Finite element analysis of 6 large PMMA skull reconstructions: A multi-criteria evaluation approach

PubMed Central

Ridwan-Pramana, Angela; Marcián, Petr; Borák, Libor; Narra, Nathaniel; Forouzanfar, Tymour; Wolff, Jan

2017-01-01

In this study 6 pre-operative designs for PMMA based reconstructions of cranial defects were evaluated for their mechanical robustness using finite element modeling. Clinical experience and engineering principles were employed to create multiple plan options, which were subsequently computationally analyzed for mechanically relevant parameters under 50N loads: stress, strain and deformation in various components of the assembly. The factors assessed were: defect size, location and shape. The major variable in the cranioplasty assembly design was the arrangement of the fixation plates. An additional study variable introduced was the location of the 50N load within the implant area. It was found that in smaller defects, it was simpler to design a symmetric distribution of plates and under limited variability in load location it was possible to design an optimal for expected loads. However, for very large defects with complex shapes, the variability in the load locations introduces complications to the intuitive design of the optimal assembly. The study shows that it can be beneficial to incorporate multi design computational analyses to decide upon the most optimal plan for a clinical case. PMID:28609471

Finite element analysis of 6 large PMMA skull reconstructions: A multi-criteria evaluation approach.

PubMed

Ridwan-Pramana, Angela; Marcián, Petr; Borák, Libor; Narra, Nathaniel; Forouzanfar, Tymour; Wolff, Jan

2017-01-01

In this study 6 pre-operative designs for PMMA based reconstructions of cranial defects were evaluated for their mechanical robustness using finite element modeling. Clinical experience and engineering principles were employed to create multiple plan options, which were subsequently computationally analyzed for mechanically relevant parameters under 50N loads: stress, strain and deformation in various components of the assembly. The factors assessed were: defect size, location and shape. The major variable in the cranioplasty assembly design was the arrangement of the fixation plates. An additional study variable introduced was the location of the 50N load within the implant area. It was found that in smaller defects, it was simpler to design a symmetric distribution of plates and under limited variability in load location it was possible to design an optimal for expected loads. However, for very large defects with complex shapes, the variability in the load locations introduces complications to the intuitive design of the optimal assembly. The study shows that it can be beneficial to incorporate multi design computational analyses to decide upon the most optimal plan for a clinical case.

Non-manipulation quantitative designs.

PubMed

Rumrill, Phillip D

2004-01-01

The article describes non-manipulation quantitative designs of two types, correlational and causal comparative studies. Both of these designs are characterized by the absence of random assignment of research participants to conditions or groups and non-manipulation of the independent variable. Without random selection or manipulation of the independent variable, no attempt is made to draw causal inferences regarding relationships between independent and dependent variables. Nonetheless, non-manipulation studies play an important role in rehabilitation research, as described in this article. Examples from the contemporary rehabilitation literature are included. Copyright 2004 IOS Press

A first principles based methodology for design of axial compressor configurations

NASA Astrophysics Data System (ADS)

Iyengar, Vishwas

Axial compressors are widely used in many aerodynamic applications. The design of an axial compressor configuration presents many challenges. Until recently, compressor design was done using 2-D viscous flow analyses that solve the flow field around cascades or in meridional planes or 3-D inviscid analyses. With the advent of modern computational methods it is now possible to analyze the 3-D viscous flow and accurately predict the performance of 3-D multistage compressors. It is necessary to retool the design methodologies to take advantage of the improved accuracy and physical fidelity of these advanced methods. In this study, a first-principles based multi-objective technique for designing single stage compressors is described. The study accounts for stage aerodynamic characteristics, rotor-stator interactions and blade elastic deformations. A parametric representation of compressor blades that include leading and trailing edge camber line angles, thickness and camber distributions was used in this study. A design of experiment approach is used to reduce the large combinations of design variables into a smaller subset. A response surface method is used to approximately map the output variables as a function of design variables. An optimized configuration is determined as the extremum of all extrema. This method has been applied to a rotor-stator stage similar to NASA Stage 35. The study has two parts: a preliminary study where a limited number of design variables were used to give an understanding of the important design variables for subsequent use, and a comprehensive application of the methodology where a larger, more complete set of design variables are used. The extended methodology also attempts to minimize the acoustic fluctuations at the rotor-stator interface by considering a rotor-wake influence coefficient (RWIC). Results presented include performance map calculations at design and off-design speed along with a detailed visualization of the flow field at design and off-design conditions. The present methodology provides a way to systematically screening through the plethora of design variables. By selecting the most influential design parameters and by optimizing the blade leading edge and trailing edge mean camber line angles, phenomenon's such as tip blockages, blade-to-blade shock structures and other loss mechanisms can be weakened or alleviated. It is found that these changes to the configuration can have a beneficial effect on total pressure ratio and stage adiabatic efficiency, thereby improving the performance of the axial compression system. Aeroacoustic benefits were found by minimizing the noise generating mechanisms associated with rotor wake-stator interactions. The new method presented is reliable, low time cost, and easily applicable to industry daily design optimization of turbomachinery blades.

Optimization of Variable-Depth Liner Configurations for Increased Broadband Noise Reduction

NASA Technical Reports Server (NTRS)

Jones, M. G.; Watson, W. R.; Nark, D. M.; Schiller, N. H.; Born, J. C.

2016-01-01

This paper employs three acoustic propagation codes to explore variable-depth liner configurations for the NASA Langley Grazing Flow Impedance Tube (GFIT). The initial study demonstrates that a variable impedance can acceptably be treated as a uniform impedance if the spatial extent over which this variable impedance occurs is less than one-third of a wavelength of the incident sound. A constrained optimization study is used to design a variable-depth liner and to select an optimization metric. It also provides insight regarding how much attenuation can be achieved with variable-depth liners. Another optimization study is used to design a liner with much finer chamber depth resolution for the Mach 0.0 and 0.3 test conditions. Two liners are designed based on spatial rearrangement of chambers from this liner to determine whether the order is critical. Propagation code predictions suggest this is not the case. Both liners are fabricated via additive manufacturing and tested in the GFIT for the Mach 0.0 condition. Predicted and measured attenuations compare favorably across the full frequency range. These results clearly suggest that the chambers can be arranged in any order, thus offering the potential for innovative liner designs to minimize depth and weight.

Optimization of a GO2/GH2 Impinging Injector Element

NASA Technical Reports Server (NTRS)

Tucker, P. Kevin; Shyy, Wei; Vaidyanathan, Rajkumar

2001-01-01

An injector optimization methodology, method i, is used to investigate optimal design points for a gaseous oxygen/gaseous hydrogen (GO2/GH2) impinging injector element. The unlike impinging element, a fuel-oxidizer- fuel (F-O-F) triplet, is optimized in terms of design variables such as fuel pressure drop, (Delta)P(sub f), oxidizer pressure drop, (Delta)P(sub o), combustor length, L(sub comb), and impingement half-angle, alpha, for a given mixture ratio and chamber pressure. Dependent variables such as energy release efficiency, ERE, wall heat flux, Q(sub w), injector heat flux, Q(sub inj), relative combustor weight, W(sub rel), and relative injector cost, C(sub rel), are calculated and then correlated with the design variables. An empirical design methodology is used to generate these responses for 163 combinations of input variables. Method i is then used to generate response surfaces for each dependent variable. Desirability functions based on dependent variable constraints are created and used to facilitate development of composite response surfaces representing some, or all, of the five dependent variables in terms of the input variables. Three examples illustrating the utility and flexibility of method i are discussed in detail. First, joint response surfaces are constructed by sequentially adding dependent variables. Optimum designs are identified after addition of each variable and the effect each variable has on the design is shown. This stepwise demonstration also highlights the importance of including variables such as weight and cost early in the design process. Secondly, using the composite response surface which includes all five dependent variables, unequal weights are assigned to emphasize certain variables relative to others. Here, method i is used to enable objective trade studies on design issues such as component life and thrust to weight ratio. Finally, specific variable weights are further increased to illustrate the high marginal cost of realizing the last increment of injector performance and thruster weight.

Intrinsic movement variability at work. How long is the path from motor control to design engineering?

PubMed

Gaudez, C; Gilles, M A; Savin, J

2016-03-01

For several years, increasing numbers of studies have highlighted the existence of movement variability. Before that, it was neglected in movement analysis and it is still almost completely ignored in workstation design. This article reviews motor control theories and factors influencing movement execution, and indicates how intrinsic movement variability is part of task completion. These background clarifications should help ergonomists and workstation designers to gain a better understanding of these concepts, which can then be used to improve design tools. We also question which techniques--kinematics, kinetics or muscular activity--and descriptors are most appropriate for describing intrinsic movement variability and for integration into design tools. By this way, simulations generated by designers for workstation design should be closer to the real movements performed by workers. This review emphasises the complexity of identifying, describing and processing intrinsic movement variability in occupational activities. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Multidisciplinary design optimization using genetic algorithms

NASA Technical Reports Server (NTRS)

Unal, Resit

1994-01-01

Multidisciplinary design optimization (MDO) is an important step in the conceptual design and evaluation of launch vehicles since it can have a significant impact on performance and life cycle cost. The objective is to search the system design space to determine values of design variables that optimize the performance characteristic subject to system constraints. Gradient-based optimization routines have been used extensively for aerospace design optimization. However, one limitation of gradient based optimizers is their need for gradient information. Therefore, design problems which include discrete variables can not be studied. Such problems are common in launch vehicle design. For example, the number of engines and material choices must be integer values or assume only a few discrete values. In this study, genetic algorithms are investigated as an approach to MDO problems involving discrete variables and discontinuous domains. Optimization by genetic algorithms (GA) uses a search procedure which is fundamentally different from those gradient based methods. Genetic algorithms seek to find good solutions in an efficient and timely manner rather than finding the best solution. GA are designed to mimic evolutionary selection. A population of candidate designs is evaluated at each iteration, and each individual's probability of reproduction (existence in the next generation) depends on its fitness value (related to the value of the objective function). Progress toward the optimum is achieved by the crossover and mutation operations. GA is attractive since it uses only objective function values in the search process, so gradient calculations are avoided. Hence, GA are able to deal with discrete variables. Studies report success in the use of GA for aircraft design optimization studies, trajectory analysis, space structure design and control systems design. In these studies reliable convergence was achieved, but the number of function evaluations was large compared with efficient gradient methods. Applicaiton of GA is underway for a cost optimization study for a launch-vehicle fuel-tank and structural design of a wing. The strengths and limitations of GA for launch vehicle design optimization is studied.

SOURCES OF VARIABILITY IN BASELINE GENE EXPRESSION IN RAT LIVER AND KIDNEY

EPA Science Inventory

Toxicogenomic studies are typically variable in design, but the impact of variations in study design and conduct on control animal gene expression has not been well characterized. A working group of the Health and Environmental Sciences Institute (HESI) Technical Committee on the...

Multidisciplinary design of a rocket-based combined cycle SSTO launch vehicle using Taguchi methods

NASA Technical Reports Server (NTRS)

Olds, John R.; Walberg, Gerald D.

1993-01-01

Results are presented from the optimization process of a winged-cone configuration SSTO launch vehicle that employs a rocket-based ejector/ramjet/scramjet/rocket operational mode variable-cycle engine. The Taguchi multidisciplinary parametric-design method was used to evaluate the effects of simultaneously changing a total of eight design variables, rather than changing them one at a time as in conventional tradeoff studies. A combination of design variables was in this way identified which yields very attractive vehicle dry and gross weights.

An Analysis of a Contingency Program on Designated Drivers at a College Bar

ERIC Educational Resources Information Center

Kazbour, Richard R.; Bailey, Jon S.

2010-01-01

The present study evaluated the effects of prompts and incentives on designated drivers in a bar. We defined the dependent variable as the percentage of customers either functioning as or riding with a designated driver. We used an ABCA design to evaluate the effectiveness of prompts and incentives on the dependent variable. Results indicated that…

An analysis of the relationship of seven selected variables to State Board Test Pool Examination performance of the University of Tennessee, Knoxville, College of Nursing.

PubMed

Sharp, T G

1984-02-01

The study was designed to determine whether any one of seven selected variables or a combination of the variables is predictive of performance on the State Board Test Pool Examination. The selected variables studied were: high school grade point average (HSGPA), The University of Tennessee, Knoxville, College of Nursing grade point average (GPA), and American College Test Assessment (ACT) standard scores (English, ENG; mathematics, MA; social studies, SS; natural sciences, NSC; composite, COMP). Data utilized were from graduates of the baccalaureate program of The University of Tennessee, Knoxville, College of Nursing from 1974 through 1979. The sample of 322 was selected from a total population of 572. The Statistical Analysis System (SAS) was designed to accomplish analysis of the predictive relationship of each of the seven selected variables to State Board Test Pool Examination performance (result of pass or fail), a stepwise discriminant analysis was designed for determining the predictive relationship of the strongest combination of the independent variables to overall State Board Test Pool Examination performance (result of pass or fail), and stepwise multiple regression analysis was designed to determine the strongest predictive combination of selected variables for each of the five subexams of the State Board Test Pool Examination. The selected variables were each found to be predictive of SBTPE performance (result of pass or fail). The strongest combination for predicting SBTPE performance (result of pass or fail) was found to be GPA, MA, and NSC.

Multiple and variable speed electrical generator systems for large wind turbines

NASA Technical Reports Server (NTRS)

Andersen, T. S.; Hughes, P. S.; Kirschbaum, H. S.; Mutone, G. A.

1982-01-01

A cost effective method to achieve increased wind turbine generator energy conversion and other operational benefits through variable speed operation is presented. Earlier studies of multiple and variable speed generators in wind turbines were extended for evaluation in the context of a specific large sized conceptual design. System design and simulation have defined the costs and performance benefits which can be expected from both two speed and variable speed configurations.

Predictors of Achievement When Virtual Manipulatives Are Used for Mathematics Instruction

ERIC Educational Resources Information Center

Moyer-Packenham, Patricia S.; Baker, Joseph; Westenskow, Arla; Anderson-Pence, Katie L.; Shumway, Jessica F.; Jordan, Kerry E.

2014-01-01

The purpose of this study was to determine variables that predict performance when virtual manipulatives are used for mathematics instruction. This study used a quasi-experimental design. This design was used to determine variables that predict student performance on tests of fraction knowledge for third- and fourth-grade students in two treatment…

Variable Mach number design approach for a parallel waverider with a wide-speed range based on the osculating cone theory

NASA Astrophysics Data System (ADS)

Zhao, Zhen-tao; Huang, Wei; Li, Shi-Bin; Zhang, Tian-Tian; Yan, Li

2018-06-01

In the current study, a variable Mach number waverider design approach has been proposed based on the osculating cone theory. The design Mach number of the osculating cone constant Mach number waverider with the same volumetric efficiency of the osculating cone variable Mach number waverider has been determined by writing a program for calculating the volumetric efficiencies of waveriders. The CFD approach has been utilized to verify the effectiveness of the proposed approach. At the same time, through the comparative analysis of the aerodynamic performance, the performance advantage of the osculating cone variable Mach number waverider is studied. The obtained results show that the osculating cone variable Mach number waverider owns higher lift-to-drag ratio throughout the flight profile when compared with the osculating cone constant Mach number waverider, and it has superior low-speed aerodynamic performance while maintaining nearly the same high-speed aerodynamic performance.

Time-Structured and Net Intraindividual Variability: Tools for Examining the Development of Dynamic Characteristics and Processes

PubMed Central

Ram, Nilam; Gerstorf, Denis

2009-01-01

The study of intraindividual variability is the study of fluctuations, oscillations, adaptations, and “noise” in behavioral outcomes that manifest on micro-time scales. This paper provides a descriptive frame for the combined study of intraindividual variability and aging/development. At the conceptual level, we highlight that the study of intraindividual variability provides access to dynamic characteristics – construct-level descriptions of individuals' capacities for change (e.g., lability), and dynamic processes – the systematic changes individuals' exhibit in response to endogenous and exogenous influences (e.g., regulation). At the methodological level, we review how quantifications of net intraindividual variability (e.g., iSD) and models of time-structured intraindividual variability (e.g., time-series) are being used to measure and describe dynamic characteristics and processes. At the research design level, we point to the benefits of measurement burst study designs, wherein data are obtained across multiple time scales, for the study of development. PMID:20025395

Structural Optimization of a Force Balance Using a Computational Experiment Design

NASA Technical Reports Server (NTRS)

Parker, P. A.; DeLoach, R.

2002-01-01

This paper proposes a new approach to force balance structural optimization featuring a computational experiment design. Currently, this multi-dimensional design process requires the designer to perform a simplification by executing parameter studies on a small subset of design variables. This one-factor-at-a-time approach varies a single variable while holding all others at a constant level. Consequently, subtle interactions among the design variables, which can be exploited to achieve the design objectives, are undetected. The proposed method combines Modern Design of Experiments techniques to direct the exploration of the multi-dimensional design space, and a finite element analysis code to generate the experimental data. To efficiently search for an optimum combination of design variables and minimize the computational resources, a sequential design strategy was employed. Experimental results from the optimization of a non-traditional force balance measurement section are presented. An approach to overcome the unique problems associated with the simultaneous optimization of multiple response criteria is described. A quantitative single-point design procedure that reflects the designer's subjective impression of the relative importance of various design objectives, and a graphical multi-response optimization procedure that provides further insights into available tradeoffs among competing design objectives are illustrated. The proposed method enhances the intuition and experience of the designer by providing new perspectives on the relationships between the design variables and the competing design objectives providing a systematic foundation for advancements in structural design.

Experimental investigation of terahertz quantum cascade laser with variable barrier heights

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Aiting; Vijayraghavan, Karun; Belkin, Mikhail A., E-mail: mbelkin@ece.utexas.edu

2014-04-28

We report an experimental study of terahertz quantum cascade lasers with variable barrier heights based on the Al{sub x}Ga{sub 1–x}As/GaAs material system. Two new designs are developed based on semiclassical ensemble Monte Carlo simulations using state-of-the-art Al{sub 0.15}Ga{sub 0.85}As/GaAs three-quantum-well resonant phonon depopulation active region design as a reference. The new designs achieved maximum lasing temperatures of 188 K and 172 K, as compared to the maximum lasing temperature of 191 K for the reference structure. These results demonstrate that terahertz quantum cascade laser designs with variable barrier heights provide a viable alternative to the traditional active region designs with fixed barrier composition.more » Additional design space offered by using variable barriers may lead to future improvements in the terahertz quantum cascade laser performance.« less

Engine design considerations for 2nd generation supersonic transports

NASA Technical Reports Server (NTRS)

Howlett, R. A.

1975-01-01

The environmental and economic goals projected for advanced supersonic transports will require revolutionary improvements in propulsion systems. Variable cycle engine concepts that incorporate unique components and advanced technologies show promise in meeting these goals. Pratt & Whitney Aircraft is conducting conceptual design studies of variable cycle engine concepts under NASA sponsorship. This paper reviews some of the design considerations for these engine concepts. Emphasis is placed on jet noise abatement, reduction of emissions, performance improvements, installation considerations, hot-section characteristics and control system requirements. Two representative variable cycle engine concepts that incorporate these basic design considerations are described.

Multi-point Adjoint-Based Design of Tilt-Rotors in a Noninertial Reference Frame

NASA Technical Reports Server (NTRS)

Jones, William T.; Nielsen, Eric J.; Lee-Rausch, Elizabeth M.; Acree, Cecil W.

2014-01-01

Optimization of tilt-rotor systems requires the consideration of performance at multiple design points. In the current study, an adjoint-based optimization of a tilt-rotor blade is considered. The optimization seeks to simultaneously maximize the rotorcraft figure of merit in hover and the propulsive efficiency in airplane-mode for a tilt-rotor system. The design is subject to minimum thrust constraints imposed at each design point. The rotor flowfields at each design point are cast as steady-state problems in a noninertial reference frame. Geometric design variables used in the study to control blade shape include: thickness, camber, twist, and taper represented by as many as 123 separate design variables. Performance weighting of each operational mode is considered in the formulation of the composite objective function, and a build up of increasing geometric degrees of freedom is used to isolate the impact of selected design variables. In all cases considered, the resulting designs successfully increase both the hover figure of merit and the airplane-mode propulsive efficiency for a rotor designed with classical techniques.

Combined model of intrinsic and extrinsic variability for computational network design with application to synthetic biology.

PubMed

Toni, Tina; Tidor, Bruce

2013-01-01

Biological systems are inherently variable, with their dynamics influenced by intrinsic and extrinsic sources. These systems are often only partially characterized, with large uncertainties about specific sources of extrinsic variability and biochemical properties. Moreover, it is not yet well understood how different sources of variability combine and affect biological systems in concert. To successfully design biomedical therapies or synthetic circuits with robust performance, it is crucial to account for uncertainty and effects of variability. Here we introduce an efficient modeling and simulation framework to study systems that are simultaneously subject to multiple sources of variability, and apply it to make design decisions on small genetic networks that play a role of basic design elements of synthetic circuits. Specifically, the framework was used to explore the effect of transcriptional and post-transcriptional autoregulation on fluctuations in protein expression in simple genetic networks. We found that autoregulation could either suppress or increase the output variability, depending on specific noise sources and network parameters. We showed that transcriptional autoregulation was more successful than post-transcriptional in suppressing variability across a wide range of intrinsic and extrinsic magnitudes and sources. We derived the following design principles to guide the design of circuits that best suppress variability: (i) high protein cooperativity and low miRNA cooperativity, (ii) imperfect complementarity between miRNA and mRNA was preferred to perfect complementarity, and (iii) correlated expression of mRNA and miRNA--for example, on the same transcript--was best for suppression of protein variability. Results further showed that correlations in kinetic parameters between cells affected the ability to suppress variability, and that variability in transient states did not necessarily follow the same principles as variability in the steady state. Our model and findings provide a general framework to guide design principles in synthetic biology.

Combined Model of Intrinsic and Extrinsic Variability for Computational Network Design with Application to Synthetic Biology

PubMed Central

Toni, Tina; Tidor, Bruce

2013-01-01

Biological systems are inherently variable, with their dynamics influenced by intrinsic and extrinsic sources. These systems are often only partially characterized, with large uncertainties about specific sources of extrinsic variability and biochemical properties. Moreover, it is not yet well understood how different sources of variability combine and affect biological systems in concert. To successfully design biomedical therapies or synthetic circuits with robust performance, it is crucial to account for uncertainty and effects of variability. Here we introduce an efficient modeling and simulation framework to study systems that are simultaneously subject to multiple sources of variability, and apply it to make design decisions on small genetic networks that play a role of basic design elements of synthetic circuits. Specifically, the framework was used to explore the effect of transcriptional and post-transcriptional autoregulation on fluctuations in protein expression in simple genetic networks. We found that autoregulation could either suppress or increase the output variability, depending on specific noise sources and network parameters. We showed that transcriptional autoregulation was more successful than post-transcriptional in suppressing variability across a wide range of intrinsic and extrinsic magnitudes and sources. We derived the following design principles to guide the design of circuits that best suppress variability: (i) high protein cooperativity and low miRNA cooperativity, (ii) imperfect complementarity between miRNA and mRNA was preferred to perfect complementarity, and (iii) correlated expression of mRNA and miRNA – for example, on the same transcript – was best for suppression of protein variability. Results further showed that correlations in kinetic parameters between cells affected the ability to suppress variability, and that variability in transient states did not necessarily follow the same principles as variability in the steady state. Our model and findings provide a general framework to guide design principles in synthetic biology. PMID:23555205

Ergonomic evaluation of interior design of Shoka vehicle and proposing recommendations for improvement.

PubMed

Mazloumi, Adel; Mohammadreze, Fallah

2012-01-01

One of the applications of ergonomics disciplinary is designing driver workstation compatible to users' characteristics. The aim of this study was evaluation of interior design of Shoka vehicle with respect to the accommodation for Iranian population and proposing suggestions for customizing design of this vehicle. This study was a descriptive-analytical study conducted among thirty men from Iranian drivers population in 5, 50, 95 percentiles of the stature variable. Objective variables related to the occupant packaging and vehicle visual aspects including anthropometric variables, frontal, lateral, and side view and so on were investigated first. Then, subjective variables related to the driver mental workload and body comfort discomfort were studied using BMDMW and comfort questionnaires during 2-hour driving trial sessions. Occupant packaging variables and hand-arm angle showed the least accommodation percent (%53). Seating angles showed low accommodation as well (%73). Among three percentile groups there were no significant differences between the mean values of mental workload during two hours driving task. And, the mean value related to the comfort discomfort was 3.9 during driving sessions. Considering the findings in this study, it can be conclude that seating angles need correction and optimization. Taking mental workload results into account, it can be concluded that the interior design of the studied car had no influence on drivers' mental workload. From the aspect of comfort discomfort, Shoka vehicle showed neutral state among drivers. Optimizing seating angles, decreasing vibration, correcting stiffness of seating pan are suggested for customization of the ergonomics aspect of this vehicle.

Variable-Speed Power-Turbine for the Large Civil Tilt Rotor

NASA Technical Reports Server (NTRS)

Suchezky, Mark; Cruzen, G. Scott

2012-01-01

Turbine design concepts were studied for application to a large civil tiltrotor transport aircraft. The concepts addressed the need for high turbine efficiency across the broad 2:1 turbine operating speed range representative of the notional mission for the aircraft. The study focused on tailoring basic turbine aerodynamic design design parameters to avoid the need for complex, heavy, and expensive variable geometry features. The results of the study showed that good turbine performance can be achieved across the design speed range if the design focuses on tailoring the aerodynamics for good tolerance to large swings in incidence, as opposed to optimizing for best performance at the long range cruise design point. A rig design configuration and program plan are suggested for a dedicated experiment to validate the proposed approach.

Vibration Analysis of a Split Path Gearbox

NASA Technical Reports Server (NTRS)

Krantz, Timothy L.; Rashidi, Majid

1995-01-01

Split path gearboxes can be attractive alternatives to the common planetary designs for rotorcraft, but because they have seen little use, they are relatively high risk designs. To help reduce the risk of fielding a rotorcraft with a split path gearbox, the vibration and dynamic characteristics of such a gearbox were studied. A mathematical model was developed by using the Lagrangian method, and it was applied to study the effect of three design variables on the natural frequencies and vibration energy of the gearbox. The first design variable, shaft angle, had little influence on the natural frequencies. The second variable, mesh phasing, had a strong effect on the levels of vibration energy, with phase angles of 0 deg and 180 deg producing low vibration levels. The third design variable, the stiffness of the shafts connecting the spur gears to the helical pinions, strongly influenced the natural frequencies of some of the vibration modes, including two of the dominant modes. We found that, to achieve the lowest level of vibration energy, the natural frequencies of these two dominant modes should be less than those of the main excitation sources.

Understanding the significance variables for fabrication of fish gelatin nanoparticles by Plackett-Burman design

NASA Astrophysics Data System (ADS)

Subara, Deni; Jaswir, Irwandi; Alkhatib, Maan Fahmi Rashid; Noorbatcha, Ibrahim Ali

2018-01-01

The aim of this experiment is to screen and to understand the process variables on the fabrication of fish gelatin nanoparticles by using quality-design approach. The most influencing process variables were screened by using Plackett-Burman design. Mean particles size, size distribution, and zeta potential were found in the range 240±9.76 nm, 0.3, and -9 mV, respectively. Statistical results explained that concentration of acetone, pH of solution during precipitation step and volume of cross linker had a most significant effect on particles size of fish gelatin nanoparticles. It was found that, time and chemical consuming is lower than previous research. This study revealed the potential of quality-by design in understanding the effects of process variables on the fish gelatin nanoparticles production.

Predicting Eight Grade Students' Equation Solving Performances via Concepts of Variable and Equality

ERIC Educational Resources Information Center

Ertekin, Erhan

2017-01-01

This study focused on how two algebraic concepts- equality and variable- predicted 8th grade students' equation solving performance. In this study, predictive design as a correlational research design was used. Randomly selected 407 eight-grade students who were from the central districts of a city in the central region of Turkey participated in…

Design study of a continuously variable roller cone traction CVT for electric vehicles

NASA Technical Reports Server (NTRS)

Mccoin, D. K.; Walker, R. D.

1980-01-01

Continuously variable ratio transmissions (CVT) featuring cone and roller traction elements and computerized controls are studied. The CVT meets or exceeds all requirements set forth in the design criteria. Further, a scalability analysis indicates the basic concept is applicable to lower and higher power units, with upward scaling for increased power being more readily accomplished.

75 FR 23775 - Agency Information Collection Activities; Proposed Collection; Comment Request; Experimental...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-04

... for research entitled ``Experimental Study of Patient Information Prototypes.'' This study is designed..., the working group refined several prototypes and designed a study to investigate the usefulness of... Design and Protocol The study is experimental and will have two independent variables in a 3 x 2 design...

EXPERIMENTAL DESIGN AND INSTRUMENTATION FOR A FIELD EXPERIMENT

EPA Science Inventory

This report concerns the design of a field experiment for a military setting in which the effects of carbon monoxide on neurobehavioral variables are to be studied. ield experiment is distinguished from a survey by the fact that independent variables are manipulated, just as in t...

Design Fixation in the Wild: Design Environments and Their Influence on Fixation

ERIC Educational Resources Information Center

Youmans, Robert J.

2011-01-01

Many studies of design fixation ask designers to work in controlled laboratory or classroom environments, but innovative design work frequently occurs in dynamic, social environments. The two studies reviewed in this paper investigated how three independent variables likely to be present in many design environments affect design fixation. The…

Sensitivity study of the monogroove with screen heat pipe design

NASA Technical Reports Server (NTRS)

Evans, Austin L.; Joyce, Martin

1988-01-01

The present sensitivity study of design variable effects on the performance of a monogroove-with-screen heat pipe obtains performance curves for maximum heat-transfer rates vs. operating temperatures by means of a computer code; performance projections for both 1-g and zero-g conditions are obtainable. The variables in question were liquid and vapor channel design, wall groove design, and the number of feed lines in the evaporator and condenser. The effect on performance of three different working fluids, namely ammonia, methanol, and water, were also determined. Greatest sensitivity was to changes in liquid and vapor channel diameters.

Learning a novel phonological contrast depends on interactions between individual differences and training paradigm design

PubMed Central

Perrachione, Tyler K.; Lee, Jiyeon; Ha, Louisa Y. Y.; Wong, Patrick C. M.

2011-01-01

Studies evaluating phonological contrast learning typically investigate either the predictiveness of specific pretraining aptitude measures or the efficacy of different instructional paradigms. However, little research considers how these factors interact—whether different students learn better from different types of instruction—and what the psychological basis for any interaction might be. The present study demonstrates that successfully learning a foreign-language phonological contrast for pitch depends on an interaction between individual differences in perceptual abilities and the design of the training paradigm. Training from stimuli with high acoustic-phonetic variability is generally thought to improve learning; however, we found high-variability training enhanced learning only for individuals with strong perceptual abilities. Learners with weaker perceptual abilities were actually impaired by high-variability training relative to a low-variability condition. A second experiment assessing variations on the high-variability training design determined that the property of this learning environment most detrimental to perceptually weak learners is the amount of trial-by-trial variability. Learners’ perceptual limitations can thus override the benefits of high-variability training where trial-by-trial variability in other irrelevant acoustic-phonetic features obfuscates access to the target feature. These results demonstrate the importance of considering individual differences in pretraining aptitudes when evaluating the efficacy of any speech training paradigm. PMID:21786912

Relationships Between Design Characteristics of Avionics Subsystems and Training Cost, Training Difficulty, and Job Performance. Final Report, Covering Activity from 1 July 1971 Through 1 September 1972.

ERIC Educational Resources Information Center

Lintz, Larry M.; And Others

A study investigated the relationship between avionics subsystem design characteristics and training time, training cost, and job performance. A list of design variables believed to affect training and job performance was established and supplemented with personnel variables, including aptitude test scores and the amount of training and…

A regularized variable selection procedure in additive hazards model with stratified case-cohort design.

PubMed

Ni, Ai; Cai, Jianwen

2018-07-01

Case-cohort designs are commonly used in large epidemiological studies to reduce the cost associated with covariate measurement. In many such studies the number of covariates is very large. An efficient variable selection method is needed for case-cohort studies where the covariates are only observed in a subset of the sample. Current literature on this topic has been focused on the proportional hazards model. However, in many studies the additive hazards model is preferred over the proportional hazards model either because the proportional hazards assumption is violated or the additive hazards model provides more relevent information to the research question. Motivated by one such study, the Atherosclerosis Risk in Communities (ARIC) study, we investigate the properties of a regularized variable selection procedure in stratified case-cohort design under an additive hazards model with a diverging number of parameters. We establish the consistency and asymptotic normality of the penalized estimator and prove its oracle property. Simulation studies are conducted to assess the finite sample performance of the proposed method with a modified cross-validation tuning parameter selection methods. We apply the variable selection procedure to the ARIC study to demonstrate its practical use.

A Study of Locale-Wise Differences in Certain Cognitive and Non-Cognitive Variables

ERIC Educational Resources Information Center

Puar, Surjit Singh

2012-01-01

The present study has been designed to investigate the locale-wise differences among high school students on the basis of certain cognitive variables like general mental ability and academic achievement and non-cognitive variables such as anxiety, emotional maturity and social maturity. The study was conducted over a sample of 400 (200 boys and…

Sensitivity analysis for axis rotation diagrid structural systems according to brace angle changes

NASA Astrophysics Data System (ADS)

Yang, Jae-Kwang; Li, Long-Yang; Park, Sung-Soo

2017-10-01

General regular shaped diagrid structures can express diverse shapes because braces are installed along the exterior faces of the structures and the structures have no columns. However, since irregular shaped structures have diverse variables, studies to assess behaviors resulting from various variables are continuously required to supplement the imperfections related to such variables. In the present study, materials elastic modulus and yield strength were selected as variables for strength that would be applied to diagrid structural systems in the form of Twisters among the irregular shaped buildings classified by Vollers and that affect the structural design of these structural systems. The purpose of this study is to conduct sensitivity analysis for axial rotation diagrid structural systems according to changes in brace angles in order to identify the design variables that have relatively larger effects and the tendencies of the sensitivity of the structures according to changes in brace angles and axial rotation angles.

Study/experimental/research design: much more than statistics.

PubMed

Knight, Kenneth L

2010-01-01

The purpose of study, experimental, or research design in scientific manuscripts has changed significantly over the years. It has evolved from an explanation of the design of the experiment (ie, data gathering or acquisition) to an explanation of the statistical analysis. This practice makes "Methods" sections hard to read and understand. To clarify the difference between study design and statistical analysis, to show the advantages of a properly written study design on article comprehension, and to encourage authors to correctly describe study designs. The role of study design is explored from the introduction of the concept by Fisher through modern-day scientists and the AMA Manual of Style. At one time, when experiments were simpler, the study design and statistical design were identical or very similar. With the complex research that is common today, which often includes manipulating variables to create new variables and the multiple (and different) analyses of a single data set, data collection is very different than statistical design. Thus, both a study design and a statistical design are necessary. Scientific manuscripts will be much easier to read and comprehend. A proper experimental design serves as a road map to the study methods, helping readers to understand more clearly how the data were obtained and, therefore, assisting them in properly analyzing the results.

Integrating Mediators and Moderators in Research Design

ERIC Educational Resources Information Center

MacKinnon, David P.

2011-01-01

The purpose of this article is to describe mediating variables and moderating variables and provide reasons for integrating them in outcome studies. Separate sections describe examples of moderating and mediating variables and the simplest statistical model for investigating each variable. The strengths and limitations of incorporating mediating…

Robustness-Based Design Optimization Under Data Uncertainty

NASA Technical Reports Server (NTRS)

Zaman, Kais; McDonald, Mark; Mahadevan, Sankaran; Green, Lawrence

2010-01-01

This paper proposes formulations and algorithms for design optimization under both aleatory (i.e., natural or physical variability) and epistemic uncertainty (i.e., imprecise probabilistic information), from the perspective of system robustness. The proposed formulations deal with epistemic uncertainty arising from both sparse and interval data without any assumption about the probability distributions of the random variables. A decoupled approach is proposed in this paper to un-nest the robustness-based design from the analysis of non-design epistemic variables to achieve computational efficiency. The proposed methods are illustrated for the upper stage design problem of a two-stage-to-orbit (TSTO) vehicle, where the information on the random design inputs are only available as sparse point and/or interval data. As collecting more data reduces uncertainty but increases cost, the effect of sample size on the optimality and robustness of the solution is also studied. A method is developed to determine the optimal sample size for sparse point data that leads to the solutions of the design problem that are least sensitive to variations in the input random variables.

Fractional Factorial Experiment Designs to Minimize Configuration Changes in Wind Tunnel Testing

NASA Technical Reports Server (NTRS)

DeLoach, Richard; Cler, Daniel L.; Graham, Albert B.

2002-01-01

This paper serves as a tutorial to introduce the wind tunnel research community to configuration experiment designs that can satisfy resource constraints in a configuration study involving several variables, without arbitrarily eliminating any of them from the experiment initially. The special case of a configuration study featuring variables at two levels is examined in detail. This is the type of study in which each configuration variable has two natural states - 'on or off', 'deployed or not deployed', 'low or high', and so forth. The basic principles are illustrated by results obtained in configuration studies conducted in the Langley National Transonic Facility and in the ViGYAN Low Speed Tunnel in Hampton, Virginia. The crucial role of interactions among configuration variables is highlighted with an illustration of difficulties that can be encountered when they are not properly taken into account.

Reverse design and characteristic study of multi-range HMCVT

NASA Astrophysics Data System (ADS)

Zhu, Zhen; Chen, Long; Zeng, Falin

2017-09-01

The reduction of fuel consumption and increase of transmission efficiency is one of the key problems of the agricultural machinery. Many promising technologies such as hydromechanical continuously variable transmissions (HMCVT) are the focus of research and investments, but there is little technical documentation that describes the design principle and presents the design parameters. This paper presents the design idea and characteristic study of HMCVT, in order to find out the suitable scheme for the big horsepower tractors. Analyzed the kinematics and dynamics of a large horsepower tractor, according to the characteristic parameters, a hydro-mechanical continuously variable transmission has been designed. Compared with the experimental curves and theoretical curves of the stepless speed regulation of transmission, the experimental result illustrates the rationality of the design scheme.

Design, Characterization, and Optimization of Controlled Drug Delivery System Containing Antibiotic Drug/s

PubMed Central

Shelate, Pragna; Dave, Divyang

2016-01-01

The objective of this work was design, characterization, and optimization of controlled drug delivery system containing antibiotic drug/s. Osmotic drug delivery system was chosen as controlled drug delivery system. The porous osmotic pump tablets were designed using Plackett-Burman and Box-Behnken factorial design to find out the best formulation. For screening of three categories of polymers, six independent variables were chosen for Plackett-Burman design. Osmotic agent sodium chloride and microcrystalline cellulose, pore forming agent sodium lauryl sulphate and sucrose, and coating agent ethyl cellulose and cellulose acetate were chosen as independent variables. Optimization of osmotic tablets was done by Box-Behnken design by selecting three independent variables. Osmotic agent sodium chloride, pore forming agent sodium lauryl sulphate, and coating agent cellulose acetate were chosen as independent variables. The result of Plackett-Burman and Box-Behnken design and ANOVA studies revealed that osmotic agent and pore former had significant effect on the drug release up to 12 hr. The observed independent variables were found to be very close to predicted values of most satisfactory formulation which demonstrates the feasibility of the optimization procedure in successful development of porous osmotic pump tablets containing antibiotic drug/s by using sodium chloride, sodium lauryl sulphate, and cellulose acetate as key excipients. PMID:27610247

Evidence-based mapping of design heterogeneity prior to meta-analysis: a systematic review and evidence synthesis.

PubMed

Althuis, Michelle D; Weed, Douglas L; Frankenfeld, Cara L

2014-07-23

Assessment of design heterogeneity conducted prior to meta-analysis is infrequently reported; it is often presented post hoc to explain statistical heterogeneity. However, design heterogeneity determines the mix of included studies and how they are analyzed in a meta-analysis, which in turn can importantly influence the results. The goal of this work is to introduce ways to improve the assessment and reporting of design heterogeneity prior to statistical summarization of epidemiologic studies. In this paper, we use an assessment of sugar-sweetened beverages (SSB) and type 2 diabetes (T2D) as an example to show how a technique called 'evidence mapping' can be used to organize studies and evaluate design heterogeneity prior to meta-analysis.. Employing a systematic and reproducible approach, we evaluated the following elements across 11 selected cohort studies: variation in definitions of SSB, T2D, and co-variables, design features and population characteristics associated with specific definitions of SSB, and diversity in modeling strategies. Evidence mapping strategies effectively organized complex data and clearly depicted design heterogeneity. For example, across 11 studies of SSB and T2D, 7 measured diet only once (with 7 to 16 years of disease follow-up), 5 included primarily low SSB consumers, and 3 defined the study variable (SSB) as consumption of either sugar or artificially-sweetened beverages. This exercise also identified diversity in analysis strategies, such as adjustment for 11 to 17 co-variables and a large degree of fluctuation in SSB-T2D risk estimates depending on variables selected for multivariable models (2 to 95% change in the risk estimate from the age-adjusted model). Meta-analysis seeks to understand heterogeneity in addition to computing a summary risk estimate. This strategy effectively documents design heterogeneity, thus improving the practice of meta-analysis by aiding in: 1) protocol and analysis planning, 2) transparent reporting of differences in study designs, and 3) interpretation of pooled estimates. We recommend expanding the practice of meta-analysis reporting to include a table that summarizes design heterogeneity. This would provide readers with more evidence to interpret the summary risk estimates.

Evidence-based mapping of design heterogeneity prior to meta-analysis: a systematic review and evidence synthesis

PubMed Central

2014-01-01

Background Assessment of design heterogeneity conducted prior to meta-analysis is infrequently reported; it is often presented post hoc to explain statistical heterogeneity. However, design heterogeneity determines the mix of included studies and how they are analyzed in a meta-analysis, which in turn can importantly influence the results. The goal of this work is to introduce ways to improve the assessment and reporting of design heterogeneity prior to statistical summarization of epidemiologic studies. Methods In this paper, we use an assessment of sugar-sweetened beverages (SSB) and type 2 diabetes (T2D) as an example to show how a technique called ‘evidence mapping’ can be used to organize studies and evaluate design heterogeneity prior to meta-analysis.. Employing a systematic and reproducible approach, we evaluated the following elements across 11 selected cohort studies: variation in definitions of SSB, T2D, and co-variables, design features and population characteristics associated with specific definitions of SSB, and diversity in modeling strategies. Results Evidence mapping strategies effectively organized complex data and clearly depicted design heterogeneity. For example, across 11 studies of SSB and T2D, 7 measured diet only once (with 7 to 16 years of disease follow-up), 5 included primarily low SSB consumers, and 3 defined the study variable (SSB) as consumption of either sugar or artificially-sweetened beverages. This exercise also identified diversity in analysis strategies, such as adjustment for 11 to 17 co-variables and a large degree of fluctuation in SSB-T2D risk estimates depending on variables selected for multivariable models (2 to 95% change in the risk estimate from the age-adjusted model). Conclusions Meta-analysis seeks to understand heterogeneity in addition to computing a summary risk estimate. This strategy effectively documents design heterogeneity, thus improving the practice of meta-analysis by aiding in: 1) protocol and analysis planning, 2) transparent reporting of differences in study designs, and 3) interpretation of pooled estimates. We recommend expanding the practice of meta-analysis reporting to include a table that summarizes design heterogeneity. This would provide readers with more evidence to interpret the summary risk estimates. PMID:25055879

The Role of Design-of-Experiments in Managing Flow in Compact Air Vehicle Inlets

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.; Miller, Daniel N.; Gridley, Marvin C.; Agrell, Johan

2003-01-01

It is the purpose of this study to demonstrate the viability and economy of Design-of-Experiments methodologies to arrive at microscale secondary flow control array designs that maintain optimal inlet performance over a wide range of the mission variables and to explore how these statistical methods provide a better understanding of the management of flow in compact air vehicle inlets. These statistical design concepts were used to investigate the robustness properties of low unit strength micro-effector arrays. Low unit strength micro-effectors are micro-vanes set at very low angles-of-incidence with very long chord lengths. They were designed to influence the near wall inlet flow over an extended streamwise distance, and their advantage lies in low total pressure loss and high effectiveness in managing engine face distortion. The term robustness is used in this paper in the same sense as it is used in the industrial problem solving community. It refers to minimizing the effects of the hard-to-control factors that influence the development of a product or process. In Robustness Engineering, the effects of the hard-to-control factors are often called noise , and the hard-to-control factors themselves are referred to as the environmental variables or sometimes as the Taguchi noise variables. Hence Robust Optimization refers to minimizing the effects of the environmental or noise variables on the development (design) of a product or process. In the management of flow in compact inlets, the environmental or noise variables can be identified with the mission variables. Therefore this paper formulates a statistical design methodology that minimizes the impact of variations in the mission variables on inlet performance and demonstrates that these statistical design concepts can lead to simpler inlet flow management systems.

Planning, Supervision and Quality of Instructional Leadership of Girls' Day Secondary Schools in Kaduna State, Nigeria

ERIC Educational Resources Information Center

Duruh, Benjamin C.

2018-01-01

This study investigated the Planning, Supervision and Quality of Instructional Leadership of Girls' Day Secondary Schools in Kaduna State. The research design adopted was a survey design. The independent variables were the respondents which include principals, teachers, students, parents and government officials while dependent variable includes…

Career Choices in Engineering: The Influence of Peers and Parents Implication for Counselling

ERIC Educational Resources Information Center

Alika, Henrietta Ijeoma

2012-01-01

This study was designed to investigate the relationship between parental and peer group influence on career choice in engineering profession among adolescents. The research design adopted was correlational because it sought to establish the relationship between the independent variable and the dependent variable. One research question and one…

The Paired Availability Design and Related Instrumental Variable Meta-analyses | Division of Cancer Prevention

Cancer.gov

Stuart G. Baker, 2017 Introduction This software computes meta-analysis and extrapolation estimates for an instrumental variable meta-analysis of randomized trial or before-and-after studies (the latter also known as the paired availability design). The software also checks on the assumptions if sufficient data are available. |

Intraclass Correlation Coefficients in Hierarchical Designs: Evaluation Using Latent Variable Modeling

ERIC Educational Resources Information Center

Raykov, Tenko

2011-01-01

Interval estimation of intraclass correlation coefficients in hierarchical designs is discussed within a latent variable modeling framework. A method accomplishing this aim is outlined, which is applicable in two-level studies where participants (or generally lower-order units) are clustered within higher-order units. The procedure can also be…

The Taguchi methodology as a statistical tool for biotechnological applications: a critical appraisal.

PubMed

Rao, Ravella Sreenivas; Kumar, C Ganesh; Prakasham, R Shetty; Hobbs, Phil J

2008-04-01

Success in experiments and/or technology mainly depends on a properly designed process or product. The traditional method of process optimization involves the study of one variable at a time, which requires a number of combinations of experiments that are time, cost and labor intensive. The Taguchi method of design of experiments is a simple statistical tool involving a system of tabulated designs (arrays) that allows a maximum number of main effects to be estimated in an unbiased (orthogonal) fashion with a minimum number of experimental runs. It has been applied to predict the significant contribution of the design variable(s) and the optimum combination of each variable by conducting experiments on a real-time basis. The modeling that is performed essentially relates signal-to-noise ratio to the control variables in a 'main effect only' approach. This approach enables both multiple response and dynamic problems to be studied by handling noise factors. Taguchi principles and concepts have made extensive contributions to industry by bringing focused awareness to robustness, noise and quality. This methodology has been widely applied in many industrial sectors; however, its application in biological sciences has been limited. In the present review, the application and comparison of the Taguchi methodology has been emphasized with specific case studies in the field of biotechnology, particularly in diverse areas like fermentation, food processing, molecular biology, wastewater treatment and bioremediation.

Preliminary Assessment of Variable Speed Power Turbine Technology on Civil Tiltrotor Size and Performance

NASA Technical Reports Server (NTRS)

Snyder, Christopher A.; Acree, Cecil W., Jr.

2012-01-01

A Large Civil Tiltrotor (LCTR) conceptual design was developed as part of the NASA Heavy Lift Rotorcraft Systems Investigation in order to establish a consistent basis for evaluating the benefits of advanced technology for large tiltrotors. The concept has since evolved into the second-generation LCTR2, designed to carry 90 passengers for 1,000 nm at 300 knots, with vertical takeoff and landing capability. This paper performs a preliminary assessment of variable-speed power turbine technology on LCTR2 sizing, while maintaining the same, advanced technology engine core. Six concepts were studied; an advanced, single-speed engine with a conventional power turbine layout (Advanced Conventional Engine, or ACE) using a multi-speed (shifting) gearbox. There were five variable-speed power turbine (VSPT) engine concepts, comprising a matrix of either three or four turbine stages, and fixed or variable guide vanes; plus a minimum weight, twostage, fixed-geometry VSPT. The ACE is the lightest engine, but requires a multi-speed (shifting) gearbox to maximize its fuel efficiency, whereas the VSPT concepts use a lighter, fixed-ratio gearbox. The NASA Design and Analysis of Rotorcraft (NDARC) design code was used to study the trades between rotor and engine efficiency and weight. Rotor performance was determined by Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD II), and engine performance was estimated with the Numerical Propulsion System Simulation (NPSS). Design trades for the ACE vs. VSPT are presented in terms of vehicle gross and empty weight, propulsion system weight and mission fuel burn for the civil mission. Because of its strong effect on gearbox weight and on both rotor and engine efficiency, rotor speed was chosen as the reference design variable for comparing design trades. Major study assumptions are presented and discussed. Impressive engine power-to-weight and fuel efficiency reduced vehicle sensitivity to propulsion system choice. The 10% weight penalty for multi-speed gearbox was more significant than most engine technology weight penalties to the vehicle design because drive system weight is more than two times engine weight. Based on study assumptions, fixed-geometry VSPT concept options performed better than their variable-geometry counterparts. Optimum design gross weights varied 1% or less and empty weights less than 2% among the concepts studied, while optimum fuel burns varied up to 5%. The outcome for some optimum configurations was so unexpected as to recommend a deeper look at the underlying technology assumptions.

Learning a novel phonological contrast depends on interactions between individual differences and training paradigm design.

PubMed

Perrachione, Tyler K; Lee, Jiyeon; Ha, Louisa Y Y; Wong, Patrick C M

2011-07-01

Studies evaluating phonological contrast learning typically investigate either the predictiveness of specific pretraining aptitude measures or the efficacy of different instructional paradigms. However, little research considers how these factors interact--whether different students learn better from different types of instruction--and what the psychological basis for any interaction might be. The present study demonstrates that successfully learning a foreign-language phonological contrast for pitch depends on an interaction between individual differences in perceptual abilities and the design of the training paradigm. Training from stimuli with high acoustic-phonetic variability is generally thought to improve learning; however, we found high-variability training enhanced learning only for individuals with strong perceptual abilities. Learners with weaker perceptual abilities were actually impaired by high-variability training relative to a low-variability condition. A second experiment assessing variations on the high-variability training design determined that the property of this learning environment most detrimental to perceptually weak learners is the amount of trial-by-trial variability. Learners' perceptual limitations can thus override the benefits of high-variability training where trial-by-trial variability in other irrelevant acoustic-phonetic features obfuscates access to the target feature. These results demonstrate the importance of considering individual differences in pretraining aptitudes when evaluating the efficacy of any speech training paradigm. © 2011 Acoustical Society of America

Multi-Objective Optimization of a Turbofan for an Advanced, Single-Aisle Transport

NASA Technical Reports Server (NTRS)

Berton, Jeffrey J.; Guynn, Mark D.

2012-01-01

Considerable interest surrounds the design of the next generation of single-aisle commercial transports in the Boeing 737 and Airbus A320 class. Aircraft designers will depend on advanced, next-generation turbofan engines to power these airplanes. The focus of this study is to apply single- and multi-objective optimization algorithms to the conceptual design of ultrahigh bypass turbofan engines for this class of aircraft, using NASA s Subsonic Fixed Wing Project metrics as multidisciplinary objectives for optimization. The independent design variables investigated include three continuous variables: sea level static thrust, wing reference area, and aerodynamic design point fan pressure ratio, and four discrete variables: overall pressure ratio, fan drive system architecture (i.e., direct- or gear-driven), bypass nozzle architecture (i.e., fixed- or variable geometry), and the high- and low-pressure compressor work split. Ramp weight, fuel burn, noise, and emissions are the parameters treated as dependent objective functions. These optimized solutions provide insight to the ultrahigh bypass engine design process and provide information to NASA program management to help guide its technology development efforts.

21 CFR 514.117 - Adequate and well-controlled studies.

Code of Federal Regulations, 2011 CFR

2011-04-01

... experimental units. When the effect of such variables is accounted for by an appropriate design, and when... and well-controlled study should provide sufficient details of study design, conduct, and analysis to... the new animal drug used in the study. (4) The study uses a design that permits a valid comparison...

21 CFR 514.117 - Adequate and well-controlled studies.

Code of Federal Regulations, 2012 CFR

2012-04-01

... experimental units. When the effect of such variables is accounted for by an appropriate design, and when... and well-controlled study should provide sufficient details of study design, conduct, and analysis to... the new animal drug used in the study. (4) The study uses a design that permits a valid comparison...

21 CFR 514.117 - Adequate and well-controlled studies.

Code of Federal Regulations, 2014 CFR

2014-04-01

... experimental units. When the effect of such variables is accounted for by an appropriate design, and when... and well-controlled study should provide sufficient details of study design, conduct, and analysis to... the new animal drug used in the study. (4) The study uses a design that permits a valid comparison...

21 CFR 514.117 - Adequate and well-controlled studies.

Code of Federal Regulations, 2013 CFR

2013-04-01

... experimental units. When the effect of such variables is accounted for by an appropriate design, and when... and well-controlled study should provide sufficient details of study design, conduct, and analysis to... the new animal drug used in the study. (4) The study uses a design that permits a valid comparison...

21 CFR 514.117 - Adequate and well-controlled studies.

Code of Federal Regulations, 2010 CFR

2010-04-01

... experimental units. When the effect of such variables is accounted for by an appropriate design, and when... and well-controlled study should provide sufficient details of study design, conduct, and analysis to... the new animal drug used in the study. (4) The study uses a design that permits a valid comparison...

Application of quality by design concept to develop a dual gradient elution stability-indicating method for cloxacillin forced degradation studies using combined mixture-process variable models.

PubMed

Zhang, Xia; Hu, Changqin

2017-09-08

Penicillins are typical of complex ionic samples which likely contain large number of degradation-related impurities (DRIs) with different polarities and charge properties. It is often a challenge to develop selective and robust high performance liquid chromatography (HPLC) methods for the efficient separation of all DRIs. In this study, an analytical quality by design (AQbD) approach was proposed for stability-indicating method development of cloxacillin. The structures, retention and UV characteristics rules of penicillins and their impurities were summarized and served as useful prior knowledge. Through quality risk assessment and screen design, 3 critical process parameters (CPPs) were defined, including 2 mixture variables (MVs) and 1 process variable (PV). A combined mixture-process variable (MPV) design was conducted to evaluate the 3 CPPs simultaneously and a response surface methodology (RSM) was used to achieve the optimal experiment parameters. A dual gradient elution was performed to change buffer pH, mobile-phase type and strength simultaneously. The design spaces (DSs) was evaluated using Monte Carlo simulation to give their possibility of meeting the specifications of CQAs. A Plackett-Burman design was performed to test the robustness around the working points and to decide the normal operating ranges (NORs). Finally, validation was performed following International Conference on Harmonisation (ICH) guidelines. To our knowledge, this is the first study of using MPV design and dual gradient elution to develop HPLC methods and improve separations for complex ionic samples. Copyright © 2017 Elsevier B.V. All rights reserved.

