Effect of dowel bar looseness on measured load transfer efficiency using FWD load
NASA Astrophysics Data System (ADS)
Shoukry, Samir N.; William, Gergis W.; Riad, Mourad Y.
2001-07-01
The effect of dowel bar looseness on the joint load transfer efficiency using Falling Weight Deflectometer is the subject of this paper. The mechanism of dynamic load transfer at transverse joints of Jointed Plain Concrete Pavement is examined using nonlinear 3D finite element analysis.
NASA Astrophysics Data System (ADS)
Shibata, Hideaki; Tanaka, Yasutomo; Ono, Isamu; Okano, Tsuyoshi
2007-01-01
The FWD (Falling Weight Deflectometer) is an instrument which makes the weight fall freely on its loading plate to apply impact load and measures the displacement caused by the fall at the center of impact load and also at the points in radial direction from the center of impact load. A kind of instrument which is mounted on or drawn by a vehicle used for construction of concrete pavement or asphalt pavement of a runway is usually called FWD. The impact load of FWD is 49KN to 196kN and it can obtain the modulus of elasticity of each pavement layer by back analysis based on the theory of multi-layer elasticity using 6 to 8 of extemal displacement sensors. On the other hand, the small FWD is an FWD which is constructed small and easy and is applicable for hand carry. It makes the weight fall freely on the loading plate to apply impact load and measures the load and displacement caused by the fall. It was developed for mainly assessing the rigidity and bearing capacity of the subgrade easily and promptly. It can measure many points in short term and obtain coefficient of subgrade reaction and modulus of subgrade elasticity without using reaction facilities like as plate bearing test or CBR test. It has also been tried to apply the small FWD to low cost asphalt road pavement (later called as low cost road pavement). Application examples of small FWD test for earth structure and low cost load pavement in Japan are shown and the methods and test results are stated in this report.
Use of Benkelman Beams for Measuring LTE in Whitetopping: An Alternative Tool to FWD Test
NASA Astrophysics Data System (ADS)
Jundhare, D. R.; Khare, K. C.; Jain, R. K.
2012-09-01
Whitetopping is a rehabilitation or structural strengthening alternative on hot mix asphalt (HMA) pavement. It is constructed on the top of existing HMA pavement. Generally, falling weight deflectometer (FWD) deflection measurements are used to obtain the load transfer efficiency (LTE) of the transverse joints. However, the use of FWD in India has been very limited so far because of its high cost and difficulties encountered in maintaining the equipment. Therefore, a need has been aroused to identify an alternative to FWD test, which can be cost effective and easily available. In this work, Benkelman beam deflection test has been conducted using two Benkelman beams simultaneously placed on two adjacent slabs near transverse joint for measuring LTE of 150 mm thick in-service thin whitetopping constructed at Dahanukar Colony, Kothrud, Pune city. An alternative tool has been developed for measuring LTE in whitetopping.
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.
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…
Structural evaluation of pavement using surface wave and portable FWD tests
NASA Astrophysics Data System (ADS)
Dong, Q.; Kubodera, T.; Himeno, K.; Matsui, K.
2006-03-01
SASW has been well known as one of nondestructive testing methods for pavements. This method makes use of the dispersion characteristics to estimate the thickness and modulus of pavement layers. It is difficult to obtain accurate dispersion curves even if the analytical surface wave fields are used, where only the stiffness proportional damping is considered. However, the good agreement of dispersion curves has been found for the analytical surface wave fields if Rayleigh damping is adopted in the numerical simulation. In this paper, a dynamic general FEM software was developed to inverse the layer moduli and Rayleigh damping coefficient of the tested pavement structure using the portable FWD data. It shows that the predicted dispersion curves are well approximately to ones obtained from experimental SASW.
Parallel multilevel adaptive methods
NASA Technical Reports Server (NTRS)
Dowell, B.; Govett, M.; Mccormick, S.; Quinlan, D.
1989-01-01
The progress of a project for the design and analysis of a multilevel adaptive algorithm (AFAC/HM/) targeted for the Navier Stokes Computer is discussed. The results of initial timing tests of AFAC, coupled with multigrid and an efficient load balancer, on a 16-node Intel iPSC/2 hypercube are included. The results of timing tests are presented.
ERIC Educational Resources Information Center
Connections: A Journal of Adult Literacy, 1997
1997-01-01
This issue contains 12 articles written by teachers who have investigated various aspects of the multilevel question in their own classrooms. "The Multilevel Question" (Lenore Balliro) provides an introduction. "Deconstructing the Great Wall of Print" (Richard Goldberg) investigates reading strategies that allow students with a wide range of…
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 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.
Multilevel ensemble Kalman filtering
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.
Multilevel corporate environmental responsibility.
Karassin, Orr; Bar-Haim, Aviad
2016-12-01
The multilevel empirical study of the antecedents of corporate social responsibility (CSR) has been identified as "the first knowledge gap" in CSR research. Based on an extensive literature review, the present study outlines a conceptual multilevel model of CSR, then designs and empirically validates an operational multilevel model of the principal driving factors affecting corporate environmental responsibility (CER), as a measure of CSR. Both conceptual and operational models incorporate three levels of analysis: institutional, organizational, and individual. The multilevel nature of the design allows for the assessment of the relative importance of the levels and of their components in the achievement of CER. Unweighted least squares (ULS) regression analysis reveals that the institutional-level variables have medium relationships with CER, some variables having a negative effect. The organizational level is revealed as having strong and positive significant relationships with CER, with organizational culture and managers' attitudes and behaviors as significant driving forces. The study demonstrates the importance of multilevel analysis in improving the understanding of CSR drivers, relative to single level models, even if the significance of specific drivers and levels may vary by context.
Multilevel Interventions: Measurement and Measures
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
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.
Assessment of forest fuel loadings in Puerto Rico and the US Virgin Islands.
Brandeis, Thomas J; Woodall, Christopher W
2008-12-01
Quantification of the downed woody materials that comprise forest fuels has gained importance in Caribbean forest ecosystems due to the increasing incidence and severity of wildfires on island ecosystems. Because large-scale assessments of forest fuels have rarely been conducted for these ecosystems, forest fuels were assessed at 121 US Department of Agriculture forest service inventory plots on Puerto Rico, Vieques, and the US Virgin Islands. Results indicated that fuel loadings averaged 24.05 Mg ha(-1) in 2004-2006. Forest litter decreased from wetter to drier forest life zones. These island forests showed a paucity of coarse woody fuels (CWD) (2.91 Mg ha(-1)) and relatively greater quantities of smaller-sized fine woody fuels (FWD) (10.18 Mg ha(-1) for FWD and 10.82 Mg ha(-1) for duff/litter) when compared to continental tropical forests. Between 2001 and 2006, CWD fuel loads decreased, while fine fuels and litter increased, such that total fuel loads remained constant on a subset of plots on Puerto Rico. This trend indicates that continued decomposition of CWD deposited by the last severe hurricane is balanced by increasing inputs of FWD from recovering and maturing secondary forests. Forest disturbance cycles and successional development must be taken into account by agencies charged with fire protection and risk assessment.
Voltage balanced multilevel voltage source converter system
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.
Voltage balanced multilevel voltage source converter system
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.
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…
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…
Fast multilevel radiative transfer
NASA Astrophysics Data System (ADS)
Paletou, Frédéric; Léger, Ludovick
2007-01-01
The vast majority of recent advances in the field of numerical radiative transfer relies on approximate operator methods better known in astrophysics as Accelerated Lambda-Iteration (ALI). A superior class of iterative schemes, in term of rates of convergence, such as Gauss-Seidel and Successive Overrelaxation methods were therefore quite naturally introduced in the field of radiative transfer by Trujillo Bueno & Fabiani Bendicho (1995); it was thoroughly described for the non-LTE two-level atom case. We describe hereafter in details how such methods can be generalized when dealing with non-LTE unpolarised radiation transfer with multilevel atomic models, in monodimensional geometry.
Gossner, C M; Severi, E
2014-10-30
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.
Totally parallel multilevel algorithms
NASA Technical Reports Server (NTRS)
Frederickson, Paul O.
1988-01-01
Four totally parallel algorithms for the solution of a sparse linear system have common characteristics which become quite apparent when they are implemented on a highly parallel hypercube such as the CM2. These four algorithms are Parallel Superconvergent Multigrid (PSMG) of Frederickson and McBryan, Robust Multigrid (RMG) of Hackbusch, the FFT based Spectral Algorithm, and Parallel Cyclic Reduction. In fact, all four can be formulated as particular cases of the same totally parallel multilevel algorithm, which are referred to as TPMA. In certain cases the spectral radius of TPMA is zero, and it is recognized to be a direct algorithm. In many other cases the spectral radius, although not zero, is small enough that a single iteration per timestep keeps the local error within the required tolerance.
Parallel multilevel preconditioners
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.
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.
Nondestructive evaluation of load transfer at rigid airport pavement joints
NASA Astrophysics Data System (ADS)
Hammons, Michael I.
1995-07-01
Current design criteria for rigid pavements for commercial and military airfields assume that 25% of the load applied to an edge of a slab is transferred through the joint to an adjacent unloaded slab. A nondestructive testing technique using a falling weight deflectometer (FWD) was used to conduct field testing at a number of sites. A transfer function, developed from an analytical study, was used to estimate load transfer from the measured joint efficiency as a function of the loaded area and the radius of relative stiffness of the pavement. This procedure, although analytically sound, lacks actual field verification at an instrumented pavement site. This procedure was used to estimate load transfer at a number of commercial and military airfields for a variety of joint types, climate conditions, and pavement structures. The results of these tests indicate that the assumption of load transfer as a constant value of 25% appears to be unconservative, especially during the winter months.
Gupta, Anjana; McCluskey, Brandon; Bhaskaran, Shylesh; Muñoz, Steve; Oyajobi, Babatunde O.
2015-01-01
Treatment of multiple myeloma with bortezomib can result in severe adverse effects, necessitating the development of targeted inhibitors of the proteasome. We show that stable expression of a dominant-negative F-box deleted (ΔF) mutant of the E3 ubiquitin ligase, SCFβ-TrCP/FWD1, in murine 5TGM1 myeloma cells dramatically attenuated their skeletal engraftment and survival when inoculated into immunocompetent C57BL/KaLwRij mice. Similar results were obtained in immunodeficient bg-nu-xid mice, suggesting that the observed effects were independent of host recipient immune status. Bone marrow stroma offered no protection for 5TGM1-ΔF cells in cocultures treated with tumor necrosis factor (TNF), indicating a cell-autonomous anti-myeloma effect. Levels of p100, IκBα, Mcl-1, ATF4, total and cleaved caspase-3, and phospho-β-catenin were elevated in 5TGM1-ΔF cells whereas cIAP was down-regulated. TNF also activated caspase-3 and downregulated Bcl-2, correlating with the enhanced susceptibility of 5TGM1-ΔF cells to apoptosis. Treatment of 5TGM1 tumor-bearing mice with a β-TrCP1/FWD1 inhibitor, pyrrolidine dithiocarbamate (PDTC), significantly reduced tumor burden in bone. PDTC also increased levels of cleaved Mcl-1 and caspase-3 in U266 human myeloma cells, correlating with our murine data and validating the development of specific β-TrCP inhibitors as an alternative therapy to nonspecific proteasome inhibitors for myeloma patients. PMID:26009993
Multilevel turbulence simulations
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.
Challenges of evaluating multilevel interventions.
Nastasi, Bonnie K; Hitchcock, John
2009-06-01
This article uses the Comprehensive Mixed-Methods Participatory Evaluation (CMMPE; Nastasi and Hitchcock Transforming school mental health services: Population-based approaches to promoting the competency and wellness of children, Thousand Oaks, CA: Corwin Press with National Association of School Psychologists 2008; Nastasi et al. School-based mental health services: creating comprehensive and culturally specific programs. Washington, DC: American Psychological Association 2004) model as a framework for addressing the multiplicity of evaluation decisions and complex nature of questions related to program success in multilevel interventions. CMMPE defines program success in terms of acceptability, integrity, social or cultural validity, outcomes (impact), sustainability and institutionalization, thus broadening the traditional notions of program outcomes. The authors use CMMPE and an example of a community-based multilevel sexual risk prevention program with multiple outcomes to discuss challenges of evaluating multilevel interventions. The sexual risk program exemplifies what Schensul and Trickett (this issue) characterize as multilevel intervention-multilevel evaluation (M-M), with both intervention and evaluation at community, health practitioner, and patient levels. The illustration provides the context for considering several challenges related to M-M designs: feasibility of randomized controlled trials within community-based multilevel intervention; acceptability and social or cultural validity of evaluation procedures; implementer, recipient, and contextual variations in program success; interactions among levels of the intervention; unanticipated changes or conditions; multiple indicators of program success; engaging multiple stakeholders in a participatory process; and evaluating sustainability and institutionalization. The complexity of multilevel intervention and evaluation designs challenges traditional notions of evaluation research and experimental
Full-scale accelerated pavement testing of Texas Mobile Load Simulator
Chen, D.H.; Hugo, F.
1998-09-01
This paper presents the test results from full-scale accelerated pavement testing with the Texas Mobile Load Simulator. Data from in-situ instrumentation and nondestructive testing were collected and analyzed at different loading stages to assess material property changes under accelerated loading. Forensic studies were made to study material characteristics in the longitudinal and transverse directions. It was found that at the early stage of trafficking the test pad responded to falling weight deflectometer (FWD) load linearly, not only over the whole pavement system but also within individual layers. Before mobile load simulator testing, FWD data indicated the weakest area exists at the left wheel path (LWP) of 7.5-m line (7.5L). Later, this weak area was confirmed to have the highest rutting and the most intensive cracking. The dynamic cone penetration results showed that the base at this location was at its weakest. Also, at 7.5L the dry density was lowest, {approximately}7% lower with a moisture content {approximately}8% higher than the adjacent area. The LWP had higher FWD deflections than the right wheel path (RWP), and consequently the LWP manifested more rutting. This proved to be primarily due to differences in moisture content. This was probably because more water infiltrated in the area during rain due to manifestation of more extensive cracking during early phases of trafficking. The maximum surface deflection values increased as trafficking increased in the left and right wheel paths due to pavement deterioration, while deflection for the center remained constant because of the lack of traffic loading. The LWP had more rutting than the RWP and this correlated with the measured FWL deflections prior to trafficking. The WI values increased as trafficking increased for the LWP and RWP due to pavement deterioration. The majority (>60%) of rutting was from the 300-mm uncrushed river gravel base.
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,…
Multilevel Assessments of Science Standards
ERIC Educational Resources Information Center
Quellmalz, Edys S.; Timms, Michael J.; Silberglitt, Matt D.
2011-01-01
The Multilevel Assessment of Science Standards (MASS) project is creating a new generation of technology-enhanced formative assessments that bring the best formative assessment practices into classrooms to transform what, how, when, and where science learning is assessed. The project is investigating the feasibility, utility, technical quality,…
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…
Applications of Multilevel IRT Modeling
ERIC Educational Resources Information Center
Fox, Jean-Paul
2004-01-01
The recent development of multilevel IRT models (Fox & Glas, 2001, 2003) has been shown to be very useful for analyzing relationships between observed variables on different levels containing measurement error. Model parameter estimates and their standard deviations are concurrently estimated taking account of measurement error in observed…
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…
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.
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.
Experimental Model of Proximal Junctional Fracture after Multilevel Posterior Spinal Instrumentation
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
A multilevel stochastic collocation method for SPDEs
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.
Scalable Adaptive Multilevel Solvers for Multiphysics Problems
Xu, Jinchao
2014-11-26
In this project, we carried out many studies on adaptive and parallel multilevel methods for numerical modeling for various applications, including Magnetohydrodynamics (MHD) and complex fluids. We have made significant efforts and advances in adaptive multilevel methods of the multiphysics problems: multigrid methods, adaptive finite element methods, and applications.
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…
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.
A multilevel nonvolatile magnetoelectric memory
NASA Astrophysics Data System (ADS)
Shen, Jianxin; Cong, Junzhuang; Shang, Dashan; Chai, Yisheng; Shen, Shipeng; Zhai, Kun; Sun, Young
2016-09-01
The coexistence and coupling between magnetization and electric polarization in multiferroic materials provide extra degrees of freedom for creating next-generation memory devices. A variety of concepts of multiferroic or magnetoelectric memories have been proposed and explored in the past decade. Here we propose a new principle to realize a multilevel nonvolatile memory based on the multiple states of the magnetoelectric coefficient (α) of multiferroics. Because the states of α depends on the relative orientation between magnetization and polarization, one can reach different levels of α by controlling the ratio of up and down ferroelectric domains with external electric fields. Our experiments in a device made of the PMN-PT/Terfenol-D multiferroic heterostructure confirm that the states of α can be well controlled between positive and negative by applying selective electric fields. Consequently, two-level, four-level, and eight-level nonvolatile memory devices are demonstrated at room temperature. This kind of multilevel magnetoelectric memory retains all the advantages of ferroelectric random access memory but overcomes the drawback of destructive reading of polarization. In contrast, the reading of α is nondestructive and highly efficient in a parallel way, with an independent reading coil shared by all the memory cells.
A multilevel nonvolatile magnetoelectric memory
Shen, Jianxin; Cong, Junzhuang; Shang, Dashan; Chai, Yisheng; Shen, Shipeng; Zhai, Kun; Sun, Young
2016-01-01
The coexistence and coupling between magnetization and electric polarization in multiferroic materials provide extra degrees of freedom for creating next-generation memory devices. A variety of concepts of multiferroic or magnetoelectric memories have been proposed and explored in the past decade. Here we propose a new principle to realize a multilevel nonvolatile memory based on the multiple states of the magnetoelectric coefficient (α) of multiferroics. Because the states of α depends on the relative orientation between magnetization and polarization, one can reach different levels of α by controlling the ratio of up and down ferroelectric domains with external electric fields. Our experiments in a device made of the PMN-PT/Terfenol-D multiferroic heterostructure confirm that the states of α can be well controlled between positive and negative by applying selective electric fields. Consequently, two-level, four-level, and eight-level nonvolatile memory devices are demonstrated at room temperature. This kind of multilevel magnetoelectric memory retains all the advantages of ferroelectric random access memory but overcomes the drawback of destructive reading of polarization. In contrast, the reading of α is nondestructive and highly efficient in a parallel way, with an independent reading coil shared by all the memory cells. PMID:27681812
Detailed Modeling and Evaluation of a Scalable Multilevel Checkpointing System
Mohror, Kathryn; Moody, Adam; Bronevetsky, Greg; de Supinski, Bronis R.
2014-09-01
High-performance computing (HPC) systems are growing more powerful by utilizing more components. As the system mean time before failure correspondingly drops, applications must checkpoint frequently to make progress. But, at scale, the cost of checkpointing becomes prohibitive. A solution to this problem is multilevel checkpointing, which employs multiple types of checkpoints in a single run. Moreover, lightweight checkpoints can handle the most common failure modes, while more expensive checkpoints can handle severe failures. We designed a multilevel checkpointing library, the Scalable Checkpoint/Restart (SCR) library, that writes lightweight checkpoints to node-local storage in addition to the parallel file system. We present probabilistic Markov models of SCR's performance. We show that on future large-scale systems, SCR can lead to a gain in machine efficiency of up to 35 percent, and reduce the load on the parallel file system by a factor of two. In addition, we predict that checkpoint scavenging, or only writing checkpoints to the parallel file system on application termination, can reduce the load on the parallel file system by 20 × on today's systems and still maintain high application efficiency.
Multilevel modelling: Beyond the basic applications.
Wright, Daniel B; London, Kamala
2009-05-01
Over the last 30 years statistical algorithms have been developed to analyse datasets that have a hierarchical/multilevel structure. Particularly within developmental and educational psychology these techniques have become common where the sample has an obvious hierarchical structure, like pupils nested within a classroom. We describe two areas beyond the basic applications of multilevel modelling that are important to psychology: modelling the covariance structure in longitudinal designs and using generalized linear multilevel modelling as an alternative to methods from signal detection theory (SDT). Detailed code for all analyses is described using packages for the freeware R.
Planarization of metal films for multilevel interconnects
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.
Planarization of metal films for multilevel interconnects
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.
Planarization of metal films for multilevel interconnects
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.
Planarization of metal films for multilevel interconnects
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.
Planarization of metal films for multilevel interconnects
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.
On multilevel block modulation codes
NASA Technical Reports Server (NTRS)
Kasami, Tadao; Takata, Toyoo; Fujiwara, Toru; Lin, Shu
1991-01-01
The multilevel (ML) technique for combining block coding and modulation is investigated. A general formulation is presented for ML modulation codes in terms of component codes with appropriate distance measures. A specific method for constructing ML block modulation codes (MLBMCs) with interdependency among component codes is proposed. Given an MLBMC C with no interdependency among the binary component codes, the proposed method gives an MLBC C-prime that has the same rate as C, a minimum squared Euclidean distance not less than that of 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. Finally, a technique is presented for analyzing the error performance of MLBMCs for an additive white Gaussian noise channel based on soft-decision maximum-likelihood decoding.
Cervical Laminoplasty for Multilevel Cervical Myelopathy
Sayana, Murali Krishna; Jamil, Hassan; Poynton, Ashley
2011-01-01
Cervical spondylotic myelopathy can result from degenerative cervical spondylosis, herniated disk material, osteophytes, redundant ligamentum flavum, or ossification of the posterior longitudinal ligament. Surgical intervention for multi-level myelopathy aims to decompress the spinal cord and maintain stability of the cervical spine. Laminoplasty was major surgical advancement as laminectomy resulted in kyphosis and unsatisfactory outcomes. Hirabayashi popularised the expansive open door laminoplasty which was later modified several surgeons. Laminoplasty has changed the way surgeons approach multilevel cervical spondylotic myelopathy. PMID:21991408
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
Gu, Fei; Preacher, Kristopher J; Wu, Wei; Yung, Yiu-Fai
2014-01-01
Although the state space approach for estimating multilevel regression models has been well established for decades in the time series literature, it does not receive much attention from educational and psychological researchers. In this article, we (a) introduce the state space approach for estimating multilevel regression models and (b) extend the state space approach for estimating multilevel factor models. A brief outline of the state space formulation is provided and then state space forms for univariate and multivariate multilevel regression models, and a multilevel confirmatory factor model, are illustrated. The utility of the state space approach is demonstrated with either a simulated or real example for each multilevel model. It is concluded that the results from the state space approach are essentially identical to those from specialized multilevel regression modeling and structural equation modeling software. More importantly, the state space approach offers researchers a computationally more efficient alternative to fit multilevel regression models with a large number of Level 1 units within each Level 2 unit or a large number of observations on each subject in a longitudinal study.
Silicon carbide DC-DC multilevel Cuk converter
NASA Astrophysics Data System (ADS)
Almalaq, Yasser; Alateeq, Ayoob; Matin, Mohammad
2016-09-01
In this paper, DC-DC multilevel cuk converter using silicon carbide (SiC) Components is presented. Cuk converter gives output voltage with negative polarity. This topology is useful for applications require high gain with limitation on duty cycle. The gain of the design can be enhanced by increasing the number of multiplier level (N). This relation between the gain and the number of levels is the major advantage of this multilevel cuk converter. In the proposed cuk converter, a single SiC MOSFET, 2N-1 SiC schottky diodes, 2N capacitors, 2 inductors, and single input voltage are used to supply a load with negative polarity. 300V input voltage, 50KHz switching frequency, and 75% duty cycle are the main parameters used in the design. The output parameters are 3KW power and -5.7 KV voltage. Because this design can be used in applications which temperature plays a critical role, the relation between increasing temperature and output voltage and power are tested. The design is simulated using LTspice software and the results are discussed.
Multilevel sequential Monte Carlo samplers
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 h_{L}. 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 levels ${\\infty}$ >h_{0}>h_{1 }...>h_{L}. 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.
Applications of cascade multilevel inverters.
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.
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.
Multilevel sequential Monte Carlo samplers
Beskos, Alexandros; Jasra, Ajay; Law, Kody; ...
