviations led to a somatosensory mismatch response peaking at 55-130 ms post-stimulus onset with a cortical generator located at the contralateral secondary somatosensory (cSII) cortex. The mismatch response was independent of the deviant stimuli physical characteristics. Global deviants led to a P300 response with cortical sources located bilaterally at temporo-parietal junction (TPJ) and supplementary motor area (SMA). The posterior parietal cortex (PPC) and the SMA were found to generate a contingent magnetic variation (CMV) attributed to top-down expectations. Amplitude of mismatch responses were modulated by top-down expectations and correlated with both the magnitude of the CMV and the P300 amplitude at the right TPJ. These results provide novel empirical evidence for a unified sensory novelty detection system in the human brain by linking detection of salient sensory stimuli in personal and extra-personal spaces to a common framework of multilevel cortical processing. PMID:27313523

  5. Biomechanical Analysis of the Proximal Adjacent Segment after Multilevel Instrumentation of the Thoracic Spine: Do Hooks Ease the Transition?

    PubMed

    Metzger, Melodie F; Robinson, Samuel T; Svet, Mark T; Liu, John C; Acosta, Frank L

    2016-06-01

    Study Design Biomechanical cadaveric study. Objective Clinical studies indicate that using less-rigid fixation techniques in place of the standard all-pedicle screw construct when correcting for scoliosis may reduce the incidence of proximal junctional kyphosis and improve patient outcomes. The purpose of this study is to investigate whether there is a biomechanical advantage to using supralaminar hooks in place of pedicle screws at the upper-instrumented vertebrae in a multilevel thoracic construct. Methods T7-T12 spines were biomechanically tested: (1) intact; (2) following a two-level pedicles screw fusion from T9 to T11; and after proximal extension of the fusion to T8-T9 with (3) bilateral supra-laminar hooks, (4) a unilateral hook + unilateral screw hybrid, or (5) bilateral pedicle screws. Specimens were nondestructively loaded while three-dimensional kinematics and intradiscal pressure at the supra-adjacent level were recorded. Results Supra-adjacent hypermobility was reduced when bilateral hooks were used in place of pedicle screws at the upper-instrumented level, with statistically significant differences in lateral bending and torsion (p < 0.05 and p < 0.001, respectively). Disk pressures in the supra-adjacent segment were not statistically different among top-off techniques. Conclusions The use of supralaminar hooks at the top of a multilevel posterior fusion construct reduces the stress at the proximal uninstrumented motion segment. Although further data is needed to provide a definitive link to the clinical occurrence of PJK, this in vitro study demonstrates the potential benefit of "easing" the transition between the stiff instrumented spine and the flexible native spine and is the first to demonstrate these results with laminar hooks. PMID:27190735

  6. Multilevel Interventions To Address Health Disparities Show Promise In Improving Population Health.

    PubMed

    Paskett, Electra; Thompson, Beti; Ammerman, Alice S; Ortega, Alexander N; Marsteller, Jill; Richardson, DeJuran

    2016-08-01

    Multilevel interventions are those that affect at least two levels of influence-for example, the patient and the health care provider. They can be experimental designs or natural experiments caused by changes in policy, such as the implementation of the Affordable Care Act or local policies. Measuring the effects of multilevel interventions is challenging, because they allow for interaction among levels, and the impact of each intervention must be assessed and translated into practice. We discuss how two projects from the National Institutes of Health's Centers for Population Health and Health Disparities used multilevel interventions to reduce health disparities. The interventions, which focused on the uptake of the human papillomavirus vaccine and community-level dietary change, had mixed results. The design and implementation of multilevel interventions are facilitated by input from the community, and more advanced methods and measures are needed to evaluate the impact of the various levels and components of such interventions. PMID:27503968

  7. Multilevel Concatenated Block Modulation Codes for the Frequency Non-selective Rayleigh Fading Channel

    NASA Technical Reports Server (NTRS)

    Lin, Shu; Rhee, Dojun

    1996-01-01

    This paper is concerned with construction of multilevel concatenated block modulation codes using a multi-level concatenation scheme for the frequency non-selective Rayleigh fading channel. In the construction of multilevel concatenated modulation code, block modulation codes are used as the inner codes. Various types of codes (block or convolutional, binary or nonbinary) are being considered as the outer codes. In particular, we focus on the special case for which Reed-Solomon (RS) codes are used as the outer codes. For this special case, a systematic algebraic technique for constructing q-level concatenated block modulation codes is proposed. Codes have been constructed for certain specific values of q and compared with the single-level concatenated block modulation codes using the same inner codes. A multilevel closest coset decoding scheme for these codes is proposed.

  8. A Parallel Implementation of Multilevel Recursive Spectral Bisection for Application to Adaptive Unstructured Meshes. Chapter 1

    NASA Technical Reports Server (NTRS)

    Barnard, Stephen T.; Simon, Horst; Lasinski, T. A. (Technical Monitor)

    1994-01-01

    The design of a parallel implementation of multilevel recursive spectral bisection is described. The goal is to implement a code that is fast enough to enable dynamic repartitioning of adaptive meshes.

  9. GROUND WATER MONITORING AND SAMPLING: MULTI-LEVEL VERSUS TRADITIONAL METHODS – WHAT’S WHAT?

    EPA Science Inventory

    Recent studies have been conducted to evaluate different sampling techniques for determining VOC concentrations in groundwater. Samples were obtained using multi-level and traditional sampling techniques in three monitoring wells at the Raymark Superfund site in Stratford, CT. Ve...

  10. Translating the Socio-Ecological Perspective Into Multilevel Interventions: Gaps Between Theory and Practice.

    PubMed

    Schölmerich, Vera L N; Kawachi, Ichiro

    2016-02-01

    Multilevel interventions are inspired by socio-ecological models, and seek to create change on various levels-for example by increasing the health literacy of individuals as well as modifying the social norms within a community. Despite becoming a buzzword in public health, actual multilevel interventions remain scarce. In this commentary, we explore the operational and empirical barriers to designing and implementing multilevel interventions, and argue that the current theoretical framework based on the socio-ecological model is insufficient to guide those seeking to design multilevel interventions. We consider two theories, namely, the complementarity principle theory and the risk compensation theory-to address the gap between theory and translation into practice. PMID:26747715

  11. MULTILEVEL ACCELERATION OF STOCHASTIC COLLOCATION METHODS FOR PDE WITH RANDOM INPUT DATA

    SciTech Connect

    Webster, Clayton G; Jantsch, Peter A; Teckentrup, Aretha L; Gunzburger, Max D

    2013-01-01

    Stochastic Collocation (SC) methods for stochastic partial differential equa- tions (SPDEs) suffer from the curse of dimensionality, whereby increases in the stochastic dimension cause an explosion of computational effort. To combat these challenges, multilevel approximation methods seek to decrease computational complexity by balancing spatial and stochastic discretization errors. As a form of variance reduction, multilevel techniques have been successfully applied to Monte Carlo (MC) methods, but may be extended to accelerate other methods for SPDEs in which the stochastic and spatial degrees of freedom are de- coupled. This article presents general convergence and computational complexity analysis of a multilevel method for SPDEs, demonstrating its advantages with regard to standard, single level approximation. The numerical results will highlight conditions under which multilevel sparse grid SC is preferable to the more traditional MC and SC approaches.

  12. Reduction in overvoltages and dynamic power losses in power switches of multilevel voltage inverters

    NASA Astrophysics Data System (ADS)

    Voronin, P. A.; Voronin, I. P.; Panfilov, D. I.; Rozhkov, D. V.

    2014-12-01

    A number of the circuit and design decisions that provide a reduction in overvoltage and dynamic power losses in power switches of multilevel voltage inverters with clamping diodes is considered. It is shown that the integral or unpackaged version is the most effective method for a reduction in the stray inductance in the multilevel circuit, which is the general cause for occurrence of dynamic overvoltage. To reduce dynamic losses of power, a method for resonant commutation on fronts, which provides commutation of switches in the multilevel circuit at zero voltage (SZV) and zero current (SZC), is proposed. The resonant switching method as applied to the multilevel circuit simultaneously solves a problem of dynamic overvoltage by means of limitation for the rate of voltage rise in the SZV mode or the mode of preliminary fault of energy stored in the inductance of the switching circuit in the SZC mode.

  13. Fabrication of multilevel resist patterns by using a liquid crystal mask

    NASA Astrophysics Data System (ADS)

    Słupski, Piotr; Nikodem, Michał; Chai, Liming; Komorowska, Katarzyna

    2015-11-01

    Photolithographic processes of multilevel features in microfluidics can be complex and expensive. This paper demonstrates a quick method for manufacturing multilevel patterns, which is based on liquid crystal display masking during a standard lithography process for master mold fabrication for the polydimethysiloxane replica process. An active mask, based on a liquid crystal display, can simplify the process due to the ability to quickly modify designs and reduce the overhead for alignment between mask levels. The possibility of multilevel patterning, with the help of active masking, creates new opportunities for optical lithography processes. We have developed the process for a standard, mercury lamp exposure mask aligner system. The patterning characteristics were evaluated with a step pattern fabricated as an example of three-dimensional patterning for multilevel structuring. The application of a liquid crystal mask for resist contrast measurements was demonstrated.

  14. Load sensing system

    DOEpatents

    Sohns, Carl W.; Nodine, Robert N.; Wallace, Steven Allen

    1999-01-01

    A load sensing system inexpensively monitors the weight and temperature of stored nuclear material for long periods of time in widely variable environments. The system can include an electrostatic load cell that encodes weight and temperature into a digital signal which is sent to a remote monitor via a coaxial cable. The same cable is used to supply the load cell with power. When multiple load cells are used, vast

  15. Groundwater Age in Multi-Level Water Quality Monitor Wells on California Central Valley Dairies

    NASA Astrophysics Data System (ADS)

    Esser, B. K.; Visser, A.; Hillegonds, D. J.; Singleton, M. J.; Moran, J. E.; Harter, T.

    2011-12-01

    Dairy farming in California's Central Valley is a significant source of nitrate to underlying aquifers. One approach to mitigation is to implement farm-scale management plans that reduce nutrient loading to groundwater while sustaining crop yield. While the effect of different management practices on crop yield is easily measured, their effect on groundwater quality has only infrequently been evaluated. Documenting and predicting the impact of management on water quality requires a quantitative assessment of transport (including timescale and mixing) through the vadose and saturated zones. In this study, we measured tritium, helium isotopic composition, and noble gas concentrations in groundwater drawn from monitor wells on several dairies in the Lower San Joaquin Valley and Tulare Lake Basin of California's Central Valley in order to predict the timescales on which changes in management may produce observable changes in groundwater quality. These dairies differ in age (from <10 to >100 years old), thickness of the vadose zone (from <10 to 60 m), hydrogeologic setting, and primary source of irrigation water (surface or groundwater). All of the dairies use manure wastewater for irrigation and fertilization. Three of the dairies have implemented management changes designed to reduce nutrient loading and/or water usage. Monitor wells in the southern Tulare Lake Basin dairies were installed by UC-Davis as multi-level nested wells allowing depth profiling of tritium and noble gases at these sites. Tritium/helium-3 groundwater ages, calculated using a simple piston-flow model, range from <2 to >50 years. Initial tritium (the sum of measured tritium and tritiogenic helium-3) is close to or slightly above precipitation in the calculated recharge year for young samples; and significantly above the precipitation curve for older samples. This pattern is consistent with the use of 20-30 year old groundwater recharged before 1980 for irrigation, and illustrates how irrigation

  16. Taking a Load Off.

    ERIC Educational Resources Information Center

    Kenny, John

    1995-01-01

    Discusses the snow -load capacity of school roofs and how understanding this data aids in planning preventive measures and easing fear of roof collapse. Describes how to determine snow-load capacity, and explains the load-bearing behavior of flat versus sloped roofs. Collapse prevention measures are highlighted. (GR)

  17. Multilevel factor analysis of smokers' real-time negative affect ratings while quitting.

    PubMed

    Bold, Krysten W; Witkiewitz, Katie; McCarthy, Danielle E

    2016-09-01

    Smoking is a serious public health problem, and accurate real-time assessment of risk factors associated with smoking is critical to understanding smoking relapse. Negative affect is often described as a critical risk factor related to smoking relapse, and ecological momentary assessment (EMA) methods have been widely used to study real-time relations between negative affect and smoking. However, the factor structure of momentary negative affect ratings is unknown. The current investigation examined the multilevel factor structure and internal consistency of an EMA measure of negative affect. Daily assessments were collected for 1 week prequit and 3 weeks postquit from 113 adult daily smokers receiving nicotine replacement therapy and counseling to quit smoking. Results supported a 2-factor model with correlated but distinct agitation and distress factors, rather than a single-factor model of negative affect. The agitation factor was indicated by these items: impatient, tense/anxious, restless. The distress factor was indicated by these items: sad/depressed, upset, distressed. The 2-factor model had acceptable model fit and consistent factor loadings across 3 separate cessation phases: prequit, postquit with recent smoking, and postquit without recent smoking. The 2 factors were highly correlated, showed good internal consistency, and showed strong associations with theoretically relevant smoking and affect variables. Agitation was more strongly related to urge to smoke, and distress was more strongly related to recent stress. This study provides support for a 2-factor model of an EMA measure of negative affect and highlights distinct facets that may be useful for future investigations of affect and smoking. (PsycINFO Database Record PMID:27536999

  18. Multi-Level Experimental and Analytical Evaluation of Two Composite Energy Absorbers

    NASA Technical Reports Server (NTRS)

    Jackson, Karen E.; Littell, Justin D.; Fasanella, Edwin L.; Annett, Martin S.; Seal, Michael D., II

    2015-01-01

    Two composite energy absorbers were developed and evaluated at NASA Langley Research Center through multi-level testing and simulation performed under the Transport Rotorcraft Airframe Crash Testbed (TRACT) research program. A conical-shaped energy absorber, designated the conusoid, was evaluated that consisted of four layers of hybrid carbon-Kevlar plain weave fabric oriented at [+45 deg/-45 deg/-45 deg/+45 deg] with respect to the vertical, or crush, direction. A sinusoidal-shaped energy absorber, designated the sinusoid, was developed that consisted of hybrid carbon-Kevlar plain weave fabric face sheets, two layers for each face sheet oriented at +/-45deg with respect to the vertical direction and a closed-cell ELFOAM P200 polyisocyanurate (2.0-lb/cu ft) foam core. The design goal for the energy absorbers was to achieve average floor-level accelerations of between 25- and 40-g during the full-scale crash test of a retrofitted CH-46E helicopter airframe, designated TRACT 2. Variations in both designs were assessed through dynamic crush testing of component specimens. Once the designs were finalized, subfloor beams of each configuration were fabricated and retrofitted into a barrel section of a CH-46E helicopter. A vertical drop test of the barrel section was conducted onto concrete to evaluate the performance of the energy absorbers prior to retrofit into TRACT 2. The retrofitted airframe was crash tested under combined forward and vertical velocity conditions onto soil, which is characterized as a sand/clay mixture. Finite element models were developed of all test articles and simulations were performed using LS-DYNA, a commercial nonlinear explicit transient dynamic finite element code. Test-analysis results are presented for each energy absorber as comparisons of time-history responses, as well as predicted and experimental structural deformations and progressive damage under impact loading for each evaluation level.

  19. A plasma aerodynamic actuator supplied by a multilevel generator operating with different voltage waveforms

    NASA Astrophysics Data System (ADS)

    Borghi, Carlo A.; Cristofolini, Andrea; Grandi, Gabriele; Neretti, Gabriele; Seri, Paolo

    2015-08-01

    In this work a high voltage—high frequency generator for the power supply of a dielectric barrier discharge (DBD) plasma actuator for the aerodynamic control obtained by the electro-hydro-dynamic (EHD) interaction is described and tested. The generator can produce different voltage waveforms. The operating frequency is independent of the load characteristics and does not require impedance matching. The peak-to-peak voltage is 30 kV at a frequency up to 20 kHz and time variation rates up to 60 kV μs-1. The performance of the actuator when supplied by several voltage waveforms is investigated. The tests have been performed in still air at atmospheric pressure. Voltage and current time behaviors have been measured. The evaluation of the energy delivered to the actuator allowed the estimation of the periods in which the plasma was ignited. Vibrational and rotational temperatures of the plasma have been estimated through spectroscopic acquisitions. The flow field induced in the region above the surface of the DBD actuator has been studied and the EHD conversion efficiency has been evaluated for the voltage waveforms investigated. The nearly sinusoidal multilevel voltage of the proposed generator and the sinusoidal voltage waveform of a conventional ac generator obtain comparable plasma features, EHD effects, and efficiencies. Inverse saw tooth waveform presents the highest effects and efficiency. The rectangular waveform generates suitable EHD effects but with the lowest efficiency. The voltage waveforms that induce plasmas with higher rotational temperatures are less efficient for the conversion of the electric into kinetic energy.