A Discourse on Human Systems Integration

DTIC Science & Technology

2010-09-01

criterion for one of the study tasks. 2. Research Design This was a mixed methods study. The first-phase quantitative portion of the study...used a quasi-experimental, posttest-only with nonequivalent groups design . The independent variables were defined as follows: • The categorical... Research Design ...............................................................................287 3. Instruments

Advanced supersonic propulsion system technology study, phase 2

NASA Technical Reports Server (NTRS)

Allan, R. D.

1975-01-01

Variable cycle engines were identified, based on the mixed-flow low-bypass-ratio augmented turbofan cycle, which has shown excellent range capability in the AST airplane. The best mixed-flow augmented turbofan engine was selected based on range in the AST Baseline Airplane. Selected variable cycle engine features were added to this best conventional baseline engine, and the Dual-Cycle VCE and Double-Bypass VCE were defined. The conventional mixed-flow turbofan and the Double-Bypass VCE were on the subjects of engine preliminary design studies to determine mechanical feasibility, confirm weight and dimensional estimates, and identify the necessary technology considered not yet available. Critical engine components were studied and incorporated into the variable cycle engine design.

A variable structure approach to robust control of VTOL aircraft

NASA Technical Reports Server (NTRS)

Calise, A. J.; Kramer, F.

1982-01-01

This paper examines the application of variable structure control theory to the design of a flight control system for the AV-8A Harrier in a hover mode. The objective in variable structure design is to confine the motion to a subspace of the total state space. The motion in this subspace is insensitive to system parameter variations and external disturbances that lie in the range space of the control. A switching type of control law results from the design procedure. The control system was designed to track a vector velocity command defined in the body frame. For comparison purposes, a proportional controller was designed using optimal linear regulator theory. Both control designs were first evaluated for transient response performance using a linearized model, then a nonlinear simulation study of a hovering approach to landing was conducted. Wind turbulence was modeled using a 1052 destroyer class air wake model.

Active Power and Flux Control of a Self-Excited Induction Generator for a Variable-Speed Wind Turbine Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Na, Woonki; Muljadi, Eduard; Leighty, Bill

A Self-Excited Induction Generation (SEIG) for a variable speed wind turbine generation(VS-WG) is normally considered to be a good candidate for implementation in stand-alone applications such as battery charging, hydrogenation, water pumping, water purification, water desalination, and etc. In this study, we have examined a study on active power and flux control strategies for a SEIG for a variable speed wind turbine generation. The control analysis for the proposed system is carried out by using PSCAD software. In the process, we can optimize the control design of the system, thereby enhancing and expediting the control design procedure for this application.more » With this study, this control design for a SEIG for VS-WG can become the industry standard for analysis and development in terms of SEIG.« less

Study/Experimental/Research Design: Much More Than Statistics

PubMed Central

Knight, Kenneth L.

2010-01-01

Abstract Context: The purpose of study, experimental, or research design in scientific manuscripts has changed significantly over the years. It has evolved from an explanation of the design of the experiment (ie, data gathering or acquisition) to an explanation of the statistical analysis. This practice makes “Methods” sections hard to read and understand. Objective: To clarify the difference between study design and statistical analysis, to show the advantages of a properly written study design on article comprehension, and to encourage authors to correctly describe study designs. Description: The role of study design is explored from the introduction of the concept by Fisher through modern-day scientists and the AMA Manual of Style. At one time, when experiments were simpler, the study design and statistical design were identical or very similar. With the complex research that is common today, which often includes manipulating variables to create new variables and the multiple (and different) analyses of a single data set, data collection is very different than statistical design. Thus, both a study design and a statistical design are necessary. Advantages: Scientific manuscripts will be much easier to read and comprehend. A proper experimental design serves as a road map to the study methods, helping readers to understand more clearly how the data were obtained and, therefore, assisting them in properly analyzing the results. PMID:20064054

Construction of nested maximin designs based on successive local enumeration and modified novel global harmony search algorithm

NASA Astrophysics Data System (ADS)

Yi, Jin; Li, Xinyu; Xiao, Mi; Xu, Junnan; Zhang, Lin

2017-01-01

Engineering design often involves different types of simulation, which results in expensive computational costs. Variable fidelity approximation-based design optimization approaches can realize effective simulation and efficiency optimization of the design space using approximation models with different levels of fidelity and have been widely used in different fields. As the foundations of variable fidelity approximation models, the selection of sample points of variable-fidelity approximation, called nested designs, is essential. In this article a novel nested maximin Latin hypercube design is constructed based on successive local enumeration and a modified novel global harmony search algorithm. In the proposed nested designs, successive local enumeration is employed to select sample points for a low-fidelity model, whereas the modified novel global harmony search algorithm is employed to select sample points for a high-fidelity model. A comparative study with multiple criteria and an engineering application are employed to verify the efficiency of the proposed nested designs approach.

Secondary Students' Considerations of Variability in Measurement Activities Based on Authentic Practices

ERIC Educational Resources Information Center

Dierdorp, Adri; Bakker, Arthur; Ben-Zvi, Dani; Makar, Katie

2017-01-01

Measurement activities were designed in this study on the basis of authentic professional practices in which linear regression is used, to study considerations of variability by students in Grade 12 (aged 17-18). The question addressed in this article is: In what ways do secondary students consider variability within these measurement activities?…

Development of Micro Air Vehicle Technology With In-Flight Adaptive-Wing Structure

NASA Technical Reports Server (NTRS)

Waszak, Martin R. (Technical Monitor); Shkarayev, Sergey; Null, William; Wagner, Matthew

2004-01-01

This is a final report on the research studies, "Development of Micro Air Vehicle Technology with In-Flight Adaptrive-Wing Structure". This project involved the development of variable-camber technology to achieve efficient design of micro air vehicles. Specifically, it focused on the following topics: 1) Low Reynolds number wind tunnel testing of cambered-plate wings. 2) Theoretical performance analysis of micro air vehicles. 3) Design of a variable-camber MAV actuated by micro servos. 4) Test flights of a variable-camber MAV.

Baroclinic instability with variable static stability - A design study for a spherical atmospheric model experiment. [for Spacelab flight

NASA Technical Reports Server (NTRS)

Giere, A. C.; Fowlis, W. W.

1980-01-01

The effect of a radially-variable, dielectric body force, analogous to gravity on baroclinic instability for the design of a spherical, synoptic-scale, atmospheric model experiment in a Spacelab flight is investigated. Exact solutions are examined for quasi-geostrophic baroclinic instability in which the rotational Froude number is a linear function of the height. Flow in a rotating rectilinear channel with a vertically variable body force without horizontal shear of the basic state is also discussed.

Effect of study design and setting on tuberculosis clustering estimates using Mycobacterial Interspersed Repetitive Units-Variable Number Tandem Repeats (MIRU-VNTR): a systematic review.

PubMed

Mears, Jessica; Abubakar, Ibrahim; Cohen, Theodore; McHugh, Timothy D; Sonnenberg, Pam

2015-01-21

To systematically review the evidence for the impact of study design and setting on the interpretation of tuberculosis (TB) transmission using clustering derived from Mycobacterial Interspersed Repetitive Units-Variable Number Tandem Repeats (MIRU-VNTR) strain typing. MEDLINE, EMBASE, CINHAL, Web of Science and Scopus were searched for articles published before 21st October 2014. Studies in humans that reported the proportion of clustering of TB isolates by MIRU-VNTR were included in the analysis. Univariable meta-regression analyses were conducted to assess the influence of study design and setting on the proportion of clustering. The search identified 27 eligible articles reporting clustering between 0% and 63%. The number of MIRU-VNTR loci typed, requiring consent to type patient isolates (as a proxy for sampling fraction), the TB incidence and the maximum cluster size explained 14%, 14%, 27% and 48% of between-study variation, respectively, and had a significant association with the proportion of clustering. Although MIRU-VNTR typing is being adopted worldwide there is a paucity of data on how study design and setting may influence estimates of clustering. We have highlighted study design variables for consideration in the design and interpretation of future studies. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Analysis of Students' Online Information Searching Strategies, Exposure to Internet Information Pollution and Cognitive Absorption Levels Based on Various Variables

ERIC Educational Resources Information Center

Kurt, Adile Askim; Emiroglu, Bülent Gürsel

2018-01-01

The objective of the present study was to examine students' online information searching strategies, their cognitive absorption levels and the information pollution levels on the Internet based on different variables and to determine the correlation between these variables. The study was designed with the survey model, the study group included 198…

Development of uniform and predictable battery materials for nickel-cadmium aerospace cells

NASA Technical Reports Server (NTRS)

1971-01-01

Battery materials and manufacturing methods were analyzed with the aim of developing uniform and predictable battery plates for nickel cadmium aerospace cells. A study is presented for the high temperature electrochemical impregnation process for the preparation of nickel cadmium battery plates. This comparative study is set up as a factorially designed experiment to examine both manufacturing and operational variables and any interaction that might exist between them. The manufacturing variables in the factorial design include plaque preparative method, plaque porosity and thickness, impregnation method, and loading, The operational variables are type of duty cycle, charge and discharge rate, extent of overcharge, and depth of discharge.

EFFECT OF INTENSE FUNCTIONAL TASK TRAINING UPON TEMPORAL STRUCTURE OF VARIABILITY OF UPPER EXTREMITY POST STROKE

PubMed Central

Sethi, Amit; Davis, Sandra; McGuirk, Theresa; Patterson, Tara S.; Richards, Lorie G.

2012-01-01

Study Design Quasi-experimental design Introduction Although the effectiveness of constraint induced movement therapy (CIMT) in upper extremity (UE) rehabilitation post stroke is well known, the efficacy of CIMT to enhance the temporal structure of variability in upper extremity movement is not known. Purpose The purpose of this study was to investigate whether CIMT could enhance temporal structure of variability in upper extremity movement in individuals with chronic stroke. Methods Six participants with chronic stroke underwent CIMT for 4 hours/day for 2 weeks. Participants performed three trials of functional reach-to-grasp before and after CIMT. Temporal structure of variability was determined by calculating approximate entropy (ApEn) in shoulder, elbow and wrist flexion/extension joint angles. Results ApEn increased post CIMT, however, statistical significance was not achieved (p > 0.0167). Conclusion Future studies with larger sample size are warranted to investigate the effect of CIMT upon temporal structure of variability in UE movement. PMID:23084461

Media milling process optimization for manufacture of drug nanoparticles using design of experiments (DOE).

PubMed

Nekkanti, Vijaykumar; Marwah, Ashwani; Pillai, Raviraj

2015-01-01

Design of experiments (DOE), a component of Quality by Design (QbD), is systematic and simultaneous evaluation of process variables to develop a product with predetermined quality attributes. This article presents a case study to understand the effects of process variables in a bead milling process used for manufacture of drug nanoparticles. Experiments were designed and results were computed according to a 3-factor, 3-level face-centered central composite design (CCD). The factors investigated were motor speed, pump speed and bead volume. Responses analyzed for evaluating these effects and interactions were milling time, particle size and process yield. Process validation batches were executed using the optimum process conditions obtained from software Design-Expert® to evaluate both the repeatability and reproducibility of bead milling technique. Milling time was optimized to <5 h to obtain the desired particle size (d90 < 400 nm). The desirability function used to optimize the response variables and observed responses were in agreement with experimental values. These results demonstrated the reliability of selected model for manufacture of drug nanoparticles with predictable quality attributes. The optimization of bead milling process variables by applying DOE resulted in considerable decrease in milling time to achieve the desired particle size. The study indicates the applicability of DOE approach to optimize critical process parameters in the manufacture of drug nanoparticles.

Near Zero Energy House (NZEH) Design Optimization to Improve Life Cycle Cost Performance Using Genetic Algorithm

NASA Astrophysics Data System (ADS)

Latief, Y.; Berawi, M. A.; Koesalamwardi, A. B.; Supriadi, L. S. R.

2018-03-01

Near Zero Energy House (NZEH) is a housing building that provides energy efficiency by using renewable energy technologies and passive house design. Currently, the costs for NZEH are quite expensive due to the high costs of the equipment and materials for solar panel, insulation, fenestration and other renewable energy technology. Therefore, a study to obtain the optimum design of a NZEH is necessary. The aim of the optimum design is achieving an economical life cycle cost performance of the NZEH. One of the optimization methods that could be utilized is Genetic Algorithm. It provides the method to obtain the optimum design based on the combinations of NZEH variable designs. This paper discusses the study to identify the optimum design of a NZEH that provides an optimum life cycle cost performance using Genetic Algorithm. In this study, an experiment through extensive design simulations of a one-level house model was conducted. As a result, the study provide the optimum design from combinations of NZEH variable designs, which are building orientation, window to wall ratio, and glazing types that would maximize the energy generated by photovoltaic panel. Hence, the design would support an optimum life cycle cost performance of the house.

Gaming in the Classroom: An Innovative Way to Teach Factorial Designs

ERIC Educational Resources Information Center

Stansbury, Jessica A.; Munro, Geoffrey D.

2013-01-01

This study tested the effectiveness of video game use for instruction of factorial designs in a research methods course. Students designed and conducted a mini study, playing "Dance, Dance, Revolution", using video game scores as the dependent variable. A mixed-design analysis of variance revealed a significantly greater increase from pretest to…

A Parallel Trade Study Architecture for Design Optimization of Complex Systems

NASA Technical Reports Server (NTRS)

Kim, Hongman; Mullins, James; Ragon, Scott; Soremekun, Grant; Sobieszczanski-Sobieski, Jaroslaw

2005-01-01

Design of a successful product requires evaluating many design alternatives in a limited design cycle time. This can be achieved through leveraging design space exploration tools and available computing resources on the network. This paper presents a parallel trade study architecture to integrate trade study clients and computing resources on a network using Web services. The parallel trade study solution is demonstrated to accelerate design of experiments, genetic algorithm optimization, and a cost as an independent variable (CAIV) study for a space system application.

Optimizing Experimental Designs: Finding Hidden Treasure.

USDA-ARS?s Scientific Manuscript database

Classical experimental design theory, the predominant treatment in most textbooks, promotes the use of blocking designs for control of spatial variability in field studies and other situations in which there is significant variation among heterogeneity among experimental units. Many blocking design...

Defining process design space for a hydrophobic interaction chromatography (HIC) purification step: application of quality by design (QbD) principles.

PubMed

Jiang, Canping; Flansburg, Lisa; Ghose, Sanchayita; Jorjorian, Paul; Shukla, Abhinav A

2010-12-15

The concept of design space has been taking root under the quality by design paradigm as a foundation of in-process control strategies for biopharmaceutical manufacturing processes. This paper outlines the development of a design space for a hydrophobic interaction chromatography (HIC) process step. The design space included the impact of raw material lot-to-lot variability and variations in the feed stream from cell culture. A failure modes and effects analysis was employed as the basis for the process characterization exercise. During mapping of the process design space, the multi-dimensional combination of operational variables were studied to quantify the impact on process performance in terms of yield and product quality. Variability in resin hydrophobicity was found to have a significant influence on step yield and high-molecular weight aggregate clearance through the HIC step. A robust operating window was identified for this process step that enabled a higher step yield while ensuring acceptable product quality. © 2010 Wiley Periodicals, Inc.

Structural reanalysis via a mixed method. [using Taylor series for accuracy improvement

NASA Technical Reports Server (NTRS)

Noor, A. K.; Lowder, H. E.

1975-01-01

A study is made of the approximate structural reanalysis technique based on the use of Taylor series expansion of response variables in terms of design variables in conjunction with the mixed method. In addition, comparisons are made with two reanalysis techniques based on the displacement method. These techniques are the Taylor series expansion and the modified reduced basis. It is shown that the use of the reciprocals of the sizing variables as design variables (which is the natural choice in the mixed method) can result in a substantial improvement in the accuracy of the reanalysis technique. Numerical results are presented for a space truss structure.

The Impact of Residence Design on Freshman Outcomes: Dormitories versus Suite-Style Residences

ERIC Educational Resources Information Center

Rodger, Susan C.; Johnson, Andrew W.

2005-01-01

This study was designed to measure affective, behavioral, and cognitive variables in a sample of 3159 first-year students, and to compare these variables by the type of residence building in which the student lived. Students living in suite-style buildings reported a greater sense of belonging, and higher activity levels than students living in…

Application of Plackett-Burman experimental design in the development of muffin using adlay flour

NASA Astrophysics Data System (ADS)

Valmorida, J. S.; Castillo-Israel, K. A. T.

2018-01-01

The application of Plackett-Burman experimental design was made to identify significant formulation and process variables in the development of muffin using adlay flour. Out of the seven screened variables, levels of sugar, levels of butter and baking temperature had the most significant influence on the product model in terms of physicochemical and sensory acceptability. Results of the experiment further demonstrate the effectiveness of Plackett-Burman design in choosing the best adlay variety for muffin production. Hence, the statistical method used in the study permits an efficient selection of important variables needed in the development of muffin from adlay which can be optimized using response surface methodology.

Definition study for variable cycle engine testbed engine and associated test program

NASA Technical Reports Server (NTRS)

Vdoviak, J. W.

1978-01-01

The product/study double bypass variable cycle engine (VCE) was updated to incorporate recent improvements. The effect of these improvements on mission range and noise levels was determined. This engine design was then compared with current existing high-technology core engines in order to define a subscale testbed configuration that simulated many of the critical technology features of the product/study VCE. Detailed preliminary program plans were then developed for the design, fabrication, and static test of the selected testbed engine configuration. These plans included estimated costs and schedules for the detail design, fabrication and test of the testbed engine and the definition of a test program, test plan, schedule, instrumentation, and test stand requirements.

The Quebec Rural Emergency Department Project: A Cross-Sectional Study of a Potential Two-Pronged Strategy in the Knowledge Transfer Process

PubMed Central

Poitras, Julien; Chauny, Jean-Marc; Lévesque, Jean-Frédéric; Ouimet, Mathieu; Dupuis, Gilles; Tanguay, Alain; Simard-Racine, Geneviève

2015-01-01

Introduction Health services research generates useful knowledge. Promotion of implementation of this knowledge in medical practice is essential. Prior to initiation of a major study on rural emergency departments (EDs), we deployed two knowledge transfer strategies designed to generate interest and engagement from potential knowledge users. The objective of this paper was to review: 1) a combined project launch and media press release strategy, and 2) a pre-study survey designed to survey potential knowledge users’ opinions on the proposed study variables. Materials and Methods We evaluated the impact of the project launch (presentation at two conferences hosted by key stakeholders) and media press release via a survey of participants/stakeholders and by calculating the number of media interview requests and reports generated. We used a pre-study survey to collect potential key stakeholder’ opinions on the study variables. Results Twenty-one of Quebec’s 26 rural EDs participated in the pre-study survey (81% participation rate). The press release about the study generated 51 press articles and 20 media request for interviews, and contributed to public awareness of a major rural research initiative. In the pre-study survey, thirteen participants (46%) mentioned prior knowledge of the research project. Results from the pre-study survey revealed that all of the potential study variables were considered to be relevant for inclusion in the research project. Respondents also proposed additional variables of interest, including factors promoting retention of human resources. Conclusions The present study demonstrated the potential utility of a two-pronged knowledge transfer strategy, including a combined formal launch and press release, and a pre-study survey designed to ensure that the included variables were of interest to participants and stakeholders. PMID:25849328

Quality by design case study: an integrated multivariate approach to drug product and process development.

PubMed

Huang, Jun; Kaul, Goldi; Cai, Chunsheng; Chatlapalli, Ramarao; Hernandez-Abad, Pedro; Ghosh, Krishnendu; Nagi, Arwinder

2009-12-01

To facilitate an in-depth process understanding, and offer opportunities for developing control strategies to ensure product quality, a combination of experimental design, optimization and multivariate techniques was integrated into the process development of a drug product. A process DOE was used to evaluate effects of the design factors on manufacturability and final product CQAs, and establish design space to ensure desired CQAs. Two types of analyses were performed to extract maximal information, DOE effect & response surface analysis and multivariate analysis (PCA and PLS). The DOE effect analysis was used to evaluate the interactions and effects of three design factors (water amount, wet massing time and lubrication time), on response variables (blend flow, compressibility and tablet dissolution). The design space was established by the combined use of DOE, optimization and multivariate analysis to ensure desired CQAs. Multivariate analysis of all variables from the DOE batches was conducted to study relationships between the variables and to evaluate the impact of material attributes/process parameters on manufacturability and final product CQAs. The integrated multivariate approach exemplifies application of QbD principles and tools to drug product and process development.

HIGH SHEAR GRANULATION PROCESS: ASSESSING IMPACT OF FORMULATION VARIABLES ON GRANULES AND TABLETS CHARACTERISTICS OF HIGH DRUG LOADING FORMULATION USING DESIGN OF EXPERIMENT METHODOLOGY.

PubMed

Fayed, Mohamed H; Abdel-Rahman, Sayed I; Alanazi, Fars K; Ahmed, Mahrous O; Tawfeek, Hesham M; Ali, Bahaa E

2017-03-01

High shear wet granulation is a significant component procedure in the pharmaceutical industry. The objective of the study was to investigate the influence of two independent formulation variables; polyvinypyrrolidone (PVP) as a binder (X,) and croscarmellose sodium (CCS) as a disintegrant (X2) on the crit- ical quality attributes of acetaminophen granules and their corresponding tablets using design of experiment (DoE) approach. A two factor, three level (32) full factorial design has been applied; each variable was investi- gated at three levels to characterize their strength and interaction. The dried granules have been analyzed for their density, granule size and flowability. Additionally, the produced tablets have been investigated for: break- ing force, friability, disintegration time and t. of drug dissolution. The analysis of variance (ANOVA) showed that the two variables had a significant impact (p < 0.05) on granules and tablets characteristics, while only the binder concentration influenced the tablets friability. Furthermore, significant interactions (p < 0.05) between the two variables, for granules and tablets attributes, were also found. However, variables interaction showed minimal effect for granules flowability as well as tablets friability. Desirability function was carried out to opti- mize the variables under study to obtain product within the USP limit. It was found that the higher desirability (0.985) could be obtained at the medium level of PVP and low level of CCS. Ultimately, this study supplies the formulator with beneficial tools in selecting the proper level of binder and disintegrant to attain product with desired characteristics.

Active Subspaces of Airfoil Shape Parameterizations

NASA Astrophysics Data System (ADS)

Grey, Zachary J.; Constantine, Paul G.

2018-05-01

Design and optimization benefit from understanding the dependence of a quantity of interest (e.g., a design objective or constraint function) on the design variables. A low-dimensional active subspace, when present, identifies important directions in the space of design variables; perturbing a design along the active subspace associated with a particular quantity of interest changes that quantity more, on average, than perturbing the design orthogonally to the active subspace. This low-dimensional structure provides insights that characterize the dependence of quantities of interest on design variables. Airfoil design in a transonic flow field with a parameterized geometry is a popular test problem for design methodologies. We examine two particular airfoil shape parameterizations, PARSEC and CST, and study the active subspaces present in two common design quantities of interest, transonic lift and drag coefficients, under each shape parameterization. We mathematically relate the two parameterizations with a common polynomial series. The active subspaces enable low-dimensional approximations of lift and drag that relate to physical airfoil properties. In particular, we obtain and interpret a two-dimensional approximation of both transonic lift and drag, and we show how these approximation inform a multi-objective design problem.

Study of process variables associated with manufacturing hermetically-sealed nickel-cadmium cells

NASA Technical Reports Server (NTRS)

Miller, L.; Doan, D. J.; Carr, E. S.

1971-01-01

A program to determine and study the critical process variables associated with the manufacture of aerospace, hermetically-sealed, nickel-cadmium cells is described. The determination and study of the process variables associated with the positive and negative plaque impregnation/polarization process are emphasized. The experimental data resulting from the implementation of fractional factorial design experiments are analyzed by means of a linear multiple regression analysis technique. This analysis permits the selection of preferred levels for certain process variables to achieve desirable impregnated plaque characteristics.

Effects of Comparison and Game-Challenge on Sixth Graders' Algebra Variable Learning Achievement, Learning Attitude, and Meta-Cognitive Awareness

ERIC Educational Resources Information Center

Sun Lin, Hong-Zheng; Chiou, Guey-Fa

2017-01-01

This study examined the effects of comparison and game-challenge strategies on sixth graders' learning achievement of algebra variable, learning attitude towards algebra variable learning, and meta-cognitive awareness of algebra variable learning. A 2 × 2 factorial design was used, and 86 students were invited to participate in the experimental…

The Use of Race Variables in Genetic Studies of Complex Traits and the Goal of Reducing Health Disparities: A Transdisciplinary Perspective

ERIC Educational Resources Information Center

Shields, Alexandra E.; Fortun, Michael; Hammonds, Evelynn M.; King, Patricia A.; Lerman, Caryn; Rapp, Rayna; Sullivan, Patrick F.

2005-01-01

The use of racial variables in genetic studies has become a matter of intense public debate, with implications for research design and translation into practice. Using research on smoking as a springboard, the authors examine the history of racial categories, current research practices, and arguments for and against using race variables in genetic…

Does psychotherapy work with school-aged youth? A meta-analytic examination of moderator variables that influence therapeutic outcomes.

PubMed

Fedewa, Alicia L; Ahn, Soyeon; Reese, Robert J; Suarez, Marietta M; Macquoid, Ahjane; Davis, Matthew C; Prout, H Thompson

2016-06-01

The present study is a quantitative synthesis of the available literature to investigate the efficacy of psychotherapy for children's mental health outcomes. In particular, this study focuses on potential moderating variables-study design, treatment, client, and therapist characteristics-that may influence therapeutic outcomes for youth but have not been thoroughly accounted for in prior meta-analytic studies. An electronic search of relevant databases resulted in 190 unpublished and published studies that met criteria for inclusion in the analysis. Effect sizes differed by study design. Pre-post-test designs resulted in absolute magnitudes of treatment effects ranging from |-0.02| to |-0.76| while treatment versus control group comparison designs resulted in absolute magnitudes of treatment effects ranging from |-0.14| to |-2.39|. Changes in youth outcomes larger than 20% were found, irrespective of study design, for outcomes focused on psychosomatization (29% reduction), school attendance (25% increase), and stress (48% reduction). The magnitude of changes after psychotherapy ranged from 6% (externalizing problems) to 48% (stress). Several moderator variables significantly influenced psychotherapy treatment effect sizes, including frequency and length of treatment as well as treatment format. However, results did not support the superiority of a single type of intervention for most outcomes. Implications for therapy with school-aged youth and future research are discussed. Copyright © 2016 Society for the Study of School Psychology. Published by Elsevier Ltd. All rights reserved.

Multidisciplinary design optimization of aircraft wing structures with aeroelastic and aeroservoelastic constraints

NASA Astrophysics Data System (ADS)

Jung, Sang-Young

Design procedures for aircraft wing structures with control surfaces are presented using multidisciplinary design optimization. Several disciplines such as stress analysis, structural vibration, aerodynamics, and controls are considered simultaneously and combined for design optimization. Vibration data and aerodynamic data including those in the transonic regime are calculated by existing codes. Flutter analyses are performed using those data. A flutter suppression method is studied using control laws in the closed-loop flutter equation. For the design optimization, optimization techniques such as approximation, design variable linking, temporary constraint deletion, and optimality criteria are used. Sensitivity derivatives of stresses and displacements for static loads, natural frequency, flutter characteristics, and control characteristics with respect to design variables are calculated for an approximate optimization. The objective function is the structural weight. The design variables are the section properties of the structural elements and the control gain factors. Existing multidisciplinary optimization codes (ASTROS* and MSC/NASTRAN) are used to perform single and multiple constraint optimizations of fully built up finite element wing structures. Three benchmark wing models are developed and/or modified for this purpose. The models are tested extensively.

OPDOT: A computer program for the optimum preliminary design of a transport airplane

NASA Technical Reports Server (NTRS)

Sliwa, S. M.; Arbuckle, P. D.

1980-01-01

A description of a computer program, OPDOT, for the optimal preliminary design of transport aircraft is given. OPDOT utilizes constrained parameter optimization to minimize a performance index (e.g., direct operating cost per block hour) while satisfying operating constraints. The approach in OPDOT uses geometric descriptors as independent design variables. The independent design variables are systematically iterated to find the optimum design. The technical development of the program is provided and a program listing with sample input and output are utilized to illustrate its use in preliminary design. It is not meant to be a user's guide, but rather a description of a useful design tool developed for studying the application of new technologies to transport airplanes.

Small Business Leadership and Organizational Culture, Job Satisfaction and Performance: Correlational Research

ERIC Educational Resources Information Center

Frazier, Eugene

2013-01-01

This study investigated the relationship among organizational leadership styles (criterion variables), organizational culture, and employee job satisfaction, and organizational performance (predictor variables). The study research method was the quantitative method using a correlational research design that investigated the relationship among the…

Are glucose levels, glucose variability and autonomic control influenced by inspiratory muscle exercise in patients with type 2 diabetes? Study protocol for a randomized controlled trial.

PubMed

Schein, Aso; Correa, Aps; Casali, Karina Rabello; Schaan, Beatriz D

2016-01-20

Physical exercise reduces glucose levels and glucose variability in patients with type 2 diabetes. Acute inspiratory muscle exercise has been shown to reduce these parameters in a small group of patients with type 2 diabetes, but these results have yet to be confirmed in a well-designed study. The aim of this study is to investigate the effect of acute inspiratory muscle exercise on glucose levels, glucose variability, and cardiovascular autonomic function in patients with type 2 diabetes. This study will use a randomized clinical trial crossover design. A total of 14 subjects will be recruited and randomly allocated to two groups to perform acute inspiratory muscle loading at 2 % of maximal inspiratory pressure (PImax, placebo load) or 60 % of PImax (experimental load). Inspiratory muscle training could be a novel exercise modality to be used to decrease glucose levels and glucose variability. ClinicalTrials.gov NCT02292810 .

Comparison study on flexible pavement design using FAA (Federal Aviation Administration) and LCN (Load Classification Number) code in Ahmad Yani international airport’s runway

NASA Astrophysics Data System (ADS)

Santoso, S. E.; Sulistiono, D.; Mawardi, A. F.

2017-11-01

FAA code for airport design has been broadly used by Indonesian Ministry of Aviation since decades ago. However, there is not much comprehensive study about its relevance and efficiency towards current situation in Indonesia. Therefore, a further comparison study on flexible pavement design for airport runway using comparable method has become essential. The main focus of this study is to compare which method between FAA and LCN that offer the most efficient and effective way in runway pavement planning. The comparative methods in this study mainly use the variety of variable approach. FAA code for instance, will use the approach on the aircraft’s maximum take-off weight and annual departure. Whilst LCN code use the variable of equivalent single wheel load and tire pressure. Based on the variables mentioned above, a further classification and rated method will be used to determine which code is best implemented. According to the analysis, it is clear that FAA method is the most effective way to plan runway design in Indonesia with consecutively total pavement thickness of 127cm and LCN method total pavement thickness of 70cm. Although, FAA total pavement is thicker that LCN its relevance towards sustainable and pristine condition in the future has become an essential aspect to consider in design and planning.

Simple uncertainty propagation for early design phase aircraft sizing

NASA Astrophysics Data System (ADS)

Lenz, Annelise

Many designers and systems analysts are aware of the uncertainty inherent in their aircraft sizing studies; however, few incorporate methods to address and quantify this uncertainty. Many aircraft design studies use semi-empirical predictors based on a historical database and contain uncertainty -- a portion of which can be measured and quantified. In cases where historical information is not available, surrogate models built from higher-fidelity analyses often provide predictors for design studies where the computational cost of directly using the high-fidelity analyses is prohibitive. These surrogate models contain uncertainty, some of which is quantifiable. However, rather than quantifying this uncertainty, many designers merely include a safety factor or design margin in the constraints to account for the variability between the predicted and actual results. This can become problematic if a designer does not estimate the amount of variability correctly, which then can result in either an "over-designed" or "under-designed" aircraft. "Under-designed" and some "over-designed" aircraft will likely require design changes late in the process and will ultimately require more time and money to create; other "over-designed" aircraft concepts may not require design changes, but could end up being more costly than necessary. Including and propagating uncertainty early in the design phase so designers can quantify some of the errors in the predictors could help mitigate the extent of this additional cost. The method proposed here seeks to provide a systematic approach for characterizing a portion of the uncertainties that designers are aware of and propagating it throughout the design process in a procedure that is easy to understand and implement. Using Monte Carlo simulations that sample from quantified distributions will allow a systems analyst to use a carpet plot-like approach to make statements like: "The aircraft is 'P'% likely to weigh 'X' lbs or less, given the uncertainties quantified" without requiring the systems analyst to have substantial knowledge of probabilistic methods. A semi-empirical sizing study of a small single-engine aircraft serves as an example of an initial version of this simple uncertainty propagation. The same approach is also applied to a variable-fidelity concept study using a NASA-developed transonic Hybrid Wing Body aircraft.

Designing eHealth Applications to Reduce Cognitive Effort for Persons With Severe Mental Illness: Page Complexity, Navigation Simplicity, and Comprehensibility

PubMed Central

Spring, Michael R; Hanusa, Barbara H; Eack, Shaun M; Haas, Gretchen L

2017-01-01

Background eHealth technologies offer great potential for improving the use and effectiveness of treatments for those with severe mental illness (SMI), including schizophrenia and schizoaffective disorder. This potential can be muted by poor design. There is limited research on designing eHealth technologies for those with SMI, others with cognitive impairments, and those who are not technology savvy. We previously tested a design model, the Flat Explicit Design Model (FEDM), to create eHealth interventions for individuals with SMI. Subsequently, we developed the design concept page complexity, defined via the design variables we created of distinct topic areas, distinct navigation areas, and number of columns used to organize contents and the variables of text reading level, text reading ease (a newly added variable to the FEDM), and the number of hyperlinks and number of words on a page. Objective The objective of our study was to report the influence that the 19 variables of the FEDM have on the ability of individuals with SMI to use a website, ratings of a website’s ease of use, and performance on a novel usability task we created termed as content disclosure (a measure of the influence of a homepage’s design on the understanding user’s gain of a website). Finally, we assessed the performance of 3 groups or dimensions we developed that organize the 19 variables of the FEDM, termed as page complexity, navigational simplicity, and comprehensibility. Methods We measured 4 website usability outcomes: ability to find information, time to find information, ease of use, and a user’s ability to accurately judge a website’s contents. A total of 38 persons with SMI (chart diagnosis of schizophrenia or schizoaffective disorder) and 5 mental health websites were used to evaluate the importance of the new design concepts, as well as the other variables in the FEDM. Results We found that 11 of the FEDM’s 19 variables were significantly associated with all 4 usability outcomes. Most other variables were significantly related to 2 or 3 of these usability outcomes. With the 5 tested websites, 7 of the 19 variables of the FEDM overlapped with other variables, resulting in 12 distinct variable groups. The 3 design dimensions had acceptable coefficient alphas. Both navigational simplicity and comprehensibility were significantly related to correctly identifying whether information was available on a website. Page complexity and navigational simplicity were significantly associated with the ability and time to find information and ease-of-use ratings. Conclusions The 19 variables and 3 dimensions (page complexity, navigational simplicity, and comprehensibility) of the FEDM offer evidence-based design guidance intended to reduce the cognitive effort required to effectively use eHealth applications, particularly for persons with SMI, and potentially others, including those with cognitive impairments and limited skills or experience with technology. The new variables we examined (topic areas, navigational areas, columns) offer additional and very simple ways to improve simplicity. PMID:28057610

Obesity and the community food environment: a systematic review.

PubMed

Holsten, Joanna E

2009-03-01

To examine the relationship between obesity and the community and/or consumer food environment. A comprehensive literature search of multiple databases was conducted and seven studies were identified for review. Studies were selected if they measured BMI and environmental variables related to food outlets. Environmental variables included the geographic arrangement of food stores or restaurants in communities and consumer conditions such as food price and availability within each outlet. The study designs, methods, limitations and results related to obesity and the food environment were reviewed, and implications for future research were synthesized. The reviewed studies used cross-sectional designs to examine the community food environment defined as the number per capita, proximity or density of food outlets. Most studies indirectly identified food outlets through large databases. The studies varied substantially in sample populations, outcome variables, units of measurement and data analysis. Two studies did not find any significant association between obesity rates and community food environment variables. Five studies found significant results. Many of the studies were subject to limitations that may have mitigated the validity of the results. Research examining obesity and the community or consumer food environment is at an early stage. The most pertinent gaps include primary data at the individual level, direct measures of the environment, studies examining the consumer environment and study designs involving a time sequence. Future research should directly measure multiple levels of the food environment and key confounders at the individual level.

Recent progresses in outcome-dependent sampling with failure time data.

PubMed

Ding, Jieli; Lu, Tsui-Shan; Cai, Jianwen; Zhou, Haibo

2017-01-01

An outcome-dependent sampling (ODS) design is a retrospective sampling scheme where one observes the primary exposure variables with a probability that depends on the observed value of the outcome variable. When the outcome of interest is failure time, the observed data are often censored. By allowing the selection of the supplemental samples depends on whether the event of interest happens or not and oversampling subjects from the most informative regions, ODS design for the time-to-event data can reduce the cost of the study and improve the efficiency. We review recent progresses and advances in research on ODS designs with failure time data. This includes researches on ODS related designs like case-cohort design, generalized case-cohort design, stratified case-cohort design, general failure-time ODS design, length-biased sampling design and interval sampling design.

Recent progresses in outcome-dependent sampling with failure time data

PubMed Central

Ding, Jieli; Lu, Tsui-Shan; Cai, Jianwen; Zhou, Haibo

2016-01-01

An outcome-dependent sampling (ODS) design is a retrospective sampling scheme where one observes the primary exposure variables with a probability that depends on the observed value of the outcome variable. When the outcome of interest is failure time, the observed data are often censored. By allowing the selection of the supplemental samples depends on whether the event of interest happens or not and oversampling subjects from the most informative regions, ODS design for the time-to-event data can reduce the cost of the study and improve the efficiency. We review recent progresses and advances in research on ODS designs with failure time data. This includes researches on ODS related designs like case–cohort design, generalized case–cohort design, stratified case–cohort design, general failure-time ODS design, length-biased sampling design and interval sampling design. PMID:26759313

Application of Taguchi Design and Response Surface Methodology for Improving Conversion of Isoeugenol into Vanillin by Resting Cells of Psychrobacter sp. CSW4.

PubMed

Ashengroph, Morahem; Nahvi, Iraj; Amini, Jahanshir

2013-01-01

For all industrial processes, modelling, optimisation and control are the keys to enhance productivity and ensure product quality. In the current study, the optimization of process parameters for improving the conversion of isoeugenol to vanillin by Psychrobacter sp. CSW4 was investigated by means of Taguchi approach and Box-Behnken statistical design under resting cell conditions. Taguchi design was employed for screening the significant variables in the bioconversion medium. Sequentially, Box-Behnken design experiments under Response Surface Methodology (RSM) was used for further optimization. Four factors (isoeugenol, NaCl, biomass and tween 80 initial concentrations), which have significant effects on vanillin yield, were selected from ten variables by Taguchi experimental design. With the regression coefficient analysis in the Box-Behnken design, a relationship between vanillin production and four significant variables was obtained, and the optimum levels of the four variables were as follows: initial isoeugenol concentration 6.5 g/L, initial tween 80 concentration 0.89 g/L, initial NaCl concentration 113.2 g/L and initial biomass concentration 6.27 g/L. Under these optimized conditions, the maximum predicted concentration of vanillin was 2.25 g/L. These optimized values of the factors were validated in a triplicate shaking flask study and an average of 2.19 g/L for vanillin, which corresponded to a molar yield 36.3%, after a 24 h bioconversion was obtained. The present work is the first one reporting the application of Taguchi design and Response surface methodology for optimizing bioconversion of isoeugenol into vanillin under resting cell conditions.

Power maximization of variable-speed variable-pitch wind turbines using passive adaptive neural fault tolerant control

NASA Astrophysics Data System (ADS)

Habibi, Hamed; Rahimi Nohooji, Hamed; Howard, Ian

2017-09-01

Power maximization has always been a practical consideration in wind turbines. The question of how to address optimal power capture, especially when the system dynamics are nonlinear and the actuators are subject to unknown faults, is significant. This paper studies the control methodology for variable-speed variable-pitch wind turbines including the effects of uncertain nonlinear dynamics, system fault uncertainties, and unknown external disturbances. The nonlinear model of the wind turbine is presented, and the problem of maximizing extracted energy is formulated by designing the optimal desired states. With the known system, a model-based nonlinear controller is designed; then, to handle uncertainties, the unknown nonlinearities of the wind turbine are estimated by utilizing radial basis function neural networks. The adaptive neural fault tolerant control is designed passively to be robust on model uncertainties, disturbances including wind speed and model noises, and completely unknown actuator faults including generator torque and pitch actuator torque. The Lyapunov direct method is employed to prove that the closed-loop system is uniformly bounded. Simulation studies are performed to verify the effectiveness of the proposed method.

Investigating Lifelong Learning Dispositions of Students Studying English Language and Literature in Terms of Different Variables

ERIC Educational Resources Information Center

Elaldi, Senel

2015-01-01

This study aims to determine lifelong learning dispositions of English Language and Literature students in terms of gender, grade levels, and age variables. Descriptive research design was used. The study group consisted of 402 students studying English Language and Literature at Cumhuriyet University in Sivas, Turkey. Research data were collected…

Variable-cycle engines for supersonic cruise aircraft

NASA Technical Reports Server (NTRS)

Willis, E.

1976-01-01

Progress and the current status of the Variable Cycle Engine (VCE) study are reviewed with emphasis placed on the impact of technology advancements and design specifications. A large variety of VCE concepts are also examined.

Optimization of olive oil based O/W nanoemulsions prepared through ultrasonic homogenization: A response surface methodology approach.

PubMed

Mehmood, Tahir; Ahmad, Asif; Ahmed, Anwaar; Ahmed, Zaheer

2017-08-15

The present study was conducted to prepare co-surfactant free, olive-oil based alpha tocopherol nanoemulsions, using a food grade non-ionic surfactant. Response surface methodology (RSM) was used to determine the effects of independent variables (ultrasonic homogenization time, olive oil concentrations and surfactant contents) on different physico-chemical characteristics of O/W nanoemulsions. This study was carried out using a central composite design. The coefficients of determination were greater than 0.900 for all response variables and there were significant effects of independent variables on all responses. The optimum levels of independent variables for the preparation of nanoemulsions were 3min. ultrasonic homogenization time, 4% olive oil content and 2.08% surfactant concentration. The physico-chemical responses at these levels were 151.68nm particle size, 7.17% p-anisidine and 88.64% antioxidant activity. These results will help in design of nanoemulsions with optimum independent variables. Copyright © 2017 Elsevier Ltd. All rights reserved.

Impact damage resistance of composite fuselage structure, part 1

NASA Technical Reports Server (NTRS)

Dost, E. F.; Avery, W. B.; Ilcewicz, L. B.; Grande, D. H.; Coxon, B. R.

1992-01-01

The impact damage resistance of laminated composite transport aircraft fuselage structures was studied experimentally. A statistically based designed experiment was used to examine numerous material, laminate, structural, and extrinsic (e.g., impactor type) variables. The relative importance and quantitative measure of the effect of each variable and variable interactions on responses including impactor dynamic response, visibility, and internal damage state were determined. The study utilized 32 three-stiffener panels, each with a unique combination of material type, material forms, and structural geometry. Two manufacturing techniques, tow placement and tape lamination, were used to build panels representative of potential fuselage crown, keel, and lower side-panel designs. Various combinations of impactor variables representing various foreign-object-impact threats to the aircraft were examined. Impacts performed at different structural locations within each panel (e.g., skin midbay, stiffener attaching flange, etc.) were considered separate parallel experiments. The relationship between input variables, measured damage states, and structural response to this damage are presented including recommendations for materials and impact test methods for fuselage structure.

An Investigation of Selected Readiness Variables As Predictors of Reading Achievement at Second Grade Level.

ERIC Educational Resources Information Center

Seals, Caryl Neman

This study was designed to determine the relationship of selected readiness variables to achievement in reading at the second grade level. The readiness variables were environment, mathematics, letters and sounds, aural comprehension, visual perception, auditory perception, vocabulary and concepts, word meaning, listening, matching, alphabet,…

Culture, Organizational Learning and Selected Employee Background Variables in Small-Size Business Enterprises

ERIC Educational Resources Information Center

Graham, Carroll M.; Nafukho, Fredrick Muyia

2007-01-01

Purpose: The purpose of this study is to determine the relationship between four independent variables educational level, longevity, type of enterprise, and gender and the dependent variable culture, as a dimension that explains organizational learning readiness in seven small-size business enterprises. Design/methodology/approach: An exploratory…

Gender differences in foot shape: a study of Chinese young adults.

PubMed

Hong, Youlian; Wang, Lin; Xu, Dong Qing; Li, Jing Xian

2011-06-01

One important extrinsic factor that causes foot deformity and pain in women is footwear. Women's sports shoes are designed as smaller versions of men's shoes. Based on this, the current study aims to identify foot shape in 1,236 Chinese young adult men and 1,085 Chinese young adult women. Three-dimensional foot shape data were collected through video filming. Nineteen foot shape variables were measured, including girth (4 variables), length (4 variables), width (3 variables), height (7 variables), and angle (1 variable). A comparison of foot measures within the range of the common foot length (FL) categories indicates that women showed significantly smaller values of foot measures in width, height, and girth than men. Three foot types were classified, and distributions of different foot shapes within the same FL were found between women and men. Foot width, medial ball length, ball angle, and instep height showed significant differences among foot types in the same FL for both genders. There were differences in the foot shape between Chinese young women and men, which should be considered in the design of Chinese young adults' sports shoes.

Multivariate analysis in thoracic research.

PubMed

Mengual-Macenlle, Noemí; Marcos, Pedro J; Golpe, Rafael; González-Rivas, Diego

2015-03-01

Multivariate analysis is based in observation and analysis of more than one statistical outcome variable at a time. In design and analysis, the technique is used to perform trade studies across multiple dimensions while taking into account the effects of all variables on the responses of interest. The development of multivariate methods emerged to analyze large databases and increasingly complex data. Since the best way to represent the knowledge of reality is the modeling, we should use multivariate statistical methods. Multivariate methods are designed to simultaneously analyze data sets, i.e., the analysis of different variables for each person or object studied. Keep in mind at all times that all variables must be treated accurately reflect the reality of the problem addressed. There are different types of multivariate analysis and each one should be employed according to the type of variables to analyze: dependent, interdependence and structural methods. In conclusion, multivariate methods are ideal for the analysis of large data sets and to find the cause and effect relationships between variables; there is a wide range of analysis types that we can use.

Quality by design approach: application of artificial intelligence techniques of tablets manufactured by direct compression.

PubMed

Aksu, Buket; Paradkar, Anant; de Matas, Marcel; Ozer, Ozgen; Güneri, Tamer; York, Peter

2012-12-01

The publication of the International Conference of Harmonization (ICH) Q8, Q9, and Q10 guidelines paved the way for the standardization of quality after the Food and Drug Administration issued current Good Manufacturing Practices guidelines in 2003. "Quality by Design", mentioned in the ICH Q8 guideline, offers a better scientific understanding of critical process and product qualities using knowledge obtained during the life cycle of a product. In this scope, the "knowledge space" is a summary of all process knowledge obtained during product development, and the "design space" is the area in which a product can be manufactured within acceptable limits. To create the spaces, artificial neural networks (ANNs) can be used to emphasize the multidimensional interactions of input variables and to closely bind these variables to a design space. This helps guide the experimental design process to include interactions among the input variables, along with modeling and optimization of pharmaceutical formulations. The objective of this study was to develop an integrated multivariate approach to obtain a quality product based on an understanding of the cause-effect relationships between formulation ingredients and product properties with ANNs and genetic programming on the ramipril tablets prepared by the direct compression method. In this study, the data are generated through the systematic application of the design of experiments (DoE) principles and optimization studies using artificial neural networks and neurofuzzy logic programs.

The impact of extracurricular activities participation on youth delinquent behaviors: An instrumental variables approach.

PubMed

Han, Sehee; Lee, Jonathan; Park, Kyung-Gook

2017-07-01

The purpose of this study was to examine the association between extracurricular activities (EA) participation and youth delinquency while tackling an endogeneity problem of EA participation. Using survey data of 12th graders in South Korea (n = 1943), this study employed an instrumental variables approach to address the self-selection problem of EA participation as the data for this study was based on an observational study design. We found a positive association between EA participation and youth delinquency based on conventional regression analysis. By contrast, we found a negative association between EA participation and youth delinquency based on an instrumental variables approach. These results indicate that caution should be exercised when we interpret the effect of EA participation on youth delinquency based on observational study designs. Copyright © 2017 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.

Examining Preservice Science Teachers' Skills of Formulating Hypotheses and Identifying Variables

ERIC Educational Resources Information Center

Aydogdu, Bülent

2015-01-01

The aim of this study is to examine preservice science teachers' skills of formulating hypotheses and identifying variables. The research has a phenomenological research design. The data was gathered qualitatively. In this study, preservice science teachers were first given two scenarios (Scenario-1 & Scenario-2) containing two different…

Characteristics of Successful Community College Students

ERIC Educational Resources Information Center

Forman, Scheherazade West

2009-01-01

The purpose of this quantitative study was to find predictors of student success. Using a predictive correlational design, the intent of the study was to find the relationships between the dichotomous dependent variable with the categories, degree recipients and non-degree recipients, and the independent variables, student characteristics and risk…

The Impact of Workplace Learning on Job Satisfaction in Small US Commercial Banks

ERIC Educational Resources Information Center

Rowden, Robert W.; Conine, Clyde T., Jr.

2005-01-01

Purpose: This study aims to examine workplace learning and job satisfaction in small, commercial US banks. Design/methodology/approach: Survey data collection with correlational procedure. Findings: The study found a statistically significant relationship between the workplace learning variables and the job satisfaction variables. Research…

Variable pitch fan system for NASA/Navy research and technology aircraft

NASA Technical Reports Server (NTRS)

Ryan, W. P.; Black, D. M.; Yates, A. F.

1977-01-01

Preliminary design of a shaft driven, variable-pitch lift fan and lift-cruise fan was conducted for a V/STOL Research and Technology Aircraft. The lift fan and lift-cruise fan employed a common rotor of 157.5 cm diameter, 1.18 pressure ratio variable-pitch fan designed to operate at a rotor-tip speed of 284 mps. Fan performance maps were prepared and detailed aerodynamic characteristics were established. Cost/weight/risk trade studies were conducted for the blade and fan case. Structural sizing was conducted for major components and weights determined for both the lift and lift-cruise fans.

Genotypic variability enhances the reproducibility of an ecological study.

PubMed

Milcu, Alexandru; Puga-Freitas, Ruben; Ellison, Aaron M; Blouin, Manuel; Scheu, Stefan; Freschet, Grégoire T; Rose, Laura; Barot, Sebastien; Cesarz, Simone; Eisenhauer, Nico; Girin, Thomas; Assandri, Davide; Bonkowski, Michael; Buchmann, Nina; Butenschoen, Olaf; Devidal, Sebastien; Gleixner, Gerd; Gessler, Arthur; Gigon, Agnès; Greiner, Anna; Grignani, Carlo; Hansart, Amandine; Kayler, Zachary; Lange, Markus; Lata, Jean-Christophe; Le Galliard, Jean-François; Lukac, Martin; Mannerheim, Neringa; Müller, Marina E H; Pando, Anne; Rotter, Paula; Scherer-Lorenzen, Michael; Seyhun, Rahme; Urban-Mead, Katherine; Weigelt, Alexandra; Zavattaro, Laura; Roy, Jacques

2018-02-01

Many scientific disciplines are currently experiencing a 'reproducibility crisis' because numerous scientific findings cannot be repeated consistently. A novel but controversial hypothesis postulates that stringent levels of environmental and biotic standardization in experimental studies reduce reproducibility by amplifying the impacts of laboratory-specific environmental factors not accounted for in study designs. A corollary to this hypothesis is that a deliberate introduction of controlled systematic variability (CSV) in experimental designs may lead to increased reproducibility. To test this hypothesis, we had 14 European laboratories run a simple microcosm experiment using grass (Brachypodium distachyon L.) monocultures and grass and legume (Medicago truncatula Gaertn.) mixtures. Each laboratory introduced environmental and genotypic CSV within and among replicated microcosms established in either growth chambers (with stringent control of environmental conditions) or glasshouses (with more variable environmental conditions). The introduction of genotypic CSV led to 18% lower among-laboratory variability in growth chambers, indicating increased reproducibility, but had no significant effect in glasshouses where reproducibility was generally lower. Environmental CSV had little effect on reproducibility. Although there are multiple causes for the 'reproducibility crisis', deliberately including genetic variability may be a simple solution for increasing the reproducibility of ecological studies performed under stringently controlled environmental conditions.

Temporal Variability of Observed and Simulated Hyperspectral Earth Reflectance

NASA Technical Reports Server (NTRS)

Roberts, Yolanda; Pilewskie, Peter; Kindel, Bruce; Feldman, Daniel; Collins, William D.

2012-01-01

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a climate observation system designed to study Earth's climate variability with unprecedented absolute radiometric accuracy and SI traceability. Observation System Simulation Experiments (OSSEs) were developed using GCM output and MODTRAN to simulate CLARREO reflectance measurements during the 21st century as a design tool for the CLARREO hyperspectral shortwave imager. With OSSE simulations of hyperspectral reflectance, Feldman et al. [2011a,b] found that shortwave reflectance is able to detect changes in climate variables during the 21st century and improve time-to-detection compared to broadband measurements. The OSSE has been a powerful tool in the design of the CLARREO imager and for understanding the effect of climate change on the spectral variability of reflectance, but it is important to evaluate how well the OSSE simulates the Earth's present-day spectral variability. For this evaluation we have used hyperspectral reflectance measurements from the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY), a shortwave spectrometer that was operational between March 2002 and April 2012. To study the spectral variability of SCIAMACHY-measured and OSSE-simulated reflectance, we used principal component analysis (PCA), a spectral decomposition technique that identifies dominant modes of variability in a multivariate data set. Using quantitative comparisons of the OSSE and SCIAMACHY PCs, we have quantified how well the OSSE captures the spectral variability of Earth?s climate system at the beginning of the 21st century relative to SCIAMACHY measurements. These results showed that the OSSE and SCIAMACHY data sets share over 99% of their total variance in 2004. Using the PCs and the temporally distributed reflectance spectra projected onto the PCs (PC scores), we can study the temporal variability of the observed and simulated reflectance spectra. Multivariate time series analysis of the PC scores using techniques such as Singular Spectrum Analysis (SSA) and Multichannel SSA will provide information about the temporal variability of the dominant variables. Quantitative comparison techniques can evaluate how well the OSSE reproduces the temporal variability observed by SCIAMACHY spectral reflectance measurements during the first decade of the 21st century. PCA of OSSE-simulated reflectance can also be used to study how the dominant spectral variables change on centennial scales for forced and unforced climate change scenarios. To have confidence in OSSE predictions of the spectral variability of hyperspectral reflectance, it is first necessary for us to evaluate the degree to which the OSSE simulations are able to reproduce the Earth?s present-day spectral variability.

Enhancing Induction Coil Reliability

NASA Astrophysics Data System (ADS)

Kreter, K.; Goldstein, R.; Yakey, C.; Nemkov, V.

2014-12-01

In induction hardening, thermal fatigue is one of the main copper failure modes of induction heat treating coils. There have been papers published that describe this failure mode and others that describe some good design practices. The variables previously identified as the sources of thermal fatigue include radiation from the part surface, frequency, current, concentrator losses, water pressure and coil wall thickness. However, there is very little quantitative data on the factors that influence thermal fatigue in induction coils is available in the public domain. By using finite element analysis software this study analyzes the effect of common design variables of inductor cooling, and quantifies the relative importance of these variables. A comprehensive case study for a single shot induction coil with Fluxtrol A concentrator applied is used for the analysis.

Efficiency Study of NLS Base-Year Design. RTI-22U-884-3.