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
A Multilevel Approach to Manual Lifting in Manufacturing Industries.
Kayis, Berman; Kothiyal, Kamal
1996-01-01
Musculoskeletal injuries are often the consequences of wrong postural configurations used during Manual Materials Handling (MMH). This eventually leads to a large payout of worker's compensation and loss of production time. A simulated study of back injury risks has been carried out on seven selected manufacturing industries to identify and evaluate harmful working postures. For each MMH task, Ovako Working Posture Analyzing System (OWAS) codes have been identified with the help of motion study pictures. Also, Chaffin's biomechanical model was used to calculate L5/S1 load compression values on the spine during MMH activities. The multilevel approach adopted was a combination of OWAS and Chaffin's biomechanical model. The application of a digitizer enabled us to identify the coordinates and it made a subsequent evaluation of the angles of each body link possible.
A multilevel preconditioner for domain decomposition boundary systems
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.
Multilevel Modeling in Psychosomatic Medicine Research
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
Multilevel modeling in psychosomatic medicine research.
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.
Propensity score weighting with multilevel data.
Li, Fan; Zaslavsky, Alan M; Landrum, Mary Beth
2013-08-30
Propensity score methods are being increasingly used as a less parametric alternative to traditional regression to balance observed differences across groups in both descriptive and causal comparisons. Data collected in many disciplines often have analytically relevant multilevel or clustered structure. The propensity score, however, was developed and has been used primarily with unstructured data. We present and compare several propensity-score-weighted estimators for clustered data, including marginal, cluster-weighted, and doubly robust estimators. Using both analytical derivations and Monte Carlo simulations, we illustrate bias arising when the usual assumptions of propensity score analysis do not hold for multilevel data. We show that exploiting the multilevel structure, either parametrically or nonparametrically, in at least one stage of the propensity score analysis can greatly reduce these biases. We applied these methods to a study of racial disparities in breast cancer screening among beneficiaries of Medicare health plans.
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…
Multilevel transport solution of LWR reactor cores
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.
Overcoming erasure errors with multilevel systems
NASA Astrophysics Data System (ADS)
Muralidharan, Sreraman; Zou, Chang-Ling; Li, Linshu; Wen, Jianming; Jiang, Liang
2017-01-01
We investigate the usage of highly efficient error correcting codes of multilevel systems to protect encoded quantum information from erasure errors and implementation to repetitively correct these errors. Our scheme makes use of quantum polynomial codes to encode quantum information and generalizes teleportation based error correction for multilevel systems to correct photon losses and operation errors in a fault-tolerant manner. We discuss the application of quantum polynomial codes to one-way quantum repeaters. For various types of operation errors, we identify different parameter regions where quantum polynomial codes can achieve a superior performance compared to qubit based quantum parity codes.
1992-01-01
interesting a research issue. An algorithm for this case, using a multiversion technique, will be the subject of future work. In addition, there is a...34 Multiversion Concurrency Control for Multilevel Secure Database Systems" in Proceedings of the IEEE Symposium on Security and Privacy, pp. 369-383...Oakland, CA May 1990. 7. William T. Maimone and Ira B. Greenberg, "Single-Level Multiversion Schedulers for Multilevel Secure Database Systems" in
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…
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…
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.
Differential Item Functioning from a Multilevel Perspective.
ERIC Educational Resources Information Center
van den Bergh, Huub; And Others
The term differential item functioning (DIF) refers to whether or not the same psychological constructs are measured across different groups. If an item does not measure the same skills or subskills in different populations, it is said to function differentially or to display item bias. A multilevel approach to DIF is proposed. In such a model,…
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.
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…
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…
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…
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
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.
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.
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.
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.
Knowledge discovery of multilevel protein motifs
Conklin, D.; Glasgow, J.; Fortier, S.
1994-12-31
A new category of protein motif is introduced. This type of motif captures, in addition to global structure, the nested structure of its component parts. A dataset of four proteins is represented using this scheme. A structured machine discovery procedure is used to discover recurrent amino acid motifs and this knowledge is utilized for the expression of subsequent protein motif discoveries. Examples of discovered multilevel motifs are presented.
Multilevel resistive information storage and retrieval
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.
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.
Multilevel sparse functional principal component analysis.
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.
Computational analyses of multilevel discourse comprehension.
Graesser, Arthur C; McNamara, Danielle S
2011-04-01
The proposed multilevel framework of discourse comprehension includes the surface code, the textbase, the situation model, the genre and rhetorical structure, and the pragmatic communication level. We describe these five levels when comprehension succeeds and also when there are communication misalignments and comprehension breakdowns. A computer tool has been developed, called Coh-Metrix, that scales discourse (oral or print) on dozens of measures associated with the first four discourse levels. The measurement of these levels with an automated tool helps researchers track and better understand multilevel discourse comprehension. Two sets of analyses illustrate the utility of Coh-Metrix in discourse theory and educational practice. First, Coh-Metrix was used to measure the cohesion of the text base and situation model, as well as potential extraneous variables, in a sample of published studies that manipulated text cohesion. This analysis helped us better understand what was precisely manipulated in these studies and the implications for discourse comprehension mechanisms. Second, Coh-Metrix analyses are reported for samples of narrative and science texts in order to advance the argument that traditional text difficulty measures are limited because they fail to accommodate most of the levels of the multilevel discourse comprehension framework.
Addressing Asthma Health Disparities: A Multilevel Challenge
Canino, Glorisa; McQuaid, Elizabeth L.; Rand, Cynthia S.
2009-01-01
Substantial research has documented pervasive disparities in the prevalence, severity, and morbidity of asthma among minority populations compared to non-Latino whites. The underlying causes of these disparities are not well understood, and as a result, the leverage points to address them remain unclear. A multilevel framework for integrating research in asthma health disparities is proposed in order to advance both future research and clinical practice. The components of the proposed model include health care policies and regulations, operation of the health care system, provider/clinician-level factors, social/environmental factors, and individual/family attitudes and behaviors. The body of research suggests that asthma disparities have multiple, complex and inter-related sources. Disparities occur when individual, environmental, health system, and provider factors interact with one another over time. Given that the causes of asthma disparities are complex and multilevel, clinical strategies to address these disparities must therefore be comparably multilevel and target many aspects of asthma care. Clinical Implications: Several strategies that could be applied in clinical settings to reduce asthma disparities are described including the need for routine assessment of the patient’s beliefs, financial barriers to disease management, and health literacy, and the provision of cultural competence training and communication skills to health care provider groups. PMID:19447484
NASA Astrophysics Data System (ADS)
Al-Naseem, Osama Abdulrahman
A novel multilevel matrix converter is developed to efficiently transfer energy between a three-phase variable-speed generator of a wind turbine and a three-phase ac utility network. Optimizing the energy transfer efficiency at light load is critical in variable-speed wind generators. Laboratory experiment suggests that converter efficiency at light load may be increased via soft-switching and multilevel switching techniques. The new converter includes the advantages of multilevel converters, such as reduced harmonic content, increased power handling capability without additional switching loss, and high efficiency at low machine voltages. It also features the characteristics of conventional matrix converters, such as space vector control and improved efficiency via auxiliary resonant commutation soft-switching techniques. Similar to a conventional matrix converter, the novel multilevel matrix converter uses a nine-switch matrix with four-quadrant switches to connect input phases at one side of the converter with output phases at the other side of the converter. However, the switches of the new converter are configured differently from those used in the conventional matrix converter. Each switch of the new converter is a cell that resembles a full-bridge inverter topology and can assume three voltage levels while used. Semiconductor devices in a switch cell are always clamped to a known constant do voltage of a capacitor. This is a typical characteristic of multilevel converters where device voltage stresses are reduced by clamping the main transistor voltages to low levels. With reduced voltage stresses, switching frequency can be increased to allow for reduced size of filter magnetics. Unlike conventional matrix converter, the multilevel matrix converter uses inductors on both input and output sides of the converter. This symmetry allows for both step up and step down operations. Each switch cell features double the power handling capability compared to the four
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…
Consequences of Unmodeled Nonlinear Effects in Multilevel Models
ERIC Educational Resources Information Center
Bauer, Daniel J.; Cai, Li
2009-01-01
Applications of multilevel models have increased markedly during the past decade. In incorporating lower-level predictors into multilevel models, a key interest is often whether or not a given predictor requires a random slope, that is, whether the effect of the predictor varies over upper-level units. If the variance of a random slope…
Minimally invasive treatment of multilevel spinal epidural abscess.
Safavi-Abbasi, Sam; Maurer, Adrian J; Rabb, Craig H
2013-01-01
The use of minimally invasive tubular retractor microsurgery for treatment of multilevel spinal epidural abscess is described. This technique was used in 3 cases, and excellent results were achieved. The authors conclude that multilevel spinal epidural abscesses can be safely and effectively managed using microsurgery via a minimally invasive tubular retractor system.
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…
Multilevel Modeling and School Psychology: A Review and Practical Example
ERIC Educational Resources Information Center
Graves, Scott L., Jr.; Frohwerk, April
2009-01-01
The purpose of this article is to provide an overview of the state of multilevel modeling in the field of school psychology. The authors provide a systematic assessment of published research of multilevel modeling studies in 5 journals devoted to the research and practice of school psychology. In addition, a practical example from the nationally…
Multilevel conductance switching in polymer films
NASA Astrophysics Data System (ADS)
Lauters, M.; McCarthy, B.; Sarid, D.; Jabbour, G. E.
2006-07-01
Multilevel conductance switching in poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) films is demonstrated. A thin-film structure, ITO-coated glass/MEH-PPV/Al, has shown the ability to store a continuum of conductance states. These states are nonvolatile and can be switched reproducibly by applying appropriate programing biases above a certain threshold voltage. The electrical conductivity of the highest and lowest states can differ by five orders of magnitude. Furthermore, these devices exhibit good cyclic switching characteristics and retention times of several weeks.
Multilevel converters -- A new breed of power converters
Lai, J.S.; Peng, F.Z. |
1995-09-01
Multilevel voltage source converters are emerging as a new breed of power converter options for high-power applications. The multilevel voltage source converters typically synthesize the staircase voltage wave from several levels of dc capacitor voltages. One of the major limitations of the multilevel converters is the voltage unbalance between different levels. The techniques to balance the voltage between different levels normally involve voltage clamping or capacitor charge control. There are several ways of implementing voltage balance in multilevel converters. Without considering the traditional magnetic coupled converters, this paper presents three recently developed multilevel voltage source converters: (1) diode-clamp, (2) flying-capacitors, and (3) cascaded-inverters with separate dc sources. The operating principle, features, constraints, and potential applications of these converters will be discussed.
Multilevel Charge Storage in a Multiple Alloy Nanodot Memory
NASA Astrophysics Data System (ADS)
Lee, Gae-Hun; Lee, Jung-Min; Heub Song, Yun; Bea, Ji Chel; Tanaka, Tetsu; Koyanagi, Mitsumasa
2011-09-01
A multilevel charge storage in a multiple FePt alloy nanodot memory is investigated for the first time. It is demonstrated that the memory structure with multiple FePt nanodot layers effectively realizes a multilevel state by the adjustment of gate voltage. Metal oxide semiconductor (MOS) capacitors with four FePt nanodot layers as a floating gate are fabricated to evaluate the multilevel cell characteristic and reliability. Here, the effect of memory window for a nanodot diameter is also investigated, and it is found that a smaller dot size gives a larger window. From the results showing good endurance and retention characteristics for the multilevel states, it is expected that a multiple FePt nanodot memory using Fowler-Nordheim (FN) tunneling can be a candidate structure for the future multilevel NAND flash memory.
Multilevel cervical arthroplasty: current evidence. A systematic review.
Joaquim, Andrei F; Riew, K Daniel
2017-02-01
OBJECTIVE Cervical disc arthroplasty (CDA) has been demonstrated to be an effective treatment modality for single-level cervical radiculopathy or myelopathy. Its advantages over an anterior cervical discectomy and fusion (ACDF) include motion preservation and decreased reoperations at the index and adjacent segments up to 7 years postoperatively. Considering the fact that many patients have multilevel cervical disc degeneration (CDD), the authors performed a systematic review of the clinical studies evaluating patients who underwent multilevel CDA (2 or more levels). METHODS A systematic review in the MEDLINE database was performed. Clinical studies including patients who had multilevel CDA were selected and included. Case reports and literature reviews were excluded. Articles were then grouped according to their main study objective: 1) studies comparing multilevel CDA versus ACDF; 2) studies comparing single-level CDA versus multilevel CDA; and 3) multilevel CDA after a previous cervical spine surgery. RESULTS Fourteen articles met all inclusion criteria. The general conclusions were that multilevel CDA was at least as safe and effective as ACDF, with preservation of cervical motion when compared with ACDF and potentially with fewer reoperations expected in most of the studies. Multilevel CDAs are clinically effective as single-level surgeries, with good clinical and radiological outcomes. Some studies reported a higher incidence of heterotopic ossification in multilevel CDA when compared with single-level procedures, but without clinical relevance during the follow-up period. A CDA may be indicated even after a previous cervical surgery in selected cases. CONCLUSIONS The current literature supports the use of multilevel CDA. Caution is necessary regarding the more restrictive indications for CDA when compared with ACDF. Further prospective, controlled, multicenter, and randomized studies not sponsored by the device manufactures are desirable to prove the
Multilevel converters for large electric drives
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.
Advanced micromechanisms in a multilevel polysilicon technology
NASA Astrophysics Data System (ADS)
Rodgers, M. Steven; Sniegowski, Jeffry J.; Miller, Samuel L.; Craig Barron, Carole; McWhorter, Paul J.
1997-09-01
Quad-level polysilicon surface micromachining technology, comprising three mechanical levels plus an electrical interconnect layer, is giving rise to a new generation of micro-electromechanical devices and assemblies. Enhanced components can now be produced through greater flexibility in fabrication and design. New levels of design complexity that include multi-level gears, single-attempt locks, and optical elements have recently been realized. Extensive utilization of the fourth layer of polysilicon differentiates these latter generation devices from their predecessors. This level of poly enables the fabrication of pin joints, linkage arms, hinges on moveable plates, and multi-level gear assemblies. The mechanical design aspects of these latest micromachines will be discussed with particular emphasis on a number of design modifications that improve the power, reliability, and smoothness of operation of the microengine. The microengine is the primary actuation mechanism that is being used to drive mirrors out of plane and rotate 1600-micrometers diameter gears. Also discussed is our most advanced micromechanical system to date, a complex proof-of-concept batch-fabricated assembly that, upon transmitting the proper electrical code to a mechanical lock, permits the operation of a micro-optical shutter.
The treatment for multilevel noncontiguous spinal fractures
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
Fault diagnosis method based on FFT-RPCA-SVM for Cascaded-Multilevel Inverter.
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.
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.
Design of a multilevel Active Power Filter for More Electrical Airplane variable frequency systems
NASA Astrophysics Data System (ADS)
Guerreiro, Joel Filipe; Pomilio, Jose Antenor; Busarello, Tiago Davi Curi
This paper presents the design and simulation of an Aeronautical Active Power Filter (AAPF) for a Variable Speed Variable Frequency (VSVF) advanced aircraft electric power system. The purposes of the AAPF are to mitigate current harmonics, to improve the source power factor and to mitigate the effects of unbalanced loads. Regarding the fact that the Aircraft Electrical Power System (AEPS) frequency may vary between 360 Hz and 900 Hz, and the load dynamics is often modified, an enhanced filtering technique is required. The designed AAPF topology is an asymmetrical multilevel inverter (AMI), which control strategy is based on the Conservative Power Theory (CPT) and synchronized by a Kalman Filter Phase-Locked Loop (KF-PLL). The above configuration renders the AAPF very robust and effective to its purpose. Accurate simulation results on Matlab/Simulink platform verify the feasibility of the proposed AAPF and the high performance of the control strategy during steady-state and dynamic operations.
[Applying multilevel models in evaluation of bioequivalence (I)].
Liu, Qiao-lan; Shen, Zhuo-zhi; Chen, Feng; Li, Xiao-song; Yang, Min
2009-12-01
This study aims to explore the application value of multilevel models for bioequivalence evaluation. Using a real example of 2 x 4 cross-over experimental design in evaluating bioequivalence of antihypertensive drug, this paper explores complex variance components corresponding to criteria statistics in existing methods recommended by FDA but obtained in multilevel models analysis. Results are compared with those from FDA standard Method of Moments, specifically on the feasibility and applicability of multilevel models in directly assessing the bioequivalence (ABE), the population bioequivalence (PBE) and the individual bioequivalence (IBE). When measuring ln (AUC), results from all variance components of the test and reference groups such as total variance (sigma(TT)(2) and sigma(TR)(2)), between-subject variance (sigma(BT)(2) and sigma(BR)(2)) and within-subject variance (sigma(WT)(2) and sigma(WR)(2)) estimated by simple 2-level models are very close to those that using the FDA Method of Moments. In practice, bioequivalence evaluation can be carried out directly by multilevel models, or by FDA criteria, based on variance components estimated from multilevel models. Both approaches produce consistent results. Multilevel models can be used to evaluate bioequivalence in cross-over test design. Compared to FDA methods, this one is more flexible in decomposing total variance into sub components in order to evaluate the ABE, PBE and IBE. Multilevel model provides a new way into the practice of bioequivalence evaluation.
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.
Cantilevered multilevel LIGA devices and methods
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.
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.
Multilevel architectures for electronic document retrieval
Rome, J.A.; Tolliver, J.S.
1997-04-01
Traditionally, most classified computer systems run at the highest level of any of the data on the system, and all users must be cleared to this security level. This architecture precludes the use of low-level (pay and clearance) personnel for such tasks as data entry, and makes sharing data with other entities difficult. The government is trying to solve this problem by the introduction of multilevel-secure (MLS) computer systems. In addition, wherever possible, there is pressure to use commercial off-the-shelf software (COTS) to improve reliability, and to reduce purchase and maintenance costs. This paper presents two architectures for an MLS electronic document retrieval system using COTS products. Although the authors believe that the resulting systems represent a real advance in usability, scaleability, and scope, the disconnect between existing security rules and regulations and the rapidly-changing state of technology will make accreditation of such systems a challenge.
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.
Multilevel wireless capsule endoscopy video segmentation
NASA Astrophysics Data System (ADS)
Hwang, Sae; Celebi, M. Emre
2010-03-01
Wireless Capsule Endoscopy (WCE) is a relatively new technology (FDA approved in 2002) allowing doctors to view most of the small intestine. WCE transmits more than 50,000 video frames per examination and the visual inspection of the resulting video is a highly time-consuming task even for the experienced gastroenterologist. Typically, a medical clinician spends one or two hours to analyze a WCE video. To reduce the assessment time, it is critical to develop a technique to automatically discriminate digestive organs and shots each of which consists of the same or similar shots. In this paper a multi-level WCE video segmentation methodology is presented to reduce the examination time.
Multi-level coupled cluster theory
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.
Multilevel domain decomposition for electronic structure calculations
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.
Evolutionary biosemiotics and multilevel construction networks.
Sharov, Alexei A
2016-12-01
In contrast to the traditional relational semiotics, biosemiotics decisively deviates towards dynamical aspects of signs at the evolutionary and developmental time scales. The analysis of sign dynamics requires constructivism (in a broad sense) to explain how new components such as subagents, sensors, effectors, and interpretation networks are produced by developing and evolving organisms. Semiotic networks that include signs, tools, and subagents are multilevel, and this feature supports the plasticity, robustness, and evolvability of organisms. The origin of life is described here as the emergence of simple self-constructing semiotic networks that progressively increased the diversity of their components and relations. Primitive organisms have no capacity to classify and track objects; thus, we need to admit the existence of proto-signs that directly regulate activities of agents without being associated with objects. However, object recognition and handling became possible in eukaryotic species with the development of extensive rewritable epigenetic memory as well as sensorial and effector capacities. Semiotic networks are based on sequential and recursive construction, where each step produces components (i.e., agents, scaffolds, signs, and resources) that are needed for the following steps of construction. Construction is not limited to repair and reproduction of what already exists or is unambiguously encoded, it also includes production of new components and behaviors via learning and evolution. A special case is the emergence of new levels of organization known as metasystem transition. Multilevel semiotic networks reshape the phenotype of organisms by combining a mosaic of features developed via learning and evolution of cooperating and/or conflicting subagents.
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.
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.
Analysis of a transformer-less, multi-level DC-DC converter for HVDC operation
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.
In situ multi-level analysis of viscoelastic deformation mechanisms in tendon collagen.
Gupta, H S; Seto, J; Krauss, S; Boesecke, P; Screen, H R C
2010-02-01
Tendon is a hydrated multi-level fibre composite, in which time-dependent behaviour is well established. Studies indicate significant stress relaxation, considered important for optimising tissue stiffness. However, whilst this behaviour is well documented, the mechanisms associated with the response are largely unknown. This study investigates the sub-structural mechanisms occurring during stress relaxation at both the macro (fibre) and nano (fibril) levels of the tendon hierarchy. Stress relaxation followed a two-stage exponential behaviour, during which structural changes were visible at the fibre and fibril levels. Fibril relaxation and fibre sliding showed a double exponential response, while fibre sliding was clearly the largest contributor to relaxation. The amount of stress relaxation and sub-structural reorganisation increased with increasing load increments, but fibre sliding was consistently the largest contributor to stress relaxation. A simple model of tendon viscoelasticity at the fibril and fibre levels has been developed, capturing this behaviour by serially coupling a Voigt element (collagen fibril), with two Maxwell elements (non-collagenous matrix between fibrils and fibres). This multi-level analysis provides a first step towards understanding how sub-structural interactions contribute to viscoelastic behaviour. It indicates that nano- and micro-scale shearing are significant dissipative mechanisms, and the kinetics of relaxation follows a two-stage exponential decay, well fitted by serially coupled viscoelastic elements.
The genetical theory of multilevel selection
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
Multilevel Radiative Transfer with Partial Frequency Redistribution
NASA Astrophysics Data System (ADS)
Uitenbroek, H.
2001-08-01
A multilevel accelerated lambda iteration (MALI) method for radiative transfer calculations with partial frequency redistribution (PRD) is presented. The method, which is based on Rybicki & Hummer's complete frequency redistribution (CRD) formalism with full preconditioning, consistently accounts for overlapping radiative transitions. Its extension to PRD is implemented in a very natural way through the use of the Ψ operator operating on the emissivity rather than the commonly used Λ operator, which operates on the source function. Apart from requiring an additional inner computational loop to evaluate the PRD emission-line profiles with fixed population numbers, implementation of the presented method requires only a trivial addition of computer code. Since the presented method employs a diagonal operator, it is easily extended to different geometries. Currently, it has been implemented for one-, two-, and three-dimensional Cartesian grids and spherical symmetry. In all cases, the speed of convergence with PRD is very similar to that in CRD, with the former sometimes even surpassing the latter. Sample calculations exhibiting the favorable convergence behavior of the PRD code are presented in the case of the Ca II H and K lines, the Mg II h and k lines, and the hydrogen Lyα and Lyβ lines in a one-dimensional solar model and the Ca II resonance lines in a two-dimensional flux-sheet model.
Multilevel Monte Carlo simulation of Coulomb collisions
Rosin, M.S.; Ricketson, L.F.; Dimits, A.M.; Caflisch, R.E.; Cohen, B.I.
2014-10-01
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{sup −2}) or O(ε{sup −2}(lnε){sup 2}), depending on the underlying discretization, Milstein or Euler–Maruyama respectively. This is to be contrasted with a cost of O(ε{sup −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{sup −5}. We discuss the importance of the method for problems in which collisions constitute the computational rate limiting step, and its limitations.
Learning Stable Multilevel Dictionaries for Sparse Representations.
