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1

Optimum Building Shapes for Energy Conservation  

ERIC Educational Resources Information Center

An approach to optimum building shape design is summarized that is based on local climate and is especially important for heat control in lower cost construction with temperature-responsive thermal characteristics. The study was supported by Istanbul Technical University. For journal availability see HE 508 931. (Author/LBH)

Berkoz, Esher Balkan

1977-01-01

2

Optimum Digital Filters for GNSS Tracking Loops  

Microsoft Academic Search

In a traditional loop filter the product between loop noise bandwidth and integration time (BLT) should remain well below unity in order to ensure the stability of the loop. This constraint, required for having a stable loop, significantly limits the maximum integration time and\\/or noise bandwidth. The current methodology in designing digital tracking loop filters mostly relies on transforming a

Pejman L. Kazemi

3

Shape of cosmic string loops  

SciTech Connect

Complicated cosmic string loops will fragment until they reach simple, nonintersecting ('stable') configurations. Through extensive numerical study we characterize these attractor loop shapes including their length, velocity, kink, and cusp distributions. We find that an initial loop containing M harmonic modes will, on average, split into 3M stable loops. These stable loops are approximately described by the degenerate kinky loop, which is planar and rectangular, independently of the number of modes on the initial loop. This is confirmed by an analytic construction of a stable family of perturbed degenerate kinky loops. The average stable loop is also found to have a 40% chance of containing a cusp. We examine the properties of stable loops of different lengths and find only slight variation. Finally we develop a new analytic scheme to explicitly solve the string constraint equations.

Copi, Craig J.; Vachaspati, Tanmay [CERCA, Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7079 (United States); Physics Department, Arizona State University, Tempe, Arizona 85287 (United States)

2011-01-15

4

Optimum Patch Repair Shapes for Cracked Members  

Microsoft Academic Search

In the present paper the problem of finding the optimal patch repair shape in a cracked structural component with respect to a given objective function, is investigated by using a biological-based procedure known as Genetic Algorithm (GA) in conjunction with a penalty constraint. The search for an optimal patch shape, which can be regarded also as an optimal topology problem,

Roberto Brighenti

2004-01-01

5

Hydromechanics of swimming propulsion. Part 2. Some optimum shape problems  

Microsoft Academic Search

The optimum shape problems considered in this part are for those profiles of a two-dimensional flexible plate in time-harmonic motion that will minimize the energy loss under the condition of fixed thrust and possibly also under other isoperimetric constraints. First, the optimum movement of a rigid plate is completely determined; it is necessary first to reduce the original singular form

T. Yao-Tsu Wu

1971-01-01

6

Optimum pulse shapes for stimulated Raman adiabatic passage  

NASA Astrophysics Data System (ADS)

Stimulated Raman adiabatic passage (STIRAP) driven with pulses of optimum shape and delay has the potential of reaching fidelities high enough to make it suitable for quantum-information processing. The optimum pulse shapes are obtained upon reduction of STIRAP to effective two-state systems. We use the Dykhne-Davis-Pechukas (DDP) method to minimize nonadiabatic transitions and to maximize the fidelity of STIRAP. This results in a particular relation between the pulse shapes of the two fields driving the Raman process. The DDP-optimized version of STIRAP maintains its robustness against variations in the pulse intensities and durations, the single-photon detuning, and possible losses from the intermediate state.

Vasilev, G. S.; Kuhn, A.; Vitanov, N. V.

2009-07-01

7

Automatic Weight Selection in H? Loop Shaping Using Genetic Algorithm  

Microsoft Academic Search

A genetic-algorithm (GA) based strategy is presented for suitable weight selection in H? loop shaping. The loop shaping is currently performed manually and usually a trial and error method. To solve this problem an automatic loop-shaping method based on GAs is introduced and air vehicle example is used to examine the performance of the proposed automatic loop shaping. A classical

Muhammad Ejaz; M. Naeem Arbab

2006-01-01

8

Beyond singular values and loop shapes  

NASA Technical Reports Server (NTRS)

The status of singular value loop-shaping as a design paradigm for multivariable feedback systems is reviewed. It shows that this paradigm is an effective design tool whenever the problem specifications are spacially round. The tool can be arbitrarily conservative, however, when they are not. This happens because singular value conditions for robust performance are not tight (necessary and sufficient) and can severely overstate actual requirements. An alternate paradign is discussed which overcomes these limitations. The alternative includes a more general problem formulation, a new matrix function mu, and tight conditions for both robust stability and robust performance. The state of the art currently permits analysis of feedback systems within this new paradigm. Synthesis remains a subject of research.

Stein, G.

1985-01-01

9

Size influence on shape of handwritten characters loops.  

PubMed

In the practice of forensic handwriting experts, the size of the writing on a questioned document may be different from that of known samples. In this study, the hypothesis of shape invariance of handwritten closed loops across size increasing was tested. A Fourier methodology was applied to 2325 small letters (591 a loops, 547 d loops, 596 o loops and 591 q loops) and 692 enlarged letters (162 a loops, 173 d loops, 173 o loops and 184 q loops), in a population of 13 writers who were asked to write letters in their usual size and about three times larger. Most of the writers presented similar modifications when increasing the size of the loops; they produced enlarged loops significantly more round and less slanted towards the right or the left. Furthermore, a discrimination was demonstrated between the writers on the basis of the enlarged loops, with a correct classification rate superior to 90%, whatever the letter (a, d, o or q). A classification of the enlarged loops in their corresponding writer was then possible. On the contrary, when comparing the enlarged loops to the small ones, almost one half of the enlarged loops were allocated to a wrong writer. Shape invariance was thus not supported for this particular application. Consequently, when comparing documents with a different writing size, differences in loops shape should be interpreted cautiously because they may be due to a different writer, but they may also be due to an enlargement of the loops. Therefore, reference material of similar writing size to that of the questioned writing should be requested for the comparison of handwritten loops. PMID:17207594

Marquis, R; Taroni, F; Bozza, S; Schmittbuhl, M

2007-10-01

10

Optimum Shape Design Using Automatic Differentiation in Reverse Mode  

NASA Technical Reports Server (NTRS)

This paper shows how to use automatic differentiation in reverse mode as a powerful tool in optimization procedures. It is also shown that for aerodynamic applications the gradients have to be as accurate as possible. In particular, the effect of having the exact gradient of he first or second order spatial discretization schemes is presented. We show that the loss of precision in the gradient affects not only the convergence, but also the final shape. Both two and three dimensional configurations of transonic and supersonic flows have been investigated. These cases involve up to several thousand control parameters.

Hafez, M.; Mohammadi, B.; Pironneau, O.

1996-01-01

11

Feedback Loops Shape Cellular Signals in Space and Time  

PubMed Central

Positive and negative feedback loops are common regulatory elements in biological signaling systems. We discuss core feedback motifs that have distinct roles in shaping signaling responses in space and time. We also discuss approaches to experimentally investigate feedback loops in signaling systems.

Brandman, Onn; Meyer, Tobias

2009-01-01

12

NON-LINEAR FREQUENCY DOMAIN BASED OPTIMUM SHAPE DESIGN FOR UNSTEADY THREE-DIMENSIONAL FLOWS  

Microsoft Academic Search

This paper presents an adjoint method for the optimum shape design of unsteady flows. The goal is to develop a set of discrete unsteady adjoint equations and the corresponding boundary condition for the non-linear frequency domain method. First, this paper presents the complete formulation of the time dependent optimal design problem. Second, we present the non-linear frequency domain adjoint equations

Siva K. Nadarajah; Matthew S. McMullen; Antony Jameson

2006-01-01

13

Measuring Shape-Dependent Looping Probability of DNA  

PubMed Central

Recently, several studies have shown that short doubled-stranded DNA (dsDNA) loops more readily than the wormlike chain model predicts. In most of these experiments, the intrinsic bendedness of dsDNA, which in theory can dramatically influence looping dynamics, was either avoided or unaccounted for. To investigate the effect of the shape of dsDNA on looping dynamics, we characterized the shapes of several synthetic dsDNA molecules of equal length but different sequences using gel electrophoresis. We then measured their looping rates using a FRET (Förster resonance energy transfer)-based assay and extracted the looping probability density known as the J factor (jM). We also used, for comparison, several dinucleotide angular parameter sets derived from the observed electrophoretic mobility to compute the jM predicted by the wormlike chain model. Although we found a strong correlation between curvature and jM, the measured jM was higher than most dinucleotide model predictions. This result suggests that it is difficult to reconcile the looping probability with the observed gel mobility within the wormlike chain model and underscores the importance of determining the intrinsic shape of dsDNA for proper theoretical analysis.

Le, Tung T.; Kim, Harold D.

2013-01-01

14

Loop shaping design for tracking performance in machine axes  

Microsoft Academic Search

A modern interpretation of classical loop shaping control design methods is presented in the context of tracking control for linear motor stages. Target applications include noncontacting machines such as laser cutters and markers, water jet cutters, and adhesive applicators. The methods are directly applicable to the common PID controller and are pertinent to many electromechanical servo actuators other than linear

Dale E. Schinstock; Zhouhong Wei; Tao Yang

2006-01-01

15

A study of the optimum field emitter shape for vacuum electronics applications  

NASA Astrophysics Data System (ADS)

A summary of a study on optimum field emitter models is introduced in this paper. Ten models of field emitter are presented and the electric field on the top of these field emitters in the given structure of triode are calculated using EMAS software. It is seen that sharp pyramid-on-post is the best shape of field emitter due to high field enhancement, reasonable mechanical stability and thermal contact, low capacitance and high transconductance.

Wang, Bao Ping; Tong, Linsu

1996-03-01

16

Wall shape optimization for a thermosyphon loop featuring corrugated pipes  

NASA Astrophysics Data System (ADS)

In the present paper we address the problem of optimal wall-shape design of a single phase laminar thermosyphon loop. The model takes the buoyancy forces into account via the Boussinesq approximation. We focus our study on showing the effects of wall shape on the flow and on the temperature inside the thermosyphon. To this extend we determine the dependency of the flow rate and the increase in temperature, on the geometrical characteristics of the loop. The geometry considered is a set of axially symmetric corrugated pipes described by a set of parameters; namely the pipe inner radius, the period of the corrugation, the amplitude of the corrugation, and the ratio of expansion and contraction regions of a period of the pipe. The governing equations are solved using the Finite Element Method, in combination with an adaptive mesh refinement technique in order to capture the effects of wall shape. We characterize the effects of the amplitude and of the ratio of expansion and contraction. In particular we show that for a given fixed amplitude it is possible to find an optimal ratio of expansion and contraction that minimizes the temperature inside the thermosyphon. The results show that by adequately choosing the design parameters, the performance of the thermosyphon loop can be improved.

Rosen Esquivel, Patricio I.; ten Thije Boonkkamp, Jan H. M.; Dam, Jacques A. M.; Mattheij, Robert M. M.

2012-06-01

17

Optimum shape control of flexible beams by piezo-electric actuators  

NASA Technical Reports Server (NTRS)

The utilization of piezoelectric actuators in controlling the static deformation and shape of flexible beams is examined. An optimum design procedure is presented to enable the selection of the optimal location, thickness and excitation voltage of the piezoelectric actuators in a way that would minimize the deflection of the beam to which these actuators are bonded. Numerical examples are presented to illustrate the application of the developed optimization procedure in minimizing structural deformation of beams using ceramic and polymeric piezoelectric actuators bonded to the beams with a typical bonding agent. The obtained results emphasize the importance of the devised rational produce in designing beam-actuator systems with minimal elastic distortions.

Baz, A.; Poh, S.

1987-01-01

18

Optimum mirror shapes and supports for light weight mirrors subjected to self-weight  

NASA Astrophysics Data System (ADS)

A parametric design study of light weight mirror shapes with various support conditions was performed utilizing the finite element program NASTRAN. Improvements in the mirror performance were made based on the following design criteria: (1) minimization of the optical surface wavefront variations, (2) minimization of the self-weight directly related to cost of manufacturing, and (3) optimal location of support points. A preprocessor to automatically generate a finite element model for each mirror geometry was developed in order to obtain the structural deformations systematically. Additionally, a postprocessor, which prepares an input data file for FRINGE (an optical computer code) was developed for generating the optical deflections that lead to the surface wavefront variations. Procedures and modeling techniques to achieve the optimum (the lightest and stiffest mirror shape due to self-weight) are addressed.

Cho, Myung K.; Richard, Ralph M.; Vukobratovich, Daniel

1989-11-01

19

{alpha}-Shaped DNA loops induced by MutS  

SciTech Connect

DNA mismatch repair (MMR) is critical for the maintenance of genomic stability. MMR is initiated by recognition of DNA mismatches by the protein, MutS, which subsequently recruits downstream repair factors. To better understand the mechanism by which MutS identifies and specifically binds mismatched basepairs embedded in random DNA sequences, we monitored the interaction between MutS and DNA substrates using atomic force microscopy (AFM). An {alpha}-shaped DNA loop formed by the interaction between MutS and DNA, which was independent of whether or not a mismatch was present in the DNA substrate. These data indicate that MutS associates with DNA non-specifically and forms an {alpha}-loop interaction with the DNA substrate. In this conformation, MutS is able to scan two arms of DNA simultaneously for each MutS dimer formed.

Jia Yanxia [National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101 (China); State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071 (China); Shenyang Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110015 (China); Graduate School, Chinese Academy of Sciences, Beijing (China); Bi Lijun; Li Feng; Chen Yuanyuan [National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101 (China); Zhang Chenggang [Shenyang Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110015 (China); Zhang Xianen [State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071 (China)], E-mail: Zhangxe@sun5.ibp.ac.cn

2008-08-08

20

Loop shaping design for tracking performance in machine axes.  

PubMed

A modern interpretation of classical loop shaping control design methods is presented in the context of tracking control for linear motor stages. Target applications include noncontacting machines such as laser cutters and markers, water jet cutters, and adhesive applicators. The methods are directly applicable to the common PID controller and are pertinent to many electromechanical servo actuators other than linear motors. In addition to explicit design techniques a PID tuning algorithm stressing the importance of tracking is described. While the theory behind these techniques is not new, the analysis of their application to modern systems is unique in the research literature. The techniques and results should be important to control practitioners optimizing PID controller designs for tracking and in comparing results from classical designs to modern techniques. The methods stress high-gain controller design and interpret what this means for PID. Nothing in the methods presented precludes the addition of feedforward control methods for added improvements in tracking. Laboratory results from a linear motor stage demonstrate that with large open-loop gain very good tracking performance can be achieved. The resultant tracking errors compare very favorably to results from similar motions on similar systems that utilize much more complicated controllers. PMID:16480110

Schinstock, Dale E; Wei, Zhouhong; Yang, Tao

2006-01-01

21

Optimum Frequency for Inductively Coupled Plasma Generation with a SingleLoop Antenna  

Microsoft Academic Search

The frequency dependence of the inductively coupled plasma is experimentally studied using a single-loop antenna. In particular the transition from the capacitive to the inductive coupling mode is examined for the frequencies from 13 to 60 MHz. The results show that the frequency at which the transition from the capacitive to the inductive mode appears at the lowest power is

Kouta Kusaba; Yuichi Kitamura; Haruo Shindo

2007-01-01

22

Practical Loop-Shaping Design of Feedback Control Systems  

NASA Technical Reports Server (NTRS)

An improved methodology for designing feedback control systems has been developed based on systematically shaping the loop gain of the system to meet performance requirements such as stability margins, disturbance attenuation, and transient response, while taking into account the actuation system limitations such as actuation rates and range. Loop-shaping for controls design is not new, but past techniques do not directly address how to systematically design the controller to maximize its performance. As a result, classical feedback control systems are designed predominantly using ad hoc control design approaches such as proportional integral derivative (PID), normally satisfied when a workable solution is achieved, without a good understanding of how to maximize the effectiveness of the control design in terms of competing performance requirements, in relation to the limitations of the plant design. The conception of this improved methodology was motivated by challenges in designing control systems of the types needed for supersonic propulsion. But the methodology is generally applicable to any classical control-system design where the transfer function of the plant is known or can be evaluated. In the case of a supersonic aerospace vehicle, a major challenge is to design the system to attenuate anticipated external and internal disturbances, using such actuators as fuel injectors and valves, bypass doors, and ramps, all of which are subject to limitations in actuator response, rates, and ranges. Also, for supersonic vehicles, with long slim type of structures, coupling between the engine and the structural dynamics can produce undesirable effects that could adversely affect vehicle stability and ride quality. In order to design distributed controls that can suppress these potential adverse effects, within the full capabilities of the actuation system, it is important to employ a systematic control design methodology such as this that can maximize the effectiveness of the control design in a methodical and quantifiable way. The emphasis is in generating simple but rather powerful design techniques that will allow even designers with a layman s knowledge in controls to develop effective feedback control designs. Unlike conventional ad hoc methodologies of feedback control design, in this approach actuator rates are incorporated into the design right from the start: The relation between actuator speeds and the desired control bandwidth of the system is established explicitly. The technique developed is demonstrated via design examples in a step-by-step tutorial way. Given the actuation system rates and range limits together with design specifications in terms of stability margins, disturbance rejection, and transient response, the procedure involves designing the feedback loop gain to meet the requirements and maximizing the control system effectiveness, without exceeding the actuation system limits and saturating the controller. Then knowing the plant transfer function, the procedure involves designing the controller so that the controller transfer function together with the plant transfer function equate to the designed loop gain. The technique also shows what the limitations of the controller design are and how to trade competing design requirements such as stability margins and disturbance rejection. Finally, the technique is contrasted against other more familiar control design techniques, like PID control, to show its advantages.

Kopasakis, George

2010-01-01

23

Weight Selection in H-? Loop Shaping Using Lead\\/Lag Compensators  

Microsoft Academic Search

In this paper a systematic approach for weight selection has been applied. A classical phase lead compensator is used as weight (precompensator) in Hinfin loop shaping for design of pitch controller for air vehicle. Analysis has been confined only to bode plots. The analysis and results achieved indicate that Hinfin loop shaping control theory is a viable tool for design

Muhammad Ejaz; M. Naeem Arbab; S. Waqar Shah

2006-01-01

24

Role of measurement voltage on hysteresis loop shape in Piezoresponse Force Microscopy  

SciTech Connect

The dependence of on-field and off-field hysteresis loop shape in Piezoresponse Force Microscopy (PFM) on driving voltage, Vac, is explored. A nontrivial dependence of hysteresis loop parameters on measurement conditions is observed. The strategies to distinguish between paraelectric and ferroelectric states with small coercive bias and separate reversible hysteretic and non-hysteretic behaviors are suggested. Generally, measurement of loop evolution with Vac is a necessary step to establish the veracity of PFM hysteresis measurements.

Kim, Yunseok [ORNL; Yang, J.-C. [University of California, Berkeley; Chu, Ying Hao [National Chiao Tung University, Hsinchu, Taiwan; Yu, Pu [University of California, Berkeley; Lu, X. [Xidian University, China; Jesse, Stephen [ORNL; Kalinin, Sergei V [ORNL

2012-01-01

25

Domain Nucleation and Hysteresis Loop Shape in Piezoresponse Force Spectroscopy  

SciTech Connect

Electromechanical hysteresis loop measurements in piezoresponse force microscopy (PFM) [piezoresponse force spectroscopy (PFS)] have emerged as a powerful technique for probing ferroelectric switching behavior on the nanoscale. Interpretation of PFS data requires the relationship between the domain parameters and PFM signal to be established. Here, the authors analyze the switching process using modified point charge model. The charge parameters are selected to reproduce tip-induced surface potential and tip radius of curvature. The relationship between geometric parameters of semiellipsoidal domain and PFM signal is derived using linear Green's function theory. The role of domain nucleation on hysteresis loop is established.

Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine; Eliseev, E. A. [National Academy of Science of Ukraine, Kiev, Ukraine; Kalinin, Sergei V [ORNL

2006-01-01

26

Segmented shape memory alloy actuators using hysteresis loop control  

Microsoft Academic Search

A new approach to the design and control of shape memory alloy (SMA) actuators is presented. SMA wires are divided into many segments and their thermal states are controlled individually as a group of finite state machines. Instead of driving a current to the entire SMA wire and controlling the wire length based on the analog strain-temperature characteristics, the new

Brian Selden; Kyujin Cho; H. Harry Asada

2006-01-01

27

A V-shaped structure for improving the directional properties of the loop antenna  

Microsoft Academic Search

A V-shaped wire-loop antenna with a butterfly-like structure is proposed in this paper. The antenna consists of two identical half-loops inclined at an angle to each other and joined together at the feed point and the point at which they meet the ground plane. The performance of the structure was evaluated analytically for included angles 90°, 120° and 150° between

Sivanand Krishnan; Le-Wei Li; Mook-Seng Leong

2005-01-01

28

Constitutive model of shape memory alloys for unidirectional loading considering inner hysteresis loops  

Microsoft Academic Search

A specimen-based macroscopic constitutive model of shape memory alloys for unidirectional loading, which is simple yet accurate and has a physical background, was derived from a grain-based microscopic model. To consider the inner hysteresis loops of a stress-strain-temperature relationship, a new inner loop model called the shift and skip model was proposed. This model is based on microscopic aspects and

Tadashige Ikeda; Florin Andrei Nae; Hisashi Naito; Yuji Matsuzaki

2004-01-01

29

The optimum shape for a rigid rotating shell enclosing an isotropic spherical planetary mass  

NASA Technical Reports Server (NTRS)

Analysis of the Dyson Sphere, an extremely advanced civilization's hypothetical construct entirely surrounding a star, shows that new stress inward to the star increases to maxima at the poles if the sphere is rotating. This is because the centrifugal force in the rotating frame of reference vanishes at zero rotational radius, which occurs at the poles. There is less of the centrifugal force at high latitudes than low to offset the star's gravity. A form is derived for a thin, rigid, rotating shell, surrounding a large pointlike mass and/or charge, which will experience the least possible net stress at every point upon it - a shape on which every point not on the shell's equator is as near as possible to being in orbit. In orbit, whose plane passes through the primary body's center of mass or of charge, F(grav), or Fg, is exactly opposite in direction to F(centrif), or Fc, and is equal in amount. At all points not on the equator, Fc will not entirely offset Fg, because of Fg's vector decomposition. However, both forces are always constrained to be equal in absolute amount everywhere on the shell, equator included. The derived shape, given by the figure of revolution around the x-axis of x = square root (y-1-72), will prove useful in large-scale space construction. Also, various engineering problems are discussed.

Covington, Tatiana

1991-01-01

30

Understanding missile autopilot design using the H? loop shaping design procedure  

Microsoft Academic Search

This paper presents different controller topologies for a missile autopilot. The controllers are based on a loop shaping design procedure due to McFarlane and Glover. The nature of the controllers obtained is discussed and a novel procedure for the selection of weights is given

Thomas J. Urban; Pete Iwaskiw; Pablo A. Iglesias

1999-01-01

31

The influence of the shape of domains on the ferroelectric hysteresis loop  

Microsoft Academic Search

Simple models of the polarization reversal in ferroelectrics with domains in the shape of either circular cylinders or parallel strips, which grow only by sideways expansion, are used to calculate the hysteresis loops and particularly the coercive field as a function of the amplitude and frequency of a sinusoidal electric field. The small differences in results corresponding to various models

Jiri Janta

1971-01-01

32

A hybrid multi-loop genetic-algorithm/simplex/spatial-grid method for locating the optimum orientation of an adsorbed protein on a solid surface  

NASA Astrophysics Data System (ADS)

Atomistic simulation of protein adsorption on a solid surface in aqueous environment is computationally demanding, therefore the determination of preferred protein orientations on the solid surface usually serves as an initial step in simulation studies. We have developed a hybrid multi-loop genetic-algorithm/simplex/spatial-grid method to search for low adsorption-energy orientations of a protein molecule on a solid surface. In this method, the surface and the protein molecule are treated as rigid bodies, whereas the bulk fluid is represented by spatial grids. For each grid point, an effective interaction region in the surface is defined by a cutoff distance, and the possible interaction energy between an atom at the grid point and the surface is calculated and recorded in a database. In searching for the optimum position and orientation, the protein molecule is translated and rotated as a rigid body with the configuration obtained from a previous Molecular Dynamic simulation. The orientation-dependent protein-surface interaction energy is obtained using the generated database of grid energies. The hybrid search procedure consists of two interlinked loops. In the first loop A, a genetic algorithm (GA) is applied to identify promising regions for the global energy minimum and a local optimizer with the derivative-free Nelder-Mead simplex method is used to search for the lowest-energy orientation within the identified regions. In the second loop B, a new population for GA is generated and competitive solution from loop A is improved. Switching between the two loops is adaptively controlled by the use of similarity analysis. We test the method for lysozyme adsorption on a hydrophobic hydrogen-terminated silicon (110) surface in implicit water (i.e., a continuum distance-dependent dielectric constant). The results show that the hybrid search method has faster convergence and better solution accuracy compared with the conventional genetic algorithm.

Wei, Tao; Mu, Shengjing; Nakano, Aiichiro; Shing, Katherine

2009-05-01

33

IMC-PID design based on model matching approach and closed-loop shaping.  

PubMed

Motivated by the limitations of the conventional internal model control (IMC), this communication addresses the design of IMC-based PID in terms of the robust performance of the control system. The IMC controller form is obtained by solving an H-infinity problem based on the model matching approach, and the parameters are determined by closed-loop shaping. The shaping of the closed-loop transfer function is considered both for the set-point tracking and for the load disturbance rejection. The design procedure is formulated as a multi-objective optimization problem which is solved by a specific optimization algorithm. A nice feature of this design method is that it permits a clear tradeoff between robustness and performance. Simulation examples show that the proposed method is effective and has a wide applicability. PMID:24280534

Jin, Qi B; Liu, Q

2014-03-01

34

Loading and unloading split hopkinson pressure bar pulse-shaping techniques for dynamic hysteretic loops  

Microsoft Academic Search

Pulse-shaping techniques are developed for both the loading and unloading paths of a split Hopkinson pressure bar (SHPB) experiment\\u000a to obtain valid dynamic stress-strain loops for engineering materials. Front and rear pulse-shapers, in association with a\\u000a momentum trap, are used to precisely control the profiles of the loading and unloading portions of the incident pulse. The\\u000a modifications, ensure that the

B. Song; W. Chen

2004-01-01

35

H? loop shaping based robust power system stabilizer for dynamic equivalent multi-machine power system  

Microsoft Academic Search

This paper describes a method of designing Glover-McFarlane H? loop shaping based Robust Power System Stabilizer (RPSS) for a coherency based dynamic equivalent large power system. Group of coherent generators are identified on the basis of the equal acceleration. The dynamic equivalent parameters are determined by structure preservation of the coefficient matrices in a time-domain representation of the machines. Simulink

Jayapal Reddy; Mendiratta Jugal Kishore

2010-01-01

36

Hindcasts and forecasts of Loop Current and eddies in the Gulf of Mexico using local ensemble transform Kalman filter and optimum-interpolation assimilation schemes  

NASA Astrophysics Data System (ADS)

The Local Ensemble Transform Kalman Filter (LETKF) is applied to the parallelized version of the Princeton Ocean Model to estimate the states of Loop Current and eddies in the Gulf of Mexico from April/20 to July/21, 2010 when detailed in situ current measurements were available. Tests are conducted to explore the sensitivity of the LETKF estimates to different parameters, and to systematic additions of different observational datasets which include satellite sea surface height anomaly (SSHA), satellite sea surface temperature (SST), and moored ADCP's. The results are compared against observations to assess model skills, and also against estimates based on a simpler optimum interpolation (OI) assimilation scheme. With appropriate values of parameters and observational errors, LETKF provides improved estimates of Loop Current and eddy. In particular, the Loop Current in the late spring to summer of 2010 underwent a shedding-reattachment-shedding process. It is shown that such a nonlinear behavior is more accurately captured by LETKF, but not by OI, due to the former's time-evolving error covariance. Finally, the accuracies of 8-week forecasts initialized from the OI and LETKF analyses and forced by reanalysis winds are compared. This period is particularly challenging to forecast because, instead of a more easily simulated westward propagation at approximately the first-mode baroclinic Rossby wave speed, the newly-shed eddy propagated very slowly, stalled, and finally decayed in the eastern Gulf. Both OI and LETKF beat persistence, but the LETKF significantly improves the eddy's position and strength throughout the 8-week forecast.

Xu, F.-H.; Oey, L.-Y.; Miyazawa, Y.; Hamilton, P.

2013-09-01

37

FREQ: A computational package for multivariable system loop-shaping procedures  

NASA Technical Reports Server (NTRS)

Many approaches in the field of linear, multivariable time-invariant systems analysis and controller synthesis employ loop-sharing procedures wherein design parameters are chosen to shape frequency-response singular value plots of selected transfer matrices. A software package, FREQ, is documented for computing within on unified framework many of the most used multivariable transfer matrices for both continuous and discrete systems. The matrices are evaluated at user-selected frequency-response values, and singular values against frequency. Example computations are presented to demonstrate the use of the FREQ code.

Giesy, Daniel P.; Armstrong, Ernest S.

1989-01-01

38

Closed-loop control of a shape memory alloy actuation system for variable area fan nozzle  

NASA Astrophysics Data System (ADS)

Shape Memory Alloys have been used in a wide variety of actuation applications. A bundled shape memory alloy cable actuator, capable of providing large force and displacement has been developed by United Technologies Corporation (patents pending) for actuating a Variable Area fan Nozzle (VAN). The ability to control fan nozzle exit area is an enabling technology for the next generation turbofan engines. Performance benefits for VAN engines are estimated to be up to 9% in Thrust Specific Fuel Consumption (TSFC) compared to traditional fixed geometry designs. The advantage of SMA actuated VAN design is light weight and low complexity compared to conventionally actuated designs. To achieve the maximum efficiency from a VAN engine, the nozzle exit area has to be continuously varied for a certain period of time during climb, since the optimum nozzle exit area is a function of several flight variables (flight Mach number, altitude etc). Hence, the actuator had to be controlled to provide the time varying desired nozzle area. A new control algorithm was developed for this purpose, which produced the desired flap area by metering the resistive heating of the SMA actuator. Since no active cooling was used, reducing overshoot was a significant challenge of the controller. A full scale, 2 flap model of the VAN system was built, which was capable of simulating a 20% nozzle area variation, and tested under full scale aerodynamic load in NASA Langley Jet Exit Test facility. The controller met all the requirements of the actuation system and was able to drive the flap position to the desired position with less than 2% overshoot in step input tests. The controller is based on a adaptive algorithm formulation with logical switches that reduces its overshoot error. Although the effectiveness of the controller was demonstrated in full scale model tests, no theoretical results as to its stability and robustness has been derived. Stability of the controller will have to be investigated for the next stage of technology readiness.

Barooah, Prabir; Rey, Nancy

2002-07-01

39

Robust loop shaping–fuzzy gain scheduling control of a servo-pneumatic system using particle swarm optimization approach  

Microsoft Academic Search

In this paper, a new technique called robust loop shaping–fuzzy gain scheduled control (RLS–FGS) is proposed to design an effective nonlinear controller for a long stroke pneumatic servo system. In our technique, a nonlinear dynamic model of a long stroke pneumatic servo plant is identified by the fuzzy identification method and is used as the plant for our design. The

Somyot Kaitwanidvilai; Piyapong Olranthichachat

2011-01-01

40

A novel device allowing for movement and trapping of particles within loop-shaped channels  

NASA Astrophysics Data System (ADS)

Resonant excitation of a fluid cavity inside ultrasonic particle manipulation devices leads to standing waves inside the fluid. Acoustic radiation forces, caused by the nonlinear interaction between the time harmonic pressure field and a particle can be used to manipulate particles towards the nodal or anti-nodal planes of the acoustic pressure field. This allows the contactless handling of cells, bacteria or other particles, suggesting a wide range of applications in life science and medical engineering. Most ultrasonic manipulation devices described in the literature utilize reflections at fluid-structure interfaces which create the standing wave. At a given frequency, the nodal planes are fixed since their locations are governed by the geometry of the device. This reduces the suitability of the method for applications that require contactless particle transport over long distances or towards arbitrary positions. In order to overcome the described shortcoming, several methods have been proposed. In this work we introduce a new approach, leveraging circumferential resonances within a loop-shaped fluid waveguide in order to gain full one-dimensional control over the location of nodal planes. Limitations regarding the device geometry and the enclosure materials are discussed and it is described how the position or the velocity of nodal planes can be controlled via amplitude modulation applied on two transducers. Preliminary experimental results illustrate potential applications but they also reveal problems related to the current device design.

Hahn, P.; Dual, J.

2012-05-01

41

A study of optimum cowl shapes and flow port locations for minimum drag with effective engine cooling, volume 1  

NASA Technical Reports Server (NTRS)

The contributions to the cruise drag of light aircraft arising from the shape of the engine cowl and the forward fuselage area and also that resulting from the cooling air mass flow through intake and exhaust sites on the nacelle were analyzed. The methods employed for the calculation of the potential flow about an arbitrary three dimensional body are described with modifications to include the effects of boundary layer displacement thickness, a nonuniform onset flow field (such as that due to a rotating propeller), and the presence of air intakes and exhausts. A simple, reliable, largely automated scheme to better define or change the shape of a body is also presented. A technique was developed which can yield physically acceptable skin friction and pressure drag coefficients for isolated light aircraft bodies. For test cases on a blunt nose Cessna 182 fuselage, the technique predicted drag reductions as much as 28.5% by body recontouring and proper placements and sizing of the cooling air intakes and exhausts.

Fox, S. R.; Smetana, F. O.

1980-01-01

42

The cyclic stress-strain properties, hysteresis loop shape, and kinematic hardening of two high-strength bearing steels  

Microsoft Academic Search

Measurements of the shapes of the cyclic, stress-strain hysteresis loops obtained from AISI 1070 (HRC 60) and AISI 52100 (HRC\\u000a 62) steels subjected to constant stress and constant plastic strain amplitude cycles in torsion are presented. The study examines\\u000a plastic strain amplitudes in the range of 0.0002 ? ??p\\/2? 0.0015, which are similar to the strain amplitudes produced by rolling

G. T. Hahn; V. Bhargava; Q. Chen

1990-01-01

43

Posterior Cervical Fixation with a Nitinol Shape Memory Loop for Primary Surgical Stabilization of Atlantoaxial Instability: A Preliminary Report  

PubMed Central

Objective To evaluate a new posterior atlantoaxial fixation technique using a nitinol shape memory loop as a simple method that avoids the risk of vertebral artery or nerve injury. Methods We retrospectively evaluated 14 patients with atlantoaxial instability who had undergone posterior C1-2 fusion using a nitinol shape memory loop. The success of fusion was determined clinically and radiologically. We reviewed patients' neurologic outcomes, neck disability index (NDI), solid bone fusion on cervical spine films, changes in posterior atlantodental interval (PADI), and surgical complications. Results Solid bone fusion was documented radiologically in all cases, and PADI increased after surgery (p<0.05). All patients remained neurologically intact and showed improvement in NDI score (p<0.05). There were no surgical complications such as neural tissue or vertebral artery injury or instrument failure in the follow-up period. Conclusion Posterior C1-2 fixation with a nitinol shape memory loop is a simple, less technically demanding method compared to the conventional technique and may avoid the instrument-related complications of posterior C1-2 screw and rod fixation. We introduce this technique as one of the treatment options for atlantoaxial instability.

Kim, Duk-Gyu; Park, Jung-Soo

2012-01-01

44

Shapes!  

NSDL National Science Digital Library

We will learn about shapes! Make pictures with pattern blocks! Pattern Blocks Make the shapes fit inside the picture. Tangrams Find the shapes in the picture! Shape Pictures Sort the shapes. Shape Sort Take a quiz! Shapes Quiz Take a test! Shape Test ...

Hoffmann, Mrs.

2011-09-27

45

Chirped Microwave Pulse Generation Based on Optical Spectral Shaping and Wavelength-to-Time Mapping Using a Sagnac Loop Mirror Incorporating a Chirped Fiber Bragg Grating  

Microsoft Academic Search

In this paper, we propose and demonstrate an approach to optically generating chirped microwave pulses with tunable chirp profile based on optical spectral shaping using a Sagnac loop filter incorporating a chirped fiber Bragg grating (CFBG) and linear wavelength-to-time mapping in a dispersive element. In the proposed approach, the optical power spectrum of an ultrashort optical pulse is shaped by

Chao Wang; Jianping Yao

2009-01-01

46

Loop Shaping Control Design for a Supersonic Propulsion System Model Using Quantitative Feedback Theory (QFT) Specifications and Bounds  

NASA Technical Reports Server (NTRS)

This paper covers the propulsion system component modeling and controls development of an integrated mixed compression inlet and turbojet engine that will be used for an overall vehicle Aero-Propulso-Servo-Elastic (APSE) model. Using previously created nonlinear component-level propulsion system models, a linear integrated propulsion system model and loop shaping control design have been developed. The design includes both inlet normal shock position control and jet engine rotor speed control for a potential supersonic commercial transport. A preliminary investigation of the impacts of the aero-elastic effects on the incoming flow field to the propulsion system are discussed, however, the focus here is on developing a methodology for the propulsion controls design that prevents unstart in the inlet and minimizes the thrust oscillation experienced by the vehicle. Quantitative Feedback Theory (QFT) specifications and bounds, and aspects of classical loop shaping are used in the control design process. Model uncertainty is incorporated in the design to address possible error in the system identification mapping of the nonlinear component models into the integrated linear model.

Connolly, Joseph W.; Kopasakis, George

2010-01-01

47

Determination of recovery energy densities of shape memory polymers via closed-loop, force-controlled recovery cycling  

NASA Astrophysics Data System (ADS)

Shape memory polymers offer semi-active properties, which can be used for actuation. Possible applications are deployment or release mechanisms in spacecraft, or the shape readjustment of high precision composite parts. For these kinds of applications, especially the recovered energy density, which is the product of recovered strain and recovered stress, is an important figure of merit. The present study shows the experimental procedure for the determination of recovery energy densities for tension and compression samples. To ensure simultaneous recording of loaded recovered strain and stress, closed-loop, force-controlled recovery cycles are performed using an Instron tensile testing machine and a thermal chamber. More-dimensional working fields of a polystyrene-based shape memory polymer are determined, using the introduced experimental technique. The resulting more-dimensional working fields show the nonlinear relationships between recovery ratio, maximum strain and recovery stress. It was discovered that the optimal working points of the tension and compression mode are complementary, which leads to an extended working range of SMP actuators if both modes are considered. As an application example for SMP energy recovery, a finite element simulation of the shape readjustment of a high precision composite part is shown.

Rapp, S.; Baier, H.

2010-04-01

48

H? Loop Shaping Control for Plasma Vertical Position Instability on QUEST  

NASA Astrophysics Data System (ADS)

QUEST has a divertor configuration with a high and a negative n-index, and the problem of plasma vertical position instability control in QUEST is still under extensive study for achieving high efficiency plasma. The instability we considered is that the toroidal plasma moves either up or down in the vacuum chamber until it meets the vessel wall and is extinguished. The actively controlled coils (HCU and HCL) outside the vacuum vessel are serially connected in feedback with a measurement of the plasma vertical position to provide stabilizing control. In this work, a robust controller is employed by using the loop synthesis method, and provides robust stability over a wide range of n-index. Moreover, the gain of the robust controller is lower than that of a typical proportional derivative (PD) controller in the operational frequency range; it indicates that the robust controller needs less power consumption than the PD controller does.

Liu, Xiaolong; Kazuo, Nakamura; Tatsuya, Yoshisue; Osamu, Mitarai; Makoto, Hasegawa; Kazutoshi, Tokunaga; Xue, Erbing; Hideki, Zushi; Kazuaki, Hanada; Akihide, Fujisawa; Hiroshi, Idei; Shoji, Kawasaki; Hisatoshi, Nakashima; Aki, Higashijima; Kuniaki, Araki

2013-03-01

49

One-dimensional quasistatic nonisothermal evolution of shape-memory material inside the hysteresis loop  

Microsoft Academic Search

We study in this paper the quasistatic nonisothermal processes of a onedimensional bar consisting of a two-phase shape-memory material. The system of p.d.e.'s governing the evolution of the bar is obtained by means of a temperature-dependent hysteretic stress-strain law that we formulate as a “plasticity” criterion and a hysteresis operator. The constitutive theory is developed here on the basis of

B. Fedelich; G. Zanzotto

1991-01-01

50

Hysteresis loop with controllable shape and direction in an optical ring cavity  

SciTech Connect

We have experimentally observed a 'backward' (clockwise rotating) hysteresis cycle in the system of an optical ring cavity containing three-level ({lambda}-type configuration) rubidium atoms. The shape and direction of the observed hysteresis cycles can be easily controlled with experimental parameters. Such an interesting phenomenon is caused by the greatly modified absorption, dispersion, and nonlinear optical properties of the three-level atomic medium, due to the induced atomic coherence.

Joshi, Amitabh; Yang Wenge; Xiao Min [Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States)

2004-10-01

51

Messenger RNA fluctuations and regulatory RNAs shape the dynamics of a negative feedback loop  

NASA Astrophysics Data System (ADS)

Single-cell experiments of simple regulatory networks can markedly differ from cell population experiments. Such differences arise from stochastic events in individual cells that are averaged out in cell populations. For instance, while individual cells may show sustained oscillations in the concentrations of some proteins, such oscillations may appear damped in the population average. In this paper we investigate the role of RNA stochastic fluctuations as a leading force to produce a sustained excitatory behavior at the single-cell level. As opposed to some previous models, we build a fully stochastic model of a negative feedback loop that explicitly takes into account the RNA stochastic dynamics. We find that messenger RNA random fluctuations can be amplified during translation and produce sustained pulses of protein expression. Motivated by the recent appreciation of the importance of noncoding regulatory RNAs in post-transcription regulation, we also consider the possibility that a regulatory RNA transcript could bind to the messenger RNA and repress translation. Our findings show that the regulatory transcript helps reducing gene expression variability both at the single-cell level and at the cell population level.

Rodríguez Martínez, María; Soriano, Jordi; Tlusty, Tsvi; Pilpel, Yitzhak; Furman, Itay

2010-03-01

52

Closed-loop decoder adaptation shapes neural plasticity for skillful neuroprosthetic control.  

PubMed

Neuroplasticity may play a critical role in developing robust, naturally controlled neuroprostheses. This learning, however, is sensitive to system changes such as the neural activity used for control. The ultimate utility of neuroplasticity in real-world neuroprostheses is thus unclear. Adaptive decoding methods hold promise for improving neuroprosthetic performance in nonstationary systems. Here, we explore the use of decoder adaptation to shape neuroplasticity in two scenarios relevant for real-world neuroprostheses: nonstationary recordings of neural activity and changes in control context. Nonhuman primates learned to control a cursor to perform a reaching task using semistationary neural activity in two contexts: with and without simultaneous arm movements. Decoder adaptation was used to improve initial performance and compensate for changes in neural recordings. We show that beneficial neuroplasticity can occur alongside decoder adaptation, yielding performance improvements, skill retention, and resistance to interference from native motor networks. These results highlight the utility of neuroplasticity for real-world neuroprostheses. PMID:24945777

Orsborn, Amy L; Moorman, Helene G; Overduin, Simon A; Shanechi, Maryam M; Dimitrov, Dragan F; Carmena, Jose M

2014-06-18

53

Anomalous Ferroelectric Hysteresis Loops.  

National Technical Information Service (NTIS)

Materials that exhibit anomalous ferroelectric hysteresis loops appear throughout the literature. These loops have irregular shapes that diverge from the normal hysteresis loop which is characteristic of most ferroelectrics. The observation of a unique hy...

F. J. Murdoch

1971-01-01

54

Optimised sensor selection for control and fault tolerance of electromagnetic suspension systems: a robust loop shaping approach.  

PubMed

This paper presents a systematic design framework for selecting the sensors in an optimised manner, simultaneously satisfying a set of given complex system control requirements, i.e. optimum and robust performance as well as fault tolerant control for high integrity systems. It is worth noting that optimum sensor selection in control system design is often a non-trivial task. Among all candidate sensor sets, the algorithm explores and separately optimises system performance with all the feasible sensor sets in order to identify fallback options under single or multiple sensor faults. The proposed approach combines modern robust control design, fault tolerant control, multiobjective optimisation and Monte Carlo techniques. Without loss of generality, it's efficacy is tested on an electromagnetic suspension system via appropriate realistic simulations. PMID:24041402

Michail, Konstantinos; Zolotas, Argyrios C; Goodall, Roger M

2014-01-01

55

Robust Voltage Stabilization in an Isolated Wind-Diesel Power System using PSO based-Fixed Structure H? Loop Shaping Control  

NASA Astrophysics Data System (ADS)

It is well known that the power system controller designed by H? control is complicated, high order and impractical. In power system applications, practical structures such as proportional integral derivative (PID) etc., are widely used, because of their simple structure, less number of tuning parameters and low-order. However, tuning of controller parameters to achieve a good performance and robustness is based on designer's experiences. To overcome this problem, this paper proposes a fixed structure robust H? loop shaping control to design Static Var Compensator (SVC) and Automatic Voltage Regulator (AVR) for robust stabilization of voltage fluctuation in an isolated wind-diesel hybrid power system. The structure of the robust controller of SVC and AVR is specified by a PID controller. In the system modeling, a normalized coprime factorization is applied to represent possible unstructured uncertainties in the power system such as variation of system parameters, generating and loading conditions etc. Based on the H? loop shaping, the performance and robust stability conditions are formulated as the optimization problem. The particle swarm optimization is applied to solve for PID control parameters of SVC and AVR simultaneously. Simulation studies confirm the control effect and robustness of the proposed control.