ERIC Educational Resources Information Center

Moore, R. P.; And Others

An efficiency study was conducted of the base year design used for the National Longitudinal Study of the High School Class of 1972 (NLS). Finding the optimal design involved a search for the numbers of sample schools and students that would maximize the variance at a given cost. Twenty-one variables describing students' plans, attitudes,…

Conceptualization and design of a variable-gravity research facility

NASA Technical Reports Server (NTRS)

1987-01-01

The goal is to provide facilities for the study of the effects of variable-gravity levels in reducing the physiological stresses upon the humans of long-term stay time in zero-g. The designs studied include: twin-tethered two module system with a central despun module with docking port and winch gear; and rigid arm tube facility using shuttle external tanks. Topics examined included: despun central capsule configuration, docking clearances, EVA requirements, crew selection, crew scheduling, food supply and preparation, waste handling, leisure use, biomedical issues, and psycho-social issues.

Continuous variable transmission and regenerative braking devices in bicycles utilizing magnetorheological fluids

NASA Astrophysics Data System (ADS)

Cheung, Wai Ming; Liao, Wei-Hsin

2013-04-01

The use of magnetorheological (MR) fluids in vehicles has been gaining popular recently due to its controllable nature, which gives automotive designers more dimensions of freedom in functional designs. However, not much attention has been paid to apply it to bicycles. This paper is aimed to study the feasibility of applying MR fluids in different dynamic parts of a bicycle such as the transmission and braking systems. MR continuous variable transmission (CVT) and power generator assisted in braking systems were designed and analyzed. Both prototypes were fabricated and tested to evaluate their performances. Experimental results showed that the proposed designs are promising to be used in bicycles.

Design and calibration of the carousel wind tunnel

NASA Technical Reports Server (NTRS)

Leach, R. N.; Greeley, R.; Iversen, J.; White, B.; Marshall, J. R.

1986-01-01

In the study of planetary aeolian processes the effect of gravity is not readily modeled. Gravity appears in the equations of particle motion along with interparticle forces but the two terms are not separable. A wind tunnel that would permit variable gravity would allow separation of the forces and aid greatly in understanding planetary aeolian processes. The design Carousel Wind Tunnel (CWT) allows for a long flow distance in a small sized tunnel since the test section is a continuo us circuit and allows for a variable pseudo gravity. A prototype design was built and calibrated to gain some understanding of the characteristics of the design and the results presented.

Design and calibration of the carousel wind tunnel

NASA Technical Reports Server (NTRS)

Leach, R. N.; Greeley, Ronald; Iversen, James D.; White, Bruce R.; Marshall, John R.

1987-01-01

In the study of planetary aeolian processes the effect of gravity is not readily modeled. Gravity appears in the equations of particle motion along with interparticle forces but the two terms are not separable. A wind tunnel that would permit variable gravity would allow separation of the forces and aid greatly in understanding planetary aeolian processes. The design of the Carousel Wind Tunnel (CWT) allows for a long flow distance in a small sized tunnel since the test section is a continuous circuit and allows for a variable pseudo-gravity. A prototype design was built and calibrated to gain some understanding of the characteristics of the design and the results presented.

Predictive and postdictive analysis of forage yield trials

USDA-ARS?s Scientific Manuscript database

Classical experimental design theory, the predominant treatment in most textbooks, promotes the use of blocking designs for control of spatial variability in field studies and other situations in which there is significant variation among heterogeneity among experimental units. Many blocking design...

Principals' Personal Variables and Information and Communication Technology Utilization in Federal Capital Territory Senior Secondary Schools, Abuja, Nigeria

ERIC Educational Resources Information Center

Ogunshola, Roseline Folashade; Adeniyi, Abiodun

2017-01-01

The study investigated principals' personal variables and information and communication technology utilization in Federal Capital Territory (FCT) senior secondary schools, Abuja, Nigeria. The study adopted the correlational research design. The study used a sample of 94 senior secondary schools (including public and private) in FCT. Stratified…

The Investigation of Science Process Skills of Science Teachers in Terms of Some Variables

ERIC Educational Resources Information Center

Aydogdu, Bülent

2015-01-01

This study aimed to investigate basic process skills, integrated process skills and overall science process skills of science teachers in terms of some variables. This study had a survey design. The study population consisted of 170 science teachers from a province located in the Central Anatolia Region of Turkey. The study data were obtained from…

Using the entire history in the analysis of nested case cohort samples.

PubMed

Rivera, C L; Lumley, T

2016-08-15

Countermatching designs can provide more efficient estimates than simple matching or case-cohort designs in certain situations such as when good surrogate variables for an exposure of interest are available. We extend pseudolikelihood estimation for the Cox model under countermatching designs to models where time-varying covariates are considered. We also implement pseudolikelihood with calibrated weights to improve efficiency in nested case-control designs in the presence of time-varying variables. A simulation study is carried out, which considers four different scenarios including a binary time-dependent variable, a continuous time-dependent variable, and the case including interactions in each. Simulation results show that pseudolikelihood with calibrated weights under countermatching offers large gains in efficiency if compared to case-cohort. Pseudolikelihood with calibrated weights yielded more efficient estimators than pseudolikelihood estimators. Additionally, estimators were more efficient under countermatching than under case-cohort for the situations considered. The methods are illustrated using the Colorado Plateau uranium miners cohort. Furthermore, we present a general method to generate survival times with time-varying covariates. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Robust optimization of a tandem grating solar thermal absorber

NASA Astrophysics Data System (ADS)

Choi, Jongin; Kim, Mingeon; Kang, Kyeonghwan; Lee, Ikjin; Lee, Bong Jae

2018-04-01

Ideal solar thermal absorbers need to have a high value of the spectral absorptance in the broad solar spectrum to utilize the solar radiation effectively. Majority of recent studies about solar thermal absorbers focus on achieving nearly perfect absorption using nanostructures, whose characteristic dimension is smaller than the wavelength of sunlight. However, precise fabrication of such nanostructures is not easy in reality; that is, unavoidable errors always occur to some extent in the dimension of fabricated nanostructures, causing an undesirable deviation of the absorption performance between the designed structure and the actually fabricated one. In order to minimize the variation in the solar absorptance due to the fabrication error, the robust optimization can be performed during the design process. However, the optimization of solar thermal absorber considering all design variables often requires tremendous computational costs to find an optimum combination of design variables with the robustness as well as the high performance. To achieve this goal, we apply the robust optimization using the Kriging method and the genetic algorithm for designing a tandem grating solar absorber. By constructing a surrogate model through the Kriging method, computational cost can be substantially reduced because exact calculation of the performance for every combination of variables is not necessary. Using the surrogate model and the genetic algorithm, we successfully design an effective solar thermal absorber exhibiting a low-level of performance degradation due to the fabrication uncertainty of design variables.

Overcoming ecologic bias using the two-phase study design.

PubMed

Wakefield, Jon; Haneuse, Sebastien J-P A

2008-04-15

Ecologic (aggregate) data are widely available and widely utilized in epidemiologic studies. However, ecologic bias, which arises because aggregate data cannot characterize within-group variability in exposure and confounder variables, can only be removed by supplementing ecologic data with individual-level data. Here the authors describe the two-phase study design as a framework for achieving this objective. In phase 1, outcomes are stratified by any combination of area, confounders, and error-prone (or discretized) versions of exposures of interest. Phase 2 data, sampled within each phase 1 stratum, provide accurate measures of exposure and possibly of additional confounders. The phase 1 aggregate-level data provide a high level of statistical power and a cross-classification by which individuals may be efficiently sampled in phase 2. The phase 2 individual-level data then provide a control for ecologic bias by characterizing the within-area variability in exposures and confounders. In this paper, the authors illustrate the two-phase study design by estimating the association between infant mortality and birth weight in several regions of North Carolina for 2000-2004, controlling for gender and race. This example shows that the two-phase design removes ecologic bias and produces gains in efficiency over the use of case-control data alone. The authors discuss the advantages and disadvantages of the approach.

78 FR 76629 - The National Children's Study, Vanguard (Pilot) Study; Submission for OMB Review; 30-Day Comment...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-18

..., revisions to existing Study visits, and the initiation of methodological substudies. The NCS Vanguard Study... design of the Main Study of the National Children's Study. Background: The National Children's Study is a... questionnaire containing key variables and designed to collect core data at every study visit contact from the...

A logical approach to optimize the nanostructured lipid carrier system of irinotecan: efficient hybrid design methodology

NASA Astrophysics Data System (ADS)

Mohan Negi, Lalit; Jaggi, Manu; Talegaonkar, Sushama

2013-01-01

Development of an effective formulation involves careful optimization of a number of excipient and process variables. Sometimes the number of variables is so large that even the most efficient optimization designs require a very large number of trials which put stress on costs as well as time. A creative combination of a number of design methods leads to a smaller number of trials. This study was aimed at the development of nanostructured lipid carriers (NLCs) by using a combination of different optimization methods. A total of 11 variables were first screened using the Plackett-Burman design for their effects on formulation characteristics like size and entrapment efficiency. Four out of 11 variables were found to have insignificant effects on the formulation parameters and hence were screened out. Out of the remaining seven variables, four (concentration of tween-80, lecithin, sodium taurocholate, and total lipid) were found to have significant effects on the size of the particles while the other three (phase ratio, drug to lipid ratio, and sonication time) had a higher influence on the entrapment efficiency. The first four variables were optimized for their effect on size using the Taguchi L9 orthogonal array. The optimized values of the surfactants and lipids were kept constant for the next stage, where the sonication time, phase ratio, and drug:lipid ratio were varied using the Box-Behnken design response surface method to optimize the entrapment efficiency. Finally, by performing only 38 trials, we have optimized 11 variables for the development of NLCs with a size of 143.52 ± 1.2 nm, zeta potential of -32.6 ± 0.54 mV, and 98.22 ± 2.06% entrapment efficiency.

The Salience of Selected Variables on Choice for Movie Attendance among High School Students.

ERIC Educational Resources Information Center

Austin, Bruce A.

A questionnaire was designed for a study assessing both the importance of 28 variables in movie attendance and the importance of movie-going as a leisure-time activity. Respondents were 130 ninth and twelfth grade students. The 28 variables were broadly organized into eight categories: movie production personnel, production elements, advertising,…

Variability in "DIBELS Next" Progress Monitoring Measures for Students at Risk for Reading Difficulties

ERIC Educational Resources Information Center

O'Keeffe, Breda V.; Bundock, Kaitlin; Kladis, Kristin L.; Yan, Rui; Nelson, Kat

2017-01-01

Previous research on curriculum-based measurement of oral reading fluency (CBM ORF) found high levels of variability around the estimates of students' fluency; however, little research has studied the issue of variability specifically with well-designed passage sets and a sample of students who scored below benchmark for the purpose of progress…

A variety of variables.

PubMed

Jupiter, Daniel C

2014-01-01

In designing studies and developing plans for analyses, we must consider which tests are appropriate for the types of variables we are using. Here I describe the types of variables available to us, and I briefly consider the appropriate tools to use in their analysis. Copyright © 2014 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

The Challenge of Reproducibility and Accuracy in Nutrition Research: Resources and Pitfalls1234

PubMed Central

Kuszak, Adam J; Williamson, John S; Hopp, D Craig; Betz, Joseph M

2016-01-01

Inconsistent and contradictory results from nutrition studies conducted by different investigators continue to emerge, in part because of the inherent variability of natural products, as well as the unknown and therefore uncontrolled variables in study populations and experimental designs. Given these challenges inherent in nutrition research, it is critical for the progress of the field that researchers strive to minimize variability within studies and enhance comparability between studies by optimizing the characterization, control, and reporting of products, reagents, and model systems used, as well as the rigor and reporting of experimental designs, protocols, and data analysis. Here we describe some recent developments relevant to research on plant-derived products used in nutrition research, highlight some resources for optimizing the characterization and reporting of research using these products, and describe some of the pitfalls that may be avoided by adherence to these recommendations. PMID:26980822

An exploratory study of organization design configurations in health care delivery organizations.

PubMed

Sheppeck, Mick; Militello, Jack

2014-01-01

Organizations are configurations of variables that support each other to achieve customer satisfaction. Based on Treacy and Wiersema (1995), we predicted the emergence of two configurations, one supporting a product leadership stance and one predicting the customer intimate approach from a set of 73 for profit health care clinics. In addition, we predicted the emergence of a configuration where the scores on most variables were near the mean for each variable. Using cluster analysis and discriminant function analysis, we identified three configurations: one a "master of two" strategy, one "stuck-in-the-middle," and one showing scores well below the mean on most variables. The implications for organization design and manager actions in the health care industry are discussed.

Understanding the context of healthcare utilization: assessing environmental and provider-related variables in the behavioral model of utilization.

PubMed Central

Phillips, K A; Morrison, K R; Andersen, R; Aday, L A

1998-01-01

OBJECTIVE: The behavioral model of utilization, developed by Andersen, Aday, and others, is one of the most frequently used frameworks for analyzing the factors that are associated with patient utilization of healthcare services. However, the use of the model for examining the context within which utilization occurs-the role of the environment and provider-related factors-has been largely neglected. OBJECTIVE: To conduct a systematic review and analysis to determine if studies of medical care utilization that have used the behavioral model during the last 20 years have included environmental and provider-related variables and the methods used to analyze these variables. We discuss barriers to the use of these contextual variables and potential solutions. DATA SOURCES: The Social Science Citation Index and Science Citation Index. We included all articles from 1975-1995 that cited any of three key articles on the behavioral model, that included all articles that were empirical analyses and studies of formal medical care utilization, and articles that specifically stated their use of the behavioral model (n = 139). STUDY DESIGN: Design was a systematic literature review. DATA ANALYSIS: We used a structured review process to code articles on whether they included contextual variables: (1) environmental variables (characteristics of the healthcare delivery system, external environment, and community-level enabling factors); and (2) provider-related variables (patient factors that may be influenced by providers and provider characteristics that interact with patient characteristics to influence utilization). We also examined the methods used in studies that included contextual variables. PRINCIPAL FINDINGS: Forty-five percent of the studies included environmental variables and 51 percent included provider-related variables. Few studies examined specific measures of the healthcare system or provider characteristics or used methods other than simple regression analysis with hierarchical entry of variables. Only 14 percent of studies analyzed the context of healthcare by including both environmental and provider-related variables as well as using relevant methods. CONCLUSIONS: By assessing whether and how contextual variables are used, we are able to highlight the contributions made by studies using these approaches, to identify variables and methods that have been relatively underused, and to suggest solutions to barriers in using contextual variables. PMID:9685123

An Algorithm for Integrated Subsystem Embodiment and System Synthesis

NASA Technical Reports Server (NTRS)

Lewis, Kemper

1997-01-01

Consider the statement,'A system has two coupled subsystems, one of which dominates the design process. Each subsystem consists of discrete and continuous variables, and is solved using sequential analysis and solution.' To address this type of statement in the design of complex systems, three steps are required, namely, the embodiment of the statement in terms of entities on a computer, the mathematical formulation of subsystem models, and the resulting solution and system synthesis. In complex system decomposition, the subsystems are not isolated, self-supporting entities. Information such as constraints, goals, and design variables may be shared between entities. But many times in engineering problems, full communication and cooperation does not exist, information is incomplete, or one subsystem may dominate the design. Additionally, these engineering problems give rise to mathematical models involving nonlinear functions of both discrete and continuous design variables. In this dissertation an algorithm is developed to handle these types of scenarios for the domain-independent integration of subsystem embodiment, coordination, and system synthesis using constructs from Decision-Based Design, Game Theory, and Multidisciplinary Design Optimization. Implementation of the concept in this dissertation involves testing of the hypotheses using example problems and a motivating case study involving the design of a subsonic passenger aircraft.

Wind-Tunnel Investigation of the Opening Characteristics, Drag, and Stability of Several Hemispherical Parachutes

NASA Technical Reports Server (NTRS)

Scher, Stanley E.; Gale, Lawrence J.

1948-01-01

An investigation has been conducted to determine the opening characteristics of several hemispherical parachutes and to study the influence of the parachute design variables on these opening characteristics. The effects of design variables on the drag and stability characteristics of the parachutes were also evaluated. The tests were made in the Langley 20-foot free-spinning tunnel and in the Langley 300 MPH 7 by 10-foot tunnel.

A quantitative analysis of statistical power identifies obesity endpoints for improved in vivo preclinical study design

PubMed Central

Selimkhanov, Jangir; Thompson, W. Clayton; Guo, Juen; Hall, Kevin D.; Musante, Cynthia J.

2017-01-01

The design of well-powered in vivo preclinical studies is a key element in building knowledge of disease physiology for the purpose of identifying and effectively testing potential anti-obesity drug targets. However, as a result of the complexity of the obese phenotype, there is limited understanding of the variability within and between study animals of macroscopic endpoints such as food intake and body composition. This, combined with limitations inherent in the measurement of certain endpoints, presents challenges to study design that can have significant consequences for an anti-obesity program. Here, we analyze a large, longitudinal study of mouse food intake and body composition during diet perturbation to quantify the variability and interaction of key metabolic endpoints. To demonstrate how conclusions can change as a function of study size, we show that a simulated pre-clinical study properly powered for one endpoint may lead to false conclusions based on secondary endpoints. We then propose guidelines for endpoint selection and study size estimation under different conditions to facilitate proper power calculation for a more successful in vivo study design. PMID:28392555

Multidisciplinary optimization of a controlled space structure using 150 design variables

NASA Technical Reports Server (NTRS)

James, Benjamin B.

1993-01-01

A controls-structures interaction design method is presented. The method coordinates standard finite-element structural analysis, multivariable controls, and nonlinear programming codes and allows simultaneous optimization of the structure and control system of a spacecraft. Global sensitivity equations are used to account for coupling between the disciplines. Use of global sensitivity equations helps solve optimization problems that have a large number of design variables and a high degree of coupling between disciplines. The preliminary design of a generic geostationary platform is used to demonstrate the multidisciplinary optimization method. Design problems using 15, 63, and 150 design variables to optimize truss member sizes and feedback gain values are solved and the results are presented. The goal is to reduce the total mass of the structure and the vibration control system while satisfying constraints on vibration decay rate. Incorporation of the nonnegligible mass of actuators causes an essential coupling between structural design variables and control design variables.

Interval estimation and optimal design for the within-subject coefficient of variation for continuous and binary variables

PubMed Central

Shoukri, Mohamed M; Elkum, Nasser; Walter, Stephen D

2006-01-01

Background In this paper we propose the use of the within-subject coefficient of variation as an index of a measurement's reliability. For continuous variables and based on its maximum likelihood estimation we derive a variance-stabilizing transformation and discuss confidence interval construction within the framework of a one-way random effects model. We investigate sample size requirements for the within-subject coefficient of variation for continuous and binary variables. Methods We investigate the validity of the approximate normal confidence interval by Monte Carlo simulations. In designing a reliability study, a crucial issue is the balance between the number of subjects to be recruited and the number of repeated measurements per subject. We discuss efficiency of estimation and cost considerations for the optimal allocation of the sample resources. The approach is illustrated by an example on Magnetic Resonance Imaging (MRI). We also discuss the issue of sample size estimation for dichotomous responses with two examples. Results For the continuous variable we found that the variance stabilizing transformation improves the asymptotic coverage probabilities on the within-subject coefficient of variation for the continuous variable. The maximum like estimation and sample size estimation based on pre-specified width of confidence interval are novel contribution to the literature for the binary variable. Conclusion Using the sample size formulas, we hope to help clinical epidemiologists and practicing statisticians to efficiently design reliability studies using the within-subject coefficient of variation, whether the variable of interest is continuous or binary. PMID:16686943

Research related to variable sweep aircraft development

NASA Technical Reports Server (NTRS)

Polhamus, E. C.; Toll, T. A.

1981-01-01

Development in high speed, variable sweep aircraft research is reviewed. The 1946 Langley wind tunnel studies related to variable oblique and variable sweep wings and results from the X-5 and the XF1OF variable sweep aircraft are discussed. A joint program with the British, evaluation of the British "Swallow", development of the outboard pivot wing/aft tail configuration concept by Langley, and the applied research program that followed and which provided the technology for the current, variable sweep military aircraft is outlined. The relative state of variable sweep as a design option is also covered.

78 FR 52548 - The National Children's Study, Vanguard (Pilot) Study Proposed Collection; 60-day Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-23

... the initiation of methodological substudies. The NCS Vanguard Study is a prospective, longitudinal pilot study of child health and development that will inform the design of the Main Study of the... variables and designed to collect core data at every study visit contact from the time that the enrolled...

Multidisciplinary design integration system for a supersonic transport aircraft

NASA Technical Reports Server (NTRS)

Dovi, A. R.; Wrenn, G. A.; Barthelemy, J.-F. M.; Coen, P. G.; Hall, L. E.

1992-01-01

An aircraft preliminary design system which provides the multidisciplinary communications and couplings between several engineering disciplines is described. A primary benefit of this system is to demonstrate advanced technology multidisciplinary design integration methodologies. The current version includes the disciplines of aerodynamics and structures. Contributing engineering disciplines are coupled using the Global Sensitivity Equation approach to influence the global design optimization problem. A high speed civil transport configuration is used for configuration trade studies. Forty four independent design variables are used to control the cross-sectional areas of wing rib and spar caps and the thicknesses of wingskincover panels. A total of 300 stress, strain, buckling and displacement behavioral constraints and minimum gages on the design variables were used to optimize the idealized wing structure. The goal of the designs to resize the wing cover panels and internal structure for minimum mass.

Black Male Labor Force Participation.

ERIC Educational Resources Information Center

Baer, Roger K.

This study attempts to test (via multiple regression analysis) hypothesized relationships between designated independent variables and age specific incidences of labor force participation for black male subpopulations in 54 Standard Metropolitan Statistical Areas. Leading independent variables tested include net migration, earnings, unemployment,…

Effects of sources of variability on sample sizes required for RCTs, applied to trials of lipid-altering therapies on carotid artery intima-media thickness.

PubMed

Gould, A Lawrence; Koglin, Joerg; Bain, Raymond P; Pinto, Cathy-Anne; Mitchel, Yale B; Pasternak, Richard C; Sapre, Aditi

2009-08-01

Studies measuring progression of carotid artery intima-media thickness (cIMT) have been used to estimate the effect of lipid-modifying therapies cardiovascular event risk. The likelihood that future cIMT clinical trials will detect a true treatment effect is estimated by leveraging results from prior studies. The present analyses assess the impact of between- and within-study variability based on currently published data from prior clinical studies on the likelihood that ongoing or future cIMT trials will detect the true treatment effect of lipid-modifying therapies. Published data from six contemporary cIMT studies (ASAP, ARBITER 2, RADIANCE 1, RADIANCE 2, ENHANCE, and METEOR) including data from a total of 3563 patients were examined. Bayesian and frequentist methods were used to assess the impact of between study variability on the likelihood of detecting true treatment effects on 1-year cIMT progression/regression and to provide a sample size estimate that would specifically compensate for the effect of between-study variability. In addition to the well-described within-study variability, there is considerable between-study variability associated with the measurement of annualized change in cIMT. Accounting for the additional between-study variability decreases the power for existing study designs. In order to account for the added between-study variability, it is likely that future cIMT studies would require a large increase in sample size in order to provide substantial probability (> or =90%) to have 90% power of detecting a true treatment effect.Limitation Analyses are based on study level data. Future meta-analyses incorporating patient-level data would be useful for confirmation. Due to substantial within- and between-study variability in the measure of 1-year change of cIMT, as well as uncertainty about progression rates in contemporary populations, future study designs evaluating the effect of new lipid-modifying therapies on atherosclerotic disease progression are likely to be challenged by large sample sizes in order to demonstrate a true treatment effect.

Investigation of Navier-Stokes Code Verification and Design Optimization

NASA Technical Reports Server (NTRS)

Vaidyanathan, Rajkumar

2004-01-01

With rapid progress made in employing computational techniques for various complex Navier-Stokes fluid flow problems, design optimization problems traditionally based on empirical formulations and experiments are now being addressed with the aid of computational fluid dynamics (CFD). To be able to carry out an effective CFD-based optimization study, it is essential that the uncertainty and appropriate confidence limits of the CFD solutions be quantified over the chosen design space. The present dissertation investigates the issues related to code verification, surrogate model-based optimization and sensitivity evaluation. For Navier-Stokes (NS) CFD code verification a least square extrapolation (LSE) method is assessed. This method projects numerically computed NS solutions from multiple, coarser base grids onto a freer grid and improves solution accuracy by minimizing the residual of the discretized NS equations over the projected grid. In this dissertation, the finite volume (FV) formulation is focused on. The interplay between the xi concepts and the outcome of LSE, and the effects of solution gradients and singularities, nonlinear physics, and coupling of flow variables on the effectiveness of LSE are investigated. A CFD-based design optimization of a single element liquid rocket injector is conducted with surrogate models developed using response surface methodology (RSM) based on CFD solutions. The computational model consists of the NS equations, finite rate chemistry, and the k-6 turbulence closure. With the aid of these surrogate models, sensitivity and trade-off analyses are carried out for the injector design whose geometry (hydrogen flow angle, hydrogen and oxygen flow areas and oxygen post tip thickness) is optimized to attain desirable goals in performance (combustion length) and life/survivability (the maximum temperatures on the oxidizer post tip and injector face and a combustion chamber wall temperature). A preliminary multi-objective optimization study is carried out using a geometric mean approach. Following this, sensitivity analyses with the aid of variance-based non-parametric approach and partial correlation coefficients are conducted using data available from surrogate models of the objectives and the multi-objective optima to identify the contribution of the design variables to the objective variability and to analyze the variability of the design variables and the objectives. In summary the present dissertation offers insight into an improved coarse to fine grid extrapolation technique for Navier-Stokes computations and also suggests tools for a designer to conduct design optimization study and related sensitivity analyses for a given design problem.

Optimization of process variables for decolorization of Disperse Yellow 211 by Bacillus subtilis using Box-Behnken design.

PubMed

Sharma, Praveen; Singh, Lakhvinder; Dilbaghi, Neeraj

2009-05-30

Decolorization of textile azo dye Disperse Yellow 211 (DY 211) was carried out from simulated aqueous solution by bacterial strain Bacillus subtilis. Response surface methodology (RSM), involving Box-Behnken design matrix in three most important operating variables; temperature, pH and initial dye concentration was successfully employed for the study and optimization of decolorization process. The total 17 experiments were conducted in the study towards the construction of a quadratic model. According to analysis of variance (ANOVA) results, the proposed model can be used to navigate the design space. Under optimized conditions the bacterial strain was able to decolorize DY 211 up to 80%. Model indicated that initial dye concentration of 100 mgl(-1), pH 7 and a temperature of 32.5 degrees C were found optimum for maximum % decolorization. Very high regression coefficient between the variables and the response (R(2)=0.9930) indicated excellent evaluation of experimental data by polynomial regression model. The combination of the three variables predicted through RSM was confirmed through confirmatory experiments, hence the bacterial strain holds a great potential for the treatment of colored textile effluents.

A Study on the Characteristics of Design Variables for IRSS Diffuser

NASA Astrophysics Data System (ADS)

Cho, Yong-Jin; Ko, Dae-Eun

2017-11-01

In modern naval ships, infrared signature suppression systems (IRSS) are installed to decrease the temperature of waste gas generated in propulsion engine and the metallic surface temperature of heated exhaust pipes. Generally, IRSS is composed of eductor, mixing tube, and diffuser. Diffuser serves to reduce the temperature by creating an air film using the pressure difference between internal gas and external air. In this study, design variables were selected by analyzing the diffuser and the characteristics of design variables that affect the performance of diffuser were examined using Taguchi experiment method. For the diffuser performance analysis, a heat flow analysis technique established in previous research was used. The IRSS performance evaluation was carried out based on the average area value of the metal surface temperature and the temperature of the exhaust gas at the outlet of the diffuser, which are variables directly related to the intensity of infrared signature in naval ships. It was verified that the exhaust gas temperature is greatly affected by changes in the diameter of the diffuser outlet, and the metal surface temperature of diffuser is greatly affected by changes in the number of diffuser rings.

Advancing Scientific Reasoning in Upper Elementary Classrooms: Direct Instruction Versus Task Structuring

NASA Astrophysics Data System (ADS)

Lazonder, Ard W.; Wiskerke-Drost, Sjanou

2015-02-01

Several studies found that direct instruction and task structuring can effectively promote children's ability to design unconfounded experiments. The present study examined whether the impact of these interventions extends to other scientific reasoning skills by comparing the inquiry activities of 55 fifth-graders randomly assigned to one of three conditions. Children in the control condition investigated a four-variable inquiry task without additional support. Performance of this task in the direct instruction condition was preceded by a short training in experimental design, whereas children in the task structuring condition, who did not receive the introductory training, were given a version of the task that addressed the four variables one at a time. Analysis of children's experimentation behavior confirmed that direct instruction and task structuring are equally effective and superior to unguided inquiry. Both interventions also evoked more determinate predictions and valid inferences. These findings demonstrate that the effect of short-term interventions designed to promote unconfounded experimentation extends beyond the control of variables.

Ultra compact spectrometer using linear variable filters

NASA Astrophysics Data System (ADS)

Dami, M.; De Vidi, R.; Aroldi, G.; Belli, F.; Chicarella, L.; Piegari, A.; Sytchkova, A.; Bulir, J.; Lemarquis, F.; Lequime, M.; Abel Tibérini, L.; Harnisch, B.

2017-11-01

The Linearly Variable Filters (LVF) are complex optical devices that, integrated in a CCD, can realize a "single chip spectrometer". In the framework of an ESA Study, a team of industries and institutes led by SELEX-Galileo explored the design principles and manufacturing techniques, realizing and characterizing LVF samples based both on All-Dielectric (AD) and Metal-Dielectric (MD) Coating Structures in the VNIR and SWIR spectral ranges. In particular the achieved performances on spectral gradient, transmission bandwidth and Spectral Attenuation (SA) are presented and critically discussed. Potential improvements will be highlighted. In addition the results of a feasibility study of a SWIR Linear Variable Filter are presented with the comparison of design prediction and measured performances. Finally criticalities related to the filter-CCD packaging are discussed. The main achievements reached during these activities have been: - to evaluate by design, manufacturing and test of LVF samples the achievable performances compared with target requirements; - to evaluate the reliability of the projects by analyzing their repeatability; - to define suitable measurement methodologies

Optimal Micro-Scale Secondary Flow Control for the Management of High Cycle Fatigue and Distortion in Compact Inlet Diffusers

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.; Keller, Dennis J.

2002-01-01

The purpose of this study on micro-scale secondary flow control (MSFC) is to study the aerodynamic behavior of micro-vane effectors through their factor (i.e., the design variable) interactions and to demonstrate how these statistical interactions, when brought together in an optimal manner, determine design robustness. The term micro-scale indicates the vane effectors are small in comparison to the local boundary layer height. Robustness in this situation means that it is possible to design fixed MSFC robust installation (i.e.. open loop) which operates well over the range of mission variables and is only marginally different from adaptive (i.e., closed loop) installation design, which would require a control system. The inherent robustness of MSFC micro-vane effector installation designs comes about because of their natural aerodynamic characteristics and the manner in which these characteristics are brought together in an optimal manner through a structured Response Surface Methodology design process.

Recommendations for Benchmarking Preclinical Studies of Nanomedicines.

PubMed

Dawidczyk, Charlene M; Russell, Luisa M; Searson, Peter C

2015-10-01

Nanoparticle-based delivery systems provide new opportunities to overcome the limitations associated with traditional small-molecule drug therapy for cancer and to achieve both therapeutic and diagnostic functions in the same platform. Preclinical trials are generally designed to assess therapeutic potential and not to optimize the design of the delivery platform. Consequently, progress in developing design rules for cancer nanomedicines has been slow, hindering progress in the field. Despite the large number of preclinical trials, several factors restrict comparison and benchmarking of different platforms, including variability in experimental design, reporting of results, and the lack of quantitative data. To solve this problem, we review the variables involved in the design of preclinical trials and propose a protocol for benchmarking that we recommend be included in in vivo preclinical studies of drug-delivery platforms for cancer therapy. This strategy will contribute to building the scientific knowledge base that enables development of design rules and accelerates the translation of new technologies. ©2015 American Association for Cancer Research.

Perspective: Recommendations for benchmarking pre-clinical studies of nanomedicines

PubMed Central

Dawidczyk, Charlene M.; Russell, Luisa M.; Searson, Peter C.

2015-01-01

Nanoparticle-based delivery systems provide new opportunities to overcome the limitations associated with traditional small molecule drug therapy for cancer, and to achieve both therapeutic and diagnostic functions in the same platform. Pre-clinical trials are generally designed to assess therapeutic potential and not to optimize the design of the delivery platform. Consequently, progress in developing design rules for cancer nanomedicines has been slow, hindering progress in the field. Despite the large number of pre-clinical trials, several factors restrict comparison and benchmarking of different platforms, including variability in experimental design, reporting of results, and the lack of quantitative data. To solve this problem, we review the variables involved in the design of pre-clinical trials and propose a protocol for benchmarking that we recommend be included in in vivo pre-clinical studies of drug delivery platforms for cancer therapy. This strategy will contribute to building the scientific knowledge base that enables development of design rules and accelerates the translation of new technologies. PMID:26249177

A parametric study of motor starting for a 2- to 10-kilowatt Brayton power system

NASA Technical Reports Server (NTRS)

Cantoni, D. A.

1971-01-01

A study of the motor starting of a Brayton cycle power system was conducted to provide estimates of system sensitivity to several controllable parameters. These sensitivity estimates were used as a basis for selection of an optimum motor-start scheme to be implemented on the 2- to 10-kilowatt Brayton power system designed and presently under test. The studies were conducted with an analog simulation of the Brayton power system and covered a range of frequencies from 400 Hz (33 percent design) to 1200 Hz (design), voltage-to-frequency ratios of 0.050 (50 percent design) to 0.100 (design), turbine-inlet temperatures of 800 K (1440 R, 70 percent design) to 1140 K (2060 deg R, design), and prestart pressure levels of 14.5 psia to 29.0 psia. These studies have shown the effect of selected system variables on motor starting. The final selection of motor-start variables can therefore be made on the basis of motor-start inverter complexity, battery size and weight, desired steady-state pressure level after startup, and other operational limitations. In general, the study showed the time required for motor starting to be inversely proportional to motor frequency, voltage, turbine-inlet temperature, and pressure level. An increase in any of these parameters decreases startup time.

A non-stationary cost-benefit based bivariate extreme flood estimation approach

NASA Astrophysics Data System (ADS)

Qi, Wei; Liu, Junguo

2018-02-01

Cost-benefit analysis and flood frequency analysis have been integrated into a comprehensive framework to estimate cost effective design values. However, previous cost-benefit based extreme flood estimation is based on stationary assumptions and analyze dependent flood variables separately. A Non-Stationary Cost-Benefit based bivariate design flood estimation (NSCOBE) approach is developed in this study to investigate influence of non-stationarities in both the dependence of flood variables and the marginal distributions on extreme flood estimation. The dependence is modeled utilizing copula functions. Previous design flood selection criteria are not suitable for NSCOBE since they ignore time changing dependence of flood variables. Therefore, a risk calculation approach is proposed based on non-stationarities in both marginal probability distributions and copula functions. A case study with 54-year observed data is utilized to illustrate the application of NSCOBE. Results show NSCOBE can effectively integrate non-stationarities in both copula functions and marginal distributions into cost-benefit based design flood estimation. It is also found that there is a trade-off between maximum probability of exceedance calculated from copula functions and marginal distributions. This study for the first time provides a new approach towards a better understanding of influence of non-stationarities in both copula functions and marginal distributions on extreme flood estimation, and could be beneficial to cost-benefit based non-stationary bivariate design flood estimation across the world.

Feasibility study of a cosmetic cream added with aqueous extract and oil from date (Phoenix dactylifera L.) fruit seed using experimental design.

PubMed

Lecheb, Fatma; Benamara, Salem

2015-01-01

This article reports on the feasibility study of a cosmetic cream added with aqueous extract and oil from date (Phoenix dactylifera L.) fruit seed using experimental design. First, the mixture design was applied to optimize the cosmetic formula. The responses (dependent variables) were the spreadability (YSp) and viscosity (YVis), the factors (independent variables) being the weight proportions of the fatty phase (X1), the aqueous date seed extract (X2), and the beeswax (X3). Second, the cosmetic stability study was conducted by applying a full factorial design. Here, three responses were considered [spreadability (Sp), viscosity (Vis), and peroxide index (PI)], the independent variables being the concentration of the date seed oil (DSO) (x1), storage temperature (x2), and storage time (x3). Results showed that in the case of mixture design, the second-order polynomial equations correctly described experimental data. Globally, results show that there is a relatively wide composition range to ensure a suitable cosmetic cream from the point of view of Sp and Vis. Regarding the cosmetic stability, the storage time was found to be the most influential factor on both Vis and PI, which are considered here as indicators of physical and chemical stability of the emulsion, respectively. Finally, the elaborated and commercial cosmetics were compared in terms of pH, Sp, and centrifugation test (Ct).

Variability aware compact model characterization for statistical circuit design optimization

NASA Astrophysics Data System (ADS)

Qiao, Ying; Qian, Kun; Spanos, Costas J.

2012-03-01

Variability modeling at the compact transistor model level can enable statistically optimized designs in view of limitations imposed by the fabrication technology. In this work we propose an efficient variabilityaware compact model characterization methodology based on the linear propagation of variance. Hierarchical spatial variability patterns of selected compact model parameters are directly calculated from transistor array test structures. This methodology has been implemented and tested using transistor I-V measurements and the EKV-EPFL compact model. Calculation results compare well to full-wafer direct model parameter extractions. Further studies are done on the proper selection of both compact model parameters and electrical measurement metrics used in the method.

77 FR 4569 - Revision to Proposed Collection; Comment Request; National Institute of Child Health and Human...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-30

... Information Collection: The purpose of the proposed methodological study is to continue the Vanguard phase of... design of the Main Study of the National Children's Study. Background The National Children's Study is a... questionnaire containing key variables and designed to collect core data at every study visit contact from the...

Numerical investigation of the variable nozzle effect on the mixed flow turbine performance characteristics

NASA Astrophysics Data System (ADS)

Meziri, B.; Hamel, M.; Hireche, O.; Hamidou, K.

2016-09-01

There are various matching ways between turbocharger and engine, the variable nozzle turbine is the most significant method. The turbine design must be economic with high efficiency and large capacity over a wide range of operational conditions. These design intents are used in order to decrease thermal load and improve thermal efficiency of the engine. This paper presents an original design method of a variable nozzle vane for mixed flow turbines developed from previous experimental and numerical studies. The new device is evaluated with a numerical simulation over a wide range of rotational speeds, pressure ratios, and different vane angles. The compressible turbulent steady flow is solved using the ANSYS CFX software. The numerical results agree well with experimental data in the nozzleless configuration. In the variable nozzle case, the results show that the turbine performance characteristics are well accepted in different open positions and improved significantly in low speed regime and at low pressure ratio.

Grid sensitivity capability for large scale structures

NASA Technical Reports Server (NTRS)

Nagendra, Gopal K.; Wallerstein, David V.

1989-01-01

The considerations and the resultant approach used to implement design sensitivity capability for grids into a large scale, general purpose finite element system (MSC/NASTRAN) are presented. The design variables are grid perturbations with a rather general linking capability. Moreover, shape and sizing variables may be linked together. The design is general enough to facilitate geometric modeling techniques for generating design variable linking schemes in an easy and straightforward manner. Test cases have been run and validated by comparison with the overall finite difference method. The linking of a design sensitivity capability for shape variables in MSC/NASTRAN with an optimizer would give designers a powerful, automated tool to carry out practical optimization design of real life, complicated structures.

Variable Complexity Structural Optimization of Shells

NASA Technical Reports Server (NTRS)

Haftka, Raphael T.; Venkataraman, Satchi

1999-01-01

Structural designers today face both opportunities and challenges in a vast array of available analysis and optimization programs. Some programs such as NASTRAN, are very general, permitting the designer to model any structure, to any degree of accuracy, but often at a higher computational cost. Additionally, such general procedures often do not allow easy implementation of all constraints of interest to the designer. Other programs, based on algebraic expressions used by designers one generation ago, have limited applicability for general structures with modem materials. However, when applicable, they provide easy understanding of design decisions trade-off. Finally, designers can also use specialized programs suitable for designing efficiently a subset of structural problems. For example, PASCO and PANDA2 are panel design codes, which calculate response and estimate failure much more efficiently than general-purpose codes, but are narrowly applicable in terms of geometry and loading. Therefore, the problem of optimizing structures based on simultaneous use of several models and computer programs is a subject of considerable interest. The problem of using several levels of models in optimization has been dubbed variable complexity modeling. Work under NASA grant NAG1-2110 has been concerned with the development of variable complexity modeling strategies with special emphasis on response surface techniques. In addition, several modeling issues for the design of shells of revolution were studied.

Variable Complexity Structural Optimization of Shells

NASA Technical Reports Server (NTRS)

Haftka, Raphael T.; Venkataraman, Satchi

1998-01-01

Structural designers today face both opportunities and challenges in a vast array of available analysis and optimization programs. Some programs such as NASTRAN, are very general, permitting the designer to model any structure, to any degree of accuracy, but often at a higher computational cost. Additionally, such general procedures often do not allow easy implementation of all constraints of interest to the designer. Other programs, based on algebraic expressions used by designers one generation ago, have limited applicability for general structures with modem materials. However, when applicable, they provide easy understanding of design decisions trade-off. Finally, designers can also use specialized programs suitable for designing efficiently a subset of structural problems. For example, PASCO and PANDA2 are panel design codes, which calculate response and estimate failure much more efficiently than general-purpose codes, but are narrowly applicable in terms of geometry and loading. Therefore, the problem of optimizing structures based on simultaneous use of several models and computer programs is a subject of considerable interest. The problem of using several levels of models in optimization has been dubbed variable complexity modeling. Work under NASA grant NAG1-1808 has been concerned with the development of variable complexity modeling strategies with special emphasis on response surface techniques. In addition several modeling issues for the design of shells of revolution were studied.

Intraclass Correlation Coefficients in Hierarchical Design Studies with Discrete Response Variables: A Note on a Direct Interval Estimation Procedure

ERIC Educational Resources Information Center

Raykov, Tenko; Marcoulides, George A.

2015-01-01

A latent variable modeling procedure that can be used to evaluate intraclass correlation coefficients in two-level settings with discrete response variables is discussed. The approach is readily applied when the purpose is to furnish confidence intervals at prespecified confidence levels for these coefficients in setups with binary or ordinal…

An Inquiry into Situational Interest in a Tenth Grade History Class: Lesson Design and Implementation from Berlyne and Bergin Perspectives

ERIC Educational Resources Information Center

Morgan, Christine L.

2010-01-01

Using a "grounded theory" approach, this classroom-based empirical research study attempted to understand if using Berlyne's "collative variables" and Bergin's "situational factors" (external variables) in a learning sequence would "catch/trigger" and "hold" situational interest in students. A collative variable is a property of a stimulus that…

Olive fruits and vacuum impregnation, an interesting combination for dietetic iron enrichment.

PubMed

Zunin, Paola; Turrini, Federica; Leardi, Riccardo; Boggia, Raffaella

2017-02-01

In this study vacuum impregnation (VI) was employed for the iron enrichment of olive fruits, which are very interesting as food vehicle for VI mineral supplementation for the porosity of their pulp. NaFeEDTA was chosen for olives fortification since it prevents iron from binding with compounds that could hinder it from being efficiently absorbed and since it causes few organoleptic problems. In order to improve the efficiency of the VI process, several parameters of the whole process were studied by design of experiment techniques. First of all D-optimal design was employed for a preliminary screening of the most significant process variables and showed that the concentration of VI solution was by far the most significant process variable, though its time in contact with olives was also significant. A factorial design was then applied to the remaining variables and it showed that the speed of the addition of VI solution was also significant. Finally, the application of a face centered composite design to the three selected variables allowed to detect processing conditions leading to final iron contents of 1.5-3 mg/g, corresponding to an introduction of 10-15 mg Fe with four or five fortified olive fruits. No effect on olive taste was observed at these concentrations. The results showed that olive fruits were the most interesting vehicles for the supplementation of both iron and other minerals.

Design of effective interventions for smoking cessation through financial and non-financial incentives.

PubMed

Balderrama, Fanor; Longo, Christopher J

2017-11-01

Smoking has a tremendous negative impact on the Canadian economy and contributes to growing costs in the healthcare system. Efforts to reduce smoking rates may therefore reduce strain on the healthcare system and free up scarce resources. Academic literature on economic smoking cessation incentives presents a countless variety of interventions that have met with varying degrees of success. This study reviews six different variables used in the design of incentives in smoking cessation interventions: direction, form, magnitude, certainty, recipient grouping, and target demographic. The purpose of this study is to provide analysis and recommendations about the contribution of each variable into the overall effectiveness of smoking cessation programs and help health leaders design better interventions according to their specific needs.

Exploring the interaction of patient activation and message design variables: message frame and presentation mode influence on the walking behavior of patients with type 2 diabetes.

PubMed

Ledford, Christy J W

2012-10-01

Examining interpersonal (physician-patient) communication strategies for promoting walking exercise to patients with type 2 diabetes assigned to primary care clinics, the study evaluated two message design variables--frame and presentation mode--as influencers of communication and adoption success. The single-site, four-week, prospective intervention study followed a 2×3 factorial, non-equivalent comparison group quasi-experimental design. Results showed frame was significantly related to steps walked; however, when including patient activation as an interaction, frame was non-significant. The model including patient activation interactions, however, detected significant mode effects on behavior. Results provide evidence that statistics are most effectively used with activated patients.

Cooled variable nozzle radial turbine for rotor craft applications

NASA Technical Reports Server (NTRS)

Rogo, C.

1981-01-01

An advanced, small 2.27 kb/sec (5 lbs/sec), high temperature, variable area radial turbine was studied for a rotor craft application. Variable capacity cycles including single-shaft and free-turbine engine configurations were analyzed to define an optimum engine design configuration. Parametric optimizations were made on cooled and uncooled rotor configurations. A detailed structural and heat transfer analysis was conducted to provide a 4000-hour life HP turbine with material properties of the 1988 time frame. A pivoted vane and a moveable sidewall geometry were analyzed. Cooling and variable geometry penalties were included in the cycle analysis. A variable geometry free-turbine engine configuration with a design 1477K (2200 F) inlet temperature and a compressor pressure ratio of 16:1 was selected. An uncooled HP radial turbine rotor with a moveable sidewall nozzle showed the highest performance potential for a time weighted duty cycle.

Influence of hydroxypropyl methylcellulose on drug release pattern of a gastroretentive floating drug delivery system using a 3(2) full factorial design.

PubMed

Swain, Kalpana; Pattnaik, Satyanarayan; Mallick, Subrata; Chowdary, Korla Appana

2009-01-01

In the present investigation, controlled release gastroretentive floating drug delivery system of theophylline was developed employing response surface methodology. A 3(2) randomized full factorial design was developed to study the effect of formulation variables like various viscosity grades and contents of hydroxypropyl methylcellulose (HPMC) and their interactions on response variables. The floating lag time for all nine experimental trial batches were less than 2 min and floatation time of more than 12 h. Theophylline release from the polymeric matrix system followed non-Fickian anomalous transport. Multiple regression analysis revealed that both viscosity and content of HPMC had statistically significant influence on all dependent variables but the effect of these variables found to be nonlinear above certain threshold values.

Bio-Social Variables as Predictors of Teacher Union Leaders' Adherence to Democratic Principles in Ogun State, Nigeria

ERIC Educational Resources Information Center

Fejoh, Johnson

2016-01-01

This study investigated the influence of bio-social variables - educational status, age and family socio-economic background on teacher union leaders' adherence to democratic principles in Ogun State of Nigeria. The study employed the ex-post-facto research design. Five hypotheses were generated and tested using an instrument titled "union…

The Impact of Selected Academic and Demographic Variables on Mathematics College Readiness Predicted by ACT

ERIC Educational Resources Information Center

Smith, Marcia

2013-01-01

The purpose of the study was to determine the degree to which academic and demographic variables affected the ACT results used in determining college readiness. This quantitative research study followed a non-experimental correlational design. A multiple regression was used to analyze archival data to determine the impact the combined Arkansas…

Identification of Prospective Science Teachers' Mathematical-Logical Structures in Reference to Magnetism

ERIC Educational Resources Information Center

Yilmaz, Ismail

2014-01-01

This paper is a qualitative case study designed to identify prospective science teachers' mathematical-logical structures on the basis of their knowledge and achievement levels in magnetism. The study also made an attempt to reveal the effects of knowledge-level variables and procedural variables, which were considered to be potential…

Predictions: From Public School Teacher Salaries to Student Outcomes.

ERIC Educational Resources Information Center

Murgo, Nicholas J.; Walsh, Tammy King

A study of 28 school districts in Rhode Island was done in 1992 to examine the hypothesis that there is a positive correlation between teacher salaries and state aid. The study was originally designed to gather information about teacher salaries and the variables related to them, but was expanded to cover student outcomes and variables related to…

Theory and Design Tools For Studies of Reactions to Abrupt Changes in Noise Exposure

NASA Technical Reports Server (NTRS)

Fields, James M.; Ehrlich, Gary E.; Zador, Paul; Shepherd, Kevin P. (Technical Monitor)

2000-01-01

Study plans, a pre-tested questionnaire, a sample design evaluation tool, a community publicity monitoring plan, and a theoretical framework have been developed to support combined social/acoustical surveys of residents' reactions to an abrupt change in environmental noise, Secondary analyses of more than 20 previous surveys provide estimates of three parameters of a study simulation model; within individual variability, between study wave variability, and between neighborhood variability in response to community noise. The simulation model predicts the precision of the results from social surveys of reactions to noise, including changes in noise. When the study simulation model analyzed the population distribution, noise exposure environments and feasible noise measurement program at a proposed noise change survey site, it was concluded that the site could not yield sufficient precise estimates of human reaction model to justify conducting a survey. Additional secondary analyses determined that noise reactions are affected by the season of the social survey.

Spatial Variation in Soil Properties among North American Ecosystems and Guidelines for Sampling Designs

PubMed Central

Loescher, Henry; Ayres, Edward; Duffy, Paul; Luo, Hongyan; Brunke, Max

2014-01-01

Soils are highly variable at many spatial scales, which makes designing studies to accurately estimate the mean value of soil properties across space challenging. The spatial correlation structure is critical to develop robust sampling strategies (e.g., sample size and sample spacing). Current guidelines for designing studies recommend conducting preliminary investigation(s) to characterize this structure, but are rarely followed and sampling designs are often defined by logistics rather than quantitative considerations. The spatial variability of soils was assessed across ∼1 ha at 60 sites. Sites were chosen to represent key US ecosystems as part of a scaling strategy deployed by the National Ecological Observatory Network. We measured soil temperature (Ts) and water content (SWC) because these properties mediate biological/biogeochemical processes below- and above-ground, and quantified spatial variability using semivariograms to estimate spatial correlation. We developed quantitative guidelines to inform sample size and sample spacing for future soil studies, e.g., 20 samples were sufficient to measure Ts to within 10% of the mean with 90% confidence at every temperate and sub-tropical site during the growing season, whereas an order of magnitude more samples were needed to meet this accuracy at some high-latitude sites. SWC was significantly more variable than Ts at most sites, resulting in at least 10× more SWC samples needed to meet the same accuracy requirement. Previous studies investigated the relationship between the mean and variability (i.e., sill) of SWC across space at individual sites across time and have often (but not always) observed the variance or standard deviation peaking at intermediate values of SWC and decreasing at low and high SWC. Finally, we quantified how far apart samples must be spaced to be statistically independent. Semivariance structures from 10 of the 12-dominant soil orders across the US were estimated, advancing our continental-scale understanding of soil behavior. PMID:24465377

Work engagement in Magnet(®)-designated hospitals: Exploring social and institutional demographics of RNs to optimize improvement efforts.

PubMed

Wonder, Amy Hagedorn

2013-12-01

This study analyzed and evaluated relationships between work engagement (WE) and social/institutional demographic variables of RNs in Magnet(®)-designated hospitals. Organizational structures of Magnet-designated hospitals are recognized to promote engagement of RNs. Because little is known about relationships between WE and the social/institutional demographics of nurses, this study focused on age (generation), gender, education, shift, hours worked per week, percentage of time in direct patient care, and nursing unit. A convenience sample of hospital RNs (n = 220) completed 2 surveys to measure WE and demographic variables in this descriptive correlational study. Shift was significantly related to RN engagement; however, age, gender, education, hours worked per week, percentage of time in direct patient care, and nursing unit were not. This study provides empirical evidence about the relationships between WE and social/institutional characteristics of RNs. The findings are relevant to patients, nurses, nurse leaders, and organizations.

The Causal Effects of Father Absence

PubMed Central

McLanahan, Sara; Tach, Laura; Schneider, Daniel

2014-01-01

The literature on father absence is frequently criticized for its use of cross-sectional data and methods that fail to take account of possible omitted variable bias and reverse causality. We review studies that have responded to this critique by employing a variety of innovative research designs to identify the causal effect of father absence, including studies using lagged dependent variable models, growth curve models, individual fixed effects models, sibling fixed effects models, natural experiments, and propensity score matching models. Our assessment is that studies using more rigorous designs continue to find negative effects of father absence on offspring well-being, although the magnitude of these effects is smaller than what is found using traditional cross-sectional designs. The evidence is strongest and most consistent for outcomes such as high school graduation, children’s social-emotional adjustment, and adult mental health. PMID:24489431

Effect analysis of design variables on the disc in a double-eccentric butterfly valve.

PubMed

Kang, Sangmo; Kim, Da-Eun; Kim, Kuk-Kyeom; Kim, Jun-Oh

2014-01-01

We have performed a shape optimization of the disc in an industrial double-eccentric butterfly valve using the effect analysis of design variables to enhance the valve performance. For the optimization, we select three performance quantities such as pressure drop, maximum stress, and mass (weight) as the responses and three dimensions regarding the disc shape as the design variables. Subsequently, we compose a layout of orthogonal array (L16) by performing numerical simulations on the flow and structure using a commercial package, ANSYS v13.0, and then make an effect analysis of the design variables on the responses using the design of experiments. Finally, we formulate a multiobjective function consisting of the three responses and then propose an optimal combination of the design variables to maximize the valve performance. Simulation results show that the disc thickness makes the most significant effect on the performance and the optimal design provides better performance than the initial design.

Self Efficacy and Some Demographic Variables as Predictors of Occupational Stress among Primary School Teachers in Delta State of Nigeria

ERIC Educational Resources Information Center

Akpochafo, G. O.

2014-01-01

This study investigated self efficacy and some demographic variables as predictors of occupational stress among primary school teachers in Delta State. Three hypotheses were formulated to guide the study. The study adopted a descriptive survey design that utilized an expost-facto research type. A sample of one hundred and twenty primary school…

The Effects of Word Processing Software on User Satisfaction: An Empirical Study of Micro, Mini, and Mainframe Computers Using an Interactive Artificial Intelligence Expert-System.

ERIC Educational Resources Information Center

Rushinek, Avi; Rushinek, Sara

1984-01-01

Describes results of a system rating study in which users responded to WPS (word processing software) questions. Study objectives were data collection and evaluation of variables; statistical quantification of WPS's contribution (along with other variables) to user satisfaction; design of an expert system to evaluate WPS; and database update and…

Investigation of the History Education Researches in Turkey in Terms of Some Variables (Master's Theses and Dissertations Sample)

ERIC Educational Resources Information Center

Elban, Mehmet

2017-01-01

The purpose of this research study is to examine the master's theses and dissertations carried out about history education research in Turkey in terms of certain variables. The study is a qualitative research and it used documentary research design as a research method. The population of the research study is the master's theses and dissertations…

Analytic Thermoelectric Couple Modeling: Variable Material Properties and Transient Operation

NASA Technical Reports Server (NTRS)

Mackey, Jonathan A.; Sehirlioglu, Alp; Dynys, Fred

2015-01-01

To gain a deeper understanding of the operation of a thermoelectric couple a set of analytic solutions have been derived for a variable material property couple and a transient couple. Using an analytic approach, as opposed to commonly used numerical techniques, results in a set of useful design guidelines. These guidelines can serve as useful starting conditions for further numerical studies, or can serve as design rules for lab built couples. The analytic modeling considers two cases and accounts for 1) material properties which vary with temperature and 2) transient operation of a couple. The variable material property case was handled by means of an asymptotic expansion, which allows for insight into the influence of temperature dependence on different material properties. The variable property work demonstrated the important fact that materials with identical average Figure of Merits can lead to different conversion efficiencies due to temperature dependence of the properties. The transient couple was investigated through a Greens function approach; several transient boundary conditions were investigated. The transient work introduces several new design considerations which are not captured by the classic steady state analysis. The work helps to assist in designing couples for optimal performance, and also helps assist in material selection.