Thiagarajan, Jayaraman J; Ramamurthy, Karthikeyan Natesan; Spanias, Andreas
2015-09-01
Sparse representations using learned dictionaries are being increasingly used with success in several data processing and machine learning applications. The increasing need for learning sparse models in large-scale applications motivates the development of efficient, robust, and provably good dictionary learning algorithms. Algorithmic stability and generalizability are desirable characteristics for dictionary learning algorithms that aim to build global dictionaries, which can efficiently model any test data similar to the training samples. In this paper, we propose an algorithm to learn dictionaries for sparse representations from large scale data, and prove that the proposed learning algorithm is stable and generalizable asymptotically. The algorithm employs a 1-D subspace clustering procedure, the K-hyperline clustering, to learn a hierarchical dictionary with multiple levels. We also propose an information-theoretic scheme to estimate the number of atoms needed in each level of learning and develop an ensemble approach to learn robust dictionaries. Using the proposed dictionaries, the sparse code for novel test data can be computed using a low-complexity pursuit procedure. We demonstrate the stability and generalization characteristics of the proposed algorithm using simulations. We also evaluate the utility of the multilevel dictionaries in compressed recovery and subspace learning applications.
Dendritic growth model of multilevel marketing
NASA Astrophysics Data System (ADS)
Pang, James Christopher S.; Monterola, Christopher P.
2017-02-01
Biologically inspired dendritic network growth is utilized to model the evolving connections of a multilevel marketing (MLM) enterprise. Starting from agents at random spatial locations, a network is formed by minimizing a distance cost function controlled by a parameter, termed the balancing factor bf, that weighs the wiring and the path length costs of connection. The paradigm is compared to an actual MLM membership data and is shown to be successful in statistically capturing the membership distribution, better than the previously reported agent based preferential attachment or analytic branching process models. Moreover, it recovers the known empirical statistics of previously studied MLM, specifically: (i) a membership distribution characterized by the existence of peak levels indicating limited growth, and (ii) an income distribution obeying the 80 - 20 Pareto principle. Extensive types of income distributions from uniform to Pareto to a "winner-take-all" kind are also modeled by varying bf. Finally, the robustness of our dendritic growth paradigm to random agent removals is explored and its implications to MLM income distributions are discussed.
Visual attention as a multilevel selection process.
Kastner, Sabine; Pinsk, Mark A
2004-12-01
Natural visual scenes are cluttered and contain many different objects that cannot all be processed simultaneously. Therefore, attentional mechanisms are needed to select relevant and to filter out irrelevant information. Evidence from functional brain imaging reveals that attention operates at various processing levels within the visual system and beyond. First, the lateral geniculate nucleus appears to be the first stage in the processing of visual information that is modulated by attention, consistent with the idea that it may play an important role as an early gatekeeper in controlling neural gain. Second, areas at intermediate cortical-processing levels, such as V4 and TEO, appear to be important sites at which attention filters out unwanted information by means of receptive field mechanisms. Third, the attention mechanisms that operate in the visual system appear to be controlled by a distributed network of higher order areas in the frontal and parietal cortex, which generate top-down signals that are transmitted via feedback connections to the visual system. And fourth, the pulvinar of the thalamus may operate by integrating and coordinating attentional functions in concert with the fronto-parietal network, although much needs to be learned about its functional properties. The overall view that emerges from the studies reviewed in this article is that neural mechanisms of selective attention operate at multiple stages in the visual system and beyond and are determined by the visual processing capabilities of each stage. In this respect, attention can be considered in terms of a multilevel selection process.
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.
Multilevel Monte Carlo simulation of Coulomb collisions
Rosin, M. S.; Ricketson, L. F.; Dimits, A. M.; ...
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
Multilevel Monte Carlo simulation of Coulomb collisions
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.
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.
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.
[Application of multilevel models in the evaluation of bioequivalence (II).].
Liu, Qiao-lan; Shen, Zhuo-zhi; Li, Xiao-song; Chen, Feng; Yang, Min
2010-03-01
The main purpose of this paper is to explore the applicability of multivariate multilevel models for bioequivalence evaluation. Using an example of a 4 x 4 cross-over test design in evaluating bioequivalence of homemade and imported rosiglitazone maleate tablets, this paper illustrated the multivariate-model-based method for partitioning total variances of ln(AUC) and ln(C(max)) in the framework of multilevel models. It examined the feasibility of multivariate multilevel models in directly evaluating average bioequivalence (ABE), population bioequivalence (PBE) and individual bioequivalence (IBE). Taking into account the correlation between ln(AUC) and ln(C(max)) of rosiglitazone maleate tablets, the proposed models suggested no statistical difference between the two effect measures in their ABE bioequivalence via joint tests, whilst a contradictive conclusion was derived based on univariate multilevel models. Furthermore, the PBE and IBE for both ln(AUC) and ln(C(max)) of the two types of tablets were assessed with no statistical difference based on estimates of variance components from the proposed models. Multivariate multilevel models could be used to analyze bioequivalence of multiple effect measures simultaneously and they provided a new way of statistical analysis to evaluate bioequivalence.
Hybrid renewable energy system using doubly-fed induction generator and multilevel inverter
NASA Astrophysics Data System (ADS)
Ahmed, Eshita
The proposed hybrid system generates AC power by combining solar and wind energy converted by a doubly-fed induction generator (DFIG). The DFIG, driven by a wind turbine, needs rotor excitation so the stator can supply a load or the grid. In a variable-speed wind energy system, the stator voltage and its frequency vary with wind speed, and in order to keep them constant, variable-voltage and variable-frequency rotor excitation is to be provided. A power conversion unit supplies the rotor, drawing power either from AC mains or from a PV panel depending on their availability. It consists of a multilevel inverter which gives lower harmonic distortion in the stator voltage. Maximum power point tracking techniques have been implemented for both wind and solar power. The complete hybrid renewable energy system is implemented in a PSIM-Simulink interface and the wind energy conversion portion is realized in hardware using dSPACE controller board.
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.
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.
On the thermodynamics of multilevel evolution.
Tessera, Marc; Hoelzer, Guy A
2013-09-01
Biodiversity is hierarchically structured both phylogenetically and functionally. Phylogenetic hierarchy is understood as a product of branching organic evolution as described by Darwin. Ecosystem biologists understand some aspects of functional hierarchy, such as food web architecture, as a product of evolutionary ecology; but functional hierarchy extends to much lower scales of organization than those studied by ecologists. We argue that the more general use of the term "evolution" employed by physicists and applied to non-living systems connects directly to the narrow biological meaning. Physical evolution is best understood as a thermodynamic phenomenon, and this perspective comfortably includes all of biological evolution. We suggest four dynamical factors that build on each other in a hierarchical fashion and set the stage for the Darwinian evolution of biological systems: (1) the entropic erosion of structure; (2) the construction of dissipative systems; (3) the reproduction of growing systems and (4) the historical memory accrued to populations of reproductive agents by the acquisition of hereditary mechanisms. A particular level of evolution can underpin the emergence of higher levels, but evolutionary processes persist at each level in the hierarchy. We also argue that particular evolutionary processes can occur at any level of the hierarchy where they are not obstructed by material constraints. This theoretical framework provides an extensive basis for understanding natural selection as a multilevel process. The extensive literature on thermodynamics in turn provides an important advantage to this perspective on the evolution of higher levels of organization, such as the evolution of altruism that can accompany the emergence of social organization.
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…
Parametric Multi-Level Tiling of Imperfectly Nested Loops
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.
Multilevel model reduction for uncertainty quantification in computational structural dynamics
NASA Astrophysics Data System (ADS)
Ezvan, O.; Batou, A.; Soize, C.; Gagliardini, L.
2017-02-01
This work deals with an extension of the reducedorder models (ROMs) that are classically constructed by modal analysis in linear structural dynamics for which the computational models are assumed to be uncertain. It is based on a multilevel projection strategy consisting in introducing three reduced-order bases that are obtained by using a spatial filtering methodology of local displacements. This filtering involves global shape functions for the kinetic energy. The proposed multilevel stochastic ROM is constructed by using the nonparametric probabilistic approach of uncertainties. It allows for affecting a specific level of uncertainties to each type of displacements associated with the corresponding vibration regime. The proposed methodology is applied to the computational model of an automobile structure, for which the multilevel stochastic ROM is identified with respect to experimental measurements. This identification is performed by solving a statistical inverse problem.
Health reforms as examples of multilevel interventions in cancer care.
Flood, Ann B; Fennell, Mary L; Devers, Kelly J
2012-05-01
To increase access and improve system quality and efficiency, President Obama signed the Patient Protection and Affordable Care Act with sweeping changes to the nation's health-care system. Although not intended to be specific to cancer, the act's implementation will profoundly impact cancer care. Its components will influence multiple levels of the health-care environment including states, communities, health-care organizations, and individuals seeking care. To illustrate these influences, two reforms are considered: 1) accountable care organizations and 2) insurance-based reforms to gather evidence about effectiveness. We discuss these reforms using three facets of multilevel interventions: 1) their intended and unintended consequences, 2) the importance of timing, and 3) their implications for cancer. The success of complex health reforms requires understanding the scientific basis and evidence for carrying out such multilevel interventions. Conversely and equally important, successful implementation of multilevel interventions depends on understanding the political setting and goals of health-care reform.
A general non-linear multilevel structural equation mixture model
Kelava, Augustin; Brandt, Holger
2014-01-01
In the past 2 decades latent variable modeling has become a standard tool in the social sciences. In the same time period, traditional linear structural equation models have been extended to include non-linear interaction and quadratic effects (e.g., Klein and Moosbrugger, 2000), and multilevel modeling (Rabe-Hesketh et al., 2004). We present a general non-linear multilevel structural equation mixture model (GNM-SEMM) that combines recent semiparametric non-linear structural equation models (Kelava and Nagengast, 2012; Kelava et al., 2014) with multilevel structural equation mixture models (Muthén and Asparouhov, 2009) for clustered and non-normally distributed data. The proposed approach allows for semiparametric relationships at the within and at the between levels. We present examples from the educational science to illustrate different submodels from the general framework. PMID:25101022
A multilevel memetic algorithm for large SAT-encoded problems.
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.
Health Reforms as Examples of Multilevel Interventions in Cancer Care
Fennell, Mary L.; Devers, Kelly J.
2012-01-01
To increase access and improve system quality and efficiency, President Obama signed the Patient Protection and Affordable Care Act with sweeping changes to the nation’s health-care system. Although not intended to be specific to cancer, the act's implementation will profoundly impact cancer care. Its components will influence multiple levels of the health-care environment including states, communities, health-care organizations, and individuals seeking care. To illustrate these influences, two reforms are considered: 1) accountable care organizations and 2) insurance-based reforms to gather evidence about effectiveness. We discuss these reforms using three facets of multilevel interventions: 1) their intended and unintended consequences, 2) the importance of timing, and 3) their implications for cancer. The success of complex health reforms requires understanding the scientific basis and evidence for carrying out such multilevel interventions. Conversely and equally important, successful implementation of multilevel interventions depends on understanding the political setting and goals of health-care reform. PMID:22623600
Multilevel animal societies can emerge from cultural transmission.
Cantor, Maurício; Shoemaker, Lauren G; Cabral, Reniel B; Flores, César O; Varga, Melinda; Whitehead, Hal
2015-09-08
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.
Multilevel animal societies can emerge from cultural transmission
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
Dynamic load balancing data centric storage for wireless sensor networks.
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.
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…
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…
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.
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.)
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)
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…
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…
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…
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,…
A Multilevel Mixture IRT Model with an Application to DIF
ERIC Educational Resources Information Center
Cho, Sun-Joo; Cohen, Allan S.
2010-01-01
Mixture item response theory models have been suggested as a potentially useful methodology for identifying latent groups formed along secondary, possibly nuisance dimensions. In this article, we describe a multilevel mixture item response theory (IRT) model (MMixIRTM) that allows for the possibility that this nuisance dimensionality may function…
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…
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,…
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…
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…
A multilevel optical element based on the Fizeau multibeam interferometer
NASA Astrophysics Data System (ADS)
Zhmud', A. A.
1990-10-01
A new multilevel optical element is proposed which is based on the Fizeau multibeam interferometer and a single-frequency wavelength-tunable semiconductor injection lazer. Possible applications of the optical element in optical data processors are discussed. As an example, a high-speed 17-bit analog-digital converter based on this element is considered.
Multilevel IRT Using Dichotomous and Polytomous Response Data. Research Report.
ERIC Educational Resources Information Center
Fox, Jean-Paul
A structural multilevel model is presented in which some of the variables cannot be observed directly but are measured using tests or questionnaires. Observed dichotomous or ordinal politicos response data serve to measure the latent variables using an item response theory model. The latent variables can be defined at any level of the multilevel…
Using multilevel models to quantify heterogeneity in resource selection
Wagner, T.; Diefenbach, D.R.; Christensen, S.A.; Norton, A.S.
2011-01-01
Models of resource selection are being used increasingly to predict or model the effects of management actions rather than simply quantifying habitat selection. Multilevel, or hierarchical, models are an increasingly popular method to analyze animal resource selection because they impose a relatively weak stochastic constraint to model heterogeneity in habitat use and also account for unequal sample sizes among individuals. However, few studies have used multilevel models to model coefficients as a function of predictors that may influence habitat use at different scales or quantify differences in resource selection among groups. We used an example with white-tailed deer (Odocoileus virginianus) to illustrate how to model resource use as a function of distance to road that varies among deer by road density at the home range scale. We found that deer avoidance of roads decreased as road density increased. Also, we used multilevel models with sika deer (Cervus nippon) and white-tailed deer to examine whether resource selection differed between species. We failed to detect differences in resource use between these two species and showed how information-theoretic and graphical measures can be used to assess how resource use may have differed. Multilevel models can improve our understanding of how resource selection varies among individuals and provides an objective, quantifiable approach to assess differences or changes in resource selection. ?? The Wildlife Society, 2011.
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…
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…
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…
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…
A Multilevel Factor Analysis of Students' Evaluations of Teaching
ERIC Educational Resources Information Center
Toland, Michael D.; De Ayala, R. J.
2005-01-01
This study examined the factorial validity of scores on the newly developed Students' Evaluation of Teaching Effectiveness Rating Scale (SETERS) through a series of confirmatory and multilevel structures. Conventional confirmatory factor analyses using the total covariance and pooled within-covariance matrices from two midwestern universities…
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…
Multilevel Models in Family Research: Some Conceptual and Methodological Issues.
ERIC Educational Resources Information Center
Teachman, Jay; Crowder, Kyle
2002-01-01
Article introduces this journal's themes that are used to discuss issues surrounding analysis of multilevel data. It cites Butler's work on whether the effect of welfare benefits on premarital childbearing varies by context, Hoffman's work on the effect of context on adolescent drug use, and Simons' research on how the relationship between…
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.
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…
Transforming SIBTEST to Account for Multilevel Data Structures
ERIC Educational Resources Information Center
French, Brian F.; Finch, W. Holmes
2015-01-01
SIBTEST is a differential item functioning (DIF) detection method that is accurate and effective with small samples, in the presence of group mean differences, and for assessment of both uniform and nonuniform DIF. The presence of multilevel data with DIF detection has received increased attention. Ignoring such structure can inflate Type I error.…
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…
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…
Teaching Strategies for Multilevel ESL Classes. Facilitator's Guide.
ERIC Educational Resources Information Center
Berry, Eve; Williams, Molly
A guide for teacher strategies in multilevel English-as-a-Second Language classes, developed at Clackamas Community College, Oregon, is presented. It contains the following materials: time schedule for a one-day workshop; facilitator's annotated agenda; five transparencies, including teaching objectives and sample lesson plans; various handouts,…
Daily Stressors in School-Age Children: A Multilevel Approach
ERIC Educational Resources Information Center
Escobar, Milagros; Alarcón, Rafael; Blanca, María J.; Fernández-Baena, F. Javier; Rosel, Jesús F.; Trianes, María Victoria
2013-01-01
This study uses hierarchical or multilevel modeling to identify variables that contribute to daily stressors in a population of schoolchildren. Four hierarchical levels with several predictive variables were considered: student (age, sex, social adaptation of the student, number of life events and chronic stressors experienced, and educational…
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…
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…
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…
Strengthening Multisite Educational Interventions: An Illustration with Multilevel Modeling.
ERIC Educational Resources Information Center
Pituch, Keenan A.; Miller, John W.
1999-01-01
Uses data from an evaluation of an alternative teacher certification program to illustrate the value and use of multilevel models to examine site-to-site outcome differences data from multisite evaluations, showing how a traditional analysis approach can overlook effective interventions and miss important links between program implementation and…
Bijma, P; Wade, M J
2008-09-01
Kin and levels-of-selection models are common approaches for modelling social evolution. Indirect genetic effect (IGE) models represent a different approach, specifying social effects on trait values rather than fitness. We investigate the joint effect of relatedness, multilevel selection and IGEs on response to selection. We present a measure for the degree of multilevel selection, which is the natural partner of relatedness in expressions for response. Response depends on both relatedness and the degree of multilevel selection, rather than only one or the other factor. Moreover, response is symmetric in relatedness and the degree of multilevel selection, indicating that both factors have exactly the same effect. Without IGEs, the key parameter is the product of relatedness and the degree of multilevel selection. With IGEs, however, multilevel selection without relatedness can explain evolution of social traits. Thus, next to relatedness and multilevel selection, IGEs are a key element in the genetical theory of social evolution.
Detailed Modeling, Design, and Evaluation of a Scalable Multi-level Checkpointing System
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.
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
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
Multi-level Hybrid Cache: Impact and Feasibility
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.
Multilevel Research and the Challenges of Implementing Genomic Medicine
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
Multilevel data storage in multilayer phase change material
NASA Astrophysics Data System (ADS)
Lu, Yegang; Wang, Miao; Song, Sannian; Xia, Mengjiao; Jia, Yu; shen, Xiang; Wang, Guoxiang; Dai, Shixun; Song, Zhitang
2016-10-01
Superlattice-like GaSb/Sb4Te phase change film was proposed for multilevel phase change memory with the feature of three stable resistance states. Two distinct transition temperatures of around 170 and 230 °C were observed in the superlattice-like GaSb/Sb4Te thin film. Under elevated temperature, the precipitated rhombohedral Sb phase was found in the Sb4Te layer, which was followed by the crystallization of rhombohedral Sb2Te3, whereas the GaSb layer remained almost in the amorphous state except the impinged Sb grains. The formation of percolation path for crystallization in the GaSb layer can account for the multilevel resistance states. For the GaSb/Sb4Te-based device, the reversibly electrical switching was realized under the electrical pulse as short as 10 ns, and the endurance was achieved at least 105 cycles among different resistance states.
Using a Dyadic Logistic Multilevel Model to Analyze Couple Data
Preciado, Mariana A.; Krull, Jennifer L.; Hicks, Andrew
2015-01-01
There is growing recognition within the sexual and reproductive health field of the importance of incorporating both partners’ perspectives when examining sexual and reproductive health behaviors. Yet, the analytical approaches to address couple data have not been readily integrated and utilized within the demographic and public health literature. This paper seeks to provide readers unfamiliar with analytical approaches to couple data an applied example of the use of dyadic logistic multilevel modeling, a useful approach to analyzing couple data to assess the individual, partner, and couple characteristics that are related to individuals’ reproductively relevant beliefs, attitudes, and behaviors. The use of multilevel models in reproductive health research can help researchers develop a more comprehensive picture of the way in which individuals’ reproductive health outcomes are situated in a larger relationship and cultural context. PMID:26363432
Using a dyadic logistic multilevel model to analyze couple data.
Preciado, Mariana A; Krull, Jennifer L; Hicks, Andrew; Gipson, Jessica D
2016-02-01
There is growing recognition within the sexual and reproductive health field of the importance of incorporating both partners' perspectives when examining sexual and reproductive health behaviors. Yet, the analytical approaches to address couple data have not been readily integrated and utilized within the demographic and public health literature. This paper seeks to provide readers unfamiliar with analytical approaches to couple data an applied example of the use of dyadic logistic multilevel modeling, a useful approach to analyzing couple data to assess the individual, partner and couple characteristics that are related to individuals' reproductively relevant beliefs, attitudes and behaviors. The use of multilevel models in reproductive health research can help researchers develop a more comprehensive picture of the way in which individuals' reproductive health outcomes are situated in a larger relationship and cultural context.
Multilevel modeling: overview and applications to research in counseling psychology.
Kahn, Jeffrey H
2011-04-01
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 of counseling psychology journals have had only limited exposure to MLM concepts. This paper provides an overview of MLM that blends mathematical concepts with examples drawn from counseling psychology. This tutorial is intended to be a first step in learning about MLM; readers are referred to other sources for more advanced explorations of MLM. In addition to being a tutorial for understanding and perhaps even conducting MLM analyses, this paper reviews recent research in counseling psychology that has adopted a multilevel framework, and it provides ideas for MLM approaches to future research in counseling psychology.
TopoLayout: multilevel graph layout by topological features.
Archambault, Daniel; Munzner, Tamara; Auber, David
2007-01-01
We describe TopoLayout, a feature-based, multilevel algorithm that draws undirected graphs based on the topological features they contain. Topological features are detected recursively inside the graph, and their subgraphs are collapsed into single nodes, forming a graph hierarchy. Each feature is drawn with an algorithm tuned for its topology. As would be expected from a feature-based approach, the runtime and visual quality of TopoLayout depends on the number and types of topological features present in the graph. We show experimental results comparing speed and visual quality for TopoLayout against four other multilevel algorithms on a variety of data sets with a range of connectivities and sizes. TopoLayout frequently improves the results in terms of speed and visual quality on these data sets.
Weighted adaptively grouped multilevel space time trellis codes
NASA Astrophysics Data System (ADS)
Jain, Dharmvir; Sharma, Sanjay
2015-05-01
In existing grouped multilevel space-time trellis codes (GMLSTTCs), the groups of transmit antennas are predefined, and the transmit power is equally distributed across all transmit antennas. When the channel parameters are perfectly known at the transmitter, adaptive antenna grouping and beamforming scheme can achieve the better performance by optimum grouping of transmit antennas and properly weighting transmitted signals based on the available channel information. In this paper, we present a new code designed by combining GMLSTTCs, adaptive antenna grouping and beamforming using the channel state information at transmitter (CSIT), henceforth referred to as weighted adaptively grouped multilevel space time trellis codes (WAGMLSTTCs). The CSIT is used to adaptively group the transmitting antennas and provide a beamforming scheme by allocating the different powers to the transmit antennas. Simulation results show that WAGMLSTTCs provide improvement in error performance of 2.6 dB over GMLSTTCs.
Multilevel conductance switching of memory device through photoelectric effect.
Ye, Changqing; Peng, Qian; Li, Mingzhu; Luo, Jia; Tang, Zhengming; Pei, Jian; Chen, Jianming; Shuai, Zhigang; Jiang, Lei; Song, Yanlin
2012-12-12
A photoelectronic switch of a multilevel memory device has been achieved using a meta-conjugated donor-bridge-acceptor (DBA) molecule. Such a DBA optoelectronic molecule responds to both the optical and electrical stimuli. The device exhibits good electrical bistable switching behaviors under dark, with a large ON/OFF ratio more than 10(6). In cooperation with the UV light, photoelectronic ternary states are addressable in a bistable switching system. On the basis of the CV measurement, charge carriers transport modeling, quantum chemical calculation, and absorption spectra analysis, the mechanism of the DBA memory is suggested to be attributed to the substep charge transfer transition process. The capability of tailoring photoelectrical properties is a very promising strategy to explore the multilevel storage, and it will give a new opportunity for designing multifunctional devices.
On the multi-level solution algorithm for Markov chains
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.
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.
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.
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.
Survey of Collaboration Technologies in Multi-level Security Environments
2014-04-28
Dickson. 1996. "Teams in Organizations: Recent Research on Performance and Effectiveness". Annual Review of Psychology , 47:307-338. [32] Hall, D.L... Psychology , 94, 2, 535-546. [48] Moore, J.A. (2002). JView: an information visualization paradigm. Proc. SPIE, Vol. 4716, 367-374. In Enabling...date. Multilevel security solutions like the Multi-Layer Access Solution were developed by Gestalt and MAXIM Systems before these companies became
Multilevel programmable logic array schemes for microprogrammed automata
Barkalov, A.A.