  20. Making the most of clustered data in laboratory animal research using multi-level models.

    PubMed

    Pearl, David L

    2014-01-01

    In the following review article, I address the fitting of multi-level models for the analysis of hierarchical data in laboratory animal medicine. Using an example of paternal dietary effects on the weight of offspring in a mouse model, this review outlines the reasons and benefits of using a multi-level modeling approach. To start, the concept of clustered/autocorrelated data is introduced, and the implications of ignoring the effects of clustered data on measures of association/model coefficients and their statistical significance are discussed. The limitations of other methods compared with multi-level modeling for analyzing clustered data are addressed in terms of statistical power, control of potential confounding effects associated with group membership, proper estimation of associations and their statistical significance, and adjusting for multiple levels of clustering. In addition, the benefits of being able to estimate variance partition coefficients and intra-class correlation coefficients from multi-level models is described, and the concepts of more complex correlation structures and various methods for fitting multi-level models are introduced. The current state of learning materials including textbooks, websites, and software for the nonstatistician is outlined to describe the accessibility of multi-level modeling approaches for laboratory animal researchers. PMID:25541550

  1. Multilevel multiple imputation: A review and evaluation of joint modeling and chained equations imputation.

    PubMed

    Enders, Craig K; Mistler, Stephen A; Keller, Brian T

    2016-06-01

    Although missing data methods have advanced in recent years, methodologists have devoted less attention to multilevel data structures where observations at level-1 are nested within higher-order organizational units at level-2 (e.g., individuals within neighborhoods; repeated measures nested within individuals; students nested within classrooms). Joint modeling and chained equations imputation are the principal imputation frameworks for single-level data, and both have multilevel counterparts. These approaches differ algorithmically and in their functionality; both are appropriate for simple random intercept analyses with normally distributed data, but they differ beyond that. The purpose of this paper is to describe multilevel imputation strategies and evaluate their performance in a variety of common analysis models. Using multiple imputation theory and computer simulations, we derive 4 major conclusions: (a) joint modeling and chained equations imputation are appropriate for random intercept analyses; (b) the joint model is superior for analyses that posit different within- and between-cluster associations (e.g., a multilevel regression model that includes a level-1 predictor and its cluster means, a multilevel structural equation model with different path values at level-1 and level-2); (c) chained equations imputation provides a dramatic improvement over joint modeling in random slope analyses; and (d) a latent variable formulation for categorical variables is quite effective. We use a real data analysis to demonstrate multilevel imputation, and we suggest a number of avenues for future research. (PsycINFO Database Record PMID:26690775

  2. Translating the Social-Ecological Perspective Into Multilevel Interventions for Family Planning: How Far Are We?

    PubMed

    Schölmerich, Vera L N; Kawachi, Ichiro

    2016-06-01

    Scholars and practitioners frequently make recommendations to develop family planning interventions that are "multilevel." Such interventions take explicit account of the role of environments by incorporating multilevel or social-ecological frameworks into their design and implementation. However, research on how interventions have translated these concepts into practice in the field of family planning-and generally in public health-remains scarce. This article seeks to review the current definitions of multilevel interventions and their operationalization in the field of family planning. First, we highlight the divergent definitions of multilevel interventions and show the persistent ambiguity around this term. We argue that interventions involving activities at several levels but lacking targets (i.e., objectives) to create change on more than one level have not incorporated a social-ecological framework and should therefore not be considered as "multilevel." In a second step, we assess the extent to which family planning interventions have successfully incorporated a social-ecological framework. To this end, the 63 studies featured in Mwaikambo et al.'s systematic review on family planning interventions were reexamined. This assessment indicates that the multilevel or social-ecological perspective has seldom been translated into interventions. Specifically, the majority of interventions involved some form of activity at the community and/or organizational level, yet targeted and measured intrapersonal change as opposed to explicitly targeting/measuring environmental modification. PMID:27105643

  3. Multilevel Models for the Analysis of Angle-Specific Torque Curves with Application to Master Athletes

    PubMed Central

    Carvalho, Humberto M

    2015-01-01

    The aim of this paper was to outline a multilevel modeling approach to fit individual angle-specific torque curves describing concentric knee extension and flexion isokinetic muscular actions in Master athletes. The potential of the analytical approach to examine between individual differences across the angle-specific torque curves was illustrated including between-individuals variation due to gender differences at a higher level. Torques in concentric muscular actions of knee extension and knee extension at 60º·s−1 were considered within a range of motion between 5º and 85º (only torques “truly” isokinetic). Multilevel time series models with autoregressive covariance structures with standard multilevel models were superior fits compared with standard multilevel models for repeated measures to fit angle-specific torque curves. Third and fourth order polynomial models were the best fits to describe angle-specific torque curves of isokinetic knee flexion and extension concentric actions, respectively. The fixed exponents allow interpretations for initial acceleration, the angle at peak torque and the decrement of torque after peak torque. Also, the multilevel models were flexible to illustrate the influence of gender differences on the shape of torque throughout the range of motion and in the shape of the curves. The presented multilevel regression models may afford a general framework to examine angle-specific moment curves by isokinetic dynamometry, and add to the understanding mechanisms of strength development, particularly the force-length relationship, both related to performance and injury prevention. PMID:26839603

  4. Multilevel Green's function interpolation method for scattering from composite metallic and dielectric objects.

    PubMed

    Shi, Yan; Wang, Hao Gang; Li, Long; Chan, Chi Hou

    2008-10-01

    A multilevel Green's function interpolation method based on two kinds of multilevel partitioning schemes--the quasi-2D and the hybrid partitioning scheme--is proposed for analyzing electromagnetic scattering from objects comprising both conducting and dielectric parts. The problem is formulated using the surface integral equation for homogeneous dielectric and conducting bodies. A quasi-2D multilevel partitioning scheme is devised to improve the efficiency of the Green's function interpolation. In contrast to previous multilevel partitioning schemes, noncubic groups are introduced to discretize the whole EM structure in this quasi-2D multilevel partitioning scheme. Based on the detailed analysis of the dimension of the group in this partitioning scheme, a hybrid quasi-2D/3D multilevel partitioning scheme is proposed to effectively handle objects with fine local structures. Selection criteria for some key parameters relating to the interpolation technique are given. The proposed algorithm is ideal for the solution of problems involving objects such as missiles, microstrip antenna arrays, photonic bandgap structures, etc. Numerical examples are presented to show that CPU time is between O(N) and O(N log N) while the computer memory requirement is O(N). PMID:18830332

  5. Comparing Spatial and Multilevel Regression Models for Binary Outcomes in Neighborhood Studies

    PubMed Central

    Xu, Hongwei

    2013-01-01

    The standard multilevel regressions that are widely used in neighborhood research typically ignore potential between-neighborhood correlations due to underlying spatial processes, and hence produce inappropriate inferences about neighborhood effects. In contrast, spatial models make estimations and predictions across areas by explicitly modeling the spatial correlations among observations in different locations. A better understanding of the strengths and limitations of spatial models as compared to the standard multilevel model is needed to improve the research on neighborhood and spatial effects. This research systematically compares model estimations and predictions for binary outcomes between (distance- and lattice-based) spatial and the standard multilevel models in the presence of both within- and between-neighborhood correlations, through simulations. Results from simulation analysis reveal that the standard multilevel and spatial models produce similar estimates of fixed effects, but different estimates of random effects variances. Both the standard multilevel and pure spatial models tend to overestimate the corresponding random effects variances, compared to hybrid models when both non-spatial within neighborhood and spatial between-neighborhood effects exist. Spatial models also outperform the standard multilevel model by a narrow margin in case of fully out-of-sample predictions. Distance-based spatial models provide extra spatial information and have stronger predictive power than lattice-based models under certain circumstances. These merits of spatial modeling are exhibited in an empirical analysis of the child mortality data from 1880 Newark, New Jersey. PMID:25284905

  6. Multilevel data analysis of a crossover designed human nutritional intervention study.

    PubMed

    van Velzen, Ewoud J J; Westerhuis, Johan A; van Duynhoven, John P M; van Dorsten, Ferdi A; Hoefsloot, Huub C J; Jacobs, Doris M; Smit, Suzanne; Draijer, Richard; Kroner, Christine I; Smilde, Age K

    2008-10-01

    A new method is introduced for the analysis of 'omics' data derived from crossover designed drug or nutritional intervention studies. The method aims at finding systematic variations in metabolic profiles after a drug or nutritional challenge and takes advantage of the crossover design in the data. The method, which can be considered as a multivariate extension of a paired t test, generates different multivariate submodels for the between- and the within-subject variation in the data. A major advantage of this variation splitting is that each submodel can be analyzed separately without being confounded with the other variation sources. The power of the multilevel approach is demonstrated in a human nutritional intervention study which used NMR-based metabolomics to assess the metabolic impact of grape/wine extract consumption. The variations in the urine metabolic profiles are studied between and within the human subjects using the multilevel analysis. After variation splitting, multilevel PCA is used to investigate the experimental and biological differences between the subjects, whereas a multilevel PLS-DA model is used to reveal the net treatment effect within the subjects. The observed treatment effect is validated with cross model validation and permutations. It is shown that the statistical significance of the multilevel classification model ( p < 0.0002) is a major improvement compared to a ordinary PLS-DA model ( p = 0.058) without variation splitting. Finally, rank products are used to determine which NMR signals are most important in the multilevel classification model. PMID:18754629

  7. Load Model Data Tool

    SciTech Connect

    David Chassin, Pavel Etingov

    2013-04-30

    The LMDT software automates the process of the load composite model data preparation in the format supported by the major power system software vendors (GE and Siemens). Proper representation of the load composite model in power system dynamic analysis is very important. Software tools for power system simulation like GE PSLF and Siemens PSSE already include algorithms for the load composite modeling. However, these tools require that the input information on composite load to be provided in custom formats. Preparation of this data is time consuming and requires multiple manual operations. The LMDT software enables to automate this process. Software is designed to generate composite load model data. It uses the default load composition data, motor information, and bus information as an input. Software processes the input information and produces load composition model. Generated model can be stored in .dyd format supported by GE PSLF package or .dyr format supported by Siemens PSSE package.

  8. Load Model Data Tool

    Energy Science and Technology Software Center (ESTSC)

    2013-04-30

    The LMDT software automates the process of the load composite model data preparation in the format supported by the major power system software vendors (GE and Siemens). Proper representation of the load composite model in power system dynamic analysis is very important. Software tools for power system simulation like GE PSLF and Siemens PSSE already include algorithms for the load composite modeling. However, these tools require that the input information on composite load to bemore » provided in custom formats. Preparation of this data is time consuming and requires multiple manual operations. The LMDT software enables to automate this process. Software is designed to generate composite load model data. It uses the default load composition data, motor information, and bus information as an input. Software processes the input information and produces load composition model. Generated model can be stored in .dyd format supported by GE PSLF package or .dyr format supported by Siemens PSSE package.« less

  9. Amplitude and phase modulated 8-ary and 16-ary multilevel signaling technologies for high-speed optical fiber communication

    NASA Astrophysics Data System (ADS)

    Kikuchi, Nobuhiko

    2005-11-01

    The optical multilevel modulation is one of the attractive candidates to significantly increase the channel bit rate and total capacity of future optical fiber communications. We review various multilevel modulation schemes proposed to date, including our experimental results of the 8-level and 16-level APSK modulation/demodulation schemes at 10 Gsymbol/s. We also discuss the advantages and disadvantages, and future issues of the optical multilevel modulation schemes.

  10. Abstract: An International Comparison of Private and Public Schools Using Multilevel Propensity Score Methods and Graphics.

    PubMed

    Bryer, Jason M; Pruzek, Robert M

    2011-11-30

    As can be seen from the recent Special Issue of MBR on propensity score analysis (PSA) methods, the use of PSA has gained increasing popularity for estimating causal effects in observational studies. However, PSA use with multilevel or clustered data has been limited, and to date there seems to have been no development of specialized graphics for such data. This paper introduces the multilevelPSA ( http://multilevelPSA.r-forge.r-project.org ) package for R that provides cluster-based functions for estimating propensity scores as well as graphics to exhibit results for multilevel data. This work extends to the multilevel case the framework for visualizing propensity score analysis introduced by Helmreich and Pruzek (2009). International data from the Programme for International Student Assessment (Organization for Economic Co-operation and Development, 2009) are comprehensively examined to compare private with public schools on reading, mathematics, and science outcomes after adjusting for covariate differences in the multilevel context. Particularly for analyses of large data sets, focusing on statistical significance is limiting. As can readily be seen, overall results favor "private" over "public" schools, at least for end of secondary school math achievement. But the graphics provide a more nuanced understanding of the nature and magnitude of adjusted differences for countries. Furthermore, the graphics are readily interpreted by a nontechnical audience. Broadly speaking, it is seen that modern graphics can enhance and extend conventional numerical summaries by focusing on details of what data have to say for multilevel comparisons of many countries based on propensity score methods. PMID:26736126

  11. Phalange Tactile Load Cell

    NASA Technical Reports Server (NTRS)

    Ihrke, Chris A. (Inventor); Diftler, Myron A. (Inventor); Linn, Douglas Martin (Inventor); Platt, Robert (Inventor); Griffith, Bryan Kristian (Inventor)

    2010-01-01

    A tactile load cell that has particular application for measuring the load on a phalange in a dexterous robot system. The load cell includes a flexible strain element having first and second end portions that can be used to mount the load cell to the phalange and a center portion that can be used to mount a suitable contact surface to the load cell. The strain element also includes a first S-shaped member including at least three sections connected to the first end portion and the center portion and a second S-shaped member including at least three sections coupled to the second end portion and the center portion. The load cell also includes eight strain gauge pairs where each strain gauge pair is mounted to opposing surfaces of one of the sections of the S-shaped members where the strain gauge pairs provide strain measurements in six-degrees of freedom.

  12. Totally parallel multilevel algorithms for sparse elliptic systems

    NASA Technical Reports Server (NTRS)

    Frederickson, Paul O.

    1989-01-01

    The fastest known algorithms for the solution of a large elliptic boundary value problem on a massively parallel hypercube all require O(log(n)) floating point operations and O(log(n)) distance-1 communications, if massively parallel is defined to mean a number of processors proportional to the size n of the problem. The Totally Parallel Multilevel Algorithm (TPMA) that has, as special cases, four of these fast algorithms is described. These four algorithms are Parallel Superconvergent Multigrid (PSMG), Robust Multigrid, the Fast Fourier Transformation (FFT) based Spectral Algorithm, and Parallel Cyclic Reduction. The algorithm TPMA, when described recursively, has four steps: (1) project to a collection of interlaced, coarser problems at the next lower level; (2) apply TPMA, recursively, to each of these lower level problems, solving directly at the lowest level; (3) interpolate these approximate solutions to the finer grid, and to verage them to form an approximate solution on this grid; and (4) refine this approximate solution with a defect-correction step, using a local approximate inverse. Choice of the projection operator (P), the interpolation operator (Q), and the smoother (S) determines the class of problems on which TPMA is most effective. There are special cases in which the first three steps produce an exact solution, and the smoother is not needed (e.g., constant coefficient operators).

  13. New multilevel DCT, feature vectors, and universal blind steganalysis

    NASA Astrophysics Data System (ADS)

    Agaian, Sos S.; Cai, Hong

    2005-03-01

    Universal blind steganalysis can detect hidden messages without using prior information about the steganographic system. Recently, Farid developed a wavelet coefficient, higher-order statistics based, universal blind steganalysis method. This approach is a global method which demonstrated a high-quality in performance standards. Fridrich and Goljan also presented a DCT based local targeted steganalysis method to break the F5 algorithm. However, both Farid"s and Fridrich and Goljan"s methods have some limitations. This paper presents a local universal steganalysis technique combining the advantages of both methods. The basic components of the presented method are: novel DCT multilevel decomposition with wavelet structure; a new set of feature vectors; and a modified kernel function in the Kernel Fisher Discriminant. Experimental results show the presented method offers better performance than commonly used schemes. Inherently, the presented method has the ability to localize the hidden information, it can capture stego information in small blocks, and it is functional using only a small training set.

  14. [Multilevel revascularization of the lower extremities using loop endarterectomy].

    PubMed

    Losev, R Z; Burov, Iu A; Mikul'skaia, E G; Eliseev, A A; Bogdanova, N B; Skriabin, V V

    2006-01-01

    Results of 91 reconstructions of the ilio-femoro-popliteal segment in patients with multilevel injuries of the lower extremity arteries were analyzed. In 42 of the operations a method of operations associated with loop endarterectomy was used. The first stage in all the patients consisted of iliac deep femoral reconstructions or semi-closed loop endarterectomy from iliac arteries in order for inclusion in blood flow of the profound femoral artery. In the presence of the volumetric blood flow along the profound femoral artery less than 150 ml/min after the first stage of revascularization the operation volume was extended at the expense of the femoro-distal reconstructions and/or semi-closed loop endarterectomy from the femoral and popliteal arteries. It was found that revascularization of the ilio-femoral segment in combination with desobliteration of the popliteal artery allowed performing two-level reconstructions with little time and material costs followed by primary positive results in 92.9% of cases. PMID:17315682

  15. [Nutritional status of elderly Brazilians: a multilevel approach].

    PubMed

    Pereira, Ingrid Freitas da Silva; Spyrides, Maria Helena Constantino; Andrade, Lára de Melo Barbosa

    2016-06-01

    The objectives of this study were to diagnose the nutritional status of the elderly Brazilian population and to identify associated factors. The study used data from the Brazilian Household Budget Survey (2008/2009) for 20,114 elderly, whose nutritional status was assessed by body mass index (BMI). Associated factors were tested with the Pearson chi-square test and multilevel linear models. The hierarchical analysis showed a significant effect of state of Brazil on BMI variance (p-value = 0.001). The individual level showed a negative association (p-value < 0.001) with Asian-descendant race, male gender, living alone, and older age and a positive association with per capita income. Underweight was more prevalent among elderly in rural areas (26.3%) and in the Northeast (23.7%) and Central regions (20.9%), and obesity was more prevalent in the South (45.1%) and Southeast (38.3%) and in cities (39%). The study suggests the importance of further in-depth research on nutritional status of elderly based on contextual variables. PMID:27276697

  16. Intracavity self-induced transparency of a multilevel absorber

    NASA Astrophysics Data System (ADS)

    Müller, M.; Kalosha, V. P.; Herrmann, J.

    1998-08-01

    Intracavity self-induced transparency of a three-level absorber is studied in the scope of solid-state laser generation of an ultrabroadband electromagnetic pulse that drives the population of all absorber levels through complete Rabi flopping. We show that at sufficient pump rates a Ti:sapphire laser forces an intracavity GaAs single quantum-well absorber, which provides an inter-valence-band transition in the THz domain in addition to two direct optical interband transitions, into the self-induced transparency regime and acts as an all-solid-state ultrabroadband pulse emitter. In dependence on the resonator bandwidth, the intracavity pulse energy and the absorber dipole moments we obtain a multilevel self-induced transparency pulse spectrum which extends from the THz domain up to the ultraviolet. The steady-state sub-10-fs pulse consists of only a few optical cycles with the high-frequency components at its leading edge and a single to subcyclic THz component at its trailing edge.

  17. National INFOSEC technical baseline: multi-level secure systems

    SciTech Connect

    Anderson, J P

    1998-09-28

    The purpose of this report is to provide a baseline description of the state of multilevel processor/processing to the INFOSEC Research Council and at their discretion to the R&D community at large. From the information in the report, it is hoped that the members of the IRC will be aware of gaps in MLS research. A primary purpose is to bring IRC and the research community members up to date on what is happening in the MLS arena. The review will attempt to cover what MLS products are still available, and to identify companies who still offer MLS products. We have also attempted to identify requirements for MLS by interviewing senior officers of the Intelligence community as well as those elements of DoD and DOE who are or may be interested in procuring MLS products for various applications. The balance of the report consists of the following sections; a background review of the highlights of the developments of MLS, a quick summary of where we are today in terms of products, installations, and companies who are still in the business of supplying MLS systems [or who are developing MLS system], the requirements as expressed by senior members of the Intelligence community and DoD and DOE, issues and unmet R&D challenges surrounding MLS, and finally a set of recommended research topics.

  18. A multilevel adaptive projection method for unsteady incompressible flow

    NASA Technical Reports Server (NTRS)

    Howell, Louis H.

    1993-01-01

    There are two main requirements for practical simulation of unsteady flow at high Reynolds number: the algorithm must accurately propagate discontinuous flow fields without excessive artificial viscosity, and it must have some adaptive capability to concentrate computational effort where it is most needed. We satisfy the first of these requirements with a second-order Godunov method similar to those used for high-speed flows with shocks, and the second with a grid-based refinement scheme which avoids some of the drawbacks associated with unstructured meshes. These two features of our algorithm place certain constraints on the projection method used to enforce incompressibility. Velocities are cell-based, leading to a Laplacian stencil for the projection which decouples adjacent grid points. We discuss features of the multigrid and multilevel iteration schemes required for solution of the resulting decoupled problem. Variable-density flows require use of a modified projection operator--we have found a multigrid method for this modified projection that successfully handles density jumps of thousands to one. Numerical results are shown for the 2D adaptive and 3D variable-density algorithms.

  19. Direct-push multilevel sampling system for unconsolidated aquifers

    NASA Astrophysics Data System (ADS)

    Ducommun, Pascale; Boutsiadou, Xenia; Hunkeler, Daniel

    2013-12-01

    An economical multilevel groundwater monitoring system has been developed that can be rapidly installed with a direct-push machine, yet is suitable for sampling across large permeability contrasts. This sealed multiport sampling (SMPS) system consists of up to five lengths of PVC tubing (12 mm OD), each with a screen at a specific depth created by drilling 2.5-mm holes. Above and below each screen, round elastomer pieces, with peripheral holes (to clip in the sampling tubes) and a central hole (to hold a discontinuous piece of central tubing at the height of the screen), are emplaced. Cement-bentonite grout is injected via a tremie tube inserted through the discontinuous centre tube into each interval between the sampling screens. The elastomer pieces and central tube prevent grout from reaching the screened interval. A textile wrapped around the system holds the arrangement in place and at the same time serves to filter the groundwater at the level of the sampling screens. The SMPS system was tested at a tetrachloroethene (PCE) contaminated site. The seals effectively separated the sampling intervals even in heterogeneous formations. Furthermore, concentration profiles agreed well with a reference system. The system should be suitable for a wide range of hydrogeological conditions.