Design of experiments utilization to map the processing capabilities of a micro-spray dryer: particle design and throughput optimization in support of drug discovery.

PubMed

Ormes, James D; Zhang, Dan; Chen, Alex M; Hou, Shirley; Krueger, Davida; Nelson, Todd; Templeton, Allen

2013-02-01

There has been a growing interest in amorphous solid dispersions for bioavailability enhancement in drug discovery. Spray drying, as shown in this study, is well suited to produce prototype amorphous dispersions in the Candidate Selection stage where drug supply is limited. This investigation mapped the processing window of a micro-spray dryer to achieve desired particle characteristics and optimize throughput/yield. Effects of processing variables on the properties of hypromellose acetate succinate were evaluated by a fractional factorial design of experiments. Parameters studied include solid loading, atomization, nozzle size, and spray rate. Response variables include particle size, morphology and yield. Unlike most other commercial small-scale spray dryers, the ProCepT was capable of producing particles with a relatively wide mean particle size, ca. 2-35 µm, allowing material properties to be tailored to support various applications. In addition, an optimized throughput of 35 g/hour with a yield of 75-95% was achieved, which affords to support studies from Lead-identification/Lead-optimization to early safety studies. A regression model was constructed to quantify the relationship between processing parameters and the response variables. The response surface curves provide a useful tool to design processing conditions, leading to a reduction in development time and drug usage to support drug discovery.

A Survey to Examine Teachers' Perceptions of Design Dispositions, Lesson Design Practices, and Their Relationships with Technological Pedagogical Content Knowledge (TPACK)

ERIC Educational Resources Information Center

Koh, Joyce Hwee Ling; Chai, Ching Sing; Hong, Huang-Yao; Tsai, Chin-Chung

2015-01-01

This study investigates 201 Singaporean teachers' perceptions of their technological pedagogical content knowledge (TPACK), lesson design practices, and design dispositions through a survey instrument. Investigation of these constructs reveal important variables influencing teachers' perceptions of TPACK which have not yet been explored. The…

Energy monitoring in gins

USDA-ARS?s Scientific Manuscript database

Energy costs are the second largest source of variable costs for cotton gins, accounting for 27% of variable costs. Energy use has typically not been a major consideration in gin design, and previous studies of energy use have utilized instantaneous readings or aggregated season-long values. In this...

Energy Monitoring in Gins - 2011

USDA-ARS?s Scientific Manuscript database

Energy costs are the second largest source of variable costs for gins, accounting for 27% of variable costs. Energy use has typically not been a major consideration in gin design and previous studies of energy use have utilized instantaneous readings or aggregated season-long values. Electricity u...

Electricity use patterns in cotton gins

USDA-ARS?s Scientific Manuscript database

Energy costs are the second largest source of variable costs for cotton gins, with electricity accounting for 18% of variable costs. Energy use has typically not been a major consideration in gin design and previous studies of energy use have utilized instantaneous readings or aggregated season-lon...

Quality by design: optimization of a freeze-drying cycle via design space in case of heterogeneous drying behavior and influence of the freezing protocol.

PubMed

Pisano, Roberto; Fissore, Davide; Barresi, Antonello A; Brayard, Philippe; Chouvenc, Pierre; Woinet, Bertrand

2013-02-01

This paper shows how to optimize the primary drying phase, for both product quality and drying time, of a parenteral formulation via design space. A non-steady state model, parameterized with experimentally determined heat and mass transfer coefficients, is used to define the design space when the heat transfer coefficient varies with the position of the vial in the array. The calculations recognize both equipment and product constraints, and also take into account model parameter uncertainty. Examples are given of cycles designed for the same formulation, but varying the freezing conditions and the freeze-dryer scale. These are then compared in terms of drying time. Furthermore, the impact of inter-vial variability on design space, and therefore on the optimized cycle, is addressed. With this regard, a simplified method is presented for the cycle design, which reduces the experimental effort required for the system qualification. The use of mathematical modeling is demonstrated to be very effective not only for cycle development, but also for solving problem of process transfer. This study showed that inter-vial variability remains significant when vials are loaded on plastic trays, and how inter-vial variability can be taken into account during process design.

Quality by design: optimization of a liquid filled pH-responsive macroparticles using Draper-Lin composite design.

PubMed

Rafati, Hasan; Talebpour, Zahra; Adlnasab, Laleh; Ebrahimi, Samad Nejad

2009-07-01

In this study, pH responsive macroparticles incorporating peppermint oil (PO) were prepared using a simple emulsification/polymer precipitation technique. The formulations were examined for their properties and the desired quality was then achieved using a quality by design (QBD) approach. For this purpose, a Draper-Lin small composite design study was employed in order to investigate the effect of four independent variables, including the PO to water ratio, the concentration of pH sensitive polymer (hydroxypropyl methylcellulose phthalate), acid and plasticizer concentrations, on the encapsulation efficiency and PO loading. The analysis of variance showed that the polymer concentration was the most important variable on encapsulation efficiency (p < 0.05). The multiple regression analysis of the results led to equations that adequately described the influence of the independent variables on the selected responses. Furthermore, the desirability function was employed as an effective tool for transforming each response separately and encompassing all of these responses in an overall desirability function for global optimization of the encapsulation process. The optimized macroparticles were predicted to yield 93.4% encapsulation efficiency and 72.8% PO loading, which were remarkably close to the experimental values of 89.2% and 69.5%, consequently.

Design Expert Supported Mathematical Optimization and Predictability Study of Buccoadhesive Pharmaceutical Wafers of Loratadine

PubMed Central

Dey, Surajit; Parcha, Versha; Bhattacharya, Shiv Sankar; Ghosh, Amitava

2013-01-01

Objective. The objective of this work encompasses the application of the response surface approach in the development of buccoadhesive pharmaceutical wafers of Loratadine (LOR). Methods. Experiments were performed according to a 32 factorial design to evaluate the effects of buccoadhesive polymer, sodium alginate (A), and lactose monohydrate as ingredient, of hydrophilic matrix former (B) on the bioadhesive force, disintegration time, percent (%) swelling index, and time taken for 70% drug release (t 70%). The effect of the two independent variables on the response variables was studied by response surface plots and contour plots generated by the Design-Expert software. The desirability function was used to optimize the response variables. Results. The compatibility between LOR and the wafer excipients was confirmed by differential scanning calorimetry, FTIR spectroscopy, and X-ray diffraction (XRD) analysis. Bioadhesion force, measured with TAXT2i texture analyzer, showed that the wafers had a good bioadhesive property which could be advantageous for retaining the drug into the buccal cavity. Conclusion. The observed responses taken were in agreement with the experimental values, and Loratadine wafers were produced with less experimental trials, and a patient compliant product was achieved with the concept of formulation by design. PMID:23781498

Design Optimization of a Variable-Speed Power Turbine

NASA Technical Reports Server (NTRS)

Hendricks, Eric S.; Jones, Scott M.; Gray, Justin S.

2014-01-01

NASA's Rotary Wing Project is investigating technologies that will enable the development of revolutionary civil tilt rotor aircraft. Previous studies have shown that for large tilt rotor aircraft to be viable, the rotor speeds need to be slowed significantly during the cruise portion of the flight. This requirement to slow the rotors during cruise presents an interesting challenge to the propulsion system designer as efficient engine performance must be achieved at two drastically different operating conditions. One potential solution to this challenge is to use a transmission with multiple gear ratios and shift to the appropriate ratio during flight. This solution will require a large transmission that is likely to be maintenance intensive and will require a complex shifting procedure to maintain power to the rotors at all times. An alternative solution is to use a fixed gear ratio transmission and require the power turbine to operate efficiently over the entire speed range. This concept is referred to as a variable-speed power-turbine (VSPT) and is the focus of the current study. This paper explores the design of a variable speed power turbine for civil tilt rotor applications using design optimization techniques applied to NASA's new meanline tool, the Object-Oriented Turbomachinery Analysis Code (OTAC).

Application of Statistic Experimental Design to Assess the Effect of Gammairradiation Pre-Treatment on the Drying Characteristics and Qualities of Wheat

NASA Astrophysics Data System (ADS)

Yu, Yong; Wang, Jun

Wheat, pretreated by 60Co gamma irradiation, was dried by hot-air with irradiation dosage 0-3 kGy, drying temperature 40-60 °C, and initial moisture contents 19-25% (drying basis). The drying characteristics and dried qualities of wheat were evaluated based on drying time, average dehydration rate, wet gluten content (WGC), moisture content of wet gluten (MCWG)and titratable acidity (TA). A quadratic rotation-orthogonal composite experimental design, with three variables (at five levels) and five response functions, and analysis method were employed to study the effect of three variables on the individual response functions. The five response functions (drying time, average dehydration rate, WGC, MCWG, TA) correlated with these variables by second order polynomials consisting of linear, quadratic and interaction terms. A high correlation coefficient indicated the suitability of the second order polynomial to predict these response functions. The linear, interaction and quadratic effects of three variables on the five response functions were all studied.

Anti-buckling design of variable stiffness composite cylinder under combined loading based on the multi-objective optimization method

NASA Astrophysics Data System (ADS)

Zheng, Y.; Chen, J.

2018-06-01

Variable stiffness composite structures take full advantages of composite’s design ability. An enlarged design space will make the structure’s performance more excellent. Through an optimal design of a variable stiffness cylinder, the buckling capacity of the cylinder will be increased as compared with its constant stiffness counterpart. In this paper, variable stiffness composite cylinders sustaining combined loadings are considered, and the optimization is conducted based on the multi-objective optimization method. The results indicate that variable stiffness cylinder’s loading capacity is increased significantly as compared with the constant stiffness, especially when an inhomogeneous loading is considered.

Commonality between Reduced Gravity and Microgravity Habitats for Long Duration Missions

NASA Technical Reports Server (NTRS)

Howard, Robert

2014-01-01

Many conceptual studies for long duration missions beyond Earth orbit have assumed unique habitat designs for each destination and for transit habitation. This may not be the most effective approach. A variable gravity habitat, one designed for use in microgravity, lunar, Martian, and terrestrial environments may provide savings that offset the loss of environment-specific optimization. However, a brief analysis of selected flown spacecraft and Constellation-era conceptual habitat designs suggests that one cannot simply lift a habitat from one environment and place it in another that it was not designed for without incurring significant human performance compromises. By comparison, a conceptual habitat based on the Skylab II framework but designed specifically to accommodate variable gravity environments can be shown to yield significant advantages while incurring only minimal human performance compromises.

Observed Score Linear Equating with Covariates

ERIC Educational Resources Information Center

Branberg, Kenny; Wiberg, Marie

2011-01-01

This paper examined observed score linear equating in two different data collection designs, the equivalent groups design and the nonequivalent groups design, when information from covariates (i.e., background variables correlated with the test scores) was included. The main purpose of the study was to examine the effect (i.e., bias, variance, and…

Variable slew-rate spiral design: theory and application to peak B(1) amplitude reduction in 2D RF pulse design.

PubMed

Xu, Dan; King, Kevin F; Liang, Zhi-Pei

2007-10-01

A new class of spiral trajectories called variable slew-rate spirals is proposed. The governing differential equations for a variable slew-rate spiral are derived, and both numeric and analytic solutions to the equations are given. The primary application of variable slew-rate spirals is peak B(1) amplitude reduction in 2D RF pulse design. The reduction of peak B(1) amplitude is achieved by changing the gradient slew-rate profile, and gradient amplitude and slew-rate constraints are inherently satisfied by the design of variable slew-rate spiral gradient waveforms. A design example of 2D RF pulses is given, which shows that under the same hardware constraints the RF pulse using a properly chosen variable slew-rate spiral trajectory can be much shorter than that using a conventional constant slew-rate spiral trajectory, thus having greater immunity to resonance frequency offsets.

Optimal lay-up design of variable stiffness laminated composite plates by a layer-wise optimization technique

NASA Astrophysics Data System (ADS)

Houmat, A.

2018-02-01

The optimal lay-up design for the maximum fundamental frequency of variable stiffness laminated composite plates is investigated using a layer-wise optimization technique. The design variables are two fibre orientation angles per ply. Thin plate theory is used in conjunction with a p-element to calculate the fundamental frequencies of symmetrically and antisymmetrically laminated composite plates. Comparisons with existing optimal solutions for constant stiffness symmetrically laminated composite plates show excellent agreement. It is observed that the maximum fundamental frequency can be increased considerably using variable stiffness design as compared to constant stiffness design. In addition, optimal lay-ups for the maximum fundamental frequency of variable stiffness symmetrically and antisymmetrically laminated composite plates with different aspect ratios and various combinations of free, simply supported and clamped edge conditions are presented. These should prove a useful benchmark for optimal lay-ups of variable stiffness laminated composite plates.

Closed loop supply chain network design with fuzzy tactical decisions

NASA Astrophysics Data System (ADS)

Sherafati, Mahtab; Bashiri, Mahdi

2016-09-01

One of the most strategic and the most significant decisions in supply chain management is reconfiguration of the structure and design of the supply chain network. In this paper, a closed loop supply chain network design model is presented to select the best tactical and strategic decision levels simultaneously considering the appropriate transportation mode in activated links. The strategic decisions are made for a long term; thus, it is more satisfactory and more appropriate when the decision variables are considered uncertain and fuzzy, because it is more flexible and near to the real world. This paper is the first research which considers fuzzy decision variables in the supply chain network design model. Moreover, in this study a new fuzzy optimization approach is proposed to solve a supply chain network design problem with fuzzy tactical decision variables. Finally, the proposed approach and model are verified using several numerical examples. The comparison of the results with other existing approaches confirms efficiency of the proposed approach. Moreover the results confirms that by considering the vagueness of tactical decisions some properties of the supply chain network will be improved.

Organizational variables on nurses' job performance in Turkey: nursing assessments.

PubMed

Top, Mehmet

2013-01-01

The purpose of this study was to describe the influence of organizational variables on hospital staff nurses' job performance as reported by staff nurses in two cities in Turkey. Hospital ownership status, employment status were examined for their effect on this influence. The reported influence of organizational variables on job performance was measured by a questionnaire developed for this study. Nurses were asked to evaluate the influence of 28 organizational variables on their job performance using a five-point Likert-type scale (1- Never effective, 5- Very effective). The study used comparative and descriptive study design. The staff nurses who were included in this study were 831 hospital staff nurses. Descriptive statistics, frequencies, t-test, ANOVA and factor analysis were used for data analysis. The study showed the relative importance of the 28 organizational variables in influencing nurses' job performance. Nurses in this study reported that workload and technological support are the most influential organizational variables on their job performance. Factor analysis yielded a five-factor model that explained 53.99% of total variance. Administratively controllable influence job organizational variables influence job performance of nurses in different magnitude.

Study of the human/ITS interface issues on the design of traffic information bulletin board and traffic control signal displays

DOT National Transportation Integrated Search

2002-10-01

The success of automation for intelligent transportation systems is ultimately contingent upon the Interface between the users (humans) and the system (ITS). The issues of variable message signs (VMS) and traffic signal device (TSD) design were studi...

Testing Multiple Outcomes in Repeated Measures Designs

ERIC Educational Resources Information Center

Lix, Lisa M.; Sajobi, Tolulope

2010-01-01

This study investigates procedures for controlling the familywise error rate (FWR) when testing hypotheses about multiple, correlated outcome variables in repeated measures (RM) designs. A content analysis of RM research articles published in 4 psychology journals revealed that 3 quarters of studies tested hypotheses about 2 or more outcome…

ALTERNATIVE EXPOSURE MEASUREMENT DESIGNS TO IMPROVE EPIDEMIOLOGICAL STUDY DESIGNS: DETERMINANTS OF TEMPORAL VARIABILITY IN ENVIRONMENTAL CONCENTRATIONS, EXPOSURES, AND BIOMARKERS

EPA Science Inventory

The National Human Exposure Assessment Survey in Maryland (NHEXAS-MD) was a longitudinal study of multimedia exposure to metals, pesticides, and polycyclic aromatic compounds (PAHs). Measurements were made and questionnaires were concurrently administered to identify sources o...

Linking Brief Functional Analysis to Intervention Design in General Education Settings

ERIC Educational Resources Information Center

Ishuin, Tifanie

2009-01-01

This study focused on the utility and applicability of brief functional analysis in general education settings. The purpose of the study was to first identify the environmental variables maintaining noncompliance through a brief functional analysis, and then to design and implement a functionally equivalent intervention. The participant exhibited…

Design studies of continuously variable transmissions for electric vehicles

NASA Technical Reports Server (NTRS)

Parker, R. J.; Loewenthal, S. H.; Fischer, G. K.

1981-01-01

Preliminary design studies were performed on four continuously variable transmission (CVT) concepts for use with a flywheel equipped electric vehicle of 1700 kg gross weight. Requirements of the CVT's were a maximum torque of 450 N-m (330 lb-ft), a maximum output power of 75 kW (100 hp), and a flywheel speed range of 28,000 to 14,000 rpm. Efficiency, size, weight, cost, reliability, maintainability, and controls were evaluated for each of the four concepts which included a steel V-belt type, a flat rubber belt type, a toroidal traction type, and a cone roller traction type. All CVT's exhibited relatively high calculated efficiencies (68 percent to 97 percent) over a broad range of vehicle operating conditions. Estimated weight and size of these transmissions were comparable to or less than equivalent automatic transmission. The design of each concept was carried through the design layout stage.

Application of design of experiments for formulation development and mechanistic evaluation of iontophoretic tacrine hydrochloride delivery.

PubMed

Patel, Niketkumar; Jain, Shashank; Madan, Parshotam; Lin, Senshang

2016-11-01

The objective of this investigation is to develop mathematical equation to understand the impact of variables and establish statistical control over transdermal iontophoretic delivery of tacrine hydrochloride. In addition, possibility of using conductivity measurements as a tool of predicting ionic mobility of the participating ions for the application of iontophoretic delivery was explored. Central composite design was applied to study effect of independent variables like current strength, buffer molarity, and drug concentration on iontophoretic tacrine permeation flux. Molar conductivity was determined to evaluate electro-migration of tacrine ions with application of Kohlrausch's law. The developed mathematic equation not only reveals drug concentration as the most significant variable regulating tacrine permeation, followed by current strength and buffer molarity, but also is capable to optimize tacrine permeation with respective combination of independent variables to achieve desired therapeutic plasma concentration of tacrine in treatment of Alzheimer's disease. Moreover, relative higher mobility of sodium and chloride ions was observed as compared to estimated tacrine ion mobility. This investigation utilizes the design of experiment approach and extends the primary understanding of imapct of electronic and formulation variables on the tacrine permeation for the formulation development of iontophoretic tacrine delivery.

Sensitivity study of Space Station Freedom operations cost and selected user resources

NASA Technical Reports Server (NTRS)

Accola, Anne; Fincannon, H. J.; Williams, Gregory J.; Meier, R. Timothy

1990-01-01

The results of sensitivity studies performed to estimate probable ranges for four key Space Station parameters using the Space Station Freedom's Model for Estimating Space Station Operations Cost (MESSOC) are discussed. The variables examined are grouped into five main categories: logistics, crew, design, space transportation system, and training. The modification of these variables implies programmatic decisions in areas such as orbital replacement unit (ORU) design, investment in repair capabilities, and crew operations policies. The model utilizes a wide range of algorithms and an extensive trial logistics data base to represent Space Station operations. The trial logistics data base consists largely of a collection of the ORUs that comprise the mature station, and their characteristics based on current engineering understanding of the Space Station. A nondimensional approach is used to examine the relative importance of variables on parameters.

A quantitative analysis of statistical power identifies obesity end points for improved in vivo preclinical study design.

PubMed

Selimkhanov, J; Thompson, W C; Guo, J; Hall, K D; Musante, C J

2017-08-01

The design of well-powered in vivo preclinical studies is a key element in building the knowledge of disease physiology for the purpose of identifying and effectively testing potential antiobesity drug targets. However, as a result of the complexity of the obese phenotype, there is limited understanding of the variability within and between study animals of macroscopic end points such as food intake and body composition. This, combined with limitations inherent in the measurement of certain end points, presents challenges to study design that can have significant consequences for an antiobesity program. Here, we analyze a large, longitudinal study of mouse food intake and body composition during diet perturbation to quantify the variability and interaction of the key metabolic end points. To demonstrate how conclusions can change as a function of study size, we show that a simulated preclinical study properly powered for one end point may lead to false conclusions based on secondary end points. We then propose the guidelines for end point selection and study size estimation under different conditions to facilitate proper power calculation for a more successful in vivo study design.

Design and process of the EMA Cohort Study: the value of antenatal education in childbirth and breastfeeding

PubMed Central

Paz-Pascual, Carmen; Pinedo, Isabel Artieta; Grandes, Gonzalo; de Gamboa, Gurutze Remiro Fernandez; Hermosilla, Itziar Odriozola; de la Hera, Amaia Bacigalupe; Gordon, Janire Payo; Garcia, Guadalupe Manzano; de Pedro, Magdalena Ureta

2008-01-01

Background Antenatal education (AE) started more than 30 years ago with the purpose of decreasing pain during childbirth. Epidural anaesthesia has achieved this objective, and the value of AE is therefore currently questioned. This article describes the protocol and process of a study designed to assess AE results today. Methods/Design A prospective study was designed in which a cohort of 616 nulliparous pregnant women attending midwife offices of the Basque Health Service were followed for 13 months. Three exposure groups were considered based on the number of AE sessions attended: (a) women attending no session, (b) women attending 1 to 4, and (c) women attending 5 or more sessions. Sociodemographic, personality, and outcome variables related to childbirth and breastfeeding were measured. It was expected 40% of pregnant women not to have participated in any AE session. However, 93% had attended at least one session. This low exposure variability decreased statistical power of the study as compared to the initially planned power. Despite this, there was a greater than 80% power for detecting as significant differences between exposure groups of, for instance, 10% in continuation of breastfeeding at one and a half months and in visits for false labour. Women attending more sessions were seen to have a mean higher age and educational level, and to belong to a higher socioeconomic group (p < 0.01). Follow-up was completed in 99% of participants. Discussion Adequate prior estimation of variability in the exposure under study is essential for designing cohort studies. Sociodemographic characteristics may play a confounding role in studies assessing AE and should be controlled in design and analyses. Quality control during the study process and continued collaboration from both public system midwives and eligible pregnant women resulted in a negligible loss rate. PMID:18435856

An Integrated Optimization Design Method Based on Surrogate Modeling Applied to Diverging Duct Design

NASA Astrophysics Data System (ADS)

Hanan, Lu; Qiushi, Li; Shaobin, Li

2016-12-01

This paper presents an integrated optimization design method in which uniform design, response surface methodology and genetic algorithm are used in combination. In detail, uniform design is used to select the experimental sampling points in the experimental domain and the system performance is evaluated by means of computational fluid dynamics to construct a database. After that, response surface methodology is employed to generate a surrogate mathematical model relating the optimization objective and the design variables. Subsequently, genetic algorithm is adopted and applied to the surrogate model to acquire the optimal solution in the case of satisfying some constraints. The method has been applied to the optimization design of an axisymmetric diverging duct, dealing with three design variables including one qualitative variable and two quantitative variables. The method of modeling and optimization design performs well in improving the duct aerodynamic performance and can be also applied to wider fields of mechanical design and seen as a useful tool for engineering designers, by reducing the design time and computation consumption.

Research on the Diesel Engine with Sliding Mode Variable Structure Theory

NASA Astrophysics Data System (ADS)

Ma, Zhexuan; Mao, Xiaobing; Cai, Le

2018-05-01

This study constructed the nonlinear mathematical model of the diesel engine high-pressure common rail (HPCR) system through two polynomial fitting which was treated as a kind of affine nonlinear system. Based on sliding-mode variable structure control (SMVSC) theory, a sliding-mode controller for affine nonlinear systems was designed for achieving the control of common rail pressure and the diesel engine’s rotational speed. Finally, on the simulation platform of MATLAB, the designed nonlinear HPCR system was simulated. The simulation results demonstrated that sliding-mode variable structure control algorithm shows favourable control performances which are overcoming the shortcomings of traditional PID control in overshoot, parameter adjustment, system precision, adjustment time and ascending time.

Project management - Factors leading to success or failure

NASA Technical Reports Server (NTRS)

Kelley, A. J.; Murphy, D. C.

1974-01-01

This paper presents initial findings of a study designed to detail the relationships among situational, structural, and process variables as they relate to project effectiveness. In the paper, emphasis is placed on delineating those variables which tend to improve and those which tend to impede project effectiveness.

Systems Engineering-Based Tool for Identifying Critical Research Systems

ERIC Educational Resources Information Center

Abbott, Rodman P.; Stracener, Jerrell

2016-01-01

This study investigates the relationship between the designated research project system independent variables of Labor, Travel, Equipment, and Contract total annual costs and the dependent variables of both the associated matching research project total annual academic publication output and thesis/dissertation number output. The Mahalanobis…

Critical Thinking in Social Work Education: A Research Synthesis

ERIC Educational Resources Information Center

Samson, Patricia L.

2016-01-01

In a meta-analytic review of critical thinking in social work education, findings revealed variability in research designs, methods, and subsequent findings. The 10 studies reviewed assessed different components of critical thinking and highlighted different potential moderator variables. Although there are significant limitations to all the…

An analysis of crash likelihood : age versus driving experience

DOT National Transportation Integrated Search

1995-05-01

The study was designed to determine the crash likelihood of drivers in Michigan as a function of two independent variables: driver age and driving experience. The age variable had eight levels (18, 19, 20, 21, 22, 23, 24, and 25 years old) and the ex...

Perception toward Organizational Learning Culture in Small-Size Business Enterprises

ERIC Educational Resources Information Center

Graham, Carroll M.; Nafukho, Fredrick M.

2007-01-01

This study sought to determine the relationship between four independent variables educational level, longevity, gender, type of enterprise, and the dependent variable respondents' perception of culture toward organizational learning readiness. An exploratory correlational research design was employed to survey 498 employees in seven small…

Experimental design and response surface modelling for optimization of vat dye from water by nano zero valent iron (NZVI).

PubMed

Arabi, Simin; Sohrabi, Mahmoud Reza

2013-01-01

In this study, NZVI particles was prepared and studied for the removal of vat green 1 dye from aqueous solution. A four-factor central composite design (CCD) combined with response surface modeling (RSM) to evaluate the combined effects of variables as well as optimization was employed for maximizing the dye removal by prepared NZVI based on 30 different experimental data obtained in a batch study. Four independent variables, viz. NZVI dose (0.1-0.9 g/L), pH (1.5-9.5), contact time (20-100 s), and initial dye concentration (10-50 mg/L) were transform to coded values and quadratic model was built to predict the responses. The significant of independent variables and their interactions were tested by the analysis of variance (ANOVA). Adequacy of the model was tested by the correlation between experimental and predicted values of the response and enumeration of prediction errors. The ANOVA results indicated that the proposed model can be used to navigate the design space. Optimization of the variables for maximum adsorption of dye by NZVI particles was performed using quadratic model. The predicted maximum adsorption efficiency (96.97%) under the optimum conditions of the process variables (NZVI dose 0.5 g/L, pH 4, contact time 60 s, and initial dye concentration 30 mg/L) was very close to the experimental value (96.16%) determined in batch experiment. In the optimization, R2 and R2adj correlation coefficients for the model were evaluated as 0.95 and 0.90, respectively.

Design of a factorial experiment with randomization restrictions to assess medical device performance on vascular tissue.

PubMed

Diestelkamp, Wiebke S; Krane, Carissa M; Pinnell, Margaret F

2011-05-20

Energy-based surgical scalpels are designed to efficiently transect and seal blood vessels using thermal energy to promote protein denaturation and coagulation. Assessment and design improvement of ultrasonic scalpel performance relies on both in vivo and ex vivo testing. The objective of this work was to design and implement a robust, experimental test matrix with randomization restrictions and predictive statistical power, which allowed for identification of those experimental variables that may affect the quality of the seal obtained ex vivo. The design of the experiment included three factors: temperature (two levels); the type of solution used to perfuse the artery during transection (three types); and artery type (two types) resulting in a total of twelve possible treatment combinations. Burst pressures of porcine carotid and renal arteries sealed ex vivo were assigned as the response variable. The experimental test matrix was designed and carried out as a split-plot experiment in order to assess the contributions of several variables and their interactions while accounting for randomization restrictions present in the experimental setup. The statistical software package SAS was utilized and PROC MIXED was used to account for the randomization restrictions in the split-plot design. The combination of temperature, solution, and vessel type had a statistically significant impact on seal quality. The design and implementation of a split-plot experimental test-matrix provided a mechanism for addressing the existing technical randomization restrictions of ex vivo ultrasonic scalpel performance testing, while preserving the ability to examine the potential effects of independent factors or variables. This method for generating the experimental design and the statistical analyses of the resulting data are adaptable to a wide variety of experimental problems involving large-scale tissue-based studies of medical or experimental device efficacy and performance.

Data Analysis Strategies for Quasi-Experimental Studies Where Differential Group and Individual Growth Rates Are Assumed. Research Series No. 13.

ERIC Educational Resources Information Center

Olejnik, Stephen

The measurement of change in quasi-experimental educational research was discussed. Problems related to measuring change exist to varying degrees in all research designs; these issues are less troublesome in experimental studies because the investigator can manipulate the interest variables and observe their effects on other variables. Measuring…

The Effect of Varying Teacher Presentation Rates on Responding during Discrete Trial Training for Two Children with Autism

ERIC Educational Resources Information Center

Roxburgh, Carole A.; Carbone, Vincent J.

2013-01-01

Recent research has emphasized the importance of manipulating antecedent variables to reduce interfering behaviors when teaching persons with autism. Few studies have focused on the effects of the rate of teacher-presented instructional demands as an independent variable. In this study, an alternating treatment design was used to evaluate the…

An Investigation of the Effectiveness and Validity of Planning Time in Speaking Test Tasks

ERIC Educational Resources Information Center

Wigglesworth, Gillian; Elder, Cathie

2010-01-01

The study described in this article investigated the relationship between three variables in the IELTS oral module--planning, proficiency, and task--and was designed to enhance our understanding of how or whether these variables interact. The study aimed to determine whether differences in performance resulted from 1 or 2 min of planning time. It…

New gentle-wing high-shear granulator: impact of processing variables on granules and tablets characteristics of high-drug loading formulation using design of experiment approach.

PubMed

Fayed, Mohamed H; Abdel-Rahman, Sayed I; Alanazi, Fars K; Ahmed, Mahrous O; Tawfeek, Hesham M; Al-Shdefat, Ramadan I

2017-10-01

The aim of this work was to study the application of design of experiment (DoE) approach in defining design space for granulation and tableting processes using a novel gentle-wing high-shear granulator. According to quality-by-design (QbD) prospective, critical attributes of granules, and tablets should be ensured by manufacturing process design. A face-centered central composite design has been employed in order to investigate the effect of water amount (X 1 ), impeller speed (X 2 ), wet massing time (X 3 ), and water addition rate (X 4 ) as independent process variables on granules and tablets characteristics. Acetaminophen was used as a model drug and granulation experiments were carried out using dry addition of povidone k30. The dried granules have been analyzed for their size distribution, density, and flow pattern. Additionally, the produced tablets have been investigated for; weight uniformity, breaking force, friability and percent capping, disintegration time, and drug dissolution. Results of regression analysis showed that water amount, impeller speed and wet massing time have significant (p < .05) effect on granules and tablets characteristics. However, the water amount had the most pronounced effect as indicated by its higher parameter estimate. On the other hand, water addition rate showed a minimal impact on granules and tablets properties. In conclusion, water amount, impeller speed, and wet massing time could be considered as critical process variables. Thus, understanding the relationship between these variables and quality attributes of granules and corresponding tablets provides the basis for adjusting granulation variables in order to optimize product performance.

Aircraft Conceptual Design and Risk Analysis Using Physics-Based Noise Prediction

NASA Technical Reports Server (NTRS)

Olson, Erik D.; Mavris, Dimitri N.

2006-01-01

An approach was developed which allows for design studies of commercial aircraft using physics-based noise analysis methods while retaining the ability to perform the rapid trade-off and risk analysis studies needed at the conceptual design stage. A prototype integrated analysis process was created for computing the total aircraft EPNL at the Federal Aviation Regulations Part 36 certification measurement locations using physics-based methods for fan rotor-stator interaction tones and jet mixing noise. The methodology was then used in combination with design of experiments to create response surface equations (RSEs) for the engine and aircraft performance metrics, geometric constraints and take-off and landing noise levels. In addition, Monte Carlo analysis was used to assess the expected variability of the metrics under the influence of uncertainty, and to determine how the variability is affected by the choice of engine cycle. Finally, the RSEs were used to conduct a series of proof-of-concept conceptual-level design studies demonstrating the utility of the approach. The study found that a key advantage to using physics-based analysis during conceptual design lies in the ability to assess the benefits of new technologies as a function of the design to which they are applied. The greatest difficulty in implementing physics-based analysis proved to be the generation of design geometry at a sufficient level of detail for high-fidelity analysis.

Effect of study design on the reported effect of cardiac resynchronization therapy (CRT) on quantitative physiological measures: stratified meta-analysis in narrow-QRS heart failure and implications for planning future studies.

PubMed

Jabbour, Richard J; Shun-Shin, Matthew J; Finegold, Judith A; Afzal Sohaib, S M; Cook, Christopher; Nijjer, Sukhjinder S; Whinnett, Zachary I; Manisty, Charlotte H; Brugada, Josep; Francis, Darrel P

2015-01-06

Biventricular pacing (CRT) shows clear benefits in heart failure with wide QRS, but results in narrow QRS have appeared conflicting. We tested the hypothesis that study design might have influenced findings. We identified all reports of CRT-P/D therapy in subjects with narrow QRS reporting effects on continuous physiological variables. Twelve studies (2074 patients) met these criteria. Studies were stratified by presence of bias-resistance steps: the presence of a randomized control arm over a single arm, and blinded outcome measurement. Change in each endpoint was quantified using a standardized effect size (Cohen's d). We conducted separate meta-analyses for each variable in turn, stratified by trial quality. In non-randomized, non-blinded studies, the majority of variables (10 of 12, 83%) showed significant improvement, ranging from a standardized mean effect size of +1.57 (95%CI +0.43 to +2.7) for ejection fraction to +2.87 (+1.78 to +3.95) for NYHA class. In the randomized, non-blinded study, only 3 out of 6 variables (50%) showed improvement. For the randomized blinded studies, 0 out of 9 variables (0%) showed benefit, ranging from -0.04 (-0.31 to +0.22) for ejection fraction to -0.1 (-0.73 to +0.53) for 6-minute walk test. Differences in degrees of resistance to bias, rather than choice of endpoint, explain the variation between studies of CRT in narrow-QRS heart failure addressing physiological variables. When bias-resistance features are implemented, it becomes clear that these patients do not improve in any tested physiological variable. Guidance from studies without careful planning to resist bias may be far less useful than commonly perceived. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

Design and optimization of topical methotrexate loaded niosomes for enhanced management of psoriasis: application of Box-Behnken design, in-vitro evaluation and in-vivo skin deposition study.

PubMed

Abdelbary, Aly A; AbouGhaly, Mohamed H H

2015-05-15

Psoriasis, a skin disorder characterized by impaired epidermal differentiation, is regularly treated by systemic methotrexate (MTX), an effective cytotoxic drug but with numerous side effects. The aim of this work was to design topical MTX loaded niosomes for management of psoriasis to avoid systemic toxicity. To achieve this goal, MTX niosomes were prepared by thin film hydration technique. A Box-Behnken (BB) design, using Design-Expert(®) software, was employed to statistically optimize formulation variables. Three independent variables were evaluated: MTX concentration in hydration medium (X1), total weight of niosomal components (X2) and surfactant: cholesterol ratio (X3). The encapsulation efficiency percent (Y1: EE%) and particle size (Y2: PS) were selected as dependent variables. The optimal formulation (F12) displayed spherical morphology under transmission electron microscopy (TEM), optimum particle size of 1375.00 nm and high EE% of 78.66%. In-vivo skin deposition study showed that the highest value of percentage drug deposited (22.45%) and AUC0-10 (1.15 mg.h/cm(2)) of MTX from niosomes were significantly greater than that of drug solution (13.87% and 0.49 mg.h/cm(2), respectively). Moreover, in-vivo histopathological studies confirmed safety of topically applied niosomes. Concisely, the results showed that targeted MTX delivery might be achieved using topically applied niosomes for enhanced treatment of psoriasis. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of selected design variables on three ramp, external compression inlet performance. [boundary layer control bypasses, and mass flow rate

NASA Technical Reports Server (NTRS)

Kamman, J. H.; Hall, C. L.

1975-01-01

Two inlet performance tests and one inlet/airframe drag test were conducted in 1969 at the NASA-Ames Research Center. The basic inlet system was two-dimensional, three ramp (overhead), external compression, with variable capture area. The data from these tests were analyzed to show the effects of selected design variables on the performance of this type of inlet system. The inlet design variables investigated include inlet bleed, bypass, operating mass flow ratio, inlet geometry, and variable capture area.

Anthropometric data reduction using confirmatory factor analysis.

PubMed

Rohani, Jafri Mohd; Olusegun, Akanbi Gabriel; Rani, Mat Rebi Abdul

2014-01-01

The unavailability of anthropometric data especially in developing countries has remained a limiting factor towards the design of learning facilities with sufficient ergonomic consideration. Attempts to use anthropometric data from developed countries have led to provision of school facilities unfit for the users. The purpose of this paper is to use factor analysis to investigate the suitability of the collected anthropometric data as a database for school design in Nigerian tertiary institutions. Anthropometric data were collected from 288 male students in a Federal Polytechnic in North-West of Nigeria. Their age is between 18-25 years. Nine vertical anthropometric dimensions related to heights were collected using the conventional traditional equipment. Exploratory factor analysis was used to categorize the variables into a model consisting of two factors. Thereafter, confirmatory factor analysis was used to investigate the fit of the data to the proposed model. A just identified model, made of two factors, each with three variables was developed. The variables within the model accounted for 81% of the total variation of the entire data. The model was found to demonstrate adequate validity and reliability. Various measuring indices were used to verify that the model fits the data properly. The final model reveals that stature height and eye height sitting were the most stable variables for designs that have to do with standing and sitting construct. The study has shown the application of factor analysis in anthropometric data analysis. The study highlighted the relevance of these statistical tools to investigate variability among anthropometric data involving diverse population, which has not been widely used for analyzing previous anthropometric data. The collected data is therefore suitable for use while designing for Nigerian students.

Approximate techniques of structural reanalysis

NASA Technical Reports Server (NTRS)

Noor, A. K.; Lowder, H. E.

1974-01-01

A study is made of two approximate techniques for structural reanalysis. These include Taylor series expansions for response variables in terms of design variables and the reduced-basis method. In addition, modifications to these techniques are proposed to overcome some of their major drawbacks. The modifications include a rational approach to the selection of the reduced-basis vectors and the use of Taylor series approximation in an iterative process. For the reduced basis a normalized set of vectors is chosen which consists of the original analyzed design and the first-order sensitivity analysis vectors. The use of the Taylor series approximation as a first (initial) estimate in an iterative process, can lead to significant improvements in accuracy, even with one iteration cycle. Therefore, the range of applicability of the reanalysis technique can be extended. Numerical examples are presented which demonstrate the gain in accuracy obtained by using the proposed modification techniques, for a wide range of variations in the design variables.

Statistical optimization of lovastatin production by Omphalotus olearius (DC.) singer in submerged fermentation.

PubMed

Atlı, Burcu; Yamaç, Mustafa; Yıldız, Zeki; Isikhuemhen, Omoanghe S

2016-01-01

In this study, culture conditions were optimized to improve lovastatin production by Omphalotus olearius, isolate OBCC 2002, using statistical experimental designs. The Plackett-Burman design was used to select important variables affecting lovastatin production. Accordingly, glucose, peptone, and agitation speed were determined as the variables that have influence on lovastatin production. In a further experiment, these variables were optimized with a Box-Behnken design and applied in a submerged process; this resulted in 12.51 mg/L lovastatin production on a medium containing glucose (10 g/L), peptone (5 g/L), thiamine (1 mg/L), and NaCl (0.4 g/L) under static conditions. This level of lovastatin production is eight times higher than that produced under unoptimized media and growth conditions by Omphalotus olearius. To the best of our knowledge, this is the first attempt to optimize submerged fermentation process for lovastatin production by Omphalotus olearius.

Design Details for the Aquantis 2.5 MW Ocean Current Generation Device

DOE Data Explorer

Banko, Rich; Coakley, David; Colegrove, Dana; Fleming, Alex; Zierke, William; Ebner, Stephen

2015-06-03

Items in this submission provide the detailed design of the Aquantis Ocean Current Turbine and accompanying analysis documents, including preliminary designs, verification of design reports, CAD drawings of the hydrostatic drivetrain, a test plan and an operating conditions simulation report. This dataset also contains analysis trade off studies of fixed vs. variable pitch and 2 vs. 3 blades.

Towards automating the discovery of certain innovative design principles through a clustering-based optimization technique

NASA Astrophysics Data System (ADS)

Bandaru, Sunith; Deb, Kalyanmoy

2011-09-01

In this article, a methodology is proposed for automatically extracting innovative design principles which make a system or process (subject to conflicting objectives) optimal using its Pareto-optimal dataset. Such 'higher knowledge' would not only help designers to execute the system better, but also enable them to predict how changes in one variable would affect other variables if the system has to retain its optimal behaviour. This in turn would help solve other similar systems with different parameter settings easily without the need to perform a fresh optimization task. The proposed methodology uses a clustering-based optimization technique and is capable of discovering hidden functional relationships between the variables, objective and constraint functions and any other function that the designer wishes to include as a 'basis function'. A number of engineering design problems are considered for which the mathematical structure of these explicit relationships exists and has been revealed by a previous study. A comparison with the multivariate adaptive regression splines (MARS) approach reveals the practicality of the proposed approach due to its ability to find meaningful design principles. The success of this procedure for automated innovization is highly encouraging and indicates its suitability for further development in tackling more complex design scenarios.

21st Century HVAC System for Future Naval Surface Combatants - Concept Development Report

DTIC Science & Technology

2007-09-01

application of permanent magnet motors to ventilation fans3. The study emphasized reducing the motor size, incorporating variable speed operation to reduce...Incorporation of permanent magnet motors and variable speed is also feasible. Permanent magnet motor technology is ideally suited for variable...family incorporates high speed permanent magnet motors and further fan blade design improvements. The fan diameters will be reduced, substantially, at the

Reporting of methodological features in observational studies of pre-harvest food safety.

PubMed

Sargeant, Jan M; O'Connor, Annette M; Renter, David G; Kelton, David F; Snedeker, Kate; Wisener, Lee V; Leonard, Erin K; Guthrie, Alessia D; Faires, Meredith

2011-02-01

Observational studies in pre-harvest food safety may be useful for identifying risk factors and for evaluating potential mitigation strategies to reduce foodborne pathogens. However, there are no structured reporting guidelines for these types of study designs in livestock species. Our objective was to evaluate the reporting of observational studies in the pre-harvest food safety literature using guidelines modified from the human healthcare literature. We identified 100 pre-harvest food safety studies published between 1999 and 2009. Each study was evaluated independently by two reviewers using a structured checklist. Of the 38 studies that explicitly stated the observational study design, 27 were described as cross-sectional studies, eight as case-control studies, and three as cohort studies. Study features reported in over 75% of the selected studies included: description of the geographic location of the studies, definitions and sources of data for outcomes, organizational level and source of data for independent variables, description of statistical methods and results, number of herds enrolled in the study and included in the analysis, and sources of study funding. However, other features were not consistently reported, including details related to eligibility criteria for groups (such as barn, room, or pen) and individuals, numbers of groups and individuals included in various stages of the study, identification of primary outcomes, the distinction between putative risk factors and confounding variables, the identification of a primary exposure variable, the referent level for evaluation of categorical variable associations, methods of controlling confounding variables and missing variables, model fit, details of subset analysis, demographic information at the sampling unit level, and generalizability of the study results. Improvement in reporting of observational studies of pre-harvest food safety will aid research readers and reviewers in interpreting and evaluating the results of such studies. Copyright © 2010 Elsevier B.V. All rights reserved.

A Mixed-Methodological Examination of Investment Model Variables among Abused and Nonabused College Women

ERIC Educational Resources Information Center

Dardis, Christina M.; Kelley, Erika L.; Edwards, Katie M.; Gidycz, Christine A.

2013-01-01

Objective: This study assessed abused and nonabused women's perceptions of Investment Model (IM) variables (ie, relationship investment, satisfaction, commitment, quality of alternatives) utilizing a mixed-methods design. Participants: Participants included 102 college women, approximately half of whom were in abusive dating relationships.…

How Knowledge Management Is Affected by Organizational Structure

ERIC Educational Resources Information Center

Mahmoudsalehi, Mehdi; Moradkhannejad, Roya; Safari, Khalil

2012-01-01

Purpose: Identifying the impact of organizational structure on knowledge management (KM) is the aim of this study, as well as recognizing the importance of each variable indicator in creating, sharing and utility of knowledge. Design/methodology/approach: For understanding relationships between the main variables (organizational structure-KM), the…

Respondent Techniques for Reduction of Emotions Limiting School Adjustment: A Quantitative Review and Methodological Critique.

ERIC Educational Resources Information Center

Misra, Anjali; Schloss, Patrick J.

1989-01-01

The critical analysis of 23 studies using respondent techniques for the reduction of excessive emotional reactions in school children focuses on research design, dependent variables, independent variables, component analysis, and demonstrations of generalization and maintenance. Results indicate widespread methodological flaws that limit the…

The Relationship of School Design to Academic Achievement of Elementary School Children.

ERIC Educational Resources Information Center

Yarbrough, Kathleen Ann

This study sought to determine if there are relationships between student achievement and educational facilities. It focused on the question: Does school design influence the academic achievement of elementary school students? Criteria used were scores on the Iowa Test of Basic Skills and 86 variables describing design patterns in various…

STME Hydrogen Mixer Study

NASA Technical Reports Server (NTRS)

Blumenthal, Rob; Kim, Dongmoon; Bache, George

1992-01-01

The hydrogen mixer for the Space Transportation Main Engine is used to mix cold hydrogen bypass flow with warm hydrogen coolant chamber gas, which is then fed to the injectors. It is very important to have a uniform fuel temperature at the injectors in order to minimize mixture ratio problems due to the fuel density variations. In addition, the fuel at the injector has certain total pressure requirements. In order to achieve these objectives, the hydrogen mixer must provide a thoroughly mixed fluid with a minimum pressure loss. The AEROVISC computational fluid dynamics (CFD) code was used to analyze the STME hydrogen mixer, and proved to be an effective tool in optimizing the mixer design. AEROVISC, which solves the Reynolds Stress-Averaged Navier-Stokes equations in primitive variable form, was used to assess the effectiveness of different mixer designs. Through a parametric study of mixer design variables, an optimal design was selected which minimized mixed fuel temperature variation and fuel mixer pressure loss. The use of CFD in the design process of the STME hydrogen mixer was effective in achieving an optimal mixer design while reducing the amount of hardware testing.

Physical activity monitoring by use of accelerometer-based body-worn sensors in older adults: a systematic literature review of current knowledge and applications.

PubMed

Taraldsen, Kristin; Chastin, Sebastien F M; Riphagen, Ingrid I; Vereijken, Beatrix; Helbostad, Jorunn L

2012-01-01

To systematically review the literature on physical activity variables derived from body-worn sensors during long term monitoring in healthy and in-care older adults. Using pre-designed inclusion and exclusion criteria, a PubMed search strategy was designed to trace relevant reports of studies. Last search date was March 8, 2011. Studies that included persons with mean or median age of >65 years, used accelerometer-based body-worn sensors with a monitoring length of >24h, and reported values on physical activity in the samples assessed. 1403 abstracts were revealed and 134 full-text papers included in the final review. A variety of variables derived from activity counts or recognition of performed activities were reported in healthy older adults as well as in in-care older adults. Three variables were possible to compare across studies, level of Energy Expenditure in kcal per day and activity recognition in terms of total time in walking and total activity. However, physical activity measured by these variables demonstrated large variation between studies and did not distinguish activity between healthy and in-care samples. There is a rich variety in methods used for data collection and analysis as well as in reported variables. Different aspects of physical activity can be described, but the variety makes it challenging to compare across studies. There is an urgent need for developing consensus on activity monitoring protocols and which variables to report. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Nano-transfersomes as a novel carrier for transdermal delivery.

PubMed

Chaudhary, Hema; Kohli, Kanchan; Kumar, Vikash

2013-09-15

The aim of this study was to design and optimize a nano-transfersomes of Diclofenac diethylamine (DDEA) and Curcumin (CRM). A 3(3) factorial design (Box-Behnken) was used to derive a polynomial equation (second order) to construct 2-D (contour) and 3-D (Response Surface) plots for prediction of responses. The ratio of lipid to surfactant (X1), weight of lipid to surfactant (X2) and sonication time (X3) (independent variables) and dependent variables [entrapment efficiency of DDEA (Y1), entrapment efficiency of CRM (Y2), effect on particle size (Y3), flux of DDEA (Y4), and flux of CRM (Y5)] were studied. The 2-D and 3-D plots were drawn and a statistical validity of the polynomials was established to find the compositions of optimized formulation. The design established the role of the derived polynomial equation, 2-D and 3-D plots in predicting the values of dependent variables for the preparation and optimization of nano-transfersomes for transdermal drug release. Copyright © 2013 Elsevier B.V. All rights reserved.

Congruency of scapula locking plates: implications for implant design.

PubMed

Park, Andrew Y; DiStefano, James G; Nguyen, Thuc-Quyen; Buckley, Jenni M; Montgomery, William H; Grimsrud, Chris D

2012-04-01

We conducted a study to evaluate the congruency of fit of current scapular plate designs. Three-dimensional image-processing and -analysis software, and computed tomography scans of 12 cadaveric scapulae were used to generate 3 measurements: mean distance from plate to bone, maximum distance, and percentage of plate surface within 2 mm of bone. These measurements were used to quantify congruency. The scapular spine plate had the most congruent fit in all 3 measured variables. The lateral border and glenoid plates performed statistically as well as the scapular spine plate in at least 1 of the measured variables. The medial border plate had the least optimal measurements in all 3 variables. With locking-plate technology used in a wide variety of anatomical locations, the locking scapula plate system can allow for a fixed-angle construct in this region. Our study results showed that the scapular spine, glenoid, and lateral border plates are adequate in terms of congruency. However, design improvements may be necessary for the medial border plate. In addition, we describe a novel method for quantifying hardware congruency, a method that can be applied to any anatomical location.

Enhanced production of lovastatin by Omphalotus olearius (DC.) Singer in solid state fermentation.

PubMed

Atlı, Burcu; Yamaç, Mustafa; Yıldız, Zeki; Isikhuemnen, Omoanghe S

2015-01-01

Although lovastatin production has been reported for different microorganism species, there is limited information about lovastatin production by basidiomycetes. The optimization of culture parameters that enhances lovastatin production by Omphalotus olearius OBCC 2002 was investigated, using statistically based experimental designs under solid state fermentation. The Plackett Burman design was used in the first step to test the relative importance of the variables affecting production of lovastatin. Amount and particle size of barley were identified as efficient variables. In the latter step, the interactive effects of selected efficient variables were studied with a full factorial design. A maximum lovastatin yield of 139.47mg/g substrate was achieved by the fermentation of 5g of barley, 1-2mm particle diam., at 28°C. This study showed that O. olearius OBCC 2002 has a high capacity for lovastatin production which could be enhanced by using solid state fermentation with novel and cost-effective substrates, such as barley. Copyright © 2013 Revista Iberoamericana de Micología. Published by Elsevier Espana. All rights reserved.

Organizational Socialization and Its Relation with Organizational Performance in High Schools

ERIC Educational Resources Information Center

Balci, Ali; Ozturk, Inci; Polatcan, Mahmut; Saylik, Ahmet; Bil, Erkut

2016-01-01

This study is designed to explore organizational socialization and organizational performance levels of secondary school teachers and the relation between the two variables mentioned. The study is designed as correlational research. The target population of the research consists of 5744 teachers who work in public and private Anatolian high…

75 FR 80821 - Agency Information Collection Activities; Submission for Office of Management and Budget Review...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-23

... statement to read: Three comments were received that expressed support for the research and recommended... design. Specifically, we agree that the study design should include the variables of age, education... another study (FDA-2009-N-0263 (January 5, 2010), ``Presentation of Quantitative Effectiveness and Risk...

Using experimental design and spatial analyses to improve the precision of NDVI estimates in upland cotton field trials

USDA-ARS?s Scientific Manuscript database

Controlling for spatial variability is important in high-throughput phenotyping studies that enable large numbers of genotypes to be evaluated across time and space. In the current study, we compared the efficacy of different experimental designs and spatial models in the analysis of canopy spectral...

Factorial study of rain garden design for nitrogen removal

EPA Science Inventory

Abstract Nitrate (〖NO〗_3^--N ) removal studies in bioretention systems showed great variability in removal rates and in some cases 〖NO〗_3^--N was exported. A 3-way factorial design (2 x 2 x 4) was devised for eight outdoor un-vegetated rain gardens to evaluate the effects of ...

An Examination of Self-Directed Learning Readiness in Executive-Level Fire Officers

ERIC Educational Resources Information Center

Knight, Steven G.

2012-01-01

The purpose of this study was to examine the self-directed learning readiness in executive fire officers in relation to the independent variables of personality type, educational attainment, and professional designation. This research utilized a quantitative design. This study utilized the Myers-Briggs Type Indicator (MBTI) and the Self-Directed…

Entrepreneurial Intentions of University Students: A Study of Design Undergraduates in Spain

ERIC Educational Resources Information Center

Ubierna, Francisco; Arranz, Nieves; Fdez de Arroyabe, J. C.

2014-01-01

This paper presents an analysis of the entrepreneurial intentions of university undergraduate students, with particular regard to those studying design. Attitudinal, social and capabilities variables are analysed in order to determine the profile of an entrepreneur. Using a sample of 521 undergraduate students, the findings show that design…

Size and consistency of problem-solving consultation outcomes: an empirical analysis.

PubMed

Hurwitz, Jason T; Kratochwill, Thomas R; Serlin, Ronald C

2015-04-01

In this study, we analyzed extant data to evaluate the variability and magnitude of students' behavior change outcomes (academic, social, and behavioral) produced by consultants through problem-solving consultation with teachers. Research questions were twofold: (a) Do consultants produce consistent and sizeable positive student outcomes across their cases as measured through direct and frequent assessment? and (b) What proportion of variability in student outcomes is attributable to consultants? Analyses of extant data collected from problem-solving consultation outcome studies that used single-case, time-series AB designs with multiple participants were analyzed. Four such studies ultimately met the inclusion criteria for the extant data, comprising 124 consultants who worked with 302 school teachers regarding 453 individual students. Consultants constituted the independent variable, while the primary dependent variable was a descriptive effect size based on student behavior change as measured by (a) curriculum-based measures, (b) permanent products, or (c) direct observations. Primary analyses involved visual and statistical evaluation of effect size magnitude and variability observed within and between consultants and studies. Given the nested nature of the data, multilevel analyses were used to assess consultant effects on student outcomes. Results suggest that consultants consistently produced positive effect sizes on average across their cases, but outcomes varied between consultants. Findings also indicated that consultants, teachers, and the corresponding studies accounted for a significant proportion of variability in student outcomes. This investigation advances the use of multilevel and integrative data analyses to evaluate consultation outcomes and extends research on problem-solving consultation, consultant effects, and meta-analysis of case study AB designs. Practical implications for evaluating consultation service delivery in school settings are also discussed. Copyright © 2015 Society for the Study of School Psychology. Published by Elsevier Ltd. All rights reserved.

