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1

Optimum Allocation of Two-Dimensional Shapes.  

National Technical Information Service (NTIS)

The optimum two-dimensional allocation problem consists in taking a two-dimensional resource and cutting it into a number of two-dimensional shapes in such a way that some objective function is optimized. The paper describes an investigation into methods ...

M. Adamowicz

1971-01-01

2

Quasi-Optimum Digital Phase-Locked Loops  

Microsoft Academic Search

Quasi-optimum digital phase-locked loops (DPLL) are derived utilizing nonlinear estimation theory. Nonlinear approximations are employed to yield realizable loop structures. Baseband equivalent loop gains are derived, which, under high signal-to-noise ratio conditions may be calculated off line. Additional simplifications are made that permit the application of the Kalman filter algorithms to determine the minimum mean-square error (MSE) loop filter. Consideration

D. Polk; S. Gupta

1973-01-01

3

Optimum shape construction of flexible manipulators with total weight constraint  

Microsoft Academic Search

This paper addresses the problem of optimum shape design of flexible manipulators that maximizes the fundamental frequency of vibration under a specified total weight constraint. Successive iteration schemes are developed to solve the unconstrained optimum shape design problem analytically using the variational approach, while nonlinear programming methods are used to solve the constrained optimum shape design problem numerically. In addition,

Fei-Yue Wang; Jeffrey L. Russell

1995-01-01

4

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

5

Optimum pulse shape for minimum spectral occupancy in FSK signals  

Microsoft Academic Search

The characteristics of a frequency shift keying (FSK) signal giving rise to maximum power within a prescribed frequency band are determined. The baseband pulse shape extends over any integer number of bit periods. An integral equation for the optimum pulse shape is derived and some simple properties of the solution are investigated. The equation has been solved for some values

M. Campanella; U. Lo Faso; G. Mamola

1984-01-01

6

Optimum pulse shapes for stimulated Raman adiabatic passage  

SciTech Connect

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. [Department of Physics, University of Oxford, Parks Road, OX1 3PU Oxford (United Kingdom); Department of Physics, Sofia University, James Bourchier 5 Boulevard, 1164 Sofia (Bulgaria); Kuhn, A. [Department of Physics, University of Oxford, Parks Road, OX1 3PU Oxford (United Kingdom); Vitanov, N. V. [Department of Physics, Sofia University, James Bourchier 5 Boulevard, 1164 Sofia (Bulgaria); Institute of Solid State Physics, Bulgarian Academy of Sciences, Tsarigradsko Chaussee 72, 1784 Sofia (Bulgaria)

2009-07-15

7

Optimum Pulse Shape Design for UWB Systems with Timing Jitter  

NASA Astrophysics Data System (ADS)

This paper proposes a novel technique in designing the optimum pulse shape for ultra wideband (UWB) systems under the presence of timing jitter. In the UWB systems, pulse transmission power and timing jitter tolerance are crucial keys to communications success. While there is a strong desire to maximize both of them, one must be traded off against the other. In the literature, much effort has been devoted to separately optimize each of them without considering the drawback to the other. In this paper, both factors are jointly considered. The proposed pulse attains the adequate power to survive the noise floor and at the same time provides good resistance to the timing jitter. The proposed pulse also meets the power spectral mask restriction as prescribed by the Federal Communications Commission (FCC) for indoor UWB systems. Simulation results confirm the advantages of the proposed pulse over other previously known UWB pulses. Parameters of the proposed optimization algorithm are also investigated in this paper.

Lee, Wilaiporn; Kunaruttanapruk, Suwich; Jitapunkul, Somchai

8

New technologies for advanced three-dimensional optimum shape design in aeronautics  

NASA Astrophysics Data System (ADS)

The analysis of complex flows around realistic aircraft geometries is becoming more and more predictive. In order to obtain this result, the complexity of flow analysis codes has been constantly increasing, involving more refined fluid models and sophisticated numerical methods. These codes can only run on top computers, exhausting their memory and CPU capabilities. It is, therefore, difficult to introduce best analysis codes in a shape optimization loop: most previous works in the optimum shape design field used only simplified analysis codes. Moreover, as the most popular optimization methods are the gradient-based ones, the more complex the flow solver, the more difficult it is to compute the sensitivity code. However, emerging technologies are contributing to make such an ambitious project, of including a state-of-the-art flow analysis code into an optimisation loop, feasible. Among those technologies, there are three important issues that this paper wishes to address: shape parametrization, automated differentiation and parallel computing. Shape parametrization allows faster optimization by reducing the number of design variable; in this work, it relies on a hierarchical multilevel approach. The sensitivity code can be obtained using automated differentiation. The automated approach is based on software manipulation tools, which allow the differentiation to be quick and the resulting differentiated code to be rather fast and reliable. In addition, the parallel algorithms implemented in this work allow the resulting optimization software to run on increasingly larger geometries. Copyright