Vachirasricirikul, Sitthidet; Ngamroo, Issarachai; Kaitwanidvilai, Somyot

56

Optimum Diversity Combining Circuit for a Plurality of Channels.  

National Technical Information Service (NTIS)

This invention consists of an AM/AGC weighted diversity combiner utilizing the AGC and AM voltages from the AGC loops of a plurality of receivers for generating an optimum weighting signal or combining ratio.

E. R. Hill E. L. Law

1980-01-01

57

Interactions of Cations with RNA Loop-Loop Complexes  

PubMed Central

RNA loop-loop interactions are essential in many biological processes, including initiation of RNA folding into complex tertiary shapes, promotion of dimerization, and viral replication. In this article, we examine interactions of metal ions with five RNA loop-loop complexes of unique biological significance using explicit-solvent molecular-dynamics simulations. These simulations revealed the presence of solvent-accessible tunnels through the major groove of loop-loop interactions that attract and retain cations. Ion dynamics inside these loop-loop complexes were distinctly different from the dynamics of the counterion cloud surrounding RNA and depend on the number of basepairs between loops, purine sequence symmetry, and presence of unpaired nucleotides. The cationic uptake by kissing loops depends on the number of basepairs between loops. It is interesting that loop-loop complexes with similar functionality showed similarities in cation dynamics despite differences in sequence and loop size.

Singh, Abhishek; Sethaphong, Latsavongsakda; Yingling, Yaroslava G.

2011-01-01

58

Nondissipative optimum charge regulator  

NASA Technical Reports Server (NTRS)

Optimum charge regulator provides constant level charge/discharge control of storage batteries. Basic power transfer and control is performed by solar panel coupled to battery through power switching circuit. Optimum controller senses battery current and modifies duty cycle of switching circuit to maximize current available to battery.

Rosen, R.; Vitebsky, J. N.

1970-01-01

59

The Kissing-Loop T-Shaped Structure Translational Enhancer of Pea Enation Mosaic Virus Can Bind Simultaneously to Ribosomes and a 5? Proximal Hairpin  

PubMed Central

The Pea Enation Mosaic Virus (PEMV) 3? translational enhancer, known as the kissing-loop T-shaped structure (kl-TSS), binds to 40S subunits, 60S subunits, and 80S ribosomes, whereas the Turnip crinkle virus (TCV) TSS binds only to 60S subunits and 80S ribosomes. Using electrophoretic mobility gel shift assay (EMSA)-based competition assays, the kl-TSS was found to occupy a different site in the ribosome than the P-site-binding TCV TSS, suggesting that these two TSS employ different mechanisms for enhancing translation. The kl-TSS also engages in a stable, long-distance RNA-RNA kissing-loop interaction with a 12-bp 5?-coding-region hairpin that does not alter the structure of the kl-TSS as revealed by molecular dynamics simulations. Addition of the kl-TSS in trans to a luciferase reporter construct containing either wild-type or mutant 5? and 3? PEMV sequences suppressed translation, suggesting that the kl-TSS is required in cis to function, and both ribosome-binding and RNA interaction activities of the kl-TSS contributed to translational inhibition. Addition of the kl-TSS was more detrimental for translation than an adjacent eIF4E-binding 3? translational enhancer known as the PTE, suggesting that the PTE may support the ribosome-binding function of the kl-TSS. Results of in-line RNA structure probing, ribosome filter binding, and high-throughput selective 2?-hydroxyl acylation analyzed by primer extension (hSHAPE) of rRNAs within bound ribosomes suggest that kl-TSS binding to ribosomes and binding to the 5? hairpin are compatible activities. These results suggest a model whereby posttermination ribosomes/ribosomal subunits bind to the kl-TSS and are delivered to the 5? end of the genome via the associated RNA-RNA interaction, which enhances the rate of translation reinitiation.

Gao, Feng; Gulay, Suna P.; Kasprzak, Wojciech; Dinman, Jonathan D.

2013-01-01

60

Electromagnetic inductive models for the loop-loop flaring interaction  

Microsoft Academic Search

The solar corona is a highly structured medium. Coronal loops, which trace closed magnetic field lines, are the primary structural elements. These loops are the evolving non-stationary objects growing up and changing their shape. Complex dynamics of the loops together with action of possible under-photospheric dynamo mechanisms cause the majority of coronal magnetic loops to be very likely as the

M. Khodachenko; H. Rucker

2003-01-01

61

Optimum propeller wind turbines  

SciTech Connect

The Prandtl-Betz-Theodorsen theory of heavily loaded airscrews has been adapted to the design of propeller windmills which are to be optimized for maximum power coefficient. It is shown that the simpler, light-loading, constant-area wake assumption can generate significantly different ''optimum'' performance and geometry, and that it is therefore not appropriate to the design of propeller wind turbines when operating in their normal range of high-tip-speed-to-wind-speed ratio. Design curves for optimum power coefficient are presented and an example of the design of a typical two-blade optimum rotor is given.

Sanderson, R.J.; Archer, R.D.

1983-11-01

62

Optimum Aircraft Rescue Tool.  

National Technical Information Service (NTIS)

This report details the design, development, testing, and evaluation pertaining to two versions of an Optimum Aircraft Rescue Tool. The rescue tool is a lightweight device required to replace several manually operated tools used by rescue personnel when f...

E. W. LeMaster P. R. Hughes J. R. Jenkins

1983-01-01

63

Shapes, shapes, shapes!  

NSDL National Science Digital Library

Shapes are awesome! Can you Assemble the Square? Play this game and find out! Slide, flip, and rotate the shapes in RoboPacker! Practice your geometry vocabulary and use the Flash Cards for Geometry!! ...

Johnson, Ms.

2008-04-30

64

Optimum x-ray spectra for mammography.  

PubMed

A number of authors have calculated x-ray energies for mammography using, as a criterion, the maximum signal-to-noise ratio (SNR) obtainable per unit dose to the breast or conversely the minimum exposure for constant SNR. The predicted optimum energy increases with increasing breast thickness. Tungsten anode x-ray spectra have been measured with and without various added filter materials to determine how close the resultant spectra can be brought to the predicted optimum energies without reducing the x-ray output to unacceptable levels. The proportion of the total number of x-rays in a measured spectrum lying within a narrow energy band centred on the predicted optimum has been used as an optimum energy index. The effect of various filter materials on the measured x-ray spectra has been investigated both experimentally and theoretically. The resulting spectra have been compared with molybdenum anode, molybdenum filtered x-ray spectra normally used for mammography. It is shown that filters with K-absorption edges close to the predicted optimum energies are the most effective at producing the desired spectral shape. The choices of filter thickness and Vp are also explored in relationship to their effect on the resultant x-ray spectral shape and intensity. PMID:7146094

Beaman, S A; Lillicrap, S C

1982-10-01

65

Improved two-loop beam energy stabilizer for an FN tandem accelerator  

SciTech Connect

A detailed analysis of the properties of various elements in a two-loop voltage regulator for a tandem accelerator enabled design of an optimum system which reduces effective accelerating voltage noise below 100 V. Essential features of the new system are high-quality slit preamplifiers, careful attention to removal of extraneous noise sources, and proper shaping of frequency responses to maximize stable gains and ensure compatibility of the two control loops. The resultant beam energy stabilizer system is easy to operate, has well defined indicators for proper adjustment of operating parameters, and recovers reliably from beam interruptions.

Trainor, T.A.

1981-01-01

66

Using Signal Detection Theory and Time Window-based Human-In-The-Loop simulation as a tool for assessing the effectiveness of different qualitative shapes in continuous monitoring tasks.  

PubMed

This paper provides a case study of Signal Detection Theory (SDT) as applied to a continuous monitoring dual-task environment. Specifically, SDT was used to evaluate the independent contributions of sensitivity and bias to different qualitative gauges used in process control. To assess detection performance in monitoring the gauges, we developed a Time Window-based Human-In-The-Loop (TWHITL) simulation bed. Through this test bed, we were able to generate a display similar to those monitored by console operators in oil and gas refinery plants. By using SDT and TWHITL, we evaluated the sensitivity, operator bias, and response time of flow, level, pressure, and temperature gauge shapes developed by Abnormal Situation Management(®) (ASM(®)) Consortium (www.asmconsortium.org). Our findings suggest that display density influences the effectiveness of participants in detecting abnormal shapes. Furthermore, results suggest that some shapes elicit better detection performance than others. PMID:24079651

Kim, Jung Hyup; Rothrock, Ling; Laberge, Jason

2014-05-01

67

RECONSTRUCTING THE LOCAL TWIST OF CORONAL MAGNETIC FIELDS AND THE THREE-DIMENSIONAL SHAPE OF THE FIELD LINES FROM CORONAL LOOPS IN EXTREME-ULTRAVIOLET AND X-RAY IMAGES  

SciTech Connect

Nonlinear force-free fields are the most general case of force-free fields, but the hardest to model as well. There are numerous methods of computing such fields by extrapolating vector magnetograms from the photosphere, but very few attempts have so far made quantitative use of coronal morphology. We present a method to make such quantitative use of X-ray and EUV images of coronal loops. Each individual loop is fit to a field line of a linear force-free field, allowing the estimation of the field line's twist, three-dimensional geometry, and the field strength along it. We assess the validity of such a reconstruction since the actual corona is probably not a linear force-free field, and that the superposition of linear force-free fields is generally not itself a force-free field. To do so, we perform a series of tests on nonlinear force-free fields, described in Low and Lou. For model loops we project field lines onto the photosphere. We compare several results of the method with the original field, in particular the three-dimensional loop shapes, local twist (coronal alpha), distribution of twist in the model photosphere, and strength of the magnetic field. We find that (1) for these trial fields, the method reconstructs twist with a mean absolute deviation of at most 15% of the range of photospheric twist, (2) heights of the loops are reconstructed with a mean absolute deviation of at most 5% of the range of trial heights, and (3) the magnitude of non-potential contribution to a photospheric field is reconstructed with a mean absolute deviation of at most 10% of the maximal value.

Malanushenko, A.; Longcope, D. W.; McKenzie, D. E. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

2009-12-20

68

Loop simulations.  

PubMed

Loop modeling is crucial for high-quality homology model construction outside conserved secondary structure elements. Dozens of loop modeling protocols involving a range of database and ab initio search algorithms and a variety of scoring functions have been proposed. Knowledge-based loop modeling methods are very fast and some can successfully and reliably predict loops up to about eight residues long. Several recent ab initio loop simulation methods can be used to construct accurate models of loops up to 12-13 residues long, albeit at a substantial computational cost. Major current challenges are the simulations of loops longer than 12-13 residues, the modeling of multiple interacting flexible loops, and the sensitivity of the loop predictions to the accuracy of the loop environment. PMID:22323223

Totrov, Maxim

2012-01-01

69

Optimum laser beam profile for maximum energy extraction from a saturable amplifier  

Microsoft Academic Search

The optimum laser beam profile allowing maximum energy extraction from a low-gain saturable amplifier is determined analytically. It is found that, in general, this intensity distribution does not correspond to the gain profile. Several examples demonstrate, however, that the optimum is broad in the space of functions so that a large class of beam shapes can be nearly optimum.

Claude Paré

1996-01-01

70

Optimum performance and potential flow field of hovering rotors  

NASA Technical Reports Server (NTRS)

Rotor and propeller performance and induced potential flowfields were studied on the basis of a rotating actuator disk concept, with special emphasis on rotors hovering out of ground effect. A new theory for the optimum performance of rotors hovering OGE is developed and presented. An extended theory for the optimum performance of rotors and propellers in axial motion is also presented. Numerical results are presented for the optimum distributions of blade-bound circulation together with axial inflow and ultimate wake velocities for the hovering rotor over the range of thrust coefficient of interest in rotorcraft applications. Shapes of the stream tubes and of the velocities in the slipstream are obtained, using available methods, for optimum and off-optimum circulation distributions for rotors hovering in and out of ground effect. A number of explicit formulae useful in computing rotor and propeller induced flows are presented for stream functions and velocities due to distributions of circular vortices over axi-symmetric surfaces.

Wu, J. C.; Sigman, R. K.

1975-01-01

71

Optimum Designs in Regression Problems  

Microsoft Academic Search

Although regression problems have been considered by workers in all sciences for many years, until recently relatively little attention has been paid to the optimum design of experiments in such problems. At what values of the independent variable should one take observations, and in what proportions? The purpose of this paper is to develop useful computational procedures for finding optimum

J. Kiefer; J. Wolfowitz

1959-01-01

72

Optimum orientation of absorber plates  

SciTech Connect

Long-term analyses are presented to predict the optimum tilt angle of an absorber plate at any surface azimuth angle {gamma}. The analyses include the effects of number of glass covers, latitude angle, monthly average clearness index, month, and ground reflectivity. The effects of each of these parameters on the optimum tilt of a south-facing surface are studied. Two numerical correlations, for ground reflectivity equal 0.2 and 0.7, are developed to predict the monthly optimum tilt of a surface. The two correlations are used to predict the optimum tilt of a surface over any specified period of time that extends from one month up to several months or a year. The analyses are also extended to predict the optimum tilt angle and azimuth angles of surfaces exposed to shading by surrounding objects. Illustrative examples are presented to demonstrate the application of the analyses.

Elsayed, M.M. (King Abdulaziz Univ., Jeddah (Saudi Arabia))

1989-01-01

73

Optimum strong-motion array geometry for source inversion - II  

USGS Publications Warehouse

Optimum strong-motion array geometry for source inversions is determined for each of three types of earthquake faults: strike-slip, dip-slip and offshore subduction thrust. It is found that the complete Green's function is capable of stabilizing the accuracy of an inversion solution obtained using theoretical seismograms, regardless of the differences in array configuration. The optimum strong-motion array for a strike-slip fault is characterized by stations well distributed in azimuth, while the optimum array for a dip-slip event has stations arranged in a grid-shaped form. -from Author

Iida, M.

1990-01-01

74

''Optimum productivity'': a geneticist's view  

SciTech Connect

Both ''optimum'' and ''productivity'' are explored in a social context with a long time dimension. Renewability, flexibility, and diversity are important concepts in long-term planning to achieve optimum productivity. Various possible genetic contributions, including complementary clones, quantitative genetic engineering, resistant trees and plantations, elimination of inbreeding, single-gene genetic engineering, and agri-forestry, are suggested for long-term sustained or increased productivity.

Libby, W.J.

1980-01-01

75

Optimum size of nanorods for heating application  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles (MNP?s) have become increasingly important in heating applications such as hyperthermia treatment of cancer due to their ability to release heat when a remote external alternating magnetic field is applied. It has been shown that the heating capability of such particles varies significantly with the size of particles used. In this paper, we theoretically evaluate the heating capability of rod-shaped MNP?s and identify conditions under which these particles display highest efficiency. For optimally sized monodisperse particles, the power generated by rod-shaped particles is found to be equal to that generated by spherical particles. However, for particles which are not mono dispersed, rod-shaped particles are found to be more effective in heating as a result of the greater spread in the power density distribution curve. Additionally, for rod-shaped particles, a dispersion in the radius of the particle contributes more to the reduction in loss power when compared to a dispersion in the length. We further identify the optimum size, i.e the radius and length of nanorods, given a bi-variate log-normal distribution of particle size in two dimensions.

Seshadri, G.; Thaokar, Rochish; Mehra, Anurag

2014-08-01

76

Performance characteristics of aerodynamically optimum turbines for wind energy generators  

NASA Technical Reports Server (NTRS)

This paper presents a brief discussion of the aerodynamic methodology for wind energy generator turbines, an approach to the design of aerodynamically optimum wind turbines covering a broad range of design parameters, some insight on the effect on performance of nonoptimum blade shapes which may represent lower fabrication costs, the annual wind turbine energy for a family of optimum wind turbines, and areas of needed research. On the basis of the investigation, it is concluded that optimum wind turbines show high performance over a wide range of design velocity ratios; that structural requirements impose constraints on blade geometry; that variable pitch wind turbines provide excellent power regulation and that annual energy output is insensitive to design rpm and solidity of optimum wind turbines.

Rohrbach, C.; Worobel, R.

1975-01-01

77

Optimum Spacing Of Extraction Wells  

NASA Astrophysics Data System (ADS)

An approach to selecting the optimum spacing of extraction wells for both groundwater production and groundwater cleanup is presented. Optimum well spacing is dependent upon 1) whether the system consits of an odd or even number of wells, 2) total number of wells, 3) aquifer thickness (B), 4) regional groundwater velocity (U), and 5) pumping rate of an extraction well (Q). Although an exact optimum well spacing cannot be determined for a system that consists of 30 or more wells (due to a lack of convergence for finding the roots of the stagnation-point equation), the optimum well-spacing factor of 0.4765 x Q/BU ensures minimum loss of groundwater recovery between the wells for a system that consists of 30 to 200 wells. Optimum well spacing and the points on the capture-zone curves are presented. Regression equations were developed for estimating capture-zone curves. Specific capture-zone curves can be constructed for any number of wells with knowledge of the parameters, Q/BU. This approach provides a method to design a new group of extraction wells and modify existing but deficient and under-designed systems, where more extraction wells are required. Using this scheme for such a modification, it is recommended that the number of wells be increased in pairs. The resulting arrangement ensures minimum loss of groundwater recovery between the wells.

Ahmad, W.

1995-03-01

78

Optimum dimensions of extended surfaces operating in a convective environment  

SciTech Connect

This article is devoted to the review of the literature on optimum dimensions of extended surfaces losing heat by pure convection to the surroundings. The review covers straight (longitudinal) fins, annular (radial) fins, and spines of different profile shapes. The optimum dimensions for each shape are given both in terms of the volume of the material as well as the heat dissipation. The effects of tip heat loss, variable heat transfer coefficient, internal heat generation, temperature dependent thermal conductivity, base convection, and primary surface thickness on the optimum dimensions are discussed. The optimization procedure is illustrated with several numerical examples. Areas of extended surface technology where further optimization studies are needed are identified. It is hoped that the article would serve the dual purpose of the state-of-the-art as well as a pedagogical review. 24 refs., 22 figs., 9 tabs.

Aziz, A. [Gonzaga Univ., Spokane, WA (United States)

1992-05-01

79

Optimum windmill-site matching  

Microsoft Academic Search

A methodology for the selection of the optimum windmill for a specific site is developed. The selection is based on finding the capacity factors of the available windmills. This is done by using long-term wind speed data recorded at different hours of the day for many years. These data are then used to generate mean wind speeds for a typical

Ziyad M. Salameh; I. Safari

1992-01-01

80

Different Conceptualizations of Optimum Development  

Microsoft Academic Search

This article discusses different conceptualizations of optimum development in adulthood. The existential perspective of Rollo May is compared to the self-actualization theory of Abraham Maslow and to transpersonal psychology. The paradigms and value assumptions underlying the different theories of personality are explicated, and social constructionism is used as an organizing frame of reference. The principal argument is that in addition

Angela Pfaffenberger

2007-01-01

81

OPTIMUM FREQUENCY OF CALIBRATION MONITORING  

EPA Science Inventory

The paper develops an algorithm by which to compute the optimal frequency of calibration monitoring to minimize the total cost of analyzing a set of samples and the required calibration standards. Optimum calibration monitoring is needed because of the high cost and calibration d...

82

Optimum optical limited scan antenna  

Microsoft Academic Search

An optical limited scan antenna system is considered for applications such as spot coverage of a small portion of the earth from a satellite. The optimum criterion relating aperture efficiency, number of control elements, and angular coverage is revisited briefly. The optical scheme advocated utilizes a bootlace aperture lens, a generalized Luneberg lens focused to the near field, and a

E. C. Dufort

1986-01-01

83

Optimum windmill-site matching  

SciTech Connect

In this paper a methodology for the selection of the optimum windmill for a specific site is developed. The selection windmill for a specific site is developed. The selection is based on finding the capacity factors (CF) of the available windmills. This is done by using long term wind speed data recorded at different hours of the day for many years. This data is then used to generate mean wind speeds for a typical day in a month. Probability density functions for the mean wind speeds for the different hours of the day are generated with the manufacturer's specifications on windmills used to calculate the capacity factors for the windmills. The windmill with the highest average capacity factor for the specific site is the optimum one and to be recommended.

Salameh, Z.M.; Safari, I. (Dept. of Electrical Engineering, Univ. of Massachusetts, Lowell, Lowell, MA (United States))

1992-12-01

84

Shape and Reinforcement Optimization of Underground Tunnels  

Microsoft Academic Search

Design of support system and selecting an optimum shape for the opening are two important steps in designing excavations in rock masses. Currently selecting the shape and support design are mainly based on designer's judgment and experience. Both of these problems can be viewed as material distribution problems where one needs to find the optimum distribution of a material in

Kazem Ghabraie; Yi Min Xie; Xiaodong Huang; Gang Ren

2010-01-01

85

Frequency Agile Wideband Phase Lock Loops for RF-FPGAs.  

National Technical Information Service (NTIS)

This project develops phase locked loop (PLL) macros that use novel digital architectures to achieve a user configurable optimum balance between phase noise, frequency resolution, frequency switching time, and power consumption. The PLL macros are impleme...

B. Sullam J. Crawford J. Popp M. Mar X. Yao

2013-01-01

86

Loop space  

NASA Astrophysics Data System (ADS)

Several topics in the loop-space formulation of non-Abelian gauge theories are considered. The basic objects dealt with are the unrenormalized dimensionally regularized gauge-invariant loop functions W(Cig, ?), where Ci is a set of loops, g is the unrenormalized coupling constant, and ? is the deviation from four space-time dimensions. The renormalization-group equations satisfied by the corresponding renormalized loop functions are derived and, using asymptotic freedom, used to determine the exact behavior of the functions when the length L of the loops approaches zero. The result is (-lnL?)a(?), where ? is the subtraction mass and ? represents the cusp and cross-point angles of the loops. The function a(?) is exactly computable and several examples are given. The equivalent result may be stated as the exact behavior of the renormalization-constant matrix Zij(?, gR, ?) for ?-->0 with fixed renormalized coupling constant gR, or as the exact behavior of the unrenormalized loop function for ?-->0 and gR fixed. It is shown next that the W(Cig, ?) satisfy dimensionally regularized Makeenko-Migdal equations in all orders of perturbation theory. The proof makes detailed use of dimensional regularization, Becchi-Rouet-Stora symmetry, gauge-field combinatorics, and properties of the area functional derivative of path-ordered multiple line integrals. Doubt is cast on the existence of such useful equations when other regularizations are used or when renormalization is performed. The Mandelstam constraints are considered next. Among other things, it is shown that the loop-function renormalization may be performed such that the renormalized functions satisfy a constraint which has the same form as the unrenormalized constraint i=1(N+1)?aiW(Ci)=0, for the U(N) gauge group. The paper concludes with illustrations of how observable matrix elements of physical (color singlet, quark bilinear) flavor currents may be expressed in terms of loop functions. Among other topics discussed in the paper are the N-->? limit, two-dimensional QCD, and normalization conditions on the renormalized loop functions.

Brandt, R. A.; Gocksch, A.; Sato, M.-A.; Neri, F.

1982-12-01

87

Dynamic Aperture-based Solar Loop Segmentation  

NASA Technical Reports Server (NTRS)

A new method to automatically segment arc-like loop structures from intensity images of the Sun's corona is introduced. The method constructively segments credible loop structures by exploiting the Gaussian-like shape of loop cross-sectional intensity profiles. The experimental results show that the method reasonably segments most of the well-defined loops in coronal images. The method is only the second published automated solar loop segmentation method. Its advantage over the other published method is that it operates independently of supplemental time specific data.

Lee, Jon Kwan; Newman, Timothy S.; Gary, G. Allen

2006-01-01

88

Optimum Beamforming Subject to Multiple Linear Constraints.  

National Technical Information Service (NTIS)

Optimum beamformers with a single look direction constraint can suffer from signal suppression problems when the optimum weights are calculated from the inverse of the signal-plus-noise cross-spectral matrix. Signal suppression occurs when the beam steer ...

A. K. Steele

1980-01-01

89

Optimum bandwidth-distance performance in full response CPM systems  

Microsoft Academic Search

The problem of minimizing the effective bandwidth of a binary full-response continuous-phase-modulation (CPM) signal with respect to the shape of the frequency pulse for a prescribed value of the minimum Euclidean distance, which is directly related to the error probability for high signal-to noise ratio, is considered. An analytical procedure is presented that allows the determination of the optimum pulse

Matteo Campanella; U. Lo Faso; Giovanni Mamola

1988-01-01

90

Swarms: Optimum aggregations of spacecraft  

NASA Technical Reports Server (NTRS)

Swarms are aggregations of spacecraft or elements of a space system which are cooperative in function, but physically isolated or only loosely connected. For some missions the swarm configuration may be optimum compared to a group of completely independent spacecraft or a complex rigidly integrated spacecraft or space platform. General features of swarms are induced by considering an ensemble of 26 swarms, examples ranging from Earth centered swarms for commercial application to swarms for exploring minor planets. A concept for a low altitude swarm as a substitute for a space platform is proposed and a preliminary design studied. The salient design feature is the web of tethers holding the 30 km swarm in a rigid two dimensional array in the orbital plane. A mathematical discussion and tutorial in tether technology and in some aspects of the distribution of services (mass, energy, and information to swarm elements) are included.

Mayer, H. L.

1980-01-01

91

Backfire antennas constructed with coaxial circular loops  

Microsoft Academic Search

The radiation characteristics of backfire antennas constructed entirely of circular loops are studied. A comparison between this type of backfire antenna and the conventional one, made of a solid reflector, reveals that the optimum dimensions of the reflector and the peripheral rim are approximately the same for both kinds of antennas. In addition, it is found that as few as

A. Shoamanesh; L. Shafai

1980-01-01

92

Loop Algorithm  

NASA Astrophysics Data System (ADS)

The loop algorithm for the world-line quantum Monte Carlo method on quantum lattice models is presented. After introducing the path integral representation that maps a quantum model to a classical one, we describe the continuous imaginary time limit, cluster algorithm, and the rejection free scheme, which are the major improvements on the quantum Monte Carlo technique during the last decades. By means of the loop algorithm, one can simulate various unfrustrated quantum lattice models of millions of sites at extremely low temperatures with absolute accuracy, being free from the critical and fine-mesh slowing down and the Suzuki-Trotter discretization error. We also discuss some technical aspects of the algorithm such as effective implementation and parallelization.

Todo, Synge

93

Shape Savvy  

NSDL National Science Digital Library

Help your students identify these different shapes! Learn your shapes with Big Bird s Shapes and then Make Designs with Shapes to create objects! You better know your colors to Paint the Shapes correctly! ...

Popwell, Ms.

2010-09-22

94

NICMOS Optimum Coronagraphic Focus Determination  

NASA Astrophysics Data System (ADS)

As originally designed the NICMOS coronagraph had two fixed focii in the optical path: {a} at the coronagraphic hole {image plane obscuration} in the camera 2 field divider mirror {at the f/24 focus of the input OTA beam} and, {b} at the detector {reimaged focal plane of the f/45 camera 2 relay optics}. Because of the forward displacement of the cold optical bench holding the Camera 2 detector resulting from the larger-than-expected expansion of the solid N2 cryogen early in HST Cycle 7 {as described and documented by the 'Dewar Anomaly Review Board'}, the two focii are now aconjugate. For direct {non-coronagraphic} imaging, this is of little concern and "best focus" at the detector is readily achieved by adjustment of NICMOS's Pupil Alignment Mechanism mirror. This, however, results in a "soft" focus at the upstream f/24 image plane of the coronagraphic hole and a degradation in coronagraphic contrast. Further deformation and hysteretic displacement of the NICMOS dewar and associated differential stresses on its mounting straps are likely to result from power cycling the NCS during SM4. As a result, the intended locations of the camera 2 focal planes in the cold well at the detector, and in the warm optics outside of the dewar, are likely to change. Such a change was seen following the warmup and cooldown of the NICMOS dewar following cryogen depletion in January 2000 and the installation of the NCS in 2002. If uncompensated, through informed investigation, coronagraphy will be adversely affected since the scattered and diffracted background light from a target afocally imaged in the coronagraphic hole will increase and thus reduce the achievable contrast at the detector image plane. The coronagraphic stray light rejection is most efficient by minimizing the spot size of an input PSF in the coronagraphic hole, but is traded against image defocus at the detector. The purpose of this test is to find the optimum wavelength-dependent compromise in the PAM position to maximize the coronagraphic image:background contrast ratio at the detector. Further details and background information may be found in the SMOV/7157 test report "NICMOS Optimal Coronagraphic Focus Determination" available from the NICMOS IDT. This proposal corresponds to SMOV activity NIC-11.;

Schneider, Glenn

2008-07-01

95

NICMOS Optimum Coronagraphic Focus Determinaton  

NASA Astrophysics Data System (ADS)

As originally designed the NICMOS coronagraph had two focii at conjugate points in the optical path with the coronagraphic hole at the f/24 focus of the input OTA beam, and the detector at the reimaged f/45 focus in Camera 2. Because of the forward displacement of the cold optical bench holding the Camera 2 detector, as a result of the larger-than-expected expansion of the solid N2 cryogen {as described and documented by the 'Dewar Anomoly Review Board'}, the two focii are now aconjugate. For direct imaging this is of little concern, and the HST/NICMOS Camera 2 focus interface is established by co-locating the f/45 image plane on the detector. This is done by de-spacing the relayed focus through a translative motion {with compensating comal tilt correction} of the Pupil Alignment Mechanism {PAM}. The mirror which this mechanism drives is upstream of the field divider mirror upon which the coronagraphic hole resides. Therefore, achieving a "best" focus at the detector results in a "soft" focus {in the f/24 image plane} at the coronagraphic hole. This leads to a wavelength-dependent increase in the diffracted energy in the now-defocused unocculted wings of a PSF from a target placed inside of the coronagraphic hole {as the f/24 image plane will fall behind the surface of the camera 2 field divider mirror} increasing the scattered and diffracted background around the target and lowering the field contrast at the detector image plane. In principal the coronagraphic stray light rejection would be most efficient by minimizing the spot size of an input PSF in the hole. This, however, is traded against a small degree of defocus at the detector. Ultimately, the best coronagraphic performance is achieved where the image contrast between an unocculted target and the residual background from an occulted source {both affected differently by focus and subsequent scattering} is maximized. The purpose of this test is to find the optimum PAM position to maximize the coronagraphic image:background contrast ratio. Further details and background information may be found in the SMOV/7157 test report "NICMOS Optimal Coronagraphic Focus Determination" available from the NICMOS IDT.

Schneider, Glenn

2001-07-01

96

New theory for giant loops.  

NASA Technical Reports Server (NTRS)

Four very large, shell-shaped features are known from the surveys of radio emission from the Galaxy. It is suggested that the giant loops represent a class of nebulae, induced by supernova radiation as opposed to supernova ejecta. The model considered provides a qualitative explanation for the spectral and polarization properties of the radio emission from giant loops. The radio emitting electrons are part of the general cosmic ray gas and need not arise specifically in the supernova that produced the fossil Stroemgren sphere.

Brandt, J. C.; Maran, S. P.

1972-01-01

97

Many ways to loop DNA.  

PubMed

In the 1960s, I developed methods for directly visualizing DNA and DNA-protein complexes using an electron microscope. This made it possible to examine the shape of DNA and to visualize proteins as they fold and loop DNA. Early applications included the first visualization of true nucleosomes and linkers and the demonstration that repeating tracts of adenines can cause a curvature in DNA. The binding of DNA repair proteins, including p53 and BRCA2, has been visualized at three- and four-way junctions in DNA. The trombone model of DNA replication was directly verified, and the looping of DNA at telomeres was discovered. PMID:24005675

Griffith, Jack D

2013-10-11

98

Optimum Reset of Ship's Inertial Navigation System  

Microsoft Academic Search

Optimum linear filter and control theory is applied to the practical problem of supplementing an inertial navigation system with discrete reference information. The information takes the form of position obtained from Loran C or Decca, for example, and occasional azimuth fixes obtained from star sightings. In particular, optimum use of this information is discussed for the Ship's Inertial Navigation System

B. E. Bona; Robert J. Smay

1966-01-01

99

Noether's theorem for optimum control systems  

Microsoft Academic Search

In this paper Noether's theorem of classical mechanics and the variational calculus is developed for optimum control systems. Also, it is shown that the existence of first integrals of Pontryagin's maximum principle equations depend on the existence of solutions of a system of partial differential equations—generalized Killing's equations —for optimum control systems.

DJORDJE S. DJUKI?

1973-01-01

100

Optimum gold films for mercury detection  

Microsoft Academic Search

An electron-beam heated source was used for the deposition of gold films on glass. The d.c. resistance change upon surface adsorption of elemental mercury has been measured for varying film thicknesses and annealing temperatures. An optimum film thickness in the region of 100 AA has been determined, with an optimum annealing temperature of 175 degrees C. It is postulated that

H. K. Chaurasia; A. Huizinga; W. A. G. Voss

1975-01-01

101

Optimum insulation thickness for refrigeration applications  

Microsoft Academic Search

A thermoeconomic optimization analysis is presented yielding a simple algebraic formula for estimating optimum insulation thickness for refrigeration applications. The effects of design parameters on the optimum insulation thickness are investigated for three test cities using an interactive computer code written in Fortran 77. The equivalent full load hours method is used to estimate the energy requirements.

M. S Söylemez; M Ünsal

1999-01-01

102

Conditions for optimum giant magnetoresistance in granular metals  

SciTech Connect

The dependence of the giant magnetoresistance (GMR) of a metallic granular system on the concentration of magnetic particles is studied numerically. The effect of particle coalescence and dipolar interactions between the particles on the value of optimum GMR and the shape of the concentration dependence curve are discussed. The micromagnetic configuration of the system is obtained by a Monte Carlo algorithm that involves short-range effective exchange couplings and long range dipolar interactions. The conductivity is obtained using Kubo{close_quote}s formula for a tight binding Hamiltonian. A comparison of our results to experiments on metallic granular films is made. {copyright} 2001 American Institute of Physics.

Kechrakos, D.; Trohidou, K. N.

2001-06-01

103

Observations of loops and prominences  

NASA Technical Reports Server (NTRS)

We review recent observations by the Yohkoh-SXT (Soft X-ray Telescope) in collaboration with other spacecraft and ground-based observatories of coronal loops and prominences. These new results point to problems that SoHO will be able to address. With a unique combination of rapid-cadence digital imaging (greater than or equal to 32 s full-disk and greater than or equal to 2 s partial-frame images), high spatial resolution (greater than or equal to 2.5 arcsec pixels), high sensitivity (EM less than or equal to 10(exp 42) cm(exp -3)), a low-scatter mirror, and large dynamic range, SXT can observe a vast range of targets on the Sun. Over the first 21 months of Yohkoh operations SXT has taken over one million images of the corona and so is building up an invaluable long-term database on the large-scale corona and loop geometry. The most striking thing about the SXT images is the range of loop sizes and shapes. The active regions are a bright tangle of magnetic field lines, surrounded by a network of large-scale quiet-Sun loops stretching over distances in excess of 105 km. The cross-section of most loops seems to be constant. Loops displaying significant Gamma's are the exception, not the rule, implying the presence of widespread currents in the corona. All magnetic structures show changes. Time scales range from seconds to months. The question of how these structures are formed, become filled with hot plasma, and are maintained is still open. While we see the propagation of brightenings along the length of active-region loops and in X-ray jets with velocities of several hundred km/s, much higher velocities are seen in the quiet Sun. In XBP flares, for example, velocities of over 1000 km/s are common. Active-region loops seem to be in constant motion, moving slowly outward, carrying plasma with them. During flares, loops often produce localized brightenings at the base and later at the apex of the loop. Quiescent filaments and prominences have been observed regularly. Their coronal manifestation seems to be an extended arcade of loops overlying the filament. Reliable alignment of the ground-based data with the X-ray images make it possible to make a detailed intercomparison of the hot and cold plasma structures over extended periods. Hence we are able to follow the long-term evolution of these structures and see how they become destabilized and erupt.

Strong, Keith T.

1994-01-01

104

Water Stream "Loop-the-Loop"  

ERIC Educational Resources Information Center

Discusses the design of a modified loop-the-loop apparatus in which a water stream is used to illustrate centripetal forces and phenomena of high-velocity hydrodynamics. Included are some procedures of carrying out lecture demonstrations. (CC)

Jefimenko, Oleg

1974-01-01

105

Optimum structure of Whipple shield against hypervelocity impact  

NASA Astrophysics Data System (ADS)

Hypervelocity impact of a spherical aluminum projectile onto two spaced aluminum plates (Whipple shield) was simulated to estimate an optimum structure. The Smooth Particle Hydrodynamics (SPH) code which has a unique migration scheme from a rectangular coordinate to an axisymmetic coordinate was used. The ratio of the front plate thickness to sphere diameter varied from 0.06 to 0.48. The impact velocities considered here were 6.7 km/s. This is the procedure we explored. To guarantee the early stage simulation, the shapes of debris clouds were first compared with the previous experimental pictures, indicating a good agreement. Next, the debris cloud expansion angle was predicted and it shows a maximum value of 23 degree for thickness ratio of front bumper to sphere diameter of 0.23. A critical sphere diameter causing failure of rear wall was also examined while keeping the total thickness of two plates constant. There exists an optimum thickness ratio of front bumper to rear wall, which is identified as a function of the size combination of the impacting body, front and rear plates. The debris cloud expansion-correlated-optimum thickness ratio study provides a good insight on the hypervelocity impact onto spaced target system.

Lee, M.

2014-05-01

106

Optimum design of a scavenging antenna system  

Microsoft Academic Search

This paper presents some guidelines for the design procedure of an optimum scavenging antenna system. Based on these guidelines, a scavenging antenna has been fabricated and characterized, achieving very good results in comparison to the traditional designs.

Raquel Serrano; Albert Aguasca; Jordi Romeu; Lluis Jofre

2010-01-01

107

Computational Complexity of Optimum Multiuser Detection.  

National Technical Information Service (NTIS)

Optimum centralized demodulation of the independent data streams transmitted simultaneously by several users through a Code Division Multiple-Access channel is considered. Each user sends an arbitrary assigned signal waveform, which is linearly modulated ...

S. Verdu'

1989-01-01

108

Optimum Design of Grillages Including Warping.  

National Technical Information Service (NTIS)

A method is presented for optimum design of elastic grillages made of straight thin walled beams. The design problem is formulated by matrix displacement method. Empirical relationships are used to relate the beam cross-sectional properties to each other ...

M. P. Saka

1981-01-01

109

Coronal Loop Model Including Ion Kinetics  

NASA Astrophysics Data System (ADS)

We present a kinetic coronal loop model including collisions and wave-particle interactions to study the mechanisms of loop heating. The model is based on a quasi-linear treatment of the Vlasov equation for the reduced velocity distribution functions of the protons, which are the only ions considered in the loop plasma. For the energy input into the loop, we assume that linear Alfvén waves penetrate the loop from its footpoints and heat the protons via wave-particle interactions and wave absorption. Through Coulomb collisions between protons and electrons some thermal energy can be transferred to the electrons. It turns out that in such a model protons are hotter than electrons, and the scale length for proton heating along the loop is determined by the dissipation scale of the ion-cyclotron waves. Through the gyrofrequency this scale is connected to the cross section area of the loop and, thus, to the spatial variation of the magnetic field shaping the coronal loop. Furthermore, it is shown that in the case of a nearly homogeneous flux tube cross section, an almost flat temperature profile occurs along the major part of the loop with an enhanced plasma density. These plasma parameter profiles are consistent with those of loops having temperatures between 1 and 1.5 MK as observed in extreme-ultraviolet emission. However, if the magnetic field lines are more strongly diverging from the footpoints to the loop apex, the proton heating is found to be more uniform, resulting in a higher temperature and lower density along the loop. These profiles are similar to those observed in X-ray loops.

Bourouaine, Sofiane; Vocks, Christian; Marsch, Eckart

2008-04-01

110

Optimum Design of High-Speed Prop-Rotors  

NASA Technical Reports Server (NTRS)

An integrated multidisciplinary optimization procedure is developed for application to rotary wing aircraft design. The necessary disciplines such as dynamics, aerodynamics, aeroelasticity, and structures are coupled within a closed-loop optimization process. The procedure developed is applied to address two different problems. The first problem considers the optimization of a helicopter rotor blade and the second problem addresses the optimum design of a high-speed tilting proprotor. In the helicopter blade problem, the objective is to reduce the critical vibratory shear forces and moments at the blade root, without degrading rotor aerodynamic performance and aeroelastic stability. In the case of the high-speed proprotor, the goal is to maximize the propulsive efficiency in high-speed cruise without deteriorating the aeroelastic stability in cruise and the aerodynamic performance in hover. The problems studied involve multiple design objectives; therefore, the optimization problems are formulated using multiobjective design procedures. A comprehensive helicopter analysis code is used for the rotary wing aerodynamic, dynamic and aeroelastic stability analyses and an algorithm developed specifically for these purposes is used for the structural analysis. A nonlinear programming technique coupled with an approximate analysis procedure is used to perform the optimization. The optimum blade designs obtained in each case are compared to corresponding reference designs.

Chattopadhyay, Aditi; McCarthy, Thomas Robert

1993-01-01

111

Shape Explorer  

NSDL National Science Digital Library

Learn the relationship between perimeter and area. A random shape will be automatically generated. Calculate the area and perimeter of this shape. Shape Explorer is one of the Interactivate assessment explorers.

112

Shape Cutter  

NSDL National Science Digital Library

"With this tool, you can explore how to decompose shapes and recompose them to make other shapes. You can draw and cut shapes and also use slides, turns, and flips to move pieces around" from NCTM Illuminations.

Mathematics, Illuminations N.

2010-03-04

113

Shape Hunt  

NSDL National Science Digital Library

Students will go on a shape hunt in the classroom or designated area. During the shape hunt, students will draw pictures of the shapes they find and the object that it is found by, in order to show the position of the shape. After the shape hunt, students will use Timed-Pair-Share to explain to peers what shapes they found and their relative positions.

Hauptli, Meghan

2012-06-11

114

Optimum Electron Distributions for Space Charge Dominated Beams in Photoinjectors  

SciTech Connect

The optimum photo-electron distribution from the cathode of an RF photoinjector producing a space charge dominated beam is a uniform distribution contained in an ellipsoid. For such a bunch distribution, the space charge forces are linear and the emittance growth induced by those forces is totally reversible and consequently can be compensated. With the appropriate tuning of the emittance compensation optics, the emittance, at the end of photoinjector beamline, for an ellipsoidal laser pulse, would only have two contributions, the cathode emittance and the RF emittance. For the peak currents of 50A and 100 A required from the SBand and L-Band RF gun photoinjectors discussed here, the RF emittance contribution is negligible. If such an ellipsoidal photo-electron distribution were available, the emittance at the end of the beamline could be reduced to the cathode emittance. Its value would be reduced by more than 40% from that obtained using cylindrical shape laser pulses. This potentially dramatic improvement warrants review of the challenges associated with the production of ellipsoidal photo-electrons. We assume the photo-electrons emission time to be short enough that the ellipsoidal electron pulse shape will come directly from the laser pulse. We shift the challenge to ellipsoidal laser pulse shaping. To expose limiting technical issues, we consider the generation of ellipsoidal laser pulse shape in terms of three different concepts.

Limborg-Deprey, C.; Bolton, P.R.; /SLAC

2006-06-15

115

Flow in conjugate natural circulation loops  

NASA Astrophysics Data System (ADS)

Two natural circulation loops are considered thermally coupled through a heat exchanger common to both. Over the rest of the loops, the heat inflow per unit length is assumed known. A steady-state analysis is made in order to determine the fluid velocities and temperature distributions. Certain general results can be obtained for loops of arbitrary shapes. The special case of square geometries is also considered. The possibility of four different steady-state conditions is demonstrated and the variation of these solutions with respect to the system parameters is discussed.

Salazar, Octavio; Sen, Mihir; Ramos, Eduardo

1988-04-01

116

Climb of Prismatic Loops in Cu--Al Alloys During Irradiation in the HVEM.  

National Technical Information Service (NTIS)

Nucleation and growth of prismatic interstitial loops was observed during irradiation in the HVEM at different temperatures and damage rates. The loops remained rhombus shaped throughout growth, with sides lying on (111) planes, suggesting low jog densiti...

T. Kosel J. Washburn

1975-01-01

117

Comparative study of decay ratios of disturbance-rejection magnitude optimum method for PI controllers.  