Behavior sensitivities for control augmented structures

NASA Technical Reports Server (NTRS)

Manning, R. A.; Lust, R. V.; Schmit, L. A.

1987-01-01

During the past few years it has been recognized that combining passive structural design methods with active control techniques offers the prospect of being able to find substantially improved designs. These developments have stimulated interest in augmenting structural synthesis by adding active control system design variables to those usually considered in structural optimization. An essential step in extending the approximation concepts approach to control augmented structural synthesis is the development of a behavior sensitivity analysis capability for determining rates of change of dynamic response quantities with respect to changes in structural and control system design variables. Behavior sensitivity information is also useful for man-machine interactive design as well as in the context of system identification studies. Behavior sensitivity formulations for both steady state and transient response are presented and the quality of the resulting derivative information is evaluated.

Development of a non-piston MR suspension rod for variable mass systems

NASA Astrophysics Data System (ADS)

Deng, Huaxia; Han, Guanghui; Zhang, Jin; Wang, Mingxian; Ma, Mengchao; Zhong, Xiang; Yu, Liandong

2018-06-01

The semi-active suspension systems for variable mass systems require long work stroke and variable damping, while the currently piston structure limits the work stroke for the magnetorheological (MR) dampers. The main work of this paper is to design a semi-active non-piston MR (NPMR) suspension rod for the reduction of the vibration of an automatic impeller washing machine, which is a typical variable mass system. The designed suspension rod locates in the suspension system that links the internal tub to the washing machine cabinet. The NPMR suspension rod includes a MR part and a air part. The MR part can provide low initial damping force and the unlimited work stroke compared with the piston MR damper. The hysteretic response tests and vibration performance evaluation with different loadings are conducted to verify the dynamic performance for the designed rod. The measured damping force of the MR part varies from 5 to 20 N. Studies of dehydration mode experiments of the washing machine indicate that its vibration acceleration with the NPMR suspension rods can reduce to half of the original passive ones in certain conditions.

Design of quantum efficiency measurement system for variable doping GaAs photocathode

NASA Astrophysics Data System (ADS)

Chen, Liang; Yang, Kai; Liu, HongLin; Chang, Benkang

2008-03-01

To achieve high quantum efficiency and good stability has been a main direction to develop GaAs photocathode recently. Through early research, we proved that variable doping structure is executable and practical, and has great potential. In order to optimize variable doping GaAs photocathode preparation techniques and study the variable doping theory deeply, a real-time quantum efficiency measurement system for GaAs Photocathode has been designed. The system uses FPGA (Field-programmable gate array) device, and high speed A/D converter to design a high signal noise ratio and high speed data acquisition card. ARM (Advanced RISC Machines) core processor s3c2410 and real-time embedded system are used to obtain and show measurement results. The measurement precision of photocurrent could reach 1nA, and measurement range of spectral response curve is within 400~1000nm. GaAs photocathode preparation process can be real-time monitored by using this system. This system could easily be added other functions to show the physic variation of photocathode during the preparation process more roundly in the future.

The Influence of PV Module Materials and Design on Solder Joint Thermal Fatigue Durability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bosco, Nick; Silverman, Timothy J.; Kurtz, Sarah

Finite element model (FEM) simulations have been performed to elucidate the effect of flat plate photovoltaic (PV) module materials and design on PbSn eutectic solder joint thermal fatigue durability. The statistical method of Latin Hypercube sampling was employed to investigate the sensitivity of simulated damage to each input variable. Variables of laminate material properties and their thicknesses were investigated. Using analysis of variance, we determined that the rate of solder fatigue was most sensitive to solder layer thickness, with copper ribbon and silicon thickness being the next two most sensitive variables. By simulating both accelerated thermal cycles (ATCs) and PVmore » cell temperature histories through two characteristic days of service, we determined that the acceleration factor between the ATC and outdoor service was independent of the variables sampled in this study. This result implies that an ATC test will represent a similar time of outdoor exposure for a wide range of module designs. This is an encouraging result for the standard ATC that must be universally applied across all modules.« less

Conceptual design optimization study

NASA Technical Reports Server (NTRS)

Hollowell, S. J.; Beeman, E. R., II; Hiyama, R. M.

1990-01-01

The feasibility of applying multilevel functional decomposition and optimization techniques to conceptual design of advanced fighter aircraft was investigated. Applying the functional decomposition techniques to the conceptual design phase appears to be feasible. The initial implementation of the modified design process will optimize wing design variables. A hybrid approach, combining functional decomposition techniques for generation of aerodynamic and mass properties linear sensitivity derivatives with existing techniques for sizing mission performance and optimization, is proposed.

VSCE technology definition study

NASA Technical Reports Server (NTRS)

Howlett, R. A.; Hunt, R. B.

1979-01-01

Refined design definition of the variable stream control engine (VSCE) concept for advanced supersonic transports is presented. Operating and performance features of the VSCE are discussed, including the engine components, thrust specific fuel consumption, weight, noise, and emission system. A preliminary engine design is presented.

Optimization and formulation design of gels of Diclofenac and Curcumin for transdermal drug delivery by Box-Behnken statistical design.

PubMed

Chaudhary, Hema; Kohli, Kanchan; Amin, Saima; Rathee, Permender; Kumar, Vikash

2011-02-01

The aim of this study was to develop and optimize a transdermal gel formulation for Diclofenac diethylamine (DDEA) and Curcumin (CRM). A 3-factor, 3-level Box-Behnken design was used to derive a second-order polynomial equation to construct contour plots for prediction of responses. Independent variables studied were the polymer concentration (X(1)), ethanol (X(2)) and propylene glycol (X(3)) and the levels of each factor were low, medium, and high. The dependent variables studied were the skin permeation rate of DDEA (Y(1)), skin permeation rate of CRM (Y(2)), and viscosity of the gels (Y(3)). Response surface plots were drawn, statistical validity of the polynomials was established to find the compositions of optimized formulation which was evaluated using the Franz-type diffusion cell. The permeation rate of DDEA increased proportionally with ethanol concentration but decreased with polymer concentration, whereas the permeation rate of CRM increased proportionally with polymer concentration. Gels showed a non-Fickian super case II (typical zero order) and non-Fickian diffusion release mechanism for DDEA and CRM, respectively. The design demonstrated the role of the derived polynomial equation and contour plots in predicting the values of dependent variables for the preparation and optimization of gel formulation for transdermal drug release. Copyright © 2010 Wiley-Liss, Inc.

Design and control of a variable geometry turbofan with an independently modulated third stream

NASA Astrophysics Data System (ADS)

Simmons, Ronald J.

Emerging 21st century military missions task engines to deliver the fuel efficiency of a high bypass turbofan while retaining the ability to produce the high specific thrust of a low bypass turbofan. This study explores the possibility of satisfying such competing demands by adding a second independently modulated bypass stream to the basic turbofan architecture. This third stream can be used for a variety of purposes including: providing a cool heat sink for dissipating aircraft heat loads, cooling turbine cooling air, and providing a readily available stream of constant pressure ratio air for lift augmentation. Furthermore, by modulating airflow to the second and third streams, it is possible to continuously match the engine's airflow demand to the inlet's airflow supply thereby reducing spillage and increasing propulsive efficiency. This research begins with a historical perspective of variable cycle engines and shows a logical progression to proposed architectures. Then a novel method for investigating optimal performance is presented which determines most favorable on design variable geometry settings, most beneficial moment to terminate flow holding, and an optimal scheduling of variable features for fuel efficient off design operation. Mission analysis conducted across the three candidate missions verifies that these three stream variable cycles can deliver fuel savings in excess of 30% relative to a year 2000 reference turbofan. This research concludes by evaluating the relative impact of each variable technology on the performance of adaptive engine architectures. The most promising technologies include modulated turbine cooling air, variable high pressure turbine inlet area and variable third stream nozzle throat area. With just these few features it is possible to obtain nearly optimal performance, including 90% or more of the potential fuel savings, with far fewer variable features than are available in the study engine. It is abundantly clear that three stream variable architectures can significantly outperform existing two stream turbofans in both fuel efficiency and at the vehicle system level with only a modest increase in complexity and weight. Such engine architectures should be strongly considered for future military applications.

The Relation between Task Demands and Student Behavior Problems during Reading Instruction: A Case Study

ERIC Educational Resources Information Center

Jones, Melanie M.; Lignugaris/Kraft, Benjamin; Peterson, Stephanie M.

2007-01-01

Demand is placed on students in a variety of ways and, in some cases, affects whether or not a student engages in problem behavior. The authors' purpose in this study was to investigate the variables that influence demand and examine how changes in those variables affected a child's behavior. The authors used parametric design in which the…

Comparing Between- and Within-Group Variances in a Two-Level Study: A Latent Variable Modeling Approach to Evaluating Their Relationship

ERIC Educational Resources Information Center

Raykov, Tenko; Marcoulides, George A.; Akaeze, Hope O.

2017-01-01

This note is concerned with examining the relationship between within-group and between-group variances in two-level nested designs. A latent variable modeling approach is outlined that permits point and interval estimation of their ratio and allows their comparison in a multilevel study. The procedure can also be used to test various hypotheses…

The Effects of Two Variables on the Problem Solving Abilities of First Grade and Second Grade Children.

ERIC Educational Resources Information Center

Kellerhouse, Kenneth Douglas, Jr.

This study was designed to replicate and extend the work of Steffe on the effect of using different set names as variables in addition problem statements. The behavior of both first- and second-grade students was studied and the usefulness of visual aids in solving addition problems was also investigated. One-hundred twenty first- and second-grade…

Design definition study of a lift/cruise fan technology V/STOL airplane: Summary

NASA Technical Reports Server (NTRS)

Zabinsky, J. M.; Higgins, H. C.

1975-01-01

A two-engine three-fan V/STOL airplane was designed to fulfill naval operational requirements. A multimission airplane was developed from study of specific point designs. Based on the multimission concept, airplanes were designed to demonstrate and develop the technology and operational procedures for this class of aircraft. Use of interconnected variable pitch fans led to a good balance between high thrust with responsive control and efficient thrust at cruise speeds. The airplanes and their characteristics are presented.

Seismic Response Control Of Structures Using Semi-Active and Passive Variable Stiffness Devices

NASA Astrophysics Data System (ADS)

Salem, Mohamed M. A.

Controllable devices such as Magneto-Rheological Fluid Dampers, Electro-Rheological Dampers, and controllable friction devices have been studied extensively with limited implementation in real structures. Such devices have shown great potential in reducing seismic demands, either as smart base isolation systems, or as smart devices for multistory structures. Although variable stiffness devices can be used for seismic control of structures, the vast majority of research effort has been given to the control of damping. The primary focus of this dissertation is to evaluate the seismic control of structures using semi-active and passive variable stiffness characteristics. Smart base isolation systems employing variable stiffness devices have been studied, and two semi-active control strategies are proposed. The control algorithms were designed to reduce the superstructure and base accelerations of seismically isolated structures subject to near-fault and far-field ground motions. Computational simulations of the proposed control algorithms on the benchmark structure have shown that excessive base displacements associated with the near-fault ground motions may be better mitigated with the use of variable stiffness devices. However, the device properties must be controllable to produce a wide range of stiffness changes for an effective control of the base displacements. The potential of controllable stiffness devices in limiting the base displacement due to near-fault excitation without compromising the performance of conventionally isolated structures, is illustrated. The application of passive variable stiffness devices for seismic response mitigation of multistory structures is also investigated. A stiffening bracing system (SBS) is proposed to replace the conventional bracing systems of braced frames. An optimization process for the SBS parameters has been developed. The main objective of the design process is to maintain a uniform inter-story drift angle over the building's height, which in turn would evenly distribute the seismic demand over the building. This behavior is particularly essential so that any possible damage is not concentrated in a single story. Furthermore, the proposed design ensures that additional damping devices distributed over the building's height work efficiently with their maximum design capacity, leading to a cost efficient design. An integrated and comprehensive design procedure that can be readily adopted by the current seismic design codes is proposed. An equivalent lateral force distribution is developed that shows a good agreement with the response history analyses in terms of seismic performance and demand prediction. This lateral force pattern explicitly accounts for the higher mode effect, the dynamic characteristics of the structure, the supplemental damping, and the site specific seismic hazard. Therefore, the proposed design procedure is considered as a standalone method for the design of SBS equipped buildings.

Reducing random measurement error in assessing postural load on the back in epidemiologic surveys.

PubMed

Burdorf, A

1995-02-01

The goal of this study was to design strategies to assess postural load on the back in occupational epidemiology by taking into account the reliability of measurement methods and the variability of exposure among the workers under study. Intermethod reliability studies were evaluated to estimate the systematic bias (accuracy) and random measurement error (precision) of various methods to assess postural load on the back. Intramethod reliability studies were reviewed to estimate random variability of back load over time. Intermethod surveys have shown that questionnaires have a moderate reliability for gross activities such as sitting, whereas duration of trunk flexion and rotation should be assessed by observation methods or inclinometers. Intramethod surveys indicate that exposure variability can markedly affect the reliability of estimates of back load if the estimates are based upon a single measurement over a certain time period. Equations have been presented to evaluate various study designs according to the reliability of the measurement method, the optimum allocation of the number of repeated measurements per subject, and the number of subjects in the study. Prior to a large epidemiologic study, an exposure-oriented survey should be conducted to evaluate the performance of measurement instruments and to estimate sources of variability for back load. The strategy for assessing back load can be optimized by balancing the number of workers under study and the number of repeated measurements per worker.

Determination of oleamide and erucamide in polyethylene films by pressurised fluid extraction and gas chromatography.

PubMed

Garrido-López, Alvaro; Esquiu, Vanesa; Tena, María Teresa

2006-08-18

A pressurized fluid extraction (PFE) and gas chromatography-flame ionization detection (GC-FID) method is proposed to determine the slip agents in polyethylene (PE) films. The study of PFE variables was performed using a fractional factorial design (FFD) for screening and a central composite design (CCD) for optimizing the main variables obtained from the Pareto charts. The variables that were studied include temperature, static time, percentage of cyclohexane and the number of extraction cycles. The final condition selected was pure isopropanol (two times) at 105 degrees C for 16min. The recovery of spiked oleamide and erucamide was around 100%. The repeatability of the method was between 9.6% for oleamide and 8% for erucamide, expressed as relative standard deviation. Finally, the method was applied to determine oleamide and erucamide in several polyethylene films and the results were statistically equal to those obtained by pyrolysis and gas-phase chemiluminescence (CL).

Development of a working Hovercraft model

NASA Astrophysics Data System (ADS)

Noor, S. H. Mohamed; Syam, K.; Jaafar, A. A.; Mohamad Sharif, M. F.; Ghazali, M. R.; Ibrahim, W. I.; Atan, M. F.

2016-02-01

This paper presents the development process to fabricate a working hovercraft model. The purpose of this study is to design and investigate of a fully functional hovercraft, based on the studies that had been done. The different designs of hovercraft model had been made and tested but only one of the models is presented in this paper. In this thesis, the weight, the thrust, the lift and the drag force of the model had been measured and the electrical and mechanical parts are also presented. The processing unit of this model is Arduino Uno by using the PSP2 (Playstation 2) as the controller. Since our prototype should be functioning on all kind of earth surface, our model also had been tested in different floor condition. They include water, grass, cement and tile. The Speed of the model is measured in every case as the respond variable, Current (I) as the manipulated variable and Voltage (V) as the constant variable.

Introduction to the use of regression models in epidemiology.

PubMed

Bender, Ralf

2009-01-01

Regression modeling is one of the most important statistical techniques used in analytical epidemiology. By means of regression models the effect of one or several explanatory variables (e.g., exposures, subject characteristics, risk factors) on a response variable such as mortality or cancer can be investigated. From multiple regression models, adjusted effect estimates can be obtained that take the effect of potential confounders into account. Regression methods can be applied in all epidemiologic study designs so that they represent a universal tool for data analysis in epidemiology. Different kinds of regression models have been developed in dependence on the measurement scale of the response variable and the study design. The most important methods are linear regression for continuous outcomes, logistic regression for binary outcomes, Cox regression for time-to-event data, and Poisson regression for frequencies and rates. This chapter provides a nontechnical introduction to these regression models with illustrating examples from cancer research.

Impact of detergent systems on bacterial survival on laundered fabrics.

PubMed Central

Jaska, J M; Fredell, D L

1980-01-01

The survival of Staphylococcus aureus was determined from inoculated swatches laundered in either a phosphate or a phosphate-substitute detergent. In a Plackett-Burman design study, the independent variables of detergent type, concentration, and variation, wash water temperature, soil load, cycle time, and water hardness were assigned high and low values. Wash water temperatures of 27, 38, 49, and 60 degrees C were employed. Viable bacteria were recovered from macerated swatches. Statistical analysis disclosed that there was no practical difference in the ability of phosphate or phosphate-substitute detergents to reduce the level of S. aureus on the laundered swatches in this controlled design. Analysis did reveal that water temperature was the most significant independent variables. The remaining variables did not appear to have any practical significance upon bacterial reduction. This bacteriological study did not evaluate other essential detergent properties. PMID:7377775

[Meta analysis of variables related to attention deficit hyperactivity disorder in school-age children].

PubMed

Park, Wan Ju; Seo, Ji Yeong; Kim, Mi Ye

2011-04-01

The purpose of this study was to use meta-analysis to examine recent domestic articles related to attention deficit hyperactivity disorder (ADHD) in school-age children. After reviewing 213 articles published between 1990 and 2009 from and cited in RISS, KISS, and DBpia, the researchers identified 24 studies with 440 research variables that had appropriate data for methodological study. SPSS 17.0 program was used. The outcome variables were divided into five types: Inattention, hyperactive impulsive, intrinsic, extrinsic, and academic ability variables. Effects size of overall core symptoms was 0.47 which is moderate level in terms of Cohen criteria and effects size of overall negative variables related ADHD was 0.27 which is small level. The most dominant variable related to ADHD was obtained from hyperactive-impulsive (0.70). Also academic ability (0.45), inattention (0.37), and intrinsic variables (0.29) had a small effect whereas extrinsic variables (0.13) had little effect on descriptive ADHD study. The results reveal that ADHD core symptoms have moderate effect size and peripheral negative variables related ADHD have small effect size. To improve the reliability of the meta-analysis results by minimizing publication bias, more intervention studies using appropriate study designs should be done.

Optimization of large animal MI models; a systematic analysis of control groups from preclinical studies.

PubMed

Zwetsloot, P P; Kouwenberg, L H J A; Sena, E S; Eding, J E; den Ruijter, H M; Sluijter, J P G; Pasterkamp, G; Doevendans, P A; Hoefer, I E; Chamuleau, S A J; van Hout, G P J; Jansen Of Lorkeers, S J

2017-10-27

Large animal models are essential for the development of novel therapeutics for myocardial infarction. To optimize translation, we need to assess the effect of experimental design on disease outcome and model experimental design to resemble the clinical course of MI. The aim of this study is therefore to systematically investigate how experimental decisions affect outcome measurements in large animal MI models. We used control animal-data from two independent meta-analyses of large animal MI models. All variables of interest were pre-defined. We performed univariable and multivariable meta-regression to analyze whether these variables influenced infarct size and ejection fraction. Our analyses incorporated 246 relevant studies. Multivariable meta-regression revealed that infarct size and cardiac function were influenced independently by choice of species, sex, co-medication, occlusion type, occluded vessel, quantification method, ischemia duration and follow-up duration. We provide strong systematic evidence that commonly used endpoints significantly depend on study design and biological variation. This makes direct comparison of different study-results difficult and calls for standardized models. Researchers should take this into account when designing large animal studies to most closely mimic the clinical course of MI and enable translational success.

A systematic review of the use of theory in randomized controlled trials of audit and feedback

PubMed Central

2013-01-01

Background Audit and feedback is one of the most widely used and promising interventions in implementation research, yet also one of the most variably effective. Understanding this variability has been limited in part by lack of attention to the theoretical and conceptual basis underlying audit and feedback. Examining the extent of theory use in studies of audit and feedback will yield better understanding of the causal pathways of audit and feedback effectiveness and inform efforts to optimize this important intervention. Methods A total of 140 studies in the 2012 Cochrane update on audit and feedback interventions were independently reviewed by two investigators. Variables were extracted related to theory use in the study design, measurement, implementation or interpretation. Theory name, associated reference, and the location of theory use as reported in the study were extracted. Theories were organized by type (e.g., education, diffusion, organization, psychology), and theory utilization was classified into seven categories (justification, intervention design, pilot testing, evaluation, predictions, post hoc, other). Results A total of 20 studies (14%) reported use of theory in any aspect of the study design, measurement, implementation or interpretation. In only 13 studies (9%) was a theory reportedly used to inform development of the intervention. A total of 18 different theories across educational, psychological, organizational and diffusion of innovation perspectives were identified. Rogers’ Diffusion of Innovations and Bandura’s Social Cognitive Theory were the most widely used (3.6% and 3%, respectively). Conclusions The explicit use of theory in studies of audit and feedback was rare. A range of theories was found, but not consistency of theory use. Advancing our understanding of audit and feedback will require more attention to theoretically informed studies and intervention design. PMID:23759034

A systematic review of the use of theory in randomized controlled trials of audit and feedback.

PubMed

Colquhoun, Heather L; Brehaut, Jamie C; Sales, Anne; Ivers, Noah; Grimshaw, Jeremy; Michie, Susan; Carroll, Kelly; Chalifoux, Mathieu; Eva, Kevin W

2013-06-10

Audit and feedback is one of the most widely used and promising interventions in implementation research, yet also one of the most variably effective. Understanding this variability has been limited in part by lack of attention to the theoretical and conceptual basis underlying audit and feedback. Examining the extent of theory use in studies of audit and feedback will yield better understanding of the causal pathways of audit and feedback effectiveness and inform efforts to optimize this important intervention. A total of 140 studies in the 2012 Cochrane update on audit and feedback interventions were independently reviewed by two investigators. Variables were extracted related to theory use in the study design, measurement, implementation or interpretation. Theory name, associated reference, and the location of theory use as reported in the study were extracted. Theories were organized by type (e.g., education, diffusion, organization, psychology), and theory utilization was classified into seven categories (justification, intervention design, pilot testing, evaluation, predictions, post hoc, other). A total of 20 studies (14%) reported use of theory in any aspect of the study design, measurement, implementation or interpretation. In only 13 studies (9%) was a theory reportedly used to inform development of the intervention. A total of 18 different theories across educational, psychological, organizational and diffusion of innovation perspectives were identified. Rogers' Diffusion of Innovations and Bandura's Social Cognitive Theory were the most widely used (3.6% and 3%, respectively). The explicit use of theory in studies of audit and feedback was rare. A range of theories was found, but not consistency of theory use. Advancing our understanding of audit and feedback will require more attention to theoretically informed studies and intervention design.

Improving Team Performance and Participation via Computer-mediated Turn Taking and Informational Prompts.

DTIC Science & Technology

1981-03-01

Abstract (continued) that time. A second independent variable studied was the use of informational prompts consisting of periodic computer displays of...resolved by allowing the person to speak first who had spoken least up to that time. A second independent variable studied was the use of...beneficial in a team which interacts repeatedly over an extended period of time. In the study to be presented here, a specially designed electronic

Theory and design of variable conductance heat pipes

NASA Technical Reports Server (NTRS)

Marcus, B. D.

1972-01-01

A comprehensive review and analysis of all aspects of heat pipe technology pertinent to the design of self-controlled, variable conductance devices for spacecraft thermal control is presented. Subjects considered include hydrostatics, hydrodynamics, heat transfer into and out of the pipe, fluid selection, materials compatibility and variable conductance control techniques. The report includes a selected bibliography of pertinent literature, analytical formulations of various models and theories describing variable conductance heat pipe behavior, and the results of numerous experiments on the steady state and transient performance of gas controlled variable conductance heat pipes. Also included is a discussion of VCHP design techniques.

Synthetic aperture radar operator tactical target acquisition research

NASA Technical Reports Server (NTRS)

Hershberger, M. L.; Craig, D. W.

1978-01-01

A radar target acquisition research study was conducted to access the effects of two levels of 13 radar sensor, display, and mission parameters on operator tactical target acquisition. A saturated fractional-factorial screening design was employed to examine these parameters. Data analysis computed ETA squared values for main and second-order effects for the variables tested. Ranking of the research parameters in terms of importance to system design revealed four variables (radar coverage, radar resolution/multiple looks, display resolution, and display size) accounted for 50 percent of the target acquisition probability variance.

Effects of Formulation Variables on the Particle Size and Drug Encapsulation of Imatinib-Loaded Solid Lipid Nanoparticles.

PubMed

Gupta, Biki; Poudel, Bijay Kumar; Pathak, Shiva; Tak, Jin Wook; Lee, Hee Hyun; Jeong, Jee-Heon; Choi, Han-Gon; Yong, Chul Soon; Kim, Jong Oh

2016-06-01

Imatinib (IMT), an anticancer agent, inhibits receptor tyrosine kinases and is characterized by poor aqueous solubility, extensive first-pass metabolism, and rapid clearance. The aims of the current study are to prepare imatinib-loaded solid lipid nanoparticles (IMT-SLN) and study the effects of associated formulation variables on particle size and drug encapsulation on IMT-SLN using an experimental design. IMT-SLN was optimized by use of a "combo" approach involving Plackett-Burman design (PBD) and Box-Behnken design (BBD). PBD screening resulted in the determination of organic-to-aqueous phase ratio (O/A), drug-to-lipid ratio (D/L), and amount of Tween® 20 (Tw20) as three significant variables for particle size (S z), drug loading (DL), and encapsulation efficiency (EE) of IMT-SLN, which were used for optimization by BBD, yielding an optimized criteria of O/A = 0.04, D/L = 0.03, and Tw20 = 2.50% w/v. The optimized IMT-SLN exhibited monodispersed particles with a size range of 69.0 ± 0.9 nm, ζ-potential of -24.2 ± 1.2 mV, and DL and EE of 2.9 ± 0.1 and 97.6 ± 0.1% w/w, respectively. Results of in vitro release study showed a sustained release pattern, presumably by diffusion and erosion, with a higher release rate at pH 5.0, compared to pH 7.4. In conclusion, use of the combo experimental design approach enabled clear understanding of the effects of various formulation variables on IMT-SLN and aided in the preparation of a system which exhibited desirable physicochemical and release characteristics.

A meta-analysis of research on science teacher education practices associated with inquiry strategy

NASA Astrophysics Data System (ADS)

Sweitzer, Gary L.; Anderson, Ronald D.

A meta-analysis was conducted of studies of teacher education having as measured outcomes one or more variables associated with inquiry teaching. Inquiry addresses those teacher behaviors that facilitate student acquisition of concepts and processes through strategies such as problem solving, uses of evidence, logical and analytical reasoning, clarification of values, and decision making. Studies which contained sufficient data for the calculation of an effect size were coded for 114 variables. These variables were divided into the following six major categories: study information and design characteristics, teacher and teacher trainee characteristics, student characteristics, treatment description, outcome description, and effect size calculation. A total of 68 studies resulting in 177 effect size calculations were coded. Mean effect sizes broken across selected variables were calculated.

Representative sets of design hydrographs for ungauged catchments: A regional approach using probabilistic region memberships

NASA Astrophysics Data System (ADS)

Brunner, Manuela Irene; Seibert, Jan; Favre, Anne-Catherine

2018-02-01

Traditional design flood estimation approaches have focused on peak discharges and have often neglected other hydrograph characteristics such as hydrograph volume and shape. Synthetic design hydrograph estimation procedures overcome this deficiency by jointly considering peak discharge, hydrograph volume, and shape. Such procedures have recently been extended to allow for the consideration of process variability within a catchment by a flood-type specific construction of design hydrographs. However, they depend on observed runoff time series and are not directly applicable in ungauged catchments where such series are not available. To obtain reliable flood estimates, there is a need for an approach that allows for the consideration of process variability in the construction of synthetic design hydrographs in ungauged catchments. In this study, we therefore propose an approach that combines a bivariate index flood approach with event-type specific synthetic design hydrograph construction. First, regions of similar flood reactivity are delineated and a classification rule that enables the assignment of ungauged catchments to one of these reactivity regions is established. Second, event-type specific synthetic design hydrographs are constructed using the pooled data divided by event type from the corresponding reactivity region in a bivariate index flood procedure. The approach was tested and validated on a dataset of 163 Swiss catchments. The results indicated that 1) random forest is a suitable classification model for the assignment of an ungauged catchment to one of the reactivity regions, 2) the combination of a bivariate index flood approach and event-type specific synthetic design hydrograph construction enables the consideration of event types in ungauged catchments, and 3) the use of probabilistic class memberships in regional synthetic design hydrograph construction helps to alleviate the problem of misclassification. Event-type specific synthetic design hydrograph sets enable the inclusion of process variability into design flood estimation and can be used as a compromise between single best estimate synthetic design hydrographs and continuous simulation studies.

Formulation and statistical optimization of self-microemulsifying drug delivery system of eprosartan mesylate for improvement of oral bioavailability.

PubMed

Dangre, Pankaj; Gilhotra, Ritu; Dhole, Shashikant

2016-10-01

The present investigation is aimed to design a statistically optimized self-microemulsifying drug delivery system (SMEDDS) of eprosartan mesylate (EM). Preliminary screening was carried out to find a suitable combination of various excipients for the formulation. A 3(2) full factorial design was employed to determine the effect of various independent variables on dependent (response) variables. The independent variables studied in the present work were concentration of oil (X 1) and the ratio of S mix (X 2), whereas the dependent variables were emulsification time (s), globule size (nm), polydispersity index (pdi), and zeta potential (mV), and the multiple linear regression analysis (MLRA) was employed to understand the influence of independent variables on dependent variables. Furthermore, a numerical optimization technique using the desirability function was used to develop a new optimized formulation with desired values of dependent variables. The optimized SMEDDS formulation of eprosartan mesylate (EMF-O) by the above method exhibited emulsification time, 118.45 ± 1.64 s; globule size, 196.81 ± 1.29 nm; zeta potential, -9.34 ± 1.2 mV, and polydispersity index, 0.354 ± 0.02. For the in vitro dissolution study, the optimized formulation (EMF-O) and pure drug were separately entrapped in the dialysis bag, and the study indicated higher release of the drug from EMF-O. In vivo pharmacokinetic studies in Wistar rats using PK solver software revealed 2.1-fold increment in oral bioavailability of EM from EMF-O, when compared with plain suspension of pure drug.

Aligning physical elements with persons' attitude: an approach using Rasch measurement theory

NASA Astrophysics Data System (ADS)

Camargo, F. R.; Henson, B.

2013-09-01

Affective engineering uses mathematical models to convert the information obtained from persons' attitude to physical elements into an ergonomic design. However, applications in the domain have not in many cases met measurement assumptions. This paper proposes a novel approach based on Rasch measurement theory to overcome the problem. The research demonstrates that if data fit the model, further variables can be added to a scale. An empirical study was designed to determine the range of compliance where consumers could obtain an impression of a moisturizer cream when touching some product containers. Persons, variables and stimulus objects were parameterised independently on a linear continuum. The results showed that a calibrated scale preserves comparability although incorporating further variables.

Applying quality by design (QbD) concept for fabrication of chitosan coated nanoliposomes.

PubMed

Pandey, Abhijeet P; Karande, Kiran P; Sonawane, Raju O; Deshmukh, Prashant K

2014-03-01

In the present investigation, a quality by design (QbD) strategy was successfully applied to the fabrication of chitosan-coated nanoliposomes (CH-NLPs) encapsulating a hydrophilic drug. The effects of the processing variables on the particle size, encapsulation efficiency (%EE) and coating efficiency (%CE) of CH-NLPs (prepared using a modified ethanol injection method) were investigated. The concentrations of lipid, cholesterol, drug and chitosan; stirring speed, sonication time; organic:aqueous phase ratio; and temperature were identified as the key factors after risk analysis for conducting a screening design study. A separate study was designed to investigate the robustness of the predicted design space. The particle size, %EE and %CE of the optimized CH-NLPs were 111.3 nm, 33.4% and 35.2%, respectively. The observed responses were in accordance with the predicted response, which confirms the suitability and robustness of the design space for CH-NLP formulation. In conclusion, optimization of the selected key variables will help minimize the problems related to size, %EE and %CE that are generally encountered when scaling up processes for NLP formulations. The robustness of the design space will help minimize both intra-batch and inter-batch variations, which are quite common in the pharmaceutical industry.

Spray-drying nanocapsules in presence of colloidal silica as drying auxiliary agent: formulation and process variables optimization using experimental designs.

PubMed

Tewa-Tagne, Patrice; Degobert, Ghania; Briançon, Stéphanie; Bordes, Claire; Gauvrit, Jean-Yves; Lanteri, Pierre; Fessi, Hatem

2007-04-01

Spray-drying process was used for the development of dried polymeric nanocapsules. The purpose of this research was to investigate the effects of formulation and process variables on the resulting powder characteristics in order to optimize them. Experimental designs were used in order to estimate the influence of formulation parameters (nanocapsules and silica concentrations) and process variables (inlet temperature, spray-flow air, feed flow rate and drying air flow rate) on spray-dried nanocapsules when using silica as drying auxiliary agent. The interactions among the formulation parameters and process variables were also studied. Responses analyzed for computing these effects and interactions were outlet temperature, moisture content, operation yield, particles size, and particulate density. Additional qualitative responses (particles morphology, powder behavior) were also considered. Nanocapsules and silica concentrations were the main factors influencing the yield, particulate density and particle size. In addition, they were concerned for the only significant interactions occurring among two different variables. None of the studied variables had major effect on the moisture content while the interaction between nanocapsules and silica in the feed was of first interest and determinant for both the qualitative and quantitative responses. The particles morphology depended on the feed formulation but was unaffected by the process conditions. This study demonstrated that drying nanocapsules using silica as auxiliary agent by spray drying process enables the obtaining of dried micronic particle size. The optimization of the process and the formulation variables resulted in a considerable improvement of product yield while minimizing the moisture content.

Framework for Computer Assisted Instruction Courseware: A Case Study.

ERIC Educational Resources Information Center

Betlach, Judith A.

1987-01-01

Systematically investigates, defines, and organizes variables related to production of internally designed and implemented computer assisted instruction (CAI) courseware: special needs of users; costs; identification and definition of realistic training needs; CAI definition and design methodology; hardware and software requirements; and general…

Shape optimization using a NURBS-based interface-enriched generalized FEM

DOE PAGES

Najafi, Ahmad R.; Safdari, Masoud; Tortorelli, Daniel A.; ...

2016-11-26

This study presents a gradient-based shape optimization over a fixed mesh using a non-uniform rational B-splines-based interface-enriched generalized finite element method, applicable to multi-material structures. In the proposed method, non-uniform rational B-splines are used to parameterize the design geometry precisely and compactly by a small number of design variables. An analytical shape sensitivity analysis is developed to compute derivatives of the objective and constraint functions with respect to the design variables. Subtle but important new terms involve the sensitivity of shape functions and their spatial derivatives. As a result, verification and illustrative problems are solved to demonstrate the precision andmore » capability of the method.« less

Optimization of Composite Structures with Curved Fiber Trajectories

NASA Astrophysics Data System (ADS)

Lemaire, Etienne; Zein, Samih; Bruyneel, Michael

2014-06-01

This paper studies the problem of optimizing composites shells manufactured using Automated Tape Layup (ATL) or Automated Fiber Placement (AFP) processes. The optimization procedure relies on a new approach to generate equidistant fiber trajectories based on Fast Marching Method. Starting with a (possibly curved) reference fiber direction defined on a (possibly curved) meshed surface, the new method allows determining fibers orientation resulting from a uniform thickness layup. The design variables are the parameters defining the position and the shape of the reference curve which results in very few design variables. Thanks to this efficient parameterization, maximum stiffness optimization numerical applications are proposed. The shape of the design space is discussed, regarding local and global optimal solutions.

Approximate simulation model for analysis and optimization in engineering system design

NASA Technical Reports Server (NTRS)

Sobieszczanski-Sobieski, Jaroslaw

1989-01-01

Computational support of the engineering design process routinely requires mathematical models of behavior to inform designers of the system response to external stimuli. However, designers also need to know the effect of the changes in design variable values on the system behavior. For large engineering systems, the conventional way of evaluating these effects by repetitive simulation of behavior for perturbed variables is impractical because of excessive cost and inadequate accuracy. An alternative is described based on recently developed system sensitivity analysis that is combined with extrapolation to form a model of design. This design model is complementary to the model of behavior and capable of direct simulation of the effects of design variable changes.

Regression dilution bias: tools for correction methods and sample size calculation.

PubMed

Berglund, Lars

2012-08-01

Random errors in measurement of a risk factor will introduce downward bias of an estimated association to a disease or a disease marker. This phenomenon is called regression dilution bias. A bias correction may be made with data from a validity study or a reliability study. In this article we give a non-technical description of designs of reliability studies with emphasis on selection of individuals for a repeated measurement, assumptions of measurement error models, and correction methods for the slope in a simple linear regression model where the dependent variable is a continuous variable. Also, we describe situations where correction for regression dilution bias is not appropriate. The methods are illustrated with the association between insulin sensitivity measured with the euglycaemic insulin clamp technique and fasting insulin, where measurement of the latter variable carries noticeable random error. We provide software tools for estimation of a corrected slope in a simple linear regression model assuming data for a continuous dependent variable and a continuous risk factor from a main study and an additional measurement of the risk factor in a reliability study. Also, we supply programs for estimation of the number of individuals needed in the reliability study and for choice of its design. Our conclusion is that correction for regression dilution bias is seldom applied in epidemiological studies. This may cause important effects of risk factors with large measurement errors to be neglected.

Optimal Design of Grid-Stiffened Panels and Shells With Variable Curvature

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.; Jaunky, Navin

2001-01-01

A design strategy for optimal design of composite grid-stiffened structures with variable curvature subjected to global and local buckling constraints is developed using a discrete optimizer. An improved smeared stiffener theory is used for the global buckling analysis. Local buckling of skin segments is assessed using a Rayleigh-Ritz method that accounts for material anisotropy and transverse shear flexibility. The local buckling of stiffener segments is also assessed. Design variables are the axial and transverse stiffener spacing, stiffener height and thickness, skin laminate, and stiffening configuration. Stiffening configuration is herein defined as a design variable that indicates the combination of axial, transverse and diagonal stiffeners in the stiffened panel. The design optimization process is adapted to identify the lightest-weight stiffening configuration and stiffener spacing for grid-stiffened composite panels given the overall panel dimensions. in-plane design loads, material properties. and boundary conditions of the grid-stiffened panel or shell.

External shading devices for energy efficient building

NASA Astrophysics Data System (ADS)

Shahdan, M. S.; Ahmad, S. S.; Hussin, M. A.

2018-02-01

External shading devices on a building façade is an important passive design strategy as they reduce solar radiation. Although studies have proven the benefits of external shading devices, many are designed solely for aesthetic purposes without fully considering its high potential to reduce solar radiation and glare. Furthermore, explorations into shading devices by the design team are mostly left too late in the design development phases. Hence, the paper looks into the effectiveness of external shading devices on a building towards more energy efficient building. The study aims to analyse the effects of various configurations of external shading devices towards the energy consumption of a case study building based on computer simulations. This study uses Building Information Modelling (BIM) through Autodesk Revit software as simulation tool. The constant variables for the simulation are the orientation of the building, types of glazing used by the building and the internal loads of the building. Whereas, the manipulated variable is the types of shading device used. The data were sorted according to the categories and translated into a chart. Analysis of the findings indicate that shading devices with different configurations show significant results in the energy consumption and the best configuration is the egg-crate shading devices. The study recommends that the consideration for shading device as a passive design strategy needs to be developed at the early stage of the building design.

The Effect of an Educational Program on Technological Literacy--The Example of a Design College in Taiwan

ERIC Educational Resources Information Center

Chu, Yuan-Hsiang

2006-01-01

The study investigated the effects of an educational intervention on the variables of awareness, perception, self-efficacy, and behavioral intentions towards technological literacy among students at a College of Design in Southern Taiwan. Using non-probability sampling, 42 freshmen students from the Department of Product Design participated in the…

A Field Study of Performance Among Embarked Infantry Personnel Exposed to Waterborne Motion

DTIC Science & Technology

2012-09-01

was designed with four groups with 16 participants per group to accommodate the calculated sample size and the maximum seating capacity of the...25  A.  APPROACH TO THE EXPERIMENTAL DESIGN .................................25  B.  VARIABLES...39  viii 1.  Design of the Training Period ...........................................................39  2.  Training Period

Changing Women's Ascriptions through a Leadership Training Program.

ERIC Educational Resources Information Center

Connell, Jim; Kimmel, Ellen B.

The purpose of this study was to determine if an intervention package designed to develop the administrative and managerial skills of women vocational educators would change their ascriptions to resemble those of male high achievers. The independent variable was a 2-week residential institute held in June 1982. The dependent variable was…

Effect of Scientific Argumentation on the Development of Scientific Process Skills in the Context of Teaching Chemistry

ERIC Educational Resources Information Center

Gultepe, Nejla; Kilic, Ziya

2015-01-01

This study was conducted in order to determine the differences in integrated scientific process skills (designing experiments, forming data tables, drawing graphs, graph interpretation, determining the variables and hypothesizing, changing and controlling variables) of students (n = 17) who were taught with an approach based on scientific…

Engineering Students Designing a Statistical Procedure for Quantifying Variability

ERIC Educational Resources Information Center

Hjalmarson, Margret A.

2007-01-01

The study examined first-year engineering students' responses to a statistics task that asked them to generate a procedure for quantifying variability in a data set from an engineering context. Teams used technological tools to perform computations, and their final product was a ranking procedure. The students could use any statistical measures,…

The Role of Schools, Families, and Psychological Variables on Math Achievement of Black High School Students

ERIC Educational Resources Information Center

Strayhorn, Terrell L.

2010-01-01

Using data from the National Education Longitudinal Study (NELS;1988/2000), the author conducted hierarchical linear regression analyses, with a nested design, to estimate the influence of affective variables--parent involvement, teacher perceptions, and school environments--on Black students' math achievement in grade 10. Drawing on…

The Prevalence of Low Self-Esteem in an Intellectually Disabled Forensic Population

ERIC Educational Resources Information Center

Johnson, P.

2012-01-01

Background: This was a quantitative study to measure the prevalence low self-esteem in an intellectually disabled forensic population. The dependent variables used were the adapted six-item Rosenberg Self-Esteem Scale and the adapted Evaluative Beliefs Scale. It had a repeated measures design with independent variables including consideration of…

Digital Technology and Caregiver Training for Older Persons: Cognitive and Affective Perspectives

ERIC Educational Resources Information Center

Zheng, Robert; Hicken, Bret L.; Hill, Robert D.; Luptak, Marilyn; Daniel, Candice M.; Grant, Marren; Rupper, Randall

2016-01-01

This research project included two studies that investigated (a) differences between technology use in tech-knowledgeable and less tech-knowledgeable older persons, (b) cognitive and affective variables and their association with the application of technology, and (c) the implications of these variables on the design of remote-delivered caregiver…

Variability in range cow mineral use is associated with season and daily high temperature in Northern Great Plains

USDA-ARS?s Scientific Manuscript database

Accurate assessment of mineral nutrition in range cattle is complicated by seasonal changes in diet mineral concentrations, shifting requirements and a lack of knowledge of seasonal mineral intake variability. This study was designed to evaluate variation in herd mineral intake, and individual cow m...

Soil Wetness Influences Log Skidding

Treesearch

William N. Darwin

1960-01-01

One of the least explored variables in timber harvesting is the effect of ground conditions on log production . The Southern Hardwoods Laboratory is studying this variable and its influence on performance of skidding vehicles in Southern bottom lands. The test reported here was designed to evaluate the effects of bark features on skidding coefficients, but it also...

Testing the Effectiveness of a Career Education Program for Potential Dropouts.

ERIC Educational Resources Information Center

Schmidt, Wesley I.; Dykeman, Bruce F.

1979-01-01

Using a randomized two group pre-test/post-test research design, the study found that (1) significant results occurred on those variables measuring levels of vocational maturity, days of school attendance, and numbers of disciplinary referrals and (2) non-significant results occurred on those variables measuring proportions of students dropping…

Invited review: study design considerations for clinical research in veterinary radiology and radiation oncology.

PubMed

Scrivani, Peter V; Erb, Hollis N

2013-01-01

High quality clinical research is essential for advancing knowledge in the areas of veterinary radiology and radiation oncology. Types of clinical research studies may include experimental studies, method-comparison studies, and patient-based studies. Experimental studies explore issues relative to pathophysiology, patient safety, and treatment efficacy. Method-comparison studies evaluate agreement between techniques or between observers. Patient-based studies investigate naturally acquired disease and focus on questions asked in clinical practice that relate to individuals or populations (e.g., risk, accuracy, or prognosis). Careful preplanning and study design are essential in order to achieve valid results. A key point to planning studies is ensuring that the design is tailored to the study objectives. Good design includes a comprehensive literature review, asking suitable questions, selecting the proper sample population, collecting the appropriate data, performing the correct statistical analyses, and drawing conclusions supported by the available evidence. Most study designs are classified by whether they are experimental or observational, longitudinal or cross-sectional, and prospective or retrospective. Additional features (e.g., controlled, randomized, or blinded) may be described that address bias. Two related challenging aspects of study design are defining an important research question and selecting an appropriate sample population. The sample population should represent the target population as much as possible. Furthermore, when comparing groups, it is important that the groups are as alike to each other as possible except for the variables of interest. Medical images are well suited for clinical research because imaging signs are categorical or numerical variables that might be predictors or outcomes of diseases or treatments. © 2013 Veterinary Radiology & Ultrasound.

Earth Observatory Satellite system definition study. Report no. 3: Design/cost tradeoff studies

NASA Technical Reports Server (NTRS)

1974-01-01

The key issues in the Earth Observatory Satellite (EOS) program which are subject to configuration study and tradeoff are identified. The issue of a combined operational and research and development program is considered. It is stated that cost and spacecraft weight are the key design variables and design options are proposed in terms of these parameters. A cost analysis of the EOS program is provided. Diagrams of the satellite configuration and subsystem components are included.

Biodiversity in canopy-forming algae: Structure and spatial variability of the Mediterranean Cystoseira assemblages

NASA Astrophysics Data System (ADS)

Piazzi, L.; Bonaviri, C.; Castelli, A.; Ceccherelli, G.; Costa, G.; Curini-Galletti, M.; Langeneck, J.; Manconi, R.; Montefalcone, M.; Pipitone, C.; Rosso, A.; Pinna, S.

2018-07-01

In the Mediterranean Sea, Cystoseira species are the most important canopy-forming algae in shallow rocky bottoms, hosting high biodiverse sessile and mobile communities. A large-scale study has been carried out to investigate the structure of the Cystoseira-dominated assemblages at different spatial scales and to test the hypotheses that alpha and beta diversity of the assemblages, the abundance and the structure of epiphytic macroalgae, epilithic macroalgae, sessile macroinvertebrates and mobile macroinvertebrates associated to Cystoseira beds changed among scales. A hierarchical sampling design in a total of five sites across the Mediterranean Sea (Croatia, Montenegro, Sardinia, Tuscany and Balearic Islands) was used. A total of 597 taxa associated to Cystoseira beds were identified with a mean number per sample ranging between 141.1 ± 6.6 (Tuscany) and 173.9 ± 8.5(Sardinia). A high variability at small (among samples) and large (among sites) scale was generally highlighted, but the studied assemblages showed different patterns of spatial variability. The relative importance of the different scales of spatial variability should be considered to optimize sampling designs and propose monitoring plans of this habitat.

Effects of Spaced Training in Creative Imagination and Delayed Posttesting on Originality.

ERIC Educational Resources Information Center

Masten, William G.; Hairston, Susan A.

While there is increasing evidence that creativity can be improved through training, the spacing of the training has not been studied. This study assessed the effect of spaced training on the use of creative imagination in 110 undergraduate students. The research design was a randomized delayed posttest-only design. The independent variable was…

An Investigation of the Effects of Relevant Samples and a Comparison of Verification versus Discovery Based Lab Design

ERIC Educational Resources Information Center

Rieben, James C., Jr.

2010-01-01

This study focuses on the effects of relevance and lab design on student learning within the chemistry laboratory environment. A general chemistry conductivity of solutions experiment and an upper level organic chemistry cellulose regeneration experiment were employed. In the conductivity experiment, the two main variables studied were the effect…

Variable Complexity Optimization of Composite Structures

NASA Technical Reports Server (NTRS)

Haftka, Raphael T.

2002-01-01

The use of several levels of modeling in design has been dubbed variable complexity modeling. The work under the grant focused on developing variable complexity modeling strategies with emphasis on response surface techniques. Applications included design of stiffened composite plates for improved damage tolerance, the use of response surfaces for fitting weights obtained by structural optimization, and design against uncertainty using response surface techniques.

Compensation for Lithography Induced Process Variations during Physical Design

NASA Astrophysics Data System (ADS)

Chin, Eric Yiow-Bing

This dissertation addresses the challenge of designing robust integrated circuits in the deep sub micron regime in the presence of lithography process variability. By extending and combining existing process and circuit analysis techniques, flexible software frameworks are developed to provide detailed studies of circuit performance in the presence of lithography variations such as focus and exposure. Applications of these software frameworks to select circuits demonstrate the electrical impact of these variations and provide insight into variability aware compact models that capture the process dependent circuit behavior. These variability aware timing models abstract lithography variability from the process level to the circuit level and are used to estimate path level circuit performance with high accuracy with very little overhead in runtime. The Interconnect Variability Characterization (IVC) framework maps lithography induced geometrical variations at the interconnect level to electrical delay variations. This framework is applied to one dimensional repeater circuits patterned with both 90nm single patterning and 32nm double patterning technologies, under the presence of focus, exposure, and overlay variability. Studies indicate that single and double patterning layouts generally exhibit small variations in delay (between 1--3%) due to self compensating RC effects associated with dense layouts and overlay errors for layouts without self-compensating RC effects. The delay response of each double patterned interconnect structure is fit with a second order polynomial model with focus, exposure, and misalignment parameters with 12 coefficients and residuals of less than 0.1ps. The IVC framework is also applied to a repeater circuit with cascaded interconnect structures to emulate more complex layout scenarios, and it is observed that the variations on each segment average out to reduce the overall delay variation. The Standard Cell Variability Characterization (SCVC) framework advances existing layout-level lithography aware circuit analysis by extending it to cell-level applications utilizing a physically accurate approach that integrates process simulation, compact transistor models, and circuit simulation to characterize electrical cell behavior. This framework is applied to combinational and sequential cells in the Nangate 45nm Open Cell Library, and the timing response of these cells to lithography focus and exposure variations demonstrate Bossung like behavior. This behavior permits the process parameter dependent response to be captured in a nine term variability aware compact model based on Bossung fitting equations. For a two input NAND gate, the variability aware compact model captures the simulated response to an accuracy of 0.3%. The SCVC framework is also applied to investigate advanced process effects including misalignment and layout proximity. The abstraction of process variability from the layout level to the cell level opens up an entire new realm of circuit analysis and optimization and provides a foundation for path level variability analysis without the computationally expensive costs associated with joint process and circuit simulation. The SCVC framework is used with slight modification to illustrate the speedup and accuracy tradeoffs of using compact models. With variability aware compact models, the process dependent performance of a three stage logic circuit can be estimated to an accuracy of 0.7% with a speedup of over 50,000. Path level variability analysis also provides an accurate estimate (within 1%) of ring oscillator period in well under a second. Another significant advantage of variability aware compact models is that they can be easily incorporated into existing design methodologies for design optimization. This is demonstrated by applying cell swapping on a logic circuit to reduce the overall delay variability along a circuit path. By including these variability aware compact models in cell characterization libraries, design metrics such as circuit timing, power, area, and delay variability can be quickly assessed to optimize for the correct balance of all design metrics, including delay variability. Deterministic lithography variations can be easily captured using the variability aware compact models described in this dissertation. However, another prominent source of variability is random dopant fluctuations, which affect transistor threshold voltage and in turn circuit performance. The SCVC framework is utilized to investigate the interactions between deterministic lithography variations and random dopant fluctuations. Monte Carlo studies show that the output delay distribution in the presence of random dopant fluctuations is dependent on lithography focus and exposure conditions, with a 3.6 ps change in standard deviation across the focus exposure process window. This indicates that the electrical impact of random variations is dependent on systematic lithography variations, and this dependency should be included for precise analysis.

The Oporto mixed-longitudinal growth, health and performance study. Design, methods and baseline results.

PubMed

Souza, Michele Caroline de; Chaves, Raquel Nichele de; Dos Santos, Fernanda Karina; Gomes, Thayse Natacha Queiroz Ferreira; Santos, Daniel Vilhena E; Borges, Alessandra Silva; Pereira, Sara Isabel Sampaio; Forjaz, Cláudia Lúcia de Moraes; Eisenmann, Joey; Maia, José António Ribeiro

2017-02-01

Studies concerning child and adolescent growth, development, performance and health aimed at the multiple interactions amongst this complex set of variables are not common in the Portuguese speaking countries. The aim of this paper is to address the key ideas, methodology and design of the Oporto Growth, Health and Performance Study (OGHPS). The OGHPS is a multidisciplinary mixed-longitudinal study whose main purpose is to examine the multiple interactions among biological, environmental and lifestyle indicators that affect growth, development, health and performance of Portuguese adolescents aged 10-18 years old. This study briefly presents baseline results for growth, physical fitness and lifestyle behaviours for those participating in the cross-sectional sample (n ≈ 8000). Approximately 30% were over-fat or obese. On average, boys were more physically fit and active than girls. Few adolescents meet the guidelines for sleep duration (≈10%) and eating habits (16.2-24.8%), while 76-85% meet the recommended levels of moderate-to-vigorous physical activity. The OGHPS has an innovative approach due to its mixed-longitudinal design and the broad array of variables. Furthermore, subsequent analyses of the longitudinal data will enable a detailed exploration of important factors affecting the growth trajectories of health and performance variables and will also help to identify some of the most opportune times for interventions in terms of health behaviours.

A conceptual framework for the domain of evidence-based design.

PubMed

Ulrich, Roger S; Berry, Leonard L; Quan, Xiaobo; Parish, Janet Turner

2010-01-01

The physical facilities in which healthcare services are performed play an important role in the healing process. Evidence-based design in healthcare is a developing field of study that holds great promise for benefiting key stakeholders: patients, families, physicians, and nurses, as well as other healthcare staff and organizations. In this paper, the authors present and discuss a conceptual framework intended to capture the current domain of evidence-based design in healthcare. In this framework, the built environment is represented by nine design variable categories: audio environment, visual environment, safety enhancement, wayfinding system, sustainability, patient room, family support spaces, staff support spaces, and physician support spaces. Furthermore, a series of matrices is presented that indicates knowledge gaps concerning the relationship between specific healthcare facility design variable categories and participant and organizational outcomes. From this analysis, the authors identify fertile research opportunities from the perspectives of key stakeholders.

Multi-objective aerodynamic shape optimization of small livestock trailers

NASA Astrophysics Data System (ADS)

Gilkeson, C. A.; Toropov, V. V.; Thompson, H. M.; Wilson, M. C. T.; Foxley, N. A.; Gaskell, P. H.

2013-11-01

This article presents a formal optimization study of the design of small livestock trailers, within which the majority of animals are transported to market in the UK. The benefits of employing a headboard fairing to reduce aerodynamic drag without compromising the ventilation of the animals' microclimate are investigated using a multi-stage process involving computational fluid dynamics (CFD), optimal Latin hypercube (OLH) design of experiments (DoE) and moving least squares (MLS) metamodels. Fairings are parameterized in terms of three design variables and CFD solutions are obtained at 50 permutations of design variables. Both global and local search methods are employed to locate the global minimum from metamodels of the objective functions and a Pareto front is generated. The importance of carefully selecting an objective function is demonstrated and optimal fairing designs, offering drag reductions in excess of 5% without compromising animal ventilation, are presented.