  20. Natural Resource Monitoring of Rheum tanguticum by Multilevel Remote Sensing

    PubMed Central

    Xie, Caixiang; Song, Jingyuan; Suo, Fengmei; Li, Xiwen; Li, Ying; Yu, Hua; Xu, Xiaolan; Luo, Kun; Li, Qiushi; Xin, Tianyi; Guan, Meng; Xu, Xiuhai; Miki, Eiji; Takeda, Osami; Chen, Shilin

    2014-01-01

    Remote sensing has been extensively applied in agriculture for its objectiveness and promptness. However, few applications are available for monitoring natural medicinal plants. In the paper, a multilevel monitoring system, which includes satellite and aerial remote sensing, as well as ground investigation, was initially proposed to monitor natural Rheum tanguticum resource in Baihe Pasture, Zoige County, Sichuan Province. The amount of R. tanguticum from images is M = S*ρ and S is vegetation coverage obtained by satellite imaging, whereas ρ is R. tanguticum density obtained by low-altitude imaging. Only the R. tanguticum which coverages exceeded 1 m2 could be recognized from the remote sensing image because of the 0.1 m resolution of the remote sensing image (called effective resource at that moment), and the results of ground investigation represented the amounts of R. tanguticum resource in all sizes (called the future resource). The data in paper showed that the present available amount of R. tanguticum accounted for 4% to 5% of the total quantity. The quantity information and the population structure of R. tanguticum in the Baihe Pasture were initially confirmed by this system. It is feasible to monitor the quantitative distribution for natural medicinal plants with scattered distribution. PMID:25101134

  1. Simulations of the bichromatic force in multilevel systems

    NASA Astrophysics Data System (ADS)

    Aldridge, L.; Galica, S. E.; Eyler, E. E.

    2016-01-01

    Coherent optical bichromatic forces have been shown to be effective tools for rapidly slowing and cooling simple atomic systems. While previous estimates suggest that these forces may also be effective for rapidly decelerating molecules or complex atoms, a quantitative treatment for multilevel systems has been lacking. We describe detailed numerical modeling of bichromatic forces by direct numerical solution for the time-dependent density matrix in the rotating-wave approximation. We describe both the general phenomenology of an arbitrary few-level system and the specific requirements for slowing and cooling on a many-level transition in calcium monofluoride (CaF), one of the molecules of greatest current experimental interest. We show that it should be possible to decelerate a cryogenic buffer-gas-cooled beam of CaF nearly to rest without a repumping laser and within a longitudinal distance of about 1 cm. We also compare a full 16-level simulation for the CaF B ↔X system with a simplified numerical model and with a semiquantitative estimate based on two-level systems. The simplified model performs nearly as well as the complete version, whereas the two-level model is useful for making order-of-magnitude estimates, but nothing more.

  2. Multilevel Context of Depression in Two American Indian Tribes

    PubMed Central

    Kaufman, Carol E.; Beals, Janette; Croy, Calvin; Jiang, Luohua; Novins, Douglas K.

    2015-01-01

    Objective Depression is a major debilitating disease. For American Indians living in tribal reservations, who endure disproportionately high levels of stress and poverty often associated with depression, determining the patterns and correlates is key to appropriate clinical assessment and intervention development. Yet, little attention has been given to the cultural context of correlates for depression, including the influence of family, cultural traditions or practices, or community conditions. Method We used data from a large representative psychiatric epidemiological study among American Indians in two reservation communities to estimate nested individual and multilevel models of past-year Major Depressive Episode (MDE) accounting for family, cultural, and community conditions. Results We found that models including culturally informed individual-level measures significantly improved the model fit over demographics alone. We found significant community-level variation in the probability of past-year MDE diagnosis in one tribe even after accounting for individual-level characteristics. Conclusions Accounting for culture, family, and community context will facilitate research, clinician assessment, and treatment of depression in diverse settings. PMID:24016293

  3. Implicit extrapolation methods for multilevel finite element computations

    SciTech Connect

    Jung, M.; Ruede, U.

    1994-12-31

    The finite element package FEMGP has been developed to solve elliptic and parabolic problems arising in the computation of magnetic and thermomechanical fields. FEMGP implements various methods for the construction of hierarchical finite element meshes, a variety of efficient multilevel solvers, including multigrid and preconditioned conjugate gradient iterations, as well as pre- and post-processing software. Within FEMGP, multigrid {tau}-extrapolation can be employed to improve the finite element solution iteratively to higher order. This algorithm is based on an implicit extrapolation, so that the algorithm differs from a regular multigrid algorithm only by a slightly modified computation of the residuals on the finest mesh. Another advantage of this technique is, that in contrast to explicit extrapolation methods, it does not rely on the existence of global error expansions, and therefore neither requires uniform meshes nor global regularity assumptions. In the paper the authors will analyse the {tau}-extrapolation algorithm and present experimental results in the context of the FEMGP package. Furthermore, the {tau}-extrapolation results will be compared to higher order finite element solutions.

  4. Evolution of neuroarchitecture, multi-level analyses and calibrative reductionism

    PubMed Central

    Berntson, Gary G.; Norman, Greg J.; Hawkley, Louise C.; Cacioppo, John T.

    2012-01-01

    Evolution has sculpted the incredibly complex human nervous system, among the most complex functions of which extend beyond the individual to an intricate social structure. Although these functions are deterministic, those determinants are legion, heavily interacting and dependent on a specific evolutionary trajectory. That trajectory was directed by the adaptive significance of quasi-random genetic variations, but was also influenced by chance and caprice. With a different evolutionary pathway, the same neural elements could subserve functions distinctly different from what they do in extant human brains. Consequently, the properties of higher level neural networks cannot be derived readily from the properties of the lower level constituent elements, without studying these elements in the aggregate. Thus, a multi-level approach to integrative neuroscience may offer an optimal strategy. Moreover, the process of calibrative reductionism, by which concepts and understandings from one level of organization or analysis can mutually inform and ‘calibrate’ those from other levels (both higher and lower), may represent a viable approach to the application of reductionism in science. This is especially relevant in social neuroscience, where the basic subject matter of interest is defined by interacting organisms across diverse environments. PMID:23386961

  5. Multi-level segment analysis: definition and applications in turbulence

    NASA Astrophysics Data System (ADS)

    Wang, Lipo

    2015-11-01

    The interaction of different scales is among the most interesting and challenging features in turbulence research. Existing approaches used for scaling analysis such as structure-function and Fourier spectrum method have their respective limitations, for instance scale mixing, i.e. the so-called infrared and ultraviolet effects. For a given function, by specifying different window sizes, the local extremal point set will be different. Such window size dependent feature indicates multi-scale statistics. A new method, multi-level segment analysis (MSA) based on the local extrema statistics, has been developed. The part of the function between two adjacent extremal points is defined as a segment, which is characterized by the functional difference and scale difference. The structure function can be differently derived from these characteristic parameters. Data test results show that MSA can successfully reveal different scaling regimes in turbulence systems such as Lagrangian and two-dimensional turbulence, which have been remaining controversial in turbulence research. In principle MSA can generally be extended for various analyses.

  6. Predicting perceived risk of crime: a multilevel study.

    PubMed

    Russo, Silvia; Roccato, Michele; Vieno, Alessio

    2011-12-01

    With a sample of Italians selected from 71 Italian counties (N = 1,868), we performed two multilevel analyses aimed at predicting the perceived risk of crime at local (i.e., in the participants' county of residence) and at societal (i.e., in the context of Italian society) levels. A significant proportion of the variation in local risk perception was at the county level. The following individual variables predicted higher levels of this variable: indirect victimization, the perception of social and physical disorder, being a woman, being poorly educated, and being an older person. Among the ecological predictors, the crime rate and unemployment rate predicted higher levels of local crime risk perception, while the immigrant rate did not. Perceived risk of crime at the societal level did not show significant variation at the county level. Education, being a man, trusting people, and adhesion to post-materialistic values predicted lower levels of societal crime risk perception, while number of sons/daughters and exposure to television news increased it. The limitations and possible development of this study are discussed. PMID:21161721

  7. Multi-level molecular modelling for plasma medicine

    NASA Astrophysics Data System (ADS)

    Bogaerts, Annemie; Khosravian, Narjes; Van der Paal, Jonas; Verlackt, Christof C. W.; Yusupov, Maksudbek; Kamaraj, Balu; Neyts, Erik C.

    2016-02-01

    Modelling at the molecular or atomic scale can be very useful for obtaining a better insight in plasma medicine. This paper gives an overview of different atomic/molecular scale modelling approaches that can be used to study the direct interaction of plasma species with biomolecules or the consequences of these interactions for the biomolecules on a somewhat longer time-scale. These approaches include density functional theory (DFT), density functional based tight binding (DFTB), classical reactive and non-reactive molecular dynamics (MD) and united-atom or coarse-grained MD, as well as hybrid quantum mechanics/molecular mechanics (QM/MM) methods. Specific examples will be given for three important types of biomolecules, present in human cells, i.e. proteins, DNA and phospholipids found in the cell membrane. The results show that each of these modelling approaches has its specific strengths and limitations, and is particularly useful for certain applications. A multi-level approach is therefore most suitable for obtaining a global picture of the plasma-biomolecule interactions.

  8. Remote sensing image compression assessment based on multilevel distortions

    NASA Astrophysics Data System (ADS)

    Jiang, Hongxu; Yang, Kai; Liu, Tingshan; Zhang, Yongfei

    2014-01-01

    The measurement of visual quality is of fundamental importance to remote sensing image compression, especially for image quality assessment and compression algorithm optimization. We exploit the distortion features of optical remote sensing image compression and propose a full-reference image quality metric based on multilevel distortions (MLD), which assesses image quality by calculating distortions of three levels (such as pixel-level, contexture-level, and content-level) between original images and compressed images. Based on this, a multiscale MLD (MMLD) algorithm is designed and it outperforms the other current methods in our testing. In order to validate the performance of our algorithm, a special remote sensing image compression distortion (RICD) database is constructed, involving 250 remote sensing images compressed with different algorithms and various distortions. Experimental results on RICD and Laboratory for Image and Video Engineering databases show that the proposed MMLD algorithm has better consistency with subjective perception values than current state-of-the-art methods in remote sensing image compression assessment, and the objective assessment results can show the distortion features and visual quality of compressed image well. It is suitable to be the evaluation criteria for optical remote sensing image compression.

  9. A multi-level typology of abstract visualization tasks.

    PubMed

    Brehmer, Matthew; Munzner, Tamara

    2013-12-01

    The considerable previous work characterizing visualization usage has focused on low-level tasks or interactions and high-level tasks, leaving a gap between them that is not addressed. This gap leads to a lack of distinction between the ends and means of a task, limiting the potential for rigorous analysis. We contribute a multi-level typology of visualization tasks to address this gap, distinguishing why and how a visualization task is performed, as well as what the task inputs and outputs are. Our typology allows complex tasks to be expressed as sequences of interdependent simpler tasks, resulting in concise and flexible descriptions for tasks of varying complexity and scope. It provides abstract rather than domain-specific descriptions of tasks, so that useful comparisons can be made between visualization systems targeted at different application domains. This descriptive power supports a level of analysis required for the generation of new designs, by guiding the translation of domain-specific problems into abstract tasks, and for the qualitative evaluation of visualization usage. We demonstrate the benefits of our approach in a detailed case study, comparing task descriptions from our typology to those derived from related work. We also discuss the similarities and differences between our typology and over two dozen extant classification systems and theoretical frameworks from the literatures of visualization, human-computer interaction, information retrieval, communications, and cartography. PMID:24051804

  10. Evolution of neuroarchitecture, multi-level analyses and calibrative reductionism.

    PubMed

    Berntson, Gary G; Norman, Greg J; Hawkley, Louise C; Cacioppo, John T

    2012-02-01

    Evolution has sculpted the incredibly complex human nervous system, among the most complex functions of which extend beyond the individual to an intricate social structure. Although these functions are deterministic, those determinants are legion, heavily interacting and dependent on a specific evolutionary trajectory. That trajectory was directed by the adaptive significance of quasi-random genetic variations, but was also influenced by chance and caprice. With a different evolutionary pathway, the same neural elements could subserve functions distinctly different from what they do in extant human brains. Consequently, the properties of higher level neural networks cannot be derived readily from the properties of the lower level constituent elements, without studying these elements in the aggregate. Thus, a multi-level approach to integrative neuroscience may offer an optimal strategy. Moreover, the process of calibrative reductionism, by which concepts and understandings from one level of organization or analysis can mutually inform and 'calibrate' those from other levels (both higher and lower), may represent a viable approach to the application of reductionism in science. This is especially relevant in social neuroscience, where the basic subject matter of interest is defined by interacting organisms across diverse environments. PMID:23386961

  11. A Multilevel Parallelization Framework for High-Order Stencil Computations

    NASA Astrophysics Data System (ADS)

    Dursun, Hikmet; Nomura, Ken-Ichi; Peng, Liu; Seymour, Richard; Wang, Weiqiang; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

    Stencil based computation on structured grids is a common kernel to broad scientific applications. The order of stencils increases with the required precision, and it is a challenge to optimize such high-order stencils on multicore architectures. Here, we propose a multilevel parallelization framework that combines: (1) inter-node parallelism by spatial decomposition; (2) intra-chip parallelism through multithreading; and (3) data-level parallelism via single-instruction multiple-data (SIMD) techniques. The framework is applied to a 6 th order stencil based seismic wave propagation code on a suite of multicore architectures. Strong-scaling scalability tests exhibit superlinear speedup due to increasing cache capacity on Intel Harpertown and AMD Barcelona based clusters, whereas weak-scaling parallel efficiency is 0.92 on 65,536 BlueGene/P processors. Multithreading+SIMD optimizations achieve 7.85-fold speedup on a dual quad-core Intel Clovertown, and the data-level parallel efficiency is found to depend on the stencil order.

  12. Multilevel evaluations of potential liver injury of bifenthrin.

    PubMed

    Zhang, Ying; Lu, Meiya; Zhou, Peixue; Wang, Cui; Zhang, Quan; Zhao, Meirong

    2015-07-01

    The widespread use of pesticides, such as pyrethroids, increases health risks to non-target organisms. The potential toxicity of pyrethroids to the liver remains unclear and could be easily overlooked if only the common clinical indicators of liver disease are examined. In the present study, BALB/c mice were given intraperitoneal injections of 0, 2, 4, or 8 mg/kg bifenthrin (BF) for 7 days. The potential liver injury of BF and its underlying mechanism were then investigated through multilevel evaluations. Histological analyses and serum enzyme activities showed no obvious clinical evidence of liver damage. Oxidative stress was induced and caspases were activated in response to increased BF concentrations. Exposure to BF also significantly altered the expression levels of mitochondrial apoptosis-related genes in dose-dependent relationships. The microarray results showed that BF could disturb the metabolic profile and extensively induce genes related to oxidative stress, including the cytochrome P450 family, glutathione peroxidases, glutathione s-transferases and kinases. In the in vivo model, BF induced liver injury through caspase-mediated mitochondrial-dependent cell death, a process that is closely related to oxidative stress, even in the absence of classical clinical biomarkers of liver dysfunction. The results of this study suggest that classical evaluations are not adequate for liver toxicity of pyrethroids, and highlight the need for more comprehensive assessment of health risks of these widely used pesticides. PMID:26071804

  13. Multilevel selection in a resource-based model

    NASA Astrophysics Data System (ADS)

    Ferreira, Fernando Fagundes; Campos, Paulo R. A.

    2013-07-01

    In the present work we investigate the emergence of cooperation in a multilevel selection model that assumes limiting resources. Following the work by R. J. Requejo and J. Camacho [Phys. Rev. Lett.0031-900710.1103/PhysRevLett.108.038701 108, 038701 (2012)], the interaction among individuals is initially ruled by a prisoner's dilemma (PD) game. The payoff matrix may change, influenced by the resource availability, and hence may also evolve to a non-PD game. Furthermore, one assumes that the population is divided into groups, whose local dynamics is driven by the payoff matrix, whereas an intergroup competition results from the nonuniformity of the growth rate of groups. We study the probability that a single cooperator can invade and establish in a population initially dominated by defectors. Cooperation is strongly favored when group sizes are small. We observe the existence of a critical group size beyond which cooperation becomes counterselected. Although the critical size depends on the parameters of the model, it is seen that a saturation value for the critical group size is achieved. The results conform to the thought that the evolutionary history of life repeatedly involved transitions from smaller selective units to larger selective units.

  14. Multilevel depth and image fusion for human activity detection.

    PubMed

    Ni, Bingbing; Pei, Yong; Moulin, Pierre; Yan, Shuicheng

    2013-10-01

    Recognizing complex human activities usually requires the detection and modeling of individual visual features and the interactions between them. Current methods only rely on the visual features extracted from 2-D images, and therefore often lead to unreliable salient visual feature detection and inaccurate modeling of the interaction context between individual features. In this paper, we show that these problems can be addressed by combining data from a conventional camera and a depth sensor (e.g., Microsoft Kinect). We propose a novel complex activity recognition and localization framework that effectively fuses information from both grayscale and depth image channels at multiple levels of the video processing pipeline. In the individual visual feature detection level, depth-based filters are applied to the detected human/object rectangles to remove false detections. In the next level of interaction modeling, 3-D spatial and temporal contexts among human subjects or objects are extracted by integrating information from both grayscale and depth images. Depth information is also utilized to distinguish different types of indoor scenes. Finally, a latent structural model is developed to integrate the information from multiple levels of video processing for an activity detection. Extensive experiments on two activity recognition benchmarks (one with depth information) and a challenging grayscale + depth human activity database that contains complex interactions between human-human, human-object, and human-surroundings demonstrate the effectiveness of the proposed multilevel grayscale + depth fusion scheme. Higher recognition and localization accuracies are obtained relative to the previous methods. PMID:23996589

  15. Bootstrap confidence intervals in multi-level simultaneous component analysis.

    PubMed

    Timmerman, Marieke E; Kiers, Henk A L; Smilde, Age K; Ceulemans, Eva; Stouten, Jeroen

    2009-05-01

    Multi-level simultaneous component analysis (MLSCA) was designed for the exploratory analysis of hierarchically ordered data. MLSCA specifies a component model for each level in the data, where appropriate constraints express possible similarities between groups of objects at a certain level, yielding four MLSCA variants. The present paper discusses different bootstrap strategies for estimating confidence intervals (CIs) on the individual parameters. In selecting a proper strategy, the main issues to address are the resampling scheme and the non-uniqueness of the parameters. The resampling scheme depends on which level(s) in the hierarchy are considered random, and which fixed. The degree of non-uniqueness depends on the MLSCA variant, and, in two variants, the extent to which the user exploits the transformational freedom. A comparative simulation study examines the quality of bootstrap CIs of different MLSCA parameters. Generally, the quality of bootstrap CIs appears to be good, provided the sample sizes are sufficient at each level that is considered to be random. The latter implies that if more than a single level is considered random, the total number of observations necessary to obtain reliable inferential information increases dramatically. An empirical example illustrates the use of bootstrap CIs in MLSCA. PMID:18086338

  16. Flight loads and control

    NASA Technical Reports Server (NTRS)

    Mowery, D. K.; Winder, S. W.

    1972-01-01

    The prediction of flight loads and their potential reduction, using various control logics for the space shuttle vehicles, is very complex. Some factors, not found on previous launch vehicles, that increase the complexity are large lifting surfaces, unsymmetrical structure, unsymmetrical aerodynamics, trajectory control system coupling, and large aeroelastic effects. Discussed are these load producing factors and load reducing techniques. Identification of potential technology areas is included.

  17. Load regulating expansion fixture

    DOEpatents

    Wagner, Lawrence M.; Strum, Michael J.