1995-03-01
Programmable logic arrays (PLAs) provide an efficient tool for implementation of logic schemes of microprogrammed automata (MPA). The number of PLAs in the MPA logic scheme can be minimized by increasing the number of levels. In this paper, we analyze the structures of multilevel schemes of Mealy automata, propose a number of new structures, consider the corresponding correctness conditions, and examine some problems that must be solved in order to satisfy these conditions.
A multi-level method for sparse linear systems
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.
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…
Dynamic Sharing of the System Resources in Multilevel Secure System.
1986-09-26
Implementation : An Introduction." Computer. July 1983. 7. Corbett. P.J.. Multilevel Secure Front End For Data Communications. Master’s Thesis. Naval...will occur. d. Self-delete Module This module holds the ending of a child process. Self delete is required if the next step is delete the child...Application Program (Appendix C) 4) BDOS Application Program (Appendix D) To this end . it was necessary to construct the following support programs 1
Organolead Halide Perovskites for Low Operating Voltage Multilevel Resistive Switching.
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.
Multilevel Interventions and Racial/Ethnic Health Disparities
Badr, Hoda; Krebs, Paul; Das, Irene Prabhu
2012-01-01
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
Multilevel selection analysis of a microbial social trait
de Vargas Roditi, Laura; Boyle, Kerry E; Xavier, Joao B
2013-01-01
The study of microbial communities often leads to arguments for the evolution of cooperation due to group benefits. However, multilevel selection models caution against the uncritical assumption that group benefits will lead to the evolution of cooperation. We analyze a microbial social trait to precisely define the conditions favoring cooperation. We combine the multilevel partition of the Price equation with a laboratory model system: swarming in Pseudomonas aeruginosa. We parameterize a population dynamics model using competition experiments where we manipulate expression, and therefore the cost-to-benefit ratio of swarming cooperation. Our analysis shows that multilevel selection can favor costly swarming cooperation because it causes population expansion. However, due to high costs and diminishing returns constitutive cooperation can only be favored by natural selection when relatedness is high. Regulated expression of cooperative genes is a more robust strategy because it provides the benefits of swarming expansion without the high cost or the diminishing returns. Our analysis supports the key prediction that strong group selection does not necessarily mean that microbial cooperation will always emerge. PMID:23959025
Soft-assembled Multilevel Dynamics of Tactical Behaviors in Soccer
Ric, Angel; Torrents, Carlota; Gonçalves, Bruno; Sampaio, Jaime; Hristovski, Robert
2016-01-01
This study aimed to identify the tactical patterns and the timescales of variables during a soccer match, allowing understanding the multilevel organization of tactical behaviors, and to determine the similarity of patterns performed by different groups of teammates during the first and second halves. Positional data from 20 professional male soccer players from the same team were collected using high frequency global positioning systems (5 Hz). Twenty-nine categories of tactical behaviors were determined from eight positioning-derived variables creating multivariate binary (Boolean) time-series matrices. Hierarchical principal component analysis (PCA) was used to identify the multilevel structure of tactical behaviors. The sequential reduction of each set level of principal components revealed a sole principal component as the slowest collective variable, forming the global basin of attraction of tactical patterns during each half of the match. In addition, the mean dwell time of each positioning-derived variable helped to understand the multilevel organization of collective tactical behavior during a soccer match. This approach warrants further investigations to analyze the influence of task constraints on the emergence of tactical behavior. Furthermore, PCA can help coaches to design representative training tasks according to those tactical patterns captured during match competitions and to compare them depending on situational variables. PMID:27761120
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.
Reliability estimation in a multilevel confirmatory factor analysis framework.
Geldhof, G John; Preacher, Kristopher J; Zyphur, Michael J
2014-03-01
Scales with varying degrees of measurement reliability are often used in the context of multistage sampling, where variance exists at multiple levels of analysis (e.g., individual and group). Because methodological guidance on assessing and reporting reliability at multiple levels of analysis is currently lacking, we discuss the importance of examining level-specific reliability. We present a simulation study and an applied example showing different methods for estimating multilevel reliability using multilevel confirmatory factor analysis and provide supporting Mplus program code. We conclude that (a) single-level estimates will not reflect a scale's actual reliability unless reliability is identical at each level of analysis, (b) 2-level alpha and composite reliability (omega) perform relatively well in most settings, (c) estimates of maximal reliability (H) were more biased when estimated using multilevel data than either alpha or omega, and (d) small cluster size can lead to overestimates of reliability at the between level of analysis. We also show that Monte Carlo confidence intervals and Bayesian credible intervals closely reflect the sampling distribution of reliability estimates under most conditions. We discuss the estimation of credible intervals using Mplus and provide R code for computing Monte Carlo confidence intervals.
Propensity score weighting for a continuous exposure with multilevel data.
Schuler, Megan S; Chu, Wanghuan; Coffman, Donna
2016-12-01
Propensity score methods (e.g., matching, weighting, subclassification) provide a statistical approach for balancing dissimilar exposure groups on baseline covariates. These methods were developed in the context of data with no hierarchical structure or clustering. Yet in many applications the data have a clustered structure that is of substantive importance, such as when individuals are nested within healthcare providers or within schools. Recent work has extended propensity score methods to a multilevel setting, primarily focusing on binary exposures. In this paper, we focus on propensity score weighting for a continuous, rather than binary, exposure in a multilevel setting. Using simulations, we compare several specifications of the propensity score: a random effects model, a fixed effects model, and a single-level model. Additionally, our simulations compare the performance of marginal versus cluster-mean stabilized propensity score weights. In our results, regression specifications that accounted for the multilevel structure reduced bias, particularly when cluster-level confounders were omitted. Furthermore, cluster mean weights outperformed marginal weights.
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.
Variable-speed wind power system with improved energy capture via multilevel conversion
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.
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
Ganjwala, Dhiren
2011-01-01
Background: The evidence for the effectiveness of orthopaedic surgery to correct crouch gait in cerebral diplegic is insufficient. The crouch gait is defined as walking with knee flexion and ankle dorsiflexion through out the stance phase. Severe crouch gait in patients with spastic diplegia causes excessive loading of the patellofemoral joint and may result in anterior knee pain, gait deterioration, and progressive loss of function. We retrospectively evaluated the effect of surgery on the mobility and energy consumption at one year or more with the help of validated scales and scores. Materials and Methods: 18 consecutive patients with mean age of 14.6 years with cerebral diplegia with crouched gait were operated for multilevel orthopaedic surgery. Decisions for surgery were made with the observations on gait analysis and physical examination. The surgical intervention consisted of lengthening of short muscle-tendon units, shortening of long muscles and correction of osseous deformities. The paired samples t test was used to compare values of physical examination findings, walking speed and physiological cost index. Two paired sample Wilcoxon signed rank test was used to compare functional walking scales. Results: After surgery, improvements in functional mobility, walking speed and physiological cost index were found. No patient was able to walk 500 meters before surgery while all were able to walk after surgery. The improvements that were noted at one year were maintained at two years. Conclusions: Multilevel orthopedic surgery for older children and adolescents with crouch gait is effective for improving function and independence. PMID:21772623
Multi-level recordable disc using signal waveform modulation recording method
NASA Astrophysics Data System (ADS)
Pei, Jing; Pan, Longfa; Yang, Bo; Hu, Junhua
A new kind of multi-level recordable disc is presented in this paper. By improving the recording control signal in DVD-R/RW burning process, a Multi-level disc with signal waveform modulation can be achieved. The multi-level recording method increases the recording density but also the channel noise. The optimally designed partial response maximum likelihood (PRML) equalizer is effective in recovering channel symbol, and the original error rate reach 10E-4. This kind of multi-level method can be used for the purpose such as increasing the capacity of disc, hiding data and burning disc identification information etc.
Cross-over component code construction for multi-level block modulation codes
NASA Technical Reports Server (NTRS)
Kasami, Tadao; Takata, Toyoo; Fujiwara, Toru; Lin, Shu
1990-01-01
This paper investigates the multilevel technique for combining block coding and modulation. Several specific methods for constructing multilevel block modulation codes with interdependency among component codes are presented. 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-prime which has the same rate as C, a minimum squared Euclidean distance not less than that of 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.
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.
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.
Multilevel modeling for inference of genetic regulatory networks
NASA Astrophysics Data System (ADS)
Ng, Shu-Kay; Wang, Kui; McLachlan, Geoffrey J.
2005-12-01
Time-course experiments with microarrays are often used to study dynamic biological systems and genetic regulatory networks (GRNs) that model how genes influence each other in cell-level development of organisms. The inference for GRNs provides important insights into the fundamental biological processes such as growth and is useful in disease diagnosis and genomic drug design. Due to the experimental design, multilevel data hierarchies are often present in time-course gene expression data. Most existing methods, however, ignore the dependency of the expression measurements over time and the correlation among gene expression profiles. Such independence assumptions violate regulatory interactions and can result in overlooking certain important subject effects and lead to spurious inference for regulatory networks or mechanisms. In this paper, a multilevel mixed-effects model is adopted to incorporate data hierarchies in the analysis of time-course data, where temporal and subject effects are both assumed to be random. The method starts with the clustering of genes by fitting the mixture model within the multilevel random-effects model framework using the expectation-maximization (EM) algorithm. The network of regulatory interactions is then determined by searching for regulatory control elements (activators and inhibitors) shared by the clusters of co-expressed genes, based on a time-lagged correlation coefficients measurement. The method is applied to two real time-course datasets from the budding yeast (Saccharomyces cerevisiae) genome. It is shown that the proposed method provides clusters of cell-cycle regulated genes that are supported by existing gene function annotations, and hence enables inference on regulatory interactions for the genetic network.
Multilevel Effects of Wealth on Women's Contraceptive Use in Mozambique
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
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.
Synergistic High Charge-Storage Capacity for Multi-level Flexible Organic Flash Memory
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
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…
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…
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.
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…
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…
Multilevel Motivation and Engagement: Assessing Construct Validity across Students and Schools
ERIC Educational Resources Information Center
Martin, Andrew J.; Malmberg, Lars-Erik; Liem, Gregory Arief D.
2010-01-01
Statistical biases associated with single-level analyses underscore the importance of partitioning variance/covariance matrices into individual and group levels. From a multilevel perspective based on data from 21,579 students in 58 high schools, the present study assesses the multilevel factor structure of motivation and engagement with a…
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…
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…
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…
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…
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…
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;…
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…
ERIC Educational Resources Information Center
Park, Jungkyu; Yu, Hsiu-Ting
2016-01-01
The multilevel latent class model (MLCM) is a multilevel extension of a latent class model (LCM) that is used to analyze nested structure data structure. The nonparametric version of an MLCM assumes a discrete latent variable at a higher-level nesting structure to account for the dependency among observations nested within a higher-level unit. In…
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…
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…
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.
A multilevel method for conductive-radiative heat transfer
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.
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.
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
Speed and efficiency limits of multilevel incoherent heat engines
NASA Astrophysics Data System (ADS)
Mukherjee, V.; Niedenzu, W.; Kofman, A. G.; Kurizki, G.
2016-12-01
We present a comprehensive theory of heat engines (HE) based on a quantum-mechanical "working fluid" (WF) with periodically modulated energy levels. The theory is valid for any periodicity of driving Hamiltonians that commute with themselves at all times and do not induce coherence in the WF. Continuous and stroke cycles arise in opposite limits of this theory, which encompasses hitherto unfamiliar cycle forms, dubbed here hybrid cycles. The theory allows us to discover the speed, power, and efficiency limits attainable by incoherently operating multilevel HE depending on the cycle form and the dynamical regimes.
Laminoplasty Techniques for the Treatment of Multilevel Cervical Stenosis
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
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.
High-speed multilevel 512x512 spatial light modulator
NASA Astrophysics Data System (ADS)
Bauchert, Kipp A.; Serati, Steven A.
2000-03-01
Recent advances in our high-speed multi-level (analog) 512 X 512 liquid crystal spatial light modulator (SLM) will be presented. These advancements include smaller pixel pitch, greatly improved optical efficiency, and higher speed operation. The new VLSI SLM can utilize Ferroelectric Liquid Crystal to Nematic Liquid Crystal to achieve phase-only, amplitude-only, and phase-amplitude-coupled modulation. This device has applications in optical processing, optical storage, holographic display, and beam steering. Design criteria and experimental data will be presented.
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.
ERIC Educational Resources Information Center
Pavlyuk, Victoria; Ivanchyuk, Halyna
2016-01-01
The article deals with the peculiarities of future teachers' training content in the system of Canadian multilevel teacher education. Main features of the Canadian teachers' training content are the standardization of multilevel pedagogical education content, Canada's focus on multilevel teachers' education in professional development of future…
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…
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…
An improved multilevel optimization approach for the design of complex engineering systems
NASA Technical Reports Server (NTRS)
Barthelemy, J.-F. M.; Riley, M. F.
1986-01-01
Multilevel optimization methods are being considered for the design of complex systems on distributed networks of computers or even parallel processors. An obstacle to the use of multilevel methods is that they can be computationally expensive because of the cycling necessary to account for the coupling between the subproblems. This research effort aims at increasing the efficiency of multilevel optimization by adapting two techniques that are widely used in conventional one-level optimization: constraint approximation and temporary constraint deletion. These improvements are implemented and tested on three-, ten- and 52-bar planar truss designs. The results show that for larger problems (approximately 100 design variables and larger), the cost of analysis dominates the total cost so that multilevel optimization is no more expensive than one-level optimization. If parallel processing is used or the analysis process itself is decomposed, then multilevel optimization stands to become more economical than one-level optimization.
Work-related road traffic injury: a multilevel systems protocol
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
Time issues in multilevel interventions for cancer treatment and prevention.
Alexander, Jeffrey; Prabhu Das, Irene; Johnson, Timothy P
2012-05-01
The concept of time introduces important complexities in estimating intervention effects, program and evaluation design, and measurement and analysis of individual change in multilevel interventions (MLIs). Despite growing recognition that time is a critical element for assessing both individual-level outcomes and higher-level changes in organizational, community, and policy contexts, most MLI designs and evaluations have not addressed these issues. In this chapter we discuss 1) conceptualizing disease life-course and treatment theory in MLIs, 2) approaches to incorporating time in research and program design for MLIs in cancer treatment and prevention, 3) analysis of time-varying multilevel data in the context of cancer treatment and prevention, and 4) resource considerations and trade-offs of incorporating time as a dimension of MLIs and analysis. Although analytic techniques for analyzing time-related phenomena are becoming more available and powerful, there has not been corresponding progress made in the development of theory to guide the application of these techniques in program design and implementation.
Multilevel perspective on high-order harmonic generation in solids
NASA Astrophysics Data System (ADS)
Wu, Mengxi; Browne, Dana A.; Schafer, Kenneth J.; Gaarde, Mette B.
2016-12-01
We investigate high-order harmonic generation in a solid, modeled as a multilevel system dressed by a strong infrared laser field. We show that the cutoff energies and the relative strengths of the multiple plateaus that emerge in the harmonic spectrum can be understood both qualitatively and quantitatively by considering a combination of adiabatic and diabatic processes driven by the strong field. Such a model was recently used to interpret the multiple plateaus exhibited in harmonic spectra generated by solid argon and krypton [G. Ndabashimiye et al., Nature 534, 520 (2016), 10.1038/nature17660]. We also show that when the multilevel system originates from the Bloch state at the Γ point of the band structure, the laser-dressed states are equivalent to the Houston states [J. B. Krieger and G. J. Iafrate, Phys. Rev. B 33, 5494 (1986), 10.1103/PhysRevB.33.5494] and will therefore map out the band structure away from the Γ point as the laser field increases. This leads to a semiclassical three-step picture in momentum space that describes the high-order harmonic generation process in a solid.
Multi-Level Bitmap Indexes for Flash Memory Storage
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.
Multilevel Intervention Research: Lessons Learned and Pathways Forward
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
Community violence and urban childhood asthma: a multilevel analysis.
Sternthal, M J; Jun, H-J; Earls, F; Wright, R J
2010-12-01
We examined the association between community violence exposure and childhood asthma risk in a multilevel, multimethod, longitudinal study controlling for individual- and neighbourhood-level confounders and pathway variables. Analyses included 2,071 children aged 0-9 yrs at enrolment from the Project on Human Development in Chicago Neighborhoods. Multilevel logistic regression models estimated the likelihood of asthma, controlling for individual-level (child's age, sex, race/ethnicity, maternal asthma, socioeconomic status and family violence in the home) and neighbourhood-level confounders (concentrated disadvantage, collective efficacy and social disorder), and pathway variables (maternal smoking, breastfeeding). In adjusted analyses, medium (OR 1.60, 95% CI 1.17-2.19) and high levels (OR 1.56, 95% CI 1.12-2.18) of community violence were associated with increased asthma risk, relative to low levels. The increased asthma risk remained for African Americans when models included community violence and all other individual-level covariates, but attenuated to borderline nonsignificance when further adjusting for collective efficacy. Community violence is associated with asthma risk when controlling for individual- and neighborhood-level confounders. Neither community violence, nor the other individual-level factors, fully accounted for the excess asthma burden among African Americans. These data suggest that public health interventions outside the biomedical model may be needed to reduce asthma in disadvantaged populations.
Multilevel Summation of Electrostatic Potentials Using Graphics Processing Units*
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
Community, culture and sustainability in multilevel dynamic systems intervention science.
Schensul, Jean J
2009-06-01
This paper addresses intertwined issues in the conceptualization, implementation and evaluation of multilevel dynamic systems intervention science (MDSIS). Interventions are systematically planned, conducted and evaluated social science-based cultural products intercepting the lives of people and institutions in the context of multiple additional events and processes (which also may be referred to as interventions) that may speed, slow or reduce change towards a desired outcome. Multilevel interventions address change efforts at multiple social levels in the hope that effects at each level will forge synergistic links, facilitating movement toward desired change. This paper utilizes an ecological framework that identifies macro (policy and regulatory institutions), meso (organizations and agencies with resources, and power) and micro (individuals, families and friends living in communities) interacting directly and indirectly. An MDSIS approach hypothesizes that change toward a goal will occur faster and more effectively when synchronized and supported across levels in a social system. MDSIS approaches by definition involve "whole" communities and cannot be implemented without the establishments of working community partnerships This paper takes a dynamic systems approach to science as conducted in communities, and discusses four concepts that are central to MDSIS--science, community, culture, and sustainability. These concepts are important in community based participatory research and to the targeting, refinement, and adaptation of enduring interventions. Consistency in their meaning and use can promote forward movement in the field of MDSIS, and in community-based prevention science.
Multi-level graph layout on the GPU.
Frishman, Yaniv; Tal, Ayellet
2007-01-01
This paper presents a new algorithm for force directed graph layout on the GPU. The algorithm, whose goal is to compute layouts accurately and quickly, has two contributions. The first contribution is proposing a general multi-level scheme, which is based on spectral partitioning. The second contribution is computing the layout on the GPU. Since the GPU requires a data parallel programming model, the challenge is devising a mapping of a naturally unstructured graph into a well-partitioned structured one. This is done by computing a balanced partitioning of a general graph. This algorithm provides a general multi-level scheme, which has the potential to be used not only for computation on the GPU, but also on emerging multi-core architectures. The algorithm manages to compute high quality layouts of large graphs in a fraction of the time required by existing algorithms of similar quality. An application for visualization of the topologies of ISP (Internet Service Provider) networks is presented.
Two-dimensional wavelength demultiplexing employing multilevel arrayed waveguides.
Yang, Jianyi; Jiang, Xiaoqing; Wang, Minghua; Wang, Yuelin
2004-03-22
Two-dimensional (2D) optical wavelength demultiplexing is demonstrated by employing multilevel arrayed waveguides as a 2D diffraction grating, named the 2D arrayed waveguide grating (2D-AWG). Since the monochromatic lightwave is diffracted by the 2D-AWG to a series of periodic spots with 2D diffraction orders in both x and y directions while the dispersion direction is never parallel to the x or y direction, we can obtain 2D wavelength demultiplexing exploiting diffraction orders of either the x or y direction. One of the two dispersion components is designed much larger than the other, and the correspondent spatial free spectral range component is set properly to ensure high diffraction efficiency. The input and output ports can also be designed based on the multilevel lightwave circuit (MLC), and their level planes can be tuned parallel to that of the MLC-based 2D-AWG, which makes it feasible to integrate the 2D-AWG with the input port and/or the output port. It provides a promising way to realize large-scale and high-density optical multiplexers/demultiplexers.
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).
Advanced micromechanisms in a multi-level polysilicon technology
Rodgers, M.S.; Sniegowski, J.J.; Miller, S.L.; Barron, C.C.; McWhorter, P.J.
1997-08-01
Quad-level polysilicon surface micromachining technology, comprising three mechanical levels plus an electrical interconnect layer, is giving rise to a new generation of micro-electromechanical devices and assemblies. Enhanced components can not be produced through greater flexibility in fabrication and design. New levels of design complexity that include multi-level gears, single-attempt locks, and optical elements have recently been realized. Extensive utilization of the fourth layer of polysilicon differentiates these latter generation devices from their predecessors. This level of poly enables the fabrication of pin joints, linkage arms, hinges on moveable plates, and multi-level gear assemblies. The mechanical design aspects of these latest micromachines will be discussed with particular emphasis on a number of design aspects of these latest micromachines will be discussed with particular emphasis on a number of design modifications that improve the power, reliability, and smoothness of operation of the microengine. The microengine is the primary actuation mechanism that is being used to drive mirrors out of plane and rotate 1600-{mu}m diameter gears. Also discussed is the authors most advanced micromechanical system to date, a complex proof-of-concept batch-fabricated assembly that, upon transmitting the proper electrical code to a mechanical lock, permits the operation of a micro-optical shutter.
Multi-level assemblies of lead sulphide nanorods.
Lu, Qingyi; Gao, Feng; Komarneni, Sridhar
2006-05-28
A new concept of multi-level assemblies of nanorod-based structures has been proposed, which could give new insight into the construction of nanorod-based complex structures from the bottom up. Multi-level architectures of complex lead sulphide (PbS) nanorod-based structures have been realized by a simple and general amino acid-mediated approach. First-level structure (multi-arm horn-like structure), second-level structure (bi-pyramid structure formed by several horn-like structures), and third-level structure (multi-pyramid structure formed by several pyramid-like structures) can be synthesized with the assistance of different amino acids: aspartic acid, serine, and histidine, respectively. The amino acids have several functional groups, such as -NH(2) and -COOH, which have strong abilities for coordination with the metal ions, and might provide reaction sites by coordinating with metal ions to initiate and then confine the assemblies of the PbS nanorods. This amino acid-mediated method provides a possibility of studying the formation and assembly mechanisms from the bottom up and might open a door to constructing complex nanorod-based structures at different levels.
Landau-Zener transitions in an open multilevel quantum system
NASA Astrophysics Data System (ADS)
Ashhab, S.
2016-10-01
We consider the Landau-Zener problem for a multilevel quantum system that is coupled to an external environment. In particular, we consider a number of cases of three-level systems coupled to a harmonic oscillator that represents the external environment. We find that, similar to the case of the Landau-Zener problem with a two-level system, when the quantum system and the environment are both initially in their ground states the probability that the system remains in the same quantum state is not affected by the coupling to the environment. The final occupation probabilities of the other states are well described by a common general principle: the coupling to the environment turns each Landau-Zener transition process in the closed system into a sequence of smaller transitions in the combined Hilbert space of the system and environment, and this sequence of transitions lasts a total duration that increases with increasing system-environment coupling strength. These results provide an intuitive understanding of Landau-Zener transitions in open multilevel quantum systems.
Multilevel selection theory and evidence: a critique of Gardner, 2015.
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.
A dynamic ant colony optimization for load balancing in MRN/MLN
NASA Astrophysics Data System (ADS)
Lu, Le; Huang, Shanguo; Gu, Wanyi
2011-12-01
Ant Colony Optimization (ACO) is a popular research field these years. Ants choose paths where pheromone concentration is higher and modify the environment they visited. However, in the context of multi-service in multi-level and multi-domain optical network, the capacity of inter-domain links is limited. Congestion may be occurred at inter-domain links. In this paper, ant colony optimization algorithm based on load balancing is proposed. Ants follow paths not just depend on pheromone alone, we also take available resources on the link as a factor too. Simulations show the proposed method could reduce the traffic blocking probability, and realize load balancing within the network.