Probabilistic Analysis and Design of a Raked Wing Tip for a Commercial Transport

NASA Technical Reports Server (NTRS)

Mason Brian H.; Chen, Tzi-Kang; Padula, Sharon L.; Ransom, Jonathan B.; Stroud, W. Jefferson

2008-01-01

An approach for conducting reliability-based design and optimization (RBDO) of a Boeing 767 raked wing tip (RWT) is presented. The goal is to evaluate the benefits of RBDO for design of an aircraft substructure. A finite-element (FE) model that includes eight critical static load cases is used to evaluate the response of the wing tip. Thirteen design variables that describe the thickness of the composite skins and stiffeners are selected to minimize the weight of the wing tip. A strain-based margin of safety is used to evaluate the performance of the structure. The randomness in the load scale factor and in the strain limits is considered. Of the 13 variables, the wing-tip design was controlled primarily by the thickness of the thickest plies in the upper skins. The report includes an analysis of the optimization results and recommendations for future reliability-based studies.

Combined loading criterial influence on structural performance

NASA Technical Reports Server (NTRS)

Kuchta, B. J.; Sealey, D. M.; Howell, L. J.

1972-01-01

An investigation was conducted to determine the influence of combined loading criteria on the space shuttle structural performance. The study consisted of four primary phases: Phase (1) The determination of the sensitivity of structural weight to various loading parameters associated with the space shuttle. Phase (2) The determination of the sensitivity of structural weight to various levels of loading parameter variability and probability. Phase (3) The determination of shuttle mission loading parameters variability and probability as a function of design evolution and the identification of those loading parameters where inadequate data exists. Phase (4) The determination of rational methods of combining both deterministic time varying and probabilistic loading parameters to provide realistic design criteria. The study results are presented.

An Ex Post Facto Study Exploring the Impact of Parental Level of Education and Parental Support on First-Year College Adjustment

ERIC Educational Resources Information Center

Huntley, Kristy M.

2011-01-01

This study explored the impact that parental levels of education and parental support have on college adjustment for first-year students. An ex post facto design was used to examine parental level of education and parental support as variables. Parental level of education is a categorical variable based on report from the student. Parental support…

Optimization under variability and uncertainty: a case study for NOx emissions control for a gasification system.

PubMed

Chen, Jianjun; Frey, H Christopher

2004-12-15

Methods for optimization of process technologies considering the distinction between variability and uncertainty are developed and applied to case studies of NOx control for Integrated Gasification Combined Cycle systems. Existing methods of stochastic optimization (SO) and stochastic programming (SP) are demonstrated. A comparison of SO and SP results provides the value of collecting additional information to reduce uncertainty. For example, an expected annual benefit of 240,000 dollars is estimated if uncertainty can be reduced before a final design is chosen. SO and SP are typically applied to uncertainty. However, when applied to variability, the benefit of dynamic process control is obtained. For example, an annual savings of 1 million dollars could be achieved if the system is adjusted to changes in process conditions. When variability and uncertainty are treated distinctively, a coupled stochastic optimization and programming method and a two-dimensional stochastic programming method are demonstrated via a case study. For the case study, the mean annual benefit of dynamic process control is estimated to be 700,000 dollars, with a 95% confidence range of 500,000 dollars to 940,000 dollars. These methods are expected to be of greatest utility for problems involving a large commitment of resources, for which small differences in designs can produce large cost savings.

Sociocultural variables in youth access to tobacco: replication 5 years later.

PubMed

Landrine, H; Klonoff, E A; Campbell, R; Reina-Patton, A

2000-05-01

A prior study presented the only systematic investigation of the role of sociocultural variables in youth access to tobacco. White, black, and Latino girls and boys attempted to purchase cigarettes in the same 72 stores at the same time of day. Results revealed significantly greater sales to girls than to boys and to minorities than to whites. Before concluding that sociocultural variables must be addressed in merchant intervention programs designed to reduce youth access to tobacco, this study must be replicated, particularly in light of the significant decreases in youth access in the past 5 years. This article presents that replication. The stores used in the prior study were selected, and 12 white, black, and Latino girls and boys attempted to purchase cigarettes in those stores at the same time of day. Results Youths' access rate in 1999 (12.7%) was significantly lower than in the prior (1993-1995) study (41%). No effect for minors' gender was found, but the ethnicity effect again emerged: Black and Latino youth were 2.5 times more likely to be sold cigarettes than their white counterparts. Multiple sociocultural variables affect youth access to tobacco when access rates are high, but only youth ethnicity plays a role when access rates are low. Merchant interventions designed to reduce youth access to tobacco must address ethnic issues.

Developing a conceptual model for the application of patient and public involvement in the healthcare system in Iran.

PubMed

Azmal, Mohammad; Sari, Ali Akbari; Foroushani, Abbas Rahimi; Ahmadi, Batoul

2016-06-01

Patient and public involvement is engaging patients, providers, community representatives, and the public in healthcare planning and decision-making. The purpose of this study was to develop a model for the application of patient and public involvement in decision making in the Iranian healthcare system. A mixed qualitative-quantitative approach was used to develop a conceptual model. Thirty three key informants were purposely recruited in the qualitative stage, and 420 people (patients and their companions) were included in a protocol study that was implemented in five steps: 1) Identifying antecedents, consequences, and variables associated with the patient and the publics' involvement in healthcare decision making through a comprehensive literature review; 2) Determining the main variables in the context of Iran's health system using conceptual framework analysis; 3) Prioritizing and weighting variables by Shannon entropy; 4) designing and validating a tool for patient and public involvement in healthcare decision making; and 5) Providing a conceptual model of patient and the public involvement in planning and developing healthcare using structural equation modeling. We used various software programs, including SPSS (17), Max QDA (10), EXCEL, and LISREL. Content analysis, Shannon entropy, and descriptive and analytic statistics were used to analyze the data. In this study, seven antecedents variable, five dimensions of involvement, and six consequences were identified. These variables were used to design a valid tool. A logical model was derived that explained the logical relationships between antecedent and consequent variables and the dimensions of patient and public involvement as well. Given the specific context of the political, social, and innovative environments in Iran, it was necessary to design a model that would be compatible with these features. It can improve the quality of care and promote the patient and the public satisfaction with healthcare and legitimate the representative of people they served for. This model can provide a practical guide for managers and policy makers to involve people in making the decisions that influence their lives.

Optimization methods applied to hybrid vehicle design

NASA Technical Reports Server (NTRS)

Donoghue, J. F.; Burghart, J. H.

1983-01-01

The use of optimization methods as an effective design tool in the design of hybrid vehicle propulsion systems is demonstrated. Optimization techniques were used to select values for three design parameters (battery weight, heat engine power rating and power split between the two on-board energy sources) such that various measures of vehicle performance (acquisition cost, life cycle cost and petroleum consumption) were optimized. The apporach produced designs which were often significant improvements over hybrid designs already reported on in the literature. The principal conclusions are as follows. First, it was found that the strategy used to split the required power between the two on-board energy sources can have a significant effect on life cycle cost and petroleum consumption. Second, the optimization program should be constructed so that performance measures and design variables can be easily changed. Third, the vehicle simulation program has a significant effect on the computer run time of the overall optimization program; run time can be significantly reduced by proper design of the types of trips the vehicle takes in a one year period. Fourth, care must be taken in designing the cost and constraint expressions which are used in the optimization so that they are relatively smooth functions of the design variables. Fifth, proper handling of constraints on battery weight and heat engine rating, variables which must be large enough to meet power demands, is particularly important for the success of an optimization study. Finally, the principal conclusion is that optimization methods provide a practical tool for carrying out the design of a hybrid vehicle propulsion system.

A multiple-alignment based primer design algorithm for genetically highly variable DNA targets

PubMed Central

2013-01-01

Background Primer design for highly variable DNA sequences is difficult, and experimental success requires attention to many interacting constraints. The advent of next-generation sequencing methods allows the investigation of rare variants otherwise hidden deep in large populations, but requires attention to population diversity and primer localization in relatively conserved regions, in addition to recognized constraints typically considered in primer design. Results Design constraints include degenerate sites to maximize population coverage, matching of melting temperatures, optimizing de novo sequence length, finding optimal bio-barcodes to allow efficient downstream analyses, and minimizing risk of dimerization. To facilitate primer design addressing these and other constraints, we created a novel computer program (PrimerDesign) that automates this complex procedure. We show its powers and limitations and give examples of successful designs for the analysis of HIV-1 populations. Conclusions PrimerDesign is useful for researchers who want to design DNA primers and probes for analyzing highly variable DNA populations. It can be used to design primers for PCR, RT-PCR, Sanger sequencing, next-generation sequencing, and other experimental protocols targeting highly variable DNA samples. PMID:23965160

"EWS Matrix" and "EWG Matrix": "De-sign for All" tools referred to the development of a enabling communication system for public spaces.

PubMed

Di Bucchianico, Giuseppe; Camplone, Stefania; Picciani, Stefano; Vallese, Valeria

2012-01-01

The widespread sense of spatial disorientation that can be experienced in many public places (buildings and open spaces),generally depends on a design approach that doesn't take into account both the "communication skills" of the different parts of the spatial organization, both the variability of people and their ways of interacting with environments, orienteering themselves. Nevertheless, "not find the way" often has some obvious practical costs (loss of time, failure to achieve a target) and some more intangible, but no less important, emotional costs. That's why the design of signage systems must take into account both the specificities of places and the extreme variability of its users. The paper presents the results of a study on this specific issue. In particular, the study focuses on the description of some tools useful for the analysis and design of a signage system that is truly "for All".

Statistical power for the comparative regression discontinuity design with a nonequivalent comparison group.

PubMed

Tang, Yang; Cook, Thomas D; Kisbu-Sakarya, Yasemin

2018-03-01

In the "sharp" regression discontinuity design (RD), all units scoring on one side of a designated score on an assignment variable receive treatment, whereas those scoring on the other side become controls. Thus the continuous assignment variable and binary treatment indicator are measured on the same scale. Because each must be in the impact model, the resulting multi-collinearity reduces the efficiency of the RD design. However, untreated comparison data can be added along the assignment variable, and a comparative regression discontinuity design (CRD) is then created. When the untreated data come from a non-equivalent comparison group, we call this CRD-CG. Assuming linear functional forms, we show that power in CRD-CG is (a) greater than in basic RD; (b) less sensitive to the location of the cutoff and the distribution of the assignment variable; and that (c) fewer treated units are needed in the basic RD component within the CRD-CG so that savings can result from having fewer treated cases. The theory we develop is used to make numerical predictions about the efficiency of basic RD and CRD-CG relative to each other and to a randomized control trial. Data from the National Head Start Impact study are used to test these predictions. The obtained estimates are closer to the predicted parameters for CRD-CG than for basic RD and are generally quite close to the parameter predictions, supporting the emerging argument that CRD should be the design of choice in many applications for which basic RD is now used. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Optimization of formulation variables of benzocaine liposomes using experimental design.

PubMed

Mura, Paola; Capasso, Gaetano; Maestrelli, Francesca; Furlanetto, Sandra

2008-01-01

This study aimed to optimize, by means of an experimental design multivariate strategy, a liposomal formulation for topical delivery of the local anaesthetic agent benzocaine. The formulation variables for the vesicle lipid phase uses potassium glycyrrhizinate (KG) as an alternative to cholesterol and the addition of a cationic (stearylamine) or anionic (dicethylphosphate) surfactant (qualitative factors); the percents of ethanol and the total volume of the hydration phase (quantitative factors) were the variables for the hydrophilic phase. The combined influence of these factors on the considered responses (encapsulation efficiency (EE%) and percent drug permeated at 180 min (P%)) was evaluated by means of a D-optimal design strategy. Graphic analysis of the effects indicated that maximization of the selected responses requested opposite levels of the considered factors: For example, KG and stearylamine were better for increasing EE%, and cholesterol and dicethylphosphate for increasing P%. In the second step, the Doehlert design, applied for the response-surface study of the quantitative factors, pointed out a negative interaction between percent ethanol and volume of the hydration phase and allowed prediction of the best formulation for maximizing drug permeation rate. Experimental P% data of the optimized formulation were inside the confidence interval (P < 0.05) calculated around the predicted value of the response. This proved the suitability of the proposed approach for optimizing the composition of liposomal formulations and predicting the effects of formulation variables on the considered experimental response. Moreover, the optimized formulation enabled a significant improvement (P < 0.05) of the drug anaesthetic effect with respect to the starting reference liposomal formulation, thus demonstrating its actually better therapeutic effectiveness.

Probabilistic Structural Evaluation of Uncertainties in Radiator Sandwich Panel Design

NASA Technical Reports Server (NTRS)

Kuguoglu, Latife; Ludwiczak, Damian

2006-01-01

The Jupiter Icy Moons Orbiter (JIMO) Space System is part of the NASA's Prometheus Program. As part of the JIMO engineering team at NASA Glenn Research Center, the structural design of the JIMO Heat Rejection Subsystem (HRS) is evaluated. An initial goal of this study was to perform sensitivity analyses to determine the relative importance of the input variables on the structural responses of the radiator panel. The desire was to let the sensitivity analysis information identify the important parameters. The probabilistic analysis methods illustrated here support this objective. The probabilistic structural performance evaluation of a HRS radiator sandwich panel was performed. The radiator panel structural performance was assessed in the presence of uncertainties in the loading, fabrication process variables, and material properties. The stress and displacement contours of the deterministic structural analysis at mean probability was performed and results presented. It is followed by a probabilistic evaluation to determine the effect of the primitive variables on the radiator panel structural performance. Based on uncertainties in material properties, structural geometry and loading, the results of the displacement and stress analysis are used as an input file for the probabilistic analysis of the panel. The sensitivity of the structural responses, such as maximum displacement and maximum tensile and compressive stresses of the facesheet in x and y directions and maximum VonMises stresses of the tube, to the loading and design variables is determined under the boundary condition where all edges of the radiator panel are pinned. Based on this study, design critical material and geometric parameters of the considered sandwich panel are identified.

Computer-aided design of customized foot orthoses: reproducibility and effect of method used to obtain foot shape.

PubMed

Telfer, Scott; Gibson, Kellie S; Hennessy, Kym; Steultjens, Martijn P; Woodburn, Jim

2012-05-01

To determine, for a number of techniques used to obtain foot shape based around plaster casting, foam box impressions, and 3-dimensional scanning, (1) the effect the technique has on the overall reproducibility of custom foot orthoses (FOs) in terms of inter- and intracaster reliability and (2) the reproducibility of FO design by using computer-aided design (CAD) software in terms of inter- and intra-CAD operator reliability for all these techniques. Cross-sectional study. University laboratory. Convenience sample of individuals (N=22) with noncavus foot types. Not applicable. Parameters of the FO design (length, width at forefoot, width at rearfoot, and peak medial arch height), the forefoot to rearfoot angle of the foot shape, and overall volume match between device designs. For intra- and intercaster reliability of the different methods of obtaining the foot shape, all methods fell below the reproducibility quality threshold for the medial arch height of the device, and volume matching was <80% for all methods. The more experienced CAD operator was able to achieve excellent reliability (intraclass correlation coefficients >0.75) for all variables with the exception of forefoot to rearfoot angle, with overall volume matches of >87% of the devices. None of the techniques for obtaining foot shape met all the criteria for excellent reproducibility, with the peak arch height being particularly variable. Additional variability is added at the CAD stage of the FO design process, although with adequate operator experience good to excellent reproducibility may be achieved at this stage. Taking only basic linear or angular measurement parameters from the device may fail to fully capture the variability in FO design. Copyright © 2012 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Variability of bioaccessibility results using seventeen different methods on a standard reference material, NIST 2710.

PubMed

Koch, Iris; Reimer, Kenneth J; Bakker, Martine I; Basta, Nicholas T; Cave, Mark R; Denys, Sébastien; Dodd, Matt; Hale, Beverly A; Irwin, Rob; Lowney, Yvette W; Moore, Margo M; Paquin, Viviane; Rasmussen, Pat E; Repaso-Subang, Theresa; Stephenson, Gladys L; Siciliano, Steven D; Wragg, Joanna; Zagury, Gerald J

2013-01-01

Bioaccessibility is a measurement of a substance's solubility in the human gastro-intestinal system, and is often used in the risk assessment of soils. The present study was designed to determine the variability among laboratories using different methods to measure the bioaccessibility of 24 inorganic contaminants in one standardized soil sample, the standard reference material NIST 2710. Fourteen laboratories used a total of 17 bioaccessibility extraction methods. The variability between methods was assessed by calculating the reproducibility relative standard deviations (RSDs), where reproducibility is the sum of within-laboratory and between-laboratory variability. Whereas within-laboratory repeatability was usually better than (<) 15% for most elements, reproducibility RSDs were much higher, indicating more variability, although for many elements they were comparable to typical uncertainties (e.g., 30% in commercial laboratories). For five trace elements of interest, reproducibility RSDs were: arsenic (As), 22-44%; cadmium (Cd), 11-41%; Cu, 15-30%; lead (Pb), 45-83%; and Zn, 18-56%. Only one method variable, pH, was found to correlate significantly with bioaccessibility for aluminum (Al), Cd, copper (Cu), manganese (Mn), Pb and zinc (Zn) but other method variables could not be examined systematically because of the study design. When bioaccessibility results were directly compared with bioavailability results for As (swine and mouse) and Pb (swine), four methods returned results within uncertainty ranges for both elements: two that were defined as simpler (gastric phase only, limited chemicals) and two were more complex (gastric + intestinal phases, with a mixture of chemicals).

Variability in Non-Target Terrestrial Plant Studies Should Inform Endpoint Selection.

PubMed

Staveley, J P; Green, J W; Nusz, J; Edwards, D; Henry, K; Kern, M; Deines, A M; Brain, R; Glenn, B; Ehresman, N; Kung, T; Ralston-Hooper, K; Kee, F; McMaster, S

2018-05-04

Inherent variability in Non-Target Terrestrial Plant (NTTP) testing of pesticides creates challenges for using and interpreting these data for risk assessment. Standardized NTTP testing protocols were initially designed to calculate the application rate causing a 25% effect (ER25, used in the U.S.) or a 50% effect (ER50, used in Europe) for various measures based on the observed dose-response. More recently, the requirement to generate a no-observed-effect rate (NOER), or, in the absence of a NOER, the rate causing a 5% effect (ER05), has raised questions about the inherent variability in, and statistical detectability of, these tests. Statistically significant differences observed between test and control groups may be a product of this inherent variability and may not represent biological relevance. Attempting to derive an ER05 and the associated risk assessment conclusions drawn from these values can overestimate risk. To address these concerns, we evaluated historical data from approximately 100 seedling emergence and vegetative vigor guideline studies on pesticides to assess the variability of control results across studies for each plant species, examined potential causes for the variation in control results, and defined the minimum percent effect that can be reliably detected. The results indicate that with current test design and implementation, the ER05 cannot be reliably estimated. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Optimal Design of General Stiffened Composite Circular Cylinders for Global Buckling with Strength Constraints

NASA Technical Reports Server (NTRS)

Jaunky, N.; Ambur, D. R.; Knight, N. F., Jr.

1998-01-01

A design strategy for optimal design of composite grid-stiffened cylinders subjected to global and local buckling constraints and strength constraints was developed using a discrete optimizer based on a genetic algorithm. An improved smeared stiffener theory was used for the global analysis. Local buckling of skin segments were assessed using a Rayleigh-Ritz method that accounts for material anisotropy. The local buckling of stiffener segments were also assessed. Constraints on the axial membrane strain in the skin and stiffener segments were imposed to include strength criteria in the grid-stiffened cylinder design. Design variables used in this study were the axial and transverse stiffener spacings, stiffener height and thickness, skin laminate stacking sequence and stiffening configuration, where stiffening configuration is a design variable that indicates the combination of axial, transverse and diagonal stiffener in the grid-stiffened cylinder. The design optimization process was adapted to identify the best suited stiffening configurations and stiffener spacings for grid-stiffened composite cylinder with the length and radius of the cylinder, the design in-plane loads and material properties as inputs. The effect of having axial membrane strain constraints in the skin and stiffener segments in the optimization process is also studied for selected stiffening configurations.

Optimal Design of General Stiffened Composite Circular Cylinders for Global Buckling with Strength Constraints

NASA Technical Reports Server (NTRS)

Jaunky, Navin; Knight, Norman F., Jr.; Ambur, Damodar R.

1998-01-01

A design strategy for optimal design of composite grid-stiffened cylinders subjected to global and local buckling constraints and, strength constraints is developed using a discrete optimizer based on a genetic algorithm. An improved smeared stiffener theory is used for the global analysis. Local buckling of skin segments are assessed using a Rayleigh-Ritz method that accounts for material anisotropy. The local buckling of stiffener segments are also assessed. Constraints on the axial membrane strain in the skin and stiffener segments are imposed to include strength criteria in the grid-stiffened cylinder design. Design variables used in this study are the axial and transverse stiffener spacings, stiffener height and thickness, skin laminate stacking sequence, and stiffening configuration, where herein stiffening configuration is a design variable that indicates the combination of axial, transverse, and diagonal stiffener in the grid-stiffened cylinder. The design optimization process is adapted to identify the best suited stiffening configurations and stiffener spacings for grid-stiffened composite cylinder with the length and radius of the cylinder, the design in-plane loads, and material properties as inputs. The effect of having axial membrane strain constraints in the skin and stiffener segments in the optimization process is also studied for selected stiffening configuration.

NASA Langley Atmospheric Science Data Center Toolsets for Airborne Data (TAD): Common Variable Naming Schema

NASA Astrophysics Data System (ADS)

Chen, G.; Early, A. B.; Peeters, M. C.

2014-12-01

NASA has conducted airborne tropospheric chemistry studies for about three decades. These field campaigns have generated a great wealth of observations, which are characterized by a wide range of trace gases and aerosol properties. The airborne observational data have often been used in assessment and validation of models and satellite instruments. One particular issue is a lack of consistent variable naming across field campaigns, which makes cross-mission data discovery difficult. The ASDC Toolset for Airborne Data (TAD) is being designed to meet the user community needs for manipulating aircraft data for scientific research on climate change and air quality relevant issues. As part of this effort, a common naming system was developed to provide a link between variables from different aircraft field studies. This system covers all current and past airborne in-situ measurements housed at the ASDC, as well as select NOAA missions. The TAD common variable naming system consists of 6 categories and 3 sub-levels. The top-level category is primarily defined by the physical characteristics of the measurement: e.g., aerosol, cloud, trace gases. The sub-levels were designed to organize the variables according to nature of measurement (e.g., aerosol microphysical and optical properties) or chemical structures (e.g., carbon compound). The development of the TAD common variable naming system was in consultation with staff from the Global Change Master Directory (GCMD) and referenced/expanded the existing Climate and Forecast (CF) variable naming conventions. The detailed structure of the TAD common variable naming convention and its application in TAD development will be presented.

Development of variable LRFD \\0x03C6 factors for deep foundation design due to site variability.

DOT National Transportation Integrated Search

2012-04-01

The current design guidelines of Load and Resistance Factor Design (LRFD) specifies constant values : for deep foundation design, based on analytical method selected and degree of redundancy of the pier. : However, investigation of multiple sites in ...

Mixed oxidizer hybrid propulsion system optimization under uncertainty using applied response surface methodology and Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Whitehead, James Joshua

The analysis documented herein provides an integrated approach for the conduct of optimization under uncertainty (OUU) using Monte Carlo Simulation (MCS) techniques coupled with response surface-based methods for characterization of mixture-dependent variables. This novel methodology provides an innovative means of conducting optimization studies under uncertainty in propulsion system design. Analytic inputs are based upon empirical regression rate information obtained from design of experiments (DOE) mixture studies utilizing a mixed oxidizer hybrid rocket concept. Hybrid fuel regression rate was selected as the target response variable for optimization under uncertainty, with maximization of regression rate chosen as the driving objective. Characteristic operational conditions and propellant mixture compositions from experimental efforts conducted during previous foundational work were combined with elemental uncertainty estimates as input variables. Response surfaces for mixture-dependent variables and their associated uncertainty levels were developed using quadratic response equations incorporating single and two-factor interactions. These analysis inputs, response surface equations and associated uncertainty contributions were applied to a probabilistic MCS to develop dispersed regression rates as a function of operational and mixture input conditions within design space. Illustrative case scenarios were developed and assessed using this analytic approach including fully and partially constrained operational condition sets over all of design mixture space. In addition, optimization sets were performed across an operationally representative region in operational space and across all investigated mixture combinations. These scenarios were selected as representative examples relevant to propulsion system optimization, particularly for hybrid and solid rocket platforms. Ternary diagrams, including contour and surface plots, were developed and utilized to aid in visualization. The concept of Expanded-Durov diagrams was also adopted and adapted to this study to aid in visualization of uncertainty bounds. Regions of maximum regression rate and associated uncertainties were determined for each set of case scenarios. Application of response surface methodology coupled with probabilistic-based MCS allowed for flexible and comprehensive interrogation of mixture and operating design space during optimization cases. Analyses were also conducted to assess sensitivity of uncertainty to variations in key elemental uncertainty estimates. The methodology developed during this research provides an innovative optimization tool for future propulsion design efforts.

Exploring adaptations to climate change with stakeholders: A participatory method to design grassland-based farming systems.

PubMed

Sautier, Marion; Piquet, Mathilde; Duru, Michel; Martin-Clouaire, Roger

2017-05-15

Research is expected to produce knowledge, methods and tools to enhance stakeholders' adaptive capacity by helping them to anticipate and cope with the effects of climate change at their own level. Farmers face substantial challenges from climate change, from changes in the average temperatures and the precipitation regime to an increased variability of weather conditions and the frequency of extreme events. Such changes can have dramatic consequences for many types of agricultural production systems such as grassland-based livestock systems for which climate change influences the seasonality and productivity of fodder production. We present a participatory design method called FARMORE (FARM-Oriented REdesign) that allows farmers to design and evaluate adaptations of livestock systems to future climatic conditions. It explicitly considers three climate features in the design and evaluation processes: climate change, climate variability and the limited predictability of weather. FARMORE consists of a sequence of three workshops for which a pre-existing game-like platform was adapted. Various year-round forage production and animal feeding requirements must be assembled by participants with a computerized support system. In workshop 1, farmers aim to produce a configuration that satisfies an average future weather scenario. They refine or revise the previous configuration by considering a sample of the between-year variability of weather in workshop 2. In workshop 3, they explicitly take the limited predictability of weather into account. We present the practical aspects of the method based on four case studies involving twelve farmers from Aveyron (France), and illustrate it through an in-depth description of one of these case studies with three dairy farmers. The case studies shows and discusses how workshop sequencing (1) supports a design process that progressively accommodates complexity of real management contexts by enlarging considerations of climate change to climate variability and low weather predictability, and (2) increases the credibility and salience of the design method. Further enhancements of the method are outlined, especially the selection of pertinent weather scenarios. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of trial-to-trial variability on optimal event-related fMRI design: Implications for Beta-series correlation and multi-voxel pattern analysis

PubMed Central

Abdulrahman, Hunar; Henson, Richard N.

2016-01-01

Functional magnetic resonance imaging (fMRI) studies typically employ rapid, event-related designs for behavioral reasons and for reasons associated with statistical efficiency. Efficiency is calculated from the precision of the parameters (Betas) estimated from a General Linear Model (GLM) in which trial onsets are convolved with a Hemodynamic Response Function (HRF). However, previous calculations of efficiency have ignored likely variability in the neural response from trial to trial, for example due to attentional fluctuations, or different stimuli across trials. Here we compare three GLMs in their efficiency for estimating average and individual Betas across trials as a function of trial variability, scan noise and Stimulus Onset Asynchrony (SOA): “Least Squares All” (LSA), “Least Squares Separate” (LSS) and “Least Squares Unitary” (LSU). Estimation of responses to individual trials in particular is important for both functional connectivity using “Beta-series correlation” and “multi-voxel pattern analysis” (MVPA). Our simulations show that the ratio of trial-to-trial variability to scan noise impacts both the optimal SOA and optimal GLM, especially for short SOAs < 5 s: LSA is better when this ratio is high, whereas LSS and LSU are better when the ratio is low. For MVPA, the consistency across voxels of trial variability and of scan noise is also critical. These findings not only have important implications for design of experiments using Beta-series regression and MVPA, but also statistical parametric mapping studies that seek only efficient estimation of the mean response across trials. PMID:26549299

Relationship between tolerance/intolerance of ambiguity and perceived environmental uncertainty in hospitals.

PubMed

Callahan, P; Young-Cureton, G; Zalar, M; Wahl, S

1997-11-01

1 Many variables may contribute to a nurse's perceptions when working in a changing health care environment, especially in the field of psychiatry. 2 While this study did not find a relationship between tolerance for ambiguity and perceived environmental uncertainty in hospitals, age and educational background appear to be variable, which may warrant further study as ultimately impacting nursing. 3 Research which explores those personality variables which underlie perception would assist nurse administrators in designing interventions, opening new lines of communication, and increasing sensitivity to individual nurse's need in these changing times.

Safety performance functions incorporating design consistency variables.

PubMed

Montella, Alfonso; Imbriani, Lella Liana

2015-01-01

Highway design which ensures that successive elements are coordinated in such a way as to produce harmonious and homogeneous driver performances along the road is considered consistent and safe. On the other hand, an alignment which requires drivers to handle high speed gradients and does not meet drivers' expectancy is considered inconsistent and produces higher crash frequency. To increase the usefulness and the reliability of existing safety performance functions and contribute to solve inconsistencies of existing highways as well as inconsistencies arising in the design phase, we developed safety performance functions for rural motorways that incorporate design consistency measures. Since the design consistency variables were used only for curves, two different sets of models were fitted for tangents and curves. Models for the following crash characteristics were fitted: total, single-vehicle run-off-the-road, other single vehicle, multi vehicle, daytime, nighttime, non-rainy weather, rainy weather, dry pavement, wet pavement, property damage only, slight injury, and severe injury (including fatal). The design consistency parameters in this study are based on operating speed models developed through an instrumented vehicle equipped with a GPS continuous speed tracking from a field experiment conducted on the same motorway where the safety performance functions were fitted (motorway A16 in Italy). Study results show that geometric design consistency has a significant effect on safety of rural motorways. Previous studies on the relationship between geometric design consistency and crash frequency focused on two-lane rural highways since these highways have the higher crash rates and are generally characterized by considerable inconsistencies. Our study clearly highlights that the achievement of proper geometric design consistency is a key design element also on motorways because of the safety consequences of design inconsistencies. The design consistency measures which are significant explanatory variables of the safety performance functions developed in this study are: (1) consistency in driving dynamics, i.e., difference between side friction assumed with respect to the design speed and side friction demanded at the 85th percentile speed; (2) operating speed consistency, i.e., absolute value of the 85th percentile speed reduction through successive elements of the road; (3) inertial speed consistency, i.e., difference between the operating speed in the curve and the average operating speed along the 5 km preceding the beginning of the curve; and (4) length of tangent preceding the curve (only for run-off-the-road crashes). Copyright © 2014 Elsevier Ltd. All rights reserved.

Applications of Human Factors in Space

NASA Technical Reports Server (NTRS)

Rajulu, Sudhakar; Margerum, Sarah

2008-01-01

The main question for human factors practitioners is to determine if the user population can be accommodated within a design. Given the wide range of variables feeding into a design, just one of which is human factors, oftentimes designers will have restrictions that may potentially impact the level of accommodation. This paper focuses on two case studies where there have been impacts at the design level that may be detrimental to the ability of the design to meet certain criteria. The studies use novel approaches to determine what, if any, changes in population accommodation levels have occurred and what factors are important when manipulating the design in the future. The results of these studies provide a backbone for future analyses when working with design considerations.

Experimental Designs and Psychometric Techniques for the Study of Ride Quality

DOT National Transportation Integrated Search

1977-05-01

A major variable in both the cost of any new transportation system and rider acceptance of the system is the ride quality of its vehicles. At this time, there exists no set of objective criteria which would allow the transportation system designer to...

EVALUATION OF AN ADVANCED ENGINEERING TEST REACTOR DESIGN

DOE Office of Scientific and Technical Information (OSTI.GOV)

McVey, M.; Bradfute, J.O.; Buck, K.E.

1958-07-15

The scope of the study was primarily concerned with optimization of the geometrical and core-composition variables to achieve maximum flux in the loop region per unit core power without exceeding heat transfer and other engineering limitations. Centain other design questions are to be investigated. (A.C.)

A new design approach based on differential evolution algorithm for geometric optimization of magnetorheological brakes

NASA Astrophysics Data System (ADS)

Le-Duc, Thang; Ho-Huu, Vinh; Nguyen-Thoi, Trung; Nguyen-Quoc, Hung

2016-12-01

In recent years, various types of magnetorheological brakes (MRBs) have been proposed and optimized by different optimization algorithms that are integrated in commercial software such as ANSYS and Comsol Multiphysics. However, many of these optimization algorithms often possess some noteworthy shortcomings such as the trap of solutions at local extremes, or the limited number of design variables or the difficulty of dealing with discrete design variables. Thus, to overcome these limitations and develop an efficient computation tool for optimal design of the MRBs, an optimization procedure that combines differential evolution (DE), a gradient-free global optimization method with finite element analysis (FEA) is proposed in this paper. The proposed approach is then applied to the optimal design of MRBs with different configurations including conventional MRBs and MRBs with coils placed on the side housings. Moreover, to approach a real-life design, some necessary design variables of MRBs are considered as discrete variables in the optimization process. The obtained optimal design results are compared with those of available optimal designs in the literature. The results reveal that the proposed method outperforms some traditional approaches.

Affected States Soft Independent Modeling by Class Analogy from the Relation Between Independent Variables, Number of Independent Variables and Sample Size

PubMed Central

Kanık, Emine Arzu; Temel, Gülhan Orekici; Erdoğan, Semra; Kaya, İrem Ersöz

2013-01-01

Objective: The aim of study is to introduce method of Soft Independent Modeling of Class Analogy (SIMCA), and to express whether the method is affected from the number of independent variables, the relationship between variables and sample size. Study Design: Simulation study. Material and Methods: SIMCA model is performed in two stages. In order to determine whether the method is influenced by the number of independent variables, the relationship between variables and sample size, simulations were done. Conditions in which sample sizes in both groups are equal, and where there are 30, 100 and 1000 samples; where the number of variables is 2, 3, 5, 10, 50 and 100; moreover where the relationship between variables are quite high, in medium level and quite low were mentioned. Results: Average classification accuracy of simulation results which were carried out 1000 times for each possible condition of trial plan were given as tables. Conclusion: It is seen that diagnostic accuracy results increase as the number of independent variables increase. SIMCA method is a method in which the relationship between variables are quite high, the number of independent variables are many in number and where there are outlier values in the data that can be used in conditions having outlier values. PMID:25207065

Development of an integrated digital hand grip dynamometer and norm of hand grip strength.

PubMed

Chang, Ho; Chen, Chih-Hao; Huang, Tung-Sun; Tai, Chun-Yen

2015-01-01

This study designs and fabricates a novel integrated digital hand grip dynamometer and analyzes collected grip strength data. The dynamometer directly stores collected data in a computer, unlike those on the market that cannot directly store information. A strain gauge load cell is used as a force sensor. The dynamometer is designed to maximize ergonomics. Excitation voltage of the load cell is 5 V, and a 9 V battery supplies power to its circuit. The signal receiver is National Instruments (NI) data acquisition (DAQ) card that transmits signals to the computer. The operation system is designed using LabView. This study assesses the correlation between variables of collected data. The correlation coefficients for height, weight and palm length were 0.793, 0.609 and 0.715, respectively, indicating that variables were moderately to strongly correlate with grip strength.

Parallel Calculation of Sensitivity Derivatives for Aircraft Design using Automatic Differentiation

NASA Technical Reports Server (NTRS)

Bischof, c. H.; Green, L. L.; Haigler, K. J.; Knauff, T. L., Jr.

1994-01-01

Sensitivity derivative (SD) calculation via automatic differentiation (AD) typical of that required for the aerodynamic design of a transport-type aircraft is considered. Two ways of computing SD via code generated by the ADIFOR automatic differentiation tool are compared for efficiency and applicability to problems involving large numbers of design variables. A vector implementation on a Cray Y-MP computer is compared with a coarse-grained parallel implementation on an IBM SP1 computer, employing a Fortran M wrapper. The SD are computed for a swept transport wing in turbulent, transonic flow; the number of geometric design variables varies from 1 to 60 with coupling between a wing grid generation program and a state-of-the-art, 3-D computational fluid dynamics program, both augmented for derivative computation via AD. For a small number of design variables, the Cray Y-MP implementation is much faster. As the number of design variables grows, however, the IBM SP1 becomes an attractive alternative in terms of compute speed, job turnaround time, and total memory available for solutions with large numbers of design variables. The coarse-grained parallel implementation also can be moved easily to a network of workstations.

Bi-Level Integrated System Synthesis (BLISS)

NASA Technical Reports Server (NTRS)

Sobieszczanski-Sobieski, Jaroslaw; Agte, Jeremy S.; Sandusky, Robert R., Jr.

1998-01-01

BLISS is a method for optimization of engineering systems by decomposition. It separates the system level optimization, having a relatively small number of design variables, from the potentially numerous subsystem optimizations that may each have a large number of local design variables. The subsystem optimizations are autonomous and may be conducted concurrently. Subsystem and system optimizations alternate, linked by sensitivity data, producing a design improvement in each iteration. Starting from a best guess initial design, the method improves that design in iterative cycles, each cycle comprised of two steps. In step one, the system level variables are frozen and the improvement is achieved by separate, concurrent, and autonomous optimizations in the local variable subdomains. In step two, further improvement is sought in the space of the system level variables. Optimum sensitivity data link the second step to the first. The method prototype was implemented using MATLAB and iSIGHT programming software and tested on a simplified, conceptual level supersonic business jet design, and a detailed design of an electronic device. Satisfactory convergence and favorable agreement with the benchmark results were observed. Modularity of the method is intended to fit the human organization and map well on the computing technology of concurrent processing.

The Relationship of Field Dependent/Independent Cognitive Styles, Stimuli Variability and Time Factor on Student Achievement.

ERIC Educational Resources Information Center

Atang, Christopher I.

The effects of black and white and color illustrations on student achievement were studied to investigate the relationships between cognitive styles and instructional design. Field dependence (FD) and field independence (FI) were chosen as the cognitive style variables. Subjects were 85 freshman students in the Iowa State University Psychology…

Relationships among Reading Performance, Locus of Control and Achievement for Marginal Admission Students.

ERIC Educational Resources Information Center

Pepper, Roger S.; Drexler, John A., Jr.

The first phase of the study was a 2 x 2 factorial design, with locus of control and instructional method (lecture and demonstration) as independent variables and honor point average (HPA) as the dependent variable. The second phase used correlational techniques to test the extent to which reading performance and traditional predictors of…

External insulation systems for cryogenic storage systems. Volume 1: Optical properties of Kapton and report of process variable study

NASA Technical Reports Server (NTRS)

Frank, A. M.

1974-01-01

Investigations are conducted into the optical properties of the glass and Kapton substrate materials, and three variables were chosen: deposition rate, sputter gas pressure, and film contamination time. Substrate tests have shown that fabrication of an dielectric broadband reflector would require an extremely complex and expensive filter design.

The Effect of Supportive Organizational Leadership, Organizational Socialization, and Satisfaction with Supervision on Turnover as Mediated by Organizational Commitment and Job Satisfaction in Faculty

ERIC Educational Resources Information Center

Lowhorn, Greg L.

2009-01-01

This study utilized a predictive, multivariate research design to test the relationship between three independent variables--supportive organizational leadership, organizational socialization, and satisfaction with supervision--and the dependent variable--turnover intent--as mediated by organizational commitment and job satisfaction. The…

Item Structural Properties as Predictors of Item Difficulty and Item Association.

ERIC Educational Resources Information Center

Solano-Flores, Guillermo

1993-01-01

Studied the ability of logical test design (LTD) to predict student performance in reading Roman numerals for 211 sixth graders in Mexico City tested on Roman numeral items varying on LTD-related and non-LTD-related variables. The LTD-related variable item iterativity was found to be the best predictor of item difficulty. (SLD)

Polychronometry: The Study of Time Variables in Behavior.

ERIC Educational Resources Information Center

Mackey, William Francis

There is a growing need for instrumentation which can enable us to observe and compute phenomena that take place in time. Although problems of observation, computation, interpretation and categorization vary from field to field and from problem to problem, it is possible to design an instrument for use in any situation where time-variables have to…

L2 Fluency as Influenced by Content Familiarity and Planning: Performance, Measurement, and Pedagogy

ERIC Educational Resources Information Center

Bui, Gavin; Huang, Zeping

2018-01-01

This study investigates how second language (L2) fluency is influenced by two factors: Pre-task planning and content familiarity. Planning was adopted as a between-participant variable, combined with content familiarity as a within-participant variable, in a 2 × 2 split-plot factorial design. Nineteen measures of fluency phenomena, constituting…

Academic Achievement and Perceived Peer Support among Turkish Students: Gender and Preschool Education Impact

ERIC Educational Resources Information Center

Bursal, Murat

2017-01-01

This study was conducted to investigate the academic achievement and perceived peer support levels of 4th-8th grade Turkish elementary and middle school students at low socio-economic status. Factorial design analyses were used to test the statistical effects of gender and preschool education variables on the dependent variables. The findings…

Cultivating Effective Pedagogical Skills in In-Service Teachers: The Role of Some Teacher Variables

ERIC Educational Resources Information Center

Amusan, Mosunmola A.

2016-01-01

Researchers have opined that pedagogical skill of the teacher is a powerful force. This study investigated variables that are required to cultivate effective pedagogical skills for teaching basic science and technology (BST) in Ogun State Primary Schools in Nigeria. A survey research design was adopted. A total of 148 teachers across the state…

Effects of ICT Assisted Real and Virtual Learning on the Performance of Secondary School Students

ERIC Educational Resources Information Center

Deka, Monisha; Jena, Ananta Kumar

2017-01-01

The study aimed to assess the effect of ICT assisted real and virtual learning performance over the traditional approach of secondary school students. Non-Equivalent Pretest-Posttest Quasi Experimental Design used to assess and relate the effects of independent variables virtual learning on dependent variables (i.e. learning performance).…

Oral Language, Sex and Socio-Economic Status as Predictors of Reading Achievement.

ERIC Educational Resources Information Center

Ebert, Dorothy Jo Williamson

This study was designed to discover the degree of relationship between a number of predictor variables and reading achievement for 65 black second grade students in two Austin, Texas, schools. The seven predictor variables used were: oral language performance as measured by the Gloria and David Beginning English, Series 20, Test 6 (GDBE); an…

Students, Teachers, and Schools as Sources of Variability, Integrity, and Sustainability in Implementing Progress Monitoring

ERIC Educational Resources Information Center

Bolt, Daniel M.; Ysseldyke, Jim; Patterson, Michael J.

2010-01-01

A three-level variance decomposition analysis was used to examine the sources of variability in implementation of a technology-enhanced progress monitoring system within each year of a 2-year study using a randomized-controlled design. We show that results of technology-enhanced progress monitoring are not necessarily a measure of student…

The art of spacecraft design: A multidisciplinary challenge

NASA Technical Reports Server (NTRS)

Abdi, F.; Ide, H.; Levine, M.; Austel, L.

1989-01-01

Actual design turn-around time has become shorter due to the use of optimization techniques which have been introduced into the design process. It seems that what, how and when to use these optimization techniques may be the key factor for future aircraft engineering operations. Another important aspect of this technique is that complex physical phenomena can be modeled by a simple mathematical equation. The new powerful multilevel methodology reduces time-consuming analysis significantly while maintaining the coupling effects. This simultaneous analysis method stems from the implicit function theorem and system sensitivity derivatives of input variables. Use of the Taylor's series expansion and finite differencing technique for sensitivity derivatives in each discipline makes this approach unique for screening dominant variables from nondominant variables. In this study, the current Computational Fluid Dynamics (CFD) aerodynamic and sensitivity derivative/optimization techniques are applied for a simple cone-type forebody of a high-speed vehicle configuration to understand basic aerodynamic/structure interaction in a hypersonic flight condition.

Design of forging process variables under uncertainties

NASA Astrophysics Data System (ADS)

Repalle, Jalaja; Grandhi, Ramana V.

2005-02-01

Forging is a complex nonlinear process that is vulnerable to various manufacturing anomalies, such as variations in billet geometry, billet/die temperatures, material properties, and workpiece and forging equipment positional errors. A combination of these uncertainties could induce heavy manufacturing losses through premature die failure, final part geometric distortion, and reduced productivity. Identifying, quantifying, and controlling the uncertainties will reduce variability risk in a manufacturing environment, which will minimize the overall production cost. In this article, various uncertainties that affect the forging process are identified, and their cumulative effect on the forging tool life is evaluated. Because the forging process simulation is time-consuming, a response surface model is used to reduce computation time by establishing a relationship between the process performance and the critical process variables. A robust design methodology is developed by incorporating reliability-based optimization techniques to obtain sound forging components. A case study of an automotive-component forging-process design is presented to demonstrate the applicability of the method.

Output Feedback Distributed Containment Control for High-Order Nonlinear Multiagent Systems.

PubMed

Li, Yafeng; Hua, Changchun; Wu, Shuangshuang; Guan, Xinping

2017-01-31

In this paper, we study the problem of output feedback distributed containment control for a class of high-order nonlinear multiagent systems under a fixed undirected graph and a fixed directed graph, respectively. Only the output signals of the systems can be measured. The novel reduced order dynamic gain observer is constructed to estimate the unmeasured state variables of the system with the less conservative condition on nonlinear terms than traditional Lipschitz one. Via the backstepping method, output feedback distributed nonlinear controllers for the followers are designed. By means of the novel first virtual controllers, we separate the estimated state variables of different agents from each other. Consequently, the designed controllers show independence on the estimated state variables of neighbors except outputs information, and the dynamics of each agent can be greatly different, which make the design method have a wider class of applications. Finally, a numerical simulation is presented to illustrate the effectiveness of the proposed method.

Designing management strategies for carbon dioxide storage and utilization under uncertainty using inexact modelling

NASA Astrophysics Data System (ADS)

Wang, Yu; Fan, Jie; Xu, Ye; Sun, Wei; Chen, Dong

2017-06-01

Effective application of carbon capture, utilization and storage (CCUS) systems could help to alleviate the influence of climate change by reducing carbon dioxide (CO2) emissions. The research objective of this study is to develop an equilibrium chance-constrained programming model with bi-random variables (ECCP model) for supporting the CCUS management system under random circumstances. The major advantage of the ECCP model is that it tackles random variables as bi-random variables with a normal distribution, where the mean values follow a normal distribution. This could avoid irrational assumptions and oversimplifications in the process of parameter design and enrich the theory of stochastic optimization. The ECCP model is solved by an equilibrium change-constrained programming algorithm, which provides convenience for decision makers to rank the solution set using the natural order of real numbers. The ECCP model is applied to a CCUS management problem, and the solutions could be useful in helping managers to design and generate rational CO2-allocation patterns under complexities and uncertainties.

Design of a factorial experiment with randomization restrictions to assess medical device performance on vascular tissue

PubMed Central

2011-01-01

Background Energy-based surgical scalpels are designed to efficiently transect and seal blood vessels using thermal energy to promote protein denaturation and coagulation. Assessment and design improvement of ultrasonic scalpel performance relies on both in vivo and ex vivo testing. The objective of this work was to design and implement a robust, experimental test matrix with randomization restrictions and predictive statistical power, which allowed for identification of those experimental variables that may affect the quality of the seal obtained ex vivo. Methods The design of the experiment included three factors: temperature (two levels); the type of solution used to perfuse the artery during transection (three types); and artery type (two types) resulting in a total of twelve possible treatment combinations. Burst pressures of porcine carotid and renal arteries sealed ex vivo were assigned as the response variable. Results The experimental test matrix was designed and carried out as a split-plot experiment in order to assess the contributions of several variables and their interactions while accounting for randomization restrictions present in the experimental setup. The statistical software package SAS was utilized and PROC MIXED was used to account for the randomization restrictions in the split-plot design. The combination of temperature, solution, and vessel type had a statistically significant impact on seal quality. Conclusions The design and implementation of a split-plot experimental test-matrix provided a mechanism for addressing the existing technical randomization restrictions of ex vivo ultrasonic scalpel performance testing, while preserving the ability to examine the potential effects of independent factors or variables. This method for generating the experimental design and the statistical analyses of the resulting data are adaptable to a wide variety of experimental problems involving large-scale tissue-based studies of medical or experimental device efficacy and performance. PMID:21599963

Determining anthropometric variables as a tool in the preparation of furniture and designs of interior spaces: the case of children 6 to 11 years old of Vicosa, State of Minas Gerais, Brazil.

PubMed

Zanuncio, Sharinna Venturim; Mafra, Simone Caldas Tavares; Antônio, Carlos Emílio Barbosa; Filho, Jugurta Lisboa; Vidigal Guimarães, Elza Maria; da Silva, Vania Eugênia; de Souza, Amaury Paulo; Minette, Luciano José

2012-01-01

The adequacy of facilities and the individual securities in their different age groups is importance to ensure greater functionality to them, allowing full development of daily activities. For this to occur more efficiently it is necessary the use of ergonomics which can ensure more comfort and safety for end users of products and spaces. The present study aimed to measure body dimensions of a representative sample of children aged 6 to 11 years old, children of graduate and pos graduate students, faculty and staff of the Federal University of Vicosa and also residents of the city of Vicosa, State of Minas Gerais, Brazil, coming from different municipalities of State of Minas Gerais, to organize a database that will provide the furniture industry, anthropometric variables more appropriate to design products for both the leisure activities, and for the school sector. To realize this research we used the methodology proposed by the authors Panero and Zelnik, based on samples distributed in six age groups, and providing a measurement of 10 variables. By applying the methodology to the field was possible to compare the observed data, with the tables of the aforementioned authors. The main results revealed a significant variation of the 10 variables analyzed, and it is believed that this variation could lead to possible flaws in the designs of products that use the data from these authors. The completion of the study provided data on Vicosa considered more appropriate for the design of products and environments for the population of the study, considering age and region, of Brazil (State of Minas Gerais) and it is believed that the future may expand to the Brazilian population, with the progress of study of this nature.

Effects and detection of raw material variability on the performance of near-infrared calibration models for pharmaceutical products.

PubMed

Igne, Benoit; Shi, Zhenqi; Drennen, James K; Anderson, Carl A

2014-02-01

The impact of raw material variability on the prediction ability of a near-infrared calibration model was studied. Calibrations, developed from a quaternary mixture design comprising theophylline anhydrous, lactose monohydrate, microcrystalline cellulose, and soluble starch, were challenged by intentional variation of raw material properties. A design with two theophylline physical forms, three lactose particle sizes, and two starch manufacturers was created to test model robustness. Further challenges to the models were accomplished through environmental conditions. Along with full-spectrum partial least squares (PLS) modeling, variable selection by dynamic backward PLS and genetic algorithms was utilized in an effort to mitigate the effects of raw material variability. In addition to evaluating models based on their prediction statistics, prediction residuals were analyzed by analyses of variance and model diagnostics (Hotelling's T(2) and Q residuals). Full-spectrum models were significantly affected by lactose particle size. Models developed by selecting variables gave lower prediction errors and proved to be a good approach to limit the effect of changing raw material characteristics. Hotelling's T(2) and Q residuals provided valuable information that was not detectable when studying only prediction trends. Diagnostic statistics were demonstrated to be critical in the appropriate interpretation of the prediction of quality parameters. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

Experimental design and efficient parameter estimation in preclinical pharmacokinetic studies.

PubMed

Ette, E I; Howie, C A; Kelman, A W; Whiting, B

1995-05-01

Monte Carlo simulation technique used to evaluate the effect of the arrangement of concentrations on the efficiency of estimation of population pharmacokinetic parameters in the preclinical setting is described. Although the simulations were restricted to the one compartment model with intravenous bolus input, they provide the basis of discussing some structural aspects involved in designing a destructive ("quantic") preclinical population pharmacokinetic study with a fixed sample size as is usually the case in such studies. The efficiency of parameter estimation obtained with sampling strategies based on the three and four time point designs were evaluated in terms of the percent prediction error, design number, individual and joint confidence intervals coverage for parameter estimates approaches, and correlation analysis. The data sets contained random terms for both inter- and residual intra-animal variability. The results showed that the typical population parameter estimates for clearance and volume were efficiently (accurately and precisely) estimated for both designs, while interanimal variability (the only random effect parameter that could be estimated) was inefficiently (inaccurately and imprecisely) estimated with most sampling schedules of the two designs. The exact location of the third and fourth time point for the three and four time point designs, respectively, was not critical to the efficiency of overall estimation of all population parameters of the model. However, some individual population pharmacokinetic parameters were sensitive to the location of these times.

Quasi-static rotor morphing concepts for rotorcraft performance improvements

NASA Astrophysics Data System (ADS)

Mistry, Mihir

The current research is focused on two separate quasi-static rotor morphing concepts: Variable span and variable camber. Both concepts were analyzed from the perspective of the performance improvements they allow for, as well as their design requirements. The goal of this body of work is to develop a comprehensive understanding of the benefits and implementation challenges of both systems. For the case of the variable span rotor concept, the effects on aircraft performance were evaluated for a UH-60A type aircraft. The parametric analysis included the performance effects of the rotor span and rotor speed variation, both individually as well as in combination. The design space considered the effect of three different gross weights (16000 lbs, 18300 lbs and 24000 lbs), for a window of +/-11% variation of the rotor speed and a range between +17% to --16% of radius variation (about the baseline) for a range of altitudes. The results of the analysis showed that variable span rotors by themselves are capable of reducing the power requirement of the helicopter by up to 20% for high altitude and gross weight conditions. However, when combined with rotor speed variation, it was possible to reduce the overall power required by the aircraft by up to 30%. Complimentary to the performance analysis, an analytical study of actuation concepts for a variable span rotor was also conducted. This study considered the design of two active actuation systems: Hydraulic pistons and threaded rods (jackscrews), and two passive systems which employed the use of an internal spring type restraining device. For all the configurations considered, it was determined that the design requirements could not be satisfied when considering the constraints defined. The performance improvements due to a variable camber system were evaluated for a BO-105 type rotor in hover. The design space considered included three different thrust levels (4800 lbs, 5500 lbs and 6400 lbs) for a range of altitudes and seven different camber distribution schemes (with up to 10 degrees of camber). Based on the analysis it was shown that variable camber was capable of reducing power up 18% for high thrust levels at high altitudes. Furthermore, it was found that a linearly distributed camber configuration, wherein the maximum camber was at the root, showed the best power reduction. For an untwisted blade (which would be advantageous in high speed flight), introducing spanwise camber variation would result in hover performance levels comparable to a twisted blade. Furthermore, the power reductions calculated were shown to be the result of a reduction of induced power due to the shift of the blade lift inboard due to the direct lift increase as a result of camber variation. The variable camber design presented in the current study exploits the warp-twist relationship of open-section beams. To that effect, a unique actuation structure was developed and implemented in a proof-of-concept variable camber prototype which was built using an existing CH-46E blade section. This prototype was shown to be capable of producing up to 18 degrees of distributed camber with a relatively low input warping of up to 0.18 inches. The results from the specifically developed finite element model of the prototype correlated very well with experimental data. The finite element results indicated the requirement of a shear-deformable core for proper camber deformation in the presence of centrifugal and aerodynamic loads.

Quality by Design approach for studying the impact of formulation and process variables on product quality of oral disintegrating films.