    1998-01-01

    A free standing self contained device for bonding ultra thin metallic films, such as 0.001 inch beryllium foils. The device will regulate to a predetermined load for solid state bonding when heated to a bonding temperature. The device includes a load regulating feature, whereby the expansion stresses generated for bonding are regulated and self adjusting. The load regulator comprises a pair of friction isolators with a plurality of annealed copper members located therebetween. The device, with the load regulator, will adjust to and maintain a stress level needed to successfully and economically complete a leak tight bond without damaging thin foils or other delicate components.

  18. Load regulating expansion fixture

    DOEpatents

    Wagner, L.M.; Strum, M.J.

    1998-12-15

    A free standing self contained device for bonding ultra thin metallic films, such as 0.001 inch beryllium foils is disclosed. The device will regulate to a predetermined load for solid state bonding when heated to a bonding temperature. The device includes a load regulating feature, whereby the expansion stresses generated for bonding are regulated and self adjusting. The load regulator comprises a pair of friction isolators with a plurality of annealed copper members located therebetween. The device, with the load regulator, will adjust to and maintain a stress level needed to successfully and economically complete a leak tight bond without damaging thin foils or other delicate components. 1 fig.

  19. Load sensing system

    DOEpatents

    Sohns, C.W.; Nodine, R.N.; Wallace, S.A.

    1999-05-04

    A load sensing system inexpensively monitors the weight and temperature of stored nuclear material for long periods of time in widely variable environments. The system can include an electrostatic load cell that encodes weight and temperature into a digital signal which is sent to a remote monitor via a coaxial cable. The same cable is used to supply the load cell with power. When multiple load cells are used, vast inventories of stored nuclear material can be continuously monitored and inventoried of minimal cost. 4 figs.

  20. Is there a “school effect” on pupil outcomes? A review of multilevel studies

    PubMed Central

    Sellström, E; Bremberg, S

    2006-01-01

    Study objective The school environment is of importance for child outcomes. Multilevel analyses can separate determinants operating at an individual level from those operating at a contextual level. This paper aims to systematically review multilevel studies of school contextual effects on pupil outcomes. Design Key word searching of five databases yielded 17 cross sectional or longitudinal studies meeting the inclusion criteria. Results are summarised with reference to type of school contextual determinant. Main results Four main school effects on pupil outcomes were identified. Having a health policy or antismoking policy, a good school climate, high average socioeconomic status, and urban location had a positive effect on pupil outcomes. Outcomes under study were smoking habits, wellbeing, problem behaviour, and school achievement. Conclusions Despite the different pupil outcomes and the variety of determinants used in the included papers, a school effect was evident. However, to improve our understanding of school effects, presentations of results from multilevel studies need to be standardised. Intraclass correlation and explained between school variance give relevant information on factors in the school environment influencing pupil outcomes, and should be included in all multilevel studies. Inclusion of pupil level predictors in the multilevel models should be based on theoretical considerations of how schools and communities are interconnected and how pupils and their families are influenced by school contextual factors. PMID:16415266

  1. Microbial load monitor

    NASA Technical Reports Server (NTRS)

    Caplin, R. S.; Royer, E. R.

    1977-01-01

    Design analysis of a microbial load monitor system flight engineering model was presented. Checkout of the card taper and media pump system was fabricated as well as the final two incubating reading heads, the sample receiving and card loading device assembly, related sterility testing, and software. Progress in these areas was summarized.

  2. Combined Load Test Fixture

    NASA Technical Reports Server (NTRS)

    Baker, Donald J.

    2010-01-01

    A test fixture has been developed at NASA Langley Research Center that has the capability of applying compression load and shear load simultaneously to a test specimen. The test specimen size is 24-inches by 28-inches. This report describes the test specimen design, test specimen preparation, fixture assembly in the test machine, and a test operation plan.

  3. Strip and load data

    NASA Technical Reports Server (NTRS)

    Jones, R. H.

    1984-01-01

    The method of taking batch data files and loading these files into the ADABAS data base management system (DBMS) is examined. This strip and load process allows the user to quickly become productive. Techniques for data fields and files definition are also included.

  4. Electronic Load Bank

    NASA Technical Reports Server (NTRS)

    Huston, Steven W.

    1992-01-01

    Electronic load-bank circuit provides pulsed or continuous low-resistance load to imitate effect of short circuit on Ni/H2 or other electrochemical power cells. Includes safety/warning feature and taps for measurement of cell-output voltage and current.

  5. Water impact loads

    NASA Technical Reports Server (NTRS)

    Sanders, D. H.; Safronski, S. G.

    1972-01-01

    Computer program to generate time history of load factor and pressure on conical body of revolution during impact with water is discussed. Program calculates depth of penetration, velocity, force, load factor, maximum pressure at water line, and average pressure. Program is written in FORTRAN 4 Level H for IBM 360/85/195 Release 20.1 computer.

  6. CRITICAL LOADS METHODS

    EPA Science Inventory

    I summarize the results of an interagency project that 1) defines a generic approach to quantifying and reporting critical loads, and 2) exercises that generic approach by examining a data rich system -- the critical loads of sulfur deposition and it's effect on the chronic acidi...

  7. Lightening the Load

    PubMed Central

    Remington, Anna M.; Swettenham, John G.; Lavie, Nilli

    2012-01-01

    Autism spectrum disorder (ASD) research portrays a mixed picture of attentional abilities with demonstrations of enhancements (e.g., superior visual search) and deficits (e.g., higher distractibility). Here we test a potential resolution derived from the Load Theory of Attention (e.g., Lavie, 2005). In Load Theory, distractor processing depends on the perceptual load of the task and as such can only be eliminated under high load that engages full capacity. We hypothesize that ASD involves enhanced perceptual capacity, leading to the superior performance and increased distractor processing previously reported. Using a signal-detection paradigm, we test this directly and demonstrate that, under higher levels of load, perceptual sensitivity was reduced in typical adults but not in adults with ASD. These findings confirm our hypothesis and offer a promising solution to the previous discrepancies by suggesting that increased distractor processing in ASD results not from a filtering deficit but from enhanced perceptual capacity. PMID:22428792

  8. Multi-level systems modeling and optimization for novel aircraft

    NASA Astrophysics Data System (ADS)

    Subramanian, Shreyas Vathul

    This research combines the disciplines of system-of-systems (SoS) modeling, platform-based design, optimization and evolving design spaces to achieve a novel capability for designing solutions to key aeronautical mission challenges. A central innovation in this approach is the confluence of multi-level modeling (from sub-systems to the aircraft system to aeronautical system-of-systems) in a way that coordinates the appropriate problem formulations at each level and enables parametric search in design libraries for solutions that satisfy level-specific objectives. The work here addresses the topic of SoS optimization and discusses problem formulation, solution strategy, the need for new algorithms that address special features of this problem type, and also demonstrates these concepts using two example application problems - a surveillance UAV swarm problem, and the design of noise optimal aircraft and approach procedures. This topic is critical since most new capabilities in aeronautics will be provided not just by a single air vehicle, but by aeronautical Systems of Systems (SoS). At the same time, many new aircraft concepts are pressing the boundaries of cyber-physical complexity through the myriad of dynamic and adaptive sub-systems that are rising up the TRL (Technology Readiness Level) scale. This compositional approach is envisioned to be active at three levels: validated sub-systems are integrated to form conceptual aircraft, which are further connected with others to perform a challenging mission capability at the SoS level. While these multiple levels represent layers of physical abstraction, each discipline is associated with tools of varying fidelity forming strata of 'analysis abstraction'. Further, the design (composition) will be guided by a suitable hierarchical complexity metric formulated for the management of complexity in both the problem (as part of the generative procedure and selection of fidelity level) and the product (i.e., is the mission

  9. Are BMI and Sedentariness Correlated? A Multilevel Study in Children.

    PubMed

    Gomes, Thayse Natacha; Katzmarzyk, Peter T; dos Santos, Fernanda Karina; de Chaves, Raquel Nichele; Santos, Daniel; Pereira, Sara; Champagne, Catherine M; Hedeker, Donald; Maia, José

    2015-07-01

    The purpose of this research was to investigate the relationship between body mass index (BMI) and sedentariness (Sed) in children and to examine the influence of child and school correlates on their variation. The sample comprises 580 children (337 girls, 9-11 years). Sedentariness was assessed with an accelerometer, and BMI was computed. Child- and school-level covariates were analyzed using multilevel models. No significant correlation between Sed and BMI was found. School context explains 5% and 1.5% of the total variance in Sed and BMI, respectively. At the child level, only moderate-to-vigorous physical activity was associated with both Sed (β = -0.02 ± 0.002) and BMI (β = -0.005 ± 0.002). Sleep time is related to Sed (β = -0.42 ± 0.04), while sex (β = 1.97 ± 0.13), biological maturity (β = 1.25 ± 0.07), media in the bedroom (β = 0.26 ± 0.08) and healthy (β = -0.09 ± 0.03) and unhealthy (β = -0.07 ± 0.04) diet scores were associated with BMI. None of the school-level covariates were related to BMI, but access to cafeteria (β = -0.97 ± 0.25), playground equipment (β = -0.67 ± 0.20) and restaurants (β = 0.16 ± 0.08) were related to Sed. In conclusion, Sed and BMI were not correlated. Further, they have different correlates, while children's traits seem to play more relevant roles in their differences in Sed and BMI than the school milieu. This information should be taken into account when strategies to reduce Sed and BMI are implemented. PMID:26193311

  10. Longitudinal Multilevel Modeling of Facial Pain, Muscle Tension, and Stress.

    PubMed

    Glaros, A G; Marszalek, J M; Williams, K B

    2016-04-01

    The role of masticatory muscle activation on pain in temporomandibular muscle and joint disorders (TMJD) is controversial. This single-group, prospective panel study examined the relationships among masticatory muscle tension, emotional distress, and TMJD pain in a sample of 7,023 observations obtained from 171 individuals using longitudinal multilevel modeling. Three main hypotheses were tested. The first posited that emotional distress and muscle tension directly influenced pain (hypothesis 1a: Distress → TMJD Pain; hypothesis 1b: Muscle Tension → TMJD Pain). The second posited that emotional distress directly influenced muscle tension (Distress → Muscle Tension), and the third posited that the effect of emotional distress on pain was mediated by muscle tension (Distress → Muscle Tension → TMJD pain). We also examined the fit of the data to possible alternative models. All the data used in this study were collected via an experience sampling methodology. The fit of the preferred models was better than that of the alternative models, with the preferred models explaining large proportions of the data, especially for level 2 variance (hypothesis 1a = 41% variance; hypothesis 1b = 69% variance; hypothesis 2 = 48% variance). In the mediation model, the addition of muscle tension to the model reduced the impact of emotional distress. The findings support a causal role for masticatory muscle tension in TMJD pain. Clinically, the results suggest that addressing tension and other oral parafunctions in those diagnosed with TMJDs should be an important part of the conservative, noninvasive care of individuals diagnosed with the myofascial pain or arthralgia of TMJD. PMID:26758381

  11. Statistical behaviour of adaptive multilevel splitting algorithms in simple models

    SciTech Connect

    Rolland, Joran Simonnet, Eric

    2015-02-15

    Adaptive multilevel splitting algorithms have been introduced rather recently for estimating tail distributions in a fast and efficient way. In particular, they can be used for computing the so-called reactive trajectories corresponding to direct transitions from one metastable state to another. The algorithm is based on successive selection–mutation steps performed on the system in a controlled way. It has two intrinsic parameters, the number of particles/trajectories and the reaction coordinate used for discriminating good or bad trajectories. We investigate first the convergence in law of the algorithm as a function of the timestep for several simple stochastic models. Second, we consider the average duration of reactive trajectories for which no theoretical predictions exist. The most important aspect of this work concerns some systems with two degrees of freedom. They are studied in detail as a function of the reaction coordinate in the asymptotic regime where the number of trajectories goes to infinity. We show that during phase transitions, the statistics of the algorithm deviate significatively from known theoretical results when using non-optimal reaction coordinates. In this case, the variance of the algorithm is peaking at the transition and the convergence of the algorithm can be much slower than the usual expected central limit behaviour. The duration of trajectories is affected as well. Moreover, reactive trajectories do not correspond to the most probable ones. Such behaviour disappears when using the optimal reaction coordinate called committor as predicted by the theory. We finally investigate a three-state Markov chain which reproduces this phenomenon and show logarithmic convergence of the trajectory durations.

  12. Multilevel samplers as microcosms to assess microbial response to biostimulation.

    PubMed

    Baldwin, B R; Peacock, A D; Park, M; Ogles, D M; Istok, J D; McKinley, J P; Resch, C T; White, D C

    2008-01-01

    Passive multilevel samplers (MLS) containing a solid matrix for microbial colonization were used as in situ microcosms in conjunction with a push-pull biostimulation experiment designed to promote biological U(VI) and Tc(VII) reduction. MLS were deployed at 24 elevations in the injection well and two downgradient wells to investigate the spatial variability in microbial community composition and growth prior to and following biostimulation. The microbial community was characterized by real-time quantitative polymerase chain reaction (Q-PCR) quantification of bacteria, NO(3)(-)-reducing bacteria (nirS and nirK), delta-proteobacteria, Geobacter sp., and methanogens (mcrA). Pretest cell densities were low overall but varied substantially with significantly greater bacterial populations detected at circumneutral pH (t-test, alpha= 0.05), suggesting carbon substrate and low pH limitations of microbial activity. Although pretest cell densities were low, denitrifying bacteria were dominant members of the microbial community. Biostimulation with an ethanol-amended ground water resulted in concurrent NO(3)(-) and Tc(VII) reduction, followed by U(VI) reduction. Q-PCR analysis of MLS revealed significant (1 to 2 orders of magnitude, Mann-Whitney U-test, alpha= 0.05) increases in cell densities of bacteria, denitrifiers, delta-proteobacteria, Geobacter sp., and methanogens in response to biostimulation. Traditionally, characterization of sediment samples has been used to investigate the microbial community response to biostimulation; however, collection of sediment samples is expensive and not conducive to deep aquifers or temporal studies. The results presented demonstrate that push-pull tests with passive MLS provide an inexpensive approach to determine the effect of biostimulation on contaminant concentrations, geochemical conditions, and the microbial community composition and function. PMID:18194316

  13. Are BMI and Sedentariness Correlated? A Multilevel Study in Children

    PubMed Central

    Gomes, Thayse Natacha; Katzmarzyk, Peter T.; dos Santos, Fernanda Karina; de Chaves, Raquel Nichele; Santos, Daniel; Pereira, Sara; Champagne, Catherine M.; Hedeker, Donald; Maia, José

    2015-01-01

    The purpose of this research was to investigate the relationship between body mass index (BMI) and sedentariness (Sed) in children and to examine the influence of child and school correlates on their variation. The sample comprises 580 children (337 girls, 9–11 years). Sedentariness was assessed with an accelerometer, and BMI was computed. Child- and school-level covariates were analyzed using multilevel models. No significant correlation between Sed and BMI was found. School context explains 5% and 1.5% of the total variance in Sed and BMI, respectively. At the child level, only moderate-to-vigorous physical activity was associated with both Sed (β = −0.02 ± 0.002) and BMI (β = −0.005 ± 0.002). Sleep time is related to Sed (β = −0.42 ± 0.04), while sex (β = 1.97 ± 0.13), biological maturity (β = 1.25 ± 0.07), media in the bedroom (β = 0.26 ± 0.08) and healthy (β = −0.09 ± 0.03) and unhealthy (β = −0.07 ± 0.04) diet scores were associated with BMI. None of the school-level covariates were related to BMI, but access to cafeteria (β = −0.97 ± 0.25), playground equipment (β = −0.67 ± 0.20) and restaurants (β = 0.16 ± 0.08) were related to Sed. In conclusion, Sed and BMI were not correlated. Further, they have different correlates, while children’s traits seem to play more relevant roles in their differences in Sed and BMI than the school milieu. This information should be taken into account when strategies to reduce Sed and BMI are implemented. PMID:26193311

  14. Multilevel Samplers to Assess Microbial Community Response to Biostimulation

    NASA Astrophysics Data System (ADS)

    Baldwin, B. R.; McKinley, J. P.; Peacock, A. D.; Park, M.; Ogles, D.; Istok, J. D.; Resch, C. T.; White, D. C.

    2006-05-01

    Passive multilevel samplers (MLS) containing a solid matrix for microbial colonization were used in conjunction with a push-pull biostimulation experiment designed to promote biological U(VI) and Tc(VII) reduction. MLS were deployed at 24 elevations in the injection well and two down gradient wells to investigate the spatial variability in microbial community composition and growth prior to and following biostimulation. The microbial community was characterized by real-time PCR (Q-PCR) quantification of eubacteria, NO3- reducing bacteria (nirS and nirK), δ-proteobacteria, Geobacter sp., and methanogens (mcrA). Pretest cell densities were low overall but varied substantially with significantly greater eubacterial populations detected at circumneutral pH (T-test, α=0.05) suggesting carbon substrate and low pH limitation of microbial activity. Although pretest cell densities were low, denitrifying bacteria were dominant members of the microbial community. Biostimulation with an ethanol amended groundwater resulted in concurrent NO3- and Tc(VII) reduction followed by U(VI) reduction. Q-PCR analysis of MLS revealed significant (1-2 orders of magnitude, T-test, α=0.05) increases in cell densities of eubacteria, denitrifiers, δ- proteobacteria, Geobacter sp., and methanogens in response to biostimulation. Traditionally characterization of sediment samples has been used to investigate the microbial community response to biostimulation, however, collection of sediment samples is expensive and not conducive to deep aquifers or temporal studies. The results presented demonstrate that push-pull tests with passive MLS provide an inexpensive approach to determine the effect of biostimulation on contaminant concentrations, geochemical conditions, and the microbial community composition and function.

  15. Specific Heat Anomalies in Solids Described by a Multilevel Model

    NASA Astrophysics Data System (ADS)

    Souza, Mariano de; Paupitz, Ricardo; Seridonio, Antonio; Lagos, Roberto E.