PubMed

One of the key time-domain closed-loop performance requirements is the closed-loop response decay ratio. In this paper, the decay ratios of the disturbance-rejection magnitude optimum (DRMO) tuning method [Vranci? D, Strmcnik S, Kocijan J. Improving disturbance rejection of PI controllers by means of the magnitude optimum method. ISA Trans 2004; 43: 73-84; Vranci? D, Strmcnik S. Achieving optimal disturbance rejection by using the magnitude optimum method. In: Pre-prints of the CSCC'99 conference. 1999. p. 3401-6] are analyzed and compared to decay ratios of two other modern tuning methods, i.e. the Kappa-Tau tuning method (based on time-domain step-response characteristics) [Aström KJ, Högglund T. PID controllers: Theory, design, and tuning. 2nd ed. Instrument Society of America; 1995] and the non-convex optimization tuning method (based on frequency response) [Panagopoulos H, Aström KJ, Hägglund T. Design of PI controllers based on non-convex optimization. Automatica 1998; 34: 585-601; Panagopoulos H, Aström KJ, Hägglund T. Design of PID controllers based on constrained optimisation. IEE Proc Control Theory Appl 2002; 149 (1): 32-40]. It is shown that the DRMO method results in such a closed-loop response that the decay ratio is within a relatively narrow interval when compared to the other two methods. PMID:17706651

Lumbar, Satja; Vranci?, Damir; Strmcnik, Stanko

2008-01-01

118

Fast flux locked loop  

DOEpatents

A flux locked loop for providing an electrical feedback signal, the flux locked loop employing radio-frequency components and technology to extend the flux modulation frequency and tracking loop bandwidth. The flux locked loop of the present invention has particularly useful application in read-out electronics for DC SQUID magnetic measurement systems, in which case the electrical signal output by the flux locked loop represents an unknown magnetic flux applied to the DC SQUID.

Ganther, Jr., Kenneth R. (Olathe, KS); Snapp, Lowell D. (Independence, MO)

2002-09-10

119

OPE for super loops  

NASA Astrophysics Data System (ADS)

We extend the Operator Product Expansion for Null Polygon Wilson loops to the Mason-Skinner-Caron-Huot super loop dual to non MHV gluon amplitudes. We explain how the known tree level amplitudes can be promoted into an infinite amount of data at any loop order in the OPE picture. As an application, we re-derive all one loop NMHV six gluon amplitudes by promoting their tree level expressions. We also present some new all loops predictions for these amplitudes.

Sever, Amit; Vieira, Pedro; Wang, Tianheng

2011-11-01

120

The preprocessed doacross loop  

NASA Technical Reports Server (NTRS)

Dependencies between loop iterations cannot always be characterized during program compilation. Doacross loops typically make use of a-priori knowledge of inter-iteration dependencies to carry out required synchronizations. A type of doacross loop is proposed that allows the scheduling of iterations of a loop among processors without advance knowledge of inter-iteration dependencies. The method proposed for loop iterations requires that parallelizable preprocessing and postprocessing steps be carried out during program execution.

Saltz, Joel H.; Mirchandaney, Ravi

1990-01-01

121

Optimum Suction Distribution for Transition Control  

NASA Technical Reports Server (NTRS)

The optimum suction distribution which gives the longest laminar region for a given total suction is computed. The goal here is to provide the designer with a method to find the best suction distribution subject to some overall constraint applied to the suction. We formulate the problem using the Lagrangian multiplier method with constraints. The resulting non-linear system of equations is solved using the Newton-Raphson technique. The computations are performed for a Blasius boundary layer on a flat-plate and crossflow cases. For the Blasius boundary layer, the optimum suction distribution peaks upstream of the maximum growth rate region and remains flat in the middle before it decreases to zero at the end of the transition point. For the stationary and travelling crossflow instability, the optimum suction peaks upstream of the maximum growth rate region and decreases gradually to zero.

Balakumar, P.; Hall, P.

1996-01-01

122

learning shapes  

NSDL National Science Digital Library

Identify, descirbe, and create simple geometric figures. This is a fun way to introduce the basic shapes to students through interactive activities. Find out about different shaes from the following link: draw me shapes Have fun with shapes with the following links: puzzle draw shapes Sesame Street Finish up the day by making some books: book ...

Grimnes, Mrs.

2007-10-17

123

Shape Builder  

NSDL National Science Digital Library

This interactive Java applet allows users to explore the relationship between area and perimeter of both rectangles and irregular shapes. In the "Auto Draw" mode a shape is given, and the user finds the area and the perimeter. In the "Create Shape" mode users create their own shape and give the area and perimeter of that shape. The activity allows users to explore the relationship between shapes with a fixed perimeter and variable area or shapes with a a fixed area and variable perimeter. An optional scoring feature allows users to keep track of the number correct.

2005-01-01

124

Optimum Detection of Frequency-Hopped Signals  

NASA Technical Reports Server (NTRS)

This paper derives and analyzes optimum and near-optimum structures for detecting frequency-hopped (FH) signals with arbitrary modulation in additive white Gaussian noise. The principalmodulation formats considered are M-ary frequency-shift-keying (MFSK) with fast frequency hopping(FFH) wherein a single tone is transmitted per hop, and slow frequency hopping (SFH) with multipleMFSK tones (data symbols) per hop. The SFH detection category has not previously been addressedin the open literature and its analysis is generally more complex than FFH.

Cheng, Unjeng; Levitt, Barry; Polydoros, Andreas; Simon, Marvin K.

1992-01-01

125

Shape Up  

NSDL National Science Digital Library

Get a better understanding of the importance of our basic geometric shapes. While going through the activity below see if you can create the following shapes: A triangle, square, parallelogram, trapezoid, rectangle, kite, diamond. Having fun with quadrilaterals Now that you can create basic shapes see if you can create more difficult shapes on the geoboard. Geoboard Activity See if you can use the geoboard to create 3-D shapes ...

Carter, Mr. S.

2006-10-23

126

Magnetic loop emergence within a granule  

NASA Astrophysics Data System (ADS)

Aims: We investigate the temporal evolution of magnetic flux emerging within a granule in the quiet-Sun internetwork at disk center. Methods: We combined IR spectropolarimetry of high angular resolution performed in two Fe i lines at 1565 nm with speckle-reconstructed G-band imaging. We determined the magnetic field parameters by a LTE inversion of the full Stokes vector using the SIR code, and followed their evolution in time. To interpret the observations, we created a geometrical model of a rising loop in 3D. The relevant parameters of the loop were matched to the observations where possible. We then synthesized spectra from the 3D model for a comparison to the observations. Results: We found signatures of magnetic flux emergence within a growing granule. In the early phases, a horizontal magnetic field with a distinct linear polarization signal dominated the emerging flux. Later on, two patches of opposite circular polarization signal appeared symmetrically on either side of the linear polarization patch, indicating a small loop-like structure. The mean magnetic flux density of this loop was roughly 450 G, with a total magnetic flux of around 3 × 1017 Mx. During the ~12 min episode of loop occurrence, the spatial extent of the loop increased from about 1 to 2 arcsec. The middle part of the appearing feature was blueshifted during its occurrence, supporting the scenario of an emerging loop. There is also clear evidence for the interaction of one loop footpoint with a preexisting magnetic structure of opposite polarity. The temporal evolution of the observed spectra is reproduced to first order by the spectra derived from the geometrical model. During the phase of clearest visibility of the loop in the observations, the observed and synthetic spectra match quantitatively. Conclusions: The observed event can be explained as a case of flux emergence in the shape of a small-scale loop. The fast disappearance of the loop at the end could possibly be due to magnetic reconnection.

Gömöry, P.; Beck, C.; Balthasar, H.; Rybák, J.; Ku?era, A.; Koza, J.; Wöhl, H.

2010-02-01

127

A Unified Approach to Optimum Frame Synchronization  

Microsoft Academic Search

In this paper, we present a unified approach for optimum frame synchronization where the observed symbols are modeled as the output of a Markov chain corrupted by additive white Gaussian noise (AWGN). This model encompasses many different frame synchronization situations e.g., convolutionally coded transmissions and nonlinear modulations with memory, such as continuous-phase modulation. The proposed frame synchronizer is implemented with

Heon Huh; James V. Krogmeier

2006-01-01

128

Concerning Optimum Frequencies for Space Vehicle Communication  

Microsoft Academic Search

Optimum frequencies for the varied needs of space vehicle communication can best be determined from the estimated system performance. Each of the contributing equipment and propagation factors over the range of the radio frequency spectrum affects the minimum tolerable signal-to-noise power ratio at the receiver. Over the range of the radio frequency spectrum, the behavior of the individual building blocks,

S. Perlman; L. Kelley; W. Russell; W. Stuart

1959-01-01

129

Optimum Watermark Detection in Color Images  

Microsoft Academic Search

This work concentrates on the problem of watermarking embedding and optimum detection in color images through the use of spread spectrum techniques, both in spa ce (Direct Sequence Spread Spectrum or DSSS) and frequency (Frequency Hopping). It is applied to RGB and opponent color component representations. Perceptive information is considered in both color systems. Some tests are performed in order

Elisa Sayrol; Josep Vidal; Silvia Cabanillas; Sonia Santamaria

1999-01-01

130

Optimum Classification in Subband Coding of Images  

Microsoft Academic Search

This paper investigates the classification technique, applied to subband coding of images, as a way of exploiting the non-stationary nature of image subbands. An algorithm for maximizing the classification gain, is presented. Each subband is optimally classified and the classification map is sent as side information. After optimum rate allocation, the classes are encoded using arithmetic and trellis coded quantization

Rajan L. Joshi; Thomas R. Fischer; Roberto H. Bamberger

1994-01-01

131

Optimum Integration of Aircraft Navigation Systems  

Microsoft Academic Search

A current problem in aircraft navigation is determining how to effect alow cost navigation system consistent with required mission operationswhich will render a high degree of accuracy and reliability. One wayto achieve this is through optimum integration of equipment,subsystems, and computer mechanizations. Consistent with this approach,the overall objectives of this paper are to show the advantages of anoptimally integrated aircraft

William Zimmerman

1969-01-01

132

Optimum table spacing in predistorting amplifier linearizers  

Microsoft Academic Search

Radio frequency (RF) power amplifiers require linearization to reduce the intermodulation (IM) power if the signal does not have a constant envelope. Digital predistortion (PD) is one of the more successful methods. However, implementations usually employ uniform spacing of the PD lookup table entries, since the question of optimum nonuniform spacing has been unresolved. This paper provides the solution: a

James K. Cavers

1999-01-01

133

Optimum table spacing in predistorting amplifier linearizers  

Microsoft Academic Search

Radio frequency (RF) power amplifiers require lin- earization to reduce the intermodulation (IM) power if the signal does not have a constant envelope. Digital predistortion (PD) is one of the more successful methods. However, implementations usually employ uniform spacing of the PD lookup table entries, since the question of optimum nonuniform spacing has been unresolved. This paper provides the solution:

James K. Cavers

1999-01-01

134

Calculations enable optimum design of magnetic brake  

NASA Technical Reports Server (NTRS)

Mathematical analysis and computations determine optimum magnetic coil configurations for a magnetic brake which controllably decelerates a free falling load to a soft stop. Calculations on unconventionally wound coils determine the required parameters for the desired deceleration with minimum electrical energy supplied to the stationary coil.

Kosmahl, H. G.

1966-01-01

135

Lorentz self-forces on curved current loops  

SciTech Connect

A derivation is presented for the Lorentz self-force arising from the interaction of a slender current loop of arbitrary shape with its own magnetic field. The self-force on any loop segment depends explicitly on the global shape of the remainder of the loop. Calculations of the self-force are presented for various model loops. For loops having small to moderate noncircularity, it is shown that the self-force on a segment with local major ([ital R]) and minor ([ital a]) radii is approximately that for an axisymmetric torus having uniform [ital R] and [ital a]. These properties of the self-force critically influence the equilibrium and dynamics of thin current loops in solar and astrophysical plasmas.

Garren, D.A.; Chen, J. (Beam Physics Branch, Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States))

1994-10-01

136

Preisach modeling of piezoceramic and shape memory alloy hysteresis  

Microsoft Academic Search

Smart materials such as piezoceramics and shape memory alloys (SMAs) exhibit significant hysteresis and in order to estimate the effect on open and closed loop control a suitable model is needed. One promising candidate is the Preisach independent domain hysteresis model that is characterized by the congruent minor loop and wiping out properties. Comparable minor loop and decaying oscillation test

Declan Hughes; John T. Wen

1995-01-01

137

Optimum design of hierarchical stiffened shells for low imperfection sensitivity  

NASA Astrophysics Data System (ADS)

A concept of hierarchical stiffened shell is proposed in this study, aiming at reducing the imperfection sensitivity without adding additional weight. Hierarchical stiffened shell is composed of major stiffeners and minor stiffeners, and the minor stiffeners are generally distributed between adjacent major stiffeners. For various types of geometric imperfections, e.g., eigenmode-shape imperfections, hierarchical stiffened shell shows significantly low imperfection sensitivity compared to traditional stiffened shell. Furthermore, a surrogate-based optimization framework is proposed to search for the hierarchical optimum design. Then, two optimum designs based on two different optimization objectives (including the critical buckling load and the weighted sum of collapse loads of geometrically imperfect shells with small- and large-amplitude imperfections) are compared and discussed in detail. The illustrative example demonstrates the inherent superiority of hierarchical stiffened shells in resisting imperfections and the effectiveness of the proposed framework. Moreover, the decrease of imperfection sensitivity can finally be converted into a decrease of structural weight, which is particularly important in the development of large-diameter launch vehicles.

Wang, Bo; Hao, Peng; Li, Gang; Zhang, Jia-Xin; Du, Kai-Fan; Tian, Kuo; Wang, Xiao-Jun; Tang, Xiao-Han

2014-03-01

138

Climate Feedback Loops  

NSDL National Science Digital Library

This is the seventh of nine lessons in the 'Visualizing and Understanding the Science of Climate Change' website. This lesson addresses climate feedback loops and how these loops help drive and regulate Earth's unique climate system.

Researchers, King'S C.

139

Shape Up!  

NSDL National Science Digital Library

In this lesson students will compare two and three dimensional shapes (circle, square, triangle, rectangle, cone, cylinder, sphere, cube) by differentiating them according to attributes. Students explain attributes of shapes by exploring real world objects.

2013-01-21

140

Leaf Shape  

NSDL National Science Digital Library

This illustrated guide is designed to help students recognize and learn the different types of leaf shapes. The single Web page, which can be easily printed for use at field sites, shows five leaf shapes.

141

Stable Shapes  

NSDL National Science Digital Library

In this activity (located on page 9 of PDF), learners compare the stability of a triangle- and square-shaped structure. Learners use straws and paper clips to construct the shapes and then press down on the tops to see which shape collapses. Learners are then encouraged to build stronger shapes, perhaps by using diagonal cross-pieces as triangular bases. Use this activity to introduce compression force and structural stability.

Museum, Chicago C.

2008-01-01

142

Vertex operators of super Wilson loops  

NASA Astrophysics Data System (ADS)

We study the supersymmetric Wilson loop as introduced by Caron-Huot, which attaches to lightlike polygons certain edge and vertex operators, whose shape is determined by supersymmetry constraints. We state explicit formulas for the vertex operators to all orders in the Graßmann expansion, thus filling a gap in the literature. This is achieved by deriving a recursion formula out of the supersymmetry constraints.

Groeger, Josua

2012-11-01

143

Ultra wideband L-loop antenna  

Microsoft Academic Search

The antenna design for ultra wideband (UWB) signal radiation is one of the main challenges of the UWB system, especially when low-cost, geometrically small and radio efficient structures are required for typical applications. This study presents a novel printed loop antenna with introducing an L shape portion to its arms. The antenna offers excellent performance for lower-band frequency of UWB

K. Y. Yazdanboost; R. Kohno

2005-01-01

144

Analysis of wasp-waisted hysteresis loops in magnetic rocks.  

PubMed

The random-field Ising model of hysteresis is generalized to dilute magnets and is solved on a Bethe lattice. Exact expressions for the major and minor hysteresis loops are obtained. In the strongly dilute limit the model provides a simple and useful understanding of the shapes of hysteresis loops in magnetic rock samples. PMID:22400529

Kharwanlang, R S; Shukla, Prabodh

2012-01-01

145

Large lithium loop experience  

Microsoft Academic Search

An engineering design and operating experience of a large, isothermal, lithium-coolant test loop are presented. This liquid metal coolant loop is called the Experimental Lithium System (ELS) and has operated safely and reliably for over 6500 hours through September 1981. The loop is used for full-scale testing of components for the Fusion Materials Irradiation Test (FMIT) Facility. Main system parameters

R. Kolowith; T. J. Owen; J. D. Berg; J. M. Atwood

1981-01-01

146

Data Shapes  

NSDL National Science Digital Library

This activity asks students to recognize differences in shapes and sort them. They are given a set of 15 shape cards that they can sort by the criteria of color, size and shape. Ideas for implementation, extension and support are included along with a printable sheet of the cards.

2011-10-01

147

Shape complexity  

Microsoft Academic Search

The complexity of 3D shapes that are represented in digital form and processed in CAD\\/CAM\\/CAE, entertainment, biomedical, and other applications has increased considerably. Much research was focused on coping with or on reducing shape complexity. But, what exactly is shape complexity? We discuss several complexity measures and the corresponding complexity reduction techniques. Algebraic complexity measures the degree of polynomials needed

Jarek Rossignac

2005-01-01

148

VOLT: the Victoria Open Loop Testbed  

NASA Astrophysics Data System (ADS)

The Victoria Open Loop Testbed (VOLT) serves as a demonstration of open loop control both on-sky (at the Dominion Astrophysical Observatory's 1.2m telescope) and in the lab in order to facilitate the future development of Multi-Object Adaptive Optics (MOAO). MOAO, when combined with multiple deployable integral field units, is a concept which promises to deliver near diffraction-limited images over a large field of view. Astronomers will be able to use the multiplex advantage of MOAO instruments to mount large, detailed surveys of galaxies and star formation regions. However, several challenges await MOAO instrument designers. The greatest of these is implementing open loop control in an astronomical adaptive optics (AO) system. Almost all astronomical AO systems to date have used some form of closed loop control, in which the wavefront sensors (WFSs) measure a residual wavefront error after the deformable mirror (DM) has taken on its commanded shape. WFSs in an open loop system can be spatially separated from the DM, but doing so creates new challenges, some known and some unknown. Uncertainties springing from open loop control pose the greatest risk to the design of a MOAO instrument. To mitigate this risk, we have designed and built VOLT, a simple on-axis open loop adaptive optics system. We describe several sources of open loop error, and our measurements of their expected contribution to the VOLT performance. Finally we present observations of a bright star, showing that VOLT, operating in open loop, was able to significantly improve the image quality from 2.5 arcseconds to 0.5 arcseconds in I-band, consistent with our estimates of the wavefront errors. We also present the open loop rejection transfer function for VOLT based on both on-sky and lab measurements.

Andersen, David R.; Fischer, Michael; Conan, Rodolphe; Fletcher, Murray; Véran, Jean-Pierre

2008-07-01

149

An approach to optimum subsonic inlet design  

NASA Technical Reports Server (NTRS)

Inlet operating requirements are compared with estimated inlet separation characteristics to identify the most critical inlet operating condition. This critical condition is taken to be the design point and is defined by the values of inlet mass flow, free-stream velocity and inlet angle of attack. Optimum flow distributions on the inlet surface were determined to be a high, flat top Mach number distribution on the inlet lip to turn the flow quickly into the inlet and a flat bottom skin-friction distribution on the diffuser wall to diffuse the flow rapidly and efficiently to the velocity required at the fan face. These optimum distributions are then modified to achieve other desirable flow characteristics. Example applications are given.

Luidens, R. W.; Stockman, N. O.; Diedrich, J. H.

1978-01-01

150

Optimum spectral bands for rock discrimination  

NASA Technical Reports Server (NTRS)

Using stepwise discriminant analysis on spectral reflectance and spectral emissivity data collected by a Multispectral Scanner and Data System, mounted in an NC-130B aircraft and flown at an altitude of approximately 3 km, spectral bands were ranked as to their usefulness in separating specific rock types and rock alteration products in seven geologically diverse Utah sites. The optimum band for rock discrimination included the 1.18 to 1.30 micron interval, and the optimum combination of bands comprised the 1.18 to 1.30, 4.50 to 4.75, 0.46 to 0.50, 1.52 to 1.73, and 2.10 to 2.36 micron intervals. It is concluded that the spectral interval combination was more successful in differentiating geologic materials than either simulated Multispectral Scanner bands or simulated Thematic Mapper bands.

Siegrist, A. W.; Schnetzler, C. C.

1980-01-01

151

Hysteresis-Loop Overskewing  

NASA Astrophysics Data System (ADS)

The performance of permanent magnets is largely determined by the magnetostatic energy stored in free space (energy product), which depends on both materials properties and magnet geometry. The latter usually differs from laboratory shapes such as spherical samples, and demagnetizing-field corrections must be applied to compare different geometries. However, in nanostructures, especially in thin films, the macroscopic demagnetizing factors D predicted from Maxwell's equations [1] yield unphysical overskewed hysteresis loops [2]. The overskewing is probably a nanoscale effect, but its origin has remained controversial. Our explanation is that nanoscale magnetization processes violate a main condition for the applicability of macroscopy demagnetizing factors, namely the uniform character of the magnetization. In bulk magnets, the magnetization inhomogeneities effectively average to zero, but this is no longer the case if any of the dimension of the magnet becomes small. We explicitly consider granular thin films, where we find a real-structure dependent reduction D, as contrasted to the sometimes assumed infinite slope M(H) at coercivity. --- This research is supported by BREM (RS), ARPA-E, DOE (DJS), and NCMN. --- References: [1] J. A. Osborn, Phys. Rev. 67, 351 (1945); [2] R. Skomski, J.- P. Liu, and D. J. Sellmyer, Phys. Rev. B 60, 7359 (1999).

Skomski, Ralph; George, T. A.; Sellmyer, D. J.

2011-03-01

152

Optimum routing of a sailing wind farm  

Microsoft Academic Search

To acquire the wind energy of the oceans, a sailing wind farm has been proposed. The wind farm considered is composed of a\\u000a semisubmersible floating structure, 11 windmills, four sails, six thrusters, and storage for hydrogen. To maximize the acquired\\u000a energy, an effective algorithm to search for optimum routes was developed. The algorithm is based on the fact that beam

Masaru Tsujimoto; Takashi Uehiro; Hiroshi Esaki; Takeshi Kinoshita; Ken Takagi; Susumu Tanaka; Hiroshi Yamaguchi; Hideo Okamura; Masuho Satou; Yoshimasa Minami

2009-01-01

153

Supervised method for optimum hyperspectral band selection  

NASA Astrophysics Data System (ADS)

Much effort has been devoted to development of methods to reduce hyperspectral image dimensionality by locating and retaining data relevant for image interpretation while discarding that which is irrelevant. Irrelevance can result from an absence of information that could contribute to the classification, or from the presence of information that could contribute to the classification but is redundant with other information already selected for inclusion in the classification process. We describe a new supervised method that uses mutual information to incrementally determine the most relevant combination of available bands and/or derived pseudo bands to differentiate a specified set of classes. We refer to this as relevance spectroscopy. The method identifies a specific optimum band combination and provides estimates of classification accuracy for data interpretation using a complementary, also information theoretic, classification procedure. When modest numbers of classes are involved the number of relevant bands to achieve good classification accuracy is typically three or fewer. Time required to determine the optimum band combination is of the order of a minute on a personal computer. Automated interpretation of intermediate images derived from the optimum band set can often keep pace with data acquisition speeds.

McConnell, Robert K.

2013-05-01

154

Chen Integrals, Generalized Loops and Loop Calculus  

NASA Astrophysics Data System (ADS)

We use Chen iterated line integrals to construct a topological algebra {A}p of separating functions on the group of loops L?p. {A}p has a Hopf algebra structure which allows the construction of a group structure on its spectrum. We call this topological group the group of generalized loops widetilde {{L} {M}p } Then we develop a loop calculus, based on the end point and area derivative operators, providing a rigorous mathematical treatment of the early heuristic ideas of Gambini, Trias and also Mandelstam, Makeenko and Migdal. Finally, we define a natural action of the “pointed” diffeomorphism group Diffp(?) on widetilde {{L} {M}p }, and consider a variational derivative which allows the construction of homotopy invariants. This formalism is useful for constructing a mathematical theory of loop representation of gauge theories and quantum gravity.

Tavares, J. N.

155

Shape Tool  

NSDL National Science Digital Library

This virtual manipulative allows you to create geometric shapes. Squares, triangles, rhombi, trapezoids and hexagons can be created, colored, enlarged, shrunk, rotated, reflected, sliced, and glued together.

Math, Illuminations N.

2009-01-15

156

Development of PC (Pair Cross) Mill Shape Control System.  

National Technical Information Service (NTIS)

In the development of roll cross type hot rolling mill (PC mill), Mitsubishi developed the control system capable of setting optimum cross angles according to the rolling conditions, removing the strip shape and crown fluctuations occurring during rolling...

Y. Hayama J. Nishizaki T. Kajiwara M. Abe K. Okura

1985-01-01

157

A comparative approach to closed-loop computation.  

PubMed

Neural computation is inescapably closed-loop: the nervous system processes sensory signals to shape motor output, and motor output consequently shapes sensory input. Technological advances have enabled neuroscientists to close, open, and alter feedback loops in a wide range of experimental preparations. The experimental capability of manipulating the topology-that is, how information can flow between subsystems-provides new opportunities to understand the mechanisms and computations underlying behavior. These experiments encompass a spectrum of approaches from fully open-loop, restrained preparations to the fully closed-loop character of free behavior. Control theory and system identification provide a clear computational framework for relating these experimental approaches. We describe recent progress and new directions for translating experiments at one level in this spectrum to predictions at another level. Operating across this spectrum can reveal new understanding of how low-level neural mechanisms relate to high-level function during closed-loop behavior. PMID:24709601

Roth, E; Sponberg, S; Cowan, N J

2014-04-01

158

Major hysteresis loop modeling of two-dimensional arrays of single domain particles  

Microsoft Academic Search

We have studied the effect of magnetostatic interactions on the overall shape of hysteresis loops for arrays of single domain particles. A computational model was used to calculate major hysteresis loops of arrays of particles with an easy axis along the applied field. The shear of the hysteresis loop, and consequent loss of squareness, is found to increase both with

M. Hwang; M. Farhoud; Y. Hao; M. Walsh; T. A. Savas; Henry I. Smith; C. A. Ross

2000-01-01

159

Two novel automatic frequency tracking loops  

NASA Technical Reports Server (NTRS)

Two automatic-frequency-control (AFC) loops are introduced and analyzed in detail. The algorithms are generalizations of the well known cross-product AFC loop with improved performance. The first estimator uses running overlapping discrete Fourier transforms to create a discriminator curve proportional to the frequency estimation error, whereas the second one preprocesses the received data and then uses an extended Kalman filter to estimate the input frequency. The algorithms are tested by computer simulations in a highly dynamic environment at low carrier/noise ratio (CNR). The algorithms are suboptimum tracking schemes with a larger frequency-error variance compared to an optimum strategy, but they offer simplicity of mechanization and a CNR with a very low operating threshold.

Aguirre, Sergio; Hinedi, Sami

1989-01-01

160

Equilibrium Models of Coronal Loops That Involve Curvature and Buoyancy  

NASA Astrophysics Data System (ADS)

We construct magnetostatic models of coronal loops in which the thermodynamics of the loop is fully consistent with the shape and geometry of the loop. This is achieved by treating the loop as a thin, compact, magnetic fibril that is a small departure from a force-free state. The density along the loop is related to the loop's curvature by requiring that the Lorentz force arising from this deviation is balanced by buoyancy. This equilibrium, coupled with hydrostatic balance and the ideal gas law, then connects the temperature of the loop with the curvature of the loop without resorting to a detailed treatment of heating and cooling. We present two example solutions: one with a spatially invariant magnetic Bond number (the dimensionless ratio of buoyancy to Lorentz forces) and the other with a constant radius of the curvature of the loop's axis. We find that the density and temperature profiles are quite sensitive to curvature variations along the loop, even for loops with similar aspect ratios.

Hindman, Bradley W.; Jain, Rekha

2013-12-01

161

PID controller auto-tuning based on process step response and damping optimum criterion.  

PubMed

This paper presents a novel method of PID controller tuning suitable for higher-order aperiodic processes and aimed at step response-based auto-tuning applications. The PID controller tuning is based on the identification of so-called n-th order lag (PTn) process model and application of damping optimum criterion, thus facilitating straightforward algebraic rules for the adjustment of both the closed-loop response speed and damping. The PTn model identification is based on the process step response, wherein the PTn model parameters are evaluated in a novel manner from the process step response equivalent dead-time and lag time constant. The effectiveness of the proposed PTn model parameter estimation procedure and the related damping optimum-based PID controller auto-tuning have been verified by means of extensive computer simulations. PMID:24035643

Pavkovi?, Danijel; Polak, Siniša; Zorc, Davor

2014-01-01

162

Nonlinear Kink Oscillations of Coronal Magnetic Loops  

NASA Astrophysics Data System (ADS)

We studied nonlinear kink oscillations of a thin magnetic tube using the cold-plasma approximation. We assumed that the plasma density varies along the tube but does not vary in the radial direction. Using the regular perturbation method, we show that the nonlinearity does not affect the oscillation amplitude. We also calculated the nonlinear correction to the oscillation frequency, which is proportional to the oscillation amplitude squared. As an example, we considered nonlinear oscillations of a coronal magnetic loop of half-circle shape in an isothermal atmosphere with equal plasma temperatures inside and outside the loop.

Ruderman, M. S.; Goossens, M.

2014-06-01

163

Molecule Shapes  

NSDL National Science Digital Library

Explore molecule shapes by building molecules in 3D! How does molecule shape change with different numbers of bonds and electron pairs? Find out by adding single, double or triple bonds and lone pairs to the central atom. Then, compare the model to real molecules!

Simulations, Phet I.; Moore, Emily; Olson, Jonathan; Lancaster, Kelly; Chamberlain, Julia; Perkins, Kathy

2011-10-10

164

Schapiro Shapes  

ERIC Educational Resources Information Center

This article describes a lesson on Schapiro Shapes. Schapiro Shapes is based on the art of Miriam Schapiro, who created a number of works of figures in action. Using the basic concepts of this project, students learn to create their own figures and styles. (Contains 1 online resource.)

O'Connell, Emily

2009-01-01

165

Strong Shapes  

NSDL National Science Digital Library

Is a square stronger than a triangle? Use tongue depressors to build simple shapes. Then apply a little weight to them and see what happens! This activity comes with useful tips for building the shapes, like how to drill the wood without cracking it, and what drill works best.

Minnesota, Science M.

1995-01-01

166

Optimum interface properties for metal matrix composites  

NASA Technical Reports Server (NTRS)

Due to the thermal expansion coefficient mismatch (CTE) between the fiber and the matrix, high residual sresses exist in metal matrix composite systems upon cool down from processing temperature to room temperature. An interface material can be placed between the fiber and the matrix to reduce the high tensile residual stresses in the matrix. A computer program was written to minimize the residual stress in the matrix subject to the interface material properties. The decision variables are the interface modulus, thickness and thermal expansion coefficient. The properties of the interface material are optimized such that the average distortion energy in the matrix and the interface is minimized. As a result, the only active variable is the thermal expansion coefficient. The optimum modulus of the interface is always the minimum allowable value and the interface thickness is always the maximum allowable value, independent of the fiber/matrix system. The optimum interface thermal expansion coefficient is always between the values of the fiber and the matrix. Using this analysis, a survey of materials was conducted for use as fiber coatings in some specific composite systems.

Ghosn, Louis J.; Lerch, Bradley A.

1989-01-01

167

Shapes lab  

NSDL National Science Digital Library

This online activity features two simulations demonstrating the comparative strengths of rectangles, arches, and triangles when stress is applied at a point. Simulations offer a simplified version of real life conditions related to the strength and stability of structures. For comparison's sake, each tested shape is of equivalent thickness and has hinged joints. The shapes show load distribution arrows when force is applied. In one simulation, a student selects a shape and initiates a dynamic illustration, providing an explanation of the effect of applying force and demonstrating how the shape can be strengthened. The second simulation shows and explains what results when increasing numbers of elephants are stacked on each of the three shapes. Copyright 2005 Eisenhower National Clearinghouse

Wgbh

2001-01-01

168

THE IMPORTANCE OF GEOMETRIC EFFECTS IN CORONAL LOOP MODELS  

SciTech Connect

We systematically investigate the effects of geometrical assumptions in one-dimensional (1D) models of coronal loops. Many investigations of coronal loops have been based on restrictive assumptions, including symmetry in the loop shape and heating profile, and a uniform cross-sectional area. Starting with a solution for a symmetric uniform-area loop with uniform heating, we gradually relax these restrictive assumptions to consider the effects of nonuniform area, nonuniform heating, a nonsymmetric loop shape, and nonsymmetric heating, to show that the character of the solutions can change in important ways. We find that loops with nonuniform cross-sectional area are more likely to experience thermal nonequilibrium, and that they produce significantly enhanced coronal emission, compared with their uniform-area counterparts. We identify a process of incomplete condensation in loops experiencing thermal nonequilibrium during which the coronal parts of loops never fully cool to chromospheric temperatures. These solutions are characterized by persistent siphon flows. Their properties agree with observations (Lionello et al.) and may not suffer from the drawbacks that led Klimchuk et al. to conclude that thermal nonequilibrium is not consistent with observations. We show that our 1D results are qualitatively similar to those seen in a three-dimensional model of an active region. Our results suggest that thermal nonequilibrium may play an important role in the behavior of coronal loops, and that its dismissal by Klimchuk et al., whose model suffered from some of the restrictive assumptions we described, may have been premature.

Mikic, Zoran; Lionello, Roberto; Linker, Jon A. [Predictive Science, Inc., San Diego, CA 92121 (United States); Mok, Yung [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Winebarger, Amy R. [NASA Marshall Space Flight Center, Huntsville, AL 35812 (United States)

2013-08-20

169

Efficiency in the Optimum Supply of Public Goods.  

National Technical Information Service (NTIS)

This paper is concerned with the question under what circumstances is the optimum allocation of expenditures between various public goods unaffected by a certain decentralization of decision making. Specifically, when can the relative optimum levels of pu...

L. J. Lau E. Sheshinski J. E. Stiglitz

1976-01-01

170

Optimum quantum states for interferometers with fixed and moving mirrors  

SciTech Connect

We address a systematic approach to the study of the optimum states reaching maximum resolution for interferometers with moving mirrors. We find a correspondence between the optimum states for interferometers with fixed and moving mirrors.

Luis, Alfredo [Departamento de Optica, Facultad de Ciencias Fisicas, Universidad Complutense, 28040 Madrid (Spain)

2004-04-01

171

Wilson loops @ 3-loops in special kinematics  

NASA Astrophysics Data System (ADS)

We obtain a compact expression for the octagon MHV amplitude/Wilson loop at 3 loops in planar mathcal{N} = {4} SYM and in special 2d kinematics in terms of 7 unfixed coefficients. We do this by making use of the cyclic and parity symmetry of the amplitude/Wilson loop and its behaviour in the soft/collinear limits as well as in the leading term in the expansion away from this limit. We also make a natural and quite general assumption about the functional form of the result, namely that it should consist of weight 6 polylogarithms whose symbol consists of basic cross-ratios only (and not functions thereof). We also describe the uplift of this result to 10 points.

Heslop, Paul; Khoze, Valentin V.

2011-11-01

172

Optimum runway orientation relative to crosswinds  

NASA Technical Reports Server (NTRS)

Specific magnitudes of crosswinds may exist that could be constraints to the success of an aircraft mission such as the landing of the proposed space shuttle. A method is required to determine the orientation or azimuth of the proposed runway which will minimize the probability of certain critical crosswinds. Two procedures for obtaining the optimum runway orientation relative to minimizing a specified crosswind speed are described and illustrated with examples. The empirical procedure requires only hand calculations on an ordinary wind rose. The theoretical method utilizes wind statistics computed after the bivariate normal elliptical distribution is applied to a data sample of component winds. This method requires only the assumption that the wind components are bivariate normally distributed. This assumption seems to be reasonable. Studies are currently in progress for testing wind components for bivariate normality for various stations. The close agreement between the theoretical and empirical results for the example chosen substantiates the bivariate normal assumption.

Falls, L. W.; Brown, S. C.

1972-01-01

173

Optimum Grid Size for Hydrological Modeling  

NASA Astrophysics Data System (ADS)

Grids are used to account for the spatial variability and heterogeneity in a physical watershed and are established through appropriate spatial scales to characterize conditions such as topography, landuse and soil properties for hydrological modeling. The current approach for determining grid sizes are often difficult to quantify and encourages the use of equal grid size throughout the watershed regardless of the varying landscape. Studies have shown that as catchment heterogeneity and spatial variability become more complex, the hydrological processes become highly variable with varying topography. This result in a catchment within a watershed showing strong localized hydrological characteristics. In this study we introduce a novel approach to determine grid size based on landscape topography for hydrological modeling. A 30m resolution elevation and watershed boundary data obtained from USGS was used in the Patuxent Watershed. The optimum grid resolution (UCellres) was found to be a function of the catchment area (Sarea) and elevation range (ElevRange) and is expressed as: UCellres = 43.339 + 0.00000002Sarea - 0.0807ElevRange. The GLM model showed a non-linear inverse, relationship between the optimum grid and elevation range indicating decreasing elevation range with increasing grid sizes. A statistical analysis of the model gave an RMSE of 0.9, a coefficient of variation of 0.07 and a relative error of 0.02. The GLM was applied to a neighboring watershed and results showed that each catchment can have unique grid sizes relative to its topography within the watershed. This finding indicate that in topography dominated watershed, individual catchments can be reasonably analyzed at different grid sizes on a localize scale to effectively model the hydrology of a watershed.

Damalie, R.; Yoon, J.

2012-12-01

174

Falling Loop Model  

NSDL National Science Digital Library

The EJS Falling Loop Model shows a conducting loop falling out of a uniform magnetic field. Users can change the size and orientation of the loop. If Ejs is installed, right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item allows for editing of the model. The Falling Loop model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_em_FallingLoop.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Cox, Anne

2009-09-24

175

Balancing Shapes  

NSDL National Science Digital Library

"Students will balance shapes on the pan balance applet to study equality, essential to understanding algebra. Equivalent relationships will be recognized when the pans balance, demonstrating the properties of equality." (from NCTM's Illuminations)

Mathematics, Illuminations N.

2009-10-26

176

Shapely Lines  

NSDL National Science Digital Library

This activity gives students practice drawing straight lines with a ruler and looking for and categorizing shapes, for example, by the number of sides in polygons. The Teachers' Notes page includes suggestions for implementation, discussion questions and ideas for extension.

2010-06-01

177

String Shapes  

NSDL National Science Digital Library

In this activity, learners work together to make polygons (many-sided shapes) with string. Learners sit on the floor and hold onto a piece of string slid between their thumbs and index fingers. Learners explore how many different kinds of triangles and other shapes they can make by changing their hand positions. Use this activity to help learners explore polygons including convex and concave polygons and vertices.

Exploratorium

2010-01-01

178

Skeleton Shapes  

NSDL National Science Digital Library

This activity gives students an opportunity to explore some of the common 3-D shapes and their names and properties. After discussion and an example, it asks students to count the required number of edges and vertices (corners) to build each of 5 given shapes. The Teachers' Notes page includes suggestions for implementation, discussion questions, ideas for extension and support, and a printable recording sheet (pdf).

2003-02-01

179

An integrated optimum design approach for high speed prop rotors  

NASA Technical Reports Server (NTRS)

The objective is to develop an optimization procedure for high-speed and civil tilt-rotors by coupling all of the necessary disciplines within a closed-loop optimization procedure. Both simplified and comprehensive analysis codes are used for the aerodynamic analyses. The structural properties are calculated using in-house developed algorithms for both isotropic and composite box beam sections. There are four major objectives of this study. (1) Aerodynamic optimization: The effects of blade aerodynamic characteristics on cruise and hover performance of prop-rotor aircraft are investigated using the classical blade element momentum approach with corrections for the high lift capability of rotors/propellers. (2) Coupled aerodynamic/structures optimization: A multilevel hybrid optimization technique is developed for the design of prop-rotor aircraft. The design problem is decomposed into a level for improved aerodynamics with continuous design variables and a level with discrete variables to investigate composite tailoring. The aerodynamic analysis is based on that developed in objective 1 and the structural analysis is performed using an in-house code which models a composite box beam. The results are compared to both a reference rotor and the optimum rotor found in the purely aerodynamic formulation. (3) Multipoint optimization: The multilevel optimization procedure of objective 2 is extended to a multipoint design problem. Hover, cruise, and take-off are the three flight conditions simultaneously maximized. (4) Coupled rotor/wing optimization: Using the comprehensive rotary wing code CAMRAD, an optimization procedure is developed for the coupled rotor/wing performance in high speed tilt-rotor aircraft. The developed procedure contains design variables which define the rotor and wing planforms.

Chattopadhyay, Aditi; Mccarthy, Thomas R.

1995-01-01

180

Shape memory effect heat engine performance  

Microsoft Academic Search

The performance of a shape memory effect heat engine has been evaluated taking into account the heat transfer to the working element, hysteresis effects, elasticity and heat losses. It is shown that there exists an optimum stress required for maximum power output. The maximum power output is found to increase with increasing cycle temperature difference, increasing cycle strain, increasing working

P. G. McCormick

1986-01-01

181

Effect of ideal-gas flow swirl on the optimum supersonic contour of an axisymmetric nozzle with break  

Microsoft Academic Search

The effect of swirling the flow at the nozzle inlet on the shape of the optimum supersonic section with a break at the point of intersection of the limiting characteristic and the contour is investigated within the framework of the ideal (inviscid and non-heat-conducting) gas model. A direct method based on reduction to a problem of nonlinear programming is used

G. I. Afonin; V. G. Butov

1989-01-01

182

Loops, polytopes and splines  

NASA Astrophysics Data System (ADS)

We uncover an unexpected connection between the physics of loop integrals and the mathematics of spline functions. One loop integrands are Laplace transforms of splines. This clarifies the geometry of the associated loop integrals, since a n-node spline has support on a n-vertex polyhedral cone. One-loop integrals are integrals of splines on a hyperbolic slice of the cone, yielding polytopes in AdS space. Splines thus give a geometrical counterpart to the rational function identities at the level of the integrand. Spline technology also allows for a clear, simple, algebraic decomposition of higher point loop integrals in lower dimensional kinematics in terms of lower point integrals — e.g. an hexagon integral in 2d kinematics can be written as a sum of scalar boxes. Higher loops can also be understood directly in terms of splines — they map onto spline convolutions, leading to an intriguing representation in terms of hyperbolic simplices integrated over other hyperbolic simplices. We finish with speculations on the interpretation of one-loop integrals as partition functions, inspired by the use of splines in counting points in polytopes.

Paulos, Miguel F.

2013-06-01

183

Large lithium loop experience  

SciTech Connect

An engineering design and operating experience of a large, isothermal, lithium-coolant test loop are presented. This liquid metal coolant loop is called the Experimental Lithium System (ELS) and has operated safely and reliably for over 6500 hours through September 1981. The loop is used for full-scale testing of components for the Fusion Materials Irradiation Test (FMIT) Facility. Main system parameters include coolant temperatures to 430/sup 0/C and flow to 0.038 m/sup 3//s (600 gal/min). Performance of the main pump, vacuum system, and control system is discussed. Unique test capabilities of the ELS are also discussed.

Kolowith, R.; Owen, T.J.; Berg, J.D.; Atwood, J.M.

1981-10-01

184

Optimum deposition conditions of ultrasmooth silver nanolayers  

NASA Astrophysics Data System (ADS)

Reduction of surface plasmon-polariton losses due to their scattering on metal surface roughness still remains a challenge in the fabrication of plasmonic devices for nanooptics. To achieve smooth silver films, we study the dependence of surface roughness on the evaporation temperature in a physical vapor deposition process. At the deposition temperature range 90 to 500 K, the mismatch of thermal expansion coefficients of Ag, Ge wetting layer, and sapphire substrate does not deteriorate the metal surface. To avoid ice crystal formation on substrates, the working temperature of the whole physical vapor deposition process should exceed that of the sublimation at the evaporation pressure range. At optimum room temperature, the root-mean-square (RMS) surface roughness was successfully reduced to 0.2 nm for a 10-nm Ag layer on sapphire substrate with a 1-nm germanium wetting interlayer. Silver layers of 10- and 30-nm thickness were examined using an atomic force microscope (AFM), X-ray reflectometry (XRR), and two-dimensional X-ray diffraction (XRD2).

Stefaniuk, Tomasz; Wróbel, Piotr; Górecka, Ewa; Szoplik, Tomasz

2014-03-01

185

Improve filtration for optimum equipment reliability  

SciTech Connect

The introduction 20 years ago of the American Petroleum Institute Standard API-614 as a purchase specification for lubrication, shaft sealing and control oil systems, had a considerable impact and did much to improve system reliability at that time. Today, however, these recommendations regarding filter rating and flushing cleanliness are outdated. Much research in the tribology field correlates clearance size particulate contamination with accelerated component wear, fatigue and performance degradation. Some of these studies demonstrate that by decreasing the population of clearance size particulate in lubrication oils, component life increases exponentially. Knowing the dynamic clearances of a piece of machinery makes it possible, using the ISO 4406 Cleanliness Code, to determine what cleanliness level will minimize contamination-related component wear/fatigue and thus help optimize machinery performance and reliability. Data obtained by the author through random sampling of rotating equipment lube and seal oil systems indicate that the API-614 standard, as it pertains to filtration and flushing, is insufficient to ensure that particulate contamination is maintained to within the levels necessary to achieve optimum equipment reliability and safety, without increasing operating cost. Adopting and practicing the guidelines presented should result in the following benefits: (1) the frequency of bearing, oil pump, mechanical seal, fluid coupling, gearbox and hydraulic control valve failures would be minimized; (2) the mean time between planned maintenance (MTBPM) would be increased. The result will be a substantial increase in safety and cost savings to the operator.