NASA Astrophysics Data System (ADS)
Sun, Yuan; Bhattacherjee, Anol
2011-11-01
Information technology (IT) usage within organisations is a multi-level phenomenon that is influenced by individual-level and organisational-level variables. Yet, current theories, such as the unified theory of acceptance and use of technology, describe IT usage as solely an individual-level phenomenon. This article postulates a model of organisational IT usage that integrates salient organisational-level variables such as user training, top management support and technical support within an individual-level model to postulate a multi-level model of IT usage. The multi-level model was then empirically validated using multi-level data collected from 128 end users and 26 managers in 26 firms in China regarding their use of enterprise resource planning systems and analysed using the multi-level structural equation modelling (MSEM) technique. We demonstrate the utility of MSEM analysis of multi-level data relative to the more common structural equation modelling analysis of single-level data and show how single-level data can be aggregated to approximate multi-level analysis when multi-level data collection is not possible. We hope that this article will motivate future scholars to employ multi-level data and multi-level analysis for understanding organisational phenomena that are truly multi-level in nature.
Resche-Rigon, Matthieu; White, Ian R
2016-09-19
In multilevel settings such as individual participant data meta-analysis, a variable is 'systematically missing' if it is wholly missing in some clusters and 'sporadically missing' if it is partly missing in some clusters. Previously proposed methods to impute incomplete multilevel data handle either systematically or sporadically missing data, but frequently both patterns are observed. We describe a new multiple imputation by chained equations (MICE) algorithm for multilevel data with arbitrary patterns of systematically and sporadically missing variables. The algorithm is described for multilevel normal data but can easily be extended for other variable types. We first propose two methods for imputing a single incomplete variable: an extension of an existing method and a new two-stage method which conveniently allows for heteroscedastic data. We then discuss the difficulties of imputing missing values in several variables in multilevel data using MICE, and show that even the simplest joint multilevel model implies conditional models which involve cluster means and heteroscedasticity. However, a simulation study finds that the proposed methods can be successfully combined in a multilevel MICE procedure, even when cluster means are not included in the imputation models.
Three essays on multi-level optimization models and applications
NASA Astrophysics Data System (ADS)
Rahdar, Mohammad
The general form of a multi-level mathematical programming problem is a set of nested optimization problems, in which each level controls a series of decision variables independently. However, the value of decision variables may also impact the objective function of other levels. A two-level model is called a bilevel model and can be considered as a Stackelberg game with a leader and a follower. The leader anticipates the response of the follower and optimizes its objective function, and then the follower reacts to the leader's action. The multi-level decision-making model has many real-world applications such as government decisions, energy policies, market economy, network design, etc. However, there is a lack of capable algorithms to solve medium and large scale these types of problems. The dissertation is devoted to both theoretical research and applications of multi-level mathematical programming models, which consists of three parts, each in a paper format. The first part studies the renewable energy portfolio under two major renewable energy policies. The potential competition for biomass for the growth of the renewable energy portfolio in the United States and other interactions between two policies over the next twenty years are investigated. This problem mainly has two levels of decision makers: the government/policy makers and biofuel producers/electricity generators/farmers. We focus on the lower-level problem to predict the amount of capacity expansions, fuel production, and power generation. In the second part, we address uncertainty over demand and lead time in a multi-stage mathematical programming problem. We propose a two-stage tri-level optimization model in the concept of rolling horizon approach to reducing the dimensionality of the multi-stage problem. In the third part of the dissertation, we introduce a new branch and bound algorithm to solve bilevel linear programming problems. The total time is reduced by solving a smaller relaxation
Building of multilevel stakeholder consensus in radioactive waste repository siting
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
Planarization of metal films for multilevel interconnects by pulsed laser heating
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.
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.
Finding Chemical Reaction Paths with a Multilevel Preconditioning Protocol
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.
Finding Chemical Reaction Paths with a Multilevel Preconditioning Protocol
Kale, Seyit; Sode, Olaseni; Weare, Jonathan; ...
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
Union leadership and member attitudes: a multi-level analysis.
Hammer, Tove Helland; Bayazit, Mahmut; Wazeter, David L
2009-03-01
Analyses of union leadership roles show that union presidents should have both a within-union focus and an external focus. The authors combined multi-level survey data from 3,871 union members in 248 local teachers' unions with archival and field staff data to examine relationships between leadership and members' perceptions of union instrumentality and justice, union commitment, and participation. The results showed significant union-level effects on members' beliefs about, and attitudes toward, their unions, attributable to the presidents' internal and external leadership, wage outcomes, and union characteristics. Relationships between internally focused leadership and members' loyalty and willingness to work for the union were partially mediated by perceptions of union instrumentality and justice. These perceptions fully mediated the relationship between externally focused leadership and union loyalty.
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.
Schwarz and multilevel methods for quadratic spline collocation
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.
Multigrid and multilevel domain decomposition for unstructured grids
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.
A multilevel multiscale mimetic method for an anisotropic infiltration problem
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.
Efficient multilevel brain tumor segmentation with integrated bayesian model classification.
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.
Finding Chemical Reaction Paths with a Multilevel Preconditioning Protocol
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
The multilevel four-stroke swap engine and its environment
NASA Astrophysics Data System (ADS)
Uzdin, Raam; Kosloff, Ronnie
2014-09-01
A multilevel four-stroke engine where the thermalization strokes are generated by unitary collisions with thermal bath particles is analyzed. Our model is solvable even when the engine operates far from thermal equilibrium and in the strong system-bath coupling. Necessary operation conditions for the heat machine to perform as an engine or a refrigerator are derived. We relate the work and efficiency of the device to local and non-local statistical properties of the baths (purity, index of coincidence, etc) and put upper bounds on these quantities. Finally, in the ultra-hot regime, we analytically optimize the work and find a striking similarity to results obtained for efficiency at maximal power of classical engines. The complete swap limit of our results holds for any four-stroke quantum Otto engine that is coupled to the baths for periods that are significantly longer than the thermal relaxation time.
Lung nodule classification with multilevel patch-based context analysis.
Zhang, Fan; Song, Yang; Cai, Weidong; Lee, Min-Zhao; Zhou, Yun; Huang, Heng; Shan, Shimin; Fulham, Michael J; Feng, Dagan D
2014-04-01
In this paper, we propose a novel classification method for the four types of lung nodules, i.e., well-circumscribed, vascularized, juxta-pleural, and pleural-tail, in low dose computed tomography scans. The proposed method is based on contextual analysis by combining the lung nodule and surrounding anatomical structures, and has three main stages: an adaptive patch-based division is used to construct concentric multilevel partition; then, a new feature set is designed to incorporate intensity, texture, and gradient information for image patch feature description, and then a contextual latent semantic analysis-based classifier is designed to calculate the probabilistic estimations for the relevant images. Our proposed method was evaluated on a publicly available dataset and clearly demonstrated promising classification performance.
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.
Development of the Multi-Level Seismic Receiver (MLSR)
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.
Ecological influences of early childhood obesity: a multilevel analysis.
Boonpleng, Wannaporn; Park, Chang Gi; Gallo, Agatha M; Corte, Colleen; McCreary, Linda; Bergren, Martha Dewey
2013-07-01
This study aims to determine the contributing factors for early childhood overweight/obesity within the contexts of the child's home, school, and community, and to determine how much each of the ecological contexts contributes to childhood overweight/obesity. The framework was developed from Bronfenbrenner's ecological systems theory. Data for 2,100 children from the Early Childhood Longitudinal Study, Birth Cohort, were used in a series of multilevel modeling analyses. There was significant variation in childhood overweight/obesity by school and community. The majority of variation in childhood overweight/obesity was explained by the child and family factors in addition to school and community factors. Explained variance of childhood overweight/obesity at the school level was 27% and at the community level, 2%. The variance composition at children's family level alone was 71%. Therefore, overweight/obesity prevention efforts should focus primarily on child, family, and school factors and then community factors, to be more effective.
A multilevel study of leadership, empowerment, and performance in teams.
Chen, Gilad; Kirkman, Bradley L; Kanfer, Ruth; Allen, Don; Rosen, Benson
2007-03-01
A multilevel model of leadership, empowerment, and performance was tested using a sample of 62 teams, 445 individual members, 62 team leaders, and 31 external managers from 31 stores of a Fortune 500 company. Leader-member exchange and leadership climate related differently to individual and team empowerment and interacted to influence individual empowerment. Also, several relationships were supported in more but not in less interdependent teams. Specifically, leader-member exchange related to individual performance partially through individual empowerment; leadership climate related to team performance partially through team empowerment; team empowerment moderated the relationship between individual empowerment and performance; and individual performance was positively related to team performance. Contributions to team leadership theory, research, and practices are discussed.
Collaborating for impact: a multilevel early childhood obesity prevention initiative.
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.
Multilevel cascade voltage source inverter with separate DC sources
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.
Multilevel cascade voltage source inverter with seperate DC sources
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.
Multilevel cascade voltage source inverter with seperate DC sources
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.
Multilevel cascade voltage source inverter with seperate DC sources
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.
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.
The effects of weather on daily mood: a multilevel approach.
Denissen, Jaap J A; Butalid, Ligaya; Penke, Lars; van Aken, Marcel A G
2008-10-01
The present study examines the effects of six weather parameters (temperature, wind power, sunlight, precipitation, air pressure, and photoperiod) on mood (positive affect, negative affect, and tiredness). Data were gathered from an online diary study (N = 1,233), linked to weather station data, and analyzed by means of multilevel analysis. Multivariate and univariate analyses enabled distinction between unique and shared effects. The results revealed main effects of temperature, wind power, and sunlight on negative affect. Sunlight had a main effect on tiredness and mediated the effects of precipitation and air pressure on tiredness. In terms of explained variance, however, the average effect of weather on mood was only small, though significant random variation was found across individuals, especially regarding the effect of photoperiod. However, these individual differences in weather sensitivity could not be explained by the Five Factor Model personality traits, gender, or age.
Multilevel image authentication using shared secret threshold and phase retrieval
NASA Astrophysics Data System (ADS)
Pan, Xuemei; Meng, Xiangfeng; Wang, Yurong; Yang, Xiulun; Peng, Xiang; He, Wenqi; Dong, Guoyan; Chen, Hongyi
2014-10-01
A new kind of multilevel authentication system based on the (t, n) threshold secret sharing scheme and the iterative phase retrieval algorithm in Fresnel domain is proposed, in which, the first phase distribution iteratively generated is divided into n parts and delivered to n different participants, during high-level authentication, any t (t ≤ n) or more of them can be collected to reconstruct the original meaningful certification image; While in the case of low-level authentication, any t - 1 or fewer will gain no significant information of certification image, however, it can result in a remarkable peak output in the nonlinear correlation coefficient of the recovered image and the standard certification image, which can successfully provide an additional authentication layer for the high-level authentication. Theoretical analysis and numerical simulations both validate the feasibility of our proposed scheme.
Drilling and completion specifications for CA series multilevel piezometers
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.
High density multi-level recording for archival data preservation
NASA Astrophysics Data System (ADS)
Holzner, F.; Paul, Ph.; Drechsler, U.; Despont, M.; Knoll, A. W.; Duerig, U.
2011-07-01
Archival data storage is predominantly based on magnetic tape technology. An alternative probe based multi-level recording scheme is proposed which specifically addresses the issue of long term data preservation. In a first step, the data are written as topographic relief in an organic resist. To achieve long term preservation, the relief structure is transferred in a Si based inorganic carrier by means of reactive ion etching. Thereby, the data are preserved as written in stone. Using 3-level logic, a storage density of 99 Gb/in2 is demonstrated and read-back of the data is accomplished with an error rate of 10-3 based on threshold detection. Exploiting etch anisotropy in layered substrates, logic levels can be physically separated from one another in different layers which enhances tamper resistance and also provides a means for heterogeneous storage concepts.
Multi-level Algorithm for the Anderson Impurity Model
NASA Astrophysics Data System (ADS)
Chandrasekharan, S.; Yoo, J.; Baranger, H. U.
2004-03-01
We develop a new quantum Monte Carlo algorithm to solve the Anderson impurity model. Instead of integrating out the Fermions, we work in the Fermion occupation number basis and thus have direct access to the Fermionic physics. The sign problem that arises in this formulation can be solved by a multi-level technique developed by Luscher and Weisz in the context of lattice QCD [JHEP, 0109 (2001) 010]. We use the directed-loop algorithm to update the degrees of freedom. Further, this algorithm allows us to work directly in the Euclidean time continuum limit for arbitrary values of the interaction strength thus avoiding time discretization errors. We present results for the impurity susceptibility and the properties of the screening cloud obtained using the algorithm.
A multilevel perspective to explain recycling behaviour in communities.
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
Multilevel and multi-user sustainability assessment of farming systems
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.
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.
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
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
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.
MULTILEVEL ACCELERATION OF STOCHASTIC COLLOCATION METHODS FOR PDE WITH RANDOM INPUT DATA
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.
NASA Astrophysics Data System (ADS)
Braginets, Eugene; Kurashov, V.; Honcharuk, S.; Girnyk, V.; Kostyukevych, S.; Kostyukevych, K.
2011-02-01
The goal of a present research is to develop a method for production of multilevel Diffractive Optical Elements (DOEs) for use in Digital Security Holograms, using the direct-writing maskless lithography system.
GROUND WATER MONITORING AND SAMPLING: MULTI-LEVEL VERSUS TRADITIONAL METHODS – WHAT’S WHAT?
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...
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.
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.
On Normal Theory Based Inference for Multilevel Models with Distributional Violations.
ERIC Educational Resources Information Center
Yuan, Ke-Hai; Bentler, Peter M.
2002-01-01
Developed a sandwich-type covariance matrix to evaluate parameters and provide a rescaled statistic to evaluate a hypothesized general multilevel model. A simulation study with a two-level factor model implies that the rescaled statistic is preferable. (SLD)
Emsens, W-J; Aggenbach, C J S; Grootjans, A P; Nfor, E E; Schoelynck, J; Struyf, E; van Diggelen, R
2016-10-01
Eutrophication is a major threat for the persistence of nutrient-poor fens, as multilevel feedbacks on decomposition rates could trigger carbon loss and increase nutrient cycling. Here, we experimentally investigate the effects of macronutrient (NPK) enrichment on litter quality of six species of sedge (Carex sp.), which we relate to litter decomposition rates in a nutrient-poor and nutrient-rich environment. Our research focused on four levels: we examined how eutrophication alters (1) fresh litter production ("productivity shift"), (2) litter stoichiometry within the same species ("intraspecific shift"), (3) overall litter stoichiometry of the vegetation under the prediction that low-competitive species are outcompeted by fast-growing competitors ("interspecific shift"), and (4) litter decomposition rates due to an altered external environment (e.g., shifts in microbial activity; "exogenous shift"). Eutrophication triggered a strong increase in fresh litter production. Moreover, individuals of the same species produced litter with lower C:N and C:P ratios, higher K contents, and lower lignin, Ca and Mg contents (intraspecific shift), which increased litter decomposability. In addition, species typical for eutrophic conditions produced more easily degradable litter than did species typical for nutrient-poor conditions (interspecific shift). However, the effects of nutrient loading of the external environment (exogenous shift) were contradictory. Here, interactions between litter type and ambient nutrient level indicate that the (exogenous) effects of eutrophication on litter decomposition rates are strongly dependent of litter quality. Moreover, parameters of litter quality only correlated with decomposition rates for litter incubated in nutrient-poor environments, but not in eutrophic environments. This suggests that rates of litter decomposition can be uncoupled from litter stoichiometry under eutrophic conditions. In conclusion, our results show that
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.
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.
Macdonald, James S. P.; Lavie, Nilli
2008-01-01
Although the perceptual load theory of attention has stimulated a great deal of research, evidence for the role of perceptual load in determining perception has typically relied on indirect measures that infer perception from distractor effects on reaction times or neural activity (see N. Lavie, 2005d`) was consistently reduced with high, compared to low, perceptual load but was unaffected by the level of working memory load. Because alternative accounts in terms of expectation, memory, response bias, and goal-neglect due to the more strenuous high load task were ruled out, these experiments clearly demonstrate that high perceptual load determines conscious perception, impairing the ability to merely detect the presence of a stimulus—a phenomenon of load induced blindness. PMID:18823196
NASA Astrophysics Data System (ADS)
Paletou, F.
1995-10-01
We have implemented standard partial frequency redistribution (PRD) in a two-dimensional multilevel non-LTE radiative transfer code. The Multilevel Accelerated Lambda Iteration (MALI) method is used. First, a numerical approach for treating standard PRD effects is described, as well as a simple method for treating an optically thick bound-free transition with MALI. Then, the method is validated in mono-dimensional geometry. Finally, preliminary results from two-dimensional radiative modelling of solar prominences are presented.
Asymmetric Multilevel Outphasing (AMO): A New Architecture for All-Silicon mm-Wave Transmitter ICs
2015-06-12
AMO ) architecture and also nonlinear predistortion of the transmitter. Finally, the foundation of the entire system 1. REPORT DATE (DD-MM-YYYY) 4...2015 1-Jun-2010 29-Feb-2016 Approved for Public Release; Distribution Unlimited Final Report: Asymmetric Multilevel Outphasing ( AMO ): A New Architecture...journals: Number of Papers published in non peer-reviewed journals: Final Report: Asymmetric Multilevel Outphasing ( AMO ): A New Architecture for All
Fraunhofer diffraction of the plane wave by a multilevel (quantized) spiral phase plate.
Kotlyar, Victor V; Kovalev, Alexey A
2008-01-15
We obtain an analytical expression in the form of a finite sum of plane waves that describes the paraxial scalar Fraunhofer diffraction of a limited plane wave by a multilevel (quantized) spiral phase plate (SPP) bounded by a polygonal aperture. For several topological charges of the SPP we numerically obtain the minimal number of SPP sectors for which the RMS between the Fraunhofer diffraction patterns for multilevel and continuous SPP does not exceed 2%.
Comparing Spatial and Multilevel Regression Models for Binary Outcomes in Neighborhood Studies
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
Modeling a multilevel boost converter using SiC components for PV application
NASA Astrophysics Data System (ADS)
Alateeq, Ayoob S.; Almalaq, Yasser A.; Matin, Mohammad A.
2016-09-01
This paper discusses a DC-DC multilevel boost with wide bandgap components for PV applications. In the PV system, the multilevel boost converter is advisable to be used over the conventional boost converter because of the high ratio conversion. The multilevel boost converter is designed with one inductor, 2N-1 silicon carbide (SiC) schottky diodes, 2N-1 capacitors and one SiC MOSFET where N is the number of levels. Inserting SiC components in the design helps to maintain the temperature effect that could cause a high power loss. Most function of using a multilevel boost converter is to produce a high output voltage without using either a power transformer or a coupled inductor. Achieving a high gain output in the multilevel boost converter depends on the level of the converter and the switching duty cycle. The demonstrated design is a multilevel boost converter supplies from 220 V to rate 2 KW power. The switching frequency is 100 KHz and the output voltage of 4-level is 3.5 KV. Several values of temperatures are applicable to the system and the effect of changing the temperature on efficiency is studied. The developed design is simulated by using a LTspice software and the results are discussed.
Multi-wavelength multi-level optical storage
NASA Astrophysics Data System (ADS)
Wullert, John R., II
Current digital information storage technologies offer rapid access and seemingly ever-increasing capacities. New storage techniques that improve the data rate of high-density storage technologies are attractive, particularly for cost-sensitive services such as video on demand. Wavelength multiplexing of optical information storage has the potential to increase storage capacity, density and data rate. This dissertation addresses the design, simulation and fabrication of a multi-wavelength, multi-level optical storage structure that has the potential to increase the capacity, density and data rate of optical storage. Multi-wavelength, multi-layer optical storage is a technique for storing data in many separate layers in a medium, where each layer responds to a unique optical wavelength. This approach builds on the strengths of current optical storage technologies and addresses some of their limitations. Multiple layers of storage increase the high storage density possible with optical techniques and the parallelism of wavelength multiplexing improves the relatively low data rate. Multi-wavelength, multi-level optical storage has been investigated theoretically and experimentally. The experimental results provide the first demonstration of optical storage using three wavelengths to read three separate layers of information. These read-only optical memories were based on dielectric mirrors of silicon dioxide, magnesium oxide and aluminum oxide. The layers were designed to be read with semiconductor lasers of 635, 780 and 980 nanometers. The prototype devices exhibited open margins between the on and off states for all eight combinations of the presence and absence of the three mirrors. Theoretical simulations were employed to assess the dynamic operation of multi-wavelength storage devices. Through systematic simulations, variations in the thickness and refractive index of the layers in the structure were identified as the primary noise mechanism and a critical
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.
Kepler, Christopher K.; Brodt, Erika D.; Dettori, Joseph R.; Albert, Todd J.
2012-01-01
Study design: Systematic review. Clinical questions: What is the effectiveness of multilevel cervical artificial disc replacement (C-ADR) compared with multilevel fusion with respect to pain and functional outcomes, and are the two procedures comparable in terms of safety? What is the effectiveness of multilevel C-ADR compared with single-level C-ADR with respect to pain and functional outcomes, and are the two procedures comparable in terms of safety? Methods: A systematic review was undertaken for articles published up to October 2011. Electronic databases and reference lists of key articles were searched to identify studies comparing multilevel C-ADR with multilevel anterior cervical discectomy and fusion (ACDF) or comparing multilevel C-ADR with single-level C-ADR. Studies which compared these procedures in the lumbar or thoracic spine or that reported alignment outcomes only were excluded. Two independent reviewers assessed the strength of evidence using the GRADE criteria and disagreements were resolved by consensus. Results: Two studies compared multilevel C-ADR with multilevel ACDF. While both reported improved Neck Disability Index (NDI) and Short-Form 36 (SF-36) scores after C-ADR compared with ACDF, only one study reported statistically significant results. Seven studies compared single-level C-ADR with multilevel C-ADR. Results were similar in terms of overall success, NDI and SF-36 scores, and patient satisfaction. There is discrepant information regarding rates of heterotopic ossification; dysphagia rate may be higher in multilevel C-ADR. Conclusions: The literature suggests that outcomes are at least similar for multilevel C-ADR and ACDF and may favor C-ADR. Future studies are necessary before firm recommendations can be made favoring one treatment strategy. Multilevel C-ADR seems to have similar results to single-level C-ADR but may have higher rates of heterotopic ossification and dysphagia. PMID:23236310
Dalstra, M; Cattaneo, P M; Laursen, M G; Beckmann, F; Melsen, B
2015-03-18
Multilevel synchrotron radiation-based microtomography has been performed on a human jaw segment obtained at autopsy by cutting increasingly smaller samples from the original segment. The focus of this study lay on the microstructure of the interface between root, periodontal ligament (PDL) and alveolar bone in order to find an answer to the question why alveolar bone remodels during orthodontic loading, when the associated stress and strain levels calculated with finite element analyses are well below the established threshold levels for bone remodeling. While the inner surface of the alveolus appears to be rather smooth on the lower resolution scans, detailed scans of the root-PDL-bone interface reveal that on a microscopical scale it is actually quite rough and uneven with bony spiculae protruding into the PDL space. Any external (orthodontic) loading applied to the root, when transferred through the PDL to the alveolar bone, will cause stress concentrations in these spiculae, rather than be distributed over a "smooth surface". As osteocyte lacunae are shown to be present in these spiculae, the local amplified stresses and strain can well be registered by the mechano-sensory network of osteocytes. In addition, a second stress amplification mechanism, due to the very presence of the lacunae themselves, is evidence that stresses and strains calculated with FE analyses, based on macroscopical scale models of teeth and their supporting structures, grossly underestimate the actual mechanical loading of alveolar bone at tissue level. It is therefore hypothesized that remodeling of alveolar bone is subject to the same biological regulatory process as remodeling in other bones.
Load regulating expansion fixture
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.
Load regulating expansion fixture
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.
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.