    2016-04-01

    In the field of condensed matter physics, specific heat measurements can be considered as a pivotal experimental technique for characterizing the fundamental excitations involved in a certain phase transition. Indeed, phase transitions involving spin (de Souza et al. Phys. B Condens. Matter 404, 494 (2009) and Manna et al. Phys. Rev. Lett. 104, 016403 (2010)), charge (Pregelj et al. Phys. Rev. B 82, 144438 (2010)), lattice (Jesche et al. Phys. Rev. B 81, 134525 (2010)) (phonons) and orbital degrees of freedom, the interplay between ferromagnetism and superconductivity (Jesche et al. Phys. Rev. B 86, 020501 (2012)), Schottky-like anomalies in doped compounds (Lagos et al. Phys. C Supercond. 309, 170 (1998)), electronic levels in finite correlated systems (Macedo and Lagos J. Magn. Magn. Mater. 226, 105 (2001)), among other features, can be captured by means of high-resolution calorimetry. Furthermore, the entropy change associated with a first-order phase transition, no matter its nature, can be directly obtained upon integrating the specific heat over T, i.e., C( T)/ T, in the temperature range of interest. Here, we report on a detailed analysis of the two-peak specific heat anomalies observed in several materials. Employing a simple multilevel model, varying the spacing between the energy levels Δ i = ( E i - E 0) and the degeneracy of each energy level g i , we derive the required conditions for the appearance of such anomalies. Our findings indicate that a ratio of {Δ }2/{Δ }1thickapprox 10 between the energy levels and a high degeneracy of one of the energy levels define the two-peaks regime in the specific heat. Our approach accurately matches recent experimental results. Furthermore, using a mean-field approach, we calculate the specific heat of a degenerate Schottky-like system undergoing a ferromagnetic (FM) phase transition. Our results reveal that as the degeneracy is increased the Schottky maximum in the specific heat becomes narrow while the peak

  16. Identifying Multilevel Barriers to Tobacco Intervention in Postdoctoral Dental Education.

    PubMed

    Albert, David A; Bruzelius, Emilie; Ward, Angela; Gordon, Judith S

    2016-04-01

    The aims of this mixed-methods study were to assess tobacco treatment behaviors among residents and faculty in dental specialty postdoctoral programs and to explore factors in training and practice related to tobacco treatment education. Surveys and focus groups were conducted with a convenience sample of participants at three postdoctoral residency programs in New York City. Surveys assessed tobacco cessation training and behaviors. Focus groups explored barriers to implementing tobacco cessation treatment in educational settings. Data were collected between May and December 2013. Among the 160 faculty and residents identified as potentially eligible for the study, 60 were invited by program directors to participate, and 50 subsequently completed the survey and participated in a focus group (response rate of 31.3%). Survey results indicated high levels of asking patients about tobacco use and advising patients to quit. In contrast, specific tobacco cessation assistance and follow-up care occurred less frequently. There were statistically significant differences in tobacco cessation intervention across the specialties surveyed, but not between residents and faculty. Focus group comments were grouped into three broad areas: clinician factors, organizational support, and structural and contextual factors. Focus group results indicated that participants experienced significant organizational and structural barriers to learning about and providing tobacco treatment. Participants from each specialty indicated that multi-level barriers impeded their provision of evidence-based tobacco cessation interventions in postdoctoral educational settings. They suggested that didactic education should be reinforced by organizational- and systems-level changes to facilitate comprehensive tobacco education and effective cessation treatment in future dental practice. PMID:27037448

  17. Laminoplasty versus laminectomy and fusion for multilevel cervical compressive myelopathy

    PubMed Central

    Liu, Feng-Yu; Yang, Si-Dong; Huo, Li-Shuang; Wang, Tao; Yang, Da-Long; Ding, Wen-Yuan

    2016-01-01

    Abstract This is a meta-analysis to compare the results between laminoplasty and laminectomy followed by fusion for the patients with multilevel cervical compressive myelopathy. An extensive search of literature was performed in MEDLINE, Embase, the Cochrane library, CNKI, and WANFANG. The following outcome measures were extracted: the Japanese Orthopaedic Association (JOA) scores, cervical curvature index (CCI), visual analog scale (VAS), cervical lordosis (C2–7), complications, blood loss, and operation time. Data analysis was conducted with RevMan 5.3 and STATA 12.0. A total of 23 studies comprising 774 and 743 patients treated with laminoplasty and laminectomy followed by fusion, respectively, were included in the final analysis. The pooled analysis showed that there was no significant difference in preoperative JOA scores [P = 0.89], postoperative JOA scores [P = 0.13], JOA scores improvement rate [P = 0.27], preoperative CCI [P = 0.15], postoperative CCI [P = 0.14], preoperative VAS [P = 0.41], postoperative VAS [P = 0.52], preoperative cervical lordosis (C2–7) [P = 0.46], postoperative cervical lordosis (C2–7) [P = 0.67], total complications [P = 0.07], axial pain [P = 0.94], and blood loss [P = 0.51]. However, there were significant difference in operation time (WMD = −19.57 [−32.11, −7.02], P = 0.002) and C5 palsy (OR = 0.26 [0.15, 0.44], P < 0.001). As compared with laminectomy followed by fusion, expansive laminoplasty showed no significant differences in JOA scores, CCI, ROM, VAS, cervical lordosis (C2–7), axial pain, total complications, and blood loss, but shorter operation time and fewer C5 palsy. PMID:27281067

  18. Multilevel Analysis of Air Pollution and Early Childhood Neurobehavioral Development

    PubMed Central

    Lin, Ching-Chun; Yang, Shih-Kuan; Lin, Kuan-Chia; Ho, Wen-Chao; Hsieh, Wu-Shiun; Shu, Bih-Ching; Chen, Pau-Chung

    2014-01-01

    To investigate the association between the ambient air pollution levels during the prenatal and postnatal stages and early childhood neurobehavioral development, our study recruited 533 mother-infant pairs from 11 towns in Taiwan. All study subjects were asked to complete childhood neurobehavioral development scales and questionnaires at 6 and 18 months. Air pollution, including particulate matter ≤10 μm (PM10), carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), and hydrocarbons, was measured at air quality monitoring stations in the towns where the subjects lived. Multilevel analyses were applied to assess the association between air pollution and childhood neurobehavioral development during pregnancy and when the children were 0 to 6 months, 7 to 12 months, and 13 to 18 months old. At 18 months, poor subclinical neurodevelopment in early childhood is associated with the average SO2 exposure of prenatal, during all trimesters of pregnancy and at postnatal ages up to 12 months (first trimester β = −0.083, se = 0.030; second and third trimester β = −0.114, se = 0.045; from birth to 12 months of age β = −0.091, se = 0.034). Furthermore, adverse gross motor below average scores at six months of age were associated with increased average non-methane hydrocarbon, (NMHC) levels during the second and third trimesters (β = −8.742, se = 3.512). Low-level SO2 exposure prenatally and up to twelve months postnatal could cause adverse neurobehavioral effects at 18 months of age. Maternal NMHC exposure during the 2nd and 3rd trimesters of pregnancy would be also associated with poor gross motor development in their children at 6 months of age. PMID:24992486

  19. Improving overlay control through proper use of multilevel query APC

    NASA Astrophysics Data System (ADS)

    Conway, Timothy H.; Carlson, Alan; Crow, David A.

    2003-06-01

    Many state-of-the-art fabs are operating with increasingly diversified product mixes. For example, at Cypress Semiconductor, it is not unusual to be concurrently running multiple technologies and many devices within each technology. This diverse product mix significantly increases the difficulty of manually controlling overlay process corrections. As a result, automated run-to-run feedforward-feedback control has become a necessary and vital component of manufacturing. However, traditional run-to-run controllers rely on highly correlated historical events to forecast process corrections. For example, the historical process events typically are constrained to match the current event for exposure tool, device, process level and reticle ID. This narrowly defined process stream can result in insufficient data when applied to lowvolume or new-release devices. The run-to-run controller implemented at Cypress utilizes a multi-level query (Level-N) correlation algorithm, where each subsequent level widens the search criteria for available historical data. The paper discusses how best to widen the search criteria and how to determine and apply a known bias to account for tool-to-tool and device-to-device differences. Specific applications include offloading lots from one tool to another when the first tool is down for preventive maintenance, utilizing related devices to determine a default feedback vector for new-release devices, and applying bias values to account for known reticle-to-reticle differences. In this study, we will show how historical data can be leveraged from related devices or tools to overcome the limitations of narrow process streams. In particular, this paper discusses how effectively handling narrow process streams allows Cypress to offload lots from a baseline tool to an alternate tool.

  20. Antibiotic resistance shaping multi-level population biology of bacteria

    PubMed Central

    Baquero, Fernando; Tedim, Ana P.; Coque, Teresa M.

    2013-01-01

    Antibiotics have natural functions, mostly involving cell-to-cell signaling networks. The anthropogenic production of antibiotics, and its release in the microbiosphere results in a disturbance of these networks, antibiotic resistance tending to preserve its integrity. The cost of such adaptation is the emergence and dissemination of antibiotic resistance genes, and of all genetic and cellular vehicles in which these genes are located. Selection of the combinations of the different evolutionary units (genes, integrons, transposons, plasmids, cells, communities and microbiomes, hosts) is highly asymmetrical. Each unit of selection is a self-interested entity, exploiting the higher hierarchical unit for its own benefit, but in doing so the higher hierarchical unit might acquire critical traits for its spread because of the exploitation of the lower hierarchical unit. This interactive trade-off shapes the population biology of antibiotic resistance, a composed-complex array of the independent “population biologies.” Antibiotics modify the abundance and the interactive field of each of these units. Antibiotics increase the number and evolvability of “clinical” antibiotic resistance genes, but probably also many other genes with different primary functions but with a resistance phenotype present in the environmental resistome. Antibiotics influence the abundance, modularity, and spread of integrons, transposons, and plasmids, mostly acting on structures present before the antibiotic era. Antibiotics enrich particular bacterial lineages and clones and contribute to local clonalization processes. Antibiotics amplify particular genetic exchange communities sharing antibiotic resistance genes and platforms within microbiomes. In particular human or animal hosts, the microbiomic composition might facilitate the interactions between evolutionary units involved in antibiotic resistance. The understanding of antibiotic resistance implies expanding our knowledge on multi-level

  1. Multilevel selection and social evolution of insect societies

    NASA Astrophysics Data System (ADS)

    Korb, Judith; Heinze, Jürgen

    How sterile, altruistic worker castes have evolved in social insects and how they are maintained have long been central topics in evolutionary biology. With the advance of kin selection theory, insect societies, in particular those of haplodiploid bees, ants, and wasps, have become highly suitable model systems for investigating the details of social evolution and recently also how within-group conflicts are resolved. Because insect societies typically do not consist of clones, conflicts among nestmates arise, for example about the partitioning of reproduction and the allocation of resources towards male and female sexuals. Variation in relatedness among group members therefore appears to have a profound influence on the social structure of groups. However, insect societies appear to be remarkably robust against such variation: division of labor and task allocation are often organized in more or less the same way in societies with high as in those with very low nestmate relatedness. To explain the discrepancy between predictions from kin structure and empirical data, it was suggested that constraints-such as the lack of power or information-prevent individuals from pursuing their own selfish interests. Applying a multilevel selection approach shows that these constraints are in fact group-level adaptation preventing or resolving intracolonial conflict. The mechanisms of conflict resolution in insect societies are similar to those at other levels in the biological hierarchy (e.g., in the genome or multicellular organisms): alignment of interests, fair lottery, and social control. Insect societies can thus be regarded as a level of selection with novelties that provide benefits beyond the scope of a solitary life. Therefore, relatedness is less important for the maintenance of insect societies, although it played a fundamental role in their evolution.

  2. Multilevel analysis of air pollution and early childhood neurobehavioral development.

    PubMed

    Lin, Ching-Chun; Yang, Shih-Kuan; Lin, Kuan-Chia; Ho, Wen-Chao; Hsieh, Wu-Shiun; Shu, Bih-Ching; Chen, Pau-Chung

    2014-07-01

    To investigate the association between the ambient air pollution levels during the prenatal and postnatal stages and early childhood neurobehavioral development, our study recruited 533 mother-infant pairs from 11 towns in Taiwan. All study subjects were asked to complete childhood neurobehavioral development scales and questionnaires at 6 and 18 months. Air pollution, including particulate matter ≤10 μm (PM10), carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), and hydrocarbons, was measured at air quality monitoring stations in the towns where the subjects lived. Multilevel analyses were applied to assess the association between air pollution and childhood neurobehavioral development during pregnancy and when the children were 0 to 6 months, 7 to 12 months, and 13 to 18 months old. At 18 months, poor subclinical neurodevelopment in early childhood is associated with the average SO2 exposure of prenatal, during all trimesters of pregnancy and at postnatal ages up to 12 months (first trimester β = -0.083, se = 0.030; second and third trimester β = -0.114, se = 0.045; from birth to 12 months of age β = -0.091, se = 0.034). Furthermore, adverse gross motor below average scores at six months of age were associated with increased average non-methane hydrocarbon, (NMHC) levels during the second and third trimesters (β = -8.742, se = 3.512). Low-level SO2 exposure prenatally and up to twelve months postnatal could cause adverse neurobehavioral effects at 18 months of age. Maternal NMHC exposure during the 2nd and 3rd trimesters of pregnancy would be also associated with poor gross motor development in their children at 6 months of age. PMID:24992486

  3. Multilevel Parallelization of AutoDock 4.2

    PubMed Central

    2011-01-01

    Background Virtual (computational) screening is an increasingly important tool for drug discovery. AutoDock is a popular open-source application for performing molecular docking, the prediction of ligand-receptor interactions. AutoDock is a serial application, though several previous efforts have parallelized various aspects of the program. In this paper, we report on a multi-level parallelization of AutoDock 4.2 (mpAD4). Results Using MPI and OpenMP, AutoDock 4.2 was parallelized for use on MPI-enabled systems and to multithread the execution of individual docking jobs. In addition, code was implemented to reduce input/output (I/O) traffic by reusing grid maps at each node from docking to docking. Performance of mpAD4 was examined on two multiprocessor computers. Conclusions Using MPI with OpenMP multithreading, mpAD4 scales with near linearity on the multiprocessor systems tested. In situations where I/O is limiting, reuse of grid maps reduces both system I/O and overall screening time. Multithreading of AutoDock's Lamarkian Genetic Algorithm with OpenMP increases the speed of execution of individual docking jobs, and when combined with MPI parallelization can significantly reduce the execution time of virtual screens. This work is significant in that mpAD4 speeds the execution of certain molecular docking workloads and allows the user to optimize the degree of system-level (MPI) and node-level (OpenMP) parallelization to best fit both workloads and computational resources. PMID:21527034

  4. Contextual Risk Factors for Low Birth Weight: A Multilevel Analysis

    PubMed Central

    Kayode, Gbenga A.; Amoakoh-Coleman, Mary; Agyepong, Irene Akua; Ansah, Evelyn; Grobbee, Diederick E.; Klipstein-Grobusch, Kerstin

    2014-01-01

    Background Low birth weight (LBW) remains to be a leading cause of neonatal death and a major contributor to infant and under-five mortality. Its prevalence has not declined in the last decade in sub-Saharan Africa (SSA) and Asia. Some individual level factors have been identified as risk factors for LBW but knowledge is limited on contextual risk factors for LBW especially in SSA. Methods Contextual risk factors for LBW in Ghana were identified by performing multivariable multilevel logistic regression analysis of 6,900 mothers dwelling in 412 communities that participated in the 2003 and 2008 Demographic and Health Surveys in Ghana. Results Contextual-level factors were significantly associated with LBW: Being a rural dweller increased the likelihood of having a LBW infant by 43% (OR 1.43; 95% CI 1.01–2.01; P-value <0.05) while living in poverty-concentrated communities increased the risk of having a LBW infant twofold (OR 2.16; 95% CI 1.29–3.61; P-value <0.01). In neighbourhoods with a high coverage of safe water supply the odds of having a LBW infant reduced by 28% (OR 0.74; 95% CI 0.57–0.96; P-value <0.05). Conclusion This study showed contextual risk factors to have independent effects on the prevalence of LBW infants. Being a rural dweller, living in a community with a high concentration of poverty and a low coverage of safe water supply were found to increase the prevalence of LBW infants. Implementing appropriate community-based intervention programmes will likely reduce the occurrence of LBW infants. PMID:25360709

  5. Multi-level human evolution: ecological patterns in hominin phylogeny.

    PubMed

    Parravicini, Andrea; Pievani, Telmo

    2016-06-20

    Evolution is a process that occurs at many different levels, from genes to ecosystems. Genetic variations and ecological pressures are hence two sides of the same coin; but due both to fragmentary evidence and to the influence of a gene-centered and gradualistic approach to evolutionary phenomena, the field of paleoanthropology has been slow to take the role of macro-evolutionary patterns (i.e. ecological and biogeographical at large scale) seriously. However, several very recent findings in paleoanthropology stress both climate instability and ecological disturbance as key factors affecting the highly branching hominin phylogeny, from the earliest hominins to the appearance of cognitively modern humans. Allopatric speciation due to geographic displacement, turnover-pulses of species, adaptive radiation, mosaic evolution of traits in several coeval species, bursts of behavioral innovation, serial dispersals out of Africa, are just some of the macro-evolutionary patterns emerging from the field. The multilevel approach to evolution proposed by paleontologist Niles Eldredge is adopted here as interpretative tool, and has yielded a larger picture of human evolution that integrates different levels of evolutionary change, from local adaptations in limited ecological niches to dispersal phenotypes able to colonize an unprecedented range of ecosystems. Changes in global climate and Earth's surface most greatly affected human evolution. Precisely because it is cognitively hard for us to appreciate the long-term common destiny we share with the whole biosphere, it is particularly valuable to highlight the accumulating evidence that human evolution has been deeply affected by global ecological changes that transformed our African continent of origin. PMID:26829575

  6. Multilevel method for modeling large-scale networks.

    SciTech Connect

    Safro, I. M.

    2012-02-24

    researchers. We propose to develop multilevel methods to model complex networks. The key point of the proposed strategy is that it will help to preserve part of the unknown structural attributes by guaranteeing the similar behavior of the real and artificial model on different scales.

  7. Estimating Correlates of Growth between Mathematics and Science Achievement via a Multivariate Multilevel Design with Latent Variables

    ERIC Educational Resources Information Center

    Ma, Lingling; Ma, Xin

    2005-01-01

    The purpose of the present study was to improve a multivariate multilevel model in the research literature which estimates the consistency in the rates of growth between mathematics and science achievement among students and schools. We introduced a new multivariate multilevel model via a latent variable approach. Data from the Longitudinal Study…

  8. Multilevel Factor Analysis and Structural Equation Modeling of Daily Diary Coping Data: Modeling Trait and State Variation

    ERIC Educational Resources Information Center

    Roesch, Scott C.; Aldridge, Arianna A.; Stocking, Stephanie N.; Villodas, Feion; Leung, Queenie; Bartley, Carrie E.; Black, Lisa J.

    2010-01-01

    This study used multilevel modeling of daily diary data to model within-person (state) and between-person (trait) components of coping variables. This application included the introduction of multilevel factor analysis (MFA) and a comparison of the predictive ability of these trait/state factors. Daily diary data were collected on a large (n =…

  9. The Impact of Misspecifying the Within-Subject Covariance Structure in Multiwave Longitudinal Multilevel Models: A Monte Carlo Study

    ERIC Educational Resources Information Center

    Kwok, Oi-man; West, Stephen G.; Green, Samuel B.

    2007-01-01

    This Monte Carlo study examined the impact of misspecifying the [big sum] matrix in longitudinal data analysis under both the multilevel model and mixed model frameworks. Under the multilevel model approach, under-specification and general-misspecification of the [big sum] matrix usually resulted in overestimation of the variances of the random…

  10. Estimation of Contextual Effects through Nonlinear Multilevel Latent Variable Modeling with a Metropolis-Hastings Robbins-Monro Algorithm

    ERIC Educational Resources Information Center

    Yang, Ji Seung

    2012-01-01

    Nonlinear multilevel latent variable modeling has been suggested as an alternative to traditional hierarchical linear modeling to more properly handle measurement error and sampling error issues in contextual effects modeling. However, a nonlinear multilevel latent variable model requires significant computational effort because the estimation…

  11. The Mantel-Haenszel Method for Detecting Differential Item Functioning in Dichotomously Scored Items: A Multilevel Approach

    ERIC Educational Resources Information Center

    MacInnes, Jann Marie Wise

    2009-01-01

    Multilevel data often exist in educational studies. The focus of this study is to consider differential item functioning (DIF) for dichotomous items from a multilevel perspective. One of the most often used methods for detecting DIF in dichotomously scored items is the Mantel-Haenszel log odds-ratio. However, the Mantel-Haenszel reduces the…

  12. Income Inequality and Risk of Suicide in New York City Neighborhoods: A Multilevel Case-Control Study

    ERIC Educational Resources Information Center

    Miller, Jeffrey R.; Piper, Tinka Markham; Ahern, Jennifer; Tracy, Melissa; Tardiff, Kenneth J.; Vlahov, David; Galea, Sandro

    2005-01-01

    Evidence on the relationship between income inequality and suicide is inconsistent. Data from the New York City Office of the Chief Medical Examiner for all fatal injuries was collected to conduct a multilevel case-control study. In multilevel models, suicide decedents (n = 374) were more likely than accident controls (n = 453) to reside in…

  13. Multilevel Modeling and Policy Development: Guidelines and Applications to Medical Travel

    PubMed Central

    Garcia-Garzon, Eduardo; Zhukovsky, Peter; Haller, Elisa; Plakolm, Sara; Fink, David; Petrova, Dafina; Mahalingam, Vaishali; Menezes, Igor G.; Ruggeri, Kai

    2016-01-01

    Medical travel has expanded rapidly in recent years, resulting in new markets and increased access to medical care. Whereas several studies investigated the motives of individuals seeking healthcare abroad, the conventional analytical approach is limited by substantial caveats. Classical techniques as found in the literature cannot provide sufficient insight due to the nested nature of data generated. The application of adequate analytical techniques, specifically multilevel modeling, is scarce to non-existent in the context of medical travel. This study introduces the guidelines for application of multilevel techniques in public health research by presenting an application of multilevel modeling in analyzing the decision-making patterns of potential medical travelers. Benefits and potential limitations are discussed. PMID:27252672

  14. Simulations Of Nanomagnet Clusters With Perpendicular Uniaxial Anisotropy For Multilevel Data Storage

    NASA Astrophysics Data System (ADS)

    Xiao, Qijun; Krotkov, Robert; Tuominen, Mark

    2006-03-01

    Digital data storage technology generally relies on a binary storage paradigm. In this work we explore a different scheme that exploits the stepwise, multilevel total magnetization of a small cluster of interacting nanomagnets. The magnetization of a cluster can be resolved more easily than that of a single nanomagnet, due to the larger lateral size. Micromagnetic simulations, based on the Landau-Lifshitz-Gilbert (LLG) equation with parameters representative of Co3Pt, reveal that magnetostatic interactions within a cluster produce a rich multilevel magnetic response, each level providing a stable remanent magnetization state. This work describes simulations used to investigate a multilevel data storage unit based on a hexagonal cluster of interacting uniaxial single domain nanomagnets. The accessibility and stability of the discrete magnetization states are studied. The switching properties of the nanomagnet clusters can be tuned by modifying the geometry, providing the ability to engineer desirable magnetic properties.