Cervera, S.M. [Pall Corp., Glen Cove, NY (United States)

1996-01-01

186

Optimum deposition conditions of ultrasmooth silver nanolayers  

PubMed Central

Reduction of surface plasmon-polariton losses due to their scattering on metal surface roughness still remains a challenge in the fabrication of plasmonic devices for nanooptics. To achieve smooth silver films, we study the dependence of surface roughness on the evaporation temperature in a physical vapor deposition process. At the deposition temperature range 90 to 500 K, the mismatch of thermal expansion coefficients of Ag, Ge wetting layer, and sapphire substrate does not deteriorate the metal surface. To avoid ice crystal formation on substrates, the working temperature of the whole physical vapor deposition process should exceed that of the sublimation at the evaporation pressure range. At optimum room temperature, the root-mean-square (RMS) surface roughness was successfully reduced to 0.2 nm for a 10-nm Ag layer on sapphire substrate with a 1-nm germanium wetting interlayer. Silver layers of 10- and 30-nm thickness were examined using an atomic force microscope (AFM), X-ray reflectometry (XRR), and two-dimensional X-ray diffraction (XRD2). PACS 63.22.Np Layered systems; 68. Surfaces and interfaces; thin films and nanosystems (structure and nonelectronic properties); 81.07.-b Nanoscale materials and structures: fabrication and characterization

2014-01-01

187

Optimum coding techniques for MST radars  

NASA Technical Reports Server (NTRS)

The optimum coding technique for MST (mesosphere stratosphere troposphere) radars is that which gives the lowest possible sidelobes in practice and can be implemented without too much computing power. Coding techniques are described in Farley (1985). A technique mentioned briefly there but not fully developed and not in general use is discussed here. This is decoding by means of a filter which is not matched to the transmitted waveform, in order to reduce sidelobes below the level obtained with a matched filter. This is the first part of the technique discussed here; the second part consists of measuring the transmitted waveform and using it as the basis for the decoding filter, thus reducing errors due to imperfections in the transmitter. There are two limitations to this technique. The first is a small loss in signal to noise ratio (SNR), which usually is not significant. The second problem is related to incomplete information received at the lowest ranges. An appendix shows a technique for handling this problem. Finally, it is shown that the use of complementary codes on transmission and nonmatched decoding gives the lowest possible sidelobe level and the minimum loss in SNR due to mismatch.

Sulzer, M. P.; Woodman, R. F.

1986-01-01

188

Shape Up!  

NSDL National Science Digital Library

In this activity (pages 8-9), learners investigate the properties of smart materials, which are materials that respond to things that happen around them. Learners train a piece of smart material (Nitinol) to adopt a particular shape. Learners discover that when the Nitinol wire is heated enough, its atoms can move around enough to "reset" its memory. This makes it possible to train the material to have a particular shape. Safety note: Young learners should have adult supervision. Be very careful with the flame and hot wire.

Jordan, Catherine

2012-01-01

189

Hot giant loop holography  

SciTech Connect

We argue that there is a phase transition in the expectation value of the Polyakov loop operator in the large N limit of the high temperature deconfined phase of N=4 Yang-Mills theory on a spatial S{sup 3}. It occurs for the large completely symmetric representation of the SU(N) symmetry group. We speculate that this transition is reflected in the D-branes which are the string theory duals of giant loops.

Grignani, Gianluca [Dipartimento di Fisica, Universita di Perugia, INFN Sezione di Perugia, Via A. Pascoli, 06123 Perugia (Italy); Karczmarek, Joanna L.; Semenoff, Gordon W. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada)

2010-07-15

190

Bifurcations of cuspidal loops  

Microsoft Academic Search

A cuspidal loop 0951-7715\\/10\\/6\\/001\\/img5 for a planar vector field X consists of a homoclinic orbit 0951-7715\\/10\\/6\\/001\\/img6 through a singular point p, at which X has a nilpotent cusp. This is the simplest non-elementary singular cycle (or graphic) in the sense that its singularities are not elementary (i.e. hyperbolic or semihyperbolic). Cuspidal loops appear persistently in three-parameter families of planar vector

Freddy Dumortier; Robert Roussarie; Jorge Sotomayor

1997-01-01

191

Thrown for a Loop  

NSDL National Science Digital Library

In this lesson, students begin to focus on the torque associated with a current carrying loop in a magnetic field. Students are prompted with example problems and use diagrams to visualize the vector product. In addition, students learn to calculate the energy of this loop in the magnetic field. Several example problems are included and completed as a class. A homework assignment is also attached as a means of student assessment.

VU Bioengineering RET Program, School of Engineering,

192

Noise characteristics of a dc SQUID with a resistively shunted inductance. II. Optimum damping  

SciTech Connect

Effects of a damping resistance on noise characteristics of a dc SQUID are studied theoretically, where the damping resistance is in shunt with a loop inductance of the SQUID. An analytical expression for the energy resolution of the SQUID is obtained, with which the relation between the damping resistance and the energy resolution is studied in detail. It is shown that an optimum value of the damping resistance exists, which is determined by the tradeoff between the improvement of the transfer function and the additional noise due to the damping resistance. Optimum values of the damping resistance are about twice the shunt resistance of the SQUID and vary slightly with SQUID modulation parameter ..beta... For optimum damping, the energy resolution is improved, compared with the case without the damping resistance. This means that the SQUID with large ..beta.. can be used without significant degradation of the performance, i.e., the previous restriction of ..beta.. = 1 can be loosened. The analytical results agree quantitatively with numerical ones.

Enpuku, K.; Yoshida, K.; Kohjiro, S.

1986-12-15

193

Episodic Coronal Loop Heating  

NASA Astrophysics Data System (ADS)

Coronal loop temperatures are known to be of a few millions degrees but the nature of the energy source remains as a longstanding fundamental problem for solar (and stellar) physics. Observations of solar atmospheric plasma show clear evidence of frequent very localised heating events, which may be statistically responsible for heating of the solar upper atmosphere. One heating theory indicates that these micro-scale events are driven by localized magnetic field reconnection. In this paper, we present the results of numerical calculations that describe the response of the coronal plasma to small-scale heating pulses in a magnetic loop. In particular, we study the effects of energy input pulses injected randomly near the two footpoints of a semi-circular loop. We have found that increasing the elapsing time between successive pulses, the overall loop temperature decreases. When a critical elapsing time is reached the loop can no longer be maintained at typical coronal temperatures. These features have some support from SOHO-CDS observations of coronal loops which seem to undergo strong variability especially in active regions of the solar atmosphere (Kjeldseth-Moe &Brekke, 1998). We also have found that successive random pulses can statistically maintain the average plasma temperature at typical coronal values. Due to the randomness of the heat injections, the resulting temperature profiles show thermal bumps that could be connected to intermittent behaviour in the transition region and the low corona.

Mendoza-Briceño, C. A.; Erdélyi, R.

2004-01-01

194

Optimum Design of Cantilevered Microprobes for Inspecting Lcd Panels and Measurement of Contacting Forces  

NASA Astrophysics Data System (ADS)

Fine pitch microprobe arrays are microneedle-like probes for inspecting the pixels of LCD panels or IC. They are usually made of multi-layers of metallic, nonmetallic, or combination of the two. The design requirement for a contacting force is less than 2 gf and a deflection should be less than 100 µm. Many microprobe shapes satisfying the design requirements are possible. A cantilever-type microprobe having many needles was chosen and optimized in this study. Several candidate shapes were chosen using topology and shape optimization technique subjected to design requirements. Then, the microprobe arrays were fabricated using the process applied for MEMS fabrication and they were made of BeNi, BeCu, or Si. The contact probing forces and deflections were measured for checking the results from optimum design by newly developed measuring equipment in our laboratory. Numerical and experimental results were compared and both showed a good correlation.

Kim, Cheol; Kim, Kwang-Joong

195

Optimum wavelengths for two color ranging  

NASA Astrophysics Data System (ADS)

The range uncertainties associated with the refractive atmosphere can be mitigated by the technique of two color, or dual wavelength, ranging. The precision of the differential time of flight (DTOF) measurement depends on the atmospheric dispersion between the two wavelengths, the received pulsewidths and photoelectron counts, and on the amount of temporal averaging. In general, the transmitted wavelengths are not independently chosen but instead are generated via nonlinear optics techniques (harmonic crystals, Raman scattering, etc.) which also determine their relative pulsewidths. The mean received photoelectrons at each wavelength are calculated via the familiar radar link equation which contains several wavelength dependent parameters. By collecting the various wavelength dependent terms, one can define a wavelength figure of merit for a two color laser ranging system. In this paper, we apply the wavelength figure of merit to the case of an extremely clear atmosphere and draw several conclusions regarding the relative merits of fundamental-second harmonic, fundamental-third harmonic, second-third harmonic, and Raman two color systems. We find that, in spite of the larger dispersion between wavelengths, fundamental-third harmonic systems have the lowest figure of merit due to a combination of poor detector performance at the fundamental and poor atmospheric transmission at the third harmonic. The fundamental-second harmonic systems (approximately 700 nm and 350 nm) have the highest figure of merit, but second-third harmonic systems, using fundamental transmitters near 1000 nm, are a close second. Raman-shifted transmitters appear to offer no advantage over harmonic systems because of the relatively small wavelength separation that can be achieved in light gases such as hydrogen and the lack of good ultrashort pulse transmitters with an optimum fundamental wavelength near 400 nm.

Degnan, John J.

1993-06-01

196

Parallelization Approaches for Hardware Accelerators - Loop Unrolling Versus Loop Partitioning  

Microsoft Academic Search

State-of-the-art behavioral synthesis tools barely have high-level transformations in order to achieve highly parallelized\\u000a implementations. If any, they apply loop unrolling to obtain a higher throughput. In this paper, we employ the PARO behavioral\\u000a synthesis tool which has the unique ability to perform both loop unrolling or loop partitioning. Loop unrolling replicates\\u000a the loop kernel and exposes the parallelism for

Frank Hannig; Hritam Dutta; Jürgen Teich

2009-01-01

197

N Reactor secondary loop contamination  

Microsoft Academic Search

N Reactor primary loop water circulates entirely within Zone 1 and the piping is, therefore, heavily shielded. Secondary loop piping crosses the Zone 1 boundaries into areas which may be unshielded and accessible during reactor operation. The leakage of primary loop water to the secondary side of the cooling loop permits contaminated fluid to leave the shielded area. It becomes

Stepnewski

1963-01-01

198

Preisach modeling of piezoceramic and shape memory alloy hysteresis  

Microsoft Academic Search

Smart materials such as piezoceramics, magnetostrictive materials, and shape memory alloys exhibit significant hysteresis, especially when driven with large input signals. Hysteresis can lead to unwanted harmonics, inaccuracy in open loop control, and instability in closed loop control. The Preisach independent domain hysteresis model has been shown to capture the major features of hysteresis arising in ferromagnetic materials. Noting the

Declan C. Hughes; John T. Wen

1996-01-01

199

Preisach modeling of piezoceramic and shape memory alloy hysteresis  

Microsoft Academic Search

Smart materials such as piezoceramics, magnetostrictive materials, and shape memory alloys exhibit hysteresis, and the larger the input signal the larger the effect. Hysteresis can lead to unwanted harmonics, inaccuracy in open loop control, and instability in closed loop control. The Preisach independent domain hysteresis model has been shown to capture the major features of hysteresis arising in ferromagnetic materials.

Declan Hughes; John T. Wen

1997-01-01

200

Optimum three-dimensional atmospheric entry from the analytical solution of Chapman's exact equations  

NASA Technical Reports Server (NTRS)

The general solution for the optimum three-dimensional aerodynamic control of a lifting vehicle entering a planetary atmosphere is developed. A set of dimensionless variables, modified Chapman variables, is introduced. The resulting exact equations of motion, referred to as Chapman's exact equations, have the advantage that they are completely free of the physical characteristics of the vehicle. Furthermore, a completely general lift-drag relationship is used in the derivation. The results obtained apply to any type of vehicle of arbitrary weight, dimensions and shape, having an arbitrary drag polar, and entering any planetary atmosphere. The aerodynamic controls chosen are the lift coefficient and the bank angle. General optimum control laws for these controls are developed. Several earlier particular solutions are shown to be special cases of this general result. Results are valid for both free and constrained terminal position.

Busemann, A.; Vinh, N. X.; Culp, R. D.

1974-01-01

201

TIG Welding and Shape Memory Effect of TiNi Shape Memory Alloy  

Microsoft Academic Search

In the present study, with respect to TIG welding for a TiNi shape-memory alloy wire and sheet, the optimum welding schedule was decided based on the breaking load of the weld and its standard deviation. By performing the cyclic loading-unloading and heating-cooling tests in the neighborhood of the weld, the shape memory effect was investigated. In order to investigate the

A. Ikai; K. Kimura; H. Tobushi

1996-01-01

202

Bifurcations of cuspidal loops  

NASA Astrophysics Data System (ADS)

A cuspidal loop 0951-7715/10/6/001/img5 for a planar vector field X consists of a homoclinic orbit 0951-7715/10/6/001/img6 through a singular point p, at which X has a nilpotent cusp. This is the simplest non-elementary singular cycle (or graphic) in the sense that its singularities are not elementary (i.e. hyperbolic or semihyperbolic). Cuspidal loops appear persistently in three-parameter families of planar vector fields. The bifurcation diagrams of unfoldings of cuspidal loops are studied here under mild genericity hypotheses: the singular point p is of Bogdanov - Takens type and the derivative of the first return map along the orbit 0951-7715/10/6/001/img6 is different from 1. An analytic and geometric method based on the blowing up for unfoldings is proposed here to justify the two essentially different models for generic bifurcation diagrams presented in this work. This method can be applied for the study of a large class of complex multiparametric bifurcation problems involving non-elementary singularities, of which the cuspidal loop is the simplest representative. The proofs are complete in a large part of parameter space and can be extended to the complete parameter space modulo a conjecture on the time function of certain quadratic planar vector fields. In one of the cases we can prove that the generic cuspidal loop bifurcates into four limit cycles that are close to it in the Hausdorff sense.

Dumortier, Freddy; Roussarie, Robert; Sotomayor, Jorge

1997-11-01

203

Closed-loop operation with alternative dewatering technology  

SciTech Connect

The introduction of dewatering devices for closed-loop drilling-fluid circulating systems and reserve pits is derived from technology that has been used in the industrial- and sanitary-waste treatment industries for years. This paper describes an overview of the need for closed-loop systems and provides the optimum design layout, including the fit of a dewatering device, for a drilling location. The introduction of a nonconventional dewatering device, called a screw press/thickener, is reviewed. A case history describing use of this technology in a southern Louisiana inland-marsh-area well is analyzed for the technical and economic viability of operating in a closed-loop mode. Results from this effort include a viable alternative to hauling off waste fluids from drilling sites and the realization that use of this technology can be justified economically.

Halliday, W.S.; Bray, R.P.; Youens, J.W.

1993-03-01

204

From Oligonucleotide Shapes to Genomic SELEX: Novel Biological Regulatory Loops  

Microsoft Academic Search

The SELEX method and oligonucleotide combinatorial chemistry discovery process yields high-affinity\\/high-specificity ligands for virtually any molecular target. Typically, the enormous starting libraries used in the SELEX process contain 1014-1015 sequences. We now ask if the smaller sequences, complexity of extant organisms, and evolutionary history provide useful interactions between oligonucleotides and at least some unexpected targets. That is, do organisms contain

Larry Gold; David Brown; Yi-Yuan He; Timur Shtatland; Britta S. Singer; Yan Wu

1997-01-01

205

Optimum academic performance and its relation to emotional intelligence  

Microsoft Academic Search

In Emotional Intelligence, Daniel Goleman (1995) discusses the effect of emotional competence on optimum performance. He describes the state of flow in which optimum performance occurs. Literature from coaching sports talks about this state of total concentration, as well. Our goal as teachers is to provide an atmosphere where flow occurs easily and the students are totally engaged in learning.

Richard Culver; Charles Yokomoto

1999-01-01

206

Optimum testing of multiple hypotheses in quantum detection theory  

Microsoft Academic Search

The problem of specifying the optimum quantum detector in multiple hypotheses testing is considered for application to optical communications. The quantum digital detection problem is formulated as a linear programming problem on an infinite-dimensional space. A necessary and sufficient condition is derived by the application of a general duality theorem specifying the optimum detector in terms of a set of

HORACE P. YUEN; ROBERT S. KENNEDY; MELVIN LAX

1975-01-01

207

Biological chip technology to quickly batch select optimum cryopreservation procedure  

Microsoft Academic Search

In the practices of cryobiology, selection of an optimum freeze\\/thawing program and an idealistic cryo- protective agent often requires rather tedious, time consum- ing and repetitive tests. Integrating the functions of sample preparation and viability detection, the concept of biochip technology was introduced to the field of cryopreservation, aiming at quickly finding an optimum freezing and thawing program. Prototype devices

YU Lina; LIU Jing; ZHOU Yixin; HUA Zezhao

208

Optimum design of B-series marine propellers  

Microsoft Academic Search

The choice of an optimum marine propeller is one of the most important problems in naval architecture. This problem can be handled using the propeller series diagrams or regression polynomials. This paper introduces a procedure to find out the optimum characteristics of B-series marine propellers. The propeller design process is performed as a single objective function subjected to constraints imposed

M. M. Gaafary; H. S. El-Kilani; M. M. Moustafa

2011-01-01

209

Permutations and the loop  

NASA Astrophysics Data System (ADS)

We consider the one-loop two-point function for multi-trace operators in the U(2) sector of Script N = 4 supersymmetric Yang-Mills at finite N. We derive an expression for it in terms of U(N) and Sn+1 group theory data, where n is the length of the operators. The Clebsch-Gordan operators constructed in [1], which are diagonal at tree level, only mix at one loop if you can reach the same (n+1)-box Young diagram by adding a single box to each of the n-box Young diagrams of their U(N) representations (which organise their multi-trace structure). Similar results are expected for higher loops and for other sectors of the global symmetry group.

Brown, T. W.

2008-06-01

210

Automatic one-loop calculations with Sherpa+OpenLoops  

NASA Astrophysics Data System (ADS)

We report on the OpenLoops generator for one-loop matrix elements and its application to four-lepton production in association with up to one jet. The open loops algorithm uses a numerical recursion to construct the numerator of one-loop Feynman diagrams as functions of the loop momentum. In combination with tensor integrals this results in a highly efficient and numerically stable matrix element generator. In order to obtain a fully automated setup for the simulation of next-to-leading order scattering processes we interfaced OpenLoops to the Sherpa Monte Carlo event generator.

Cascioli, F.; Höche, S.; Krauss, F.; Maierhöfer, P.; Pozzorini, S.; Siegert, F.

2014-06-01

211

The Anderson Current Loop  

NASA Technical Reports Server (NTRS)

Four-wire-probe concept applied to electrical-resistance transducers. Anderson current loop is excitation-and-signal-conditioning circuit suitable for use with strain gauges, resistance thermometers, and other electrical-resistance transducers mounted in harsh environments. Used as alternative to Wheatstone bridge. Simplifies signal-conditioning problem, enabling precise measurement of small changes in resistance of transducer. Eliminates some uncertainties in Wheatstone-bridge resistance-change measurements in flight research. Current loop configuration makes effects of lead-wire and contact resistances insignificantly small. Also provides output voltage that varies linearly with change in gauge resistance, and does so at double sensitivity of Wheatstone bridge.

Anderson, Karl F.

1994-01-01

212

Learning Active Shape Models for Bifurcating Contours  

Microsoft Academic Search

Statistical shape models are often learned from examples based on landmark correspondences between annotated examples. A method is proposed for learning such models from contours with inconsistent bifurcations and loops. Automatic segmentation of tibial and femoral contours in knee x-ray images is investigated as a step towards reliable, quantitative radio- graphic analysis of osteoarthritis for diagnosis and assessment of progression.

Matthias Seise; Stephen J. Mckenna; Ian W. Ricketts; Carlos A. Wigderowitz

2007-01-01

213

Gummy Shapes  

NSDL National Science Digital Library

In this activity, learners use chemistry to âself-assembleâ gummy shapes. Learners discover that self-assembly is a process by which molecules and cells form themselves into functional structures. Learners also learn that self-assembly is used to make nanocapsules that can deliver medication to diseased parts of the body, bypassing healthy parts. This activity is a fun way to talk about the connections between science and cooking, since the gummy capsules produced in this activity are also used in molecular gastronomy.

Sciencenter

2012-01-01

214

NETL - Chemical Looping Reactor  

ScienceCinema

NETL's Chemical Looping Reactor unit is a high-temperature integrated CLC process with extensive instrumentation to improve computational simulations. A non-reacting test unit is also used to study solids flow at ambient temperature. The CLR unit circulates approximately 1,000 pounds per hour at temperatures around 1,800 degrees Fahrenheit.

None

2014-06-26

215

Loop heat pipes  

Microsoft Academic Search

Loop heat pipes (LHPs) are two-phase heat-transfer devices with capillary pumping of a working fluid. They possess all the main advantages of conventional heat pipes, but owing to the original design and special properties of the capillary structure are capable of transferring heat efficiency for distances up to several meters at any orientation in the gravity field, or to several

Yu. F. Maydanik

2005-01-01

216

The Unsymmetrical Hysteresis Loop  

Microsoft Academic Search

The paper gives results and analyses of tests to determine losses in hysteresis loops wherein the magnetism is carried through cycles in which limiting values of flux are different in amount or the mean values of flux differ from zero. Such variations of magnetism occur in inductor generators, in teeth of induction machines and in materials magnetized from rectifier circuits,

John D. Ball

1915-01-01

217

Homogeneous loop quantum cosmology  

Microsoft Academic Search

Loop quantum cosmological methods are extended to homogeneous models in a diagonalized form. It is shown that the diagonalization leads to a simplification of the volume operator such that its spectrum can be determined explicitly. This allows the calculation of composite operators, most importantly the Hamiltonian constraint. As an application the dynamics of the Bianchi I model is studied and

Martin Bojowald

2003-01-01

218

Isotropic loop quantum cosmology  

Microsoft Academic Search

Isotropic models in loop quantum cosmology allow explicit calculations, thanks largely to a completely known volume spectrum, which is exploited in order to write down the evolution equation in a discrete internal time. Because of genuinely quantum geometrical effects, the classical singularity is absent in those models in the sense that the evolution does not break down there, contrary to

Martin Bojowald

2002-01-01

219

Consistent loop quantum cosmology  

Microsoft Academic Search

A consistent combination of quantum geometry effects rules out a large class of models of loop quantum cosmology and their critical densities as they have been used in the recent literature. In particular, the critical density at which an isotropic universe filled with a free, massless scalar field would bounce must be well below the Planck density. In the presence

Martin Bojowald

2009-01-01

220

Optimizing coherent anti-Stokes Raman scattering by genetic algorithm controlled pulse shaping  

NASA Astrophysics Data System (ADS)

The hybrid coherent anti-Stokes Raman scattering (CARS) has been successful applied to fast chemical sensitive detections. As the development of femto-second pulse shaping techniques, it is of great interest to find the optimum pulse shapes for CARS. The optimum pulse shapes should minimize the non-resonant four wave mixing (NRFWM) background and maximize the CARS signal. A genetic algorithm (GA) is developed to make a heuristic searching for optimized pulse shapes, which give the best signal the background ratio. The GA is shown to be able to rediscover the hybrid CARS scheme and find optimized pulse shapes for customized applications by itself.

Yang, Wenlong; Sokolov, Alexei

2010-10-01

221

Buck-boost switched-capacitor DC-DC voltage regulator using delta-sigma control loop  

Microsoft Academic Search

This paper presents a delta-sigma control loop for a buck-boost DC-DC converter with fractional gains. The charge pump used to convert the input voltage acts as a D\\/A converter in the loop, and its output ripple is frequency shaped by the loop, which also provides the pulse frequency modulation needed for the conversion. Simulation results show that the delta-sigma loop

A. Rao; W. Mcintyre; J. Parry; Un-ku Moon; Gabor C. Temes

2002-01-01

222

Collective Loop Fusion for Array Contraction  

Microsoft Academic Search

In this paper we propose a method for applying the loop fusion and array contractionoptimizations across a collection of loop nests. Loop fusion and array contraction aretechniques that can reduce array communication between fused loops by transformingarray references into simple scalar references. In previous work we investigated theproblem of performing loop interchange and loop reversal on individual loop nests soas

Guang R. Gao; R. Olsen; Vivek Sarkar; Radhika Thekkath

1992-01-01

223

Closed Loop Welding Controller for Manufacturing Process  

NASA Astrophysics Data System (ADS)

The aim of this paper is to investigate on the closed loop welding controller of a rapid manufacturing Shaped Metal Deposition (SMD) process. SMD was developed and patented by Rolls-Royce in order to produce mechanical parts directly from a CAD model. A simplified SMD plant has been set up in order to investigate the welding dynamics and parameters and to develop a SMD automatic controller. On the basis of the experience acquired, some basic control laws have been developed, and a closed loop controller has been implemented. This controller permits to find and to maintain the process stability condition, so that the final process results totally automatic. The control is performed adjusting the welding conditions on the basis of arc voltage information obtained from the welding machine during the deposition. The experimental results reported confirm the validity of the proposed strategy.

Bonaccorso, F.; Bruno, C.; Cantelli, L.; Longo, D.; Muscato, G.; Rapisarda, S.

2011-12-01

224

Null Zig-Zag Wilson Loops in {N}=4 Sym  

NASA Astrophysics Data System (ADS)

In planar {N}=4 supersymmetric Yang-Mills theory we have studied one kind of (locally) BPS Wilson loops composed of a large number of light-like segments, i.e. null zig-zags. These contours oscillate around smooth underlying spacelike paths. At one-loop in perturbation theory, we have compared the finite part of the expectation value of null zig-zags to the finite part of the expectation value of non-scalar-coupled Wilson loops whose contours are the underlying smooth spacelike paths. In arXiv:0710.1060 [hep-th] it was argued that these quantities are equal for the case of a rectangular Wilson loop. Here we present a modest extension of this result to zig-zags of circular shape and zig-zags following non-parallel, disconnected line segments and show analytically that the one-loop finite part is indeed that given by the smooth spacelike Wilson loop without coupling to scalars which the zig-zag contour approximates. We make some comments regarding the generalization to arbitrary shapes.

Xie, Zhifeng

225

Effect of Loop Geometry on TEM Response Over Layered Earth  

NASA Astrophysics Data System (ADS)

A large horizontal loop located on the ground or carried by an aircraft are the most common sources of the transient electromagnetic method. Although topographical factors or airplane outlines make the loop of arbitrary shape, magnetic sources are generally represented as a magnetic dipole or a circular loop, which may bring about significant errors in the calculated response. In this paper, we present a method for calculating the response of a loop of arbitrary shape (for which the description can be obtained by different methods, including GPS localization) in air or on the surface of a stratified earth. The principle of reciprocity is firstly used to exchange the functions of the transmitting loop and the dipole receiver, then the response of a vertical or a horizontal magnetic dipole is calculated beforehand, and finally the line integral of the second kind is employed to get the transient response. Analytical analysis and comparisons depict that our work got very good results in many situations. Synthetic and field examples are given in the end to show the effect of loop geometry and how our method improves the precision of the EM response.

Qi, Youzheng; Huang, Ling; Wu, Xin; Fang, Guangyou; Yu, Gang

2014-04-01

226

Three-Loop Static Potential  

SciTech Connect

We compute the three-loop corrections to the potential of two heavy quarks. In particular, we consider in this Letter the purely gluonic contribution which provides, in combination with our previous fermion corrections, the complete answer at three loops.

Smirnov, Alexander V. [Scientific Research Computing Center, Moscow State University, 119992 Moscow (Russian Federation); Smirnov, Vladimir A. [Skobeltsyn Institute of Nuclear Physics of Moscow State University, 119992 Moscow (Russian Federation); Steinhauser, Matthias [Institut fuer Theoretische Teilchenphysik, Karlsruhe Institute of Technology (KIT), D-76128 Karlsruhe (Germany)

2010-03-19

227

Flexible Loop Slip Ring Brush.  

National Technical Information Service (NTIS)

Flexible wire loop slip ring brushes for use in miniaturized gyroscopes. A plurality of flexible wire loop brushes hug or embrace opposite peripheral sides of respective slip rings in resilient sliding contact over a substantial arc for establishing a red...

J. B. Haberl

1980-01-01

228

Inner-Loop Flight Control  

Microsoft Academic Search

\\u000a We propose a three-layer automatic flight control system for our unmanned vehicles based on the time scales of the state variables\\u000a of the helicopter, which consists of the inner loop, the outer loop, and the flight scheduling layers. The inner loop stabilizes\\u000a the dynamics of the helicopter associated with its angular velocities and Euler angles. The outer loop controls the

Guowei Cai; Ben M. Chen; Tong Heng Lee

229

A closed loop welding controller for a rapid manufacturing process  

Microsoft Academic Search

The aim of this paper is to investigate on the closed loop welding controller of a rapid manufacturing shaped metal deposition (SMD) process. SMD was developed and patented by Rolls-Royce in order to produce mechanical parts directly from a CAD model. The paper describes a deep investigation upon the welding dynamics and parameters in order to develop an SMD automatic

Giovanni Muscato; Giacomo Spampinato; Luciano Cantelli

2008-01-01

230

Loop Heat Pipes and Capillary Pumped Loops: An Applications Perspective  

NASA Technical Reports Server (NTRS)

Capillary pumped loops (CPLS) and loop heat pipes (LHPS) are versatile two-phase heat transfer devices which have recently gained increasing acceptance in space applications. Both systems work based on the same principles and have very similar designs. Nevertheless, some differences exist in the construction of the evaporator and the hydro-accumulator, and these differences lead to very distinct operating characteristics for each loop. This paper presents comparisons of the two loops from an applications perspective, and addresses their impact on spacecraft design, integration, and test. Some technical challenges and issues for both loops are also addressed.

Butler, Dan; Ku, Jentung; Swanson, Theodore; Obenschain, Arthur F. (Technical Monitor)

2001-01-01

231

Numerical characterization of dynamic hysteresis loops and losses in soft magnetic materials  

Microsoft Academic Search

This paper deals with the characterization of dynamic loops shapes and losses in soft magnetic materials. An experimental and theoretical analysis has been done in order to describe static and dynamic hysteresis on soft ferrite cores. A parallelogram-loop-based hysteresis modeling is described and discussed. The possibility of the model to include vector hysteresis and the related properties are then discussed,

E. Cardeffi; Romano Giannetti; Bernardo Tellini

2005-01-01

232

Triangular hysteresis loops in the spin-rotation region of orthoferrites  

NASA Astrophysics Data System (ADS)

A theory is proposed that qualitatively explains the shapes of the hysteresis loops in orthoferrites within the temperature interval of the magnetic reorientation transition. Triangular loops result from the strong temperature dependence of both the magnetic moment and the magnetic domain wall structure.

Bazaliy, Ya. B.; Tsymbal, L. T.

2010-08-01

233

A Digital Loop Communication System  

Microsoft Academic Search

In this concise paper, we describe the concept of a local loop communication system with distributed control. Digital signals offered by the subscribers are parceled and transmitted in blocks to their destination using address-coding. Access of the terminals to the loop is gained by switching a delay network (shift register, containing the message block to be transmitted) into the loop

E. Hafner; Z. Nenadal; M. Tschanz

1974-01-01

234

Tracking performance of unbalanced QPSK demodulators. I - Biphase Costas loop with passive arm filters  

NASA Technical Reports Server (NTRS)

Unbalanced quadriphase-shift-keying (QPSK) is an attractive means for transmitting two digital data streams which in general have different average powers, data rates, and data formats. Previous analyses of the tracking performance of Costas loop demodulators of unbalanced QPSK have accounted only for the filtering effect produced by the loop's two arm filters on the equivalent additive noise perturbing the loop. When the bandwidth of these filters is selected on the basis of the order of the data rate, as is typical of optimum Costas loop design, the filtering degradations of the data modulations themselves and the cross-modulation noise produced by their multiplication in the loop often cannot be neglected. The purpose of this paper is to incorporate these additional filtering effects into the analysis. Many of the results obtained herein are in the form of closed-form expressions which can easily be evaluated numerically for design and performance prediction purposes.

Simon, M. K.; Alem, W. K.

1978-01-01

235

Optimum conditions for composites fiber coating by chemical vapor infiltration  

SciTech Connect

A combined analytical and numerical method is employed to optimize process conditions for composites fiber coating by chemical vapor infiltration (CVI). For a first-order deposition reaction, the optimum pressure yielding the maximum deposition rate at a preform center is obtained in closed form and is found to depend only on the activation energy of the deposition reaction, the characteristic pore size, and properties of the reactant and product gases. It does not depend on the preform specific surface area, effective diffusivity or preform thickness, nor on the gas-phase yield of the deposition reaction. Further, this optimum pressure is unaltered by the additional constraint of a prescribed deposition uniformity. Optimum temperatures are obtained using an analytical expression for the optimum value along with numerical solutions to the governing transport equations. These solutions account for both diffusive and advective transport, as well as both ordinary and Knudsen diffusion. Sample calculations are presented for coating preform fibers with boron nitride.

Griffiths, S.K.; Nilson, R.H.

1997-04-01

236

Optimum conditions for composites fiber coating by chemical vapor infiltration  

SciTech Connect

A combined analytical and numerical method is employed to optimize process conditions for composites fiber coating by chemical vapor infiltration. For a first-order deposition reaction, the optimum pressure yielding the maximum deposition rate at a preform center is obtained in closed form and is found to depend only on the activation energy of the deposition reaction, the characteristic pore size, and properties of the reactant and product gases. It does not depend on the preform specific surface area, effective diffusivity or preform thickness, nor on the gas-phase yield of the deposition reaction. Further, this optimum pressure is unaltered by the additional constraint of a prescribed deposition uniformity. Optimum temperatures are obtained using an analytical expression for the optimum value along with numerical solutions to the governing transport equations. These solutions account for both diffusive and advective transport, as well as both ordinary and Knudsen diffusion. Sample calculations are presented for coating preform fibers with boron nitride.

Griffiths, S.K.; Nilson, R.H. [Sandia National Labs., Livermore, CA (United States)

1998-04-01

237

Study of Optimum Pulse Transmission through a Dispersion Medium.  

National Technical Information Service (NTIS)

The propagation of electromagnetic signals through ionized media was studied with the goal of relating characteristics of transmitted signals to the physical properties of gaseous plasmas. In particular, methods of optimum transmission were considered usi...

R. E. McIntosh

1973-01-01

238

Research on the Wiener Canonical Expansion of Bayes' Optimum Filters.  

National Technical Information Service (NTIS)

This report contains the results of research on the Wiener Canonical Expansion of Bayes Optimum Filters. Investigation consisted of: (a) Application of the Wiener canonical expansion technique to various useful statistical decision, estimation, control an...

D. B. Bric E. G. Henrichon A. Citron R. W. Stout L. Petri

1968-01-01

239

A comparison of methods for DPLL loop filter design  

NASA Technical Reports Server (NTRS)

Four design methodologies for loop filters for a class of digital phase-locked loops (DPLLs) are presented. The first design maps an optimum analog filter into the digital domain; the second approach designs a filter that minimizes in discrete time weighted combination of the variance of the phase error due to noise and the sum square of the deterministic phase error component; the third method uses Kalman filter estimation theory to design a filter composed of a least squares fading memory estimator and a predictor. The last design relies on classical theory, including rules for the design of compensators. Linear analysis is used throughout the article to compare different designs, and includes stability, steady state performance and transient behavior of the loops. Design methodology is not critical when the loop update rate can be made high relative to loop bandwidth, as the performance approaches that of continuous time. For low update rates, however, the miminization method is significantly superior to the other methods.

Aguirre, S.; Hurd, W. J.; Kumar, R.; Statman, J.

1986-01-01

240

On Modeling Morphogenesis of the Looping Heart Following Mechanical Perturbations  

PubMed Central

Looping is a crucial early phase during heart development, as the initially straight heart tube (HT) deforms into a curved tube to lay out the basic plan of the mature heart. This paper focuses on the first phase of looping, called c-looping, when the HT bends ventrally and twists dextrally (rightward) to create a c-shaped tube. Previous research has shown that bending is an intrinsic process, while dextral torsion is likely caused by external forces acting on the heart. However, the specific mechanisms that drive and regulate looping are not yet completely understood. Here, we present new experimental data and finite element models to help define these mechanisms for the torsional component of c-looping. First, with regions of growth and contraction specified according to experiments on chick embryos, a three-dimensional model exhibits morphogenetic deformation consistent with observations for normal looping. Next, the model is tested further using experiments in which looping is perturbed by removing structures that exert forces on the heart — a membrane (splanchnopleure, SPL) that presses against the ventral surface of the heart and the left and right primitive atria. In all cases, the model predicts the correct qualitative behavior. Finally, a two-dimensional model of the HT cross section is used to study a feedback mechanism for stress-based regulation of looping. The model is tested using experiments in which the SPL is removed before, during, and after c-looping. In each simulation, the model predicts the correct response. Hence, these models provide new insight into the mechanical mechanisms that drive and regulate cardiac looping.

Ramasubramanian, Ashok; Nerurkar, Nandan L.; Achtien, Kate H.; Filas, Benjamin A.; Voronov, Dmitry A.; Taber, Larry A.

2008-01-01

241

Optimum Preventive Maintenance Policies for a 2Unit Redundant System  

Microsoft Academic Search

Optimum preventive maintenance policies are discussed to maximize the availability for a 2-unit standby redundant system. The Laplace-Stieltjes transform of the pointwise availability and the steady-state availability are derived by applying a unique modification of the regeneration point techniques under the assumptions that all the distributions are arbitrary. A theorem gives the optimum preventive maintenance time which is a unique

Toshio Nakagawa; Shunji Osaki

1974-01-01

242

Optimum Commodity Taxation with a NonRenewable Resource  

Microsoft Academic Search

Optimum commodity taxation theory asks how to raise a given amount of tax revenue while minimizing distortions. We reexamine Ramsey’s inverse elasticity rule in presence of Hotelling-type non-renewable natural resources. Under standard assumptions borrowed from the non-renewable-resource-extraction and from the optimum-commodity-taxation literatures, we show that a non-renewable resource should be taxed in priority whatever its demand elasticity and whatever the

Julien Daubanes; Pierre Lasserre

2011-01-01

243

Optimum Combining in Digital Mobile Radio with Cochannel Interference  

Microsoft Academic Search

This paper studies optimum signal combining for space diversity reception in cellular mobile radio systems. With optimum combining, the signals received by the antennas are weighted and combined to maximize the output signal-to-interference-plus-noise ratio. Thus, with cochannel interference, space diversity is used not only to combat Rayleigh fading of the desired signal (as with maximal ratio combining) but also to

JACK H. WINTERS

1984-01-01

244

Determining the Optimum Stratum Boundaries Using Mathematical Programming  

Microsoft Academic Search

The method of choosing the best boundaries that make strata internally homogeneous, given some sample allocation, is known\\u000a as optimum stratification. In order to make the strata internally homogeneous, the strata are constructed in such a way that\\u000a the strata variances should be as small as possible for the characteristic under study. In this paper the problem of determining\\u000a optimum

M. G. M. Khan; N. Ahmad; Sabiha Khan

2009-01-01

245

Capillary-pumped heat transport system two-phase loop and evaporators: Research and results  

Microsoft Academic Search

Different test performance and modeling results pertinent to capillary pumped heat transport systems are presented. The test results of an aluminum\\/ammonia two phase capillary pumped loop showed a heat transport capability between 250 W and 7.5 kW over a distance of 10 m. Emphasis is given to the loop in general and to the flat shaped evaporator performance. Cylindrical shaped

S. Vanoost; R. S. Bhatti; M. Dubois; G. Bekaert; W. Supper

1991-01-01

246

Channel shape optimization of electromagnetic pumps  

SciTech Connect

Electromagnetic pumps are used for the transportation of liquid metals such as the cooling sodium of fast breeder nuclear reactors. The design of this induction machine is close to that of a tubular linear induction motor. In this paper, channels of variable cross section are used to improve the efficiency of electromagnetic pumps. The optimum channel shape is derived analytically and is then tested with a finite element code. The performances are compared with those of standard pumps.

Leboucher, L.; Boissonneau, P. [LEGI, Genoble (France). Inst. de Mecanique de Grenoble] [LEGI, Genoble (France). Inst. de Mecanique de Grenoble; Villani, D. [Framatome direction Novatome, Lyon (France)] [Framatome direction Novatome, Lyon (France)

1995-05-01

247

Optimum detailed design of reinforced concrete frames using genetic algorithms  

NASA Astrophysics Data System (ADS)

This article presents the application of the genetic algorithm to the optimum detailed design of reinforced concrete frames based on Indian Standard specifications. The objective function is the total cost of the frame which includes the cost of concrete, formwork and reinforcing steel for individual members of the frame. In order for the optimum design to be directly constructible without any further modifications, aspects such as available standard reinforcement bar diameters, spacing requirements of reinforcing bars, modular sizes of members, architectural requirements on member sizes and other practical requirements in addition to relevant codal provisions are incorporated into the optimum design model. The produced optimum design satisfies the strength, serviceability, ductility, durability and other constraints related to good design and detailing practice. The detailing of reinforcements in the beam members is carried out as a sub-level optimization problem. This strategy helps to reduce the size of the optimization problem and saves computational time. The proposed method is demonstrated through several example problems and the optimum results obtained are compared with those in the available literature. It is concluded that the proposed optimum design model can be adopted in design offices as it yields rational, reliable, economical, time-saving and practical designs.

Govindaraj, V.; Ramasamy, J. V.

2007-06-01

248

Verification of Loop Diagnostics  

NASA Astrophysics Data System (ADS)

Many different techniques have been used to characterize the plasma in the solar corona: density-sensitive spectral line ratios are used to infer the density, the evolution of coronal structures in different passbands is used to infer the temperature evolution, and the simultaneous intensities measured in multiple passbands are used to determine the emission measure. All these analysis techniques assume that the intensity of the structures can be isolated through background subtraction. In this paper, we use simulated observations from a 3D hydrodynamic simulation of a coronal active region to verify these diagnostics. The density and temperature from the simulation are used to generate images in several passbands and spectral lines. We identify loop structures in the simulated images and calculate the loop background. We then determine the density, temperature and emission measure distribution as a function of time from the observations and compare with the true temperature and density of the loop. We find that the overall characteristics of the temperature, density, and emission measure are recovered by the analysis methods, but the details of the true temperature and density are not. For instance, the emission measure curves calculated from the simulated observations are much broader than the true emission measure distribution, though the average temperature evolution is similar. These differences are due, in part, to inadequate background subtraction, but also indicate a limitation of the analysis methods.

Winebarger, Amy R.; Lionello, Roberto; Mok, Yung; Linker, Jon A.; Mikic, Zoran

2014-06-01

249

Chemical Looping Combustion Kinetics  

SciTech Connect

One of the most promising methods of capturing CO{sub 2} emitted by coal-fired power plants for subsequent sequestration is chemical looping combustion (CLC). A powdered metal oxide such as NiO transfers oxygen directly to a fuel in a fuel reactor at high temperatures with no air present. Heat, water, and CO{sub 2} are released, and after H{sub 2}O condensation the CO{sub 2} (undiluted by N{sub 2}) is ready for sequestration, whereas the nickel metal is ready for reoxidation in the air reactor. In principle, these processes can be repeated endlessly with the original nickel metal/nickel oxide participating in a loop that admits fuel and rejects ash, heat, and water. Our project accumulated kinetic rate data at high temperatures and elevated pressures for the metal oxide reduction step and for the metal reoxidation step. These data will be used in computational modeling of CLC on the laboratory scale and presumably later on the plant scale. The oxygen carrier on which the research at Utah is focused is CuO/Cu{sub 2}O rather than nickel oxide because the copper system lends itself to use with solid fuels in an alternative to CLC called 'chemical looping with oxygen uncoupling' (CLOU).

Edward Eyring; Gabor Konya

2009-03-31

250

Cosmic string loop microlensing  

NASA Astrophysics Data System (ADS)

Cosmic superstring loops within the galaxy microlens background point sources lying close to the observer-string line of sight. For suitable alignments, multiple paths coexist and the (achromatic) flux enhancement is a factor of two. We explore this unique type of lensing by numerically solving for geodesics that extend from source to observer as they pass near an oscillating string. We characterize the duration of the flux doubling and the scale of the image splitting. We probe and confirm the existence of a variety of fundamental effects predicted from previous analyses of the static infinite straight string: the deficit angle, the Kaiser-Stebbins effect, and the scale of the impact parameter required to produce microlensing. Our quantitative results for dynamical loops vary by O(1) factors with respect to estimates based on infinite straight strings for a given impact parameter. A number of new features are identified in the computed microlensing solutions. Our results suggest that optical microlensing can offer a new and potentially powerful methodology for searches for superstring loop relics of the inflationary era.