Dervieux, Alain; Lanteri, Stéphane; Malé, Jean-Michel; Marco, Nathalie; Rostaing-Schmidt, Nicole; Stoufflet, Bruno

1999-05-01

9

Optimum Width for Loops as Determined by Model Studies.  

National Technical Information Service (NTIS)

The purpose of the research was to improve the reliability and extent of range of harbor defense detection equipments against surface craft, sneak craft, and swimmers. The report gives the results of an experiment, on models of magnetic indicator loops, d...

A. N. Smith

1964-01-01

10

Feedback Loops Shape Cellular Signals in Space and Time  

NSDL National Science Digital Library

This article discusses the study of feedback loops in biological systems. 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.

Onn Brandman (University of California-San Francisco and Howard Hughes Medical Institute;Department of Cellular and Molecular Pharmacology); Tobias Meyer (Stanford University Medical Center;Department of Chemical and Systems Biology)

2008-10-17

11

Preliminary studies on the optimum shape of dental bridges.  

PubMed

Several pre-existing anterior and posterior dental bridge models using Finite elements and the new ceramic material In-Ceram have been developed. The mechanical behaviour of these models has been compared with optimised profiles obtained from a newly developed evolutionary algorithm known as Evolutionary Structural Optimisation (ESO). The results show that the mechanical behaviour of the bridges was mainly restricted by the properties of the porcelain veneer and the design of the bridges themselves. For the case of the anterior bridge, it was found that there existed a specific thickness of veneer that minimised the maximum principal stress. This was related to peak stresses that occurred at the bridge surface. Peak stresses also occurred in the material interface between the In-Ceram and the veneer. These extreme stresses were attributed to the notch size and shape. For the case of the posterior bridge, it was concluded that the shape of the bottom of the Pontic tooth is crucial in reducing the magnitude of the maximum principal tensile stress. The ESO process produced bridge designs which have uniformly stressed bridge surfaces, and which also have significantly lower maximum principal tensile stresses compared to the pre-existing designs (up to 44%). PMID:11264862

Proos, K; Steven, G; Swain, M; Ironside, J

2000-01-01

12

Optimum Shape in Brick Masonry Arches Under Static And Dynamic Loads  

Microsoft Academic Search

The objective of this study is to determine brick masonry arches under dynamic and static loads. In this paper, considerable attention is given to arches, their importance, modeling stages, dynamic analysis, static analysis and arch optimization using ANSYS11 software. A multiple stage analysis framework was conducted for semicircular arch: 1- The study of optimum shape for semicircular arch on the

KAVEH KUMARCI; ARASH ZIAIE; MEHRAN KOOHIKAMALI; ARASH KYIOUMARSI

2008-01-01

13

Resonantly damped oscillations of elliptically shaped stratified emerging coronal loops  

NASA Astrophysics Data System (ADS)

The effects of both elliptical shape and stage of emergence of the coronal loop on the resonant absorption of standing kink oscillations are studied. To do so, a typical coronal loop is modeled as a zero-beta longitudinally stratified cylindrical magnetic flux tube. We developed the connection formulae for the resonant absorption of standing transversal oscillations of a coronal loop with an elliptical shape, at various stages of its emergence. Using the connection formulae, the dispersion relation is derived and solved numerically to obtain the frequencies and damping rates of the fundamental and first-overtone kink modes. Our numerical results show that both the elliptical shape and stage of emergence of the loop alter the frequencies and damping rates of the tube as well as the ratio of frequencies of the fundamental and its first-overtone modes. However, the ratio of the oscillation frequency to the damping rate is not affected by the tube shape and stage of its emergence and also is independent of the density stratification parameter.

Karami, K.; Amiri, S.; Bahari, K.; Ebrahimi, Z.