Dynamic localized load balancing
NASA Astrophysics Data System (ADS)
Balandin, Sergey I.; Heiner, Andreas P.
2003-08-01
Traditionally dynamic load balancing is applied in resource-reserved connection-oriented networks with a large degree of managed control. Load balancing in connectionless networks is rather rudimentary and is either static or requires network-wide load information. This paper presents a fully automated, traffic driven dynamic load balancing mechanism that uses local load information. The proposed mechanism is easily deployed in a multi-vendor environment in which only a subset of routers supports the function. The Dynamic Localized Load Balancing (DLLB) mechanism distributes traffic based on two sets of weights. The first set is fixed and is inverse proportional to the path cost, typically the sum of reciprocal bandwidths along the path. The second weight reflects the utilization of the link to the first next hop along the path, and is therefore variable. The ratio of static weights defines the ideal load distribution, the ratio of variable weights the node-local load distribution estimate. By minimizing the difference between variable and fixed ratios the traffic distribution, with the available node-local knowledge, is optimal. The above mechanism significantly increases throughput and decreases delay from a network-wide perspective. Optionally the variable weight can include load information of nodes downstream to prevent congestion on those nodes. The latter function further improves network performance, and is easily implemented on top of the standard OSPF signaling. The mechanism does not require many node resources and can be implemented on existing router platforms.
Implicit extrapolation methods for multilevel finite element computations
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.
Natural Resource Monitoring of Rheum tanguticum by Multilevel Remote Sensing
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
Data integration, systems approach and multilevel description of complex biosystems
NASA Astrophysics Data System (ADS)
Hernández-Lemus, Enrique
2013-12-01
Recent years have witnessed the development of new quantitative approaches and theoretical tenets in the biological sciences. The advent of high throughput experiments in genomics, proteomics and electrophysiology (to cite just a few examples) have provided the researchers with unprecedented amounts of data to be analyzed. Large datasets, however can not provide the means to achieve a complete understanding of the underlying biological phenomena, unless they are supplied with a solid theoretical framework and with proper analytical tools. It is now widely accepted that by using and extending some of the paradigmatic principles of what has been called complex systems theory, some degree of advance in this direction can be attained. We will be presenting ways in which by using data integration techniques (linear, non-linear, combinatorial, graphical), multidimensional-multilevel descriptions (multifractal modeling, dimensionality reduction, computational learning), as well as an approach based in systems theory (interaction maps, probabilistic graphical models, non-equilibrium physics) have allowed us to better understand some problems in the interface of Statistical Physics and Computational Biology.
Extracting building patterns with multilevel graph partition and building grouping
NASA Astrophysics Data System (ADS)
Du, Shihong; Luo, Liqun; Cao, Kai; Shu, Mi
2016-12-01
Building patterns are crucial for urban landscape evaluation, social analyses and multiscale spatial data automatic production. Although many studies have been conducted, there is still lack of satisfying results due to the incomplete typology of building patterns and the ineffective extraction methods. This study aims at providing a typology with four types of building patterns (e.g., collinear patterns, curvilinear patterns, parallel and perpendicular groups, and grid patterns) and presenting four integrated strategies for extracting these patterns effectively and efficiently. First, the multilevel graph partition method is utilized to generate globally optimal building clusters considering area, shape and visual distance similarities. In this step, the weights of similarity measurements are automatically estimated using Relief-F algorithm instead of manual selection, thus building clusters with high quality can be obtained. Second, based on the clusters produced in the first step, the extraction strategies group the buildings from each cluster into patterns according to the criteria of proximity, continuity and directionality. The proposed methods are tested using three datasets. The experimental results indicate that the proposed methods can produce satisfying results, and demonstrate that the F-Histogram model is better than the two widely used models (i.e., centroid model and the Voronoi graph) to represent relative directions for building patterns extraction.
National INFOSEC technical baseline: multi-level secure systems
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.
Race, Employment Disadvantages, and Heavy Drinking: A Multilevel Model.
Lo, Celia C; Cheng, Tyrone C
2015-01-01
We intended to determine (1) whether stress from employment disadvantages led to increased frequency of heavy drinking and (2) whether race had a role in the relationship between such disadvantages and heavy drinking. Study data came from the National Longitudinal Survey of Youth, a prospective study that has followed a representative sample of youth since 1979. Our study employed data from 11 particular years, during which the survey included items measuring respondents' heavy drinking. Our final sample numbered 10,171 respondents, which generated 75,394 person-waves for data analysis. Both of our hypotheses were supported by results from multilevel mixed-effects linear regression capturing the time-varying nature of three employment disadvantages and of the heavy-drinking outcome. Results show that more-frequent heavy drinking was associated with employment disadvantages, and that disadvantages' effects on drinking were stronger for Blacks and Hispanics than for Whites. That worsening employment disadvantages have worse effects on minority groups' heavy drinking (compared to Whites) probably contributes to the racial health disparities in our nation. Policies and programs addressing such disparities are especially important during economic downturns.
Nucleus segmentation in histology images with hierarchical multilevel thresholding
NASA Astrophysics Data System (ADS)
Ahmady Phoulady, Hady; Goldgof, Dmitry B.; Hall, Lawrence O.; Mouton, Peter R.
2016-03-01
Automatic segmentation of histological images is an important step for increasing throughput while maintaining high accuracy, avoiding variation from subjective bias, and reducing the costs for diagnosing human illnesses such as cancer and Alzheimer's disease. In this paper, we present a novel method for unsupervised segmentation of cell nuclei in stained histology tissue. Following an initial preprocessing step involving color deconvolution and image reconstruction, the segmentation step consists of multilevel thresholding and a series of morphological operations. The only parameter required for the method is the minimum region size, which is set according to the resolution of the image. Hence, the proposed method requires no training sets or parameter learning. Because the algorithm requires no assumptions or a priori information with regard to cell morphology, the automatic approach is generalizable across a wide range of tissues. Evaluation across a dataset consisting of diverse tissues, including breast, liver, gastric mucosa and bone marrow, shows superior performance over four other recent methods on the same dataset in terms of F-measure with precision and recall of 0.929 and 0.886, respectively.
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.
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.
Multilevel Context of Depression in Two American Indian Tribes
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
Multilevel soil-vapor extraction test for heterogeneous soil
Widdowson, M.A.; Haney, O.R.; Reeves, H.W.; Aelion, C.M.; Ray, R.P.
1997-02-01
The design, performance, and analysis of a field method for quantifying contaminant mass-extraction rates and air-phase permeability at discrete vertical locations of the vadose zones are presented. The test configuration consists of a multiscreen extraction well and multilevel observation probes located in soil layers adjacent to the extraction well. For each level tested an inflatable packer system is used to pneumatically isolate a single screen in the extraction well, and a vacuum is applied to induce air flow through the screen. Test data include contaminant concentration and flow characteristics at the extraction well, and transient or steady-state pressure drawdown data at observation probes located at variable radii from the extraction well. The test method is applicable to the design of soil-vapor extraction (SVE) and bioventing remediation systems in a variety of geologic settings, particularly stratified soils. Application of the test method at a gasoline-polluted site located in the Piedmont physiographic region is described. Contaminant mass-extraction rates, expressed in terms of volatile hydrocarbons, varied from 0.16 to 14 kg/d.
PHYSICS OF POLARIZED SCATTERING AT MULTI-LEVEL ATOMIC SYSTEMS
Stenflo, J. O.
2015-03-01
The symmetric peak observed in linear polarization in the core of the solar sodium D{sub 1} line at 5896 Å has remained enigmatic since its discovery nearly two decades ago. One reason is that the theory of polarized scattering has not been experimentally tested for multi-level atomic systems in the relevant parameter domains, although the theory is continually being used for the interpretation of astrophysical observations. A laboratory experiment that was set up a decade ago to find out whether the D{sub 1} enigma is a problem of solar physics or quantum physics revealed that the D{sub 1} system has a rich polarization structure in situations where standard scattering theory predicts zero polarization, even when optical pumping of the m state populations of the hyperfine-split ground state is accounted for. Here we show that the laboratory results can be modeled in great quantitative detail if the theory is extended to include the coherences in both the initial and final states of the scattering process. Radiative couplings between the allowed dipole transitions generate coherences in the initial state. Corresponding coherences in the final state are then demanded by a phase closure selection rule. The experimental results for the well understood D{sub 2} line are used to constrain the two free parameters of the experiment, collision rate and optical depth, to suppress the need for free parameters when fitting the D{sub 1} results.
Natural Resource Monitoring of Rheum tanguticum by Multilevel Remote Sensing.
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 m(2) 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.
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...
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.
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.
Macdonald, James S P; Lavie, Nilli
2008-10-01
Although the perceptual load theory of attention has stimulated a great deal of research, evidence for the role of perceptual load in determining perception has typically relied on indirect measures that infer perception from distractor effects on reaction times or neural activity (see N. Lavie, 2005, for a review). Here we varied the level of perceptual load in a letter-search task and assessed its effect on the conscious perception of a search-irrelevant shape stimulus appearing in the periphery, using a direct measure of awareness (present/absent reports). Detection sensitivity (d') was consistently reduced with high, compared to low, perceptual load but was unaffected by the level of working memory load. Because alternative accounts in terms of expectation, memory, response bias, and goal-neglect due to the more strenuous high load task were ruled out, these experiments clearly demonstrate that high perceptual load determines conscious perception, impairing the ability to merely detect the presence of a stimulus--a phenomenon of load induced blindness.
ERIC Educational Resources Information Center
Macdonald, James S. P.; Lavie, Nilli
2008-01-01
Although the perceptual load theory of attention has stimulated a great deal of research, evidence for the role of perceptual load in determining perception has typically relied on indirect measures that infer perception from distractor effects on reaction times or neural activity (see N. Lavie, 2005, for a review). Here we varied the level of…
Transportation and handling loads
NASA Technical Reports Server (NTRS)
Ostrem, F. E.
1971-01-01
Criteria and recommended practices are presented for the prediction and verification of transportation and handling loads for the space vehicle structure and for monitoring these loads during transportation and handling of the vehicle or major vehicle segments. Elements of the transportation and handling systems, and the forcing functions and associated loads are described. The forcing functions for common carriers and typical handling devices are assessed, and emphasis is given to the assessment of loads at the points where the space vehicle is supported during transportation and handling. Factors which must be considered when predicting the loads include the transportation and handling medium; type of handling fixture; transport vehicle speed; types of terrain; weather (changes in pressure of temperature, wind, etc.); and dynamics of the transportation modes or handling devices (acceleration, deceleration, and rotations of the transporter or handling device).
Multilevel processes and cultural adaptation: Examples from past and present small-scale societies
Reyes-García, V.; Balbo, A. L.; Gomez-Baggethun, E.; Gueze, M.; Mesoudi, A.; Richerson, P.; Rubio-Campillo, X.; Ruiz-Mallén, I.; Shennan, S.
2016-01-01
Cultural adaptation has become central in the context of accelerated global change with authors increasingly acknowledging the importance of understanding multilevel processes that operate as adaptation takes place. We explore the importance of multilevel processes in explaining cultural adaptation by describing how processes leading to cultural (mis)adaptation are linked through a complex nested hierarchy, where the lower levels combine into new units with new organizations, functions, and emergent properties or collective behaviours. After a brief review of the concept of “cultural adaptation” from the perspective of cultural evolutionary theory and resilience theory, the core of the paper is constructed around the exploration of multilevel processes occurring at the temporal, spatial, social and political scales. We do so by examining small-scale societies’ case studies. In each section, we discuss the importance of the selected scale for understanding cultural adaptation and then present an example that illustrates how multilevel processes in the selected scale help explain observed patterns in the cultural adaptive process. We end the paper discussing the potential of modelling and computer simulation for studying multilevel processes in cultural adaptation. PMID:27774109
Sung, Yao-Ting; Chen, Ju-Ling; Cha, Ji-Her; Tseng, Hou-Chiang; Chang, Tao-Hsing; Chang, Kuo-En
2015-06-01
Multilevel linguistic features have been proposed for discourse analysis, but there have been few applications of multilevel linguistic features to readability models and also few validations of such models. Most traditional readability formulae are based on generalized linear models (GLMs; e.g., discriminant analysis and multiple regression), but these models have to comply with certain statistical assumptions about data properties and include all of the data in formulae construction without pruning the outliers in advance. The use of such readability formulae tends to produce a low text classification accuracy, while using a support vector machine (SVM) in machine learning can enhance the classification outcome. The present study constructed readability models by integrating multilevel linguistic features with SVM, which is more appropriate for text classification. Taking the Chinese language as an example, this study developed 31 linguistic features as the predicting variables at the word, semantic, syntax, and cohesion levels, with grade levels of texts as the criterion variable. The study compared four types of readability models by integrating unilevel and multilevel linguistic features with GLMs and an SVM. The results indicate that adopting a multilevel approach in readability analysis provides a better representation of the complexities of both texts and the reading comprehension process.
[Improving laser center wavelength detection accuracy based on multi-level combination prisms].
Liu, Xiao-Dong; Zhang, Zhi-Jie
2011-08-01
In order to improve the spectral resolution of birefringence prism under the conditions of ensuring the quality of interference fringes image, the system used multi-level combination prisms and designed the method of interferometer fringes splice. According to calculation of the interferometer fringes intensity of multi-level combination prisms, the optical path difference function and the spectrum resolution, the present paper analyzed that the least spectrum resolution is 2.875 cm(-1) in multi-level combination prisms of four prisms structure. The method of interferometer fringes splice was designed to splice the section interferometer fringes, and in experiment the size of multi-level combination prisms is 30 mm x 28 mm x 10 mm. The standard 635 nm laser for getting the interferometer fringes was dealed with. Experimental data show that the detection spectrum distribution of the 635.0 nm laser was distorted by the direct splicing of the interference fringes, while the detection spectrum distribution of the 635.0 nm laser was consistent with the standard spectrum by the method of interferometer fringes splice. So the method can effectively avoid spectrum distortion by interferometer fringes splice in multi-level combination prisms.
Researching the method of providing harmonicity to multi-level inverter
NASA Astrophysics Data System (ADS)
Taissariyeva, K. N.; Ilipbaeva, L.; Dzhobalaeva, G.
2016-09-01
In this work we consider the developed scheme of multi-level invertor, which is collected on IGBT transistors. Transistor switching, which provides harmonicity of output tension, is calculated on each level. For verification the settlement data, the imitating model of multilevel inverter was constructed in MatLab program. The output curve tension received at the exit of multilevel inverter's imitating model was spread out to harmonious components. It allowed investigating most precisely harmonious structure of the received multi-level inverter's tension curve. For ensuring output tension with a sinusoidal curve, researches and calculations of a corner of switching for each source of the multi-level inverter are conducted. Calculation of switching corner for each source for eight, twelve and twenty-six step single-phase inverters is carried out. For each step the necessary level of tension is provided, it carries out the harmonicity the whole inverter's output tension. Calculations were carried out in algorithm presented below, in this case for eight, twelve, and twenty-six step inverters.
A latent-variable marginal method for multi-level incomplete binary data.
Chen, Baojiang; Zhou, Xiao-Hua
2012-11-20
Incomplete multi-level data arise commonly in many clinical trials and observational studies. Because of multi-level variations in this type of data, appropriate data analysis should take these variations into account. A random effects model can allow for the multi-level variations by assuming random effects at each level, but the computation is intensive because high-dimensional integrations are often involved in fitting models. Marginal methods such as the inverse probability weighted generalized estimating equations can involve simple estimation computation, but it is hard to specify the working correlation matrix for multi-level data. In this paper, we introduce a latent variable method to deal with incomplete multi-level data when the missing mechanism is missing at random, which fills the gap between the random effects model and marginal models. Latent variable models are built for both the response and missing data processes to incorporate the variations that arise at each level. Simulation studies demonstrate that this method performs well in various situations. We apply the proposed method to an Alzheimer's disease study.
Cho, Sun-Joo; Cohen, Allan S; Bottge, Brian
2013-07-01
A multilevel latent transition analysis (LTA) with a mixture IRT measurement model (MixIRTM) is described for investigating the effectiveness of an intervention. The addition of a MixIRTM to the multilevel LTA permits consideration of both potential heterogeneity in students' response to instructional intervention as well as a methodology for assessing stage sequential change over time at both student and teacher levels. Results from an LTA-MixIRTM and multilevel LTA-MixIRTM were compared in the context of an educational intervention study. Both models were able to describe homogeneities in problem solving and transition patterns. However, ignoring a multilevel structure in LTA-MixIRTM led to different results in group membership assignment in empirical results. Results for the multilevel LTA-MixIRTM indicated that there were distinct individual differences in the different transition patterns. The students receiving the intervention treatment outscored their business as usual (i.e., control group) counterparts on the curriculum-based Fractions Computation test. In addition, 27.4 % of the students in the sample moved from the low ability student-level latent class to the high ability student-level latent class. Students were characterized differently depending on the teacher-level latent class.
NASA Astrophysics Data System (ADS)
Hagiwara, Makoto; Nishimura, Kazutoshi; Akagi, Hirofumi
This paper presents a medium-voltage motor drive with a three-phase modular multilevel PWM inverter and focuses on its control method and operating performance. This motor drive is particularly suitable for fans, blowers, pumps, and compressors, in which the load torque is proportional to the square of the rotating speed. Particular attention is paid to the dc-capacitor voltage fluctuation of each chopper-cell because it may affect the voltage rating of the power switching devices used. This paper describes the theoretical equations related to the amount of the voltage fluctuation. A downscaled model rated at 400V and 15kW is designed and built to confirm the validity and effectiveness of the nine-level (17-level in line-to-line) PWM inverter that is intended for use in medium-voltage motor drives to achieve energy savings.
On the Retrieval and Analysis of Multilevel Clouds
NASA Technical Reports Server (NTRS)
Baum, Bryan A.; Wielicki, Bruce A.
1992-01-01
An accurate satellite retrieval of cloud properties depends upon the detection and analysis of multilayered, overlapping cloud systems that surface observations show to be common. Multiple cloud layers are often found, for instance, in frontal situations, where cirrus overlays boundary layer convective cloud or low-to mid-level stratus cloud. Surface observers (Hahan et al., 1982) indicate that over ocean in the Northern Hemisphere between 30 deg. N and 60 deg. N, 51 percent of observations are of multilevel clouds. A satellite analysis by Coakley (1983) over the Pacific Ocean finds that more than 50 percent of 500 (250 sq km) frames exhibit evidence of multilayered cloud systems. The questions addressed in this study are the following: What error is introduced when inferring the cloud pressure from a Field-Of-View (FOV) that contains some arbitrary amount of transparent cloud overlaying a lower-level black cloud, such as stratus, by making the assumption that there is only a single cloud layer in the FOV, and what may be done to improve the cloud retrieval? The CO2 slicing methods (e.g. McCleese and Wilson, 1976; Smith and Platt, 1978; Chahine, 1974) have been shown to provide accurate means of inferring cirrus cloud altitude from passive infrared radiance measurements. The CO2 techniques have been applied to radiometric data from several instruments, notably the High Resolution Infrared Radiometric Sounder (HIRS/2, hereafter referred to as HIRS), the VISSR Atmospheric Sounder (VAS) (e.g., Menzel et al., 1983; Wylie and Menzel, 1989), and most recently to the High Resolution Interferometer Sounder (HIS) (Smith and Frey, 1990). The methods take advantage of the fact that infrared CO2 sounding channels spaced closely in wavenumber each have varying opacity to CO2, thereby causing each channel to be sensitive to a different level in the atmosphere. The techniques have been shown to be effective for single-layered, nonblack, mid- to high-level clouds such as cirrus
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
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
Statistical behaviour of adaptive multilevel splitting algorithms in simple models
NASA Astrophysics Data System (ADS)
Rolland, Joran; Simonnet, Eric
2015-02-01
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.
Statistical behaviour of adaptive multilevel splitting algorithms in simple models
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.
Longitudinal Multilevel Modeling of Facial Pain, Muscle Tension, and Stress.
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.
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.
Multi-level human evolution: ecological patterns in hominin phylogeny.
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.
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.
Multilevel analysis of air pollution and early childhood neurobehavioral development.
Lin, Ching-Chun; Yang, Shih-Kuan; Lin, Kuan-Chia; Ho, Wen-Chao; Hsieh, Wu-Shiun; Shu, Bih-Ching; Chen, Pau-Chung
2014-07-02
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.
Welfare state matters: a typological multilevel analysis of wealthy countries.
Chung, Haejoo; Muntaner, Carles
2007-02-01
Building on the social science literature, we hypothesized that population health indicators in wealthy industrialized countries are 'clustered' around welfare state regime types. We tested this hypothesis during a period of welfare state expansion from 1960 to 1994. We categorized data from 19 wealthy countries into 4 different types of welfare state regimes (Social Democratic, Christian Democratic, Liberal and Wage Earner Welfare States). Outcome variables were the infant mortality rate (IMR) and the low birth weight rate (LBW), obtained from the Organization of Economic Co-operation and Development (OECD) Health Data 2000 and from the United Nations Common Statistical Database (UNCSD). A two-level multilevel model was constructed, and fixed effects of welfare state were tested. Through the 39 years analyzed, Social Democratic countries exhibited a significantly better population health status, i.e., lower infant mortality rate and low birth weight rate, compared to other countries. Twenty percent of the difference in infant mortality rate among countries could be explained by the type of welfare state, and about 10% for low birth weight rate. The gap between Social Democracies and other countries widened over the 1990s. Our results confirm that countries exhibit distinctive levels of population health by welfare regime types even when adjusted by the level of economic development (GDP per capita) and intra-country correlations. It implies that countries, as groups, adopt similar policies or through any other ways, achieve similar level of health status. Proposed mechanisms of such process and suggestions for future research directions are presented in the discussion.
Women's status and depressive symptoms: a multilevel analysis.
Chen, Ying-Yeh; Subramanian, S V; Acevedo-Garcia, Doloros; Kawachi, Ichiro
2005-01-01
The effects of state-level women's status and autonomy on individual-level women's depressive symptoms were examined. We conducted a multi-level analysis of the 1991 longitudinal follow up of the 1988 National Maternal Infant Health Survey (NMIHS), with 7789 women nested within the fifty American states. State-level women's status was assessed by four composite indices measuring women's political participation, economic autonomy, employment & earnings, and reproductive rights. The main outcome measure was symptoms of depression (Center for Epidemiologic Studies Depression Scale, CES-D). The participants were a nationally representative stratified random sample of women in the USA aged between 17 and 40 years old who gave birth to live babies in 1988, were successfully contacted again in 1991 and provided complete information on depressive symptoms. Women who were younger, non-white, not currently married, less educated or had lower household income tended to report higher levels of depressive symptoms. Compared with states ranking low on the employment & earnings index, women residing in states that were high on the same index scored 0.85 points lower on the CES-D (p<0.01). Women who lived in states that were high on the economic autonomy index scored 0.83 points lower in depressive symptoms (p<0.01), compared with women who lived in states low on the same index. Finally, women who resided in states with high reproductive rights scored 0.62 points lower on the CES-D (p<0.05) compared with women who lived in states with lower reproductive rights. Gender inequality appears to contribute to depressive symptoms in women.
Are BMI and Sedentariness Correlated? A Multilevel Study in Children.
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
2015-07-16
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.
Are BMI and Sedentariness Correlated? A Multilevel Study in Children
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
Multilevel method for modeling large-scale networks.
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.
Antibiotic resistance shaping multi-level population biology of bacteria
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
Antibiotic resistance shaping multi-level population biology of bacteria.
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
Multilevel Analysis of Air Pollution and Early Childhood Neurobehavioral Development
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
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.
Load Balancing Scientific Applications
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.