Bloomfield, Jolyon K.; Chernoff, David F.

2014-06-01

251

Hot Holographic Giant Loop  

NASA Astrophysics Data System (ADS)

We consider the Polyakov loop operator in finite temperature planar N = 4 supersymmetric Yang-Mills theory defined on a spatial S3 and in representations where the number of boxes in the Young Tableau k is large and scales so that kN remains finite in the large N limit. We review the argument that, in the de-confined phase of the gauge theory, and for symmetric representations with row Young tableau, there is a quantum phase transition in the expectation value of the Polyakov loop operator which occurs as the size of the representation is increased beyond a critical value of kN. We also argue that for completely antisymmetric representations with column tableau, there is no such phase transition. The AdS/CFT dual of such large representation loops are thought to be probe D-branes with k units of fundamental string charge dissolved in their world-volumes. Our results for both symmetric and antisymmetric representations are consistent with what is known about these branes on the thermal AdS black hole background.

Grignani, G.; Karczmarek, J. L.; Semenoff, G. W.

2013-12-01

252

Integrable Wilson loops  

NASA Astrophysics Data System (ADS)

The generalized quark-antiquark potential of supersymmetric Yang-Mills theory on calculates the potential between a pair of heavy charged particles separated by an arbitrary angle on and also an angle in flavor space. It can be calculated by a Wilson loop following a prescribed path and couplings, or after a conformal transformation, by a cusped Wilson loop in flat space, hence also generalizing the usual concept of the cusp anomalous dimension. In this is calculated by an infinite open string. I present here an open spin-chain model which calculates the spectrum of excitations of such open strings. In the dual gauge theory these are cusped Wilson loops with extra operator insertions at the cusp. The boundaries of the spin-chain introduce a non-trivial reflection phase and break the bulk symmetry down to a single copy of . The dependence on the two angles is captured by the two embeddings of this algebra into , i.e., by a global rotation. The exact answer to this problem is conjectured to be given by solutions to a set of twisted boundary thermodynamic Bethe ansatz integral equations. In particular the generalized quark-antiquark potential or cusp anomalous dimension is recovered by calculating the ground state energy of the minimal length spin-chain, with no sites. It gets contributions only from virtual particles reflecting off the boundaries. I reproduce from this calculation some known weak coupling perturtbative results.

Drukker, Nadav

2013-10-01

253

Pulsed Neutron Intensity from Rectangular Shaped Light Water Moderator with Fast-Neutron Reflector  

Microsoft Academic Search

With a view to enhancing the thermal-neutron intensity obtained from a pulsed neutron source, an experimental study has been made to determine the optimum size of a rectangular shaped light water moderator provided with fast neutron reflector of beryllium oxide or graphite, and decoupled thermal-neutronically by means of Cd sheet. The optimum dimensions for the moderator are derived for the

Yoshiaki KIYANAGI; Hirokatsu IWASA

1982-01-01

254

The Role of Entropic Effects on DNA Loop Formation  

NASA Astrophysics Data System (ADS)

The formation of protein mediated DNA loops often regulates gene expression. Typically, a protein is simultaneously bound to two DNA operator sites. An example is the lactose repressor which binds to the Lac operon of E. coli. We characterize the mechanics of this system by calculating the free energy cost of loop formation. We construct a Hamiltonian that describes the change in DNA bending energy due to linear perturbations about the looped and open states, starting from a non-linear mechanical rod model that determines the shape and bending energy of the inter-operator DNA loop while capturing the intrinsic curvature and sequence-dependent elasticity of the DNA. The crystal structure of the LacI protein provides the boundary conditions for the DNA. We then calculate normal modes of the open and closed loops to account for the thermal fluctuations. The ratio of determinants of the two Hamiltonians yields the partition function, and the enthalphic and entropic cost of looping. This calculation goes beyond standard elastic energy models because it fully accounts for the substantial entropic differences between the two states. It also includes effects of sequence dependent curvature and stiffness and allows anisotropic variations in persistence length. From the free energy we then calculate the J-factor and ratio of loop lifetimes.

Wilson, David; Tkachenko, Alexei; Lillian, Todd; Perkins, Noel; Meiners, Jens Christian

2009-03-01

255

Efficiently computing exact geodesic loops within finite steps.  

PubMed

Closed geodesics, or geodesic loops, are crucial to the study of differential topology and differential geometry. Although the existence and properties of closed geodesics on smooth surfaces have been widely studied in mathematics community, relatively little progress has been made on how to compute them on polygonal surfaces. Most existing algorithms simply consider the mesh as a graph and so the resultant loops are restricted only on mesh edges, which are far from the actual geodesics. This paper is the first to prove the existence and uniqueness of geodesic loop restricted on a closed face sequence; it contributes also with an efficient algorithm to iteratively evolve an initial closed path on a given mesh into an exact geodesic loop within finite steps. Our proposed algorithm takes only an O(k) space complexity and an O(mk) time complexity (experimentally), where m is the number of vertices in the region bounded by the initial loop and the resultant geodesic loop, and k is the average number of edges in the edge sequences that the evolving loop passes through. In contrast to the existing geodesic curvature flow methods which compute an approximate geodesic loop within a predefined threshold, our method is exact and can apply directly to triangular meshes without needing to solve any differential equation with a numerical solver; it can run at interactive speed, e.g., in the order of milliseconds, for a mesh with around 50K vertices, and hence, significantly outperforms existing algorithms. Actually, our algorithm could run at interactive speed even for larger meshes. Besides the complexity of the input mesh, the geometric shape could also affect the number of evolving steps, i.e., the performance. We motivate our algorithm with an interactive shape segmentation example shown later in the paper. PMID:21690647

Xin, Shi-Qing; He, Ying; Fu, Chi-Wing

2012-06-01

256

Loops, Wrinkles and Scrolls in Twisted Ribbons  

NASA Astrophysics Data System (ADS)

We explore experimentally the stable and metastable configurations of an elastic ribbon under mixed twist and tension. A ribbon is a slender and thin elastic material with an extremely narrow cross section which exhibits features of rods and plates: it can coil and form loops but wrinkles and stress localization can also been seen yielding a surprisingly rich variety of shapes. Using the twist angle and the tension as control parameters, the various configurations obtained can be rationalized in a phase diagram. Using x-ray tomography, we are able to reconstruct the 3D shape of the ribbon which can then be precisely characterized by measuring locally the mean and Gaussian curvature. Guided by our experimental data, we will present a simple model for the bifurcations observed. Finally, implications for the fabrication of structured rods and yarns with novel mechanical and transport properties will be discussed.

Chopin, Julien; Kudrolli, Arshad

2013-03-01

257

SIGMOID-TO-FLUX-ROPE TRANSITION LEADING TO A LOOP-LIKE CORONAL MASS EJECTION  

SciTech Connect

Sigmoids are one of the most important precursor structures for solar eruptions. In this Letter, we study a sigmoid eruption on 2010 August 1 with EUV data obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO). In AIA 94 A (Fe XVIII; 6 MK), topological reconfiguration due to tether-cutting reconnection is unambiguously observed for the first time, i.e., two opposite J-shaped loops reconnect to form a continuous S-shaped loop, whose central portion is dipped and aligned along the magnetic polarity inversion line (PIL), and a compact loop crossing the PIL. A causal relationship between photospheric flows and coronal tether-cutting reconnections is evidenced by the detection of persistent converging flows toward the PIL using line-of-sight magnetograms obtained by the Helioseismic and Magnetic Imager on board SDO. The S-shaped loop remains in quasi-equilibrium in the lower corona for about 50 minutes, with the central dipped portion rising slowly at {approx}10 km s{sup -1}. The speed then increases to {approx}60 km s{sup -1} about 10 minutes prior to the onset of a GOES-class C3.2 flare, as the S-shaped loop speeds up its transformation into an arch-shaped loop, which eventually leads to a loop-like coronal mass ejection. The AIA observations combined with H{alpha} filtergrams as well as hard X-ray imaging and spectroscopy are consistent with most flare loops being formed by reconnection of the stretched legs of less-sheared J-shaped loops that envelopes the rising flux rope, in agreement with the standard tether-cutting scenario.

Liu Rui; Liu Chang; Wang Shuo; Deng Na; Wang Haimin, E-mail: rui.liu@njit.ed [Space Weather Research Laboratory, Center for Solar-Terrestrial Research, NJIT, Newark, NJ 07102 (United States)

2010-12-10

258

The Gulf Loop Current  

NSDL National Science Digital Library

Students conduct experiments and explore wind driven currents, determining patterns of current flow in a body of water. They participate in a relay where they blow a Styrofoam peanut or cotton ball across the classroom floor. They explore the motion of Styrofoam pieces that are floating in a clear pie pan of water simulating the Gulf Loop, and compare their pie pan model with a map of the currents. Students will map the trip of several different types of beach debris as it travels to the Texas coast.

Stryker, Pam

2010-01-01

259

Loop diagrams without ? matrices  

NASA Astrophysics Data System (ADS)

By using a quantum-mechanical path integral to compute matrix elements of the form , radiative corrections in quantum-field theory can be evaluated without encountering loop-momentum integrals. In this paper we demonstrate how Dirac ? matrices that occur in the proper-time ``Hamiltonian'' H lead to the introduction of a quantum-mechanical path integral corresponding to a superparticle analogous to one proposed recently by Fradkin and Gitman. Direct evaluation of this path integral circumvents many of the usual algebraic manipulations of ? matrices in the computation of quantum-field-theoretical Green's functions involving fermions.

McKeon, D. G. C.; Rebhan, A.

1993-09-01

260

Hard noncommutative loops resummation.  

PubMed

The noncommutative version of the Euclidean g2phi4 theory is considered. By using Wilsonian flow equations the ultraviolet renormalizability can be proved to all orders in perturbation theory. On the other hand, the infrared sector cannot be treated perturbatively and requires a resummation of the leading divergences in the two-point function. This is analogous to what is done in the hard thermal loops resummation of finite temperature field theory. Next-to-leading order corrections to the self-energy are computed, resulting in O(g3) contributions in the massless case, and O(g6logg2) in the massive one. PMID:11863880

Griguolo, Luca; Pietroni, Massimo

2002-02-18

261

Loop quantum black hole  

NASA Astrophysics Data System (ADS)

We study the quantum properties of the Kantowski Sachs spacetime, using ideas from loop quantum gravity. This spacetime coincides with the Schwarzschild black hole solution inside the horizon. Recently it was shown that the classical black hole singularity is controlled by the quantum theory, using ADM variables. In this paper we have used Ashtekar-like variables, obtaining information both on quantum effects on the singularity and on the dynamics across the r = 0 singular point. Finally, we have found a regular spacetime inside the horizon and that the dynamics can be extended beyond the classical singularity.

Modesto, Leonardo

2006-09-01

262

Closing the loop.  

PubMed

Closed-loop algorithms can be found in every aspect of everyday modern life. Automation and control are used constantly to provide safety and to improve quality of life. Closed-loop systems and algorithms can be found in home appliances, automobiles, aviation and more. Can one imagine nowadays driving a car without ABS, cruise control or even anti-sliding control? Similar principles of automation and control can be used in the management of diabetes mellitus (DM). The idea of an algorithmic/technological way to control glycaemia is not new and has been researched for more than four decades. However, recent improvements in both glucose-sensing technology and insulin delivery together with advanced control and systems engineering made this dream of an artificial pancreas possible. The artificial pancreas may be the next big step in the treatment of DM since the use of insulin analogues. An artificial pancreas can be described as internal or external devices that use continuous glucose measurements to automatically manage exogenous insulin delivery with or without other hormones in an attempt to restore glucose regulation in individuals with DM using a control algorithm. This device as described can be internal or external; can use different types of control algorithms with bi-hormonal or uni-hormonal design; and can utilise different ways to administer them. The different designs and implementations have transitioned recently from in silico simulations to clinical evaluation stage with practical applications in mind. This may mark the beginning of a new era in diabetes management with the introduction of semi-closed-loop systems that can prevent or minimise nocturnal hypoglycaemia, to hybrid systems that will manage blood glucose (BG) levels with minimal user intervention to finally fully automated systems that will take the user out of the loop. More and more clinical trials will be needed for the artificial pancreas to become a reality but initial encouraging results are proof that we are on the right track. We attempted to select recent publications that will present these current achievements in the quest for the artificial pancreas and that will inspire others to continue to progress this field of research. PMID:21323809

Dassau, E; Atlas, E; Phillip, M

2011-02-01

263

Optical parametric loop mirror  

NASA Astrophysics Data System (ADS)

A novel configuration for four-wave mixing (FWM) is proposed that offers the remarkable feature of inherently separating the FWM wave from the input pump and signal waves and suppressing their background amplified stimulated emission without optical filtering. In the proposed configuration, an optical parametric loop mirror, two counterpropagating FWM waves generated in a Sagnac interferometer interfere with a relative phase difference that is introduced deliberately. FWM frequency-conversion experiments in a polarization-maintaining fiber achieved more than 35 dB of input-wave suppression against the FWM wave.

Mori, K.; Morioka, T.; Saruwatari, M.

1995-06-01

264

Timing Recovery Loop Delay Compensation by Optimal Loop Gains  

Microsoft Academic Search

Future data storage systems must cope with higher densities and lower signal-to-noise ratios. Decision-aided timing recovery loops will likely need a longer delay in the sequence detector to make reliable bit decisions. Loop delay degrades the dynamics of the phase-locked loop (PLL). In this paper we present a process to determine optimal gains for PLL with delay assuming that the

Jin Xie; B. V. K. Vijaya Kumar

2006-01-01

265

Optimum Design of High-Speed Prop-Rotors.  

National Technical Information Service (NTIS)

An integrated multidisciplinary optimization procedure is developed for application to rotary wing aircraft design. The necessary disciplines such as dynamics, aerodynamics, aeroelasticity, and structures are coupled within a closed-loop optimization proc...

A. Chattopadhyay T. R. McCarthy

1993-01-01

266

Wilson loops as precursors  

NASA Astrophysics Data System (ADS)

There is substantial evidence that string theory on AdS5×S5 is a holographic theory in which the number of degrees of freedom scales as the area of the boundary in Planck units. Precisely how the theory can describe bulk physics using only surface degrees of freedom is not well understood. A particularly paradoxical situation involves an event deep in the interior of the bulk space. The event must be recorded in the (Schrödinger picture) state vector of the boundary theory long before a signal, such as a gravitational wave, can propagate from the event to the boundary. In a previous paper with Polchinski, we argued that the ``precursor'' operators which carry information stored in the wave during the time when it vanishes in a neighborhood of the boundary are necessarily non-local. In this paper we argue that the precursors cannot be products of local gauge invariant operators such as the energy momentum tensor. In fact gauge theories have a class of intrinsically non-local operators which cannot be built from local gauge invariant objects. These are the Wilson loops. We show that the precursors can be identified with Wilson loops whose spatial size is dictated by the UV-IR connection.

Susskind, Leonard; Toumbas, Nicolaos

2000-02-01

267

Accelerating the loop expansion  

SciTech Connect

This thesis introduces a new non-perturbative technique into quantum field theory. To illustrate the method, I analyze the much-studied phi/sup 4/ theory in two dimensions. As a prelude, I first show that the Hartree approximation is easy to obtain from the calculation of the one-loop effective potential by a simple modification of the propagator that does not affect the perturbative renormalization procedure. A further modification then susggests itself, which has the same nice property, and which automatically yields a convex effective potential. I then show that both of these modifications extend naturally to higher orders in the derivative expansion of the effective action and to higher orders in the loop-expansion. The net effect is to re-sum the perturbation series for the effective action as a systematic ''accelerated'' non-perturbative expansion. Each term in the accelerated expansion corresponds to an infinite number of terms in the original series. Each term can be computed explicitly, albeit numerically. Many numerical graphs of the various approximations to the first two terms in the derivative expansion are given. I discuss the reliability of the results and the problem of spontaneous symmetry-breaking, as well as some potential applications to more interesting field theories. 40 refs.

Ingermanson, R.

1986-07-29

268

Shapes and Geometry  

NSDL National Science Digital Library

Today we will learn more about shapes. We will also have a chance to create new shapes out of the shapes we receive! First, click on Sorting. Sort the different shapes by size, color, or shape. You will have to decide which way the shapes are being sorted each time. Sort shapes five times. Next, create some Quadrilaterals. This Quadrilateral can move as you click the vertex with the mouse and move it. ...

Holmgren, Ms.

2006-10-27

269

Optimum quantum dot size for highly efficient fluorescence bioimaging  

NASA Astrophysics Data System (ADS)

Semiconductor quantum dots of few nanometers have demonstrated a great potential for bioimaging. The size determines the emitted color, but it is also expected to play an important role in the image brightness. In this work, the size dependence of the fluorescence quantum yield of the highly thermal sensitive CdTe quantum dots has been systematically investigated by thermal lens spectroscopy. It has been found that an optimum quantum yield is reached for 3.8-nm quantum dots. The presence of this optimum size has been corroborated in both one-photon excited fluorescence experiments and two-photon fluorescence microscopy of dot-incubated cancer cells. Combination of quantum yield and fluorescence decay time measurements supports that the existence of this optimum size emerges from the interplay between the frequency-dependent radiative emission rate and the size-dependent coupling strength between bulk excitons and surface trapping states.

Martínez Maestro, Laura; Jacinto, Carlos; Rocha, Uéslen; Carmen Iglesias-de La Cruz, M.; Sanz-Rodriguez, Francisco; Juarranz, Angeles; García Solé, José; Jaque, Daniel

2012-01-01

270

Digital Parallel Processor Array for Optimum Path Planning  

NASA Technical Reports Server (NTRS)

The invention computes the optimum path across a terrain or topology represented by an array of parallel processor cells interconnected between neighboring cells by links extending along different directions to the neighboring cells. Such an array is preferably implemented as a high-speed integrated circuit. The computation of the optimum path is accomplished by, in each cell, receiving stimulus signals from neighboring cells along corresponding directions, determining and storing the identity of a direction along which the first stimulus signal is received, broadcasting a subsequent stimulus signal to the neighboring cells after a predetermined delay time, whereby stimulus signals propagate throughout the array from a starting one of the cells. After propagation of the stimulus signal throughout the array, a master processor traces back from a selected destination cell to the starting cell along an optimum path of the cells in accordance with the identity of the directions stored in each of the cells.

Kremeny, Sabrina E. (Inventor); Fossum, Eric R. (Inventor); Nixon, Robert H. (Inventor)

1996-01-01

271

Optimum two-impulse transfers for preliminary interplanetary trajectory design  

NASA Technical Reports Server (NTRS)

A method for numerically determining the optimum two-impulse transfer between two positions in two different heliocentric orbits is described. The formulas are based on earlier work by McCue and Bender (1965) for optimum two-impulse transfers between two orbits about the earth. The contours of minimum total Delta-V(Delta-V to launch plus Delta-V to achieve a given final orbit at the target body) are plotted on axes of true anomaly of the launch body at launch and true anomaly of the target body at arrival. The optimum transfers obtained are 'time-open' and the Delta-V from the initial orbit to the final orbit is found using patched conics. These 'prime rib' plots are useful for selecting initial conditions in the early phases of mission design.

Hulkower, N. D.; Lau, C. O.; Bender, D. F.

1984-01-01

272

Plasticity of 150-Loop in Influenza Neuraminidase Explored by Hamiltonian Replica Exchange Molecular Dynamics Simulations  

PubMed Central

Neuraminidase (NA) of influenza is a key target for antiviral inhibitors, and the 150-cavity in group-1 NA provides new insight in treating this disease. However, NA of 2009 pandemic influenza (09N1) was found lacking this cavity in a crystal structure. To address the issue of flexibility of the 150-loop, Hamiltonian replica exchange molecular dynamics simulations were performed on different groups of NAs. Free energy landscape calculated based on the volume of 150-cavity indicates that 09N1 prefers open forms of 150-loop. The turn A (residues 147–150) of the 150-loop is discovered as the most dynamical motif which induces the inter-conversion of this loop among different conformations. In the turn A, the backbone dynamic of residue 149 is highly related with the shape of 150-loop, thus can function as a marker for the conformation of 150-loop. As a contrast, the closed conformation of 150-loop is more energetically favorable in N2, one of group-2 NAs. The D147-H150 salt bridge is found having no correlation with the conformation of 150-loop. Instead the intimate salt bridge interaction between the 150 and 430 loops in N2 variant contributes the stabilizing factor for the closed form of 150-loop. The clustering analysis elaborates the structural plasticity of the loop. This enhanced sampling simulation provides more information in further structural-based drug discovery on influenza virus.

Han, Nanyu; Mu, Yuguang

2013-01-01

273

The double loop mattress suture.  

PubMed

An interrupted stitch type with favorable tissue characteristics will reduce local wound complications. We describe a novel high-strength, low-tension repair for the interrupted closure of skin, cartilage, and muscle, the double loop mattress stitch, and compare it experimentally with other interrupted closure methods. The performance of the double loop mattress technique in porcine cartilage and skeletal muscle is compared with the simple, mattress, and loop mattress interrupted sutures in both a novel porcine loading chamber and mechanical model. Wound apposition is assessed by electron microscopy. The performance of the double loop mattress in vivo was confirmed using a series of 805 pediatric laparotomies/laparoscopies. The double loop mattress suture is 3.5 times stronger than the loop mattress in muscle and 1.6 times stronger in cartilage (p???0.001). Additionally, the double loop mattress reduces tissue tension by 66% compared with just 53% for the loop mattress (p???0.001). Wound gapping is equal, and wound eversion appears significantly improved (p???0.001) compared with the loop mattress in vitro. In vivo, the double loop mattress performs as well as the loop mattress and significantly better than the mattress stitch in assessments of wound eversion and dehiscence. There were no episodes of stitch extrusion in our series of patients. The mechanical advantage of its intrinsic pulley arrangement gives the double loop mattress its favorable properties. Wound dehiscence is reduced because this stitch type is stronger and exerts less tension on the tissue than the mattress stitch. We advocate the use of this novel stitch wherever a high-strength, low-tension repair is required. These properties will enhance wound repair, and its application will be useful to surgeons of all disciplines. PMID:24698436

Biddlestone, John; Samuel, Madan; Creagh, Terry; Ahmad, Tariq

2014-05-01

274

Optimum camera placement considering camera specification for security monitoring  

Microsoft Academic Search

Abstract—We,present,an optimum,camera,placement,algo- rithm. We,are motivated,by,the fact that the installation of security cameras,is increasing rapidly. From the system cost point of view, it is desirable to observe all the area of interest by the smallest number,of cameras. We propose,a method,for deciding optimum,camera,placement,automatically,considering,camera specification such as visual distance, visual angle, and resolution. Moreover, to reduce the number of cameras, we divide the

Kenichi Yabuta; Hitoshi Kitazawa

2008-01-01

275

Shape and Reinforcement Optimization of Underground Tunnels  

NASA Astrophysics Data System (ADS)

Design of support system and selecting an optimum shape for the opening are two important steps in designing excavations in rock masses. Currently selecting the shape and support design are mainly based on designer's judgment and experience. Both of these problems can be viewed as material distribution problems where one needs to find the optimum distribution of a material in a domain. Topology optimization techniques have proved to be useful in solving these kinds of problems in structural design. Recently the application of topology optimization techniques in reinforcement design around underground excavations has been studied by some researchers. In this paper a three-phase material model will be introduced changing between normal rock, reinforced rock, and void. Using such a material model both problems of shape and reinforcement design can be solved together. A well-known topology optimization technique used in structural design is bi-directional evolutionary structural optimization (BESO). In this paper the BESO technique has been extended to simultaneously optimize the shape of the opening and the distribution of reinforcements. Validity and capability of the proposed approach have been investigated through some examples.

Ghabraie, Kazem; Xie, Yi Min; Huang, Xiaodong; Ren, Gang

276

Unstable anisotropic loop quantum cosmology  

SciTech Connect

We study stability conditions of the full Hamiltonian constraint equation describing the quantum dynamics of the diagonal Bianchi I model in the context of loop quantum cosmology. Our analysis has shown robust evidence of an instability in the explicit implementation of the difference equation, implying important consequences for the correspondence between the full loop quantum gravity theory and loop quantum cosmology. As a result, one may question the choice of the quantization approach, the model of lattice refinement, and/or the role of the ambiguity parameters; all these should, in principle, be dictated by the full loop quantum gravity theory.

Nelson, William; Sakellariadou, Mairi [Department of Physics, King's College London, Strand WC2R 2LS, London (United Kingdom)

2009-09-15

277

Dissipation of Longitudinal Oscillations in Stratified Nonisothermal Hot Coronal Loops  

NASA Astrophysics Data System (ADS)

We investigate the damping of longitudinal ( i.e., slow or acoustic) waves in nonisothermal, hot ( T? 5.0 MK), gravitationally stratified coronal loops. Motivated by SOHO/SUMER and Yohkoh/SXT observations, and by taking into account a range of dissipative mechanisms such as thermal conduction, compressive viscosity, radiative cooling, and heating, the nonlinear governing equations of one-dimensional hydrodynamics are solved numerically for standing-wave oscillations along a magnetic field line. A semicircular shape is chosen to represent the geometry of the coronal loop. It was found that the decay time of standing waves decreases with the increase of the initial temperature, and the periods of oscillations are affected by the different initial footpoint temperatures and loop lengths studied by the numerical experiments. In general, the period of oscillation of standing waves increases and the damping time decreases when the parameter that characterises the temperature at the apex of the loop increases for a fixed footpoint temperature and loop length. A relatively simple second-order scaling polynomial between the damping time and the parameter determining the apex temperature is found. This scaling relation is proposed to be tested observationally. Because of the lack of a larger, statistically relevant number of observational studies of the damping of longitudinal (slow) standing oscillations, it can only be concluded that the numerically predicted decay times are well within the range of values inferred from Doppler shifts observed by SUMER in hot coronal loops.

Erdélyi, R.; Luna-Cardozo, M.; Mendoza-Briceño, C. A.

2008-11-01

278

Studying DNA Looping by Single-Molecule FRET.  

PubMed

Bending of double-stranded DNA (dsDNA) is associated with many important biological processes such as DNA-protein recognition and DNA packaging into nucleosomes. Thermodynamics of dsDNA bending has been studied by a method called cyclization which relies on DNA ligase to covalently join short sticky ends of a dsDNA. However, ligation efficiency can be affected by many factors that are not related to dsDNA looping such as the DNA structure surrounding the joined sticky ends, and ligase can also affect the apparent looping rate through mechanisms such as nonspecific binding. Here, we show how to measure dsDNA looping kinetics without ligase by detecting transient DNA loop formation by FRET (Fluorescence Resonance Energy Transfer). dsDNA molecules are constructed using a simple PCR-based protocol with a FRET pair and a biotin linker. The looping probability density known as the J factor is extracted from the looping rate and the annealing rate between two disconnected sticky ends. By testing two dsDNAs with different intrinsic curvatures, we show that the J factor is sensitive to the intrinsic shape of the dsDNA. PMID:24998459

Le, Tung T; Kim, Harold D

2014-01-01

279

Colors and Shapes  

NSDL National Science Digital Library

How do you name things by color and shape? Lets learn about shapes and colors! 1. Watch this Color Video 2. Play this Color Game 3. Complete this Color Page 4. Watch this Shape Video 5. Watch this Shape Video2 6. Play this Shape Game 7. ...

Ms.campbell

2012-04-04

280

Dynamic PID loop control  

SciTech Connect

The Horizontal Test Stand (HTS) SRF Cavity and Cryomodule 1 (CM1) of eight 9-cell, 1.3GHz SRF cavities are operating at Fermilab. For the cryogenic control system, how to hold liquid level constant in the cryostat by regulation of its Joule-Thompson JT-valve is very important after cryostat cool down to 2.0 K. The 72-cell cryostat liquid level response generally takes a long time delay after regulating its JT-valve; therefore, typical PID control loop should result in some cryostat parameter oscillations. This paper presents a type of PID parameter self-optimal and Time-Delay control method used to reduce cryogenic system parameters oscillation.

Pei, L.; Klebaner, A.; Theilacker, J.; Soyars, W.; Martinez, A.; Bossert, R.; DeGraff, B.; Darve, C.; /Fermilab

2011-06-01

281

Vortex loops and Majoranas  

SciTech Connect

We investigate the role that vortex loops play in characterizing eigenstates of interacting Majoranas. We give some general results and then focus on ladder Hamiltonian examples as a test of further ideas. Two methods yield exact results: (i) A mapping of certain spin Hamiltonians to quartic interactions of Majoranas shows that the spectra of these two examples coincide. (ii) In cases with reflection-symmetric Hamiltonians, we use reflection positivity for Majoranas to characterize vortices in the ground states. Two additional methods suggest wider applicability of these results: (iii) Numerical evidence suggests similar behavior for certain systems without reflection symmetry. (iv) A perturbative analysis also suggests similar behavior without the assumption of reflection symmetry.

Chesi, Stefano [Department of Physics, McGill University, Montreal, Quebec H3A 2T8 (Canada) [Department of Physics, McGill University, Montreal, Quebec H3A 2T8 (Canada); CEMS, RIKEN, Wako, Saitama 351-0198 (Japan); Jaffe, Arthur [Harvard University, Cambridge, Massachusetts 02138 (United States) [Harvard University, Cambridge, Massachusetts 02138 (United States); Department of Physics, University of Basel, Basel (Switzerland); Institute for Theoretical Physics, ETH Zürich, Zürich (Switzerland); Loss, Daniel [CEMS, RIKEN, Wako, Saitama 351-0198 (Japan) [CEMS, RIKEN, Wako, Saitama 351-0198 (Japan); Department of Physics, University of Basel, Basel (Switzerland); Pedrocchi, Fabio L. [Department of Physics, University of Basel, Basel (Switzerland)] [Department of Physics, University of Basel, Basel (Switzerland)

2013-11-15

282

Digital self excited loop  

US Patent & Trademark Office Database

A process that provides the ability to incorporate a self exciting loop (SEL) algorithm into a digital LLRF system. The present digital SEL provides for conversion from the Cartesian domain to the Polar domain, wherein most signal processing is accomplished, and back to Cartesian. By handling most signal processing in the Polar (phase & amplitude) domain, a perfect amplitude limiter can be realized and simpler logic operations can be used. When operational, cavity recovery from faults will be tuner-less. At high gradients, .about.20 MV/m, like those needed for the upgraded cryomodules, the Lorentz detuning will be many bandwidths, making cavity turn-on problematic with out some tuner based compensation or other algorithmic solution. The present SEL solves this problem and allows cavity recovery from cryogenic trips, wherein cavities have been known to detune 1000's of Hz. Other applications such has He processing can also be implemented in situ without additional electronics.

2012-03-06

283

Aerodynamic shape optimization for unsteady three-dimensional flows  

Microsoft Academic Search

This paper presents an adjoint method for the optimum shape design of unsteady flows. The goal is to develop a set of discrete unsteady adjoint equations and the corresponding boundary condition for the non-linear frequency domain method. First, this paper presents the complete formulation of the time dependent optimal design problem. Second, we present the non-linear frequency domain adjoint equations

Siva K. Nadarajah; Matthew S. McMullen; Antony Jameson

2006-01-01

284

Uranyl Nitrate Flow Loop  

SciTech Connect

The objectives of the work discussed in this report were to: (1) develop a flow loop that would simulate the purified uranium-bearing aqueous stream exiting the solvent extraction process in a natural uranium conversion plant (NUCP); (2) develop a test plan that would simulate normal operation and disturbances that could be anticipated in an NUCP; (3) use the flow loop to test commercially available flowmeters for use as safeguards monitors; and (4) recommend a flowmeter for production-scale testing at an NUCP. There has been interest in safeguarding conversion plants because the intermediate products [uranium dioxide (UO{sub 2}), uranium tetrafluoride (UF{sub 4}), and uranium hexafluoride (UF{sub 6})] are all suitable uranium feedstocks for producing special nuclear materials. Furthermore, if safeguards are not applied virtually any nuclear weapons program can obtain these feedstocks without detection by the International Atomic Energy Agency (IAEA). Historically, IAEA had not implemented safeguards until the purified UF{sub 6} product was declared as feedstock for enrichment plants. H. A. Elayat et al. provide a basic definition of a safeguards system: 'The function of a safeguards system on a chemical conversion plant is in general terms to verify that no useful nuclear material is being diverted to use in a nuclear weapons program'. The IAEA now considers all highly purified uranium compounds as candidates for safeguarding. DOE is currently interested in 'developing instruments, tools, strategies, and methods that could be of use to the IAEA in the application of safeguards' for materials found in the front end of the nuclear fuel cycle-prior to the production of the uranium hexafluoride or oxides that have been the traditional starting point for IAEA safeguards. Several national laboratories, including Oak Ridge, Los Alamos, Lawrence Livermore, and Brookhaven, have been involved in developing tools or techniques for safeguarding conversion plants. This study was sponsored by the U.S. Department of Energy (DOE) NA-241, Office of Dismantlement and Transparency.

Ladd-Lively, Jennifer L [ORNL

2008-10-01

285

Biomass power cost and optimum plant size in western Canada  

Microsoft Academic Search

The power cost and optimum plant size for power plants using three biomass fuels in western Canada were determined. The three fuels are biomass from agricultural residues (grain straw), whole boreal forest, and forest harvest residues from existing lumber and pulp operations (limbs and tops). Forest harvest residues have the smallest economic size, 137 MW, and the highest power cost,

Amit Kumar; Jay B. Cameron; Peter C. Flynn

2003-01-01

286

Optimum digital recursive filters for step scan phased array radars  

Microsoft Academic Search

A design method for recursive filters with optimum clutter rejection is presented. The designed filters are suitable for MTI (moving target indication) systems in step scan phased array radars. The designed filters are optimized for a given clutter power spectrum and a finite number of samples without initialization. The performance of the designed filters was studied by considering their clutter

Hussian Al-Ahmad; Gordon B. Lockhart

1991-01-01

287

Optimum detection of slow frequency-hopped signals  

NASA Astrophysics Data System (ADS)

Optimum detectors have previously been derived for fast frequency-hopped (FFH) signals with M-ary frequency-shift-keyed (MFSK) data modulation received in additive white Gaussian noise. This paper extends that work to the more analytically complex category of slow frequency-hopped (SFH) signals with multiple MFSK tones per hop.

Levitt, Barry K.; Cheng, Unjeng; Polydoros, Andreas; Simon, Marvin K.

1994-02-01

288

The theory of optimum currency areas, trade adjustment, and trade  

Microsoft Academic Search

This article seeks to provide a closer integration of the theory of optimum currency areas with the theory of international trade. A currency area is treated as a continuous variable ranging from zero to one: zero if there is no enlargement, and some positive value otherwise, corresponding exactly to the percentge of trade in the enlarged area. The benefits of

Jacques Mélitz

1996-01-01

289

Optimum conditions for composites fiber coating by chemical vapor infiltration  

Microsoft Academic Search

A combined analytical and numerical method is employed to optimize process conditions for composites fiber coating by chemical vapor infiltration. For a first-order deposition reaction, the optimum pressure yielding the maximum deposition rate at a preform center is obtained in closed form and is found to depend only on the activation energy of the deposition reaction, the characteristic pore size,

Stewart K. Griffiths; R. H. Nilson

1998-01-01

290

The Optimum Brand Extension Strategy in Monopolized Target Market  

Microsoft Academic Search

Brand extension, or the use of established brand name to enter new product category, is a very popular branding strategy. According to the quality model reflecting the vertical differentiation of the product, this article derived the optimum brand extension strategy pattern of the brand-extension firm in the monopolized target market. The result showed: It is not always the positive correlation

Chai Jun-wu

2006-01-01

291

An Application of Calculus: Optimum Parabolic Path Problem  

ERIC Educational Resources Information Center

A practical and technological application of calculus problem is posed to motivate freshman students or junior high school students. A variable coefficient of friction is used in modelling air friction. The case in which the coefficient of friction is a decreasing function of altitude is considered. The optimum parabolic path for a flying object…

Atasever, Merve; Pakdemirli, Mehmet; Yurtsever, Hasan Ali

2009-01-01

292

Improved global sea surface temperature analyses using optimum interpolation  

Microsoft Academic Search

The new NOAA operational global sea surface temperature (SST) analysis is described. The analyses use 7 days of in situ (ship and buoy) and satellite SST. These analyses are produced weekly and daily using optimum interpolation (OI) on a 1[degrees] grid. The OI technique requires the specification of data and analysis error statistics. These statistics are derived and show that

Richard W. Reynolds; Thomas M. Smith

1994-01-01

293

A bilevel game theoretic approach to optimum design of flywheels  

Microsoft Academic Search

Multiobjective optimization problems arise frequently in mechanical design. One approach to solving these types of problems is to use a game theoretic formulation. This article illustrates the application of a bilevel, leader–follower model for solving an optimum design problem. In particular, the optimization problem is modelled as a Stackelberg game. The partitioning of variables between the leader and follower problem

Ehsan Ghotbi; Anoop K. Dhingra

2012-01-01

294

Optimum Onager: The Classical Mechanics of a Classical Siege Engine  

ERIC Educational Resources Information Center

The onager is a throwing weapon of classical antiquity, familiar to both the ancient Greeks and Romans. Here we analyze the dynamics of onager operation and derive the optimum angle for launching a projectile to its maximum range. There is plenty of scope for further considerations about increasing onager range, and so by thinking about how this…

Denny, Mark

2009-01-01

295

Design system for optimum contra-rotating propellers  

Microsoft Academic Search

A new type of contrarotating propeller (CRP) system has been developed through the cooperative research work of five shipbuilding companies in Japan (Hitachi Zosen Corporation; Kawasaki Heavy Industries, Ltd.; Mitsui Engineering and Shipbuilding Co., Ltd.; NKK Corporation; and Sumitomo Heavy Industries, Ltd.). This paper describes a design system for an optimum CRP, which is one of the numerous outcomes of

Noriyuki Sasaki; Mitsunori Murakami; Kazuo Nozawa; Shunji Soejima; Akira Shiraki; Takeshi Aono; Tomeo Fujimoto; Isao Funeno; Norio Ishii; Hiroshi Onogi

1998-01-01

296

Optimum cast plan for steelmaking-continuous casting production scheduling  

Microsoft Academic Search

A planning method of cast for steelmaking continuous casting production scheduling in CIMS is studied. The cast plan model is established. An adaptive operator genetic algorithm is proposed to solve the optimum cast plan problem. The computation with practical data shows that the model and the solving method are very effective.

Yuncan Xue; Qiwen Yang; Huihe Shao

2004-01-01

297

Optimum design and operation of a dynamic solar power system  

Microsoft Academic Search

The paper proposes a model of a space power station composed of a Curzon-Ahlborn engine driven by the heat flux supplied by a solar collector. Both design and operational optimizations are envisaged. Universal graphs are drawn for the optimum ratio between the collector and radiator area and for a non-dimensional maximum power. A brief comparison between the three usual types

V. Badescu

1996-01-01

298

Topology optimum design of loading plate in fuselage flutter model  

Microsoft Academic Search

Loading plate in fuselage flutter model is a thin-walled plate which is divided into regions with different thickness, so the design and manufacture is a difficult job. In this paper, topology optimum design of loading plate in fuselage flutter model for frequencies is presented. A thin-walled plate of variable thickness is converted to a constant thickness plate with holes. The

Yang Xuyin; Yang Rui; Wang Xianlin

2009-01-01

299

Selection of Wavelengths for Optimum Precision in Simultaneous Spectrophotometric Determinations.  

ERIC Educational Resources Information Center

Although many textbooks include a description of simultaneous determinations employing absorption spectrophotometry and treat the mathematics necessary for analytical quantitations, treatment of analytical wavelength selection has been mostly qualitative. Therefore, a general method for selecting wavelengths for optimum precision in simultaneous…

DiTusa, Michael R.; Schilt, Alfred A.

1985-01-01

300

The Optimum and Maximum Size of the University.  

ERIC Educational Resources Information Center

This document, which deals in whole with the optimum and maximum size of the university, is broken down into 4 major chapters, each of which was written by an expert in the particular field. The first discusses the unity of the university and studies: (1) the unity of the university, including in particular the relationship between the university…

Standing Conference of Rectors and Vice-Chancellors of the European Universities, Geneva (Switzerland).

301

Optimum control of multilevel inverters using Artificial Neural Networks  

Microsoft Academic Search

Estimation of optimum switching angles for multilevel converters so as to produce the required fundamental voltage while at the same time eliminate specified lower order harmonics through Artificial Neural Networks (ANNs) is presented. The proposed technique uses the best performance solutions (lowest THD solutions) as the training data set for proposed ANN system. This technique can be applied to multilevel

M. Tarafdar Hagh; H. Taghizadeh; K. Razi

2008-01-01

302

OPTIMUM CONTROL OF OSCILLATION OF WAVE-ENERGY CONVERTERS  

Microsoft Academic Search

The power output from wave energy converters (WECs) may be increased by controlling the oscillation in order to approach an optimum interaction between the WEC and the incident wave. Optimally controlled WECs, designed to operate at full capacity a rather large fraction of their lifetime, may improve the economic prospects for wave power significantly. Most of the WECs discussed here,

J. Falnes

1993-01-01

303

Optimum Sequential Detector Performance on Intersymbol Interference Channels.  

National Technical Information Service (NTIS)

Tight upper and lower bounds on the average probability of error are obtained for the nonlinear optimum sequential detector with zero 'look ahead'. A linear upper bound is obtained that is very tight over a wide range of signal-to-noise ratios and a wide ...

B. D. Fritchman L. N. Kanal J. D. Womer

1973-01-01

304

Optimum stuff threshold modulation schemes for digital data transmission  

Microsoft Academic Search

The method of `stuff threshold modulation' (STM) is widely used with pulse stuffing in network synchronizers to obtain reduced jitter power at the output of desynchronizers. Of the various STM waveforms that appear in the published literature, none have been selected as an optimum for a given set of synchronizer-desynchronizer operating conditions. This paper formulates the problem of STM waveform

Suman S. Abeysekera

1994-01-01

305

Optimum hot water temperature for absorption solar cooling  

Microsoft Academic Search

The hot water temperature that maximizes the overall instantaneous efficiency of a solar cooling facility is determined. A modified characteristic equation model is used and applied to single-effect lithium bromide–water absorption chillers. This model is based on the characteristic temperature difference and serves to empirically calculate the performance of real chillers. This paper provides an explicit equation for the optimum

A. Lecuona; R. Ventas; M. Venegas; A. Zacarías; R. Salgado

2009-01-01

306

Research on optimum location of urban land based on CA  

Microsoft Academic Search

The Optimum location of urban land is considered as an important issue of urban land intensive use. How to establish a technology road to realize this spatial location, objectively and quantitatively, has been the focus of current studies on urban land intensive use. During the summary of related studies at home and abroad, we try to establish the theory, methodology

Guoping Wu; Chonghui Song; Bo Wei; Qinshu Wu; Huichao Si

2007-01-01

307

Robust optimum criteria for tuned mass dampers in fuzzy environments  

Microsoft Academic Search

Tuned mass dampers are widely adopted passive strategies for vibrations mitigation, in the past years extensively investigated to improve the offered protection level in any mechanical systems in which they are installed. Although different mechanical and energetic optimum criteria have been proposed in the last decades by assuming involved parameters as deterministically known, nowadays the need persists to explore more

Giuseppe Carlo Marano; Giuseppe Quaranta

2009-01-01

308

Dispersion-managed solitons in a fiber loop with in-line filtering  

SciTech Connect

We investigate both numerically and experimentally soliton propagation in a fiber loop with dispersion management, in-line filters, and frequency shifting. More than 90{percent} of the fiber in the loop is in the normal-dispersion regime, but the net dispersion is anomalous. Stable pulses in the loop have an enhanced power relative to solitons in a fiber with uniform dispersion equal to the loop{close_quote}s path-averaged dispersion. Because the loop{close_quote}s path-averaged dispersion is small, the in-line filtering and the frequency shifting play an important role in pulse shaping. Recirculating loop experiments that demonstrate stable pulse propagation over 28,000 km are consistent with results from computer modeling. {copyright} {ital 1997} {ital Optical Society of America}

Golovchenko, E.A.; Jacob, J.M.; Pilipetskii, A.N.; Menyuk, C.R.; Carter, G.M. [Department of Computer Science and Electrical Engineering, University of Maryland, Baltimore County, Baltimore, Maryland 21250 (United States)

1997-03-01

309

Dispersion-managed solitons in a fiber loop with in-line filtering.  