  15. Modeling of trophospheric ozone concentrations using genetically trained multi-level cellular neural networks

    NASA Astrophysics Data System (ADS)

    Ozcan, H. Kurtulus; Bilgili, Erdem; Sahin, Ulku; Ucan, O. Nuri; Bayat, Cuma

    2007-09-01

    Tropospheric ozone concentrations, which are an important air pollutant, are modeled by the use of an artificial intelligence structure. Data obtained from air pollution measurement stations in the city of Istanbul are utilized in constituting the model. A supervised algorithm for the evaluation of ozone concentration using a genetically trained multi-level cellular neural network (ML-CNN) is introduced, developed, and applied to real data. A genetic algorithm is used in the optimization of CNN templates. The model results and the actual measurement results are compared and statistically evaluated. It is observed that seasonal changes in ozone concentrations are reflected effectively by the concentrations estimated by the multilevel-CNN model structure, with a correlation value of 0.57 ascertained between actual and model results. It is shown that the multilevel-CNN modeling technique is as satisfactory as other modeling techniques in associating the data in a complex medium in air pollution applications.

  16. Multilevel Modeling and Policy Development: Guidelines and Applications to Medical Travel.

    PubMed

    Garcia-Garzon, Eduardo; Zhukovsky, Peter; Haller, Elisa; Plakolm, Sara; Fink, David; Petrova, Dafina; Mahalingam, Vaishali; Menezes, Igor G; Ruggeri, Kai

    2016-01-01

    Medical travel has expanded rapidly in recent years, resulting in new markets and increased access to medical care. Whereas several studies investigated the motives of individuals seeking healthcare abroad, the conventional analytical approach is limited by substantial caveats. Classical techniques as found in the literature cannot provide sufficient insight due to the nested nature of data generated. The application of adequate analytical techniques, specifically multilevel modeling, is scarce to non-existent in the context of medical travel. This study introduces the guidelines for application of multilevel techniques in public health research by presenting an application of multilevel modeling in analyzing the decision-making patterns of potential medical travelers. Benefits and potential limitations are discussed. PMID:27252672

  17. Multilevel Weighted Support Vector Machine for Classification on Healthcare Data with Missing Values

    PubMed Central

    Razzaghi, Talayeh; Roderick, Oleg; Safro, Ilya; Marko, Nicholas

    2016-01-01

    This work is motivated by the needs of predictive analytics on healthcare data as represented by Electronic Medical Records. Such data is invariably problematic: noisy, with missing entries, with imbalance in classes of interests, leading to serious bias in predictive modeling. Since standard data mining methods often produce poor performance measures, we argue for development of specialized techniques of data-preprocessing and classification. In this paper, we propose a new method to simultaneously classify large datasets and reduce the effects of missing values. It is based on a multilevel framework of the cost-sensitive SVM and the expected maximization imputation method for missing values, which relies on iterated regression analyses. We compare classification results of multilevel SVM-based algorithms on public benchmark datasets with imbalanced classes and missing values as well as real data in health applications, and show that our multilevel SVM-based method produces fast, and more accurate and robust classification results. PMID:27195952

  18. A multilevel control system for the large space telescope. [numerical analysis/optimal control

    NASA Technical Reports Server (NTRS)

    Siljak, D. D.; Sundareshan, S. K.; Vukcevic, M. B.

    1975-01-01

    A multilevel scheme was proposed for control of Large Space Telescope (LST) modeled by a three-axis-six-order nonlinear equation. Local controllers were used on the subsystem level to stabilize motions corresponding to the three axes. Global controllers were applied to reduce (and sometimes nullify) the interactions among the subsystems. A multilevel optimization method was developed whereby local quadratic optimizations were performed on the subsystem level, and global control was again used to reduce (nullify) the effect of interactions. The multilevel stabilization and optimization methods are presented as general tools for design and then used in the design of the LST Control System. The methods are entirely computerized, so that they can accommodate higher order LST models with both conceptual and numerical advantages over standard straightforward design techniques.

  19. Analyzing average and conditional effects with multigroup multilevel structural equation models

    PubMed Central

    Mayer, Axel; Nagengast, Benjamin; Fletcher, John; Steyer, Rolf

    2014-01-01

    Conventionally, multilevel analysis of covariance (ML-ANCOVA) has been the recommended approach for analyzing treatment effects in quasi-experimental multilevel designs with treatment application at the cluster-level. In this paper, we introduce the generalized ML-ANCOVA with linear effect functions that identifies average and conditional treatment effects in the presence of treatment-covariate interactions. We show how the generalized ML-ANCOVA model can be estimated with multigroup multilevel structural equation models that offer considerable advantages compared to traditional ML-ANCOVA. The proposed model takes into account measurement error in the covariates, sampling error in contextual covariates, treatment-covariate interactions, and stochastic predictors. We illustrate the implementation of ML-ANCOVA with an example from educational effectiveness research where we estimate average and conditional effects of early transition to secondary schooling on reading comprehension. PMID:24795668

  20. An integrated technique for eliminating harmonics of multilevel inverter with unequal DC sources

    NASA Astrophysics Data System (ADS)

    Malarvizhi, M.; Gnanambal, I.

    2015-02-01

    For improving the alteration performance of multilevel inverter, selective harmonics elimination methods play a significant role. In this document, an incorporated method is suggested for removing the harmonics of multilevel inverter with uneven DC sources. The suggested incorporated method is the mixture of fuzzy logic intelligent system and particle swarm optimisation (PSO) algorithm. For generating the training information set in terms of switching angle, Fuzzy is one of the synthetic intelligent methods which apply harmonic voltage and harmonic distortion. PSO is one of the swarm intelligence-based optimisation algorithms which is employed for choosing optimal switching angle from the training data set. The suggested hybrid method is executed in MATLAB/Simulink platform. At dissimilar unequal input voltage levels, the performance of the suggested method is checked by cascade H-bridge multilevel inverter. The production of the suggested method is compared with the theoretical effects.

  1. A multilevel voltage-source inverter with separate dc sources for static var generation

    SciTech Connect

    Peng, Fang Zheng |; Lai, Jih-Sheng; McKeever, J.; VanCoevering, J.

    1995-09-01

    A new multilevel voltage-source inverter with a separate dc sources is proposed for high-voltage, high-power applications, such as flexible ac transmission systems (FACTS) including static var generation (SVG), power line conditioning, series compensation, phase shifting, voltage balancing, fuel cell and photovoltaic utility systems interfacing, etc. The new M-level inverter consists of (M-1)/2 single phase full bridges in which each bridge has its own separate dc source. This inverter can generate almost sinusoidal waveform voltage with only one time switching per cycle as the number of levels increases. It can solve the problems of conventional transformer-based multipulse inverters and the problems of the multilevel diode-clamped inverter and the multilevel flying capacitor inverter. To demonstrate the superiority of the new inverter, a SVG system using the new inverter topology is discussed through analysis, simulation and experiment.

  2. Enhanced multi-level block ILU preconditioning strategies for general sparse linear systems

    NASA Astrophysics Data System (ADS)

    Saad, Yousef; Zhang, Jun

    2001-05-01

    This paper introduces several strategies to deal with pivot blocks in multi-level block incomplete LU factorization (BILUM) preconditioning techniques. These techniques are aimed at increasing the robustness and controlling the amount of fill-ins of BILUM for solving large sparse linear systems when large-size blocks are used to form block-independent set. Techniques proposed in this paper include double-dropping strategies, approximate singular-value decomposition, variable size blocks and use of an arrowhead block submatrix. We point out the advantages and disadvantages of these strategies and discuss their efficient implementations. Numerical experiments are conducted to show the usefulness of the new techniques in dealing with hard-to-solve problems arising from computational fluid dynamics. In addition, we discuss the relation between multi-level ILU preconditioning methods and algebraic multi-level methods.

  3. Anterior decompression and fusion versus posterior laminoplasty for multilevel cervical compressive myelopathy.

    PubMed

    Liu, Xuzhou; Wang, Hehui; Zhou, Zhilai; Jin, Anmin

    2014-02-01

    The optimal surgical strategy for anterior or posterior approaches remains controversial for multilevel cervical compressive myelopathy caused by multisegment cervical spondylotic myelopathy (MCSM) or ossification of the posterior longitudinal ligament (OPLL). A systematic review and meta-analysis was conducted evaluating the clinical results of anterior decompression and fusion (ADF) compared with posterior laminoplasty for patients with multilevel cervical compressive myelopathy. PubMed, Embase, and the Cochrane Library were searched for randomized controlled trials and nonrandomized cohort studies conducted from 1990 to May 2013 comparing ADF with posterior laminoplasty for the treatment of multilevel cervical compressive myelopathy due to MCSM or OPLL. The following outcome measures were extracted: Japanese Orthopedic Association (JOA) score, recovery rate, complication rate, reoperation rate, blood loss, and operative time. Subgroup analysis was conducted according to the mean number of surgical segments. Eleven studies were included in the review, all of which were prospective or retrospective cohort studies with relatively low quality indicated by GRADE Working Group assessment. A definitive conclusion could not be reached regarding which surgical approach is more effective for the treatment of multilevel cervical compressive myelopathy. Although ADF was associated with better postoperative neural function than posterior laminoplasty in the treatment of multilevel cervical compressive myelopathy due to MCSM or OPLL, there was no apparent difference in the neural function recovery rate between the 2 approaches. Higher rates of surgery-related complication and reoperation should be taken into consideration when ADF is used for patients with multilevel cervical compressive myelopathy. The surgical trauma associated with corpectomy was significantly higher than that associated with posterior laminoplasty. PMID:24679196

  4. Statistical power of multilevel modelling in dental caries clinical trials: a simulation study.

    PubMed

    Burnside, G; Pine, C M; Williamson, P R

    2014-01-01

    Outcome data from dental caries clinical trials have a naturally hierarchical structure, with surfaces clustered within teeth, clustered within individuals. Data are often aggregated into the DMF index for each individual, losing tooth- and surface-specific information. If these data are to be analysed by tooth or surface, allowing exploration of effects of interventions on different teeth and surfaces, appropriate methods must be used to adjust for the clustered nature of the data. Multilevel modelling allows analysis of clustered data using individual observations without aggregating data, and has been little used in the field of dental caries. A simulation study was conducted to investigate the performance of multilevel modelling methods and standard caries increment analysis. Data sets were simulated from a three-level binomial distribution based on analysis of a caries clinical trial in Scottish adolescents, with varying sample sizes, treatment effects and random tooth level effects based on trials reported in Cochrane reviews of topical fluoride, and analysed to compare the power of multilevel models and traditional analysis. 40,500 data sets were simulated. Analysis showed that estimated power for the traditional caries increment method was similar to that for multilevel modelling, with more variation in smaller data sets. Multilevel modelling may not allow significant reductions in the number of participants required in a caries clinical trial, compared to the use of traditional analyses, but investigators interested in exploring the effect of their intervention in more detail may wish to consider the application of multilevel modelling to their clinical trial data. PMID:24216573

  5. Cable load sensing device

    DOEpatents

    Beus, Michael J.; McCoy, William G.

    1998-01-01

    Apparatus for sensing the magnitude of a load on a cable as the cable is employed to support the load includes a beam structure clamped to the cable so that a length of the cable lies along the beam structure. A spacer associated with the beam structure forces a slight curvature in a portion of the length of cable under a cable "no-load" condition so that the portion of the length of cable is spaced from the beam structure to define a cable curved portion. A strain gauge circuit including strain gauges is secured to the beam structure by welding. As the cable is employed to support a load the load causes the cable curved portion to exert a force normal to the cable through the spacer and on the beam structure to deform the beam structure as the cable curved portion attempts to straighten under the load. As this deformation takes place, the resistance of the strain gauges is set to a value proportional to the magnitude of the normal strain on the beam structure during such deformation. The magnitude of the normal strain is manipulated in a control device to generate a value equal to the magnitude or weight of the load supported by the cable.

  6. Load Balancing Scientific Applications

    SciTech Connect

    Pearce, Olga Tkachyshyn

    2014-12-01

    The largest supercomputers have millions of independent processors, and concurrency levels are rapidly increasing. For ideal efficiency, developers of the simulations that run on these machines must ensure that computational work is evenly balanced among processors. Assigning work evenly is challenging because many large modern parallel codes simulate behavior of physical systems that evolve over time, and their workloads change over time. Furthermore, the cost of imbalanced load increases with scale because most large-scale scientific simulations today use a Single Program Multiple Data (SPMD) parallel programming model, and an increasing number of processors will wait for the slowest one at the synchronization points. To address load imbalance, many large-scale parallel applications use dynamic load balance algorithms to redistribute work evenly. The research objective of this dissertation is to develop methods to decide when and how to load balance the application, and to balance it effectively and affordably. We measure and evaluate the computational load of the application, and develop strategies to decide when and how to correct the imbalance. Depending on the simulation, a fast, local load balance algorithm may be suitable, or a more sophisticated and expensive algorithm may be required. We developed a model for comparison of load balance algorithms for a specific state of the simulation that enables the selection of a balancing algorithm that will minimize overall runtime.

  7. Cable load sensing device

    SciTech Connect

    Beus, M.J.; McCoy, W.G.

    1996-12-31

    Apparatus for sensing the magnitude of a load on a cable as the cable is employed to support the load includes a beam structure clamped to the cable so that a length of the cable lies along the beam structure. A spacer associated with the beam structure forces a slight curvature in a portion of the length of cable under a cable no-load condition so that the portion of the length of cable is spaced from the beam structure to define a cable curved portion. A strain gauge circuit including strain gauges is secured to the beam structure by welding. As the cable is employed to support a load the load causes the cable curved portion to exert a force normal to the cable through the spacer and on the beam structure to deform the beam structure as the cable curved portion attempts to straighten under the load. As this deformation takes place, the resistance of the strain gauges is set to a value proportional to the magnitude of the normal strain on the beam structure during such deformation. The magnitude of the normal strain is manipulated in a control device to generate a value equal to the magnitude or weight of the load supported by the cable.

  8. Dynamic load simulator

    NASA Technical Reports Server (NTRS)

    Joncas, K. P.

    1972-01-01

    Concepts and techniques for identifying and simulating both the steady state and dynamic characteristics of electrical loads for use during integrated system test and evaluation are discussed. The investigations showed that it is feasible to design and develop interrogation and simulation equipment to perform the desired functions. During the evaluation, actual spacecraft loads were interrogated by stimulating the loads with their normal input voltage and measuring the resultant voltage and current time histories. Elements of the circuits were optimized by an iterative process of selecting element values and comparing the time-domain response of the model with those obtained from the real equipment during interrogation.

  9. Streamlined mean field variational Bayes for longitudinal and multilevel data analysis.

    PubMed

    Lee, Cathy Yuen Yi; Wand, Matt P

    2016-07-01

    Streamlined mean field variational Bayes algorithms for efficient fitting and inference in large models for longitudinal and multilevel data analysis are obtained. The number of operations is linear in the number of groups at each level, which represents a two orders of magnitude improvement over the naïve approach. Storage requirements are also lessened considerably. We treat models for the Gaussian and binary response situations. Our algorithms allow the fastest ever approximate Bayesian analyses of arbitrarily large longitudinal and multilevel datasets, with little degradation in accuracy compared with Markov chain Monte Carlo. The modularity of mean field variational Bayes allows relatively simple extension to more complicated scenarios. PMID:27214238

  10. Towards Multi-level Optimization: Space-Mapping and Manifold-Mapping

    SciTech Connect

    Echeverria, D; Tong, C

    2006-07-24

    In this report we study space-mapping and manifold-mapping, two multi-level optimization techniques that aim at accelerating expensive optimization procedures with the aid of simple auxiliary models. Manifold-mapping improves in accuracy the solution given by space-mapping. In this report, the two mentioned techniques are basically described and then applied in the solving of two minimization problems. Several coarse models are tried, both from a two and a three level perspective. The results with these simple tests confirm the speed-up expected for the multi-level approach.

  11. A multi-level solution algorithm for steady-state Markov chains

    NASA Technical Reports Server (NTRS)

    Horton, Graham; Leutenegger, Scott T.

    1993-01-01

    A new iterative algorithm, the multi-level algorithm, for the numerical solution of steady state Markov chains is presented. The method utilizes a set of recursively coarsened representations of the original system to achieve accelerated convergence. It is motivated by multigrid methods, which are widely used for fast solution of partial differential equations. Initial results of numerical experiments are reported, showing significant reductions in computation time, often an order of magnitude or more, relative to the Gauss-Seidel and optimal SOR algorithms for a variety of test problems. The multi-level method is compared and contrasted with the iterative aggregation-disaggregation algorithm of Takahashi.

  12. Multilevel solvers of first-order system least-squares for Stokes equations

    SciTech Connect

    Lai, Chen-Yao G.

    1996-12-31

    Recently, The use of first-order system least squares principle for the approximate solution of Stokes problems has been extensively studied by Cai, Manteuffel, and McCormick. In this paper, we study multilevel solvers of first-order system least-squares method for the generalized Stokes equations based on the velocity-vorticity-pressure formulation in three dimensions. The least-squares functionals is defined to be the sum of the L{sup 2}-norms of the residuals, which is weighted appropriately by the Reynolds number. We develop convergence analysis for additive and multiplicative multilevel methods applied to the resulting discrete equations.

  13. Multilevel radiative thermal memory realized by the hysteretic metal-insulator transition of vanadium dioxide

    NASA Astrophysics Data System (ADS)

    Ito, Kota; Nishikawa, Kazutaka; Iizuka, Hideo

    2016-02-01

    Thermal information processing is attracting much interest as an analog of electronic computing. We experimentally demonstrated a radiative thermal memory utilizing a phase change material. The hysteretic metal-insulator transition of vanadium dioxide (VO2) allows us to obtain a multilevel memory. We developed a Preisach model to explain the hysteretic radiative heat transfer between a VO2 film and a fused quartz substrate. The transient response of our memory predicted by the Preisach model agrees well with the measured response. Our multilevel thermal memory paves the way for thermal information processing as well as contactless thermal management.