Adibi, M.M.; Thorne, D.K. )
1988-08-01
Equipment overloads in an underground transmission network are caused by unscheduled outages. Repairs or replacements of damaged cables and/or transformers in urban areas are inherently difficult and time-consuming. Therefore, for overloads greatly in excess of short-time ratings, speed of load shedding is of paramount importance. Under such conditions, the system operator is faced with: recognizing the problem, determining the course of action and shedding the correct amount of load at the right locations. These tasks are difficult to perform, particularly under pressure of time. Reliance on pre-specified load shedding lists is not satisfactory since the load shedding lists do not necessarily match the amounts and locations of the required loads to be shed. Clearly, there has been a need for a local load shedding scheme, which in the first order of importance, would relieve the overloaded equipment within the time limits imposed by the equipment short-time ratings and in the second order of importance, would ''minimize'' the amount of load to be curtailed. This paper describes an approach which meets the dual objective, providing a practical solution to a difficult engineering/operating problem.
NASA Astrophysics Data System (ADS)
Colak, Ilhami; Kabalci, Ersan; Gazi Electrical Machines; Energy Control (Gemec) Group
This paper presents a digital signal processor (DSP) based algorithm to generate three-level output voltage using H-Bridge multilevel inverter (MLI). The developed sinusoidal pulse width modulation (SPWM) scheme is employed to achieve lower harmonic contents in the output waveforms of inverter. Since SPWM scheme does not utilize vector positions, any pre-calculated switching states are not required. In addition to this advantage of conventional SPWM, modulators eliminate only base band harmonics due to regular control scheme. Therefore, neglecting the side band harmonics limits the efficiency of SPWM scheme. The harmonics located in the side bands of carrier frequency are also eliminated by the enhanced SPWM scheme proposed in this study. The validation of the modelled system is verified with the total harmonic distortion (THD) analyzes. The control algorithm is developed using TMS320F2812 DSP that is a 32-bit fixed-point processor operating at 150 MHz. The simulation and experimental results are compared to previous studies. The THD ratios of phase voltages and currents are measured loading the inverter with a three- phase 3 kW asynchronous motor. The lowest THD ratios of voltage and current are obtained at 1.9% and 0.4%, respectively.
NASA Astrophysics Data System (ADS)
Shao, Meng; Pei, Jing; Yang, Bo
2013-12-01
With smaller pits and lands in multi-level optical disks using signal waveform modulation than those in DVD disks, the ISI and nonlinear attenuation of the read-out signal become more serious. One ordinary way is using an equalizer at sample rate 1/T, we proposed one method of designing the equalizer in fixed sample rate with digital interpolation. According to the analysis of the multi-level optical disk channel, we get the target frequency-response cure and implement it with seven order FIR filter. From the result of the read out experiment with multi-level optical disk, the clock of the RF signal could be recovered with the proposed equalizer.
Multilevel Modeling and Policy Development: Guidelines and Applications to Medical Travel
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
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.
Multilevel Weighted Support Vector Machine for Classification on Healthcare Data with Missing Values
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
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.
Self-compliance multilevel storage characteristic in HfO2-based device
NASA Astrophysics Data System (ADS)
Gao, Xiao-Ping; Fu, Li-Ping; Chen, Chuan-Bing; Yuan, Peng; Li, Ying-Tao
2016-10-01
In this paper, the self-compliance bipolar resistive switching characteristic of an HfO2-based memory device with Ag/HfO2/Au structure for multilevel storage is investigated. By applying a positive voltage, the dual-step set processes corresponding to three stable resistance states are observed in the device. The multilevel switching characteristics can still be observed after 48 hours. In addition, the resistance values of all the three states show negligible degradation over 104 s, which may be useful for the applications in nonvolatile multilevel storage. Project supported by the National Natural Science Foundation of China (Grant Nos. 61664001, 61574070, and 61306148) and the Application Research and Development Plan of Gansu Academy of Sciences, China (Grant Nos. 2015JK-11 and 2015JK-01).
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…
ERIC Educational Resources Information Center
Bulotsky-Shearer, Rebecca J.; Wen, Xiaoli; Faria, Ann-Marie; Hahs-Vaughn, Debbie L.; Korfmacher, Jon
2012-01-01
Guided by a developmental and ecological model, the study employed latent profile analysis to identify a multilevel typology of family involvement and Head Start classroom quality. Using the nationally representative Head Start Family and Child Experiences Survey (FACES 1997; N = 1870), six multilevel latent profiles were estimated, characterized…
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…
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…
Chen, Huaihou; Wang, Yuanjia; Paik, Myunghee Cho; Choi, H Alex
2013-10-01
Multilevel functional data is collected in many biomedical studies. For example, in a study of the effect of Nimodipine on patients with subarachnoid hemorrhage (SAH), patients underwent multiple 4-hour treatment cycles. Within each treatment cycle, subjects' vital signs were reported every 10 minutes. This data has a natural multilevel structure with treatment cycles nested within subjects and measurements nested within cycles. Most literature on nonparametric analysis of such multilevel functional data focus on conditional approaches using functional mixed effects models. However, parameters obtained from the conditional models do not have direct interpretations as population average effects. When population effects are of interest, we may employ marginal regression models. In this work, we propose marginal approaches to fit multilevel functional data through penalized spline generalized estimating equation (penalized spline GEE). The procedure is effective for modeling multilevel correlated generalized outcomes as well as continuous outcomes without suffering from numerical difficulties. We provide a variance estimator robust to misspecification of correlation structure. We investigate the large sample properties of the penalized spline GEE estimator with multilevel continuous data and show that the asymptotics falls into two categories. In the small knots scenario, the estimated mean function is asymptotically efficient when the true correlation function is used and the asymptotic bias does not depend on the working correlation matrix. In the large knots scenario, both the asymptotic bias and variance depend on the working correlation. We propose a new method to select the smoothing parameter for penalized spline GEE based on an estimate of the asymptotic mean squared error (MSE). We conduct extensive simulation studies to examine property of the proposed estimator under different correlation structures and sensitivity of the variance estimation to the choice
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.
Load research manual. Volume 3. Load research for advanced technologies
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.
2010-05-11
TNT - equivalent ) UNCLASSIFIED 8 Uncertainty in Charge Size & Location Underbody Blast Simulation Uncertainty in Vehicle Peak Acceleration Drop Tower...for Protection of Vehicle Occupants against Anti-Vehicular Landmine Effects.” North Atlantic Treaty Organisation, Neuilly-sur-Seine Cedex, France
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.
16. UPPER PASSENGER LOADING ZONE, NOTE LOADING ZONE BELOW WITH ...
16. UPPER PASSENGER LOADING ZONE, NOTE LOADING ZONE BELOW WITH TURN STILES - Jefferson National Expansion Memorial Arch, Mississippi River between Washington & Poplar Streets, Saint Louis, Independent City, MO
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 (VO{sub 2}) allows us to obtain a multilevel memory. We developed a Preisach model to explain the hysteretic radiative heat transfer between a VO{sub 2} 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.
Lauder, G R; White, M C
2005-05-01
Six children with cerebral palsy are presented who developed neuropathic pain following multilevel orthopedic surgery. This significant complication is previously unreported. The diagnosis and treatment options are reviewed. Treatment should be kept as simple and noninvasive as possible, and aim to enable physiotherapy to continue. Early recognition and interdisciplinary treatment is important to prevent a downward spiral of increasing pain and decreased function. A good outcome in respect of improved pain and functioning was achieved in five of these six children. It is our opinion that this complication should form part of informed consent for multilevel surgery and that anesthetists should be aware of this complication when managing postoperative pain control.
Multilevel solvers of first-order system least-squares for Stokes equations
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.
Vassallo, Rebecca; Durrant, Gabriele B; Smith, Peter W F; Goldstein, Harvey
2015-01-01
The paper investigates two different multilevel approaches, the multilevel cross-classified and the multiple-membership models, for the analysis of interviewer effects on wave non-response in longitudinal surveys. The models proposed incorporate both interviewer and area effects to account for the non-hierarchical structure, the influence of potentially more than one interviewer across waves and possible confounding of area and interviewer effects arising from the non-random allocation of interviewers across areas. The methods are compared by using a data set: the UK Family and Children Survey. PMID:25598587
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.
The effects of autonomy and empowerment on employee turnover: test of a multilevel model in teams.
Liu, Dong; Zhang, Shu; Wang, Lei; Lee, Thomas W
2011-11-01
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 collected from 817 employees on 115 teams indicates that psychological empowerment mediates the main effect of autonomy orientation and the interactive effect of autonomy support and its differentiation on a team member's voluntary turnover. The findings have meaningful implications for the turnover and self-determination literatures as well as for managers who endeavor to prevent voluntary turnover in teams.
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.
Multi-level SLIC superpixels segmentation method based on edge detection operator
NASA Astrophysics Data System (ADS)
Ni, Sen; Fu, Dongmei; Yang, Tao
2016-10-01
Simple linear iterative clustering (SLIC) super-pixel algorithm for its excellent performance and efficient border holding computational efficiency is widely used in image processing. But with the increase of the number of super-pixels, there will be a lot of redundancy in the image merging process. In this paper, we propose a multi-level super-pixels method based SLIC algorithm, which focuses on the target area to set up edge detection operator for generating multi-level super-pixels. Simulation results show that the proposed method ensures the accuracy of extraction and improves the computational efficiency.
Tabu search approaches for the multi-level warehouse layout problem with adjacency constraints
NASA Astrophysics Data System (ADS)
Zhang, G. Q.; Lai, K. K.
2010-08-01
A new multi-level warehouse layout problem, the multi-level warehouse layout problem with adjacency constraints (MLWLPAC), is investigated. The same item type is required to be located in adjacent cells, and horizontal and vertical unit travel costs are product dependent. An integer programming model is proposed to formulate the problem, which is NP hard. Along with a cube-per-order index policy based heuristic, the standard tabu search (TS), greedy TS, and dynamic neighbourhood based TS are presented to solve the problem. The computational results show that the proposed approaches can reduce the transportation cost significantly.
Multilevel coherent and direct-detection optical transmission: systems and applications
NASA Astrophysics Data System (ADS)
Betti, Silvello; De Marchis, Giancarlo; Iannone, Eugenio
1992-12-01
A review is presented of multilevel coherent and DD optical transmission systems with the aim of a comparative analysis between conventional modulation formats, such as N-PSK, N-QAM and new modulation/demodulation techniques, such as N-4QSK, N-SPSK and PM-DD. Besides the conceptual relevance of new multilevel modulation formats proposed to exploit the transmission characteristics of single-mode optical fibers, important applications can be foreseen like, for example, multiple parallel paths between network nodes or transmission between different processing units of supercomputers.
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.
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
Multilevel analysis of neuropathogenesis of neurocognitive impairment in HIV.
Levine, Andrew J; Soontornniyomkij, Virawudh; Achim, Cristian L; Masliah, Eliezer; Gelman, Benjamin B; Sinsheimer, Janet S; Singer, Elyse J; Moore, David J
2016-08-01
The neuropathogenesis of HIV-associated neurocognitive disorders (HAND) remains puzzling. We interrogated several levels of data (host genetic, histopathology, brain viral load, and neurocognitive) to identify histopathological changes most relevant to HAND. The design of the study is a clinicopathological study employing genetic association analyses. Data and brain tissue from 80 HIV-infected adults were used. Markers in monocyte chemoattractant protein-1 (MCP-1), interleukin 1-alpha (IL1-α), macrophage inflammatory protein 1-alpha (MIP1-α), DRD3, DRD2, and apolipoprotein E (ApoE) were genotyped. Microtubule associated protein 2 (MAP2), synaptophysin (SYP), human leukocyte antigen-DR (HLA-DR), glial fibrillary acidic protein (GFAP), amyloid beta (A-Beta), and ionized calcium-binding adaptor molecule-1 (Iba-1) immunoreactivity were quantified in the frontal cortex, putamen, and hippocampus. A composite score for each marker (mean of the three brain regions) was used. Neurocognitive functioning and other clinical variables were determined within 1 year of death. Brain HIV RNA viral load was available for a subset of cases. MAP2 and SYP proved most relevant to neurocognitive functioning. Immunoreactivity of these markers, as well as A-Beta and Iba-1, was correlated with brain HIV RNA viral load. Several genetic markers in combination with other factors predicted histopathology: HIV blood viral load, MIP1-α genotype, and DRD3 genotype predicted Iba-1 immunoreactivity; the duration of infection and IL1-α genotype predicted GFAP immunoreactivity; ApoE genotype and age at death predicted A-Beta immunoreactivity. These data indicate that HIV replication in the brain is the primary driving force leading to neuroinflammation and dysfunctional protein clearance, as reflected by A-Beta and Iba-1. Downstream to these changes are synaptodendritic degeneration, which is the immediate histopathological substrate of the neurocognitive impairment characteristic of HAND. These
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
NASA Technical Reports Server (NTRS)
Miller, Roy G
1927-01-01
The ultimate test of a load factor formula is experience. The chief advantages of a semi rational formula over arbitrary factors are that it fairs in between points of experience and it differentiates according to variables within a type. Structural failure of an airplane apparently safe according to the formula would call for a specific change in the formula. The best class of airplanes with which to check a load factor formula seems to be those which have experienced structural failure. Table I comprises a list of the airplanes which have experienced failure in flight traceable to the wing structure. The load factor by formula is observed to be greater than the designed strength in each case, without a single exception. Table II comprises the load factor by formula with the designed strength of a number of well-known service types. The formula indicates that by far the majority of these have ample structural strength. One case considered here in deriving a suitable formula is that of a heavy load carrier of large size and practically no reserve power.
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…
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…
Individual-Level Influences on Perceptions of Neighborhood Disorder: A Multilevel Analysis
ERIC Educational Resources Information Center
Latkin, Carl A.; German, Danielle; Hua, Wei; Curry, Aaron D.
2009-01-01
Health outcomes are associated with aggregate neighborhood measures and individual neighborhood perceptions. In this study, the authors sought to delineate individual, social network, and spatial factors that may influence perceptions of neighborhood disorder. Multilevel regression analysis showed that neighborhood perceptions were more negative…
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…
Very Efficient Methods for Multilevel Radiative Transfer in Atomic and Molecular Lines
NASA Astrophysics Data System (ADS)
Asensio Ramos, A.; Trujillo Bueno, J.
The development of fast numerical methods for multilevel radiative transfer (RT) applications often leads to important breakthroughs in astrophysics, because they allow the investigation of problems that could not be properly tackled using the methods previously available. Probably, the most familiar example is the so-called Multilevel Accelerated Λ-Iteration (MALI) technique of Rybicki & Hummer for the case of a local approximate operator, which is based on Jacobi iteration. However, there are superior operator-splitting methods, based on Gauss-Seidel (GS) and Successive Overrelaxation (SOR) iteration, which provide a dramatic increase in the speed with which non-LTE multilevel transfer problems can be solved in one, two and three-dimensional geometries. Such RT methods, which were introduced by Trujillo Bueno & Fabiani Bendicho ten years ago, are the main subject of the first part of this paper. We show in some detail how they can be applied for solving multilevel RT problems in spherical geometry, for both atomic and molecular line transitions. The second part of the article addresses the issue of the calculation of the molecular number densities when the approximation of instantaneous chemical equilibrium turns out to be inadequate, which happens to be the case whenever the dynamical time scales of the astrophysical plasma under consideration are much shorter than the time needed by the molecules to form.
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'…
Brief Report: Multilevel Analysis of School Smoking Policy and Pupil Smoking Behaviour in Wales
ERIC Educational Resources Information Center
Wiium, Nora; Burgess, Stephen; Moore, Laurence
2011-01-01
A multilevel analysis of cross-sectional data from a survey involving 1941 pupils (in grades 10 and 11) and policy indicators developed from interviews with staff from 45 secondary schools in Wales examined the hypotheses that pupil smoking prevalence would be associated with: restrictive staff and pupil smoking policies; dissemination of school…
ERIC Educational Resources Information Center
French, Kimberly A.; Kottke, Janet L.
2013-01-01
Multilevel modeling is used to examine the impact of teamwork interest and group extraversion on group satisfaction. Participants included 206 undergraduates in 65 groups who were surveyed at the beginning and end of a requisite term-length group project for an upper-division university course. We hypothesized that teamwork interest and both…
ERIC Educational Resources Information Center
Corbie-Smith, Giselle; Odeneye, Ebun; Banks, Bahby; Shandor Miles, Margaret; Roman Isler, Malika
2013-01-01
Minorities are disproportionately affected by HIV/AIDS in the rural Southeast; therefore, it is important to develop targeted, culturally appropriate interventions to support rural minority participation in HIV/AIDS research. Using intervention mapping, we developed a comprehensive multilevel intervention for service providers (SPs) and people…
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…
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…
Gibson, Abraham H; Kwapich, Christina L; Lang, Martha
2013-01-01
As multilevel selection theory has gained greater acceptance over the past quarter-century, scientists and scholars have shown an increased interest in the theory's historical antecedents. Despite this interest, however, the early twentieth century remains largely unexplored. It is generally assumed that biologists thought "naively" about evolutionary dynamics during this era, and that their attempts to explain biological phenomena often lacked sophistication. Now that several recent works have called attention to the complex relationship between biological individuality and the levels of selection, we believe it will prove instructive to revisit these early-twentieth-century biologists and reassess their criteria for biological individuality. Doing so reveals that they constructed a multilevel explanation of evolution that anticipated modern interpretations in several important ways. Though it is certainly true that most of these early biologists failed to recognize natural selection's pervasive agency, it is no less true that one of them, termite expert Alfred Emerson, artfully united the multilevel theory of "emergent evolution" with natural selection in a way that differs but little from the theory of multilevel selection that many scientists and scholars now promote. After reviewing the historical record, we place these early-twentieth-century biologists in their proper historical context, and we compare their interpretation of evolution with modern interpretations.
ERIC Educational Resources Information Center
Welch, Chiquitia L.; Roberts-Lewis, Amelia C.; Parker, Sharon
2009-01-01
The rise in female delinquency has resulted in large numbers of girls being incarcerated in Youth Development Centers (YDC). However, there are few gender specific treatment programs for incarcerated female adolescent offenders, particularly for those with a history of substance dependency. In this article, we present a Multi-level Risk Model…
A Multilevel Decomposition of School Performance Using Robust Nonparametric Frontier Techniques
ERIC Educational Resources Information Center
Thieme, Claudio; Prior, Diego; Tortosa-Ausina, Emili
2013-01-01
We propose a methodology for evaluating educational performance, from a multilevel perspective. We use partial frontier approaches to mitigate the influence of outliers and the curse of dimensionality. Our estimation considers idiosyncratic variables at the school, class, and student levels. Our model is applied to a sample of students in fourth…
Incorporating Mobility in Growth Modeling for Multilevel and Longitudinal Item Response Data.
Choi, In-Hee; Wilson, Mark
2016-01-01
Multilevel data often cannot be represented by the strict form of hierarchy typically assumed in multilevel modeling. A common example is the case in which subjects change their group membership in longitudinal studies (e.g., students transfer schools; employees transition between different departments). In this study, cross-classified and multiple membership models for multilevel and longitudinal item response data (CCMM-MLIRD) are developed to incorporate such mobility, focusing on students' school change in large-scale longitudinal studies. Furthermore, we investigate the effect of incorrectly modeling school membership in the analysis of multilevel and longitudinal item response data. Two types of school mobility are described, and corresponding models are specified. Results of the simulation studies suggested that appropriate modeling of the two types of school mobility using the CCMM-MLIRD yielded good recovery of the parameters and improvement over models that did not incorporate mobility properly. In addition, the consequences of incorrectly modeling the school effects on the variance estimates of the random effects and the standard errors of the fixed effects depended upon mobility patterns and model specifications. Two sets of large-scale longitudinal data are analyzed to illustrate applications of the CCMM-MLIRD for each type of school mobility.
Predicting Homework Effort: Support for a Domain-Specific, Multilevel Homework Model
ERIC Educational Resources Information Center
Trautwein, Ulrich; Ludtke, Oliver; Schnyder, Inge; Niggli, Alois
2006-01-01
According to the domain-specific, multilevel homework model proposed in the present study, students' homework effort is influenced by expectancy and value beliefs, homework characteristics, parental homework behavior, and conscientiousness. The authors used structural equation modeling and hierarchical linear modeling analyses to test the model in…
Commitment to the Study of International Business and Cultural Intelligence: A Multilevel Model
ERIC Educational Resources Information Center
Ramsey, Jase R.; Barakat, Livia L.; Aad, Amine Abi
2014-01-01
Adopting a multilevel theoretical framework, we examined how metacognitive and motivational cultural intelligence influence an individual's commitment to the study of international business (IB). Data from 292 undergraduate and graduate business students nested in 12 U.S. business school classes demonstrated that individuals' metacognitive and…
DIF Analysis with Multilevel Data: A Simulation Study Using the Latent Variable Approach
ERIC Educational Resources Information Center
Jin, Ying; Eason, Hershel
2016-01-01
The effects of mean ability difference (MAD) and short tests on the performance of various DIF methods have been studied extensively in previous simulation studies. Their effects, however, have not been studied under multilevel data structure. MAD was frequently observed in large-scale cross-country comparison studies where the primary sampling…
ERIC Educational Resources Information Center
Johnson, Ursula Y.; Hull, Darrell M.
2014-01-01
The authors examined science achievement growth at Grades 3, 5, and 8 and parent school involvement at the same time points using the Early Childhood Longitudinal Study-Kindergarten Class of 1998-1999. Data were analyzed using cross-classified multilevel latent growth curve modeling with time invariant and varying covariates. School-based…
Multilevel and Single-Level Models for Measured and Latent Variables When Data Are Clustered
ERIC Educational Resources Information Center
Stapleton, Laura M.; McNeish, Daniel M.; Yang, Ji Seung
2016-01-01
Multilevel models are often used to evaluate hypotheses about relations among constructs when data are nested within clusters (Raudenbush & Bryk, 2002), although alternative approaches are available when analyzing nested data (Binder & Roberts, 2003; Sterba, 2009). The overarching goal of this article is to suggest when it is appropriate…
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 through…
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...
Pedagogical Conditions of Multilevel Foreign Languages Teaching in Pedagogical Higher Education
ERIC Educational Resources Information Center
Kadakin, Vasily V.; Shukshina, Tatiana I.; Piskunova, Svetlana I.; Babushkina, Larisa E.; Falileev, Alexander E.
2016-01-01
This article is devoted to pedagogical conditions of multilevel foreign languages teaching in pedagogical higher education. The purpose of the study is to form the students' skills in foreign language mastering, to form the ability to operate independently and autonomously in this activity, both in the specific learning situation, and in the…
ERIC Educational Resources Information Center
Goosby, Bridget J.; Cheadle, Jacob E.
2009-01-01
We used multilevel covariance structure analysis to study the relationship between birth weight, family context and youth math and reading comprehension growth from approximately ages 5 through 14 within and between families. Using data from the National Longitudinal Survey of Youth Child Sample, we examined the relationship between birth weight…
GROUND WATER MONITORING AND SAMPLING: MULTI-LEVEL VERSUS TRADITIONAL METHODS WHATS WHAT?
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...
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…
On Multilevel Model Reliability Estimation From the Perspective of Structural Equation Modeling
ERIC Educational Resources Information Center
Raykov, Tenko; Marcoulides, George A.
2006-01-01
A covariance structure modeling perspective on reliability estimation can be used to construct a formal approach to estimation of reliability in multilevel models. This article presents a didactic discussion of the relation between a structural modeling procedure for scale reliability estimation and the notion of reliability of observed means in…
ERIC Educational Resources Information Center
Leckie, George; Baird, Jo-Anne
2011-01-01
This study examined rater effects on essay scoring in an operational monitoring system from England's 2008 national curriculum English writing test for 14-year-olds. We fitted two multilevel models and analyzed: (1) drift in rater severity effects over time; (2) rater central tendency effects; and (3) differences in rater severity and central…
Wolff, Matthew A.; Xia, Jianlin; Schulten, Klaus
2016-01-01
The multilevel summation method for calculating electrostatic interactions in molecular dynamics simulations constructs an approximation to a pairwise interaction kernel and its gradient, which can be evaluated at a cost that scales linearly with the number of atoms. The method smoothly splits the kernel into a sum of partial kernels of increasing range and decreasing variability with the longer-range parts interpolated from grids of increasing coarseness. Multilevel summation is especially appropriate in the context of dynamics and minimization, because it can produce continuous gradients. This article explores the use of B-splines to increase the accuracy of the multilevel summation method (for nonperiodic boundaries) without incurring additional computation other than a preprocessing step (whose cost also scales linearly). To obtain accurate results efficiently involves technical difficulties, which are overcome by a novel preprocessing algorithm. Numerical experiments demonstrate that the resulting method offers substantial improvements in accuracy and that its performance is competitive with an implementation of the fast multipole method in general and markedly better for Hamiltonian formulations of molecular dynamics. The improvement is great enough to establish multilevel summation as a serious contender for calculating pairwise interactions in molecular dynamics simulations. In particular, the method appears to be uniquely capable for molecular dynamics in two situations, nonperiodic boundary conditions and massively parallel computation, where the fast Fourier transform employed in the particle–mesh Ewald method falls short. PMID:27004867
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
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…
ERIC Educational Resources Information Center
Bradshaw, Catherine P.; Mitchell, Mary M.; O'Brennan, Lindsey M.; Leaf, Philip J.