PubMed

We investigate both numerically and experimentally soliton propagation in a fiber loop with dispersion management, in-line filters, and frequency shifting. More than 90% of the fiber in the loop is in the normal-dispersion regime, but the net dispersion is anomalous. Stable pulses in the loop have an enhanced power relative to solitons in a fiber with uniform dispersion equal to the loop's path-averaged dispersion. Because the loop's path-averaged dispersion is small, the in-line filtering and the frequency shifting play an important role in pulse shaping. Recirculating loop experiments that demonstrate stable pulse propagation over 28,000 km are consistent with results from computer modeling. PMID:18183178

Golovchenko, E A; Jacob, J M; Pilipetskii, A N; Menyuk, C R; Carter, G M

1997-03-01

310

Plasma shape experiments for an optimized tokamak  

NASA Astrophysics Data System (ADS)

In this paper we present results from recent experiments at DIII-D which measured the plasma stability and confinement performance product, beta(tau)(sub E), in one previously studied and three new plasma shapes. One important goal of these experiments was to identify performance vs. shape trends which would identify a shape compatible with both high performance and the planned effort to decrease the power flux to the divertor floor using a closed 'slot' divertor geometry. The closed divertor hardware must be designed for a reduced set of plasma shapes, so care must be taken to choose the shape that optimizes beta(tau)(sub E) and divertor performance. The four shapes studied form a matrix of moderate and high elongations (kappa congruent to 1.8 and 2.1) and low and high triangularities (delta congruent to 0.3 and 0.9). All configurations were double-null diverted (DND), held fixed during a shot, with neutral beam heating. The shapes span a range of X-point locations compatible with the envisioned closed divertor. We find that from shape to shape, a shot's transient normalized performance, beta(sub N)H, where beta(sub N) is equivalent to beta/(I(sup p)/aB(sub T)) and H is equivalent to tau(sub E)/tau(sub E)(sup ITER-89P), increases strongly with triangularity, but depends only weakly on elongation. However, the normalized performance during quasi stationary ELMing H-mode, to which these discharges eventually relax, is insensitive to both triangularity and elongation. The moderate elongation, high triangularity DND shape is shown to be near optimum for future studies on DIII-D.

Hyatt, A. W.; Osborne, T. H.; Lazarus, E. A.

1994-07-01

311

Loop quantum cosmology: I. Kinematics  

Microsoft Academic Search

The framework of quantum symmetry reduction is applied to loop quantum gravity with respect to transitively acting symmetry groups. This allows us to test loop quantum gravity in a large class of minisuperspaces and to investigate its features - e.g. the discrete volume spectrum - in certain cosmological regimes. Contrary to previous studies of quantum cosmology (minisuperspace quantizations) the symmetry

Martin Bojowald

2000-01-01

312

Sodium loop framework structural analysis  

SciTech Connect

This document provides the structural analysis of the Sodium Loop framework in a drop condition. The drop is similar to the US Department of Transportation non-bulk, performance-oriented packaging (Packaging Group I) drop test. The drop height evaluated for the Sodium Loop framework is 5.9 ft.

Nguyen, P.M.

1995-06-06

313

Fusion of Loops for Parallelism and Locality  

Microsoft Academic Search

Loop fusion improves data locality and re- duces synchronization in data-parallel applications. How - ever, loop fusion is not always legal. Even when legal, fusion may introduce loop-carried dependences which re- duce parallelism. In addition, performance losses result from cache conflicts in fused loops. We present new, sys- tematic techniques which: (1) allow fusion of loop nests in the presence

Naraig Manjikian; Tarek S. Abdelrahman

1995-01-01

314

Fusion of Loops for Parallelism and Locality  

Microsoft Academic Search

Abstract Loop fusion improves data locality and reduces synchronization in data-parallel applications. However, loop fusion is not always legal. Even when legal, fusion may introduce loop-carried dependences which prevent parallelism. In addition, performance losses result from cache conflicts in fused loops. In this paper, we present new techni ques to: (1) allow fusion of loop nests in the presence of

Naraig Manjikian; Tarek S. Abdelrahman

1997-01-01

315

Loop-bed combustion apparatus  

DOEpatents

The present invention is directed to a combustion apparatus in the configuration of a oblong annulus defining a closed loop. Particulate coal together with a sulfur sorbent such as sulfur or dolomite is introduced into the closed loop, ignited, and propelled at a high rate of speed around the loop. Flue gas is withdrawn from a location in the closed loop in close proximity to an area in the loop where centrifugal force imposed upon the larger particulate material maintains these particulates at a location spaced from the flue gas outlet. Only flue gas and smaller particulates resulting from the combustion and innerparticle grinding are discharged from the combustor. This structural arrangement provides increased combustion efficiency due to the essentially complete combustion of the coal particulates as well as increased sulfur absorption due to the innerparticle grinding of the sorbent which provides greater particle surface area.

Shang, Jer-Yu (Fairfax, VA); Mei, Joseph S. (Morgantown, WV); Slagle, Frank D. (Kingwood, WV); Notestein, John E. (Morgantown, WV)

1984-01-01

316

Loop Heat Pipe Startup Behaviors  

NASA Technical Reports Server (NTRS)

A loop heat pipe must start successfully before it can commence its service. The start-up transient represents one of the most complex phenomena in the loop heat pipe operation. This paper discusses various aspects of loop heat pipe start-up behaviors. Topics include the four start-up scenarios, the initial fluid distribution between the evaporator and reservoir that determines the start-up scenario, factors that affect the fluid distribution between the evaporator and reservoir, difficulties encountered during the low power start-up, and methods to enhance the start-up success. Also addressed are the thermodynamic constraint between the evaporator and reservoir in the loop heat pipe operation, the superheat requirement for nucleate boiling, pressure spike and pressure surge during the start-up transient, and repeated cycles of loop start-up andshutdown under certain conditions.

Ku, Jentung

2014-01-01

317

DNA looping and cleavage by restriction enzymes studied by manipulation of single DNA molecules with optical tweezers  

NASA Astrophysics Data System (ADS)

Looping and cleavage of single DNA molecules by the two-site restriction endonuclease Sau3AI were measured with optical tweezers. A DNA template containing many recognition sites was used, permitting loop sizes from ~10 to 10,000 basepairs. At high enzyme concentration cleavage events were detected within 5 seconds and nearly all molecules were cleaved within 5 minutes. Activity decreased ~10-fold as the DNA tension was increased from 0.03 to 0.7 pN. Substituting Ca2+ for Mg2+ blocked cleavage, permitting measurement of stable loops. At low tension, the initial rates of cleavage and looping were similar (~0.025 s-1 at 0.1 pN), suggesting that looping is rate limiting. Short loops formed more rapidly than long loops. The optimum size decreased from ~250 to 45 bp and the average number of loops (in 1 minute) from 4.2 to 0.75 as tension was increased from 0.03 to 0.7 pN. No looping was detected at 5 pN. These findings are in qualitative agreement with recent theoretical predictions considering only DNA mechanics, but we observed weaker suppression with tension and smaller loop sizes. Our results suggest that the span and elasticity of the protein complex and protein-induced DNA bending and wrapping play an important role.

Smith, Douglas E.; Gemmen, Gregory J.; Millin, Rachel

2006-09-01

318

ICRH antenna coupling physics and optimum plasma edge density profile. Application to ITER  

NASA Astrophysics Data System (ADS)

The performance of an ICRH system depends on the coupling capabilities of the antenna to the inhomogeneous plasma profile in front of it. The aim of this study is to understand the key physics phenomena contributing to the coupling. It is shown that the following plasma density profile characteristics are decisive: (i) distance between the antenna and the wave cutoff density, (ii) position of an optimum density with respect to the cutoff one and (iii) the density gradient leading from this optimum density to the plasma bulk. At each step of the analysis approximate relations are derived and the loading due to the plasma is compared with that of an isotropic dielectric medium in view of the application for modelling or dummy load testing. Examples are taken starting from the case of the projected ITER antenna array with its different phasing cases in front of the plasma edge profile used in the conceptual design phase. It is shown that, for the same antenna-cutoff distance, slight profile modifications can lead to substantial coupling and therefore power capability variations. Stronger profile modifications and some critically shaped resonant edge profiles are also analysed. The usefulness of a dielectric medium to simulate plasma loading is discussed in an appendix.

Messiaen, A.; Weynants, R.

2011-08-01

319

An optimum silica flour-bentonite mixture for an engineered barrier  

SciTech Connect

To dispose of low-level and mixed wastes (MAR) by burial, it is necessary to design an impermeable closure, which limits water infiltration through the waste. Bentonite has very low permeability to water but can be subject to volume alterations. Over time, these alterations can lead to channeling and subsequent permeability increases. The fluid conductivity and bulk properties of silica flour and bentonite mixtures were tested to find a mixture that would retain the low conductivity of the bentonite while maintaining volumetric stability. Silica flour was chosen for its small grain size and spherical shape, and its similarity to silty soil. Test results indicate that a 90% silica flour and 10% bentonite mixture will provide the optimum properties for this application. 5 refs., 2 figs., 2 tabs.

Walker, J.N.; Daffern, D.D.; Emer, D.F.

1991-01-01

320

A Numerical Model for the Search of the Optimum Capacitance in Electromagnetic Metal Forming  

NASA Astrophysics Data System (ADS)

Electromagnetic forming (EMF) is a high velocity forming technique that uses electromagnetic forces to shape metallic workpieces. In this work we present a numerical model that is able to compute the current flowing trough the coil, the Lorentz force acting on the workpiece and the optimum capacitance of the EMF process. The main advantage of our approach is that it provides an explicit relation between the capacitance of the capacitor bank and the frequency of the discharge, which is a key parameter in the design of an electromagnetic forming system. This method is computationally efficient because it only requires solving the time-harmonic Maxwell equations for a few frequencies to have completely characterized the EMF system. The approach can be very useful for estimating the order of magnitude of some parameters, for experimentation on modeling conditions, for coil design or for modeling complex geometries. Moreover, it can be easily included in a sequential coupling strategy without the worry of numerical instabilities.

Otin, Ruben; Mendez, Roger; Fruitos, Oscar

2011-08-01

321

Decision algorithm for 3D blood vessel loop based on a route edit distance  

NASA Astrophysics Data System (ADS)

This paper reports on a method to distinguish true from false of the loop in the blood vessel graph. Most conventional studies have used a graph to represent 3D blood vessels structure. Blood vessels graph sometimes has a false loop and this exerts a harmful influence to the graph analysis. Conventional study simply cut them but this is not suitable for the graph include real loop. For this reason, we try to distinguish true from false of the loop in the graph. Our method uses the loop inside and the outside main blood vessel shape to distinguish the similar loop. This main blood vessel we called route is long, thick, and not shares to other route as much as possible. Even if a graph includes false loop, this main route will avoid the false connection and detect the same main blood vessel. Our method detects such a main route in each loop branch point and stores it as the outside feature for comparing. Inside feature is measured by converting the inside blood vessels as one route. Each loop is compared by the graph edit distance. Graph edit distance is easily able to deal with the route adding, deleting and replacing. Our method was tested by the cerebral blood vessels image in MRI. Our method tried to detect the arterial cycles of Willis from the graph including false loops. As a result, our method detected it correctly in four data from five.

Kobayashi, D.; Yokota, H.; Morishita, S.; Hiraoka, K.; Fukasaku, K.; Himeno, R.; Mishima, T.

2009-02-01

322

Unimodular loop quantum cosmology  

NASA Astrophysics Data System (ADS)

Unimodular gravity is based on a modification of the usual Einstein-Hilbert action that allows one to recover general relativity with a dynamical cosmological constant. It also has the interesting property of providing, as the momentum conjugate to the cosmological constant, an emergent clock variable. In this paper we investigate the cosmological reduction of unimodular gravity, and its quantization within the framework of flat homogeneous and isotropic loop quantum cosmology. It is shown that the unimodular clock can be used to construct the physical state space, and that the fundamental features of the previous models featuring scalar field clocks are reproduced. In particular, the classical singularity is replaced by a quantum bounce, which takes place in the same condition as obtained previously. We also find that requirement of semiclassicality demands the expectation value of the cosmological constant to be small (in Planck units). The relation to spin foam models is also studied, and we show that the use of the unimodular time variable leads to a unique vertex expansion.

Chiou, Dah-Wei; Geiller, Marc

2010-09-01

323

Modeling loop entropy.  

PubMed

Proteins fold from a highly disordered state into a highly ordered one. Traditionally, the folding problem has been stated as one of predicting "the" tertiary structure from sequential information. However, new evidence suggests that the ensemble of unfolded forms may not be as disordered as once believed, and that the native form of many proteins may not be described by a single conformation, but rather an ensemble of its own. Quantifying the relative disorder in the folded and unfolded ensembles as an entropy difference may therefore shed light on the folding process. One issue that clouds discussions of "entropy" is that many different kinds of entropy can be defined: entropy associated with overall translational and rotational Brownian motion, configurational entropy, vibrational entropy, conformational entropy computed in internal or Cartesian coordinates (which can even be different from each other), conformational entropy computed on a lattice, each of the above with different solvation and solvent models, thermodynamic entropy measured experimentally, etc. The focus of this work is the conformational entropy of coil/loop regions in proteins. New mathematical modeling tools for the approximation of changes in conformational entropy during transition from unfolded to folded ensembles are introduced. In particular, models for computing lower and upper bounds on entropy for polymer models of polypeptide coils both with and without end constraints are presented. The methods reviewed here include kinematics (the mathematics of rigid-body motions), classical statistical mechanics, and information theory. PMID:21187223

Chirikjian, Gregory S

2011-01-01

324

Modeling Loop Entropy  

PubMed Central

Proteins fold from a highly disordered state into a highly ordered one. Traditionally, the folding problem has been stated as one of predicting ‘the’ tertiary structure from sequential information. However, new evidence suggests that the ensemble of unfolded forms may not be as disordered as once believed, and that the native form of many proteins may not be described by a single conformation, but rather an ensemble of its own. Quantifying the relative disorder in the folded and unfolded ensembles as an entropy difference may therefore shed light on the folding process. One issue that clouds discussions of ‘entropy’ is that many different kinds of entropy can be defined: entropy associated with overall translational and rotational Brownian motion, configurational entropy, vibrational entropy, conformational entropy computed in internal or Cartesian coordinates (which can even be different from each other), conformational entropy computed on a lattice; each of the above with different solvation and solvent models; thermodynamic entropy measured experimentally, etc. The focus of this work is the conformational entropy of coil/loop regions in proteins. New mathematical modeling tools for the approximation of changes in conformational entropy during transition from unfolded to folded ensembles are introduced. In particular, models for computing lower and upper bounds on entropy for polymer models of polypeptide coils both with and without end constraints are presented. The methods reviewed here include kinematics (the mathematics of rigid-body motions), classical statistical mechanics and information theory.

Chirikjian, Gregory S.

2011-01-01

325

Shapes and Shaping of Planetary Nebulae  

Microsoft Academic Search

We review the state of observational and theoretical studies of the shaping of planetary nebulae (PNe) and protoplanetary nebulae (pPNe). In the past decade, high-resolution studies of PNe have revealed a bewildering array of morphologies with elaborate symmetries. Recent imaging studies of pPNe exhibit an even richer array of shapes. The variety of shapes, sometimes multiaxial symmetries, carefully arranged systems

Bruce Balick; Adam Frank

2002-01-01

326

Rogowski Loop design for NSTX  

SciTech Connect

The Rogowski Loop is one of the most basic diagnostics for tokamak operations. On the National Spherical Torus Experiment (NSTX), the plasma current Rogowski Loop had the constraints of the very limited space available on the center stack, 5,000 volt isolation, flexibility requirements as it remained a part of the Center Stack assembly after the first phase of operation, and a +120 C temperature requirement. For the second phase of operation, four Halo Current Rogowski Loops under the Center Stack tiles will be installed having +600 C and limited space requirements. Also as part of the second operational phase, up to ten Rogowski Loops will installed to measure eddy currents in the Passive Plate support structures with +350 C, restricted space, and flexibility requirements. This presentation will provide the details of the material selection, fabrication techniques, testing, and installation results of the Rogowski Loops that were fabricated for the high temperature operational and bakeout requirements, high voltage isolation requirements, and the space and flexibility requirements imposed upon the Rogowski Loops. In the future operational phases of NSTX, additional Rogowski Loops could be anticipated that will measure toroidal plasma currents in the vacuum vessel and in the Passive Plate assemblies.

McCormack, B.; Kaita, R.; Kugel, H.; Hatcher, R.

2000-01-06

327

Wilson loops in minimal surfaces  

SciTech Connect

The AdS/CFT correspondence suggests that the Wilson loop of the large N gauge theory with N = 4 supersymmetry in 4 dimensions is described by a minimal surface in AdS{sub 5} x S{sup 5}. The authors examine various aspects of this proposal, comparing gauge theory expectations with computations of minimal surfaces. There is a distinguished class of loops, which the authors call BPS loops, whose expectation values are free from ultra-violet divergence. They formulate the loop equation for such loops. To the extent that they have checked, the minimal surface in AdS{sub 5} x S{sup 5} gives a solution of the equation. The authors also discuss the zig-zag symmetry of the loop operator. In the N = 4 gauge theory, they expect the zig-zag symmetry to hold when the loop does not couple the scalar fields in the supermultiplet. They will show how this is realized for the minimal surface.

Drukker, Nadav; Gross, David J.; Ooguri, Hirosi

1999-04-27

328

Shape & Solid Exploration  

NSDL National Science Digital Library

In this game, learners use clues to identify mystery shapes. Use everyday objects (like from the pantry) as the shapes. It is important for learners to be able to describe a shape with correct math vocabulary and to be able to visualize a shape in their head.

Houston, Children'S M.

2011-01-01

329

Dynamic Shapes Average.  

National Technical Information Service (NTIS)

A framework for computing shape statistics in general, and average in particular, for dynamic shapes is introduced in this paper. Given a metric d(-,-) on the set of static shapes, the empirical mean of N static shapes, C(sub 1),...,C(sub N), is defined b...

P. Maurel G. Sapiro

2005-01-01

330

Physical Meaning of the Optimum Measurement Process in Quantum Detection Theory  

NASA Technical Reports Server (NTRS)

The optimum measurement processes are represented as the optimum detection operators in the quantum detection theory. The error probability by the optimum detection operators goes beyond the standard quantum limit automatically. However the optimum detection operators are given by pure mathematical descriptions. In order to realize a communication system overcoming the standard quantum limit, we try to give the physical meaning of the optimum detection operators.

Osaki, Masao; Kozuka, Haruhisa; Hirota, Osamu

1996-01-01

331

Optimum detection of an optical image on a photoelectric surface.  

NASA Technical Reports Server (NTRS)

The image-detecting performance of an optimum counting detector is compared with that of a threshold detector and that of a detector basing its decisions on the total number of photoelectrons from a finite area of the image. The illuminance of the image is assumed to have a Gaussian spatial distribution. The optimum detector works with the pristine datum (and not with the photoelectric response) which is the spatiotemporal electromagnetic field at the aperture of the observing optical instrument. It is shown that little is to be gained by using details of the illuminance distribution beyond the crude knowledge of its breadth as embodied in a simple counter of emitted photoelectrons. All three detectors exhibit accordingly about the same reliability.

Helstrom, C. W.; Wang, L.

1973-01-01

332

Asymptotically optimum radar detection in compound-Gaussian clutter  

NASA Astrophysics Data System (ADS)

An asymptotically optimum receiver designed for detecting coherent pulse trains in compound-Gaussian clutter is introduced and assessed. The proposed receiver assumes knowledge of the structure of the clutter covariance matrix, but does not require that of its amplitude probability density function (apdf). Performance is analytically evaluated, showing that the loss, as measured with respect to the corresponding optimum structure, is kept within a few dBs even for a relatively small number of integrated pulses and that it largely outperforms the matched-filter detector under all instances of practical interest. Interestingly, the proposed detector achieves constant false alarm rate (CFAR), regardless of the clutter envelope distribution and, consequently, its power.

Conte, Ernesto; Lops, Marco; Ricci, Giuseppe

1995-04-01

333

A methodology for selecting optimum organizations for space communities  

NASA Technical Reports Server (NTRS)

This paper suggests that a methodology exists for selecting optimum organizations for future space communities of various sizes and purposes. Results of an exploratory study to identify an optimum hypothetical organizational structure for a large earth-orbiting multidisciplinary research and applications (R&A) Space Base manned by a mixed crew of technologists are presented. Since such a facility does not presently exist, in situ empirical testing was not possible. Study activity was, therefore, concerned with the identification of a desired organizational structural model rather than the empirical testing of it. The principal finding of this research was that a four-level project type 'total matrix' model will optimize the effectiveness of Space Base technologists. An overall conclusion which can be reached from the research is that application of this methodology, or portions of it, may provide planning insights for the formal organizations which will be needed during the Space Industrialization Age.

Ragusa, J. M.

1978-01-01

334

A new optimum topology switching dc-to-dc converter  

NASA Technical Reports Server (NTRS)

A novel switching dc-to-dc converter is presented, which has the same general conversion property (increase or decrease of the input dc voltage) as does the conventional buck-boost converter, and which offers through its new optimum topology higher efficiency, lower output voltage ripple, reduced EMI, smaller size and weight, and excellent dynamic response. One of its most significant advantages is that both input and output current are not pulsating but are continuous (essentially dc with small superimposed switching current ripple), thus resulting in a close approximation to the ideal physically nonrealizable dc-to-dc transformer. The converter retains the simplest possible structure with the minimum number of components which, when interconnected in its optimum topology, yield the maximum performance.

Cuk, S.; Middlebrook, R. D.

1977-01-01

335

Optimum Production Control and Workforce Scheduling of Machining Project  

NASA Astrophysics Data System (ADS)

Through the proposed model in this study, the production control with the consideration of workforce scheduling for advanced manufacturing systems becomes realistically and concretely solvable. This study not only meditates the concept of balancing machine productivity and human ability into the objective, but also implements Calculus of Variations to optimize the profit for a deterministic production quantity. In addition, the optimum solutions of dynamic productivity control and workforce scheduling are comprehensively provided. Moreover, the decision criteria for selecting the optimum solution and the sensitivity analysis of the critical variables are fully discussed. This study definitely contributes the applicable strategy to control the productivity and workforce in manufacturing and provides the valuable tool to conclusively optimize the profit of a machining project for operations research in today`s manufacturing industry with profound insight.

Lan, Tian-Syung; Lo, Chih-Yao; Hou, Cheng-I.

336

Shape control of a beam using piezoelectric actuators  

NASA Astrophysics Data System (ADS)

This paper presents the analytical and experimental results on optimal placement of piezoceramic actuators for shape control of beam structures. The objective is to determine the optimum piezoceramic actuator locations and voltages to minimize the error between the desired shape and the achieved shape. The analytical model for predicting beam deformation due to a piezoelectric actuator is based on the Euler-Bernoulli model. The cost function has fifth-order polynomials in the actuator locations and second-order polynomials in actuator voltages. This difference resulted in difficulty in simultaneous optimization of actuator locations and voltages. Using embedded Nader and Mead simplex algorithms to separately optimize actuator locations and voltages was found to produce reliable results, converging to the same optimum solution for a variety of initial conditions. Experimental results show that the analytical model provides a reasonable prediction of actuator performance at low input voltage, but does not account for the nonlinear behavior of the piezoceramic and effects of hysteresis.

Agrawal, Brij N.; Treanor, Kirk E.

1999-12-01

337

Comparison of High Damping Shape Memory Alloys with Cu-Mn-Based and Fe-Cr-Based Alloys.  

National Technical Information Service (NTIS)

The strain dependence and temperature dependence of damping in the thermoelastic martensitic (shape memory) alloys titanium-nickel and copper zinc aluminum was compared to predetermined optimum damping behavior in the quiet alloys copper manganese aluminu...

J. T. Cronauer

1987-01-01

338

A noise–shaped switched–capacitor DC–DC voltage regulator  

Microsoft Academic Search

This paper presents a delta-sigma control loop for a buck-boost dc-dc converter with fractional gains. The charge pump used to convert the input voltage acts as a D\\/A converter in the loop, and its output ripple is frequency shaped by the loop, which also provides the pulse-frequency modulation needed for the conversion. A test chip realised in a 0.72-µm CMOS

A. Rao; W. McIntyre; U. Moon; G. Temes

2002-01-01

339

Easily Computable Optimum Grasps in 2-D and 3-D  

Microsoft Academic Search

We consider the problem of finding optimum forceclosure grasps of two and three-dimensional objects.Our focus is on grasps which are useful in practice,namely grasps with a small number of fingers, withfriction at the contacts. Assuming frictional contactand rounded finger tips---very mild assumptions inpractice---we give new upper (and lower) bounds onthe number of fingers necessary to achieve force closuregrasps of 2-D

Brian Mirtich; John F. Canny

1994-01-01

340

Optimum Design of Steel Frames via Harmony Search Algorithm  

Microsoft Academic Search

A harmony search algorithm is presented for optimum design of planar and space steel frames in this chapter. Harmony search\\u000a (HS) is a meta-heuristic search method. It bases on the analogy between natural musical performance process and searching\\u000a the solutions to optimization problems. The design algorithm aims to obtain minimum weight frames by selecting a standard\\u000a set of steel sections.

S. O. Degertekin

341

Sand deserts during glacial maximum and climatic optimum  

Microsoft Academic Search

THE past 20,000 yr have witnessed tremendous climatic changes, a glacial maximum at about 18,000 yr BP and a climatic optimum centred on about 6,000 yr BP, both of which mark extreme situations for the Quaternary. This paper attempts to show that active sand dunes were extensive 18,000 yr ago. Conversely, it seems that sand dunes were generally dormant 6,000

Michael Sarnthein

1978-01-01

342

Safety Systems Optimum Design by Multicriteria Evolutionary Algorithms  

Microsoft Academic Search

In this work new safety systems multiobjective optimum design methodologies are introduced and compared. Various multicriteria\\u000a evolutionary algorithms are analysed (SPEA2, NSGAII and controlled elitist-NSGAII) and applied to a Containment Spray Injection\\u000a System of a nuclear power plant. Influence of various mutation rates is considered. A double minimization is handled: unavailability\\u000a and cost of the system. The comparative statistical results

David Greiner; Blas Galván; Gabriel Winter

2003-01-01

343

Optimum sensitivity derivatives of objective functions in nonlinear programming  

NASA Technical Reports Server (NTRS)

The feasibility of eliminating second derivatives from the input of optimum sensitivity analyses of optimization problems is demonstrated. This elimination restricts the sensitivity analysis to the first-order sensitivity derivatives of the objective function. It is also shown that when a complete first-order sensitivity analysis is performed, second-order sensitivity derivatives of the objective function are available at little additional cost. An expression is derived whose application to linear programming is presented.

Barthelemy, J.-F. M.; Sobieszczanski-Sobieski, J.

1983-01-01

344

Optimum management of pediatric patients with fever and neutropenia  

Microsoft Academic Search

Fever with neutropenia is a common clinical problem in patients receiving cancer treatment. Prevention and optimum management\\u000a of infectious complications is critical to the overall success of cancer therapy. This article provides an overview of the\\u000a current status of this evolving subject. While the basic principles of rapid institution of broad spectrum antibiotics, early\\u000a intervention with empiric antifungal therapy and

Aditya H. Gaur; Patricia M. Flynn; Jerry L. Shenepu

2004-01-01

345

Optimum take-off angle in the standing long jump  

Microsoft Academic Search

The aim of this study was to identify and explain the optimum projection angle that maximises the distance achieved in a standing long jump. Five physically active males performed maximum-effort jumps over a wide range of take-off angles, and the jumps were recorded and analysed using a 2-D video analysis procedure. The total jump distance achieved was considered as the

Masaki Wakai; Nicholas P. Linthorne

2005-01-01

346

Optimum control strategy for all-variable speed chiller plant  

Microsoft Academic Search

The optimum control strategy and the saving potential of all variable chiller plant under the conditions of changing building\\u000a cooling load and cooling water supply temperature were investigated. Based on a simulation model of water source chiller plant\\u000a established in dynamic transient simulation program (TRNSYS), the four-variable quadratic orthogonal regression experiments\\u000a were carried out by taking cooling load, cooling water

Xiao-qiang Jiang; Wei-ding Long; Min Li

2011-01-01

347

Generalized chirp-like polyphase sequences with optimum correlation properties  

Microsoft Academic Search

A new general class of polyphase sequences with ideal periodic autocorrelation function is presented. The new class of sequences is based on the application of Zadoff-Chu polyphase sequences of length N=sm2, where s and m are any positive integers. It is shown that the generalized chirp-like sequences of odd length have the optimum crosscorrelation function under certain conditions. Finally, recently

Branislav M. Popovic

1992-01-01

348

Optimum detection of slow frequency-hopped signals  

Microsoft Academic Search

Optimum detectors have previously been derived for fast frequency-hopped (FFH) signals with M-ary frequency-shift-keyed (MFSK) data modulation received in additive white Gaussian noise (FFH here implies that a single MFSK tone is transmitted per hop), The present paper extends that work to the more analytically complex category of slow frequency-hopped (SFH) signals with multiple MFSK tones per hop. A special

Barry K. Levitt; Unjeng Cheng; Andreas Polydoros; Marvin K. Simon

1994-01-01

349

Optimum design of steel frames using harmony search algorithm  

Microsoft Academic Search

In this article, harmony search algorithm was developed for optimum design of steel frames. Harmony search is a meta-heuristic\\u000a search method that has been developed recently. It bases on the analogy between the performance process of natural music and\\u000a searching for solutions to optimization problems. The objective of the design algorithm is to obtain minimum weight frames\\u000a by selecting suitable

S. O. Degertekin

2008-01-01

350

Near-optimum decoding of product codes: block turbo codes  

Microsoft Academic Search

This paper describes an iterative decoding algorithm for any product code built using linear block codes. It is based on soft-input\\/soft-output decoders for decoding the component codes so that near-optimum performance is obtained at each iteration. This soft-input\\/soft-output decoder is a Chase decoder which delivers soft outputs instead of binary decisions. The soft output of the decoder is an estimation

Ramesh Mahendra Pyndiah

1998-01-01

351

Optimum Design of High Speed Prop-Rotors  

NASA Technical Reports Server (NTRS)

The objective of this research is to develop optimization procedures to provide design trends in high speed prop-rotors. The necessary disciplinary couplings are all considered within a closed loop optimization process. The procedures involve the consideration of blade aeroelastic, aerodynamic performance, structural and dynamic design requirements. Further, since the design involves consideration of several different objectives, multiobjective function formulation techniques are developed.

Chattopadhyay, Aditi

1992-01-01

352

Helicoids, Wrinkles, and Loops in Twisted Ribbons  

NASA Astrophysics Data System (ADS)

We investigate the instabilities of a flat elastic ribbon subject to twist under tension and develop an integrated phase diagram of the observed shapes and transitions. We find that the primary buckling mode switches from being localized longitudinally along the length of the ribbon to transverse above a triple point characterized by a crossover tension that scales with ribbon elasticity and aspect ratio. Far from threshold, the longitudinally buckled ribbon evolves continuously into a self-creased helicoid with focusing of the curvature along the triangular edges. Further twist causes an anomalous transition to loops compared with rods due to the self-rigidity induced by the creases. When the ribbon is twisted under high tension, transverse wrinkles are observed due to the development of compressive stresses with higher harmonics for greater width-to-length ratios. Our results can be used to develop functional structures using a wide range of elastic materials and length scales.

Chopin, Julien; Kudrolli, Arshad

2013-10-01

353

Helicoids, wrinkles, and loops in twisted ribbons.  

PubMed

We investigate the instabilities of a flat elastic ribbon subject to twist under tension and develop an integrated phase diagram of the observed shapes and transitions. We find that the primary buckling mode switches from being localized longitudinally along the length of the ribbon to transverse above a triple point characterized by a crossover tension that scales with ribbon elasticity and aspect ratio. Far from threshold, the longitudinally buckled ribbon evolves continuously into a self-creased helicoid with focusing of the curvature along the triangular edges. Further twist causes an anomalous transition to loops compared with rods due to the self-rigidity induced by the creases. When the ribbon is twisted under high tension, transverse wrinkles are observed due to the development of compressive stresses with higher harmonics for greater width-to-length ratios. Our results can be used to develop functional structures using a wide range of elastic materials and length scales. PMID:24206494

Chopin, Julien; Kudrolli, Arshad

2013-10-25

354

Development of agri-pellet production cost and optimum size.  

PubMed

Minimum production cost and optimum plant size were determined for pellet plants using agricultural biomass residue from wheat, barley and oats. Three scenarios involving minimum, average and maximum yields of straw were considered for developing a techno-economic model. The life cycle cost of producing pellets in Western Canada was estimated. The economically optimum size of production plant for the three yield scenarios in tonne year(-1) were 70,000, 150,000 and 150,000, respectively. The corresponding costs of production per tonne are $170.89, $129.42 and $122.17, respectively. However, the cost of pellets does not change much for capacities over 70,000 tonne year(-1) for both the average and maximum yields. The optimum size is same for both average and maximum yield cases. Sensitivity analyses have showed that the total cost of pellet production is most sensitive to field cost followed by transportation cost. Currently, the cost of energy from agri-pellets is higher than that of energy from natural gas. PMID:20189801

Sultana, Arifa; Kumar, Amit; Harfield, Don

2010-07-01

355

Optimum Design of Insulated Compression Plates Subjected to Aerodynamic Heating  

NASA Technical Reports Server (NTRS)

A method to determine the optimum thicknesses of insulation and load-carrying structure has been applied to insulated compression plates subjected to aerodynamic heating. The optimum design results in the lowest combined weight of insulation and load-carrying plate. Load parameters which included the imposed load, insulation conductivity and density, and flight time were found for design strength criteria of compressive yield, compressive buckling, and postbuckling failure. Charts of optimum total weight were prepared for 2024-T3 aluminum alloy, HK3lA magnesium alloy, 17-7 PH stainless steel, and Inconel X for each design criterion. The results show that 17-7 PH stainless steel and Inconel X are most efficient for compressive yield stress and that HK3lA magnesium is most efficient for buckling. HK31A magnesium is also most efficient for the postbuckling failure criterion except under conditions of light loading and long flight periods; under such conditions uninsulated Inconel X may be superior for environmental temperature less than 1,200 F. Insulated magnesium is more efficient than insulated aluminum because the lower density of magnesium permits the use of thick plates with large heat capacity. When more than one failure mode was applied to a design, it was found that the minimum weight structure was one in which all modes of failure occurred at the design load.

Davidson, John R.; Dalby, James F.

1961-01-01

356

Automated optimum design of wing structures. Deterministic and probabilistic approaches  

NASA Technical Reports Server (NTRS)

The automated optimum design of airplane wing structures subjected to multiple behavior constraints is described. The structural mass of the wing is considered the objective function. The maximum stress, wing tip deflection, root angle of attack, and flutter velocity during the pull up maneuver (static load), the natural frequencies of the wing structure, and the stresses induced in the wing structure due to landing and gust loads are suitably constrained. Both deterministic and probabilistic approaches are used for finding the stresses induced in the airplane wing structure due to landing and gust loads. A wing design is represented by a uniform beam with a cross section in the form of a hollow symmetric double wedge. The airfoil thickness and chord length are the design variables, and a graphical procedure is used to find the optimum solutions. A supersonic wing design is represented by finite elements. The thicknesses of the skin and the web and the cross sectional areas of the flanges are the design variables, and nonlinear programming techniques are used to find the optimum solution.

Rao, S. S.

1982-01-01

357

Optimum combining of residual carrier array signals in correlated noises  

NASA Technical Reports Server (NTRS)

An array feed combining system for the recovery of signal-to-noise ratio (SNR) loss due to antenna reflector deformation has been implemented and is currently being evaluated on the Jet Propulsion Laboratory 34-m DSS-13 antenna. The current signal-combining system operates under the assumption that the white Gaussian noise processes in the received signals from different array elements are mutually uncorrelated. However, experimental data at DSS 13 indicate that these noise processes are indeed mutually correlated. The objective of this work is to develop a signal-combining system optimized to account for the mutual correlations between these noise processes. The set of optimum combining weight coefficients that maximizes the combined signal SNR in the correlated noises environment is determined. These optimum weights depend on unknown signal and noise covariance parameters. A maximum-likelihood approach is developed to estimate these unknown parameters to obtain estimates of the optimum weight coefficients based on residual carrier signal samples. The actual combined signal SNR using the estimated weight coefficients is derived and shown to converge to the maximum achievable SNR as the number of signal samples increases. These results are also verified by simulation. A numerical example shows a significant improvement in SNR performance can be obtained, especially when the amount of correlation increases.

Liang, R.; Suen, P. H.; Tan, H. H.

1996-01-01

358

Optimum Combining of Residual Carrier Array Signals in Correlated Noises  

NASA Technical Reports Server (NTRS)

An array feed combining system for the recovery of signal-to-noise ratio (SNR) loss due to antenna reflector deformation has been implemented and is currently being evaluated on the Jet Propulsion Laboratory 34-m DSS-13 antenna. The current signal-combining system operates under the assumption that the white Gaussian noise processes in the received signals from different array elements are mutually uncorrelated. However, experimental data at DSS 13 indicate that these noise processes are indeed mutually correlated. The objective of this work is to develop a signal-combining system optimized to account for the mutual correlations between these noise processes. The set of optimum combining weight coefficients that maximizes the combined signal SNR in the correlated noises environment is determined. These optimum weights depend on unknown signal and noise covariance parameters. A maximum-likelihood approach is developed to estimate these unknown parameters to obtain estimates of the optimum weight coefficients based on residual carrier signal samples. The actual combined signal SNR using the estimated weight coefficients is derived and shown to converge to the maximum achievable SNR as the number of signal samples increases. These results are also verified by simulation. A numerical example shows a significant improvement in SNR performance can be obtained, especially when the amount of correlation increases.

Tan, H. H.; Liang, R.; Suen, P.-H.

1996-01-01

359

Optimum design of structures subject to general periodic loads  

NASA Technical Reports Server (NTRS)

A simplified version of Icerman's problem regarding the design of structures subject to a single harmonic load is discussed. The nature of the restrictive conditions that must be placed on the design space in order to ensure an analytic optimum are discussed in detail. Icerman's problem is then extended to include multiple forcing functions with different driving frequencies. And the conditions that now must be placed upon the design space to ensure an analytic optimum are again discussed. An important finding is that all solutions to the optimality condition (analytic stationary design) are local optima, but the global optimum may well be non-analytic. The more general problem of distributing the fixed mass of a linear elastic structure subject to general periodic loads in order to minimize some measure of the steady state deflection is also considered. This response is explicitly expressed in terms of Green's functional and the abstract operators defining the structure. The optimality criterion is derived by differentiating the response with respect to the design parameters. The theory is applicable to finite element as well as distributed parameter models.

Reiss, Robert; Qian, B.

1989-01-01

360

NCHRP Report 350 Testing of Montana Portable Concrete Safety Shape Barriers.  

National Technical Information Service (NTIS)

The existing Montana DOT concrete median barrier sections are 3.048 m (10 ft) long New Jersey shaped barriers with a pin-and-loop connection. Two pairs of 25 mm (1 inch) diameter wire rope loops are connected using a 660 mm (26 inch) long, 25 mm (1 inch) ...

C. E. Buth N. Sheikh R. P. Bligh W. L. Menges R. R. Haug

2003-01-01

361

Optimum rocket propulsion for energy-limited transfer  

NASA Technical Reports Server (NTRS)

In order to effect large-scale return of extraterrestrial resources to Earth orbit, it is desirable to optimize the propulsion system to maximize the mass of payload returned per unit energy expended. This optimization problem is different from the conventional rocket propulsion optimization. A rocket propulsion system consists of an energy source plus reaction mass. In a conventional chemical rocket, the energy source and the reaction mass are the same. For the transportation system required, however, the best system performance is achieved if the reaction mass used is from a locally available source. In general, the energy source and the reaction mass will be separate. One such rocket system is the nuclear thermal rocket, in which the energy source is a reactor and the reaction mass a fluid which is heated by the reactor and exhausted. Another energy-limited rocket system is the hydrogen/oxygen rocket where H2/O2 fuel is produced by electrolysis of water using a solar array or a nuclear reactor. The problem is to choose the optimum specific impulse (or equivalently exhaust velocity) to minimize the amount of energy required to produce a given mission delta-v in the payload. The somewhat surprising result is that the optimum specific impulse is not the maximum possible value, but is proportional to the mission delta-v. In general terms, at the beginning of the mission it is optimum to use a very low specific impulse and expend a lot of reaction mass, since this is the most energy efficient way to transfer momentum. However, as the mission progresses, it becomes important to minimize the amount of reaction mass expelled, since energy is wasted moving the reaction mass. Thus, the optimum specific impulse will increase with the mission delta-v. Optimum I(sub sp) is derived for maximum payload return per energy expended for both the case of fixed and variable I(sub sp) engines. Sample missions analyzed include return of water payloads from the moons of Mars and of Saturn.

Zuppero, Anthony; Landis, Geoffrey A.

1991-01-01

362

Integrated optical phase locked loop.  

SciTech Connect

A silicon photonics based integrated optical phase locked loop is utilized to synchronize a 10.2 GHz voltage controlled oscillator with a 509 MHz mode locked laser, achieving 32 fs integrated jitter over 300 kHz bandwidth.

Lentine, Anthony L.; Kim, Jungwon (Massachusetts Institute of Technology, Cambridge, MA); Trotter, Douglas Chandler; DeRose, Christopher T.; Kartner, Franz X. (Massachusetts Institute of Technology, Cambridge, MA); Byun, Hyunil (Massachusetts Institute of Technology, Cambridge, MA); Nejadmalayeri, Amir H. (Massachusetts Institute of Technology, Cambridge, MA); Watts, Michael R.; Zortman, William A.

2010-12-01

363

Faraday Loop in Changing Field  

NSDL National Science Digital Library

The EJS Faraday Loop Changing Field Model shows the induced emf in a changing external magnetic field. You can control the frequency, magnitude and type of variation in the external field as you would in the laboratory when using a function generator to produce current in a large coil. You can also change the size and orientation of the conducting loop. If Ejs is installed, right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item allows for editing of the model. The Faraday Loop Changing Field model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_em_FaradayLoopChangingField.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models.

Cox, Anne

2011-12-07

364

CAD based shape optimization for gas turbine component design  

Microsoft Academic Search

In order to improve product characteristics, engineering design makes increasing use of Robust Design and Multidisciplinary\\u000a Design Optimisation. Common to both methodologies is the need to vary the object’s shape and to assess the resulting change\\u000a in performance, both executed within an automatic loop. This shape change can be realised by modifying the parameter values\\u000a of a suitably parameterised Computer

Djordje Brujic; Mihailo Ristic; Massimiliano Mattone; Paolo Maggiore; Gian Paolo De Poli

2010-01-01

365

Shape Dynamics and Effective Field Theory  

NASA Astrophysics Data System (ADS)

Shape dynamics is a gauge theory based on spatial diffeomorphism- and Weyl-invariance which is locally indistinguishable from classical general relativity. If taken seriously, it suggests that the space-time geometry picture that underlies general relativity can be replaced by a picture based on spatial conformal geometry. This classically well-understood trading of gauge symmetries opens new conceptual avenues in many approaches to quantum gravity. This paper focusses on the general implications for quantum gravity and effective field theory and considers the application of the shape dynamics picture in the exact renormalization group approaches to gravity, loop- and polymer-quantization approaches to gravity and low energy effective field theories. Also, the interpretation of known results is discussed through the shape dynamics picture, particularly holographic renormalization and the problem of time in canonical quantum gravity.

Koslowski, Tim A.

2013-05-01

366

Loop quantum cosmology: Recent progress  

Microsoft Academic Search

Aspects of the full theory of loop quantum gravity can be studied in a simpler context by reducing to symmetric models like\\u000a cosmological ones. This leads to several applications where loop effects play a significant role when one is sensitive to\\u000a the quantum regime. As a consequence, the structure of and the approach to classical singularities are very different from

Martin Bojowald

2004-01-01

367

The Structure of Coronal Loops  

NASA Technical Reports Server (NTRS)

It is widely believed that the simple coronal loops observed by XUV imagers, such as EIT, TRACE, or XRT, actually have a complex internal structure consisting of many (perhaps hundreds) of unresolved, interwoven "strands". According to the nanoflare model, photospheric motions tangle the strands, causing them to reconnect and release the energy required to produce the observed loop plasma. Although the strands, themselves, are unresolved by present-generation imagers, there is compelling evidence for their existence and for the nanoflare model from analysis of loop intensities and temporal evolution. A problem with this scenario is that, although reconnection can eliminate some of the strand tangles, it cannot destroy helicity, which should eventually build up to observable scales. we consider, therefore, the injection and evolution of helicity by the nanoflare process and its implications for the observed structure of loops and the large-scale corona. we argue that helicity does survive and build up to observable levels, but on spatial and temporal scales larger than those of coronal loops. we discuss the implications of these results for coronal loops and the corona, in general .

Antiochos, Spiro K.