  14. An analytical description of the atomic information entropy in a multi-level system

    NASA Astrophysics Data System (ADS)

    Obada, A.-S. F.; Abdel-Aty, Mahmoud

    2008-05-01

    We construct a complete representation of the atomic information entropy of an arbitrary multi-level system. Our approach is applicable to all scenarios in which the quantum state shared by a single particle and fields is known. As illustrations we apply our findings to a single four-level atom strongly coupled to a cavity field and driven by a coherent laser field. In this framework, we discuss connections with entanglement frustration and entropic forms. We conclude by showing how the atomic information entropy can be extended to examine entanglement in multi-level atomic systems.

  15. A multilevel approach to the design of dc-free line codes

    NASA Technical Reports Server (NTRS)

    Calderbank, A. R.; Herro, Mark A.; Telang, Vivek

    1989-01-01

    A multilevel approach to the design of dc-free line codes is presented. The different levels can be used for different purposes; for example, to control the maximum accumulated charge or to guarantee a certain minimum distance. The advantages of codes designed by this method over similar codes are the improved run-length/accumulated-charge parameters, higher transmission rate, and the systematic nature of the code construction. The multilevel structure allows the redundancy in the signal selection procedure to be allocated efficiently among the different levels. It also allows the use of suboptimal staged decoding procedures that have performance/complexity advantages over maximum-likelihood decoding.

  16. Data-derived symbol synchronization of MASK and QASK signals. [for multilevel digital communication systems

    NASA Technical Reports Server (NTRS)

    Simon, M. K.

    1974-01-01

    Multilevel amplitude-shift-keying (MASK) and quadrature amplitude-shift-keying (QASK) as signaling techniques for multilevel digital communications systems, and the problem of providing symbol synchronization in the receivers of such systems are discussed. A technique is presented for extracting symbol sync from an MASK or QASK signal. The scheme is a generalization of the data transition tracking loop used in PSK systems. The performance of the loop was analyzed in terms of its mean-squared jitter and its effects on the data detection process in MASK and QASK systems.

  17. Multilevel Cell Storage and Resistance Variability in Resistive Random Access Memory

    NASA Astrophysics Data System (ADS)

    Pantelis, D. I.; Karakizis, P. N.; Dragatogiannis, D. A.; Charitidis, C. A.

    2016-06-01

    Multilevel per cell (MLC) storage in resistive random access memory (ReRAM) is attractive in achieving high-density and low-cost memory and will be required in future. In this chapter, MLC storage and resistance variability and reliability of multilevel in ReRAM are discussed. Different MLC operation schemes with their physical mechanisms and a comprehensive analysis of resistance variability have been provided. Various factors that can induce variability and their effect on the resistance margin between the multiple resistance levels are assessed. The reliability characteristics and the impact on MLC storage have also been assessed.

  18. Landau Zener scenario in a trapped atomic gas: multi-level multi-particle model

    NASA Astrophysics Data System (ADS)

    Fai, Lukong Cornelius; Tchoffo, Martin; Jipdi, Michael Nana

    2015-07-01

    The paper investigates multi-level and multi-particle Landau-Zener problem applying the dynamic matrix approach. The Landau Zener transitions are observed to depend sensitively on the frequency, phase of interaction and number of levels and particles. The dynamic behaviour of atomic trapped gas is solved for one particle model that permits to deduce different probabilities for particular initial conditions. The generalization of the probabilities permits to solve any multi-level system with an arbitrary number of particles and controlled particle transitions.

  19. LOADING SIMULATION PROGRAM C

    EPA Science Inventory

    LSPC is the Loading Simulation Program in C++, a watershed modeling system that includes streamlined Hydrologic Simulation Program Fortran (HSPF) algorithms for simulating hydrology, sediment, and general water quality on land as well as a simplified stream transport model. LSPC ...

  20. Statistical load data processing

    NASA Technical Reports Server (NTRS)

    Vandijk, G. M.

    1972-01-01

    A recorder system has been installed on two operational fighter aircrafts. Signal values from a c.g.-acceleration transducer and a strain-gage installation at the wing root were sampled and recorded in digital format on the recorder system. To analyse such load-time histories for fatigue evaluation purposes, a number of counting methods are available in which level crossings, peaks, or ranges are counted. Ten different existing counting principles are defined. The load-time histories are analysed to evaluate these counting methods. For some of the described counting methods, the counting results might be affected by arbitrarily chosen parameters such as the magnitude of load ranges that will be neglected and other secondary counting restrictions. Such influences might invalidate the final counting results entirely. The evaluation shows that for the type of load-time histories associated with most counting methods, a sensible value of the parameters involved can be found.

  1. Load proportional safety brake

    NASA Technical Reports Server (NTRS)

    Cacciola, M. J.

    1979-01-01

    This brake is a self-energizing mechanical friction brake and is intended for use in a rotary drive system. It incorporates a torque sensor which cuts power to the power unit on any overload condition. The brake is capable of driving against an opposing load or driving, paying-out, an aiding load in either direction of rotation. The brake also acts as a no-back device when torque is applied to the output shaft. The advantages of using this type of device are: (1) low frictional drag when driving; (2) smooth paying-out of an aiding load with no runaway danger; (3) energy absorption proportional to load; (4) no-back activates within a few degrees of output shaft rotation and resets automatically; and (5) built-in overload protection.

  2. LOADING MACHINE FOR REACTORS

    DOEpatents

    Simon, S.L.

    1959-07-01

    An apparatus is described for loading or charging slugs of fissionable material into a nuclear reactor. The apparatus of the invention is a "muzzle loading" type comprising a delivery tube or muzzle designed to be brought into alignment with any one of a plurality of fuel channels. The delivery tube is located within the pressure shell and it is also disposed within shielding barriers while the fuel cantridges or slugs are forced through the delivery tube by an externally driven flexible ram.

  3. Rim loaded reflector antennas

    NASA Astrophysics Data System (ADS)

    Bucci, O. M.; Franceschetti, G.

    1980-05-01

    A general theory of reflector antennas loaded by surface impedances is presented. Spatial variation of primary illumination is taken into account using a generalized slope diffraction coefficient. The theory is experimentally checked on surface loaded square plate scatterers and then used for computing the radiation diagram of parabolic and hyperbolic dishes. Computer programs and computed diagrams refer to the case of focal illumination and negligible tapering of primary illumination.

  4. Load research manual. Volume 3. Load research for advanced technologies

    SciTech Connect

    Brandenburg, L.; Clarkson, G.; Grund, Jr., C.; Leo, J.; Asbury, J.; Brandon-Brown, F.; Derderian, H.; Mueller, R.; Swaroop, R.

    1980-11-01

    This three-volume manual presents technical guidelines for electric utility load research. Special attention is given to issues raised by the load data reporting requirements of the Public Utility Regulatory Policies Act of 1978 and to problems faced by smaller utilities that are initiating load research programs. The manual includes guides to load research literature and glossaries of load research and statistical terms. In Volume 3, special load research procedures are presented for solar, wind, and cogeneration technologies.

  5. Composite Load Model Evaluation

    SciTech Connect

    Lu, Ning; Qiao, Hong

    2007-09-30

    The WECC load modeling task force has dedicated its effort in the past few years to develop a composite load model that can represent behaviors of different end-user components. The modeling structure of the composite load model is recommended by the WECC load modeling task force. GE Energy has implemented this composite load model with a new function CMPLDW in its power system simulation software package, PSLF. For the last several years, Bonneville Power Administration (BPA) has taken the lead and collaborated with GE Energy to develop the new composite load model. Pacific Northwest National Laboratory (PNNL) and BPA joint force and conducted the evaluation of the CMPLDW and test its parameter settings to make sure that: • the model initializes properly, • all the parameter settings are functioning, and • the simulation results are as expected. The PNNL effort focused on testing the CMPLDW in a 4-bus system. An exhaustive testing on each parameter setting has been performed to guarantee each setting works. This report is a summary of the PNNL testing results and conclusions.

  6. Ultra-short pulse propagation in multi-level media

    NASA Astrophysics Data System (ADS)

    Clader, B. David

    We consider the propagation of short, intense laser pulses through media consisting of two-level and three-level atoms. We derive the coupled Maxwell-Bloch (MB) equations, which describe such propagation. Many different physical situations have been studied by analyzing various limiting cases of these equations. Most of the recent work has relied on steady-state or adiabatic assumptions to simplify the analysis of the MB equations. However rapid progress has been made in recent years in developing analytic solution techniques that do not require these simplifications, such as BAcklund transformations, inverse scattering methods, and Darboux transformations. We use the Backlund solution method, to derive soliton solutions to the MB equations for various physical situations of interest in multi-level media. In addition we examine the experimental applicability of the exact solutions by numerically integrating the MB equations for more physically realistic pulse shapes and media preparations that may not permit analytic solutions. In two-level inverted gain media, we derive a pulse solution with group velocity exceeding the speed of light in vacuum (fast light). Numerical results confirm that such a pulse can exhibit fractional peak advances exceeding one pulse width despite spontaneous instabilites such as superfluorescence and stimulated instabilities related to the McCall-Hahn area theorem. In three-level Λ type media we derive soliton solutions for two pulses propagating through a medium prepared in an arbitrary mixed-state of the two ground states. We include a tunable parameter in the solutions that allows one to vary the medium between completely mixed state and completely pure-state superpositions known as "phaseonium". This flexibility allows one to study the interplay between stimulated Raman scattering, electromagnetically induced transparency (EIT), self induced transparency (SIT), and pulse matching. Past results have indicated that asymptotic pulse

  7. Multilevel Resistance Programming in Conductive Bridge Resistive Memory

    NASA Astrophysics Data System (ADS)

    Mahalanabis, Debayan

    This work focuses on the existence of multiple resistance states in a type of emerging non-volatile resistive memory device known commonly as Programmable Metallization Cell (PMC) or Conductive Bridge Random Access Memory (CBRAM), which can be important for applications such as multi-bit memory as well as non-volatile logic and neuromorphic computing. First, experimental data from small signal, quasi-static and pulsed mode electrical characterization of such devices are presented which clearly demonstrate the inherent multi-level resistance programmability property in CBRAM devices. A physics based analytical CBRAM compact model is then presented which simulates the ion-transport dynamics and filamentary growth mechanism that causes resistance change in such devices. Simulation results from the model are fitted to experimental dynamic resistance switching characteristics. The model designed using Verilog-a language is computation-efficient and can be integrated with industry standard circuit simulation tools for design and analysis of hybrid circuits involving both CMOS and CBRAM devices. Three main circuit applications for CBRAM devices are explored in this work. Firstly, the susceptibility of CBRAM memory arrays to single event induced upsets is analyzed via compact model simulation and experimental heavy ion testing data that show possibility of both high resistance to low resistance and low resistance to high resistance transitions due to ion strikes. Next, a non-volatile sense amplifier based flip-flop architecture is proposed which can help make leakage power consumption negligible by allowing complete shutdown of power supply while retaining its output data in CBRAM devices. Reliability and energy consumption of the flip-flop circuit for different CBRAM low resistance levels and supply voltage values are analyzed and compared to CMOS designs. Possible extension of this architecture for threshold logic function computation using the CBRAM devices as re

  8. Exploring the impact of different multi-level measures of physician communities in patient-centric care networks on healthcare outcomes: A multi-level regression approach

    PubMed Central

    Uddin, Shahadat

    2016-01-01

    A patient-centric care network can be defined as a network among a group of healthcare professionals who provide treatments to common patients. Various multi-level attributes of the members of this network have substantial influence to its perceived level of performance. In order to assess the impact different multi-level attributes of patient-centric care networks on healthcare outcomes, this study first captured patient-centric care networks for 85 hospitals using health insurance claim dataset. From these networks, this study then constructed physician collaboration networks based on the concept of patient-sharing network among physicians. A multi-level regression model was then developed to explore the impact of different attributes that are organised at two levels on hospitalisation cost and hospital length of stay. For Level-1 model, the average visit per physician significantly predicted both hospitalisation cost and hospital length of stay. The number of different physicians significantly predicted only the hospitalisation cost, which has significantly been moderated by age, gender and Comorbidity score of patients. All Level-1 findings showed significance variance across physician collaboration networks having different community structure and density. These findings could be utilised as a reflective measure by healthcare decision makers. Moreover, healthcare managers could consider them in developing effective healthcare environments. PMID:26842548

  9. Belief in a Just World, Teacher Justice, and Student Achievement: A Multilevel Study

    ERIC Educational Resources Information Center

    Peter, Felix; Kloeckner, Nils; Dalbert, Claudia; Radant, Matthias

    2012-01-01

    The meaning of belief in a just world and students' subjective experience of the justice of their teachers' behavior toward them personally for academic achievement was examined. Sample 1 involved 947 secondary school students from 67 classes (grade levels 9 to 11), and Sample 2 718 students from 48 classes (grade level 9). Multilevel analyses…

  10. Assessing Impact, DIF, and DFF in Accommodated Item Scores: A Comparison of Multilevel Measurement Model Parameterizations

    ERIC Educational Resources Information Center

    Beretvas, S. Natasha; Cawthon, Stephanie W.; Lockhart, L. Leland; Kaye, Alyssa D.

    2012-01-01

    This pedagogical article is intended to explain the similarities and differences between the parameterizations of two multilevel measurement model (MMM) frameworks. The conventional two-level MMM that includes item indicators and models item scores (Level 1) clustered within examinees (Level 2) and the two-level cross-classified MMM (in which item…

  11. The Impact of a Multilevel Intervention on Special Education Induction Teacher Retention Indicators

    ERIC Educational Resources Information Center

    Imel, Breck

    2012-01-01

    This mixed methods action research study explores the impact of a multilevel intervention on retention indicators of special education induction teachers and the leadership capacities of the special education induction coaches and coordinator. The purpose of this investigation was to understand the impact of developing and implementing an action…

  12. Multilevel Structural Equation Models for the Analysis of Comparative Data on Educational Performance

    ERIC Educational Resources Information Center

    Goldstein, Harvey; Bonnet, Gerard; Rocher, Thierry

    2007-01-01

    The Programme for International Student Assessment comparative study of reading performance among 15-year-olds is reanalyzed using statistical procedures that allow the full complexity of the data structures to be explored. The article extends existing multilevel factor analysis and structural equation models and shows how this can extract richer…

  13. Modeling the Factors Associated with Children's Mental Health Difficulties in Primary School: A Multilevel Study

    ERIC Educational Resources Information Center

    Humphrey, Neil; Wigelsworth, Michael

    2012-01-01

    The current study explores some of the factors associated with children's mental health difficulties in primary school. Multilevel modeling with data from 628 children from 36 schools was used to determine how much variation in mental health difficulties exists between and within schools, and to identify characteristics at the school and…

  14. Measuring Effective Teacher-Student Interactions from a Student Perspective: A Multilevel Analysis

    ERIC Educational Resources Information Center

    Downer, Jason T.; Stuhlman, Megan; Schweig, Jonathan; Martínez, José Felipe; Ruzek, Erik

    2015-01-01

    This study applies multi-level analysis to student reports of effective teacher-student interactions in 50 upper elementary school classrooms (N = 594 fourth- and fifth-grade students). Observational studies suggest that teacher-student interactions fall into three domains: Emotional Support, Classroom Organization, and Instructional Support.…

  15. Neighborhoods, Social Support, and African American Adolescents' Mental Health Outcomes: A Multilevel Path Analysis

    ERIC Educational Resources Information Center

    Hurd, Noelle M.; Stoddard, Sarah A.; Zimmerman, Marc A.

    2013-01-01

    This study explored how neighborhood characteristics may relate to African American adolescents' internalizing symptoms via adolescents' social support and perceptions of neighborhood cohesion. Participants included 571 urban, African American adolescents (52% female; "M" age = 17.8). A multilevel path analysis testing both direct and indirect…

  16. Motivating Proteges' Personal Learning in Teams: A Multilevel Investigation of Autonomy Support and Autonomy Orientation

    ERIC Educational Resources Information Center

    Liu, Dong; Fu, Ping-ping

    2011-01-01

    This study examined the roles of 3 multilevel motivational predictors in proteges' personal learning in teams: an autonomy-supportive team climate, mentors' autonomy support, and proteges' autonomy orientation. The authors followed 305 proteges in 58 teams for 12 weeks and found that all 3 predictors were positively related to the proteges'…

  17. From Autonomy to Creativity: A Multilevel Investigation of the Mediating Role of Harmonious Passion

    ERIC Educational Resources Information Center

    Liu, Dong; Chen, Xiao-Ping; Yao, Xin

    2011-01-01

    Building on self-determination theory, we theorized about and demonstrated, through 2 multilevel field studies, the pivotal role of harmonious passion in translating organizational autonomy support and individual autonomy orientation into job creativity. Results based on 3-level data from 856 members in 111 teams within 23 work units of a porous…

  18. A Multilevel Model of Minority Opinion Expression and Team Decision-Making Effectiveness

    ERIC Educational Resources Information Center

    Park, Guihyun; DeShon, Richard P.

    2010-01-01

    The consideration of minority opinions when making team decisions is an important factor that contributes to team effectiveness. A multilevel model of minority opinion influence in decision-making teams is developed to address the conditions that relate to adequate consideration of minority opinions. Using a sample of 57 teams working on a…

  19. Multilevel Analysis for Applied Research: It's Just Regression! Methodology in the Social Sciences

    ERIC Educational Resources Information Center

    Bickel, Robert

    2007-01-01

    This book provides a uniquely accessible introduction to multilevel modeling, a powerful tool for analyzing relationships between an individual level dependent variable, such as student reading achievement, and individual-level and contextual explanatory factors, such as gender and neighborhood quality. Helping readers build on the statistical…

  20. A Multilevel Analysis of the Relationships among Communal School Organization, Student Bonding, and Delinquency

    ERIC Educational Resources Information Center

    Payne, Allison Ann

    2008-01-01

    Research has identified school-related factors that are predictive of a student's involvement in delinquency: specifically, school-level communal school organization and individual-level student bonding. Hierarchical linear modeling was used to examine the multilevel relationships among these concepts in a nationally representative sample of…

  1. Multi-Level Model of Contextual Factors and Teachers' Assessment Practices: An Integrative Review of Research

    ERIC Educational Resources Information Center

    Fulmer, Gavin W.; Lee, Iris C. H.; Tan, Kelvin H. K.

    2015-01-01

    We present a multi-level model of contextual factors that may influence teachers' assessment practices, and use this model in a selected review of existing literature on teachers' assessment knowledge, views and conceptions with respect to these contextual factors. Adapting Kozma's model, we distinguish three levels of influence on teachers'…

  2. Asymptotic Effect of Misspecification in the Random Part of the Multilevel Model

    ERIC Educational Resources Information Center

    Berkhof, Johannes; Kampen, Jarl Kennard

    2004-01-01

    The authors examine the asymptotic effect of omitting a random coefficient in the multilevel model and derive expressions for the change in (a) the variance components estimator and (b) the estimated variance of the fixed effects estimator. They apply the method of moments, which yields a closed form expression for the omission effect. In…

  3. A New Approach for Estimating a Nonlinear Growth Component in Multilevel Modeling

    ERIC Educational Resources Information Center

    Tolvanen, Asko; Kiuru, Noona; Leskinen, Esko; Hakkarainen, Kai; Inkinen, Mikko; Lonka, Kirsti; Salmela-Aro, Katariina

    2011-01-01

    This study presents a new approach to estimation of a nonlinear growth curve component with fixed and random effects in multilevel modeling. This approach can be used to estimate change in longitudinal data, such as day-of-the-week fluctuation. The motivation of the new approach is to avoid spurious estimates in a random coefficient regression…

  4. Perceived Learning Environment and Students' Emotional Experiences: A Multilevel Analysis of Mathematics Classrooms

    ERIC Educational Resources Information Center

    Frenzel, Anne C.; Pekrun, Reinhard; Goetz, Thomas

    2007-01-01

    A multilevel approach was used to analyze relationships between perceived classroom environments and emotions in mathematics. Based on Pekrun's (2000) [A social-cognitive, control-value theory of achievement emotions. In J. Heckhausen (Ed.), Motivational psychology of human development (pp. 143-163)] social-cognitive, control-value theory of…

  5. Computational Tools for Probing Interactions in Multiple Linear Regression, Multilevel Modeling, and Latent Curve Analysis

    ERIC Educational Resources Information Center

    Preacher, Kristopher J.; Curran, Patrick J.; Bauer, Daniel J.