PubMed

Mazumder, Sonal; Pavurala, Naresh; Manda, Prashanth; Xu, Xiaoming; Cruz, Celia N; Krishnaiah, Yellela S R

2017-07-15

The present investigation was carried out to understand the impact of formulation and process variables on the quality of oral disintegrating films (ODF) using Quality by Design (QbD) approach. Lamotrigine (LMT) was used as a model drug. Formulation variable was plasticizer to film former ratio and process variables were drying temperature, air flow rate in the drying chamber, drying time and wet coat thickness of the film. A Definitive Screening Design of Experiments (DoE) was used to identify and classify the critical formulation and process variables impacting critical quality attributes (CQA). A total of 14 laboratory-scale DoE formulations were prepared and evaluated for mechanical properties (%elongation at break, yield stress, Young's modulus, folding endurance) and other CQA (dry thickness, disintegration time, dissolution rate, moisture content, moisture uptake, drug assay and drug content uniformity). The main factors affecting mechanical properties were plasticizer to film former ratio and drying temperature. Dissolution rate was found to be sensitive to air flow rate during drying and plasticizer to film former ratio. Data were analyzed for elucidating interactions between different variables, rank ordering the critical materials attributes (CMA) and critical process parameters (CPP), and for providing a predictive model for the process. Results suggested that plasticizer to film former ratio and process controls on drying are critical to manufacture LMT ODF with the desired CQA. Published by Elsevier B.V.

Explaining Variance and Identifying Predictors of Children's Communication via a Multilevel Model of Single-Case Design Research: Brief Report

ERIC Educational Resources Information Center

Ottley, Jennifer Riggie; Ferron, John M.; Hanline, Mary Frances

2016-01-01

The purpose of this study was to explain the variability in data collected from a single-case design study and to identify predictors of communicative outcomes for children with developmental delays or disabilities (n = 4). Using SAS® University Edition, we fit multilevel models with time nested within children. Children's level of baseline…

Drag Optimization Of Light Trucks Using Computational Fluid Dynamics

DTIC Science & Technology

2003-09-01

dimensional design case 19 study on the Lockheed C-141B aircraft wing, Cosentino and Holst [Ref. 10] reduced the number of design variables from 120 to 12... case letters) 6. AUTHOR(S) 5. FUNDING NUMBERS 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Postgraduate School Monterey, CA 93943...23 B. TWO DIMENSIONAL LIGHT TRUCK SHAPE STUDIES .................. 23 1. Canopies

Scalability of surrogate-assisted multi-objective optimization of antenna structures exploiting variable-fidelity electromagnetic simulation models

NASA Astrophysics Data System (ADS)

Koziel, Slawomir; Bekasiewicz, Adrian

2016-10-01

Multi-objective optimization of antenna structures is a challenging task owing to the high computational cost of evaluating the design objectives as well as the large number of adjustable parameters. Design speed-up can be achieved by means of surrogate-based optimization techniques. In particular, a combination of variable-fidelity electromagnetic (EM) simulations, design space reduction techniques, response surface approximation models and design refinement methods permits identification of the Pareto-optimal set of designs within a reasonable timeframe. Here, a study concerning the scalability of surrogate-assisted multi-objective antenna design is carried out based on a set of benchmark problems, with the dimensionality of the design space ranging from six to 24 and a CPU cost of the EM antenna model from 10 to 20 min per simulation. Numerical results indicate that the computational overhead of the design process increases more or less quadratically with the number of adjustable geometric parameters of the antenna structure at hand, which is a promising result from the point of view of handling even more complex problems.

Design and optimisation of novel configurations of stormwater constructed wetlands

NASA Astrophysics Data System (ADS)

Kiiza, Christopher

2017-04-01

Constructed wetlands (CWs) are recognised as a cost-effective technology for wastewater treatment. CWs have been deployed and could be retrofitted into existing urban drainage systems to prevent surface water pollution, attenuate floods and act as sources for reusable water. However, there exist numerous criteria for design configuration and operation of CWs. The aim of the study was to examine effects of design and operational variables on performance of CWs. To achieve this, 8 novel designs of vertical flow CWs were continuously operated and monitored (weekly) for 2years. Pollutant removal efficiency in each CW unit was evaluated from physico-chemical analyses of influent and effluent water samples. Hybrid optimised multi-layer perceptron artificial neural networks (MLP ANNs) were applied to simulate treatment efficiency in the CWs. Subsequently, predictive and analytical models were developed for each design unit. Results show models have sound generalisation abilities; with various design configurations and operational variables influencing performance of CWs. Although some design configurations attained faster and higher removal efficiencies than others; all 8 CW designs produced effluents permissible for discharge into watercourses with strict regulatory standards.

Understanding the variable effect of instructional innovations on student learning

NASA Astrophysics Data System (ADS)

Iverson, Heidi L.

2012-02-01

As a result of dissatisfaction with the traditional lecture-based model of education a large number of reform-oriented instructional innovations have been developed, enacted, and studied in undergraduate physics courses. While previous work has shown that the impact of instructional innovations on student learning has been overwhelmingly positive, it has also been highly variable. The purpose of this analysis is to investigate this variability. For this analysis, 79 published studies on undergraduate physics instructional innovations were analyzed with respect to the types of innovations used and the methodological characteristics of the studies themselves. The findings of this analysis have indicated that nearly half of the variability in effect size can be accounted for by study design characteristics rather than by the characteristics of the innovations used. However, a subsequent analysis illustrated that one specific innovation, Workshop/Studio Physics, appears to be particularly effective within the observed sample of studies.

Optimization of a Small Scale Linear Reluctance Accelerator

NASA Astrophysics Data System (ADS)

Barrera, Thor; Beard, Robby

2011-11-01

Reluctance accelerators are extremely promising future methods of transportation. Several problems still plague these devices, most prominently low efficiency. Variables to overcoming efficiency problems are many and difficult to correlate how they affect our accelerator. The study examined several differing variables that present potential challenges in optimizing the efficiency of reluctance accelerators. These include coil and projectile design, power supplies, switching, and the elusive gradient inductance problem. Extensive research in these areas has been performed from computational and theoretical to experimental. Findings show that these parameters share significant similarity to transformer design elements, thus general findings show current optimized parameters the research suggests as a baseline for further research and design. Demonstration of these current findings will be offered at the time of presentation.

Optimization of Mineral Separator for Recovery of Total Heavy Minerals of Bay of Bengal using Central Composite Design

NASA Astrophysics Data System (ADS)

Routray, Sunita; Swain, Ranjita; Rao, Raghupatruni Bhima

2017-04-01

The present study is aimed at investigating the optimization of a mineral separator for processing of beach sand minerals of Bay of Bengal along Ganjam-Rushikulya coast. The central composite design matrix and response surface methodology were applied in designing the experiments to evaluate the interactive effects of the three most important operating variables, such as feed quantity, wash water rate and Shake amplitude of the deck. The predicted values were found to be in good agreement with the experimental values (R2 = 0.97 for grade and 0.98 for recovery). To understand the impact of each variable, three dimensional (3D) plots were also developed for the estimated responses.

Tethered gravity laboratories study

NASA Technical Reports Server (NTRS)

Lucchetti, F.

1989-01-01

Variable Gravity Laboratory studies are discussed. The following subject areas are covered: (1) conceptual design and engineering analysis; (2) control strategies (fast crawling maneuvers, main perturbations and their effect upon the acceleration level); and (3) technology requirements.

Individual determinants of research utilization: a systematic review.

PubMed

Estabrooks, Carole A; Floyd, Judith A; Scott-Findlay, Shannon; O'Leary, Katherine A; Gushta, Matthew

2003-09-01

In order to design interventions that increase research use in nursing, it is necessary to have an understanding of what influences research use. To report findings on a systematic review of studies that examine individual characteristics of nurses and how they influence the utilization of research. A survey of published articles in English that examine the influence of individual factors on the research utilization behaviour of nurses, without restriction of the study design, from selected computerized databases and hand searches. Articles had to measure one or more individual determinants of research utilization, measure the dependent variable (research utilization), and evaluate the relationship between the dependent and independent variables. The studies also had to indicate the direction of the relationship between the independent and dependent variables, report a P-value and the statistic used, and indicate the magnitude of the relationship. Six categories of potential individual determinants were identified: beliefs and attitudes, involvement in research activities, information seeking, professional characteristics, education and other socio-economic factors. Research design, sampling, measurement, and statistical analysis were examined to evaluate methodological quality. Methodological problems surfaced in all of the studies and, apart from attitude to research, there was little to suggest that any potential individual determinant influences research use. Important conceptual and measurement issues with regard to research utilization could be better addressed if research in the area were undertaken longitudinally by multi-disciplinary teams of researchers.

Development of Probabilistic Rigid Pavement Design Methodologies for Military Airfields.

DTIC Science & Technology

1983-12-01

4A161102AT22, Task AO, Work Unit 009, "Methodology for Considering Material Variability in Pavement Design." OCE Project Monitor was Mr. S. S. Gillespie. The...PREFACE. .. ............................. VOLUME 1: STATE OF THE ART VARIABILITY OF AIRFIELD PAVEMENT MATERIALS VOLUME 11: MATHEMATICAL FORMULATION OF...VOLUME IV: PROBABILISTIC ANALYSIS OF RIGID AIRFIELD DESIGN BY ELASTIC LAYERED THEORY VOLUME I STATE OF THE ART VARIABILITY OF AIRFIELD PAVEMENT MATERIALS

Multidisciplinary optimization of controlled space structures with global sensitivity equations

NASA Technical Reports Server (NTRS)

Padula, Sharon L.; James, Benjamin B.; Graves, Philip C.; Woodard, Stanley E.

1991-01-01

A new method for the preliminary design of controlled space structures is presented. The method coordinates standard finite element structural analysis, multivariable controls, and nonlinear programming codes and allows simultaneous optimization of the structures and control systems of a spacecraft. Global sensitivity equations are a key feature of this method. The preliminary design of a generic geostationary platform is used to demonstrate the multidisciplinary optimization method. Fifteen design variables are used to optimize truss member sizes and feedback gain values. The goal is to reduce the total mass of the structure and the vibration control system while satisfying constraints on vibration decay rate. Incorporating the nonnegligible mass of actuators causes an essential coupling between structural design variables and control design variables. The solution of the demonstration problem is an important step toward a comprehensive preliminary design capability for structures and control systems. Use of global sensitivity equations helps solve optimization problems that have a large number of design variables and a high degree of coupling between disciplines.

Intraindividual differences in executive functions during childhood: the role of emotions.

PubMed

Pnevmatikos, Dimitris; Trikkaliotis, Ioannis

2013-06-01

Intraindividual differences in executive functions (EFs) have been rarely investigated. In this study, we addressed the question of whether the emotional fluctuations that schoolchildren experience in their classroom settings could generate substantial intraindividual differences in their EFs and, more specifically, in the fundamental unifying component of EFs, their inhibition function. We designed an experimental research with ecological validity within the school setting where schoolchildren of three age groups (8-, 10-, and 12-year-olds) were involved. We executed three experiments. In Experiment 1, using a between-participants design, we isolated a classroom episode that, compared with the other episodes, generated significant differences in inhibitory function in a consequent Go/NoGo task. This was an episode that induced frustration after the experience of anxiety due to the uncertainty. Experiment 2, using a within-participants design, confirmed both the induced emotions from the episode and the intraindividual variability in schoolchildren's inhibition accuracy in the consequent Go/NoGo task. Experiment 3, again using a within-participants design, examined whether the same episode could generate intraindividual differences in a more demanding inhibition task, namely the anti-saccade task. The experiment confirmed the previous evidence; the episode generated high variability that in some age groups accounted for more than 1.5 standard deviations from the interindividual variability between the schoolchildren of the same age. Results showed that, regardless of their sex and the developmental progression in their inhibition with age, the variability induced within participants from the experienced frustration was very high compared with the interindividual variability of the same age group. Copyright © 2013 Elsevier Inc. All rights reserved.

Bioresearch module design definition and space shuttle vehicle integration study. Volume 2: Appendices

NASA Technical Reports Server (NTRS)

Lang, A. L., Jr.

1971-01-01

Data presented in the appendices covers: (1) summary description of baseline power system; (2) revised thermal profile analysis; (3) design analysis of television monitor; (4) bioresearch module ground station support evaluation; (5) variable spin control analysis; and (6) bioresearch modules and work flow.

Factors Affecting the Acceptability of Microforms as a Reading Medium.

ERIC Educational Resources Information Center

Spencer, Herbert; Reynolds, Linda

Based on visits to representative microform users and an extensive survey of relevant literature, a study was undertaken to assess the relative importance of factors affecting the acceptability of microforms as reading mediums. The following variables were considered: (1) microform characteristics; (2) equipment design; (3) work station design;…

Photography To Enhance Aesthetic Skills.

ERIC Educational Resources Information Center

McIsaac, Marina Stock

Recognizing that photography in the classroom is highly motivating in that it offers a unique vehicle for communicating ideas visually, this study was designed to isolate variables which can be both observed and evaluated in photographs and for which instruction can be designed. Relationships among the technical and aesthetic qualities in…

Explaining Relationships among Student Outcomes and the School's Physical Environment

ERIC Educational Resources Information Center

Tanner, C. Kenneth

2008-01-01

This descriptive study investigated the possible effects of selected school design patterns on third-grade students' academic achievement. A reduced regression analysis revealed the effects of school design components (patterns) on ITBS achievement data, after including control variables, for a sample of third-grade students drawn from 24…

A Robust Adaptive Autonomous Approach to Optimal Experimental Design

NASA Astrophysics Data System (ADS)

Gu, Hairong

Experimentation is the fundamental tool of scientific inquiries to understand the laws governing the nature and human behaviors. Many complex real-world experimental scenarios, particularly in quest of prediction accuracy, often encounter difficulties to conduct experiments using an existing experimental procedure for the following two reasons. First, the existing experimental procedures require a parametric model to serve as the proxy of the latent data structure or data-generating mechanism at the beginning of an experiment. However, for those experimental scenarios of concern, a sound model is often unavailable before an experiment. Second, those experimental scenarios usually contain a large number of design variables, which potentially leads to a lengthy and costly data collection cycle. Incompetently, the existing experimental procedures are unable to optimize large-scale experiments so as to minimize the experimental length and cost. Facing the two challenges in those experimental scenarios, the aim of the present study is to develop a new experimental procedure that allows an experiment to be conducted without the assumption of a parametric model while still achieving satisfactory prediction, and performs optimization of experimental designs to improve the efficiency of an experiment. The new experimental procedure developed in the present study is named robust adaptive autonomous system (RAAS). RAAS is a procedure for sequential experiments composed of multiple experimental trials, which performs function estimation, variable selection, reverse prediction and design optimization on each trial. Directly addressing the challenges in those experimental scenarios of concern, function estimation and variable selection are performed by data-driven modeling methods to generate a predictive model from data collected during the course of an experiment, thus exempting the requirement of a parametric model at the beginning of an experiment; design optimization is performed to select experimental designs on the fly of an experiment based on their usefulness so that fewest designs are needed to reach useful inferential conclusions. Technically, function estimation is realized by Bayesian P-splines, variable selection is realized by Bayesian spike-and-slab prior, reverse prediction is realized by grid-search and design optimization is realized by the concepts of active learning. The present study demonstrated that RAAS achieves statistical robustness by making accurate predictions without the assumption of a parametric model serving as the proxy of latent data structure while the existing procedures can draw poor statistical inferences if a misspecified model is assumed; RAAS also achieves inferential efficiency by taking fewer designs to acquire useful statistical inferences than non-optimal procedures. Thus, RAAS is expected to be a principled solution to real-world experimental scenarios pursuing robust prediction and efficient experimentation.

Application of variable-gain output feedback for high-alpha control

NASA Technical Reports Server (NTRS)

Ostroff, Aaron J.

1990-01-01

A variable-gain, optimal, discrete, output feedback design approach that is applied to a nonlinear flight regime is described. The flight regime covers a wide angle-of-attack range that includes stall and post stall. The paper includes brief descriptions of the variable-gain formulation, the discrete-control structure and flight equations used to apply the design approach, and the high performance airplane model used in the application. Both linear and nonlinear analysis are shown for a longitudinal four-model design case with angles of attack of 5, 15, 35, and 60 deg. Linear and nonlinear simulations are compared for a single-point longitudinal design at 60 deg angle of attack. Nonlinear simulations for the four-model, multi-mode, variable-gain design include a longitudinal pitch-up and pitch-down maneuver and high angle-of-attack regulation during a lateral maneuver.

Message Variability and Heterogeneity: A Core Challenge for Communication Research

PubMed Central

Slater, Michael D.; Peter, Jochen; Valkenberg, Patti

2015-01-01

Messages are central to human social experience, and pose key conceptual and methodological challenges in the study of communication. In response to these challenges, we outline a systematic approach to conceptualizing, operationalizing, and analyzing messages. At the conceptual level, we distinguish between two core aspects of messages: message variability (the defined and operationalized features of messages) and message heterogeneity (the undefined and unmeasured features of messages), and suggest preferred approaches to defining message variables. At the operational level, we identify message sampling, selection, and research design strategies responsive to issues of message variability and heterogeneity in experimental and survey research. At the analytical level, we highlight effective techniques to deal with message variability and heterogeneity. We conclude with seven recommendations to increase rigor in the study of communication through appropriately addressing the challenges presented by messages. PMID:26681816

Multi-stability and variable stiffness of cellular solids designed based on origami patterns

NASA Astrophysics Data System (ADS)

Sengupta, Sattam; Li, Suyi

2017-04-01

The application of origami-inspired designs to engineered structures and materials has been a subject of much research efforts. These structures and materials, whose mechanical properties are directly related to the geometry of folding, are capable of achieving a host of unique adaptive functions. In this study, we investigate a three-dimensional multistability and variable stiffness function of a cellular solid based on the Miura-Ori folding pattern. The unit cell of such a solid, consisting of two stacked Miura-Ori sheets, can be elastically bistable due to the nonlinear relationship between rigid-folding deformation and crease material bending. Such a bistability possesses an unorthodox property: the critical, unstable configuration lies on the same side of two stable ones, so that two different force-deformation curves co-exist within the same range of deformation. By exploiting such unique stability properties, we can achieve a programmable stiffness change between the two elastically stable states, and the stiffness differences can be prescribed by tailoring the crease patterns of the cell. This paper presents a comprehensive parametric study revealing the correlations between such variable stiffness and various design parameters. The unique properties stemming from the bistability and design of such a unit cell can be advanced further by assembling them into a solid which can be capable of shape morphing and programmable mechanical properties.

The role of anthropometry in designing for sustainability.

PubMed

Nadadur, Gopal; Parkinson, Matthew B

2013-01-01

An understanding of human factors and ergonomics facilitates the design of artefacts, tasks and environments that fulfil their users' physical and cognitive requirements. Research in these fields furthers the goal of efficiently accommodating the desired percentage of user populations through enhanced awareness and modelling of human variability. Design for sustainability (DfS) allows for these concepts to be leveraged in the broader context of designing to minimise negative impacts on the environment. This paper focuses on anthropometry and proposes three ways in which its consideration is relevant to DfS: reducing raw material consumption, increasing usage lifetimes and ethical human resource considerations. This is demonstrated through the application of anthropometry synthesis, virtual fitting, and sizing and adjustability allocation methods in the design of an industrial workstation seat for use in five distinct global populations. This work highlights the importance of and opportunities for using ergonomic design principles in DfS efforts. This research demonstrates the relevance of some anthropometry-based ergonomics concepts to the field of design for sustainability. A global design case study leverages human variability considerations in furthering three sustainable design goals: reducing raw material consumption, increasing usage lifetimes and incorporating ethical human resource considerations in design.

Design of helicopter rotors to noise constraints

NASA Technical Reports Server (NTRS)

Schaeffer, E. G.; Sternfeld, H., Jr.

1978-01-01

Results of the initial phase of a research project to study the design constraints on helicopter noise are presented. These include the calculation of nonimpulsive rotor harmonic and broadband hover noise spectra, over a wide range of rotor design variables and the sensitivity of perceived noise level (PNL) to changes in rotor design parameters. The prediction methodology used correlated well with measured whirl tower data. Application of the predictions to variations in rotor design showed tip speed and thrust as having the most effect on changing PNL.

Task-Driven Evaluation of Aggregation in Time Series Visualization

PubMed Central

Albers, Danielle; Correll, Michael; Gleicher, Michael

2014-01-01

Many visualization tasks require the viewer to make judgments about aggregate properties of data. Recent work has shown that viewers can perform such tasks effectively, for example to efficiently compare the maximums or means over ranges of data. However, this work also shows that such effectiveness depends on the designs of the displays. In this paper, we explore this relationship between aggregation task and visualization design to provide guidance on matching tasks with designs. We combine prior results from perceptual science and graphical perception to suggest a set of design variables that influence performance on various aggregate comparison tasks. We describe how choices in these variables can lead to designs that are matched to particular tasks. We use these variables to assess a set of eight different designs, predicting how they will support a set of six aggregate time series comparison tasks. A crowd-sourced evaluation confirms these predictions. These results not only provide evidence for how the specific visualizations support various tasks, but also suggest using the identified design variables as a tool for designing visualizations well suited for various types of tasks. PMID:25343147

Accounting for patient variability in finite element analysis of the intact and implanted hip and knee: a review.

PubMed

Taylor, Mark; Bryan, Rebecca; Galloway, Francis

2013-02-01

It is becoming increasingly difficult to differentiate the performance of new joint replacement designs using available preclinical test methods. Finite element analysis is commonly used and the majority of published studies are performed on representative anatomy, assuming optimal implant placement, subjected to idealised loading conditions. There are significant differences between patients and accounting for this variability will lead to better assessment of the risk of failure. This review paper provides a comprehensive overview of the techniques available to account for patient variability. There is a brief overview of patient-specific model generation techniques, followed by a review of multisubject patient-specific studies performed on the intact and implanted femur and tibia. In particular, the challenges and limitations of manually generating models for such studies are discussed. To efficiently account for patient variability, the application of statistical shape and intensity models (SSIM) are being developed. Such models have the potential to synthetically generate thousands of representative models generated from a much smaller training set. Combined with the automation of the prosthesis implantation process, SSIM provides a potentially powerful tool for assessing the next generation of implant designs. The potential application of SSIM are discussed along with their limitations. Copyright © 2012 John Wiley & Sons, Ltd.

Evidence-based design recommendations for prevalence studies on multimorbidity: improving comparability of estimates.

PubMed

Holzer, Barbara M; Siebenhuener, Klarissa; Bopp, Matthias; Minder, Christoph E

2017-03-07

In aging populations, multimorbidity causes a disease burden of growing importance and cost. However, estimates of the prevalence of multimorbidity (prevMM) vary widely across studies, impeding valid comparisons and interpretation of differences. With this study we pursued two research objectives: (1) to identify a set of study design and demographic factors related to prevMM, and (2) based on (1), to formulate design recommendations for future studies with improved comparability of prevalence estimates. Study data were obtained through systematic review of the literature. UsingPubMed/MEDLINE, Embase, CINAHL, Web of Science, BIOSIS, and Google Scholar, we looked for articles with the terms "multimorbidity," "comorbidity," "polymorbidity," and variations of these published in English or German in the years 1990 to 2011. We selected quantitative studies of the prevalence of multimorbidity (two or more chronic medical conditions) with a minimum sample size of 50 and a study population with a majority of Caucasians. Our database consisted of prevalence estimates in 108 age groups taken from 45 studies. To assess the effects of study design variables, we used meta regression models. In 58% of the studies, there was only one age group, i.e., no stratification by age. The number of persons per age group ranged from 136 to 5.6 million. Our analyses identified the following variables as highly significant: "mean age," "number of age groups", and "data reporting quality" (all p < 0.0001). "Setting," "disease classification," and "number of diseases in the classification" were significant (0.01 < p ≤ 0.03), and "data collection period" and "data source" were non-significant. A separate analysis showed that prevMM was significantly higher in women than men (sign test, p = 0.0015). Comparable prevalence estimates are urgently needed for realistic description of the magnitude of the problem of multimorbidity. Based on the results of our analyses of variables affecting prevMM, we make some design recommendations. Our suggestions were guided by a pragmatic approach and aimed at facilitating the implementation of a uniform methodology. This should aid progress towards a more uniform operationalization of multimorbidity.

Evaluating the case-positive, control test-negative study design for influenza vaccine effectiveness for the frailty bias.

PubMed

Talbot, H Keipp; Nian, Hui; Chen, Qingxia; Zhu, Yuwei; Edwards, Kathryn M; Griffin, Marie R

2016-04-04

Previous influenza vaccine effectiveness studies were criticized for their failure to control for frailty. This study was designed to see if the test-negative study design overcomes this bias. Adults ≥ 50 years of age with respiratory symptoms were enrolled from November 2006 through May 2012 during the influenza season (excluding the 2009-2010 H1N1 pandemic season) to perform yearly test-negative control influenza vaccine effectiveness studies in Nashville, TN. At enrollment, both a nasal and throat swab sample were obtained and tested for influenza by RT-PCR. Frailty was calculated using a modified Rockwood Index that included 60 variables ascertained in a retrospective chart review giving a score of 0 to 1. Subjects were divided into three strata: non frail (≤ 0.08), pre-frail (> 0.08 to < 0.25), and frail (≥ 0.25). Vaccine effectiveness was calculated using the formula [1-adjusted odds ratio (OR)] × 100%. Adjusted ORs for individual years and all years combined were estimated by penalized multivariable logistic regression. Of 1023 hospitalized adults enrolled, 866 (84.7%) participants had complete immunization status, molecular influenza testing and covariates to calculate frailty. There were 83 influenza-positive cases and 783 test-negative controls overall, who were 74% white, 25% black, and 59% female. The median frailty index was 0.167 (Interquartile: 0.117, 0.267). The frailty index was 0.167 (0.100, 0.233) for the influenza positive cases compared to 0.183 (0.133, 0.267) for influenza negative controls (p = 0.07). Vaccine effectiveness estimates were 55.2% (95%CI: 30.5, 74.2), 60.4% (95%CI: 29.5, 74.4), and 54.3% (95%CI: 28.8, 74.0) without the frailty variable, including frailty as a continuous variable, and including frailty as a categorical variable, respectively. Using the case positive test negative study design to assess vaccine effectiveness, our measure of frailty was not a significant confounder as inclusion of this measure did not significantly change vaccine effectiveness estimates. Copyright © 2016 Elsevier Ltd. All rights reserved.

Optical design of laser zoom projective lens with variable total track

NASA Astrophysics Data System (ADS)

He, Yulan; Xiao, Xiangguo; Lu, Feng; Li, Yuan; Han, Kunye; Wang, Nanxi; Qiang, Hua

2017-02-01

In order to project the laser command information to the proper distance , so a laser zoom projective lens with variable total track optical system is designed in the carrier-based aircraft landing system. By choosing the zoom structure, designing of initial structure with PW solution, correcting and balancing the aberration, a large variable total track with 35 × zoom is carried out. The size of image is invariable that is φ25m, the distance of projective image is variable from 100m to 3500m. Optical reverse design, the spot is less than 8μm, the MTF is near the diffraction limitation, the value of MTF is bigger than 0.4 at 50lp/mm.

Design simplicity influences patient portal use: the role of aesthetic evaluations for technology acceptance

PubMed Central

Watkins, Ivan; Mackert, Michael S; Xie, Bo; Stephens, Keri K; Shalev, Heidi

2016-01-01

Objective This study focused on patient portal use and investigated whether aesthetic evaluations of patient portals function are antecedent variables to variables in the Technology Acceptance Model. Methods A cross-sectional survey of current patient portals users (N = 333) was conducted online. Participants completed the Visual Aesthetics of Website Inventory, along with items measuring perceived ease of use (PEU), perceived usefulness (PU), and behavioral intentions (BIs) to use the patient portal. Results The hypothesized model accounted for 29% of the variance in BIs to use the portal, 46% of the variance in the PU of the portal, and 29% of the variance in the portal’s PEU. Additionally, one dimension of the aesthetic evaluations functions as a predictor in the model – simplicity evaluations had a significant positive effect on PEU. Conclusion This study provides evidence that aesthetic evaluations – specifically regarding simplicity – function as a significant antecedent variable to patients’ use of patient portals and should influence patient portal design strategies. PMID:26635314

Effects of Immediate Feedback and Pacing of Item Presentation on Ability Test Performance and Psychological Reactions to Testing.

DTIC Science & Technology

1981-02-01

3 Design ..................................................................... 3 Independent Variables...Prestwood & Weiss, 1978), which were designed to assess the effects of KR, the provision of "KR wa ; onf.,tidod with paring of item presentation...ach Item. -3- The present study was designed to separately examine the effects of KR and of computer- versus self-pacing of item presentation in order

Parametric Studies of Flow Separation using Air Injection

NASA Technical Reports Server (NTRS)

Zhang, Wei

2004-01-01

Boundary Layer separation causes the airfoil to stall and therefore imposes dramatic performance degradation on the airfoil. In recent years, flow separation control has been one of the active research areas in the field of aerodynamics due to its promising performance improvements on the lifting device. These active flow separation control techniques include steady and unsteady air injection as well as suction on the airfoil surface etc. This paper will be focusing on the steady and unsteady air injection on the airfoil. Although wind tunnel experiments revealed that the performance improvements on the airfoil using injection techniques, the details of how the key variables such as air injection slot geometry and air injection angle etc impact the effectiveness of flow separation control via air injection has not been studied. A parametric study of both steady and unsteady air injection active flow control will be the main objective for this summer. For steady injection, the key variables include the slot geometry, orientation, spacing, air injection velocity as well as the injection angle. For unsteady injection, the injection frequency will also be investigated. Key metrics such as lift coefficient, drag coefficient, total pressure loss and total injection mass will be used to measure the effectiveness of the control technique. A design of experiments using the Box-Behnken Design is set up in order to determine how each of the variables affects each of the key metrics. Design of experiment is used so that the number of experimental runs will be at minimum and still be able to predict which variables are the key contributors to the responses. The experiments will then be conducted in the 1ft by 1ft wind tunnel according to the design of experiment settings. The data obtained from the experiments will be imported into JMP, statistical software, to generate sets of response surface equations which represent the statistical empirical model for each of the metrics as a function of the key variables. Next, the variables such as the slot geometry can be optimized using the build-in optimizer within JMP. Finally, a wind tunnel testing will be conducted using the optimized slot geometry and other key variables to verify the empirical statistical model. The long term goal for this effort is to assess the impacts of active flow control using air injection at system level as one of the task plan included in the NASAs URETI program with Georgia Institute of Technology.

A Bayesian approach to the statistical analysis of device preference studies.

PubMed

Fu, Haoda; Qu, Yongming; Zhu, Baojin; Huster, William

2012-01-01

Drug delivery devices are required to have excellent technical specifications to deliver drugs accurately, and in addition, the devices should provide a satisfactory experience to patients because this can have a direct effect on drug compliance. To compare patients' experience with two devices, cross-over studies with patient-reported outcomes (PRO) as response variables are often used. Because of the strength of cross-over designs, each subject can directly compare the two devices by using the PRO variables, and variables indicating preference (preferring A, preferring B, or no preference) can be easily derived. Traditionally, methods based on frequentist statistics can be used to analyze such preference data, but there are some limitations for the frequentist methods. Recently, Bayesian methods are considered an acceptable method by the US Food and Drug Administration to design and analyze device studies. In this paper, we propose a Bayesian statistical method to analyze the data from preference trials. We demonstrate that the new Bayesian estimator enjoys some optimal properties versus the frequentist estimator. Copyright © 2012 John Wiley & Sons, Ltd.

Multivariate hydrological frequency analysis for extreme events using Archimedean copula. Case study: Lower Tunjuelo River basin (Colombia)

NASA Astrophysics Data System (ADS)

Gómez, Wilmar

2017-04-01

By analyzing the spatial and temporal variability of extreme precipitation events we can prevent or reduce the threat and risk. Many water resources projects require joint probability distributions of random variables such as precipitation intensity and duration, which can not be independent with each other. The problem of defining a probability model for observations of several dependent variables is greatly simplified by the joint distribution in terms of their marginal by taking copulas. This document presents a general framework set frequency analysis bivariate and multivariate using Archimedean copulas for extreme events of hydroclimatological nature such as severe storms. This analysis was conducted in the lower Tunjuelo River basin in Colombia for precipitation events. The results obtained show that for a joint study of the intensity-duration-frequency, IDF curves can be obtained through copulas and thus establish more accurate and reliable information from design storms and associated risks. It shows how the use of copulas greatly simplifies the study of multivariate distributions that introduce the concept of joint return period used to represent the needs of hydrological designs properly in frequency analysis.

Analysis of Genome-Wide Association Studies with Multiple Outcomes Using Penalization

PubMed Central

Liu, Jin; Huang, Jian; Ma, Shuangge

2012-01-01

Genome-wide association studies have been extensively conducted, searching for markers for biologically meaningful outcomes and phenotypes. Penalization methods have been adopted in the analysis of the joint effects of a large number of SNPs (single nucleotide polymorphisms) and marker identification. This study is partly motivated by the analysis of heterogeneous stock mice dataset, in which multiple correlated phenotypes and a large number of SNPs are available. Existing penalization methods designed to analyze a single response variable cannot accommodate the correlation among multiple response variables. With multiple response variables sharing the same set of markers, joint modeling is first employed to accommodate the correlation. The group Lasso approach is adopted to select markers associated with all the outcome variables. An efficient computational algorithm is developed. Simulation study and analysis of the heterogeneous stock mice dataset show that the proposed method can outperform existing penalization methods. PMID:23272092

Variables affecting learning in a simulation experience: a mixed methods study.

PubMed

Beischel, Kelly P

2013-02-01

The primary purpose of this study was to test a hypothesized model describing the direct effects of learning variables on anxiety and cognitive learning outcomes in a high-fidelity simulation (HFS) experience. The secondary purpose was to explain and explore student perceptions concerning the qualities and context of HFS affecting anxiety and learning. This study used a mixed methods quantitative-dominant explanatory design with concurrent qualitative data collection to examine variables affecting learning in undergraduate, beginning nursing students (N = 124). Being ready to learn, having a strong auditory-verbal learning style, and being prepared for simulation directly affected anxiety, whereas learning outcomes were directly affected by having strong auditory-verbal and hands-on learning styles. Anxiety did not quantitatively mediate cognitive learning outcomes as theorized, although students qualitatively reported debilitating levels of anxiety. This study advances nursing education science by providing evidence concerning variables affecting learning outcomes in HFS.

Sensitivity of Space Station alpha joint robust controller to structural modal parameter variations

NASA Technical Reports Server (NTRS)

Kumar, Renjith R.; Cooper, Paul A.; Lim, Tae W.

1991-01-01

The photovoltaic array sun tracking control system of Space Station Freedom is described. A synthesis procedure for determining optimized values of the design variables of the control system is developed using a constrained optimization technique. The synthesis is performed to provide a given level of stability margin, to achieve the most responsive tracking performance, and to meet other design requirements. Performance of the baseline design, which is synthesized using predicted structural characteristics, is discussed and the sensitivity of the stability margin is examined for variations of the frequencies, mode shapes and damping ratios of dominant structural modes. The design provides enough robustness to tolerate a sizeable error in the predicted modal parameters. A study was made of the sensitivity of performance indicators as the modal parameters of the dominant modes vary. The design variables are resynthesized for varying modal parameters in order to achieve the most responsive tracking performance while satisfying the design requirements. This procedure of reoptimization design parameters would be useful in improving the control system performance if accurate model data are provided.

Association between study design and citation counts of articles published in the American Journal of Orthodontics and Dentofacial Orthopedics and Angle Orthodontist.

PubMed

Allareddy, Veerasathpurush; Lee, Min Kyeong; Shah, Andrea; Elangovan, Satheesh; Lin, Chin-Yu

2012-01-01

The scientific community views meta-analyses and systematic reviews, in addition to well-designed randomized controlled clinical trials, as the highest echelon in the continuum of hierarchy of evidence. The objective of this study was to examine the association between different study designs and citation counts of articles published in the American Journal of Orthodontics and Dentofacial Orthopedics and Angle Orthodontist. All articles, excluding editorial comments, letters to the editor, commentaries, and special articles, that were published in the American Journal of Orthodontics and Dentofacial Orthopedics and Angle Orthodontist during the years 2004 and 2005 were examined in this study. The number of times an article was cited in the first 24 months after its publication was computed. The PubMed database was used to index the study design of the articles. The association between study design and citation counts was examined using the Kruskal-Wallis test. A multivariable negative binomial regression model was used to examine the association between citation count and study design along with several other confounding variables. A total of 624 articles were selected for analysis. Of these, there were 25 meta-analyses or review articles, 42 randomized clinical trials, 59 clinical trials, 48 animal studies, 64 case reports, and 386 quasiexperimental/miscellaneous study designs. The mean ± SD citation count was 1.04 ± 1.46. Nearly half of the articles (n = 311) were not cited even once during the observation period. Case reports were cited less frequently than meta-analyses or reviews (incident risk ratio, 0.37; 95% confidence interval, 0.19 to 0.72; P = .003), even after adjusting for other independent variables. Among various study designs, meta-analyses and review articles are more likely to be cited in the first 24 months after publication. This study demonstrates the importance of publishing more meta-analyses and review articles for quicker dissemination of research findings.

Instrumental variables I: instrumental variables exploit natural variation in nonexperimental data to estimate causal relationships.

PubMed

Rassen, Jeremy A; Brookhart, M Alan; Glynn, Robert J; Mittleman, Murray A; Schneeweiss, Sebastian

2009-12-01

The gold standard of study design for treatment evaluation is widely acknowledged to be the randomized controlled trial (RCT). Trials allow for the estimation of causal effect by randomly assigning participants either to an intervention or comparison group; through the assumption of "exchangeability" between groups, comparing the outcomes will yield an estimate of causal effect. In the many cases where RCTs are impractical or unethical, instrumental variable (IV) analysis offers a nonexperimental alternative based on many of the same principles. IV analysis relies on finding a naturally varying phenomenon, related to treatment but not to outcome except through the effect of treatment itself, and then using this phenomenon as a proxy for the confounded treatment variable. This article demonstrates how IV analysis arises from an analogous but potentially impossible RCT design, and outlines the assumptions necessary for valid estimation. It gives examples of instruments used in clinical epidemiology and concludes with an outline on estimation of effects.

Instrumental variables I: instrumental variables exploit natural variation in nonexperimental data to estimate causal relationships

PubMed Central

Rassen, Jeremy A.; Brookhart, M. Alan; Glynn, Robert J.; Mittleman, Murray A.; Schneeweiss, Sebastian

2010-01-01

The gold standard of study design for treatment evaluation is widely acknowledged to be the randomized controlled trial (RCT). Trials allow for the estimation of causal effect by randomly assigning participants either to an intervention or comparison group; through the assumption of “exchangeability” between groups, comparing the outcomes will yield an estimate of causal effect. In the many cases where RCTs are impractical or unethical, instrumental variable (IV) analysis offers a nonexperimental alternative based on many of the same principles. IV analysis relies on finding a naturally varying phenomenon, related to treatment but not to outcome except through the effect of treatment itself, and then using this phenomenon as a proxy for the confounded treatment variable. This article demonstrates how IV analysis arises from an analogous but potentially impossible RCT design, and outlines the assumptions necessary for valid estimation. It gives examples of instruments used in clinical epidemiology and concludes with an outline on estimation of effects. PMID:19356901

Population health needs as predictors of variations in NHS practice payments: a cross-sectional study of English general practices in 2013–2014 and 2014–2015

PubMed Central

Levene, Louis S; Baker, Richard; Wilson, Andrew; Walker, Nicola; Boomla, Kambiz; Bankart, M John G

2017-01-01

Background NHS general practice payments in England include pay for performance elements and a weighted component designed to compensate for workload, but without measures of specific deprivation or ethnic groups. Aim To determine whether population factors related to health needs predicted variations in NHS payments to individual general practices in England. Design and setting Cross-sectional study of all practices in England, in financial years 2013–2014 and 2014–2015. Method Descriptive statistics, univariable analyses (examining correlations between payment and predictors), and multivariable analyses (undertaking multivariable linear regressions for each year, with logarithms of payments as the dependent variables, and with population, practice, and performance factors as independent variables) were undertaken. Results Several population variables predicted variations in adjusted total payments, but inconsistently. Higher payments were associated with increases in deprivation, patients of older age, African Caribbean ethnic group, and asthma prevalence. Lower payments were associated with an increase in smoking prevalence. Long-term health conditions, South Asian ethnic group, and diabetes prevalence were not predictive. The adjusted R2 values were 0.359 (2013–2014) and 0.374 (2014–2015). A slightly different set of variables predicted variations in the payment component designed to compensate for workload. Lower payments were associated with increases in deprivation, patients of older age, and diabetes prevalence. Smoking prevalence was not predictive. There was a geographical differential. Conclusion Population factors related to health needs were, overall, poor predictors of variations in adjusted total practice payments and in the payment component designed to compensate for workload. Revising the weighting formula and extending weighting to other payment components might better support practices to address these needs. PMID:27872085

Relative Contributions of Selected Teachers' Variables and Students' Attitudes toward Academic Achievement in Biology among Senior Secondary School Students in Ondo State, Nigeria

ERIC Educational Resources Information Center

Gbore, L. O.; Daramola, C. A.

2013-01-01

This study investigated the relative contributions of selected teachers' variables and students' attitude towards academic achievement in biology among senior secondary schools in Ondo State, Nigeria. It involved descriptive survey research and ex-post facto research designs. The sample, 360 respondents which consists of 180 biology teachers and…

Children's Acquisition and Use of the Control-of-Variables Strategy: Effects of Explicit and Implicit Instructional Guidance

ERIC Educational Resources Information Center

Lazonder, Ard W.; Egberink, Angelique

2014-01-01

Direct instruction is a proven effective method to strengthen children's ability to design unconfounded experiments using the control-of-variables strategy (CVS). Recent research suggests that task segmentation can also promote children's use of this strategy. The present study investigated this assumption by comparing the relative…

The Effects of Training, Modality, and Redundancy on the Development of a Historical Inquiry Strategy in a Multimedia Learning Environment

ERIC Educational Resources Information Center

McNeill, Andrea L.; Doolittle, Peter E.; Hicks, David

2009-01-01

The purpose of this study was to assess the effects of training, modality, and redundancy on the participants' ability to apply and recall a historical inquiry strategy. An experimental research design was utilized with presentation mode as the independent variable and strategy application and strategy recall as the dependent variables. The…

A Study of the Effect of Socioeconomic Factors on the School Achievement of Spanish-Speaking School Beginners.

ERIC Educational Resources Information Center

MacMillan, Robert Wilson

A model of inquiry was designed to test the correlation between certain socioeconomic variables and school achievement of Spanish-speaking 1st-graders in San Antonio, Texas. For analyses of these variables as predictors of achievement and attendance, 305 Mexican American children were used; 5 Mexican American, 4 Negro, and 3 Anglo schools were…

Motivational and Volitional Variables Associated with Stages of Change for Exercise in Multiple Sclerosis: A Multiple Discriminant Analysis

ERIC Educational Resources Information Center

Chiu, Chung-Yi; Fitzgerald, Sandra D.; Strand, David M.; Muller, Veronica; Brooks, Jessica; Chan, Fong

2012-01-01

The main objective of this study was to determine whether motivational and volitional variables identified in the health action process approach (HAPA) model can be used to successfully differentiate people with multiple sclerosis (MS) in different stages of change for exercise and physical activity. Ex-post-facto design using multiple…

Long-term streamflow response to climatic variability in the Loess Plateau, China

Treesearch

Shenping Wang; Zhiqiang Zhang; Ge Sun; Steven G. McNulty; Huayong Zhang; Jianlao Li; Manliang Zhang

2008-01-01

The Loess Plateau region in northwestern China has experienced severe water resource shortages due to the combined impacts of climate and land use changes and water resource exploitation during the past decades. This study was designed to examine the impacts of climatic variability on streamflow characteristics of a 12-km2 watershed near Tianshui City, Gansu Province...

Analysis of Primary School Student's Science Learning Anxiety According to Some Variables

ERIC Educational Resources Information Center

Karakaya, Ferhat; Avgin, Sakine Serap; Kumperli, Ethem

2016-01-01

On this research, it is analyzed if the science learning anxiety level shows difference according to variables which are gender, grade level, science lesson grade, mother education, father education level. Scanning Design is used for this study. Research working group is consisted of 294 primary school from 6th, 7th and 8th graders on 2015-2016…

The Effects of Gesture and Movement Training on the Intonation of Children's Singing in Vocal Warm-Up Sessions

ERIC Educational Resources Information Center

Liao, Mei-Ying; Davidson, Jane W.

2016-01-01

The main purpose of the current study was to examine the effects of gesture and movement training for beginning children's choirs with regard to improving intonation. It was a between-subjects design with one independent variable Training Technique (TT). One dependent variable was measured: intonation in the singing of vocal pattern warm-up…

Effect of Variable Emittance Coatings on the Operation of a Miniature Loop Heat Pipe

NASA Technical Reports Server (NTRS)

Douglas, Donya M.; Ku, Jentung; Ottenstein, Laura; Swanson, Theodore; Hess, Steve; Darrin, Ann

2005-01-01

Abstract. As the size of spacecraft shrink to accommodate small and more efficient instruments, smaller launch vehicles, and constellation missions, all subsystems must also be made smaller. Under NASA NFL4 03-OSS-02, Space Technology-8 (ST 8), NASA Goddard Space Flight Center and Jet Propulsion Laboratory jointly conducted a Concept Definition study to develop a miniature loop heat pipe (MLHP) thermal management system design suitable for future small spacecraft. The proposed MLHP thermal management system consists of a miniature loop heat pipe (LHP) and deployable radiators that are coated with variable emittance coatings (VECs). As part of the Phase A study and proof of the design concept, variable emittance coatings were integrated with a breadboard miniature loop heat pipe. The miniature loop heat pipe was supplied by the Jet Propulsion Laboratory (PL), while the variable emittance technology were supplied by Johns Hopkins University Applied Physics Laboratory and Sensortex, Inc. The entire system was tested under vacuum at various temperature extremes and power loads. This paper summarizes the results of this testing and shows the effect of the VEC on the operation of a miniature loop heat pipe.

Invariance and variability in interaction error-related potentials and their consequences for classification

NASA Astrophysics Data System (ADS)

Abu-Alqumsan, Mohammad; Kapeller, Christoph; Hintermüller, Christoph; Guger, Christoph; Peer, Angelika

2017-12-01

Objective. This paper discusses the invariance and variability in interaction error-related potentials (ErrPs), where a special focus is laid upon the factors of (1) the human mental processing required to assess interface actions (2) time (3) subjects. Approach. Three different experiments were designed as to vary primarily with respect to the mental processes that are necessary to assess whether an interface error has occurred or not. The three experiments were carried out with 11 subjects in a repeated-measures experimental design. To study the effect of time, a subset of the recruited subjects additionally performed the same experiments on different days. Main results. The ErrP variability across the different experiments for the same subjects was found largely attributable to the different mental processing required to assess interface actions. Nonetheless, we found that interaction ErrPs are empirically invariant over time (for the same subject and same interface) and to a lesser extent across subjects (for the same interface). Significance. The obtained results may be used to explain across-study variability of ErrPs, as well as to define guidelines for approaches to the ErrP classifier transferability problem.

Oscar: a portable prototype system for the study of climate variability

NASA Astrophysics Data System (ADS)

Madonna, Fabio; Rosoldi, Marco; Amato, Francesco

2015-04-01

The study of the techniques for the exploitation of solar energy implies the knowledge of nature, ecosystem, biological factors and local climate. Clouds, fog, water vapor, and the presence of large concentrations of dust can significantly affect the way to exploit the solar energy. Therefore, a quantitative characterization of the impact of climate variability at the regional scale is needed to increase the efficiency and sustainability of the energy system. OSCAR (Observation System for Climate Application at Regional scale) project, funded in the frame of the PO FESR 2007-2013, aims at the design of a portable prototype system for the study of correlations among the trends of several Essential Climate Variables (ECVs) and the change in the amount of solar irradiance at the ground level. The final goal of this project is to provide a user-friendly low cost solution for the quantification of the impact of regional climate variability on the efficiency of solar cell and concentrators to improve the exploitation of natural sources. The prototype has been designed on the basis of historical measurements performed at CNR-IMAA Atmospheric Observatory (CIAO). Measurements from satellite and data from models have been also considered as ancillary to the study, above all, to fill in the gaps of existing datasets. In this work, the results outcome from the project activities will be presented. The results include: the design and implementation of the prototype system; the development of a methodology for the estimation of the impact of climate variability, mainly due to aerosol, cloud and water vapor, on the solar irradiance using the integration of the observations potentially provided by prototype; the study of correlation between the surface radiation, precipitation and aerosols transport. In particular, a statistical study will be presented to assess the impact of the atmosphere on the solar irradiance at the ground, quantifying the contribution due to aerosol and clouds and separating their effect on the direct and the diffuse components of the solar radiation. This also aims to provide recommendations to the manufacturer of the devices used to exploit solar radiation.

Integrated Control Using the SOFFT Control Structure

NASA Technical Reports Server (NTRS)

Halyo, Nesim

1996-01-01

The need for integrated/constrained control systems has become clearer as advanced aircraft introduced new coupled subsystems such as new propulsion subsystems with thrust vectoring and new aerodynamic designs. In this study, we develop an integrated control design methodology which accomodates constraints among subsystem variables while using the Stochastic Optimal Feedforward/Feedback Control Technique (SOFFT) thus maintaining all the advantages of the SOFFT approach. The Integrated SOFFT Control methodology uses a centralized feedforward control and a constrained feedback control law. The control thus takes advantage of the known coupling among the subsystems while maintaining the identity of subsystems for validation purposes and the simplicity of the feedback law to understand the system response in complicated nonlinear scenarios. The Variable-Gain Output Feedback Control methodology (including constant gain output feedback) is extended to accommodate equality constraints. A gain computation algorithm is developed. The designer can set the cross-gains between two variables or subsystems to zero or another value and optimize the remaining gains subject to the constraint. An integrated control law is designed for a modified F-15 SMTD aircraft model with coupled airframe and propulsion subsystems using the Integrated SOFFT Control methodology to produce a set of desired flying qualities.

Estimates of Intraclass Correlation for Variables Related to Behavioral HIV/STD Prevention in a Predominantly African American and Hispanic Sample of Young Women

ERIC Educational Resources Information Center

Pals, Sherri L.; Beaty, Brenda L.; Posner, Samuel F.; Bull, Sheana S.

2009-01-01

Studies designed to evaluate HIV and STD prevention interventions often involve random assignment of groups such as neighborhoods or communities to study conditions (e.g., to intervention or control). Investigators who design group-randomized trials (GRTs) must take the expected intraclass correlation coefficient (ICC) into account in sample size…

A Darwinian approach to control-structure design

NASA Technical Reports Server (NTRS)

Zimmerman, David C.

1993-01-01

Genetic algorithms (GA's), as introduced by Holland (1975), are one form of directed random search. The form of direction is based on Darwin's 'survival of the fittest' theories. GA's are radically different from the more traditional design optimization techniques. GA's work with a coding of the design variables, as opposed to working with the design variables directly. The search is conducted from a population of designs (i.e., from a large number of points in the design space), unlike the traditional algorithms which search from a single design point. The GA requires only objective function information, as opposed to gradient or other auxiliary information. Finally, the GA is based on probabilistic transition rules, as opposed to deterministic rules. These features allow the GA to attack problems with local-global minima, discontinuous design spaces and mixed variable problems, all in a single, consistent framework.

Immunization in pregnancy clinical research in low- and middle-income countries - Study design, regulatory and safety considerations.

PubMed

Kochhar, Sonali; Bonhoeffer, Jan; Jones, Christine E; Muñoz, Flor M; Honrado, Angel; Bauwens, Jorgen; Sobanjo-Ter Meulen, Ajoke; Hirschfeld, Steven

2017-12-04

Immunization of pregnant women is a promising public health strategy to reduce morbidity and mortality among both the mothers and their infants. Establishing safety and efficacy of vaccines generally uses a hybrid design between a conventional interventional study and an observational study that requires enrolling thousands of study participants to detect an unknown number of uncommon events. Historically, enrollment of pregnant women in clinical research studies encountered many barriers based on risk aversion, lack of knowledge, and regulatory ambiguity. Conducting research enrolling pregnant women in low- and middle-income countries can have additional factors to address such as limited availability of baseline epidemiologic data on disease burden and maternal and neonatal outcomes during and after pregnancy; challenges in recruiting and retaining pregnant women in research studies, variability in applying and interpreting assessment methods, and variability in locally acceptable and available infrastructure. Some measures to address these challenges include adjustment of study design, tailoring recruitment, consent process, retention strategies, operational and logistical processes, and the use of definitions and data collection methods that will align with efforts globally. Copyright © 2017. Published by Elsevier Ltd.

Tobacco smoking and depression: time to move on to a new research paradigm in medicine?

PubMed

de Jonge, Peter; Bos, Elisabeth Henriette

2013-05-24

A recent paper published in BMC Cardiovascular Disorders reported on a study into whether tobacco smoking may serve as a risk factor for depression in patients with heart disease. In the current paper, we discuss several limitations of that study, of which many apply not just to the study itself but to the nomothetic research design that was used. Particularly when bidirectionality between variables is expected, fluctuation in variables over time takes place, and/or inter-individual differences are considerable, a nomothetic research approach does not seem appropriate, and may lead to false conclusions. As an alternative, we describe an idiographic approach in which individuals are followed up over time using many repeated measurements, and from which individual models are estimated. Such intensive time-series studies are not common in medicine, but are well described in the fields of econometrics and meteorology. Combining idiographic research designs with more traditional nomothetic designs may lead to research findings that are not only useful for society but also valid in individuals. See related research article here http://www.biomedcentral.com/1471-2261/13/35.

Tobacco smoking and depression: time to move on to a new research paradigm in medicine?

PubMed Central

2013-01-01

A recent paper published in BMC Cardiovascular Disorders reported on a study into whether tobacco smoking may serve as a risk factor for depression in patients with heart disease. In the current paper, we discuss several limitations of that study, of which many apply not just to the study itself but to the nomothetic research design that was used. Particularly when bidirectionality between variables is expected, fluctuation in variables over time takes place, and/or inter-individual differences are considerable, a nomothetic research approach does not seem appropriate, and may lead to false conclusions. As an alternative, we describe an idiographic approach in which individuals are followed up over time using many repeated measurements, and from which individual models are estimated. Such intensive time-series studies are not common in medicine, but are well described in the fields of econometrics and meteorology. Combining idiographic research designs with more traditional nomothetic designs may lead to research findings that are not only useful for society but also valid in individuals. See related research article here http://www.biomedcentral.com/1471-2261/13/35. PMID:23705867

Prolonged release matrix tablet of pyridostigmine bromide: formulation and optimization using statistical methods.

PubMed

Bolourchian, Noushin; Rangchian, Maryam; Foroutan, Seyed Mohsen

2012-07-01

The aim of this study was to design and optimize a prolonged release matrix formulation of pyridostigmine bromide, an effective drug in myasthenia gravis and poisoning with nerve gas, using hydrophilic - hydrophobic polymers via D-optimal experimental design. HPMC and carnauba wax as retarding agents as well as tricalcium phosphate were used in matrix formulation and considered as independent variables. Tablets were prepared by wet granulation technique and the percentage of drug released at 1 (Y(1)), 4 (Y(2)) and 8 (Y(3)) hours were considered as dependent variables (responses) in this investigation. These experimental responses were best fitted for the cubic, cubic and linear models, respectively. The optimal formulation obtained in this study, consisted of 12.8 % HPMC, 24.4 % carnauba wax and 26.7 % tricalcium phosphate, had a suitable prolonged release behavior followed by Higuchi model in which observed and predicted values were very close. The study revealed that D-optimal design could facilitate the optimization of prolonged release matrix tablet containing pyridostigmine bromide. Accelerated stability studies confirmed that the optimized formulation remains unchanged after exposing in stability conditions for six months.

Space Shuttle 2 advanced space transportation system, volume 2

NASA Technical Reports Server (NTRS)

Adinaro, James N.; Benefield, Philip A.; Johnson, Shelby D.; Knight, Lisa K.