2009-01-01

368

Melting studies of dangling-ended DNA hairpins: effects of end length, loop sequence and biotinylation of loop bases  

PubMed Central

The effects of 3? single-strand dangling-ends of different lengths, sequence identity of hairpin loop, and hairpin loop biotinylation at different loop residues on DNA hairpin thermodynamic stability were investigated. Hairpins contained 16 bp stem regions and five base loops formed from the sequence, 5?-TAGTCGACGTGGTCC-N5-GGACCACGTCGACTAG-En-3?. The length of the 3? dangling-ends (En) was n = 13 or 22 bases. The identities of loop bases at positions 2 and 4 were varied. Biotinylation was varied at loop base positions 2, 3 or 4. Melting buffers contained 25 or 115 mM Na+. Average tm values for all molecules were 73.5 and 84.0°C in 25 and 115 mM Na+, respectively. Average two-state parameters evaluated from van’t Hoff analysis of the melting curve shapes in 25 mM Na+ were ?HvH = 84.8 ± 15.5 kcal/mol, ?SvH = 244.8 ± 45.0 cal/K·mol and ?GvH = 11.9 ± 2.1 kcal/mol. In 115 mM Na+, two-state parameters were not very different at ?HvH = 80.42 ± 12.74 kcal/mol, ?SvH = 225.24 ± 35.88 cal/K·mol and ?GvH = 13.3 ± 2.0 kcal/mol. Differential scanning calorimetry (DSC) was performed to test the validity of the two-state assumption and evaluated van’t Hoff parameters. Thermodynamic parameters from DSC measurements (within experimental error) agreed with van’t Hoff parameters, consistent with a two-state process. Overall, dangling-end DNA hairpin stabilities are not affected by dangling-end length, loop biotinylation or sequence and vary uniformly with [Na+]. Consider able freedom is afforded when designing DNA hairpins as probes in nucleic acid based detection assays, such as microarrays.

Riccelli, Peter V.; Mandell, Kathleen E.; Benight, Albert S.

2002-01-01

369

Pulse evolution in nonlinear optical loop mirrors  

NASA Astrophysics Data System (ADS)

In this thesis, a mathematical analysis of the nonlinear Sagnac interferometer switch and degenerate optical parametric oscillator is presented. These all-optical devices have potentially wide applications in fiber-optic communication networks. The nonlinear optical loop mirror is an important component in both of these devices. In the first part, the interaction of two copropagating pulses with different carrier frequencies in a nonlinear optical loop mirror is described using coupled nonlinear Schrödinger equations. The signal pulse is assumed to propagate as a soliton. The control pulse is assumed to have a Gaussian shape and experience normal group velocity dispersion. Soliton perturbation theory is used to approximate the evolution of the signal pulse in the limit of a strong control pulse and large collision velocity. Control pulse evolution is approximated using a variational method. An integral equation for the frequency shift induced in the signal pulse by control pulse spreading is derived and analyzed asymptotically in the limit of large collision velocity. The analysis suggests that pre-chirping the control pulse before the interaction can significantly reduce the residual frequency shift, and predicts a value for the initial chirp parameter that should be used. Numerical studies confirm the existence of the frequency shift, and demonstrate that the analysis gives a good approximation to the optimal chirp parameter. The second part is a study of an all-fiber degenerate optical parametric oscillator in which gain is provided by a phase sensitive amplifier based on a nonlinear optical loop mirror. A partial differential equation modeling the evolution of pulses in this device is derived in the limit of small optical path length. The model PDE includes self phase modulation in the cavity and PSA as well as group velocity dispersion in the cavity, but neglects dispersion in the PSA. Results obtained using the PDE model agree well with numerical simulations of the individual DOPO elements. The PDE model is used to study the behavior of the DOPO under various parameter variations. Bistable operation is observed for a range of cavity lengths. The influence of group velocity dispersion on the steady-state pulse shape is investigated.

Mills, Michael John

1999-12-01

370

Optimized conical shaped charge design using the SCAP (Shaped Charge Analysis Program) code  

SciTech Connect

The Shaped Charge Analysis Program (SCAP) is used to analytically model and optimize the design of Conical Shaped Charges (CSC). A variety of existing CSCs are initially modeled with the SCAP code and the predicted jet tip velocities, jet penetrations, and optimum standoffs are compared to previously published experimental results. The CSCs vary in size from 0.69 inch (1.75 cm) to 9.125 inch (23.18 cm) conical liner inside diameter. Two liner materials (copper and steel) and several explosives (Octol, Comp B, PBX-9501) are included in the CSCs modeled. The target material was mild steel. A parametric study was conducted using the SCAP code to obtain the optimum design for a 3.86 inch (9.8 cm) CSC. The variables optimized in this study included the CSC apex angle, conical liner thickness, explosive height, optimum standoff, tamper/confinement thickness, and explosive width. The non-dimensionalized jet penetration to diameter ratio versus the above parameters are graphically presented. 12 refs., 10 figs., 7 tabs.

Vigil, M.G.

1988-09-01

371

Dynamical expansion of a dislocation loop on a two-dimensional periodic potential  

Microsoft Academic Search

The equilibrium shape and the motion of a dislocation loop on twodimensional periodic potential fields are discussed. The Peierls stress for a straight dislocation along non-close-packed direction as well as the Peierls stress for kink migration can be neglected in comparison with that for a dislocation along close-packed directions, provided that the potential is not high. A dislocation loop can

H. Koizumi; K. Ohno; T. Suzuki; F. R. N. Nabarro

1999-01-01

372

Computational analysis of looping of a large family of highly bent DNA by LacI.  

PubMed

Sequence-dependent intrinsic curvature of DNA influences looping by regulatory proteins such as LacI and NtrC. Curvature can enhance stability and control shape, as observed in LacI loops formed with three designed sequences with operators bracketing an A-tract bend. We explore geometric, topological, and energetic effects of curvature with an analysis of a family of highly bent sequences, using the elastic rod model from previous work. A unifying straight-helical-straight representation uses two phasing parameters to describe sequences composed of two straight segments that flank a common helically supercoiled segment. We exercise the rod model over this two-dimensional space of phasing parameters to evaluate looping behaviors. This design space is found to comprise two subspaces that prefer parallel versus anti-parallel binding topologies. The energetic cost of looping varies from 4 to 12 kT. Molecules can be designed to yield distinct binding topologies as well as hyperstable or hypostable loops and potentially loops that can switch conformations. Loop switching could be a mechanism for control of gene expression. Model predictions for linking numbers and sizes of LacI-DNA loops can be tested using multiple experimental approaches, which coupled with theory could address whether proteins or DNA provide the observed flexibility of protein-DNA loops. PMID:18931251

Lillian, Todd D; Goyal, Sachin; Kahn, Jason D; Meyhöfer, Edgar; Perkins, N C

2008-12-15

373

Generation of rectangular prismatic dislocation loops in shells and cores of composite nanoparticles  

NASA Astrophysics Data System (ADS)

A theoretical model has been proposed for describing the relaxation of misfit stresses in a spherically symmetric composite core-shell nanoparticle due to the generation and expansion of rectangular prismatic dislocation loops at the internal and external interfaces. The critical conditions of the formation of these loops have been calculated for nanoparticles consisting of a relatively massive core and a thin shell. It has been shown that the generation of dislocation loops is possible when the misfit of the lattice parameters of the core and shell of the nanoparticle exceeds a critical value that depends on the nanoparticle radius, the shell thickness, the loop formation position, and the shape of loops. This condition holds for a loop in the shell when the shell thickness either lies in a specific range of small values or (for a larger misfit) is less than a critical value. For the generation of loops in the core, the shell thickness should exceed a critical value. The dislocation loops elongated along the core-shell interface are formed more readily. As the shell thickness increases at a fixed nanoparticle radius, the energetically more favorable generation of a dislocation loop occurs first from the free surface into the bulk of the shell, then from the interface into the shell, and finally from the interface into the core of the nanoparticle.

Gutkin, M. Yu.; Smirnov, A. M.

2014-04-01

374

Preliminary evaluation of the utility of a large spacing electromagnetic loop-loop logging tool  

SciTech Connect

This paper analyses the potential of using loop-loop large spacing downhole electromagnetic measurements for detection of clay zones within a tuff and alluvium matrix. A brief background on surface loop-loop electromagnetic methods is given followed by a section on source and receiver loop orientation. Measurement sensitivity is discussed followed by the modelling strategy used. The value of the loop-loop electromagnetic tool is assessed in terms of usefulness to containment evaluation. 4 refs., 13 figs.

Harben, P.

1985-10-01

375

Low temperature enantiotropic nematic phases from V-shaped, shape-persistent molecules  

PubMed Central

Summary A series of V-shaped, shape-persistent thiadiazole nematogens, based on an oligo(phenylene ethynylene) scaffold with ester groups connected via alkyloxy spacers, was efficiently prepared by a two-step procedure. Phase engineering results in an optimum of the mesophase range and low melting temperature when the nematogens are desymmetrised with a butoxy and a heptyloxy spacer. The mesophases are enantiotropic and over the whole temperature range nematic. For the optimised mesogen structure, optical investigations by conoscopy monitored a uniaxial nematic phase upon cooling from the isotropic phase to room temperature (?T = 150 °C). X-ray studies on magnetic-field-aligned samples of this mesogen family revealed a general pattern, indicating the alignment of two molecular axes along individual directors in the magnetic field. These observations may be rationalised with larger assemblies of V-shaped molecules isotropically distributed around the direction of the magnetic field.

Seltmann, Jens

2009-01-01

376

Design, fabrication and delivery of an improved single Elastic Loop Mobility System (ELMS)  

NASA Technical Reports Server (NTRS)

Several significant design improvements have been incorporated into the second-generation full-scale ELMS unit. A major improved design accomplishment was the increase of the load carrying capacity of elastic loops without severe weight or stress penalties. Redesign of the loop form and size, plus selection of a more advanced titanium alloy, resulted in performance characteristics representing a marked improvement over the first-generation unit. Another important design improvement was the shaping of the loop's footprint into a favorable form for uniform pressure distribution. Other improvements are associated with a more efficient drive torque transmission from the internal drive drums to the elastic loop which are expected to reduce the internal losses of the drive system. The new ELMS unit will be capable of being integrated, on a modularized basis, with a multi-loop articulated ELMS test vehicle as the next logical step in the development of the mobility concept.

Trautwein, W.

1972-01-01

377

Filter for third order phase locked loops  

NASA Technical Reports Server (NTRS)

Filters for third-order phase-locked loops are used in receivers to acquire and track carrier signals, particularly signals subject to high doppler-rate changes in frequency. A loop filter with an open-loop transfer function and set of loop constants, setting the damping factor equal to unity are provided.

Crow, R. B.; Tausworthe, R. C. (inventors)

1973-01-01

378

Bending of the looping heart: differential growth revisited.  

PubMed

In the early embryo, the primitive heart tube (HT) undergoes the morphogenetic process of c-looping as it bends and twists into a c-shaped tube. Despite intensive study for nearly a century, the physical forces that drive looping remain poorly understood. This is especially true for the bending component, which is the focus of this paper. For decades, experimental measurements of mitotic rates had seemingly eliminated differential growth as the cause of HT bending, as it has commonly been thought that the heart grows almost exclusively via hyperplasia before birth and hypertrophy after birth. Recently published data, however, suggests that hypertrophic growth may play a role in looping. To test this idea, we developed finite-element models that include regionally measured changes in myocardial volume over the HT. First, models based on idealized cylindrical geometry were used to simulate the bending process in isolated hearts, which bend without the complicating effects of external loads. With the number of free parameters in the model reduced to the extent possible, stress and strain distributions were compared to those measured in embryonic chick hearts that were isolated and cultured for 24?h. The results show that differential growth alone yields results that agree reasonably well with the trends in our data, but adding active changes in myocardial cell shape provides closer quantitative agreement with stress measurements. Next, the estimated parameters were extrapolated to a model based on realistic 3D geometry reconstructed from images of an actual chick heart. This model yields similar results and captures quite well the basic morphology of the looped heart. Overall, our study suggests that differential hypertrophic growth in the myocardium (MY) is the primary cause of the bending component of c-looping, with other mechanisms possibly playing lesser roles. PMID:24509638

Shi, Yunfei; Yao, Jiang; Xu, Gang; Taber, Larry A

2014-08-01

379

Kalman Orbit Optimized Loop Tracking  

NASA Technical Reports Server (NTRS)

Under certain conditions of low signal power and/or high noise, there is insufficient signal to noise ratio (SNR) to close tracking loops with individual signals on orbiting Global Navigation Satellite System (GNSS) receivers. In addition, the processing power available from flight computers is not great enough to implement a conventional ultra-tight coupling tracking loop. This work provides a method to track GNSS signals at very low SNR without the penalty of requiring very high processor throughput to calculate the loop parameters. The Kalman Orbit-Optimized Loop (KOOL) tracking approach constitutes a filter with a dynamic model and using the aggregate of information from all tracked GNSS signals to close the tracking loop for each signal. For applications where there is not a good dynamic model, such as very low orbits where atmospheric drag models may not be adequate to achieve the required accuracy, aiding from an IMU (inertial measurement unit) or other sensor will be added. The KOOL approach is based on research JPL has done to allow signal recovery from weak and scintillating signals observed during the use of GPS signals for limb sounding of the Earth s atmosphere. That approach uses the onboard PVT (position, velocity, time) solution to generate predictions for the range, range rate, and acceleration of the low-SNR signal. The low- SNR signal data are captured by a directed open loop. KOOL builds on the previous open loop tracking by including feedback and observable generation from the weak-signal channels so that the MSR receiver will continue to track and provide PVT, range, and Doppler data, even when all channels have low SNR.

Young, Lawrence E.; Meehan, Thomas K.

2011-01-01

380

Determination of optimum electrolyte composition for molten carbonate fuel cells  

SciTech Connect

The objective of this study is to determine the optimum electrolyte composition for molten carbonate fuel cells. To accomplish this, the contractor will provide: (1) Comprehensive reports of on-going efforts to optimize carbonate composition. (2) A list of characteristics affected by electrolyte composition variations (e.g. ionic conductivity, vapor pressure, melting range, gas solubility, exchange current densities on NiO, corrosion and cathode dissolution effects). (3) Assessment of the overall effects that these characteristics have state-of-the-art cell voltage and lifetime.

Yuh, C.Y.; Pigeaud, A.

1987-01-01

381

Determination of optimum electrolyte composition for molten carbonate fuel cells  

SciTech Connect

The objective of this study is to determine the optimum electrolyte composition for molten carbonate fuel cells. To accomplish this, the contractor will provide: (1) Comprehensive reports of on-going efforts to optimize carbonate composition. (2) A list of characteristics affected by electrolyte composition variations (e.g. ionic conductivity, vapor pressure, melting range, gas solubility, exchange current densities on NiO, corrosion and cathode dissolution effects). (3) Assessment of the overall effects that these characteristics have on state-of-the-art cell voltage and lifetime.

Yuh, C.Y.; Pigeaud, A.

1987-01-01

382

Modeling and optimum time performance for concurrent processing  

NASA Technical Reports Server (NTRS)

The development of a new graph theoretic model for describing the relation between a decomposed algorithm and its execution in a data flow environment is presented. Called ATAMM, the model consists of a set of Petri net marked graphs useful for representing decision-free algorithms having large-grained, computationally complex primitive operations. Performance time measures which determine computing speed and throughput capacity are defined, and the ATAMM model is used to develop lower bounds for these times. A concurrent processing operating strategy for achieving optimum time performance is presented and illustrated by example.

Mielke, Roland R.; Stoughton, John W.; Som, Sukhamoy

1988-01-01

383

Design optimum frac jobs using virtual intelligence techniques  

NASA Astrophysics Data System (ADS)

Designing optimal frac jobs is a complex and time-consuming process. It usually involves the use of a two- or three-dimensional computer model. For the computer models to perform as intended, a wealth of input data is required. The input data includes wellbore configuration and reservoir characteristics such as porosity, permeability, stress and thickness profiles of the pay layers as well as the overburden layers. Among other essential information required for the design process is fracturing fluid type and volume, proppant type and volume, injection rate, proppant concentration and frac job schedule. Some of the parameters such as fluid and proppant types have discrete possible choices. Other parameters such as fluid and proppant volume, on the other hand, assume values from within a range of minimum and maximum values. A potential frac design for a particular pay zone is a combination of all of these parameters. Finding the optimum combination is not a trivial process. It usually requires an experienced engineer and a considerable amount of time to tune the parameters in order to achieve desirable outcome. This paper introduces a new methodology that integrates two virtual intelligence techniques, namely, artificial neural networks and genetic algorithms to automate and simplify the optimum frac job design process. This methodology requires little input from the engineer beyond the reservoir characterizations and wellbore configuration. The software tool that has been developed based on this methodology uses the reservoir characteristics and an optimization criteria indicated by the engineer, for example a certain propped frac length, and provides the detail of the optimum frac design that will result in the specified criteria. An ensemble of neural networks is trained to mimic the two- or three-dimensional frac simulator. Once successfully trained, these networks are capable of providing instantaneous results in response to any set of input parameters. These networks will be used as the fitness function for a genetic algorithm routine that will search for the best combination of the design parameters for the frac job. The genetic algorithm will search through the entire solution space and identify the optimal combination of parameters to be used in the design process. Considering the complexity of this task this methodology converges relatively fast, providing the engineer with several near-optimum scenarios for the frac job design. These scenarios, which can be achieved in just a minute or two, can be valuable initial points for the engineer to start his/her design job and save him/her hours of runs on the simulator.

Mohaghegh, Shahab; Popa, Andrei; Ameri, Sam

2000-10-01

384

Post the Shapes  

NSDL National Science Digital Library

In this game students use basic transformations (sliding, flipping and turning) to make one or more shapes coincide with a congruent shape on a Cartesian plane. Players are challenged to complete the matching in the fewest possible moves.

2011-01-01

385

Static shape control for adaptive wings  

NASA Astrophysics Data System (ADS)

A theoretical method was developed and experimentally validated, to control the static shape of flexible structures by employing internal translational actuators. A finite element model of the structure, without the actuators present, is employed to obtain the multiple-input, multiple-output control-system gain matrices for actuator-load control as well as actuator-displacement control. The method is applied to the quasistatic problem of maintaining an optimum-wing cross section during various transonic-cruise flight conditions to obtain significant reductions in the shock-induced drag. Only small, potentially achievable, adaptive modifications to the profile are required. The adaptive-wing concept employs actuators as truss elements of active ribs to reshape the wing cross section by deforming the structure. Finite element analyses of an adaptive-rib model verify the controlled-structure theory. Experiments on the model were conducted, and arbitrarily selected deformed shapes were accurately achieved.

Austin, Fred; Rossi, Michael J.; van Nostrand, William; Knowles, Gareth; Jameson, Antony

1994-09-01

386

Posterior shape models.  

PubMed

We present a method to compute the conditional distribution of a statistical shape model given partial data. The result is a "posterior shape model", which is again a statistical shape model of the same form as the original model. This allows its direct use in the variety of algorithms that include prior knowledge about the variability of a class of shapes with a statistical shape model. Posterior shape models then provide a statistically sound yet easy method to integrate partial data into these algorithms. Usually, shape models represent a complete organ, for instance in our experiments the femur bone, modeled by a multivariate normal distribution. But because in many application certain parts of the shape are known a priori, it is of great interest to model the posterior distribution of the whole shape given the known parts. These could be isolated landmark points or larger portions of the shape, like the healthy part of a pathological or damaged organ. However, because for most shape models the dimensionality of the data is much higher than the number of examples, the normal distribution is singular, and the conditional distribution not readily available. In this paper, we present two main contributions: First, we show how the posterior model can be efficiently computed as a statistical shape model in standard form and used in any shape model algorithm. We complement this paper with a freely available implementation of our algorithms. Second, we show that most common approaches put forth in the literature to overcome this are equivalent to probabilistic principal component analysis (PPCA), and Gaussian Process regression. To illustrate the use of posterior shape models, we apply them on two problems from medical image analysis: model-based image segmentation incorporating prior knowledge from landmarks, and the prediction of anatomically correct knee shapes for trochlear dysplasia patients, which constitutes a novel medical application. Our experiments confirm that the use of conditional shape models for image segmentation improves the overall segmentation accuracy and robustness. PMID:23837968

Albrecht, Thomas; Lüthi, Marcel; Gerig, Thomas; Vetter, Thomas

2013-12-01

387

Fun with Shapes  

NSDL National Science Digital Library

In this activity, early learners combine pre-cut recognizable shapes and their own abstract ideas to make representational pictures (e.g. houses, trees, shoes). This exploration of shape identification and transformation develops problem-solving skills. Use the provided open-ended questions to help learners communicate the processes they used to select shapes and colors as well as develop and practice a vocabulary of color and shapes.

Omsi

2004-01-01

388

Inferring shape evolution  

Microsoft Academic Search

Dynamic shapes, namely shapes that change with time, represent an important issue in several scientific and technological contexts. The current article presents a model-based mathematic-computational approach for inferring the processes governing some of the most representative types of shape evolution, with special attention given to biological shapes. The considered models include functional mappings, convolution-based evolution and normal wavefront propagation. The

L. Da Fountoura; A. G. Campos Bianchi

2001-01-01

389

The Effects of Including Non-Thermal Particles in Flare Loop Models  

NASA Astrophysics Data System (ADS)

In this work, we use HyLoop (Winter et al. 2011), a loop model that can incorporate the effects of both MHD and non-thermal particle populations, to simulate soft X-ray emissions in various situations. First of all, we test the effect of acceleration location on the emission in several XRT filters by simulating a series of post flare loops with different injection points for the non-thermal particle beams. We use an injection distribution peaked at the loop apex to represent a direct acceleration model, and an injection distribution peaked at the footpoints to represent the Alfvén wave interaction model. We find that footpoint injection leads to several early peaks in the apex-to-footpoint emission ratio. Second, we model a loop with cusp-shaped geometry based on the eruption model developed byLin & Forbes (2000) and Reeves & Forbes (2005a), and find that early in the flare, emission in the loop footpoints is much brighter in the XRT filters if non-thermal particles are included in the calculation. Finally, we employ a multi-loop flare model to simulate thermal emission and compare with a previous model where a semi-circular geometry was used (Reeves et al. 2007). We compare the Geostationary Operational Environmental Satellite (GOES) emission from the two models and find that the cusp-shaped geometry leads to a smaller GOES class flare.

Reeves, K. K.; Winter, H. D.; Larson, N. L.

2012-05-01

390

Picophytoplankton physiology and the microbial loop  

NASA Astrophysics Data System (ADS)

Physiological observations are needed for a better understanding of the complexity of marine ecosystem processes. This information is important for a better model formulation and parameterisation to identify the consequences of, and feedbacks to, global change and to make future projections. Picophytoplankton form the smallest component of the phytoplankton community (˜ 3?m) and show a substantial contribution to phytoplankton biomass in oligotrophic oceans. Here they also have an important function as primary producers in the microbial loop. They include cyanobacteria, represented by Prochlorococcus and Synechococcus, and picoeukaryotes. The aim of this project is to achieve a better representation of picophytoplankton in the global biogeochemical model PlankTOM 10. PlankTOM 10 simplifies the complex ecosystem into 10 conceptual groups also known as plankton functional types (PFTs). These groups of organisms are defined by physiological and biochemical parameters (6 of phytoplankton, 3 of zooplankton and 1 of bacteria). Furthermore, the question will be addressed, whether picophytoplankton are typical K-strategists with low minimum nutrient and high maximum chlorophyll quota relative to carbon, or by having superior nutrient uptake kinetics and light harvesting (high ?Chl). Laboratory experiments showed that the smaller picoprokaryotes respond faster to increasing light intensities than their picoeukaryotic counterpart. Preliminary data show that the initial slope of the photosynthesis vs. irradiance curve (?Chl) of picoprokaryotes is about 1.5 times higher than of picoeukaryotes. This is consistent with their common distribution at the deep chlorophyll maximum. The maximum chlorophyll quota are not significantly different. Temperature experiments confirmed that the maximum growth rates of picophytoplankton at the optimum temperature (0.47 ± 0.17 d-1 for prokaryotes and 1.05 ± 0.47 d-1 for eukaryotes) are significantly lower than of diatoms (1.57 ± 0.73 d-1, Chollet et al. in prep.) and not significantly different from coccolithophores (0.68 ± 0.10 d-1, Buitenhuis et al. 2008), consistent with the characterisation of picophytoplanton as K-strategists. Their optimum temperatures were found to be 22.7 ± 2.0 ° C for prokaryotes and 23.6 ± 3.1 ° C for eukaryotes. Nutrient limitation experiments will be conducted to characterize the nutrient uptake and elemental composition of picophytoplankton. Finally the results of all experiments will then be used to improve the representation of picophytoplankton in PlankTOM10, evaluated against a recently compiled global database of picophytoplankton biomass.

Stawiarski, Beate

2013-04-01

391

The Shape of Thought  

ERIC Educational Resources Information Center

When children learn the name of a novel object, they tend to extend that name to other objects similar in shape--a phenomenon referred to as the shape bias. Does the shape bias stem from learned associations between names and categories of objects, or does it derive from more general properties of children's understanding of language and the…

Markson, Lori; Diesendruck, Gil; Bloom, Paul

2008-01-01

392

The Princeton Shape Benchmark  

Microsoft Academic Search

In recent years, many shape representations and geomet- ric algorithms have been proposed for matching 3D shapes. Usually, each algorithm is tested on a different (small) database of 3D models, and thus no direct comparison is available for competing methods. In this paper, we describe the Princeton Shape Bench- mark (PSB), a publicly available database of polygonal models collected from

Philip Shilane; Patrick Min; Michael M. Kazhdan; Thomas A. Funkhouser

2004-01-01

393

3D Shapes Video  

NSDL National Science Digital Library

This upbeat music video reviews 3D shapes including the sphere, cylinder, cube, and cone. As each 3D shape is presented, examples of things we see every day that have the same shape are also shown for reinforcement. (Length: 3:18)

Kindergarten, Harry

2011-06-17

394

The Hue of Shapes  

ERIC Educational Resources Information Center

This article presents an experimental study on the naturally biased association between shape and color. For each basic geometric shape studied, participants were asked to indicate the color perceived as most closely related to it, choosing from the Natural Color System Hue Circle. Results show that the choices of color for each shape were not…

Albertazzi, Liliana; Da Pos, Osvaldo; Canal, Luisa; Micciolo, Rocco; Malfatti, Michela; Vescovi, Massimo

2013-01-01

395

Creating the feedback loop: closed-loop neurostimulation.  

PubMed

Current DBS therapy delivers a train of electrical pulses at set stimulation parameters. This open-loop design is effective for movement disorders, but therapy may be further optimized by a closed loop design. The technology to record biosignals has outpaced our understanding of their relationship to the clinical state of the whole person. Neuronal oscillations may represent or facilitate the cooperative functioning of brain ensembles, and may provide critical information to customize neuromodulation therapy. This review addresses advances to date, not of the technology per se, but of the strategies to apply neuronal signals to trigger or modulate stimulation systems. PMID:24262909

Hebb, Adam O; Zhang, Jun Jason; Mahoor, Mohammad H; Tsiokos, Christos; Matlack, Charles; Chizeck, Howard Jay; Pouratian, Nader

2014-01-01

396

"Optimum" formulae for heart rate correction of the QT interval.  

PubMed

The study investigated the performance of several generic QT/RR regression models in a dataset of QT and RR intervals obtained from resting electrocardiograms of 1,100 healthy subjects (913 male, mean age 33+/-12 years). All the investigated models have three degrees of freedom and included the hyperparabolic and hyper-hyperbolic models, algorithmic models, negative exponential models, and models involving inverse tangent, hyperbolic tangent, and inverse hyperbolic sign functions. For each generic model, the combination of parameters leading to the lowest regression residuum was found. The results of the study show that the goodness of the optimum fit is practically independent of the generic form of the regression model and that different datasets lead to different combinations of the numerical values of parameters of the corresponding regression models. The study concludes that the search for a universally applicable QT/RR regression model that would provide the best fit in all circumstances is most likely fruitless. Rather, individual studies such as those investigating drug related QT prolongation might benefit from establishing a best-fit regression that would provide the optimum model for each particular dataset. PMID:10598974

Hnatkova, K; Malik, M

1999-11-01

397

Optimum Waveforms for Differential Ion Mobility Spectrometry (FAIMS)  

SciTech Connect

Differential mobility spectrometry or field asymmetric waveform ion mobility spectrometry (FAIMS) has emerged as a major tool for separation and identification of gas-phase ions, particularly in conjunction with mass-spectrometry. In FAIMS, ions are filtered by the difference between mobilities in gases (K) at high and low electric field intensity (E) using asymmetric waveforms. An infinite number of waveform profiles is possible and maximizing the performance within engineering constraints is a major issue in FAIMS technology development. Earlier optimizations assumed the non-constant component of mobility to scale as E2, producing the same result for all ions. Here we show that the optimum profiles for either rectangular or sinusoidal-based waveforms are controlled by the full series expansion of K(E) that always includes terms beyond the 1st proportional to E2. For many ion/gas pairs, the first two terms have different signs and the optimum profiles at sufficiently high E in FAIMS may substantially differ from those found previously, improving the resolving power by up to 2 - 2.5 times. This situation arises for some ions in all FAIMS systems, but becomes more common with recent miniaturized units that employ higher E. With realistic K(E) dependences, the maximum waveform amplitude is not necessarily best and reducing it by up to 20 - 30% is beneficial in some cases. Present findings are particularly relevant to targeted analyses where separation depends on the spread between K(E) functions of specific ions.

Shvartsburg, Alexandre A.; Smith, Richard D.

2008-09-01

398

Optimum Channel Inclination for Gas Venting Under Countercurrent Flow Limitations  

SciTech Connect

Countercurrent flow limitation (CCFL) in the pressurizer surge line of future Pressurized Water Reactors (PWR) with passive safety systems is an important phenomenon in reactor safety analysis. The pressurizer surge line is typically comprised of several sections with various inclination angles. Under certain accident conditions, countercurrent flow takes place in the surge line with liquid flowing down from the pressurizer and steam flowing up from the hot leg. The steam venting rate as well as the liquid draining rate may affect the Emergency Core Cooling System (ECCS) actuation. The objective herein is to develop a physics-based model for evaluating the effect of inclination angle on CCFL. For a given liquid superficial velocity in the countercurrent flow system of the pressurizer surge line, the gas superficial velocity should be as large as possible at the onset of flooding, so that the steam can vent as fast as possible without inhibiting the pressurizer drain rate. Thus the system could de-pressurize in a timely manner to initiate the ECCS actuation. As indicated by CCFL experiments, for a given liquid superficial velocity, the gas superficial velocity attains a greatest value at a certain channel inclination, which is defined as the optimum channel inclination. In the present work, an analytical model is proposed to predict the optimum channel inclination under simplified conditions. The model predictions compare favorably with experimental data. (authors)

Liao, Y.; Vierow, K. [Purdue Unviersity, West Lafayette, IN 47907 (United States)

2006-07-01

399

Optimum pinch grips in the handling of dies.  

PubMed

Handling roller-press dies has caused numerous work-related musculoskeletal disorders in the leather industry. The dies are quite large (0.61 x 0.30 m), heavy (3.5 kg) and are difficult to handle because of the large pinch span requirements (up to 16 cm). The purpose of this study was to determine the optimum pinch span and optimum crossbar angulation to minimize die handling forces. Five-finger pulp-pinch forces were measured on five males and five females with a force-sensitive-resistor instrumented glove while handling a simulated adjustable die. Maximum pinch forces occurred at pinch spans between 1.27 and 3.81 cm, with average female strengths being 57% of average male pinch strengths. Minimum pinch forces to hold the die occurred at a 45 degrees angulation and increased linearly as the angle approached 90 degrees or the normal vertical orientation. The simplest solution to redesigning the dies is to: (1) decrease the distance between the braces to less than 4 cm and (2) slant the braces at 45 degrees. PMID:10975667

Heffernan, C; Freivalds, A

2000-08-01

400

Investigation of Various Essential Factors for Optimum Infrared Thermography  

PubMed Central

ABSTRACT We investigated various essential factors for optimum infrared thermography for cattle clinics. The effect of various factors on the detection of surface temperature was investigated in an experimental room with a fixed ambient temperature using a square positioned on a wall. Various factors of animal objects were examined using cattle to determine the relationships among presence of hair, body surface temperature, surface temperature of the eyeball, the highest temperature of the eye circle, rectum temperature and ambient temperature. Also, the surface temperature of the flank at different time points after eating was examined. The best conditions of thermography for cattle clinics were determined and were as follows: (1) The distance between a thermal camera and an object should be fixed, and the camera should be set within a 45-degree angle with respect to the objects using the optimum focal length. (2) Factors that affect the camera temperature, such as extreme cold or heat, direct sunshine, high humidity and wind, should be avoided. (3) For the comparison of thermographs, imaging should be performed under identical conditions. If this is not achievable, hairless parts should be used.

OKADA, Keiji; TAKEMURA, Kei; SATO, Shigeru

2013-01-01

401

Creatine kinase in serum: 1. Determination of optimum reaction conditions.  

PubMed

To establish optimum conditions for creatine kinase (EC 2.7.3.2) activity measurement with the creatine phosphate in equilibrium creatine reaction, we re-examined all kinetics factors relevant to an optimal and standardized enzyme assay at 30 and 25 degrees C. We determined the pH optimum in vaious buffers, considering the effect of the type and concentration of the buffer, as well as the influence of various buffer anions on the activity. The relation between activity and substrate concentration was shown and the apparent Michaelis constants of creatine kinase for creatine phosphate and ADP were evaluated. We tested the effect on creatine kinase measurement of the concentration of substrates (glucose and NADP+) in the auxillary and indicator reactions, especially the influence of the added auxiliary (hexokinase) and indicator (glucose-6-phosphate dehydrogenase) enzymes on the lag phase, at different temperatures. The NADP+ concentration proved to be the factor limiting the duration of constant reaction rate. We studied the inhibition of creatine kinase and adenylate kinase by AMP and established a convenient AMP concentration. For reactivation of creatine kinase, N-acetyl cysteine as sulfhydryl compound was introduced. Finally, we examined the relationship between activity and temperature. PMID:4240

Szasz, G; Gruber, W; Bernt, E

1976-05-01

402

Investigation of various essential factors for optimum infrared thermography.  

PubMed

We investigated various essential factors for optimum infrared thermography for cattle clinics. The effect of various factors on the detection of surface temperature was investigated in an experimental room with a fixed ambient temperature using a square positioned on a wall. Various factors of animal objects were examined using cattle to determine the relationships among presence of hair, body surface temperature, surface temperature of the eyeball, the highest temperature of the eye circle, rectum temperature and ambient temperature. Also, the surface temperature of the flank at different time points after eating was examined. The best conditions of thermography for cattle clinics were determined and were as follows: (1) The distance between a thermal camera and an object should be fixed, and the camera should be set within a 45-degree angle with respect to the objects using the optimum focal length. (2) Factors that affect the camera temperature, such as extreme cold or heat, direct sunshine, high humidity and wind, should be avoided. (3) For the comparison of thermographs, imaging should be performed under identical conditions. If this is not achievable, hairless parts should be used. PMID:23759714

Okada, Keiji; Takemura, Kei; Sato, Shigeru

2013-10-01

403

Optimum flywheel sizing for parallel and series hybrid vehicles  

SciTech Connect

Flywheels have the possibility of providing high turnaround efficiency and high specific power output. These characteristics are very important for the successful manufacture of parallel and series hybrid vehicles, which have the potential for providing high fuel economy and very low emissions with range and performance comparable to today`s light-duty vehicles. Flywheels have a high specific power output, but relatively low specific energy output. Therefore, it is of importance to determine energy and power requirements for flywheels applied to light-duty vehicles. Vehicle applications that require an energy storage system with high power and low energy are likely to benefit from a flywheel. In this paper, a vehicle simulation code and a flywheel model are applied to the calculation of optimum flywheel energy storage capacity for a parallel and a series hybrid vehicle. A conventional vehicle is also evaluated as a base-case, to provide an indication of the fuel economy gains that can be obtained with flywheel hybrid vehicles. The results of the analysis indicate that the optimum flywheel energy storage capacity is relatively small. This results in a low weight unit that has a significant power output and high efficiency. Emissions generated by the hybrid vehicles are not calculated, but have the potential of being significantly lower than the emissions from the conventional car.

Aceves, S.M.; Smith, J.R.

1996-12-20

404

Optimum conditions for high-quality 3D reconstruction in confocal scanning microscopy  

NASA Astrophysics Data System (ADS)

Confocal Scanning Microscopy (CSM) is very useful to reconstruct 3D image of Bio-cells and the objects that have specification shape in higher axial and lateral resolution and widely used as measurement instrument. A 3D reconstruction is used to visualize confocal images and consists of following processes. The First process is to get 3D data by collecting a series of images at regular focus intervals (Optical Sectioning). The Second process is to fit a curve to a series of 3D data points each pixel. The Third process is to search height information that has maximum value from curve-fitting. However, because of various systematic errors (NOISE) occurred when collecting the information of images through Optical Sectioning and large peak deviation occurred from curve-fitting error, high quality 3D reconstruction is not expected. Also, it takes much time to 3d Reconstruction by using many 3D data in order to acquire high quality and much cost to improve signal-to-noise (SNR) using a higher power laser. So, we are going to define SNR, peak deviation and the order of curve-fitting as important factors and simulate the relation between the factors in order to find a optimum condition for high quality 3D reconstruction in Confoal Scanning Microscopy. If we use optimum condition obtained by this simulation, using a suitable SNR and the suitable number of data and the suitable n-th order curve-fitting, small peak deviation is expected and then, 3D reconstruction of little better quality is expected. Also, it is expected to save.

Kim, Taehoon; Kim, Taejoong; Lee, SeungWoo; Gweon, Dae-Gab; Seo, Jungwoo

2006-03-01

405

Two-channel Costas loop tracking performance for UQPSK signals with arbitrary data formats  

NASA Technical Reports Server (NTRS)

Previous results on the tracking performance of two-channel Costas-type carrier synchronization loops are generalized and corrected, in order that they may be applied to several mixed-format cases. In particular, the mean-square phase jitter performance of these loops with active arm filters, synchronous or asynchronous symbol clocks, and arbitrary data formats on the two channels is examined. It is demonstrated that for each case, selection of the channel gain ratio, as motivated by the MAP estimation theory, does not guarantee optimum loop tracking performance: in some instances, a conventional single-channel Costas loop would outperform the two-channel version with the MAP choice of gain ratio. It is suggested that the gain ratio be chosen to directly minimize the mean-square phase tracking jitter which is equivalent to minimizing the loop's 'squaring loss'. This can, in some cases, improve the performance measure, although in all cases, the two-channel loop will still outperform the single-channel version.

Simon, M. K.

1981-01-01

406

Optimum Operation of Desalting Plants as a Supplemental Source of Safe Yield.  

National Technical Information Service (NTIS)

The report covers development of a computer program which would enable assessment of the optimum fashion in which desalting plants should be operated in conjunction with a single reservoir system. The program determines the optimum plant capacity to use a...

C. G. Clyde C. M. Wong J. J. Strobel S. Shiozawa W. H. Blood

1970-01-01

407

Performance evaluation of shape memory alloy/rubber-based isolation systems for seismic response mitigation of bridges  

NASA Astrophysics Data System (ADS)

Base isolation is an effective method of reducing seismic response of bridges during an earthquake. Rubber isolators are one of the most common types of base isolation systems. As an alternative to conventional rubber isolators such as high damping rubber bearing and lead rubber bearing, smart rubber bearing systems with shape memory alloys (SMAs) have been proposed in recent years. As a class of smart materials, shape memory alloys shows excellent re-centering and considerable damping capabilities which can be exploited to obtain an efficient seismic isolation system. This paper explores effectiveness of shape memory alloy/rubber-based isolation systems for protecting bridges against seismic loads by performing a sensitivity analysis. The isolation system considered in this study consists of a laminated rubber bearing which provides lateral flexibility while supplying high vertical load-carrying capacity and an auxiliary device made of multiple loops SMA wires. The SMA device offers additional energy dissipating and re-centering capability. A threespan continuous bridge is modeled with SMA/rubber-based isolation system. Numerical simulations of the bridge are conducted for various historical ground motions that are spectrally matched to a target design spectrum. The normalized yield strength, yield displacement and pre-stress level of the SMA device and ambient temperature are selected as parameters of the sensitivity study. The variation of seismic response of the bridge with considered parameters is assessed. The optimum values of the normalized yield strength and the yield displacement of the SMA device is found to be in the range of 0.20-0.25 and 40-50 mm, respectively. Also, the SMA/rubber-based isolation system is observed to be more effective when the SMA device is pre-stressed. In addition, it is found that ambient temperature considerably affects the performance of the bridge isolated by SMA/rubber-based isolators.

Ozbulut, Osman E.; Hurlebaus, Stefan

2010-03-01

408

Generation of programmable temporal pulse shape and applications in micromachining  

NASA Astrophysics Data System (ADS)

In this paper we presented a pulse shaping technique on regular solid-state lasers and the application in semiconductor micromachining. With a conventional Q-switched laser, all of the parameters can be adjusted over only limited ranges, especially the pulse width and pulse shape. However, some laser link processes using traditional laser pulses with pulse widths of a few nanoseconds to a few tens of nanoseconds tend to over-crater in thicker overlying passivation layers and thereby cause IC reliability problems. Use of a laser pulse with a special shape and a fast leading edge, such as tailored pulse, is one technique for controlling link processing. The pulse shaping technique is based on light-loop controlled optical modulation to shape conventional Q-switched solid-state lasers. One advantage of the pulse shaping technique is to provide a tailored pulse shape that can be programmed to have more than one amplitude value. Moreover, it has the capability of providing programmable tailored pulse shapes with discrete amplitude and time duration components. In addition, it provides fast rising and fall time of each pulse at fairly high repetition rate at 355nm with good beam quality. The regular-to-shaped efficiency is up to 50%. We conclude with a discussion of current results for laser processing of semiconductor memory link structures using programmable temporal pulse shapes. The processing experiments showed promising results with shaped pulse.

Peng, X.; Jordens, B.; Hooper, A.; Baird, B. W.; Ren, W.; Xu, L.; Sun, L.

2009-02-01

409

The interdependence of membrane shape and cellular signal processing.  

PubMed

Cellular membranes are constantly reshaped by vesicular fission and fusion as well as by interactions with the dynamic cytoskeleton. Signaling activity at membranes depends on their geometric parameters, such as surface area and curvature; these affect local concentration and thereby regulate the potency of molecular reactions. A membrane's shape is thus inextricably tied to information processing. Here, we review how a trinity of signaling, cytoskeletal dynamics, and membrane shape interact within a closed-loop causality that gives rise to an energy-consuming, self-organized system that changes shape to sense the extracellular environment. PMID:24630717

Schmick, Malte; Bastiaens, Philippe I H

2014-03-13

410

Digital phase-lock loop  

NASA Technical Reports Server (NTRS)

An improved digital phase lock loop incorporates several distinctive features that attain better performance at high loop gain and better phase accuracy. These features include: phase feedback to a number-controlled oscillator in addition to phase rate; analytical tracking of phase (both integer and fractional cycles); an amplitude-insensitive phase extractor; a more accurate method for extracting measured phase; a method for changing loop gain during a track without loss of lock; and a method for avoiding loss of sampled data during computation delay, while maintaining excellent tracking performance. The advantages of using phase and phase-rate feedback are demonstrated by comparing performance with that of rate-only feedback. Extraction of phase by the method of modeling provides accurate phase measurements even when the number-controlled oscillator phase is discontinuously updated.

Thomas, Jr., Jess B. (Inventor)

1991-01-01

411

Coronal loop detection and salient contour group extraction from solar images  

NASA Astrophysics Data System (ADS)

This dissertation addresses two different problems: 1) coronal loop detection from solar images: and 2) salient contour group extraction from cluttered images. In the first part, we propose two different solutions to the coronal loop detection problem. The first solution is a block-based coronal loop mining method that detects coronal loops from solar images by dividing the solar image into fixed sized blocks, labeling the blocks as "Loop" or "Non-Loop", extracting features from the labeled blocks, and finally training classifiers to generate learning models that can classify new image blocks. The block-based approach achieves 64% accuracy in 10-fold cross validation experiments. To improve the accuracy and scalability, we propose a contour-based coronal loop detection method that extracts contours from cluttered regions, then labels the contours as "Loop" and "Non-Loop", and extracts geometric features from the labeled contours. The contour-based approach achieves 85% accuracy in 10-fold cross validation experiments, which is a 20% increase compared to the block-based approach. In the second part, we propose a method to extract semi-elliptical open curves from cluttered regions. Our method consists of the following steps: obtaining individual smooth contours along with their saliency measures; then starting from the most salient contour, searching for possible grouping options for each contour; and continuing the grouping until an optimum solution is reached. Our work involved the design and development of a complete system for coronal loop mining in solar images, which required the formulation of new Gestalt perceptual rules and a systematic methodology to select and combine them in a fully automated judicious manner using machine learning techniques that eliminate the need to manually set various weight and threshold values to define an effective cost function. After finding salient contour groups, we close the gaps within the contours in each group and perform B-spline fitting to obtain smooth curves. Our methods were successfully applied on cluttered solar images from TRACE and STEREO/SECCHI to discern coronal loops. Aerial road images were also used to demonstrate the applicability of our grouping techniques to other contour-types in other real applications. Keywords: coronal loops, solar images, coronal loop detection, feature extraction, pattern recognition, classification, curve tracing, contour extraction, contour grouping, perceptual rules

Durak, Nurcan

412

Tracking performance and cycle slipping in the all-digital symbol synchronizer loop of the block 5 receiver  

NASA Technical Reports Server (NTRS)

Computer simulated noise performance of the symbol synchronizer loop (SSL) in the Block 5 receiver is compared with the theoretical noise performance. Good agreement is seen at the higher loop SNR's (SNR(sub L)'s), with gradual degradation as the SNR(sub L) is decreased. For the different cases simulated, cycle slipping is observed (within the simulation time of 10(exp 4) seconds) at SNR(sub L)'s below different thresholds, ranging from 6 to 8.5 dB, comparable to that of a classical phase-locked loop. An important point, however, is that to achieve the desired loop SNR above the seemingly low threshold to avoid cycle slipping, a large data-to-loop-noise power ratio, P(sub D)/(N(sub 0)B(sub L)), is necessary (at least 13 dB larger than the desired SNR(sub L) in the optimum case and larger otherwise). This is due to the large squaring loss (greater than or equal to 13 dB) inherent in the SSL. For the special case of symbol rates approximately equaling the loop update rate, a more accurate equivalent model accounting for an extra loop update period delay (characteristic of the SSL phase detector design) is derived. This model results in a more accurate estimation of the noise-equivalent bandwidth of the loop.