    2006-01-01

    Simple slopes, regions of significance, and confidence bands are commonly used to evaluate interactions in multiple linear regression (MLR) models, and the use of these techniques has recently been extended to multilevel or hierarchical linear modeling (HLM) and latent curve analysis (LCA). However, conducting these tests and plotting the…

  6. Multilevel Latent Class Analysis: An Application of Adolescent Smoking Typologies with Individual and Contextual Predictors

    ERIC Educational Resources Information Center

    Henry, Kimberly L.; Muthen, Bengt

    2010-01-01

    Latent class analysis (LCA) is a statistical method used to identify subtypes of related cases using a set of categorical or continuous observed variables. Traditional LCA assumes that observations are independent. However, multilevel data structures are common in social and behavioral research and alternative strategies are needed. In this…

  7. Multi-Level Partnerships Support a Comprehensive Faith-Based Health Promotion Program

    ERIC Educational Resources Information Center

    Hardison-Moody, Annie; Dunn, Carolyn; Hall, David; Jones, Lorelei; Newkirk, Jimmy; Thomas, Cathy

    2011-01-01

    This article examines the role of multi-level partnerships in implementing Faithful Families Eating Smart and Moving More, a faith-based health promotion program that works with low-resource faith communities in North Carolina. This program incorporates a nine-lesson individual behavior change program in concert with policy and environmental…

  8. Observations of Student Behavior in Nonclassroom Settings: A Multilevel Examination of Location, Density, and School Context

    ERIC Educational Resources Information Center

    Cash, Anne H.; Bradshaw, Catherine P.; Leaf, Philip J.

    2015-01-01

    Observational methods are increasingly used to assess the impact of school-based interventions. Yet, few studies have used observations in nonclassroom settings, such as hallways or the cafeteria, or explored aspects of the school context that may be related to the observed behavior. The current study used a multilevel approach to examine…

  9. Multilevel Analysis of the Effects of Antidiscrimination Policies on Earnings by Sexual Orientation

    ERIC Educational Resources Information Center

    Klawitter, Marieka

    2011-01-01

    This study uses the 2000 U.S. Census data to assess the impact of antidiscrimination policies for sexual orientation on earnings for gays and lesbians. Using a multilevel model allows estimation of the effects of state and local policies on earnings and of variation in the effects of sexual orientation across local labor markets. The results…

  10. The Multi-Level Classroom or the One Room Little Red School-House Revisited.

    ERIC Educational Resources Information Center

    Courchene, Robert

    1984-01-01

    Describes language lab listening activity designed to serve needs of the English as a second language class comprised of students at different levels of language proficiency, divergent native languages, multicultural backgrounds, and varying levels of formal education. Multilevel tasks are drawn from a common text, allowing students to do…

  11. Framing ICT Implementation in a Context of Educational Change: A Multilevel Analysis

    ERIC Educational Resources Information Center

    Wong, Emily M. L.; Li, S. C.

    2008-01-01

    Despite frequent attempts to address educational changes and the roles of information and communication technology (ICT) in effecting changes in student learning, few have conceptually examined ICT implementation within a wider context of managing change in schools. Methodologically, it has been argued that ignoring the multilevel nature of the…

  12. "Using Power Tables to Compute Statistical Power in Multilevel Experimental Designs"

    ERIC Educational Resources Information Center

    Konstantopoulos, Spyros

    2009-01-01

    Power computations for one-level experimental designs that assume simple random samples are greatly facilitated by power tables such as those presented in Cohen's book about statistical power analysis. However, in education and the social sciences experimental designs have naturally nested structures and multilevel models are needed to compute the…

  13. Multilevel resistive switching nonvolatile memory based on MoS2 nanosheet-embedded graphene oxide

    NASA Astrophysics Data System (ADS)

    Shin, Gwang Hyuk; Kim, Choong-Ki; Bang, Gyeong Sook; Kim, Jong Yun; Jang, Byung Chul; Koo, Beom Jun; Woo, Myung Hun; Choi, Yang-Kyu; Choi, Sung-Yool

    2016-09-01

    An increasing demand for nonvolatile memory has driven extensive research on resistive switching memory because it uses simple structures with high density, fast switching speed, and low power consumption. To improve the storage density, the application of multilevel cells is among the most promising solutions, including three-dimensional cross-point array architectures. Two-dimensional nanomaterials have several advantages as resistive switching media, including flexibility, low cost, and simple fabrication processes. However, few reports exist on multilevel nonvolatile memory and its switching mechanism. We herein present a multilevel resistive switching memory based on graphene oxide (GO) and MoS2 fabricated by a simple spin-coating process. Metallic 1T-MoS2 nanosheets, chemically exfoliated by Li intercalation, were successfully embedded between two GO layers as charge-trapping sites. The resulting stacks of GO/MoS2/GO exhibited excellent nonvolatile memory performance with at least four resistance states, >102 endurance cycles, and >104 s retention time. Furthermore, the charge transport mechanism was systematically investigated through the analysis of low-frequency 1/f noise in various resistance states, which could be modulated by the input voltage bias in the negative differential resistance region. Accordingly, we propose a strategy to achieve multilevel nonvolatile memory in which the stacked layers of two-dimensional nanosheets are utilized as resistive and charge-storage materials.

  14. Conceptualizing and Testing Random Indirect Effects and Moderated Mediation in Multilevel Models: New Procedures and Recommendations

    ERIC Educational Resources Information Center

    Bauer, Daniel J.; Preacher, Kristopher J.; Gil, Karen M.

    2006-01-01

    The authors propose new procedures for evaluating direct, indirect, and total effects in multilevel models when all relevant variables are measured at Level 1 and all effects are random. Formulas are provided for the mean and variance of the indirect and total effects and for the sampling variances of the average indirect and total effects.…

  15. Multilevel Factor Analyses of Family Data from the Hawai'i Family Study of Cognition

    ERIC Educational Resources Information Center

    McArdle, John J.; Hamagami, Fumiaki; Bautista, Randy; Onoye, Jane; Hishinuma, Earl S.; Prescott, Carol A.; Takeshita, Junji; Zonderman, Alan B.; Johnson, Ronald C.

    2014-01-01

    In this study, we reanalyzed the classic Hawai'i Family Study of Cognition (HFSC) data using contemporary multilevel modeling techniques. We used the HFSC baseline data ("N" = 6,579) and reexamined the factorial structure of 16 cognitive variables using confirmatory (restricted) measurement models in an explicit sequence. These…

  16. A Multilevel Investigation of Relationships between Australian Teachers' Career Stages and Locus of Control

    ERIC Educational Resources Information Center

    McCormick, John; Barnett, Kerry

    2008-01-01

    Purpose: The purpose of this paper was to posit and test hypotheses concerned with relationships between teachers' demographics, locus of control and career stages. Design/methodology/approach: A sample consisting of 416 Australian non-executive high school teachers was gathered from 40 randomly selected high schools. Multilevel regression…

  17. Multilevel pulse-position modulation for optical power-efficient communication.

    PubMed

    Karlsson, Magnus; Agrell, Erik

    2011-12-12

    A family of modulation formats is derived by combining pulse-position modulation (PPM) with multilevel dual-polarization signal constellations. With 16-PPM, gains of up to 5.4 dB are obtained over dual-polarization QPSK, at the cost of reduced spectral efficiency. PMID:22274105

  18. A Multilevel Perspective on the Climate of Bullying: Discrepancies among Students, School Staff, and Parents

    ERIC Educational Resources Information Center

    Waasdorp, Tracy Evian; Pas, Elise T.; O'Brennan, Lindsey M.; Bradshaw, Catherine P.

    2011-01-01

    Although many bullying prevention programs aim to involve multiple partners, few studies have examined perceptual differences regarding peer victimization and the broader bullying climate among students, staff, and parents. The present study utilized multilevel data from 11,674 students, 960 parents, and 1,027 staff at 44 schools to examine the…

  19. A Multi-Level Analysis of Risk Factors for Campylobacter spp. in Broiler Chickens in Iceland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Introduction We carried out a longitudinal study of the broiler industry in Iceland between May 2001 and September 2004. Using multi-level statistical methods, our objective was to determine which aspects of the birds, their management and/or their housing may be most useful for applying interventi...

  20. High School Social Climate and Antisocial Behavior: A 10 Year Longitudinal and Multilevel Study

    ERIC Educational Resources Information Center

    Leblanc, Line; Swisher, Raymond; Vitaro, Frank; Tremblay, Richard E.

    2008-01-01

    A longitudinal and multilevel approach is used to examine the relationship between antisocial behavior during adolescence and high school social climate. The data are taken from a longitudinal study of 1,233 boys and girls who attended 217 public and private high schools. Students' disruptive behaviors were assessed yearly from 6 to 12 years of…

  1. Evidencing Learning Outcomes: A Multi-Level, Multi-Dimensional Course Alignment Model

    ERIC Educational Resources Information Center

    Sridharan, Bhavani; Leitch, Shona; Watty, Kim

    2015-01-01

    This conceptual framework proposes a multi-level, multi-dimensional course alignment model to implement a contextualised constructive alignment of rubric design that authentically evidences and assesses learning outcomes. By embedding quality control mechanisms at each level for each dimension, this model facilitates the development of an aligned…

  2. When Cannabis Is Available and Visible at School--A Multilevel Analysis of Students' Cannabis Use

    ERIC Educational Resources Information Center

    Kuntsche, Emmanuel

    2010-01-01

    Aims: To investigate the links between the visibility of cannabis use in school (measured by teachers' reports of students being under the influence of cannabis on school premises), the proportion of cannabis users in the class, perceived availability of cannabis, as well as adolescent cannabis use. Methods: A multilevel regression model was…

  3. Synthesis of Single-Case Experimental Data: A Comparison of Alternative Multilevel Approaches

    ERIC Educational Resources Information Center

    Ferron, John; Van den Noortgate, Wim; Beretvas, Tasha; Moeyaert, Mariola; Ugille, Maaike; Petit-Bois, Merlande; Baek, Eun Kyeng

    2013-01-01

    Single-case or single-subject experimental designs (SSED) are used to evaluate the effect of one or more treatments on a single case. Although SSED studies are growing in popularity, the results are in theory case-specific. One systematic and statistical approach for combining single-case data within and across studies is multilevel modeling. The…

  4. Multilevel Synthesis of Single-Case Experimental Data: An Empirical Validation

    ERIC Educational Resources Information Center

    Van den Noortgate, Wim; Moeyaert, Mariola; Ugille, Maaike; Beretvas, Tasha; Ferron, John

    2012-01-01

    The purpose of the study is to investigate empirically the multilevel approach for combining single-case or single-subject experimental designs (SSED) data. More specifically, the authors aim at assessing the value of the approach for numbers of observations, cases and studies that are common in SSED research, by looking at the bias and precision…

  5. Documenting Attitudes toward Undocumented Immigrant Access to Public Education: A Multilevel Analysis

    ERIC Educational Resources Information Center

    Herrera, Felisha A.; Garibay, Juan C.; Garcia, Gina A.; Johnston, Marc P.

    2013-01-01

    This study investigates how students' views toward undocumented immigrants' access to public education change during college. A multilevel analysis among a national sample of 12,388 undergraduates, drawn from the Cooperative Institutional Research Program's (CIRP) Freshman Survey and College Senior Survey, revealed that significant…

  6. A Multilevel Multivariate Analysis of Academic Performances in College Based on NCAA Student-Athletes

    ERIC Educational Resources Information Center

    McArdle, John J.; Paskus, Thomas S.; Boker, Steven M.

    2013-01-01

    This is an application of contemporary multilevel regression modeling to the prediction of academic performances of 1st-year college students. At a first level of analysis, the data come from N greater than 16,000 students who were college freshman in 1994-1995 and who were also participants in high-level college athletics. At a second level of…

  7. Graduate Attribute Attainment in a Multi-Level Undergraduate Geography Course

    ERIC Educational Resources Information Center

    Mager, Sarah; Spronken-Smith, Rachel

    2014-01-01

    We investigated students' perceptions of graduate attributes in a multi-level (second and third year) geography course. A case study with mixed methodology was employed, with data collected through focus groups and a survey. We found that undergraduate geography students can identify the skills, knowledge and attributes that are developed…

  8. Multilevel decomposition of complete vehicle configuration in a parallel computing environment

    NASA Technical Reports Server (NTRS)

    Bhatt, Vinay; Ragsdell, K. M.

    1989-01-01

    This research summarizes various approaches to multilevel decomposition to solve large structural problems. A linear decomposition scheme based on the Sobieski algorithm is selected as a vehicle for automated synthesis of a complete vehicle configuration in a parallel processing environment. The research is in a developmental state. Preliminary numerical results are presented for several example problems.

  9. Multi-Level Assessment of Scientific Content Knowledge Gains Associated with Socioscientific Issues-Based Instruction

    ERIC Educational Resources Information Center

    Klosterman, Michelle L.; Sadler, Troy D.

    2010-01-01

    This study explored the impact of using a socioscientific issue (SSI) based curriculum on developing science content knowledge. Using a multi-level assessment design, student content knowledge gains were measured before and after implementation of a three-week unit on global warming (a prominent SSI) that explored both the relevant science content…

  10. A Bayesian Multi-Level Factor Analytic Model of Consumer Price Sensitivities across Categories

    ERIC Educational Resources Information Center

    Duvvuri, Sri Devi; Gruca, Thomas S.

    2010-01-01

    Identifying price sensitive consumers is an important problem in marketing. We develop a Bayesian multi-level factor analytic model of the covariation among household-level price sensitivities across product categories that are substitutes. Based on a multivariate probit model of category incidence, this framework also allows the researcher to…

  11. GROUND WATER MONITORING AND SAMPLING: MULTI-LEVEL VERSUS TRADITIONAL METHODS WHATS WHAT?

    EPA Science Inventory

    After years of research and many publications, the question still remains: What is the best method to collect representative ground water samples from monitoring wells? Numerous systems and devices are currently available for obtaining both multi-level samples as well as traditi...

  12. Applications of Multilevel Structural Equation Modeling to Cross-Cultural Research

    ERIC Educational Resources Information Center

    Cheung, Mike W.-L.; Au, Kevin

    2005-01-01

    Multilevel structural equation modeling (MSEM) has been proposed as an extension to structural equation modeling for analyzing data with nested structure. We have begun to see a few applications in cross-cultural research in which MSEM fits well as the statistical model. However, given that cross-cultural studies can only afford collecting data…

  13. Hybrid Surgery of Multilevel Cervical Degenerative Disc Disease : Review of Literature and Clinical Results

    PubMed Central

    Lee, Sang-Bok; Kim, Jong-Youn; Yoo, Do-Sung; Lee, Tae-Gyu; Huh, Pil-Woo

    2012-01-01

    Objective In the present study, we evaluated the effect, safety and radiological outcomes of cervical hybrid surgery (cervical disc prosthesis replacement at one level, and interbody fusion at the other level) on the multilevel cervical degenerative disc disease (DDD). Methods Fifty-one patients (mean age 46.7 years) with symptomatic multilevel cervical spondylosis were treated using hybrid surgery (HS). Clinical [neck disability index (NDI) and Visual Analogue Scale (VAS) score] and radiologic outcomes [range of motion (ROM) for cervical spine, adjacent segment and arthroplasty level] were evaluated at routine postoperative intervals of 1, 6, 12, 24 months. Review of other similar studies that examined the HS in multilevel cervical DDD was performed. Results Out of 51 patients, 41 patients received 2 level hybrid surgery and 10 patients received 3 level hybrid surgery. The NDI and VAS score were significantly decreased during the follow up periods (p<0.05). The cervical ROM was recovered at 6 and 12 month postoperatively and the mean ROM of inferior adjacent segment was significantly larger than that of superior adjacent segments after surgery. The ROM of the arthoplasty level was preserved well during the follow up periods. No surgical and device related complications were observed. Conclusion Hybrid surgery is a safe and effective alternative to fusion for the management of multilevel cervical spondylosis. PMID:23323165

  14. Within-Cluster and Across-Cluster Matching with Observational Multilevel Data

    ERIC Educational Resources Information Center

    Kim, Jee-Seon; Steiner, Peter M.; Hall, Courtney; Thoemmes, Felix

    2013-01-01

    When randomized experiments cannot be conducted in practice, propensity score (PS) techniques for matching treated and control units are frequently used for estimating causal treatment effects from observational data. Despite the popularity of PS techniques, they are not yet well studied for matching multilevel data where selection into treatment…

  15. Estimating Treatment Effects via Multilevel Matching within Homogenous Groups of Clusters

    ERIC Educational Resources Information Center

    Steiner, Peter M.; Kim, Jee-Seon

    2015-01-01

    Despite the popularity of propensity score (PS) techniques they are not yet well studied for matching multilevel data where selection into treatment takes place among level-one units within clusters. This paper suggests a PS matching strategy that tries to avoid the disadvantages of within- and across-cluster matching. The idea is to first…

  16. Covariate Measurement Error Adjustment for Multilevel Models with Application to Educational Data

    ERIC Educational Resources Information Center

    Battauz, Michela; Bellio, Ruggero; Gori, Enrico

    2011-01-01

    This article proposes a multilevel model for the assessment of school effectiveness where the intake achievement is a predictor and the response variable is the achievement in the subsequent periods. The achievement is a latent variable that can be estimated on the basis of an item response theory model and hence subject to measurement error.…

  17. EVALUATION OF IN SITU COSOLVENT FLUSHING DYNAMICS USING A NETWORK OF SPATIALLY DISTRIBUTED MULTILEVEL SAMPLERS

    EPA Science Inventory

    A network of multilevel samplers was used to evaluate the spatial patterns in containment extraction during an in situ cosolvent flushing field test. The study was conducted in an isolation test cell installed in a fuel contaminated site at Hill Air Force Base, Utah. Partitioni...

  18. Grade Retention and Its Association with School Misconduct in Adolescence: A Multilevel Approach

    ERIC Educational Resources Information Center

    Demanet, Jannick; Van Houtte, Mieke

    2013-01-01

    Few studies with respect to grade retention and school-disruptive behavior have focused on adolescence. Moreover, previous retention research has ignored multilevel issues. This study aims to fill these research lacunae by addressing the role of grade retention in adolescent students' school misconduct. Furthermore, we explore the role of the…

  19. A multilevel model of the impact of farm-level best management practices on phosphorus runoff

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Multilevel or hierarchical models have been applied for a number of years in the social sciences but only relatively recently in the environmental sciences. These models can be developed in either a frequentist or Bayesian context and have similarities to other methods such as empirical Bayes analys...

  20. A Multilevel Model of Educational Expectations of Secondary School Students in the United States

    ERIC Educational Resources Information Center

    Lowman, Jennifer; Elliott, Marta

    2010-01-01

    Using the Educational Longitudinal Survey of 2002, we investigate variation in factors that contribute to Asian, Black, Hispanic, and White students' educational expectations. Separate multilevel models demonstrate group variation in student and school-level influences. Academic and school factors explained the most variation in White students'…