1989-01-01

To determine the best configuration from all candidate configurations, it was necessary first to calculate minimum system weights and performance. To optimize the design, it is necessary to vary configuration-specific variables such as total system weight, thrust-to-weight ratios, burn durations, total thrust available, and mass fraction for the system. Optimizing each of these variables at the same time is technically unfeasible and not necessarily mathematically possible. However, discrete sets of data can be generated which will eliminate many candidate configurations. From the most promising remaining designs, a final configuration can be selected. Included are the three most important designs considered: one which closely approximates the design criteria set forth in a Marshall Space Flight Center study of the Shuttle 2; the configuration used in the initial proposal; and the final configuration. A listing by cell of the formulas used to generate the aforementioned data is included for reference.

The role of intersection and street design on severity of bicycle-motor vehicle crashes

PubMed Central

Verma, Santosh; Mekary, Rania A; Courtney, Theodore K; Christiani, David C

2017-01-01

Background Safety concerns are a major barrier to cycling. Intersection and street design variables such as intersection angles and street width might contribute to the severity of crashes and the safety concerns. In this study we examined whether these design variables were associated with bicycle-motor vehicle crashes (BMVC) severity. Methods Using the geographical information system and latitudes/longitudes recorded by the police using a global positioning device, we extracted intersection angles, street width, bicycle facilities, posted speed limits and annual average daily traffic from 3266 BMVC data from New York City police records. Additional variables about BMVC, including age and sex of the bicyclist, time of the day, road surface conditions, road character, vehicle type and injury severity, were obtained from police reports. Injury severity was classified as severe (incapacitating or killed) or non-severe (non-incapacitating, possible injury). The associations between injury severity and environment design variables were examined using multivariate log-binomial regression model. Findings Compared with crashes at orthogonal intersections, crashes at non-orthogonal intersections had 1.37 times (95% CI 1.05 to 1.80) and non-intersection street segments had 1.31 times (95% CI 1.01 to 1.70) higher risk of a severe injury. Crashes that involved a truck or a bus were twice as likely to result in a severe injury outcome; street width was not significantly associated with injury severity. Conclusion Crashes at non-orthogonal intersections and non-intersection segments are more likely to result in higher injury severity. The findings can be used to improve road design and develop effective safety interventions. PMID:27881469

An Efficient Variable Screening Method for Effective Surrogate Models for Reliability-Based Design Optimization

DTIC Science & Technology

2014-04-01

surrogate model generation is difficult for high -dimensional problems, due to the curse of dimensionality. Variable screening methods have been...a variable screening model was developed for the quasi-molecular treatment of ion-atom collision [16]. In engineering, a confidence interval of...for high -level radioactive waste [18]. Moreover, the design sensitivity method can be extended to the variable screening method because vital

Analytical and numerical study on cooling flow field designs performance of PEM fuel cell with variable heat flux

NASA Astrophysics Data System (ADS)

Afshari, Ebrahim; Ziaei-Rad, Masoud; Jahantigh, Nabi

2016-06-01

In PEM fuel cells, during electrochemical generation of electricity more than half of the chemical energy of hydrogen is converted to heat. This heat of reactions, if not exhausted properly, would impair the performance and durability of the cell. In general, large scale PEM fuel cells are cooled by liquid water that circulates through coolant flow channels formed in bipolar plates or in dedicated cooling plates. In this paper, a numerical method has been presented to study cooling and temperature distribution of a polymer membrane fuel cell stack. The heat flux on the cooling plate is variable. A three-dimensional model of fluid flow and heat transfer in cooling plates with 15 cm × 15 cm square area is considered and the performances of four different coolant flow field designs, parallel field and serpentine fields are compared in terms of maximum surface temperature, temperature uniformity and pressure drop characteristics. By comparing the results in two cases, the constant and variable heat flux, it is observed that applying constant heat flux instead of variable heat flux which is actually occurring in the fuel cells is not an accurate assumption. The numerical results indicated that the straight flow field model has temperature uniformity index and almost the same temperature difference with the serpentine models, while its pressure drop is less than all of the serpentine models. Another important advantage of this model is the much easier design and building than the spiral models.

Designed experiment evaluation of key variables affecting the cutting performance of rotary instruments.

PubMed

Funkenbusch, Paul D; Rotella, Mario; Ercoli, Carlo

2015-04-01

Laboratory studies of tooth preparation are often performed under a limited range of conditions involving single values for all variables other than the 1 being tested. In contrast, in clinical settings not all variables can be tightly controlled. For example, a new dental rotary cutting instrument may be tested in the laboratory by making a specific cut with a fixed force, but in clinical practice, the instrument must make different cuts with individual dentists applying a range of different forces. Therefore, the broad applicability of laboratory results to diverse clinical conditions is uncertain and the comparison of effects across studies is difficult. The purpose of this study was to examine the effect of 9 process variables on dental cutting in a single experiment, allowing each variable to be robustly tested over a range of values for the other 8 and permitting a direct comparison of the relative importance of each on the cutting process. The effects of 9 key process variables on the efficiency of a simulated dental cutting operation were measured. A fractional factorial experiment was conducted by using a computer-controlled, dedicated testing apparatus to simulate dental cutting procedures and Macor blocks as the cutting substrate. Analysis of Variance (ANOVA) was used to judge the statistical significance (α=.05). Five variables consistently produced large, statistically significant effects (target applied load, cut length, starting rpm, diamond grit size, and cut type), while 4 variables produced relatively small, statistically insignificant effects (number of cooling ports, rotary cutting instrument diameter, disposability, and water flow rate). The control exerted by the dentist, simulated in this study by targeting a specific level of applied force, was the single most important factor affecting cutting efficiency. Cutting efficiency was also significantly affected by factors simulating patient/clinical circumstances as well as hardware choices. These results highlight the importance of local clinical conditions (procedure, dentist) in understanding dental cutting procedures and in designing adequate experimental methodologies for future studies. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

A variable-gain output feedback control design approach

NASA Technical Reports Server (NTRS)

Haylo, Nesim

1989-01-01

A multi-model design technique to find a variable-gain control law defined over the whole operating range is proposed. The design is formulated as an optimal control problem which minimizes a cost function weighing the performance at many operating points. The solution is obtained by embedding into the Multi-Configuration Control (MCC) problem, a multi-model robust control design technique. In contrast to conventional gain scheduling which uses a curve fit of single model designs, the optimal variable-gain control law stabilizes the plant at every operating point included in the design. An iterative algorithm to compute the optimal control gains is presented. The methodology has been successfully applied to reconfigurable aircraft flight control and to nonlinear flight control systems.

Aerodynamic design and optimization in one shot

NASA Technical Reports Server (NTRS)

Ta'asan, Shlomo; Kuruvila, G.; Salas, M. D.

1992-01-01

This paper describes an efficient numerical approach for the design and optimization of aerodynamic bodies. As in classical optimal control methods, the present approach introduces a cost function and a costate variable (Lagrange multiplier) in order to achieve a minimum. High efficiency is achieved by using a multigrid technique to solve for all the unknowns simultaneously, but restricting work on a design variable only to grids on which their changes produce nonsmooth perturbations. Thus, the effort required to evaluate design variables that have nonlocal effects on the solution is confined to the coarse grids. However, if a variable has a nonsmooth local effect on the solution in some neighborhood, it is relaxed in that neighborhood on finer grids. The cost of solving the optimal control problem is shown to be approximately two to three times the cost of the equivalent analysis problem. Examples are presented to illustrate the application of the method to aerodynamic design and constraint optimization.

Development of variable LRFD \\0x03C6 factors for deep foundation design due to site variability [summary].

DOT National Transportation Integrated Search

2012-01-01

Both the Florida Department of Transportation : (FDOT) and the Federal Highway Administration : (FHWA) specify use of fixed resistance factors () : for Load and Resistance Factored Design (LRFD) of : deep foundations, depending on design approach :...

Implementation of "Quality by Design (QbD)" Approach for the Development of 5-Fluorouracil Loaded Thermosensitive Hydrogel.

PubMed

Dalwadi, Chintan; Patel, Gayatri

2016-01-01

The purpose of this study was to investigate Quality by Design (QbD) principle for the preparation of hydrogel products to prove both practicability and utility of executing QbD concept to hydrogel based controlled release systems. Product and process understanding will help in decreasing the variability of critical material and process parameters, which give quality product output and reduce the risk. This study includes the identification of the Quality Target Product Profiles (QTPPs) and Critical Quality Attributes (CQAs) from literature or preliminary studies. To identify and control the variability in process and material attributes, two tools of QbD was utilized, Quality Risk Management (QRM) and Experimental Design. Further, it helps to identify the effect of these attributes on CQAs. Potential risk factors were identified from fishbone diagram and screened by risk assessment and optimized by 3-level 2- factor experimental design with center points in triplicate, to analyze the precision of the target process. This optimized formulation was further characterized by gelling time, gelling temperature, rheological parameters, in-vitro biodegradation and in-vitro drug release. Design space was created using experimental design tool that gives the control space and working within this controlled space reduces all the failure modes below the risk level. In conclusion, QbD approach with QRM tool provides potent and effectual pyramid to enhance the quality into the hydrogel.

An all-at-once reduced Hessian SQP scheme for aerodynamic design optimization

NASA Technical Reports Server (NTRS)

Feng, Dan; Pulliam, Thomas H.

1995-01-01

This paper introduces a computational scheme for solving a class of aerodynamic design problems that can be posed as nonlinear equality constrained optimizations. The scheme treats the flow and design variables as independent variables, and solves the constrained optimization problem via reduced Hessian successive quadratic programming. It updates the design and flow variables simultaneously at each iteration and allows flow variables to be infeasible before convergence. The solution of an adjoint flow equation is never needed. In addition, a range space basis is chosen so that in a certain sense the 'cross term' ignored in reduced Hessian SQP methods is minimized. Numerical results for a nozzle design using the quasi-one-dimensional Euler equations show that this scheme is computationally efficient and robust. The computational cost of a typical nozzle design is only a fraction more than that of the corresponding analysis flow calculation. Superlinear convergence is also observed, which agrees with the theoretical properties of this scheme. All optimal solutions are obtained by starting far away from the final solution.

Analysis of 12 AH aerospace nickel-cadmium cells from the design variable program

NASA Technical Reports Server (NTRS)

Vasanth, Kunigahalli L.; Morrow, George

1987-01-01

The Design Variable Program of NASA/GSFC provided a systematic approach to evaluate the performance of 12 Ampere-Hour Nickel-Cadmium cells of different designs. Design Variables tested in this program included teflonated negative plates, silver treated negative plates, lightly loaded negative plates, positive plates with no cadmium treatment, plate design of 1968 utilizing old and new processing techniques and electrochemically impregnated positive plates. These cells were life cycled in a Low-Earth Orbit (LEO) regime for 3 to 4 years. Representative cells taken from the Design Variable Program were examined via chemical, electrochemical and surface analyses. The results indicate the following: (1) positive swelling and carbonate content in the electrolyte increase as a function of number of cycles; (2) electrolyte distribution follows a general order NEG greater than POS greater than SEP; (3) control and No PQ groups outperformed the rest of the groups; and (4) the polyproylene group exhibited heavy cadmium migration and poor performance.

Using Bayesian variable selection to analyze regular resolution IV two-level fractional factorial designs

DOE PAGES

Chipman, Hugh A.; Hamada, Michael S.

2016-06-02

Regular two-level fractional factorial designs have complete aliasing in which the associated columns of multiple effects are identical. Here, we show how Bayesian variable selection can be used to analyze experiments that use such designs. In addition to sparsity and hierarchy, Bayesian variable selection naturally incorporates heredity . This prior information is used to identify the most likely combinations of active terms. We also demonstrate the method on simulated and real experiments.

Using Bayesian variable selection to analyze regular resolution IV two-level fractional factorial designs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chipman, Hugh A.; Hamada, Michael S.

Regular two-level fractional factorial designs have complete aliasing in which the associated columns of multiple effects are identical. Here, we show how Bayesian variable selection can be used to analyze experiments that use such designs. In addition to sparsity and hierarchy, Bayesian variable selection naturally incorporates heredity . This prior information is used to identify the most likely combinations of active terms. We also demonstrate the method on simulated and real experiments.

A variable-gain output feedback control design methodology

NASA Technical Reports Server (NTRS)

Halyo, Nesim; Moerder, Daniel D.; Broussard, John R.; Taylor, Deborah B.

1989-01-01

A digital control system design technique is developed in which the control system gain matrix varies with the plant operating point parameters. The design technique is obtained by formulating the problem as an optimal stochastic output feedback control law with variable gains. This approach provides a control theory framework within which the operating range of a control law can be significantly extended. Furthermore, the approach avoids the major shortcomings of the conventional gain-scheduling techniques. The optimal variable gain output feedback control problem is solved by embedding the Multi-Configuration Control (MCC) problem, previously solved at ICS. An algorithm to compute the optimal variable gain output feedback control gain matrices is developed. The algorithm is a modified version of the MCC algorithm improved so as to handle the large dimensionality which arises particularly in variable-gain control problems. The design methodology developed is applied to a reconfigurable aircraft control problem. A variable-gain output feedback control problem was formulated to design a flight control law for an AFTI F-16 aircraft which can automatically reconfigure its control strategy to accommodate failures in the horizontal tail control surface. Simulations of the closed-loop reconfigurable system show that the approach produces a control design which can accommodate such failures with relative ease. The technique can be applied to many other problems including sensor failure accommodation, mode switching control laws and super agility.

FRANOPP: Framework for analysis and optimization problems user's guide

NASA Technical Reports Server (NTRS)

Riley, K. M.

1981-01-01

Framework for analysis and optimization problems (FRANOPP) is a software aid for the study and solution of design (optimization) problems which provides the driving program and plotting capability for a user generated programming system. In addition to FRANOPP, the programming system also contains the optimization code CONMIN, and two user supplied codes, one for analysis and one for output. With FRANOPP the user is provided with five options for studying a design problem. Three of the options utilize the plot capability and present an indepth study of the design problem. The study can be focused on a history of the optimization process or on the interaction of variables within the design problem.

A comparison of two microscale laboratory reporting methods in a secondary chemistry classroom

NASA Astrophysics Data System (ADS)

Martinez, Lance Michael

This study attempted to determine if there was a difference between the laboratory achievement of students who used a modified reporting method and those who used traditional laboratory reporting. The study also determined the relationships between laboratory performance scores and the independent variables score on the Group Assessment of Logical Thinking (GALT) test, chronological age in months, gender, and ethnicity for each of the treatment groups. The study was conducted using 113 high school students who were enrolled in first-year general chemistry classes at Pueblo South High School in Colorado. The research design used was the quasi-experimental Nonequivalent Control Group Design. The statistical treatment consisted of the Multiple Regression Analysis and the Analysis of Covariance. Based on the GALT, students in the two groups were generally in the concrete and transitional stages of the Piagetian cognitive levels. The findings of the study revealed that the traditional and the modified methods of laboratory reporting did not have any effect on the laboratory performance outcome of the subjects. However, the students who used the traditional method of reporting showed a higher laboratory performance score when evaluation was conducted using the New Standards rubric recommended by the state. Multiple Regression Analysis revealed that there was a significant relationship between the criterion variable student laboratory performance outcome of individuals who employed traditional laboratory reporting methods and the composite set of predictor variables. On the contrary, there was no significant relationship between the criterion variable student laboratory performance outcome of individuals who employed modified laboratory reporting methods and the composite set of predictor variables.

A pilot data collecting exercise on stress and nursing students.

PubMed

Por, Jitna

This article discusses the lessons learned from a small pilot study exploring the link between the working environment and occupational stress among groups of nursing students. A comparative descriptive design was adopted to examine, describe and compare the two variables (sources and frequency) in three groups of nursing students. The sample comprised 90 students from one large inner-city school of nursing in London. The Expanded Nursing Stress Scale questionnaires were used to collect the data. The main findings suggest that the adult, child and mental health branch students were similar with respect to overall frequency of occupational stress. Areas of commonality and variability in the sources of stress perceived by the three groups of students were identified. A pilot study is a crucial element of a good study design. Areas of concern, lessons learned and suggested refinements were identified.

Design sensitivity analysis of rotorcraft airframe structures for vibration reduction

NASA Technical Reports Server (NTRS)

Murthy, T. Sreekanta

1987-01-01

Optimization of rotorcraft structures for vibration reduction was studied. The objective of this study is to develop practical computational procedures for structural optimization of airframes subject to steady-state vibration response constraints. One of the key elements of any such computational procedure is design sensitivity analysis. A method for design sensitivity analysis of airframes under vibration response constraints is presented. The mathematical formulation of the method and its implementation as a new solution sequence in MSC/NASTRAN are described. The results of the application of the method to a simple finite element stick model of the AH-1G helicopter airframe are presented and discussed. Selection of design variables that are most likely to bring about changes in the response at specified locations in the airframe is based on consideration of forced response strain energy. Sensitivity coefficients are determined for the selected design variable set. Constraints on the natural frequencies are also included in addition to the constraints on the steady-state response. Sensitivity coefficients for these constraints are determined. Results of the analysis and insights gained in applying the method to the airframe model are discussed. The general nature of future work to be conducted is described.

A Comparative Propulsion System Analysis for the High-Speed Civil Transport

NASA Technical Reports Server (NTRS)

Berton, Jeffrey J.; Haller, William J.; Senick, Paul F.; Jones, Scott M.; Seidel, Jonathan A.

2005-01-01

Six of the candidate propulsion systems for the High-Speed Civil Transport are the turbojet, turbine bypass engine, mixed flow turbofan, variable cycle engine, Flade engine, and the inverting flow valve engine. A comparison of these propulsion systems by NASA's Glenn Research Center, paralleling studies within the aircraft industry, is presented. This report describes the Glenn Aeropropulsion Analysis Office's contribution to the High-Speed Research Program's 1993 and 1994 propulsion system selections. A parametric investigation of each propulsion cycle's primary design variables is analytically performed. Performance, weight, and geometric data are calculated for each engine. The resulting engines are then evaluated on two airframer-derived supersonic commercial aircraft for a 5000 nautical mile, Mach 2.4 cruise design mission. The effects of takeoff noise, cruise emissions, and cycle design rules are examined.

Structural tailoring of engine blades (STAEBL) user's manual

NASA Technical Reports Server (NTRS)

Brown, K. W.

1985-01-01

This User's Manual contains instructions and demonstration case to prepare input data, run, and modify the Structural Tailoring of Engine Blades (STAEBL) computer code. STAEBL was developed to perform engine fan and compressor blade numerical optimizations. This blade optimization seeks a minimum weight or cost design that satisfies realistic blade design constraints, by tuning one to twenty design variables. The STAEBL constraint analyses include blade stresses, vibratory response, flutter, and foreign object damage. Blade design variables include airfoil thickness at several locations, blade chord, and construction variables: hole size for hollow blades, and composite material layup for composite blades.

Undertaking Experiments in Social Sciences: Sequential, Multiple Time Series Designs for Consideration

ERIC Educational Resources Information Center

Phan, Huy P.; Ngu, Bing H.

2017-01-01

In social sciences, the use of stringent methodological approaches is gaining increasing emphasis. Researchers have recognized the limitations of cross-sectional, non-manipulative data in the study of causality. True experimental designs, in contrast, are preferred as they represent rigorous standards for achieving causal flows between variables.…

The Attitudes of Field Dependence Learners for Learner Interface Design (LID) in e-Learning Instruction

ERIC Educational Resources Information Center

Sözcü, Ömer Faruk; Ipek, Ismail; Kinay, Hüseyin

2016-01-01

The purpose of the study is to explore relationships between learners' cognitive styles of field dependence and learner variables in the preference of learner Interface design, attitudes in e-Learning instruction and experience with e-Learning in distance education. Cognitive style has historically referred to a psychological dimension…

Heaping-Induced Bias in Regression-Discontinuity Designs. NBER Working Paper No. 17408

ERIC Educational Resources Information Center

Barreca, Alan I.; Lindo, Jason M.; Waddell, Glen R.

2011-01-01

This study uses Monte Carlo simulations to demonstrate that regression-discontinuity designs arrive at biased estimates when attributes related to outcomes predict heaping in the running variable. After showing that our usual diagnostics are poorly suited to identifying this type of problem, we provide alternatives. We also demonstrate how the…

Experimental Methodology in English Teaching and Learning: Method Features, Validity Issues, and Embedded Experimental Design

ERIC Educational Resources Information Center

Lee, Jang Ho

2012-01-01

Experimental methods have played a significant role in the growth of English teaching and learning studies. The paper presented here outlines basic features of experimental design, including the manipulation of independent variables, the role and practicality of randomised controlled trials (RCTs) in educational research, and alternative methods…

Mechanistic-Empirical Pavement Design Guide Flexible Pavement Performance Prediction Models Volume III Field Guide - Calibration and User's Guide for the Mechanistic-Empirical Pavement Design Guide

DOT National Transportation Integrated Search

2007-08-01

The objective of this research study was to develop performance characteristics or variables (e.g., ride quality, rutting, : fatigue cracking, transverse cracking) of flexible pavements in Montana, and to use these characteristics in the : implementa...

Advanced propulsion system for hybrid vehicles

NASA Technical Reports Server (NTRS)

Norrup, L. V.; Lintz, A. T.

1980-01-01

A number of hybrid propulsion systems were evaluated for application in several different vehicle sizes. A conceptual design was prepared for the most promising configuration. Various system configurations were parametrically evaluated and compared, design tradeoffs performed, and a conceptual design produced. Fifteen vehicle/propulsion systems concepts were parametrically evaluated to select two systems and one vehicle for detailed design tradeoff studies. A single hybrid propulsion system concept and vehicle (five passenger family sedan)were selected for optimization based on the results of the tradeoff studies. The final propulsion system consists of a 65 kW spark-ignition heat engine, a mechanical continuously variable traction transmission, a 20 kW permanent magnet axial-gap traction motor, a variable frequency inverter, a 386 kg lead-acid improved state-of-the-art battery, and a transaxle. The system was configured with a parallel power path between the heat engine and battery. It has two automatic operational modes: electric mode and heat engine mode. Power is always shared between the heat engine and battery during acceleration periods. In both modes, regenerative braking energy is absorbed by the battery.

Improving power to detect changes in blood miRNA expression by accounting for sources of variability in experimental designs.

PubMed

Daniels, Sarah I; Sillé, Fenna C M; Goldbaum, Audrey; Yee, Brenda; Key, Ellen F; Zhang, Luoping; Smith, Martyn T; Thomas, Reuben

2014-12-01

Blood miRNAs are a new promising area of disease research, but variability in miRNA measurements may limit detection of true-positive findings. Here, we measured sources of miRNA variability and determine whether repeated measures can improve power to detect fold-change differences between comparison groups. Blood from healthy volunteers (N = 12) was collected at three time points. The miRNAs were extracted by a method predetermined to give the highest miRNA yield. Nine different miRNAs were quantified using different qPCR assays and analyzed using mixed models to identify sources of variability. A larger number of miRNAs from a publicly available blood miRNA microarray dataset with repeated measures were used for a bootstrapping procedure to investigate effects of repeated measures on power to detect fold changes in miRNA expression for a theoretical case-control study. Technical variability in qPCR replicates was identified as a significant source of variability (P < 0.05) for all nine miRNAs tested. Variability was larger in the TaqMan qPCR assays (SD = 0.15-0.61) versus the qScript qPCR assays (SD = 0.08-0.14). Inter- and intraindividual and extraction variability also contributed significantly for two miRNAs. The bootstrapping procedure demonstrated that repeated measures (20%-50% of N) increased detection of a 2-fold change for approximately 10% to 45% more miRNAs. Statistical power to detect small fold changes in blood miRNAs can be improved by accounting for sources of variability using repeated measures and choosing appropriate methods to minimize variability in miRNA quantification. This study demonstrates the importance of including repeated measures in experimental designs for blood miRNA research. See all the articles in this CEBP Focus section, "Biomarkers, Biospecimens, and New Technologies in Molecular Epidemiology." ©2014 American Association for Cancer Research.

Outcome-Dependent Sampling with Interval-Censored Failure Time Data

PubMed Central

Zhou, Qingning; Cai, Jianwen; Zhou, Haibo

2017-01-01

Summary Epidemiologic studies and disease prevention trials often seek to relate an exposure variable to a failure time that suffers from interval-censoring. When the failure rate is low and the time intervals are wide, a large cohort is often required so as to yield reliable precision on the exposure-failure-time relationship. However, large cohort studies with simple random sampling could be prohibitive for investigators with a limited budget, especially when the exposure variables are expensive to obtain. Alternative cost-effective sampling designs and inference procedures are therefore desirable. We propose an outcome-dependent sampling (ODS) design with interval-censored failure time data, where we enrich the observed sample by selectively including certain more informative failure subjects. We develop a novel sieve semiparametric maximum empirical likelihood approach for fitting the proportional hazards model to data from the proposed interval-censoring ODS design. This approach employs the empirical likelihood and sieve methods to deal with the infinite-dimensional nuisance parameters, which greatly reduces the dimensionality of the estimation problem and eases the computation difficulty. The consistency and asymptotic normality of the resulting regression parameter estimator are established. The results from our extensive simulation study show that the proposed design and method works well for practical situations and is more efficient than the alternative designs and competing approaches. An example from the Atherosclerosis Risk in Communities (ARIC) study is provided for illustration. PMID:28771664

A New Approach to Extreme Value Estimation Applicable to a Wide Variety of Random Variables

NASA Technical Reports Server (NTRS)

Holland, Frederic A., Jr.

1997-01-01

Designing reliable structures requires an estimate of the maximum and minimum values (i.e., strength and load) that may be encountered in service. Yet designs based on very extreme values (to insure safety) can result in extra material usage and hence, uneconomic systems. In aerospace applications, severe over-design cannot be tolerated making it almost mandatory to design closer to the assumed limits of the design random variables. The issue then is predicting extreme values that are practical, i.e. neither too conservative or non-conservative. Obtaining design values by employing safety factors is well known to often result in overly conservative designs and. Safety factor values have historically been selected rather arbitrarily, often lacking a sound rational basis. To answer the question of how safe a design needs to be has lead design theorists to probabilistic and statistical methods. The so-called three-sigma approach is one such method and has been described as the first step in utilizing information about the data dispersion. However, this method is based on the assumption that the random variable is dispersed symmetrically about the mean and is essentially limited to normally distributed random variables. Use of this method can therefore result in unsafe or overly conservative design allowables if the common assumption of normality is incorrect.

Multi-disciplinary optimization of railway wheels

NASA Astrophysics Data System (ADS)

Nielsen, J. C. O.; Fredö, C. R.

2006-06-01

A numerical procedure for multi-disciplinary optimization of railway wheels, based on Design of Experiments (DOE) methodology and automated design, is presented. The target is a wheel design that meets the requirements for fatigue strength, while minimizing the unsprung mass and rolling noise. A 3-level full factorial (3LFF) DOE is used to collect data points required to set up Response Surface Models (RSM) relating design and response variables in the design space. Computationally efficient simulations are thereafter performed using the RSM to identify the solution that best fits the design target. A demonstration example, including four geometric design variables in a parametric finite element (FE) model, is presented. The design variables are wheel radius, web thickness, lateral offset between rim and hub, and radii at the transitions rim/web and hub/web, but more variables (including material properties) can be added if needed. To improve further the performance of the wheel design, a constrained layer damping (CLD) treatment is applied on the web. For a given load case, compared to a reference wheel design without CLD, a combination of wheel shape and damping optimization leads to the conclusion that a reduction in the wheel component of A-weighted rolling noise of 11 dB can be achieved if a simultaneous increase in wheel mass of 14 kg is accepted.

Engineering Support of Microgravity Life Science Research: Development of an Avian Development Facility

NASA Technical Reports Server (NTRS)

Vellinger, J.; Deuser, M.; Hullinger, R.

1995-01-01

The Avian Development Facility (ADF) is designed to provide a 'window' for the study of embryogenesis in space. It allows researchers to determine and then to mitigate or nullify the forces of altered gravity upon embryos when leaving and re-entering the Earth's gravity. The ADF design will allow investigations to begin their incubation after their experiments have achieved orbit, and shut down the experiment and fix specimens before leaving orbit. In effect, the ADF makes every attempt to minimize launch and re-entry effects in order to isolate and preserve the effects of the experimental variable(s) of the space environment.

Kullback-Leibler information function and the sequential selection of experiments to discriminate among several linear models. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Sidik, S. M.

1972-01-01

A sequential adaptive experimental design procedure for a related problem is studied. It is assumed that a finite set of potential linear models relating certain controlled variables to an observed variable is postulated, and that exactly one of these models is correct. The problem is to sequentially design most informative experiments so that the correct model equation can be determined with as little experimentation as possible. Discussion includes: structure of the linear models; prerequisite distribution theory; entropy functions and the Kullback-Leibler information function; the sequential decision procedure; and computer simulation results. An example of application is given.

Designing a biomechanics investigation: choosing the right model.

PubMed

Olson, Steven A; Marsh, J Lawrence; Anderson, Donald D; Latta Pe, Loren L

2012-12-01

Physical testing is commonly performed to answer important biomechanical questions in the treatment of patients with fractures and other orthopaedic conditions. However, a variety of mistakes that are made in performing such investigations can severely limit their impact. The goal of this article is to discuss important aspects of study design to consider when planning for biomechanical investigations so that the studies can provide maximal benefit to the field. The best mechanical investigations begin with a good research question, one that comes out of patient care experience, is clearly defined, and can be stated concisely. The first practical issue to be considered is often choosing the type of physical specimens to be tested to address the research question. A related issue involves determining how many specimens will be needed to answer the posed mechanical question. Cadavers are generally still the closest to the actual clinical situation, but they are limited by interspecimen variability, which often requires a matched pair design that can address only one question. Simulated bone specimens limit variability and can replicate normal and osteoporotic bone. In planning the physical testing, the critical mechanical variables involved in answering the research question must be identified and due consideration given to deciding how best to measure them. Another important issue that arises relates to whether or not single static loadings will suffice in the testing (eg, to study construct stiffness) or whether cyclic dynamic testing is necessary (eg, to study late failure likely attributable to fatigue). To summarize, experimental design should be carefully planned before initiating mechanical testing. Sample size calculations should be performed to ensure adequate power and that clinically relevant differences can be detected. This pregame analysis can save significant time and cost and greatly increase the likelihood that the results will advance knowledge.

Natural variability of biochemical biomarkers in the macro-zoobenthos: Dependence on life stage and environmental factors.

PubMed

Scarduelli, Lucia; Giacchini, Roberto; Parenti, Paolo; Migliorati, Sonia; Di Brisco, Agnese Maria; Vighi, Marco

2017-11-01

Biomarkers are widely used in ecotoxicology as indicators of exposure to toxicants. However, their ability to provide ecologically relevant information remains controversial. One of the major problems is understanding whether the measured responses are determined by stress factors or lie within the natural variability range. In a previous work, the natural variability of enzymatic levels in invertebrates sampled in pristine rivers was proven to be relevant across both space and time. In the present study, the experimental design was improved by considering different life stages of the selected taxa and by measuring more environmental parameters. The experimental design considered sampling sites in 2 different rivers, 8 sampling dates covering the whole seasonal cycle, 4 species from 3 different taxonomic groups (Plecoptera, Perla grandis; Ephemeroptera, Baetis alpinus and Epeorus alpicula; Tricoptera, Hydropsyche pellucidula), different life stages for each species, and 4 enzymes (acetylcholinesterase, glutathione S-transferase, alkaline phosphatase, and catalase). Biomarker levels were related to environmental (physicochemical) parameters to verify any kind of dependence. Data were statistically elaborated using hierarchical multilevel Bayesian models. Natural variability was found to be relevant across both space and time. The results of the present study proved that care should be paid when interpreting biomarker results. Further research is needed to better understand the dependence of the natural variability on environmental parameters. Environ Toxicol Chem 2017;36:3158-3167. © 2017 SETAC. © 2017 SETAC.

Merits and limitations of optimality criteria method for structural optimization

NASA Technical Reports Server (NTRS)

Patnaik, Surya N.; Guptill, James D.; Berke, Laszlo

1993-01-01

The merits and limitations of the optimality criteria (OC) method for the minimum weight design of structures subjected to multiple load conditions under stress, displacement, and frequency constraints were investigated by examining several numerical examples. The examples were solved utilizing the Optimality Criteria Design Code that was developed for this purpose at NASA Lewis Research Center. This OC code incorporates OC methods available in the literature with generalizations for stress constraints, fully utilized design concepts, and hybrid methods that combine both techniques. Salient features of the code include multiple choices for Lagrange multiplier and design variable update methods, design strategies for several constraint types, variable linking, displacement and integrated force method analyzers, and analytical and numerical sensitivities. The performance of the OC method, on the basis of the examples solved, was found to be satisfactory for problems with few active constraints or with small numbers of design variables. For problems with large numbers of behavior constraints and design variables, the OC method appears to follow a subset of active constraints that can result in a heavier design. The computational efficiency of OC methods appears to be similar to some mathematical programming techniques.

Trauma systems and the costs of trauma care.

PubMed Central

Goldfarb, M G; Bazzoli, G J; Coffey, R M

1996-01-01

OBJECTIVE. This study examines the cost of providing trauma services in trauma centers organized by publicly administered trauma systems, compared to hospitals not part of a formal trauma system. DATA SOURCES AND STUDY SETTING. Secondary administrative discharge abstracts for a national sample of severely injured trauma patients in 44 trauma centers and 60 matched control hospitals for the year 1987 were used. STUDY DESIGN. Retrospective univariate and multivariate analyses were conducted to examine the impact of formal trauma systems and trauma center designation on the costs of treating trauma patients. Key dependent variables included length of stay, charge per day per patient, and charge per hospital stay. Key impact variables were type of trauma system and level of trauma designation. Control variables included patient, hospital, and community characteristics. DATA COLLECTION/EXTRACTION METHODS. Data were selected for hospitals based on (1) a large national hospital discharge database, the Hospital Cost and Utilization Project, 1980-1987 (HCUP-2) and (2) a special survey of trauma systems and trauma designation undertaken by the Hospital Research and Educational Trust of the American Hospital Association. PRINCIPAL FINDINGS. The results show that publicly designated Level I trauma centers, which are the focal point of most trauma systems, have the highest charge per case, the highest average charge per day, and similar or longer average lengths of stay than other hospitals. These findings persist after controlling for patient injury and health status, and for demographic characteristics and hospital and community characteristics. CONCLUSIONS. Prior research shows that severely injured trauma patients have greater chances of survival when treated in specialized trauma centers. However, findings here should be of concern to the many states developing trauma systems since the high costs of Level I centers support limiting the number of centers designated at this level and/or reconsidering the requirements placed on these centers. PMID:8617611

The Attributes of a Variable-Diameter Rotor System Applied to Civil Tiltrotor Aircraft

NASA Technical Reports Server (NTRS)

Brender, Scott; Mark, Hans; Aguilera, Frank

1996-01-01

The attributes of a variable diameter rotor concept applied to civil tiltrotor aircraft are investigated using the V/STOL aircraft sizing and performance computer program (VASCOMP). To begin, civil tiltrotor viability issues that motivate advanced rotor designs are discussed. Current work on the variable diameter rotor and a theoretical basis for the advantages of the rotor system are presented. The size and performance of variable diameter and conventional tiltrotor designs for the same baseline mission are then calculated using a modified NASA Ames version of VASCOMP. The aircraft are compared based on gross weight, fuel required, engine size, and autorotative performance for various hover disk loading values. Conclusions about the viability of the resulting designs are presented and a program for further variable diameter rotor research is recommended.

Teaching Gene Technology in an Outreach Lab: Students' Assigned Cognitive Load Clusters and the Clusters' Relationships to Learner Characteristics, Laboratory Variables, and Cognitive Achievement

ERIC Educational Resources Information Center

Scharfenberg, Franz-Josef; Bogner, Franz X.

2013-01-01

This study classified students into different cognitive load (CL) groups by means of cluster analysis based on their experienced CL in a gene technology outreach lab which has instructionally been designed with regard to CL theory. The relationships of the identified student CL clusters to learner characteristics, laboratory variables, and…

Solar diameter measurements for study of Sun climate coupling

NASA Technical Reports Server (NTRS)

Hill, H. A.

1981-01-01

Variability in solar shape and diameters was examined as a possible probe of an important climatic driving function, solar luminosity variability. The techniques and facilities developed for measuring the solar diameter were used. The observing program and the requisite data reduction were conducted simultaneously. The development of a technique to calibrate the scale in the telescope field progressed to the design and construction phase.

Vocational Interest as a Correlate of Re-Entry of Girls into School in Edo State, Nigeria: Implications for Counselling

ERIC Educational Resources Information Center

Alika, Ijeoma Henrietta; Egbochuku, Elizabeth Omotunde

2012-01-01

The study investigated the relationship between vocational interest socio-economic status and re-entry of girls into school in Edo State. The research design adopted was correlational because it sought to establish the relationship between the independent variable and the dependent variable. A sample size of 306 girls who re-enrolled in institutes…

Examination of the Mathematical Problem-Solving Beliefs and Success Levels of Primary School Teacher Candidates through the Variables of Mathematical Success and Gender

ERIC Educational Resources Information Center

Bal, Ayten Pinar

2015-01-01

The aim of this study is to examine the mathematical problem-solving beliefs and problem-solving success levels of primary school teacher candidates through the variables of academic success and gender. The research was designed according to the mixed methods technique in which qualitative and quantitative methods are used together. The working…

Segmented Polynomial Models in Quasi-Experimental Research.

ERIC Educational Resources Information Center

Wasik, John L.

1981-01-01

The use of segmented polynomial models is explained. Examples of design matrices of dummy variables are given for the least squares analyses of time series and discontinuity quasi-experimental research designs. Linear combinations of dummy variable vectors appear to provide tests of effects in the two quasi-experimental designs. (Author/BW)

[Methodological design for the National Survey Violence Against Women in Mexico].

PubMed

Olaiz, Gustavo; Franco, Aurora; Palma, Oswaldo; Echarri, Carlos; Valdez, Rosario; Herrera, Cristina

2006-01-01

To describe the methodology, the research designs used, the estimation and sample selection, variable definitions, collection instruments, and operative design and analytical procedures for the National Survey Violence Against Women in Mexico. A complex (two-step) cross-sectional study was designed and the qualitative design was carried out using in-depth interviews and participant observation in health care units. We obtained for the quantitative study a total of 26 240 interviews in women users of health services and 2 636 questionnaires for health workers; the survey is representative of the 32 Mexican states. For the qualitative study 26 in-depth interviews were conducted with female users and 60 interviews with health workers in the States of Quintana Roo, Coahuila and the Federal District.

Tetrafluoroethane (R134a) hydrate formation within variable volume reactor accompanied by evaporation and condensation.

PubMed

Jeong, K; Choo, Y S; Hong, H J; Yoon, Y S; Song, M H

2015-03-01

Vast size hydrate formation reactors with fast conversion rate are required for the economic implementation of seawater desalination utilizing gas hydrate technology. The commercial target production rate is order of thousand tons of potable water per day per train. Various heat and mass transfer enhancement schemes including agitation, spraying, and bubbling have been examined to maximize the production capacities in scaled up design of hydrate formation reactors. The present experimental study focused on acquiring basic knowledge needed to design variable volume reactors to produce tetrafluoroethane hydrate slurry. Test vessel was composed of main cavity with fixed volume of 140 ml and auxiliary cavity with variable volume of 0 ∼ 64 ml. Temperatures at multiple locations within vessel and pressure were monitored while visual access was made through front window. Alternating evaporation and condensation induced by cyclic volume change provided agitation due to density differences among water and vapor, liquid and hydrate R134a as well as extended interface area, which improved hydrate formation kinetics coupled with latent heat release and absorption. Influences of coolant temperature, piston stroke/speed, and volume change period on hydrate formation kinetics were investigated. Suggestions of reactor design improvement for future experimental study are also made.

Tetrafluoroethane (R134a) hydrate formation within variable volume reactor accompanied by evaporation and condensation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeong, K.; Choo, Y. S.; Hong, H. J.

Vast size hydrate formation reactors with fast conversion rate are required for the economic implementation of seawater desalination utilizing gas hydrate technology. The commercial target production rate is order of thousand tons of potable water per day per train. Various heat and mass transfer enhancement schemes including agitation, spraying, and bubbling have been examined to maximize the production capacities in scaled up design of hydrate formation reactors. The present experimental study focused on acquiring basic knowledge needed to design variable volume reactors to produce tetrafluoroethane hydrate slurry. Test vessel was composed of main cavity with fixed volume of 140 mlmore » and auxiliary cavity with variable volume of 0 ∼ 64 ml. Temperatures at multiple locations within vessel and pressure were monitored while visual access was made through front window. Alternating evaporation and condensation induced by cyclic volume change provided agitation due to density differences among water and vapor, liquid and hydrate R134a as well as extended interface area, which improved hydrate formation kinetics coupled with latent heat release and absorption. Influences of coolant temperature, piston stroke/speed, and volume change period on hydrate formation kinetics were investigated. Suggestions of reactor design improvement for future experimental study are also made.« less

Modulation of brain activity by multiple lexical and word form variables in visual word recognition: A parametric fMRI study.

PubMed

Hauk, Olaf; Davis, Matthew H; Pulvermüller, Friedemann

2008-09-01

Psycholinguistic research has documented a range of variables that influence visual word recognition performance. Many of these variables are highly intercorrelated. Most previous studies have used factorial designs, which do not exploit the full range of values available for continuous variables, and are prone to skewed stimulus selection as well as to effects of the baseline (e.g. when contrasting words with pseudowords). In our study, we used a parametric approach to study the effects of several psycholinguistic variables on brain activation. We focussed on the variable word frequency, which has been used in numerous previous behavioural, electrophysiological and neuroimaging studies, in order to investigate the neuronal network underlying visual word processing. Furthermore, we investigated the variable orthographic typicality as well as a combined variable for word length and orthographic neighbourhood size (N), for which neuroimaging results are still either scarce or inconsistent. Data were analysed using multiple linear regression analysis of event-related fMRI data acquired from 21 subjects in a silent reading paradigm. The frequency variable correlated negatively with activation in left fusiform gyrus, bilateral inferior frontal gyri and bilateral insulae, indicating that word frequency can affect multiple aspects of word processing. N correlated positively with brain activity in left and right middle temporal gyri as well as right inferior frontal gyrus. Thus, our analysis revealed multiple distinct brain areas involved in visual word processing within one data set.

Design, innovation, and rural creative places: Are the arts the cherry on top, or the secret sauce?

PubMed

Wojan, Timothy R; Nichols, Bonnie

2018-01-01

Creative class theory explains the positive relationship between the arts and commercial innovation as the mutual attraction of artists and other creative workers by an unobserved creative milieu. This study explores alternative theories for rural settings, by analyzing establishment-level survey data combined with data on the local arts scene. The study identifies the local contextual factors associated with a strong design orientation, and estimates the impact that a strong design orientation has on the local economy. Data on innovation and design come from a nationally representative sample of establishments in tradable industries. Latent class analysis allows identifying unobserved subpopulations comprised of establishments with different design and innovation orientations. Logistic regression allows estimating the association between an establishment's design orientation and local contextual factors. A quantile instrumental variable regression allows assessing the robustness of the logistic regression results with respect to endogeneity. An estimate of design orientation at the local level derived from the survey is used to examine variation in economic performance during the period of recovery from the Great Recession (2010-2014). Three distinct innovation (substantive, nominal, and non-innovators) and design orientations (design-integrated, "design last finish," and no systematic approach to design) are identified. Innovation- and design-intensive establishments were identified in both rural and urban areas. Rural design-integrated establishments tended to locate in counties with more highly educated workforces and containing at least one performing arts organization. A quantile instrumental variable regression confirmed that the logistic regression result is robust to endogeneity concerns. Finally, rural areas characterized by design-integrated establishments experienced faster growth in wages relative to rural areas characterized by establishments using no systematic approach to design.

Design, innovation, and rural creative places: Are the arts the cherry on top, or the secret sauce?

PubMed Central

Nichols, Bonnie

2018-01-01

Objective Creative class theory explains the positive relationship between the arts and commercial innovation as the mutual attraction of artists and other creative workers by an unobserved creative milieu. This study explores alternative theories for rural settings, by analyzing establishment-level survey data combined with data on the local arts scene. The study identifies the local contextual factors associated with a strong design orientation, and estimates the impact that a strong design orientation has on the local economy. Method Data on innovation and design come from a nationally representative sample of establishments in tradable industries. Latent class analysis allows identifying unobserved subpopulations comprised of establishments with different design and innovation orientations. Logistic regression allows estimating the association between an establishment’s design orientation and local contextual factors. A quantile instrumental variable regression allows assessing the robustness of the logistic regression results with respect to endogeneity. An estimate of design orientation at the local level derived from the survey is used to examine variation in economic performance during the period of recovery from the Great Recession (2010–2014). Results Three distinct innovation (substantive, nominal, and non-innovators) and design orientations (design-integrated, “design last finish,” and no systematic approach to design) are identified. Innovation- and design-intensive establishments were identified in both rural and urban areas. Rural design-integrated establishments tended to locate in counties with more highly educated workforces and containing at least one performing arts organization. A quantile instrumental variable regression confirmed that the logistic regression result is robust to endogeneity concerns. Finally, rural areas characterized by design-integrated establishments experienced faster growth in wages relative to rural areas characterized by establishments using no systematic approach to design. PMID:29489884

Adult Lifespan Cognitive Variability in the Cross-Sectional Cam-CAN Cohort

PubMed Central

Green, Emma; Shafto, Meredith A.; Matthews, Fiona E.; White, Simon R.

2015-01-01

This study examines variability across the age span in cognitive performance in a cross-sectional, population-based, adult lifespan cohort from the Cambridge Centre for Ageing and Neuroscience (Cam-CAN) study (n = 2680). A key question we highlight is whether using measures that are designed to detect age-related cognitive pathology may not be sensitive to, or reflective of, individual variability among younger adults. We present three issues that contribute to the debate for and against age-related increases in variability. Firstly, the need to formally define measures of central tendency and measures of variability. Secondly, in addition to the commonly addressed location-confounding (adjusting for covariates) there may exist changes in measures of variability due to confounder sub-groups. Finally, that increases in spread may be a result of floor or ceiling effects; where the measure is not sensitive enough at all ages. From the Cam-CAN study, a large population-based dataset, we demonstrate the existence of variability-confounding for the immediate episodic memory task; and show that increasing variance with age in our general cognitive measures is driven by a ceiling effect in younger age groups. PMID:26690191

Adult Lifespan Cognitive Variability in the Cross-Sectional Cam-CAN Cohort.

PubMed

Green, Emma; Shafto, Meredith A; Matthews, Fiona E; White, Simon R

2015-12-07

This study examines variability across the age span in cognitive performance in a cross-sectional, population-based, adult lifespan cohort from the Cambridge Centre for Ageing and Neuroscience (Cam-CAN) study (n = 2680). A key question we highlight is whether using measures that are designed to detect age-related cognitive pathology may not be sensitive to, or reflective of, individual variability among younger adults. We present three issues that contribute to the debate for and against age-related increases in variability. Firstly, the need to formally define measures of central tendency and measures of variability. Secondly, in addition to the commonly addressed location-confounding (adjusting for covariates) there may exist changes in measures of variability due to confounder sub-groups. Finally, that increases in spread may be a result of floor or ceiling effects; where the measure is not sensitive enough at all ages. From the Cam-CAN study, a large population-based dataset, we demonstrate the existence of variability-confounding for the immediate episodic memory task; and show that increasing variance with age in our general cognitive measures is driven by a ceiling effect in younger age groups.

A Framework for Orbital Performance Evaluation in Distributed Space Missions for Earth Observation

NASA Technical Reports Server (NTRS)

Nag, Sreeja; LeMoigne-Stewart, Jacqueline; Miller, David W.; de Weck, Olivier

2015-01-01

Distributed Space Missions (DSMs) are gaining momentum in their application to earth science missions owing to their unique ability to increase observation sampling in spatial, spectral and temporal dimensions simultaneously. DSM architectures have a large number of design variables and since they are expected to increase mission flexibility, scalability, evolvability and robustness, their design is a complex problem with many variables and objectives affecting performance. There are very few open-access tools available to explore the tradespace of variables which allow performance assessment and are easy to plug into science goals, and therefore select the most optimal design. This paper presents a software tool developed on the MATLAB engine interfacing with STK, for DSM orbit design and selection. It is capable of generating thousands of homogeneous constellation or formation flight architectures based on pre-defined design variable ranges and sizing those architectures in terms of predefined performance metrics. The metrics can be input into observing system simulation experiments, as available from the science teams, allowing dynamic coupling of science and engineering designs. Design variables include but are not restricted to constellation type, formation flight type, FOV of instrument, altitude and inclination of chief orbits, differential orbital elements, leader satellites, latitudes or regions of interest, planes and satellite numbers. Intermediate performance metrics include angular coverage, number of accesses, revisit coverage, access deterioration over time at every point of the Earth's grid. The orbit design process can be streamlined and variables more bounded along the way, owing to the availability of low fidelity and low complexity models such as corrected HCW equations up to high precision STK models with J2 and drag. The tool can thus help any scientist or program manager select pre-Phase A, Pareto optimal DSM designs for a variety of science goals without having to delve into the details of the engineering design process.

Practice schedule and acquisition, retention, and transfer of a throwing task in 6-yr.-old children.

PubMed

Granda Vera, Juan; Montilla, Mariano Medina

2003-06-01

Earlier studies have raised questions about the usefulness of variable and random practice in learning motor tasks so this study was designed to investigate the effects of contextual interference in young children, and specifically to evaluate the effectiveness of variable or random practice structure in 6-yr.-old boys and girls. Participants on a variable practice schedule showed better performances than those on a blocked schedule. The differences between the two groups were significant in the acquisition, retention, and transfer phases. These results support the hypothesis that contextual interference enhances skill learning. Because the study involved groups of young children in the setting of their normally scheduled physical education class, the practical applications of the results are evident.

A plant’s perspective of extremes: Terrestrial plant responses to changing climatic variability

PubMed Central

Reyer, C.; Leuzinger, S.; Rammig, A.; Wolf, A.; Bartholomeus, R. P.; Bonfante, A.; de Lorenzi, F.; Dury, M.; Gloning, P.; Abou Jaoudé, R.; Klein, T.; Kuster, T. M.; Martins, M.; Niedrist, G.; Riccardi, M.; Wohlfahrt, G.; de Angelis, P.; de Dato, G.; François, L.; Menzel, A.; Pereira, M.

2013-01-01

We review observational, experimental and model results on how plants respond to extreme climatic conditions induced by changing climatic variability. Distinguishing between impacts of changing mean climatic conditions and changing climatic variability on terrestrial ecosystems is generally underrated in current studies. The goals of our review are thus (1) to identify plant processes that are vulnerable to changes in the variability of climatic variables rather than to changes in their mean, and (2) to depict/evaluate available study designs to quantify responses of plants to changing climatic variability. We find that phenology is largely affected by changing mean climate but also that impacts of climatic variability are much less studied but potentially damaging. We note that plant water relations seem to be very vulnerable to extremes driven by changes in temperature and precipitation and that heatwaves and flooding have stronger impacts on physiological processes than changing mean climate. Moreover, interacting phenological and physiological processes are likely to further complicate plant responses to changing climatic variability. Phenological and physiological processes and their interactions culminate in even more sophisticated responses to changing mean climate and climatic variability at the species and community level. Generally, observational studies are well suited to study plant responses to changing mean climate, but less suitable to gain a mechanistic understanding of plant responses to climatic variability. Experiments seem best suited to simulate extreme events. In models, temporal resolution and model structure are crucial to capture plant responses to changing climatic variability. We highlight that a combination of experimental, observational and /or modeling studies have the potential to overcome important caveats of the respective individual approaches. PMID:23504722

A Systematic Review on the Designs of Clinical Technology: Findings and Recommendations for Future Research

PubMed Central

PhD, Greg Alexander; Staggers, Nancy

2010-01-01

Human factors (HF) studies are increasingly important as technology infuses into clinical settings. No nursing research reviews exist in this area. The authors conducted a systematic review on designs of clinical technology, 34 articles with 50 studies met inclusion criteria. Findings were classified into three categories based on HF research goals. The majority of studies evaluated effectiveness of clinical design; efficiency was fewest. Current research ranges across many interface types examined with no apparent pattern or obvious rationale. Future research should expand types, settings, participants; integrate displays; and expand outcome variables. PMID:19707093

Method Improving Reading Comprehension In Primary Education Program Students

NASA Astrophysics Data System (ADS)

Rohana

2018-01-01

This study aims to determine the influence of reading comprehension skills of English for PGSD students through the application of SQ3R learning method. The type of this research is Pre-Experimental research because it is not yet a real experiment, there are external variables that influence the formation of a dependent variable, this is because there is no control variable and the sample is not chosen randomly. The research design is used is one-group pretest-post-test design involving one group that is an experimental group. In this design, the observation is done twice before and after the experiment. Observations made before the experiment (O1) are called pretests and the post-experimental observation (O2) is called posttest. The difference between O1 and O2 ie O2 - O1 is the effect of the treatment. The results showed that there was an improvement in reading comprehension skills of PGSD students in Class M.4.3 using SQ3R method, and better SQ3R enabling SQ3R to improve English comprehension skills.

Is protective equipment useful in preventing concussion? A systematic review of the literature.

PubMed

Benson, B W; Hamilton, G M; Meeuwisse, W H; McCrory, P; Dvorak, J

2009-05-01

To determine if there is evidence that equipment use reduces sport concussion risk and/or severity. 12 electronic databases were searched using a combination of Medical Subject Headings and text words to identify relevant articles. Specific inclusion and exclusion criteria were used to select studies for review. Data extracted included design, study population, exposure/outcome measures and results. The quality of evidence was assessed based on epidemiologic criteria regarding internal and external validity (ie, strength of design, sample size/power calculation, selection bias, misclassification bias, control of potential confounding and effect modification). In total, 51 studies were selected for review. A comparison between studies was difficult due to the variability in research designs, definition of concussion, mouthguard/helmet/headgear/face shield types, measurements used to assess exposure and outcomes, and variety of sports assessed. The majority of studies were observational, with 23 analytical epidemiologic designs related to the subject area. Selection bias was a concern in the reviewed studies, as was the lack of measurement and control for potentially confounding variables. There is evidence that helmet use reduces head injury risk in skiing, snowboarding and bicycling, but the effect on concussion risk is inconclusive. No strong evidence exists for the use of mouthguards or face shields to reduce concussion risk. Evidence is provided to suggest that full facial protection in ice hockey may reduce concussion severity, as measured by time loss from competition.

Methods to control for unmeasured confounding in pharmacoepidemiology: an overview.

PubMed

Uddin, Md Jamal; Groenwold, Rolf H H; Ali, Mohammed Sanni; de Boer, Anthonius; Roes, Kit C B; Chowdhury, Muhammad A B; Klungel, Olaf H

2016-06-01

Background Unmeasured confounding is one of the principal problems in pharmacoepidemiologic studies. Several methods have been proposed to detect or control for unmeasured confounding either at the study design phase or the data analysis phase. Aim of the Review To provide an overview of commonly used methods to detect or control for unmeasured confounding and to provide recommendations for proper application in pharmacoepidemiology. Methods/Results Methods to control for unmeasured confounding in the design phase of a study are case only designs (e.g., case-crossover, case-time control, self-controlled case series) and the prior event rate ratio adjustment method. Methods that can be applied in the data analysis phase include, negative control method, perturbation variable method, instrumental variable methods, sensitivity analysis, and ecological analysis. A separate group of methods are those in which additional information on confounders is collected from a substudy. The latter group includes external adjustment, propensity score calibration, two-stage sampling, and multiple imputation. Conclusion As the performance and application of the methods to handle unmeasured confounding may differ across studies and across databases, we stress the importance of using both statistical evidence and substantial clinical knowledge for interpretation of the study results.