2010-01-01
Although there is increasing awareness of the overrepresentation of ethic minority students--particularly Black students--in disciplinary actions, the extant research has rarely empirically examined potential factors that may contribute to these disparities. The current study used a multilevel modeling approach to examine factors at the child…
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…
School Climate for Academic Success: A Multilevel Analysis of School Climate and Student Outcomes
ERIC Educational Resources Information Center
Kwong, Darren; Davis, Jonathan Ryan
2015-01-01
This multilevel study examined the relationship between school climate and academic achievement. Using the Educational Longitudinal Survey (ELS, 2002), and a sample of 16,258 students and 1954 schools nationwide, we found that student-level perception of school climate--especially the student learning environment--was highly predictive of academic…
ERIC Educational Resources Information Center
Lu, Xingjiang; Yao, Chen; Zheng, Jianmin
2013-01-01
This paper focuses on the training of undergraduate students' innovation ability. On top of the theoretical framework of the Quality Function Deployment (QFD), we propose a teaching quality management model. Based on this model, we establish a multilevel decomposition indicator system, which integrates innovation ability characterized by four…
ERIC Educational Resources Information Center
Li, Fuzhong; Duncan, Terry E.; Harmer, Peter; Acock, Alan; Stoolmiller, Mike
1998-01-01
Discusses the utility of multilevel confirmatory factor analysis and hierarchical linear modeling methods in testing measurement models in which the underlying attribute may vary as a function of levels of observation. A real dataset is used to illustrate the two approaches and their comparability. (SLD)
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…
ERIC Educational Resources Information Center
Zhu, Xiaoshu
2013-01-01
The current study introduced a general modeling framework, multilevel mixture IRT (MMIRT) which detects and describes characteristics of population heterogeneity, while accommodating the hierarchical data structure. In addition to introducing both continuous and discrete approaches to MMIRT, the main focus of the current study was to distinguish…
ERIC Educational Resources Information Center
Jones, Leah; Totsika, Vasiliki; Hastings, Richard P.; Petalas, Michael A.
2013-01-01
Parenting a child with autism may differentially affect mothers and fathers. Existing studies of mother-father differences often ignore the interdependence of data within families. We investigated gender differences within-families using multilevel linear modeling. Mothers and fathers of children with autism (161 couples) reported on their own…
ERIC Educational Resources Information Center
Powell, Joshua E.; Powell, Anna L.; Petrosko, Joseph M.
2015-01-01
We surveyed public school educators on the workplace incivility and workplace bullying they experienced and obtained their ratings of the organizational climate of the school. We used multilevel modeling to determine the effects of individual-level and school-level predictors. Ratings of school climate were significantly related to incivility and…
Pons, Tracey; Shipton, Edward A
2011-04-01
There are no comparative randomised controlled trials of physiotherapy modalities for chronic low back and radicular pain associated with multilevel fusion. Physiotherapy-based rehabilitation to control pain and improve activation levels for persistent pain following multilevel fusion can be challenging. This is a case report of a 68-year-old man who was referred for physiotherapy intervention 10 months after a multilevel spinal fusion for spinal stenosis. He reported high levels of persistent postoperative pain with minimal activity as a consequence of his pain following the surgery. The physiotherapy interventions consisted of three phases of rehabilitation starting with pool exercise that progressed to land-based walking. These were all combined with transcutaneous electrical nerve stimulation (TENS) that was used consistently for up to 8 hours per day. As outcome measures, daily pain levels and walking distances were charted once the pool programme was completed (in the third phase). Phase progression was determined by shuttle test results. The pain level was correlated with the distance walked using linear regression over a 5-day average. Over a 5-day moving average, the pain level reduced and walking distance increased. The chart of recorded pain level and walking distance showed a trend toward decreased pain with the increased distance walked. In a patient undergoing multilevel lumbar fusion, the combined use of TENS and a progressive walking programme (from pool to land) reduced pain and increased walking distance. This improvement was despite poor medication compliance and a reported high level of postsurgical pain.
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...
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.
The Performance of Multilevel Growth Curve Models under an Autoregressive Moving Average Process
ERIC Educational Resources Information Center
Murphy, Daniel L.; Pituch, Keenan A.
2009-01-01
The authors examined the robustness of multilevel linear growth curve modeling to misspecification of an autoregressive moving average process. As previous research has shown (J. Ferron, R. Dailey, & Q. Yi, 2002; O. Kwok, S. G. West, & S. B. Green, 2007; S. Sivo, X. Fan, & L. Witta, 2005), estimates of the fixed effects were unbiased, and Type I…
Li, Baoyue; Bruyneel, Luk; Lesaffre, Emmanuel
2014-05-20
A traditional Gaussian hierarchical model assumes a nested multilevel structure for the mean and a constant variance at each level. We propose a Bayesian multivariate multilevel factor model that assumes a multilevel structure for both the mean and the covariance matrix. That is, in addition to a multilevel structure for the mean we also assume that the covariance matrix depends on covariates and random effects. This allows to explore whether the covariance structure depends on the values of the higher levels and as such models heterogeneity in the variances and correlation structure of the multivariate outcome across the higher level values. The approach is applied to the three-dimensional vector of burnout measurements collected on nurses in a large European study to answer the research question whether the covariance matrix of the outcomes depends on recorded system-level features in the organization of nursing care, but also on not-recorded factors that vary with countries, hospitals, and nursing units. Simulations illustrate the performance of our modeling approach.
ERIC Educational Resources Information Center
Huang, Francis L.; Cornell, Dewey G.
2016-01-01
Advances in multilevel modeling techniques now make it possible to investigate the psychometric properties of instruments using clustered data. Factor models that overlook the clustering effect can lead to underestimated standard errors, incorrect parameter estimates, and model fit indices. In addition, factor structures may differ depending on…
Multilevel Factor Analysis by Model Segregation: New Applications for Robust Test Statistics
ERIC Educational Resources Information Center
Schweig, Jonathan
2014-01-01
Measures of classroom environments have become central to policy efforts that assess school and teacher quality. This has sparked a wide interest in using multilevel factor analysis to test measurement hypotheses about classroom-level variables. One approach partitions the total covariance matrix and tests models separately on the…
Friendship and Alcohol Use in Early Adolescence: A Multilevel Social Network Approach
ERIC Educational Resources Information Center
Knecht, Andrea B.; Burk, William J.; Weesie, Jeroen; Steglich, Christian
2011-01-01
This study applies multilevel social network analytic techniques to examine processes of homophilic selection and social influence related to alcohol use among friends in early adolescence. Participants included 3,041 Dutch youth (M age =12 years, 49% female) from 120 classrooms in 14 schools. Three waves with 3-month intervals of friendship…
On the Usefulness of a Multilevel Logistic Regression Approach to Person-Fit Analysis
ERIC Educational Resources Information Center
Conijn, Judith M.; Emons, Wilco H. M.; van Assen, Marcel A. L. M.; Sijtsma, Klaas
2011-01-01
The logistic person response function (PRF) models the probability of a correct response as a function of the item locations. Reise (2000) proposed to use the slope parameter of the logistic PRF as a person-fit measure. He reformulated the logistic PRF model as a multilevel logistic regression model and estimated the PRF parameters from this…
Polytomous multilevel testlet models for testlet-based assessments with complex sampling designs.
Jiao, Hong; Zhang, Yuan
2015-02-01
Applications of standard item response theory models assume local independence of items and persons. This paper presents polytomous multilevel testlet models for dual dependence due to item and person clustering in testlet-based assessments with clustered samples. Simulation and survey data were analysed with a multilevel partial credit testlet model. This model was compared with three alternative models - a testlet partial credit model (PCM), multilevel PCM, and PCM - in terms of model parameter estimation. The results indicated that the deviance information criterion was the fit index that always correctly identified the true multilevel testlet model based on the quantified evidence in model selection, while the Akaike and Bayesian information criteria could not identify the true model. In general, the estimation model and the magnitude of item and person clustering impacted the estimation accuracy of ability parameters, while only the estimation model and the magnitude of item clustering affected the item parameter estimation accuracy. Furthermore, ignoring item clustering effects produced higher total errors in item parameter estimates but did not have much impact on the accuracy of ability parameter estimates, while ignoring person clustering effects yielded higher total errors in ability parameter estimates but did not have much effect on the accuracy of item parameter estimates. When both clustering effects were ignored in the PCM, item and ability parameter estimation accuracy was reduced.
2010-12-01
discontinuous coefficients on geometrically nonconforming substructures. Technical Report Serie A 634, Instituto de Matematica Pura e Aplicada, Brazil, 2009...Instituto de Matematica Pura e Aplicada, Brazil, 2010. submitted. [41] M. Dryja, M. V. Sarkis, and O. B. Widlund. Multilevel Schwarz methods for
Marginal Mean Weighting through Stratification: Adjustment for Selection Bias in Multilevel Data
ERIC Educational Resources Information Center
Hong, Guanglei
2010-01-01
Defining causal effects as comparisons between marginal population means, this article introduces marginal mean weighting through stratification (MMW-S) to adjust for selection bias in multilevel educational data. The article formally shows the inherent connections among the MMW-S method, propensity score stratification, and…
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…
ERIC Educational Resources Information Center
May, Henry
2006-01-01
In this article, a new method is presented and implemented for deriving a scale of socioeconomic status (SES) from international survey data using a multilevel Bayesian item response theory (IRT) model. The proposed model incorporates both international anchor items and nation-specific items and is able to (a) produce student family SES scores…
Kadengye, Damazo T; Cools, Wilfried; Ceulemans, Eva; Van den Noortgate, Wim
2012-06-01
Missing data, such as item responses in multilevel data, are ubiquitous in educational research settings. Researchers in the item response theory (IRT) context have shown that ignoring such missing data can create problems in the estimation of the IRT model parameters. Consequently, several imputation methods for dealing with missing item data have been proposed and shown to be effective when applied with traditional IRT models. Additionally, a nonimputation direct likelihood analysis has been shown to be an effective tool for handling missing observations in clustered data settings. This study investigates the performance of six simple imputation methods, which have been found to be useful in other IRT contexts, versus a direct likelihood analysis, in multilevel data from educational settings. Multilevel item response data were simulated on the basis of two empirical data sets, and some of the item scores were deleted, such that they were missing either completely at random or simply at random. An explanatory IRT model was used for modeling the complete, incomplete, and imputed data sets. We showed that direct likelihood analysis of the incomplete data sets produced unbiased parameter estimates that were comparable to those from a complete data analysis. Multiple-imputation approaches of the two-way mean and corrected item mean substitution methods displayed varying degrees of effectiveness in imputing data that in turn could produce unbiased parameter estimates. The simple random imputation, adjusted random imputation, item means substitution, and regression imputation methods seemed to be less effective in imputing missing item scores in multilevel data settings.
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...
ERIC Educational Resources Information Center
Wei, Youhua; Qu, Yanxuan
2014-01-01
For a testing program with frequent administrations, it is important to understand and monitor the stability and fluctuation of test performance across administrations. Different methods have been proposed for this purpose. This study explored the potential of using multilevel analysis to understand and monitor examinees' test performance across…
Four Types of School Environment: Multilevel Self-Management and Educational Quality
ERIC Educational Resources Information Center
Cheng, Yin Cheong; Cheung, Wing Ming
2004-01-01
How school-based management in the form of multilevel self-management is related to educational quality is a crucial issue in current educational reforms. An empirical study was conducted to explore this issue in a sample of 68 primary schools in Hong Kong. It was found that the school environment of sampled schools could be classified into 4…
Multilevel Analyses of School and Children's Characteristics Associated with Physical Activity
ERIC Educational Resources Information Center
Gomes, Thayse Natacha; dos Santos, Fernanda K.; Zhu, Weimo; Eisenmann, Joey; Maia, José A. R.
2014-01-01
Background: Children spend most of their awake time at school, and it is important to identify individual and school-level correlates of their physical activity (PA) levels. This study aimed to identify the between-school variability in Portuguese children PA and to investigate student and school PA correlates using multilevel modeling. Methods:…
Estimating Reliability of School-Level Scores Using Multilevel and Generalizability Theory Models
ERIC Educational Resources Information Center
Jeon, Min-Jeong; Lee, Guemin; Hwang, Jeong-Won; Kang, Sang-Jin
2009-01-01
The purpose of this study was to investigate the methods of estimating the reliability of school-level scores using generalizability theory and multilevel models. Two approaches, "student within schools" and "students within schools and subject areas," were conceptualized and implemented in this study. Four methods resulting from the combination…
Developing an Adequately Specified Model of State Level Student Achievement with Multilevel Data.
ERIC Educational Resources Information Center
Bernstein, Lawrence
Limitations of using linear, unilevel regression procedures in modeling student achievement are discussed. This study is a part of a broader study that is developing an empirically-based predictive model of variables associated with academic achievement from a multilevel perspective and examining the differences by which parameters are estimated…
ERIC Educational Resources Information Center
de Jong, Martijn G.; Steenkamp, Jan-Benedict E. M.
2010-01-01
We present a class of finite mixture multilevel multidimensional ordinal IRT models for large scale cross-cultural research. Our model is proposed for confirmatory research settings. Our prior for item parameters is a mixture distribution to accommodate situations where different groups of countries have different measurement operations, while…
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'…
Multilevel approach to the experimental study of plastic deformation of HCP-zirconium alloys
Poletika, T. M. E-mail: girs@ispms.tsc.ru; Girsova, S. L. E-mail: girs@ispms.tsc.ru
2014-11-14
A multilevel approach was developed to the experimental study of plastic deformation in anisotropic polycrystalline materials, using by way of an example HCP-Zr alloys. This allowed establishing the relationship and hierarchy of processes occurring at macro-, meso- and microscale levels in conditions of significant heterogeneity of plastic flow and of texture formation.
ERIC Educational Resources Information Center
Wang, Chee Keng John; Pyun, Do Young; Liu, Woon Chia; Lim, Boon San Coral; Li, Fuzhong
2013-01-01
Using a multilevel latent growth curve modeling (LGCM) approach, this study examined longitudinal change in levels of physical fitness performance over time (i.e. four years) in young adolescents aged from 12-13 years. The sample consisted of 6622 students from 138 secondary schools in Singapore. Initial analyses found between-school variation on…
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…
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.
ERIC Educational Resources Information Center
Schulz, Wolfram
Differences in student knowledge about democracy, institutions, and citizenship and students skills in interpreting political communication were studied through multilevel regression analysis of results from the second International Education Association (IEA) Study. This study provides data on 14-year-old students from 28 countries in Europe,…
ERIC Educational Resources Information Center
Cronley, Courtney; Patterson, David A.
2012-01-01
This study examined the effects of organizational culture on staff members' use of management information systems ("N" = 142) within homeless service organizations ("N" = 24), using a multilevel model. The Organizational Social Context Questionnaire was used to measure organizational culture, defined by three sub-constructs: (1) proficiency, (2)…
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'…
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…
ERIC Educational Resources Information Center
Wissink, Inge B.; Dekovic, Maja; Stams, Geert-Jan; Asscher, Jessica J.; Rutten, Esther; Zijlstra, Bonne J. H.
2014-01-01
This multilevel study examined the relationships between moral climate factors and prosocial as well as antisocial behaviors inside and outside the school (school misconduct, delinquent behavior, and vandalism). The moral climate factors were punishment-and victim-based moral orientation, relationships among students, and teacher-student…
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…
Multilevel Modeling in the Presence of Outliers: A Comparison of Robust Estimation Methods
ERIC Educational Resources Information Center
Finch, Holmes
2017-01-01
Multilevel models (MLMs) have proven themselves to be very useful in social science research, as data from a variety of sources is sampled such that individuals at level-1 are nested within clusters such as schools, hospitals, counseling centers, and business entities at level-2. MLMs using restricted maximum likelihood estimation (REML) provide…
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…
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…
ERIC Educational Resources Information Center
Netten, Andrea; Luyten, Hans; Droop, Mienke; Verhoeven, Ludo
2016-01-01
This study examined how linguistic and sociocultural diversity have an impact on the reading literacy outcomes of a representative sample of 3,549 first-language (L1) and 208 second-language (L2) fourth-grade students in the Netherlands. A multilevel modelling analysis was conducted using Progress in International Reading Literacy Study 2006 data…
A Multilevel Bi-Factor Framework for the Measurement of Instruction
ERIC Educational Resources Information Center
Kelcey, Ben; Carlisle, Joanne
2012-01-01
In this paper the authors briefly describe how features of the multilevel bi-factor model align with salient features of instruction. They then apply this framework to measure the extent to which teachers' instruction is supportive of vocabulary learning in second and third grade reading comprehension and vocabulary lessons. The results lend…
Level and Change of Bullying Behavior during High School: A Multilevel Growth Curve Analysis
ERIC Educational Resources Information Center
Nocentini, Annalaura; Menesini, Ersilia; Salmivalli, Christina
2013-01-01
The development of bullying behavior was examined across three years in a sample of 515 adolescents (46% females) from 41 classrooms. At time 1, the students were in grades 9 and 10 (mean age = 14.5 years; SD = 0.54). Results of a multilevel growth model showed that both baseline level and change of bullying varied significantly across individuals…
ERIC Educational Resources Information Center
Beretvas, S. Natasha; Walker, Cindy M.
2012-01-01
This study extends the multilevel measurement model to handle testlet-based dependencies. A flexible two-level testlet response model (the MMMT-2 model) for dichotomous items is introduced that permits assessment of differential testlet functioning (DTLF). A distinction is made between this study's conceptualization of DTLF and that of…
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…
Generalized multilevel function-on-scalar regression and principal component analysis.
Goldsmith, Jeff; Zipunnikov, Vadim; Schrack, Jennifer
2015-06-01
This manuscript considers regression models for generalized, multilevel functional responses: functions are generalized in that they follow an exponential family distribution and multilevel in that they are clustered within groups or subjects. This data structure is increasingly common across scientific domains and is exemplified by our motivating example, in which binary curves indicating physical activity or inactivity are observed for nearly 600 subjects over 5 days. We use a generalized linear model to incorporate scalar covariates into the mean structure, and decompose subject-specific and subject-day-specific deviations using multilevel functional principal components analysis. Thus, functional fixed effects are estimated while accounting for within-function and within-subject correlations, and major directions of variability within and between subjects are identified. Fixed effect coefficient functions and principal component basis functions are estimated using penalized splines; model parameters are estimated in a Bayesian framework using Stan, a programming language that implements a Hamiltonian Monte Carlo sampler. Simulations designed to mimic the application have good estimation and inferential properties with reasonable computation times for moderate datasets, in both cross-sectional and multilevel scenarios; code is publicly available. In the application we identify effects of age and BMI on the time-specific change in probability of being active over a 24-hour period; in addition, the principal components analysis identifies the patterns of activity that distinguish subjects and days within subjects.
Introduction to Multilevel Item Response Theory Analysis: Descriptive and Explanatory Models
ERIC Educational Resources Information Center
Sulis, Isabella; Toland, Michael D.
2017-01-01
Item response theory (IRT) models are the main psychometric approach for the development, evaluation, and refinement of multi-item instruments and scaling of latent traits, whereas multilevel models are the primary statistical method when considering the dependence between person responses when primary units (e.g., students) are nested within…
Multi-level 3D implementation of thermo-pneumatic pumping on centrifugal microfluidic CD platforms.
Thio, Tzer Hwai Gilbert; Ibrahim, Fatimah; Al-Faqheri, Wisam; Soin, Norhayati; Abdul Kahar, Maria Kahar Bador; Madou, Marc
2013-01-01
Thermo-pneumatic (TP) pumping is a method employing the principle of expanding heated air to transfer fluids back towards the CD center on the centrifugal microfluidic CD platform. While the TP features are easy to fabricate as no moving parts are involved, it consumes extra real estate on the CD, and because heating is involved, it introduces unnecessary heating to the fluids on the CD. To overcome these limitations, we introduce a multi-level 3D approach and implement forced convection heating. In a multi-level 3D CD, the TP features are relocated to a separate top level, while the microfluidic process remains on a lower bottom level. This allows for heat shielding of the fluids in the microfluidic process level, and also improve usage of space on the CD. To aid in future implementations of TP pumping on a multi-level 3D CD, studies on the effect of heat source setting, and the effect of positioning the TP feature (it distance from the CD center) on CD surface heating are also presented. In this work, we successfully demonstrate a multi-level 3D approach to implement TP pumping on the microfluidic CD platform.
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…
The Development of Multi-Level Audio-Visual Teaching Aids for Earth Science.
ERIC Educational Resources Information Center
Pitt, William D.
The project consisted of making a multi-level teaching film titled "Rocks and Minerals of the Ouachita Mountains," which runs for 25 minutes and is in color. The film was designed to be interesting to earth science students from junior high to college, and consists of dialogue combined with motion pictures of charts, sequential diagrams, outcrops,…
ERIC Educational Resources Information Center
Butner, Jonathan; Amazeen, Polemnia G.; Mulvey, Genna M.
2005-01-01
The authors present a dynamical multilevel model that captures changes over time in the bidirectional, potentially asymmetric influence of 2 cyclical processes. S. M. Boker and J. Graham's (1998) differential structural equation modeling approach was expanded to the case of a nonlinear coupled oscillator that is common in bimanual coordination…
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…
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…
Multi-Level Research on Youth Participation in the Haitian Reconstruction
ERIC Educational Resources Information Center
Pluim, Gary W. J.
2012-01-01
Research in comparative and international education routinely encounters exceptional research conditions. In this article, the author explores the particular issues he faced in his research on multi-level youth programs of the Haitian reconstruction. Through a vertical analysis of internationally sponsored programs, this study required special…
1992-01-01
Architecture" in Proceedings of the IEEE Symposium on Security and Privacy, pp. 360-368, Oakland, CA May 1990. 7. T.F. Keefe and W.T. Tsai, " Multiversion ...June 1990), pp. 593-607. 9. William T. Maimone and Ira B. Greenberg, "Single-Level Multiversion Schedulers for Multilevel Secure Database Systems" in
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 models…
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…
Community Social and Place Predictors of Sense of Community: A Multilevel and Longitudinal Analysis
ERIC Educational Resources Information Center
Long, D. Adam; Perkins, Douglas D.
2007-01-01
Sense of community (SOC) is empirically "unpacked" as a multilevel construct with place and social elements. SOC has been studied primarily at the individual level despite researchers acknowledging its effects at the community level. Little attention has been given to the roles of place and place attitudes in SOC. We argue that place and…
ERIC Educational Resources Information Center
Dedrick, Robert F.; Greenbaum, Paul E.
2011-01-01
Multilevel confirmatory factor analysis was used to evaluate the factor structure underlying the 12-item, three-factor "Interagency Collaboration Activities Scale" (ICAS) 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…
Random or Fixed Testlet Effects: A Comparison of Two Multilevel Testlet Models
ERIC Educational Resources Information Center
Chen, Tzu-An
2010-01-01
This simulation study compared the performance of two multilevel measurement testlet (MMMT) models: Beretvas and Walker's (2008) two-level MMMT model and Jiao, Wang, and Kamata's (2005) three-level model. Several conditions were manipulated (including testlet length, sample size, and the pattern of the testlet effects) to assess the impact on the…