Aung, M.

1992-01-01

413

Reionization from cosmic string loops  

SciTech Connect

Loops formed from a cosmic string network at early times would act as seeds for early formation of halos, which would form galaxies and lead to early reionization. With reasonable guesses about astrophysical and string parameters, the cosmic string scale G{mu} must be no more than about 3x10{sup -8} to avoid conflict with the reionization redshift found by WMAP. The bound is much stronger for superstring models with a small string reconnection probability. For values near the bound, cosmic string loops may explain the discrepancy between the WMAP value and theoretical expectations.

Olum, Ken D.; Vilenkin, Alexander [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, Massachusetts 02155 (United States)

2006-09-15

414

Perturbations in loop quantum cosmology  

NASA Astrophysics Data System (ADS)

The era of precision cosmology has allowed us to accurately determine many important cosmological parameters, in particular via the CMB. Confronting Loop Quantum Cosmology with these observations provides us with a powerful test of the theory. For this to be possible, we need a detailed understanding of the generation and evolution of inhomogeneous perturbations during the early, quantum gravity phase of the universe. Here, we have described how Loop Quantum Cosmology provides a completion of the inflationary paradigm, that is consistent with the observed power spectra of the CMB.

Nelson, W.; Agullo, I.; Ashtekar, A.

2014-03-01

415

WFU Physics Demo Video: Miller Loop-de-Loop  

NSDL National Science Digital Library

This video demonstrates conservation of energy. A ball is released at the higher end of the track. Since energy is conserved, the ball will roll around the loop and off the other, lower end. It is part of a collection of typical lecture demonstration videos put together by the physics department at Wake Forest University.

G. Eric Matthews, Professor

2008-06-23

416

Optimum Design of High-Speed, Short Journal Bearings by Mathematical Programming  

Microsoft Academic Search

Generally, the selection of design variables in bearing design is done by a trial and error method using many design charts. However, it is not so easy to successfully select optimum design variables by such a method, and a considerable amount of working time and cost is needed to complete the optimum design of bearings. In this paper, an optimum

H. Hashimoto

1997-01-01

417

Optimum doping achieves high quantum yields in GaAs photoemitters  

NASA Technical Reports Server (NTRS)

Experimental data indicate that optimum doping exists. Measured quantum yield curves indicate optimum overall response is obtained in GaAs emitters with doping in high 10 to the 18th power per cu cm range. Doping for optimum response is not necessarily in this range.

Sonnenberg, H.

1971-01-01

418

Method for ascertaining optimum location for well stimulation and\\/or perforation  

Microsoft Academic Search

A method is disclosed for the in situ examination of earth formations penetrated by a borehole to ascertain the optimum location along the length thereof for instituting well stimulation operations or, where the well is cased, the optimum location for perforating the casing. The method utilizes natural gamma ray logging to determine the optimum locations with the natural gamma ray

W. H. Fertl; D. B. Vaello

1980-01-01

419

Method for ascertaining optimum location for well stimulation and\\/or perforation  

Microsoft Academic Search

A method is disclosed for the in situ examination of earth formations penetrated by a borehole to ascertain the optimum location along the length thereof for instituting well stimulation operations or, where the well is cased, the optimum location for perforating the casing. The method utilizes natural gamma ray logging to determine the optimum locations with the natural gamma ray

W. H. Fertl; D. B. Vaello

1983-01-01

420

Input shaped control of 3-dimensional maneuvers of flexible spacecraft  

NASA Technical Reports Server (NTRS)

This paper deals with the control of three dimensional rotational maneuvers of flexible spacecraft. A spacecraft with a spherical hub and six symmetric appendages is considered here as a model. The appendages are long and flexible leading to low frequency vibration under any control action. To provide a comprehensive treatment of input shaped controllers, both open loop and closed loop controllers are considered. The minimum-time bang-bang and the near-minimum-time controller, used in conjunction with the shaped input technique are studied. In addition, a combination of a Liapunov controller with the shaped input control technique is proposed to take advantage of the simple feedback control strategy and augment it with a technique that can eliminate the vibratory motion of the flexible appendages more efficiently.

Singh, T.; Vadali, S. R.

1992-01-01

421

Automated Coronal Loop Identification Using Digital Image Processing Techniques  

NASA Technical Reports Server (NTRS)

The results of a master thesis project on a study of computer algorithms for automatic identification of optical-thin, 3-dimensional solar coronal loop centers from extreme ultraviolet and X-ray 2-dimensional images will be presented. These center splines are proxies of associated magnetic field lines. The project is pattern recognition problems in which there are no unique shapes or edges and in which photon and detector noise heavily influence the images. The study explores extraction techniques using: (1) linear feature recognition of local patterns (related to the inertia-tensor concept), (2) parametric space via the Hough transform, and (3) topological adaptive contours (snakes) that constrains curvature and continuity as possible candidates for digital loop detection schemes. We have developed synthesized images for the coronal loops to test the various loop identification algorithms. Since the topology of these solar features is dominated by the magnetic field structure, a first-order magnetic field approximation using multiple dipoles provides a priori information in the identification process. Results from both synthesized and solar images will be presented.

Lee, Jong K.; Gary, G. Allen; Newman, Timothy S.

2003-01-01

422

Loop oscillations and an extreme ultraviolet wave associated with a micro-sigmoid eruption  

NASA Astrophysics Data System (ADS)

Taking advantage of the high temporal and spatial resolution observations of the Solar Dynamics Observatory, we present an extreme ultraviolet (EUV) wave associated with a micro-sigmoid eruption, which took place on 2012 October 4. The micro-sigmoid underwent a typical sigmoid-to-arcade evolution via tether-cutting reconnection, accompanied by a micro-flare, a filament eruption. The twin coronal dimmings at the footpoints of the sigmoid indicate the existence of the associated micro-coronal mass ejection that likely triggered a small-scale EUV wave. The wave onset was nearly simultaneous with the start of the eruption and the associated flare. The wave had a nearly circular front, and propagated at initial velocities of 300-360 km s-1. Because the sigmoid was located in the non-quiet region, the generated wave interacted with the ambient loops, and triggered transverse loop oscillations, resulting in many loop-shaped dimmings. Moreover, the interaction between the wave and one large loop led not only to the oscillation but also to the downward plasma flow along the loop, inducing loop footpoints to brighten. Another small loop was nearly intact after the wave passed. In some directions, the wave was refracted by the loops, and the refracted speeds increased, decreased, or vanished in different directions. All results provide evidence that the EUV wave was a fast-mode magnetohydrodynamic wave.

Zheng, R.-S.; Jiang, Y.-C.; Yang, J.-Y.; Hong, J.-C.; Bi, Y.; Yang, B.; Yang, D.

2013-05-01

423

Combining thermodynamic principles with Preisach models for superelastic shape memory alloy wires  

Microsoft Academic Search

We present a simple model for simulating the response of a superelastic shape memory alloy wire based on the thermodynamics of irreversible processes, which can simulate the full thermomechanical response including internal hysteresis loops, at different temperatures, with minimal data input. The key idea is to separate the dissipative response and the elastic response of shape memory alloys using a

S. Doraiswamy; A. Rao; A R Srinivasa

2011-01-01

424

Changes in lung tumor shape during respiration  

NASA Astrophysics Data System (ADS)

Evidence that some lung tumors change shape during respiration is derived from respiratory gated CT data by statistical shape modeling and image manipulation. Some tumors behave as rigid objects while others show systematic shape changes. Two views of lung motion are presented to allow analysis of the results. In the first, lung motion is viewed as a wave motion in which inertial effects arising from mass are present and in the second it is a quasistatic motion in which the mass of the lung tissues is neglected. In the first scenario, the extremes of tumor compression and expansion are expected to correlate with maximum upward and downward velocity of the tumor, respectively. In the second, they should occur at end exhale and end inhale, respectively. An observed correlation between tumor strain and tumor velocity provides more support for the first view of lung motion and may explain why previous attempts at observing tumor shape changes during respiration have largely failed. The implications for the optimum gating of radiation therapy are discussed.

Kyriakou, E.; McKenzie, D. R.

2012-02-01

425

Optimum Actuator Selection with a Genetic Algorithm for Aircraft Control  

NASA Technical Reports Server (NTRS)

The placement of actuators on a wing determines the control effectiveness of the airplane. One approach to placement maximizes the moments about the pitch, roll, and yaw axes, while minimizing the coupling. For example, the desired actuators produce a pure roll moment without at the same time causing much pitch or yaw. For a typical wing, there is a large set of candidate locations for placing actuators, resulting in a substantially larger number of combinations to examine in order to find an optimum placement satisfying the mission requirements and mission constraints. A genetic algorithm has been developed for finding the best placement for four actuators to produce an uncoupled pitch moment. The genetic algorithm has been extended to find the minimum number of actuators required to provide uncoupled pitch, roll, and yaw control. A simplified, untapered, unswept wing is the model for each application.

Rogers, James L.

2004-01-01

426

Optimum detection of tones transmitted by a spacecraft  

NASA Technical Reports Server (NTRS)

The performance of a scheme proposed for automated routine monitoring of deep-space missions is presented. The scheme uses four different tones (sinusoids) transmitted from the spacecraft (S/C) to a ground station with the positive identification of each of them used to indicate different states of the S/C. Performance is measured in terms of detection probability versus false alarm probability with detection signal-to-noise ratio as a parameter. The cases where the phase of the received tone is unknown and where both the phase and frequency of the received tone are unknown are treated separately. The decision rules proposed for detecting the tones are formulated from average-likelihood ratio and maximum-likelihood ratio tests, the former resulting in optimum receiver structures.

Simon, M. K.; Shihabi, M. M.; Moon, T.

1995-01-01

427

A Decision Support System for Optimum Use of Fertilizers  

SciTech Connect

The Decision Support System for Agriculture (DSS4Ag) is an expert system being developed by the Site-Specific Technologies for Agriculture (SST4Ag) precision farming research project at the INEEL. DSS4Ag uses state-of-the-art artificial intelligence and computer science technologies to make spatially variable, site-specific, economically optimum decisions on fertilizer use. The DSS4Ag has an open architecture that allows for external input and addition of new requirements and integrates its results with existing agricultural systems' infrastructures. The DSS4Ag reflects a paradigm shift in the information revolution in agriculture that is precision farming. We depict this information revolution in agriculture as an historic trend in the agricultural decision-making process.

R. L. Hoskinson; J. R. Hess; R. K. Fink

1999-07-01

428

A Decision Support System for Optimum Use of Fertilizers  

SciTech Connect

The Decision Support System for Agriculture (DSS4Ag) is an expert system being developed by the Site-Specific Technologies for Agriculture (SST4Ag) precision farming research project at the INEEL. DSS4Ag uses state-of-the-art artificial intelligence and computer science technologies to make spatially variable, site-specific, economically optimum decisions on fertilizer use. The DSS4Ag has an open architecture that allows for external input and addition of new requirements and integrates its results with existing agricultural systems’ infrastructures. The DSS4Ag reflects a paradigm shift in the information revolution in agriculture that is precision farming. We depict this information revolution in agriculture as an historic trend in the agricultural decision-making process.

Hoskinson, Reed Louis; Hess, John Richard; Fink, Raymond Keith

1999-07-01

429

Constraint-Based Local Search for Constrained Optimum Paths Problems  

NASA Astrophysics Data System (ADS)

Constrained Optimum Path (COP) problems arise in many real-life applications and are ubiquitous in communication networks. They have been traditionally approached by dedicated algorithms, which are often hard to extend with side constraints and to apply widely. This paper proposes a constraint-based local search (CBLS) framework for COP applications, bringing the compositionality, reuse, and extensibility at the core of CBLS and CP systems. The modeling contribution is the ability to express compositional models for various COP applications at a high level of abstraction, while cleanly separating the model and the search procedure. The main technical contribution is a connected neighborhood based on rooted spanning trees to find high-quality solutions to COP problems. The framework, implemented in COMET, is applied to Resource Constrained Shortest Path (RCSP) problems (with and without side constraints) and to the edge-disjoint paths problem (EDP). Computational results show the potential significance of the approach.

Pham, Quang Dung; Deville, Yves; van Hentenryck, Pascal

430

Parametric Study of Water Rocket for Optimum Flight  

NASA Astrophysics Data System (ADS)

Parametric study is conducted to find the optimum condition of water rocket for long flight, provided that the tank volume is prescribed. The parameters considered in the present study are the initial air pressure, water volume fraction, empty rocket mass, launching angle and bottle diameter which significantly affect the flight performance of water rocket. First, we calculate the temporal changes in tank pressure, water and air issue speeds and thrust, on the basis of a simple physical model which has been experimentally validated. Then, this model is incorporated into the equation of motion to calculate the ballistic flight of water rocket with various parameter values. As a result, it is found that PET bottles in the market are one of the most suitable for use as the pressure tank of water rocket.

Ota, Takayuki; Umemura, Akira

431

Simpler Alternative to an Optimum FQPSK-B Viterbi Receiver  

NASA Technical Reports Server (NTRS)

A reduced-complexity alternative to an optimum FQPSK-B Viterbi receiver has been invented. As described, the reduction in complexity is achieved at the cost of only a small reduction in power performance [performance expressed in terms of a bit-energy-to-noise-energy ratio (Eb/N0) for a given bit-error rate (BER)]. The term "FQPSK-B" denotes a baseband-filtered version of Feher quadrature-phase-shift keying, which is a patented, bandwidth-efficient phase-modulation scheme named after its inventor. Heretofore, commercial FQPSK-B receivers have performed symbol-by-symbol detection, in each case using a detection filter (either the proprietary FQPSK-B filter for better BER performance, or a simple integrate-and-dump filter with degraded performance) and a sample-and-hold circuit.

Lee, Dennis; Simon, Marvin; Yan, Tsun-Yee

2003-01-01

432

Incorporating spatial criteria in optimum reserve network selection.  

PubMed Central

Considering the spatial location of sites that are to be selected for inclusion in a protected reserve network may be necessary to facilitate dispersal and long-term persistence of species in the selected sites. This paper presents an integer programming (IP) approach to the reserve network selection problem where spatial considerations based on intersite distances are taken into account when selecting reserve sites. The objective is to reduce the fragmentation of preserved sites and design a compact reserve network. Two IP formulations are developed which minimize the sum of pairwise distances and the maximum intersite distance between all sites in the reserve network, respectively, while representing all species under consideration. This approach is applied to a pond invertebrate dataset consisting of 131 sites containing 256 species in Oxfordshire, UK. The results show that significant reductions in reserve fragmentation can be achieved, compared with spatially unrestricted optimum reserve selection, at the expense of a small loss in reserve efficiency.

Onal, Hayri; Briers, Robert A

2002-01-01

433

Improving the robustness of nonadditive watermarks through optimum detection theory  

NASA Astrophysics Data System (ADS)

In this paper, a new watermarking system for copyright protection of digital images is presented. The method operates in the frequency domain, by embedding a pseudo-random sequence of real numbers in a selected set of DFT coefficients of the image. Moreover, the masking characteristics of the Human Visual System are exploited for watermark hiding and a synchronization pattern is introduced into the watermarked image to cope with geometrical attacks. By relying on statistical decision theory, a new decoding algorithm which is optimum for non-additive full-frame DFT watermarks is then derived. Experimental results highlight both the superiority of the novel detector scheme with respect to conventional correlation-based decoding, both the robustness of the overall system against a large set of attacks aiming at removing the watermark.

Piva, Alessandro; Barni, Mauro; Bartolini, Franco; Cappellini, Vito; De Rosa, Alessia

2000-05-01

434

Optimum detection of an optical image on a photoelectric surface  

NASA Technical Reports Server (NTRS)

The detection of an optical image in the presence of uniform background light is based on a likelihood ratio formed of the numbers of photoelectrons emitted from small elements of a photoelectric surface onto which the image is focused. When diffraction is negligible and the surface has unit quantum efficiency, this detector is equipollent with the optimum detector of the image forming light. Its performance is compared with that of the threshold detector and that of a detector basing its decisions on the total number of photoelectrons from a finite area of the image. The illuminance of the image is postulated to have a Gaussian spatial distribution. All three detectors exhibit nearly the same reliability.

Helstrom, C. W.; Wang, L.

1972-01-01

435

Generation and evoluation of near-optimum vertical flight profiles  

NASA Technical Reports Server (NTRS)

The overall objectives of this research effort have been to develop and evaluate algorithms and flight management concepts for minimization of fuel or direct operating costs. These concepts are to be used for flight planning or for on-board computation and steering of turbojet transport aircraft in the vertical path. Within this research context, a computer program, called OPTIM, has been developed to use these algorithms to generate near-optimum vertical reference profiles. OPTIM contains control options to examine effects of various flight constraints on cost performance. A companion program, called TRAGEN, was developed to simulate an aircraft flying along a given vertical reference profile. TRAGEN is used to verify OPTIM's output , to examine the effects of parameter value uncertainty (such as prevailing wind), and to compare cost performance of profiles generated by different techniques. This paper describes OPTIM and TRAGEN and presents examples of the programs utility.

Sorensen, J. A.

1983-01-01

436

Optimum dietary crude protein level for finishing Awassi lambs.  

PubMed

Awassi is a multi-purpose sheep breed. Awassi lambs being finished are usually offered an 18% crude protein (CP) diet. The growth rate of Awassi lambs is lower than other meat breeds. Therefore, this high content of dietary CP is questionable. The objective of this study was to estimate the optimum CP level for finishing Awassi lambs. Fifty male Awassi lambs (23.0+/-1.2kg) were fed five high concentrate isocaloric diets (10 lambs per diet) that contained 10, 12, 14, 16, and 18% CP in a totally mixed diets for 9 weeks using a completely randomized design. Lambs were fed twice daily, and feed offered and feed refusals recorded for each feeding. Individual lamb intakes were calculated using daily feed offered and feed refused averaged over the interval of the experiment. Digestibility estimates were measured by total fecal collection. Lambs fed diets that contained 10, 12, and 14% CP gained less weight than those fed the 16 and 18% CP diets (P<0.05). Dry matter and CP intakes increased (P<0.05) with increasing levels of dietary CP. No difference (P>0.10) was observed in feed-to-gain ratio between diets except for the diet that contained 10% CP (P<0.05) which had a lower ratio. Organic matter and CP digestibility were lowest in lambs fed the 10% CP diet. Results suggest that the optimum CP concentration is 16% and that any increase above this level will not result in any improvement in production. PMID:11163714

Haddad, S G.; Nasr, R E.; Muwalla, M M.

2001-01-01

437

Closed Loop Knowledge System (CLKS)  

Microsoft Academic Search

This paper will provide information about the benefits of the closed loop knowledge system (CLKS). CLKS is based on a robust warehouse-based data repository and support tools where data access, storage and predictive data mining exploitation can be obtained from a web interface which will enable better decision support for war fighters. Knowledge engineering and analysis of the data required

S. Head

2008-01-01

438

Closed loop pulsating heat pipes  

Microsoft Academic Search

Closed loop pulsating heat pipes (CLPHPs) are complex heat transfer devices having a strong thermo-hydrodynamic coupling governing the thermal performance. In this paper, a wide range of pulsating heat pipes is experimentally studied thereby providing vital information on the parameter dependency of their thermal performance. The influence characterization has been done for the variation of internal diameter, number of turns,

Piyanun Charoensawan; Sameer Khandekar; Manfred Groll; Pradit Terdtoon

2003-01-01

439

Loop quantum cosmology and inhomogeneities  

Microsoft Academic Search

Inhomogeneities are introduced in loop quantum cosmology using regular lattice states, with a kinematical arena similar to that in homogeneous models considered earlier. The framework is intended to encapsulate crucial features of background independent quantizations in a setting accessible to explicit calculations of perturbations on a cosmological background. It is used here only for qualitative insights but can be extended

Martin Bojowald

2006-01-01

440

OUTER LOOP LANDFILL CASE STUDY  

EPA Science Inventory

This presentation will describe the interim data reaulting from a CRADA between USEPA and Waste Management, Inc. at the outer Loop Landfill Bioreactor research project located in Louisville, KY. Recently updated data will be presented covering landfill solids, gas being collecte...

441

Optimum Systems of Heat Dissipation by Radiation (Survey).  

National Technical Information Service (NTIS)

The article discusses available data on various optimal systems of evacuating heat energy by radiation. A radiating system with fins of optimal shape is considered first, together with the problem of minimizing the weight of the system. The influence of t...

G. L. Grodzovskii Y. G. Zhulev

1969-01-01

442

Noncontact guide system for traveling elastic steel plates: vibration control performance for different guideway shapes  

NASA Astrophysics Data System (ADS)

We have developed a noncontact guide system for a high-speed traveling elastic steel plate in which electromagnetic forces are applied by actuators at the edges of the plate to control its position. Recently, we have been examining a noncontact guide system, in which one of the loops of a belt-shaped thin steel plate is supported by a pulley, and another loop is guided without contact using electromagnets. It was confirmed experimentally that the loop shape of the thin steel plate changes with increasing traveling speed when no control is carried out. In this study, a basic examination of the technique for forming a guideway using electromagnets, in which the change in the uncontrolled loop shape is considered, was carried out. By comparing the results for guideways with several different shapes, the effect of the guideway shape on the vibration suppression performance of the steel plate was discussed experimentally. As a result, it was confirmed that the vibration suppression performance of the steel plate can be improved by adjusting the shape of the noncontact guide system that uses electromagnets to conform with that of the loop of the uncontrolled steel plate.

Kumagai, Hiroaki; Oshinoya, Yasuo; Ishibashi, Kazuhisa; Kasuya, Hirakazu

2007-12-01

443

Study of optimum nozzle exit position (NXP) in a steam ejector refrigeration system  

NASA Astrophysics Data System (ADS)

A steam ejector refrigeration system with a movable primary nozzle was developed to study the optimum nozzle exit position (NXP) in the ejector system. Three nozzles and two diffusers were fabricated to investigate the nozzle and diffuser effect on the optimum NXP. Experimental results show that an optimum NXP exists for an ejector system. In addition, the effects of boiler temperature and evaporator temperature on the system coefficient of performance (COP) were studied. The results indicate that the optimum NXP is not related to the operating temperature and the nozzle dimension and diffuser size. The investigation provides a better understanding of optimum NXP in a steam ejector refrigeration system.

Dong, Jingming; Ma, H. B.

2013-07-01

444

Loop quantum gravity without the Hamiltonian constraint  

NASA Astrophysics Data System (ADS)

We show that under certain technical assumptions, including the existence of a constant mean curvature (CMC) slice and strict positivity of the scalar field, general relativity conformally coupled to a scalar field can be quantized on a partially reduced phase space, meaning reduced only with respect to the Hamiltonian constraint and a proper gauge fixing. More precisely, we introduce, in close analogy to shape dynamics, the generator of a local conformal transformation acting on both, the metric and the scalar field, which coincides with the CMC gauge condition. A new metric, which is invariant under this transformation, is constructed and used to define connection variables which can be quantized by standard loop quantum gravity methods. Since this connection is invariant under the local conformal transformation, the generator of which is shown to be a good gauge fixing for the Hamiltonian constraint, the Dirac bracket associated with implementing these constraints coincides with the Poisson bracket for the connection. Thus, the well developed kinematical quantization techniques for loop quantum gravity are available, while the Hamiltonian constraint has been solved (more precisely, gauge fixed) classically. The physical interpretation of this system is that of general relativity on a fixed spatial CMC slice, the associated ‘time’ of which is given by the CMC. While it is hard to address dynamical problems in this framework (due to the complicated ‘time’ function), it seems, due to good accessibility properties of the CMC gauge, to be well suited for problems such as the computation of black hole entropy, where actual physical states can be counted and the dynamics is only of indirect importance. The corresponding calculation yields the surprising result that the usual prescription of fixing the Barbero-Immirzi parameter ? to a constant value in order to obtain the well-known formula S = a(?)A/(4G) does not work for the black holes under consideration, while a recently proposed prescription involving an analytic continuation of ? to the case of a self-dual space-time connection yields the correct result. Also, the interpretation of the geometric operators gets an interesting twist, which exemplifies the deep relationship between observables and the choice of a time function and has consequences for loop quantum cosmology.

Bodendorfer, N.; Stottmeister, A.; Thurn, A.

2013-04-01

445

Learning Deformable Shape Manifolds  

PubMed Central

We propose an approach to shape detection of highly deformable shapes in images via manifold learning with regression. Our method does not require shape key points be defined at high contrast image regions, nor do we need an initial estimate of the shape. We only require sufficient representative training data and a rough initial estimate of the object position and scale. We demonstrate the method for face shape learning, and provide a comparison to nonlinear Active Appearance Model. Our method is extremely accurate, to nearly pixel precision and is capable of accurately detecting the shape of faces undergoing extreme expression changes. The technique is robust to occlusions such as glasses and gives reasonable results for extremely degraded image resolutions.

Rivera, Samuel; Martinez, Aleix

2011-01-01

446

Similar-Shape Retrieval in Shape Data Management  

Microsoft Academic Search

Addresses the problem of similar-shape retrieval, where shapes or images in a shape database that satisfy specified shape-similarity constraints with respect to the query shape or image must be retrieved from the database. In its simplest form, the similar-shape retrieval problem can be stated as, “retrieve or select all shapes or images that are visually similar to the query shape

Rajiv Mehrotra; James E. Gary

1995-01-01

447

Decentralized control of sound radiation using iterative loop recovery.  

PubMed

A decentralized model-based control strategy is designed to reduce low-frequency sound radiation from periodically stiffened panels. While decentralized control systems tend to be scalable, performance can be limited due to modeling error introduced by the unmodeled interaction between neighboring control units. Since bounds on modeling error are not known in advance, it is difficult to ensure the decentralized control system will be robust without making the controller overly conservative. Therefore an iterative approach is suggested, which utilizes frequency-shaped loop recovery. The approach accounts for modeling error introduced by neighboring control loops, requires no communication between subsystems, and is relatively simple. The control strategy is evaluated numerically using a model of a stiffened aluminum panel that is representative of the sidewall of an aircraft. Simulations demonstrate that the iterative approach can achieve significant reductions in radiated sound power from the stiffened panel without destabilizing neighboring control units. PMID:20968346

Schiller, Noah H; Cabell, Randolph H; Fuller, Chris R

2010-10-01

448

Decentralized Control of Sound Radiation Using Iterative Loop Recovery  

NASA Technical Reports Server (NTRS)

A decentralized model-based control strategy is designed to reduce low-frequency sound radiation from periodically stiffened panels. While decentralized control systems tend to be scalable, performance can be limited due to modeling error introduced by the unmodeled interaction between neighboring control units. Since bounds on modeling error are not known in advance, it is difficult to ensure the decentralized control system will be robust without making the controller overly conservative. Therefore an iterative approach is suggested, which utilizes frequency-shaped loop recovery. The approach accounts for modeling error introduced by neighboring control loops, requires no communication between subsystems, and is relatively simple. The control strategy is evaluated numerically using a model of a stiffened aluminum panel that is representative of the sidewall of an aircraft. Simulations demonstrate that the iterative approach can achieve significant reductions in radiated sound power from the stiffened panel without destabilizing neighboring control units.

Schiller, Noah H.; Cabell, Randolph H.; Fuller, Chris R.

2009-01-01

449

Matching with Shape Contexts  

Microsoft Academic Search

We present a novel approach to measuring similarity between shapes and exploit it for object recognition. In our framework,\\u000a the measurement of similarity is preceded by (1) solving for correspondences between points on the two shapes, and (2) using\\u000a the correspondences to estimate an aligning transform. In order to solve the correspondence problem, we attach a descriptor,\\u000a the shape context,

Serge Belongie; Greg Mori; Jitendra Malik

450

Shape-Memory Polymers  

Microsoft Academic Search

Material scientists predict a prominent role in the future for self-repairing and intelligent materials. Throughout the last few years, this concept has found growing interest as a result of the rise of a new class of polymers. These so- called shape-memory polymers by far surpass well-known metallic shape- memory alloys in their shape-memory properties. As a consequence of the relatively

Andreas Lendlein; Steffen Kelch

2002-01-01

451

Shape preserving spline interpolation  

NASA Technical Reports Server (NTRS)

A rational spline solution to the problem of shape preserving interpolation is discussed. The rational spline is represented in terms of first derivative values at the knots and provides an alternative to the spline-under-tension. The idea of making the shape control parameters dependent on the first derivative unknowns is then explored. The monotonic or convex shape of the interpolation data can then be preserved automatically through the solution of the resulting non-linear consistency equations of the spline.

Gregory, J. A.

1985-01-01

452

Shapes of the proton  

NASA Astrophysics Data System (ADS)

A model proton wave function, constructed using Poincaré invariance and constrained by recent electromagnetic form factor data, is used to study the shape of the proton. Spin-dependent quark densities are defined as matrix elements of density operators in proton states of definite polarization, and shown to have an infinite variety of nonspherical shapes. For high momentum quarks with spin parallel to that of the proton, the shape resembles that of a peanut, but for quarks with antiparallel spin the shape is that of a bagel.

Miller, Gerald A.

2003-08-01

453

Visualization of shape motions in shape space.  

PubMed

Analysis of dynamic object deformations such as cardiac motion is of great importance, especially when there is a necessity to visualize and compare the deformation behavior across subjects. However, there is a lack of effective techniques for comparative visualization and assessment of a collection of motion data due to its 4-dimensional nature, i.e., timely varying three-dimensional shapes. From the geometric point of view, the motion change can be considered as a function defined on the 2D manifold of the surface. This paper presents a novel classification and visualization method based on a medial surface shape space, in which two novel shape descriptors are defined, for discriminating normal and abnormal human heart deformations as well as localizing the abnormal motion regions. In our medial surface shape space, the geodesic distance connecting two points in the space measures the similarity between their corresponding medial surfaces, which can quantify the similarity and disparity of the 3D heart motions. Furthermore, the novel descriptors can effectively localize the inconsistently deforming myopathic regions on the left ventricle. An easy visualization of heart motion sequences on the projected space allows users to distinguish the deformation differences. Our experimental results on both synthetic and real imaging data show that this method can automatically classify the healthy and myopathic subjects and accurately detect myopathic regions on the left ventricle, which outperforms other conventional cardiac diagnostic methods. PMID:24051831

Taimouri, Vahid; Hua, Jing

2013-12-01

454

Study of loop?loop and loop?edge dislocation interactions in bcc iron  

NASA Astrophysics Data System (ADS)

Recent theoretical calculations and atomistic computer simulations have shown that one-dimensional glissile clusters of self-interstitial atoms (SIAs) play an important role in the evolution of microstructure in metals and alloys under cascade damage conditions. Recently, it has been proposed that the evolution of heterogeneities such as dislocation decoration and rafts has serious impacts on the mechanical properties on neutron-irradiated metals. In the present work, atomic-scale computer modelling (ASCM) has been applied to study the mechanisms for the formation of such microstructure in bcc iron. It is shown that glissile clusters with parallel Burgers vectors interact strongly and can form extended immobile complexes, i.e., rafts. Similar attractive interaction exists between dislocation loops and an edge dislocation. These two mechanisms may be responsible for the formation of extended complexes of dislocation loops below the extra half-plane of edge dislocations. The interaction energies between loops and between an edge dislocation and loops has been calculated as a function of distance using ASCM and the results for long-range interactions are in good agreement with the results of isotropic elasticity calculations.

Osetsky, Yu. N.; Bacon, D. J.; Gao, F.; Serra, A.; Singh, B. N.

2000-12-01

455

Charge-pump phase-lock loops  

NASA Astrophysics Data System (ADS)

A basic charge-pump model is developed and the loop transfer function is derived based on the assumption of small error (linearized loop) and narrow bandwidth as compared to input frequency (continuous-time approximation). With reference to second order phase-lock loops (PLL), it is shown that Type-II operation is obtainable even with a passive loop filter, which is a particular benefit associated with charge pumps. Root-locus plots are given for third-order loops to aid design efforts. Finally, results of a nonlinear, discrete state-variable analysis are presented for the second-order loop. It is shown that transient settling times of wide-band loops obtained by discrete-time analysis are similar to the scaled settling times of narrow loops analyzed on the ordinary continuous-time basis.

Gardner, F. M.

1980-11-01

456

Subscriber loop economics: defining fiber's competitive edge  

NASA Astrophysics Data System (ADS)

Loop economics (capital, operating cost, revenues, and present worth) is not well known for any loop technology, hampering deployment of new loop technologies. Local Exchange Carriers (LECs) must establish a base economic case for copper since the LECs have generally required fiber to be deployed when 'cost competitive with copper for POTS.' However, LEC management information systems do not capture copper costs in a format useful to loop planners. Results of one detailed analysis of loop economics are presented, showing loop density as key cost driver. Work in progress suggests how fiber in the loop (FITL) can be compared to copper's POTS cost, revenue and value structures. Using different revenue streams due to fiber's service enhancements, present worth analysis will demonstrate the range of loop densities that fiber may have an advantage in today.

Tumolillo, Allan M.

1993-02-01

457

Evolution in a Braided Loop Ensemble  

NASA Video Gallery

This braided loop has several loops near the 'base' that appear to be unwinding with significant apparent outflow. This is evidence of untwisting, and the braided structure also seeming to unwind w...

458

Noise Performance Of A Digital Tanlock Loop  

NASA Technical Reports Server (NTRS)

Slight improvement over sinusoidal phase-lock loop achieved. Report discusses theoretical studies and numerical simulations of performance of digital tangent phase-lock loop (DTL), in presence of noise.

Hurd, W. J.; Pomalaza-Raez, C. A.

1988-01-01

459

Introduction of thermal activation in forward modeling of hysteresis loops for single-domain magnetic particles and implications for the interpretation of the Day diagram  

Microsoft Academic Search

Synthetic hysteresis loops were generated by numerically solving the classical Stoner-Wohlfarth model and a thermally activated Stoner-Wohlfarth model for a set of randomly oriented magnetic grains. Although computationally intensive this method allows forward modeling of hysteresis loops of single-domain (SD) and viscous grains. In the classic Stoner-Wohlfarth model the shape of the modeled loops can be modified by changing the

Luca Lanci; Dennis V. Kent

2003-01-01

460

Fragmentation of cosmic-string loops  

NASA Technical Reports Server (NTRS)

The fragmentation of cosmic string loops is discussed, and the results of a simulation of this process are presented. The simulation can evolve any of a large class of loops essentially exactly, including allowing fragments that collide to join together. Such reconnection enhances the production of small fragments, but not drastically. With or without reconnections, the fragmentation process produces a collection of nonself-intersecting loops whose typical length is on the order of the persistence length of the initial loop.

York, Thomas

1989-01-01

461

Identification of optimum scopes of environmental factors for snails using spatial analysis techniques in Dongting Lake Region, China  

PubMed Central

Background Owing to the harmfulness and seriousness of Schistosomiasis japonica in China, the control and prevention of S. japonica transmission are imperative. As the unique intermediate host of this disease, Oncomelania hupensis plays an important role in the transmission. It has been reported that the snail population in Qiangliang Lake district, Dongting Lake Region has been naturally declining and is slowly becoming extinct. Considering the changes of environmental factors that may cause this phenomenon, we try to explore the relationship between circumstance elements and snails, and then search for the possible optimum scopes of environmental factors for snails. Methods Moisture content of soil, pH, temperature of soil and elevation were collected by corresponding apparatus in the study sites. The LISA statistic and GWR model were used to analyze the association between factors and mean snail density, and the values in high-high clustered areas and low-low clustered areas were extracted to find out the possible optimum ranges of these elements for snails. Results A total of 8,589 snail specimens were collected from 397 sampling sites in the study field. Besides the mean snail density, three environmental factors including water content, pH and temperature had high spatial autocorrelation. The spatial clustering suggested that the possible optimum scopes of moisture content, pH, temperature of the soil and elevation were 58.70 to 68.93%, 6.80 to 7.80, 22.73 to 24.23°C and 23.50 to 25.97 m, respectively. Moreover, the GWR model showed that the possible optimum ranges of these four factors were 36.58 to 61.08%, 6.541 to 6.89, 24.30 to 25.70°C and 23.50 to 29.44 m, respectively. Conclusion The results indicated the association between snails and environmental factors was not linear but U-shaped. Considering the results of two analysis methods, the possible optimum scopes of moisture content, pH, temperature of the soil and elevation were 58.70% to 68.93%, 6.6 to 7.0, 22.73°C to 24.23°C, and 23.5 m to 26.0 m, respectively. The findings in this research will help in making an effective strategy to control snails and provide a method to analyze other factors.

2014-01-01

462

Thermomechanical modeling of polycrystalline SMAs under cyclic loading, Part IV: modeling of minor hysteresis loops  

Microsoft Academic Search

A thermomechanical model for the hysteretic response of Shape Memory Alloys (SMAs) is proposed in this paper by expanding a previous model developed by Bo and Lagoudas (Z. Bo, D.C. Lagoudas, International Journal of Engineering Science, accepted) to include minor hysteresis loops. The constitutive model for SMAs previously developed by Bo and Lagoudas is reviewed first, and a simplification for

Zhonghe Bo; Dimitris C. Lagoudas

1999-01-01

463

Coming Full Circle with Boyd's OODA Loop Ideas: An Analysis of Innovation Diffusion and Evolution.  

National Technical Information Service (NTIS)

The Observe-Orient-Decide-Act (OODA) Loop ideas of Air Force Colonel John Boyd have impacted the Department of Defense (DoD), influenced military thought, paved the way for operational change, and helped to shape fighting doctrines. A wide variety of OODA...

W. S. Angerman

2004-01-01

464

Frequency Selective Reflectarray Using Crossed-Dipole Elements With Square Loops for Wireless Communication Applications  

Microsoft Academic Search

A new frequency selective reflectarray (FSR) com- prising a crossed-dipole array and a frequency selective surface (FSS) of square loops printed on both sides of a dielectric substrate is presented for wireless communication applications. The reflec- tarray functions as a reflector, and generates the desired reflected beam shape while steering the primary wave source in the desired direction. Moreover, the

Long Li; Qiang Chen; Qiaowei Yuan; Kunio Sawaya; Tamami Maruyama; Tatsuo Furuno; Shinji Uebayashi

2011-01-01

465

Rotating String Shapes  

NSDL National Science Digital Library

In this group activity, learners make multi-sided polygons with string. Learners slide a long piece of string through their fingers to make different kinds of triangles (isosceles, right, equilateral, and scalene) and quadrilaterals, including concave and convex shapes. Learners also draw the shapes from different points of view to explore congruency.

Exploratorium

2010-01-01

466

Shape Memory Alloys  

Microsoft Academic Search

This special issue on shape memory alloys (SMA) is an encore to a special issue on the same topic edited by us six years ago (Smart Mater. Struct.9 (5) October 2000). A total of 19 papers is offered in this issue, organized into the three broad categories of modeling, characterization and applications. In addition to thermally activated shape memory alloys,

Abhijit Bhattacharyya; Dimitris C Lagoudas

2007-01-01

467

Pan Balance-Shapes  

NSDL National Science Digital Library

This Java applet allows children to explore a balancing tool and thus build their algebraic thinking about equivalency. By placing shapes on each side of the balance and finding equivalent sets of weights, students discover the weight of each shape in one of six built-in sets or a random set.

2011-01-01

468

Axial Representations of Shape.  

National Technical Information Service (NTIS)

Classes of 'ribbonlike' planar shapes can be defined by specifying an arc, called the spine or axis, and a geometric figure such as a disk or line segment, called the generator, that 'sweeps out' the shape by moving along the spine, changing size as it mo...

A. Rosenfeld

1984-01-01

469

3D Shape Similarity.  

National Technical Information Service (NTIS)

We study the 3D shape similarity between closed surfaces. We represent a curved or polyhedral 3D object of genus zero using a mesh representation that has nearly uniform distribution with known connectivity among mesh nodes. We define a shape similarity m...

H. Y. Shum M. Hebert K. Ikeuchi

1995-01-01

470

Pan Balance - Shapes  

NSDL National Science Digital Library

This resource provides a virtual manipulative pan balance to explore and practice equality with geometric shapes. Each shape is assigned a certain weight. The pictorial representation is entered in a table and the items on each side of the balance can be represented by an algebraic expression.

Mathematics, Illuminations N.

2009-03-04

471

Drifting buoy observations of a loop current anticyclonic eddy  

NASA Astrophysics Data System (ADS)

The Loop Current penetrated deep into the Gulf of Mexico in early 1989. After several eddy formation and reattachment cycles, a southwestward propagating anticyclonic eddy was formed during the summer. The Loop Current and subsequent eddy produced strong currents over widespread areas on the Louisiana continental slope, prompting a series of current measurement programs. Because of the lack of satellite infrared coverage in the Gulf of Mexico during the summer, the trajectories of 53 ARGOS tracked drifting buoys deployed in the Gulf of Mexico in 1989 were assembled to determine the synoptic history of the Loop Current and anticyclonic eddy during this event. Ten of the most critical summertime buoy trajectories are discussed here. In addition, the trajectories of three of the buoys simultaneously deployed at different radii in the eddy were chosen for analysis with a kinematic feature model. The model assumes the looping buoy motion is generated by an elliptical orbit around a translating eddy center. The buoy trajectories were used to determine time series of the feature model parameters, including eddy center, shape and circulation characteristics. The time series results indicate that the eddy actually propagated in a series of short sprints separated by longer stalls. During the sprints, the eddy propagated as an elliptical but otherwise symmetric solid body. During the stalls, significant asymmetries developed. The asymmetries are consistent with attachment to the Loop Current during the first stall, the effects of topographic Rossby wave dispersion during the second, and the effects of planetary Rossby wave dispersion during the third. The results provide both a framework for the interpretation of in situ observations and a detailed evolutionary history for numerical modelers.

Glenn, Scott M.; Ebbesmeyer, Curtis C.

1993-01-01

472

Determining the optimum beef longissimus muscle size for retail consumers.  

PubMed

Research was conducted in two phases to determine the optimum beef LM size for retail consumers. In Phase I, 50 USDA Choice beef carcass sides were selected at a commercial packing plant and assigned to five different categories (10 sides per category) based on LM size: 61 to 68 cm2 (A), 70 to 78 cm2 (B), 80 to 90 cm2 (C), 92 to 103 cm2 (D), and 105 to 119 cm2 (E). Ribeye rolls were retrieved from all carcass sides. Steaks (2.5-cm thick; 14 per ribeye roll) were cut as needed and transported in groups of 35 steaks (seven per LM size category) to a retail grocery store in Brookings, SD, where they were placed into a designated section of the retail meat case. Steaks were tallied every 4 h on weekdays and every 2 h on weekends and holidays to determine the number of monitoring periods that each steak remained in the retail case. Steaks that did not sell within an allotted time were removed from the case and termed "pulled." Time in case and percentage of steaks pulled from the case did not differ among LM size categories (P > 0.16). Quadratic regression indicated that larger LM steaks sold faster (P < 0.05) than average and small LM steaks. Steaks from rib locations 6 and 7 spent more (P < 0.05) time in the case than steaks from rib locations 8 through 12. Steaks from the 7th rib location were more (P < 0.05) likely to be pulled than steaks from the 8th through 12th rib locations. In Phase II, 15 USDA Choice ribeye rolls were selected from a commercial packing plant to represent two LM size categories: 80 to 90 cm2 (AVG; n = 5); and 105 to 119 cm2 (LARGE; n = 10) and cut into 2.5-cm-thick steaks. A portion of the LARGE steaks was subsequently cut in half (HALF). Four display steaks represented each treatment group in each of five random nth price auctions. Seventy-five people were recruited from the Brookings, SD area to participate in the auctions to determine their willingness to pay for the three different types of ribeye steak. Consumers were willing to pay a premium of 1.50 dollars/kg for LARGE ribeye steaks over AVG ribeye steaks (P < 0.05). Consumers discounted HALF ribeye steaks by 1.01 dollars/kg compared with AVG ribeye steaks (P < 0.05). In conclusion, no optimum LM size existed for beef retail consumers; however, a trend existed toward greater demand for larger LM sizes over smaller LM sizes. PMID:16230657

Sweeter, K K; Wulf, D M; Maddock, R J

2005-11-01

473

Looping: Adding Time, Strengthening Relationships. ERIC Digest.  

ERIC Educational Resources Information Center

"Looping" is an essentially simple concept: a teacher moves with his or her students to the next grade level, rather than sending them to another teacher at the end of the school year. This Digest explores the practitioners' perspectives on looping, the experience of European school systems, and research on looping. Practitioners report positive…

Bu