2013-09-01

14

Quantitative Evaluation of Closed-Loop-Shaped Cardiomyocyte Network by Using Ring-Shaped Electrode  

NASA Astrophysics Data System (ADS)

Re-entry of excitation in the heart is one of the abnormal phenomena that causes lethal arrhythmia and is thought to be induced by the looped structure of the excitation conduction pathway. To evaluate the geometrical pattern dependence of electrophysiological results, we fabricated three models of cardiomyocyte networks and compared their beating frequencies (BFs), amplitudes of a depolarization peak, and field potential durations (FPDs). The set of different closed-loop-shaped network models from 3 to 8 mm in length showed the same BFs, amplitudes, and FPDs independent of their loop lengths, whereas the BFs and FPDs of 60 ?m small clusters, and the FPDs of the 2 mm open-line-shaped network model were different from those of a closed-loop-shaped network model. These results indicate that the mm order larger size of clusters might create lower BFs, and the closed-loop-shaped model may generate longer FPDs. They also suggest the importance of spatial arrangement control of the cardoimyocyte community for reproducible measurement of electrophysiological properties of cardiomyocytes, especially control of the closed-loop formation, which might change the waveforms of FPDs depending on the difference in the geometry and conduction pathway of the cell network.

Nomura, Fumimasa; Kaneko, Tomoyuki; Hamada, Tomoyo; Hattori, Akihiro; Yasuda, Kenji

2012-06-01

15

Shape Optimum Design of Propeller Blade Operating in Low Reynolds Number Range  

Microsoft Academic Search

This study is concerned with a shape optimum design of a propeller blade operating in a low Reynolds number range, 1.0 2.0×105. The objective is to minimize the power-required under the constraints on the thrust and the angle of attack in terms of chord length and twist angle distributions where the power-required is evaluated by 3-D panel method. The profile

Nozomu Kogiso; Tomoyoshi Utsumi; Yoshisada Murotsu

2003-01-01

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

{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

18

Fields of a horizontal loop of arbitrary shape buried in a two-layer earth  

Microsoft Academic Search

Expressions have been derived for the magnetic field in air produced by a buried horizontal loop of arbitrary shape. Numerical results are presented for both circular and rectangular loops. Rectangular loops produce an azimuthal magnetic field component which is not present in the case of a circular loop. The results have application to source location in mine rescue techniques. In

James R. Wait; David A. Hill

1980-01-01

19

An improved qualitative shape analysis technique for automatic detection of valve stiction in flow control loops  

Microsoft Academic Search

Valve stiction is a frequent cause of loop performance deterioration and in recent literature many techniques have been proposed for its automatic detection. Yamashita [(2006). An automatic method for detection of valve stiction in process control loops. Control Engineering Practice, 14, 503–510] proposes a method based on qualitative shape analysis, which is very effective for flow control loops where the

Claudio Scali; Claudio Ghelardoni

2008-01-01

20

CACSD tools for loop gain-phase shaping design of SISO robust controllers  

Microsoft Academic Search

The steps in loop gain-phase shaping (LGPS) and a family of CAD tools that make LGPS a realistic design procedure are described. Several examples demonstrating the use of these tools and the performance advantages of LGPS over classical loop shaping and its derivatives are presented. It is reported that the LGPS approach uses phase information explicitly, providing an increased range

F. N. Bailey; C.-H. Hui

1989-01-01

21

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

22

A qualitative shape analysis formalism for monitoring control loop performance  

Microsoft Academic Search

Optimal performance of controllers and control loops is crucial for process economy, quality and safety in chemical plants. Industrial statistics show that often a significant percentage of them are performing sub-optimally at any given time. Effective real-time monitoring of control loops is a difficult task as there may be dozens of loops to monitor in a typical process. In addition,

R. Rengaswamy; T. Hägglund; V. Venkatasubramanian

2001-01-01

23

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

24

Gain-scheduling Control of Rotary Inverted Pendulum by Weight Optimization and H? Loop Shaping Procedure  

NASA Astrophysics Data System (ADS)

Gain-scheduling control is one of effective methods for plants whose dynamics changes significantly according to its operating point. A frozen parameter method is known to be a practical gain-scheduling controller synthesis, which interpolates the controllers designed at the prespecified (frozen) operating points according to the current operation point. Hyde et al. proposed a gain-scheduling control that H? loop shaping procedure is adopted as a controller synthesis at each operating point. H? loop shaping procedure is based on loop shaping of an open loop characteristic by frequency weights and is known to be effective for plants with bad condition number. However, weight selection satisfying control specifications is hard job for a designer. This paper describes the design of a suboptimal weight and a controller by means of algorithm that maximizes the robust stability margin and shapes the open loop characteristic into the desired shape at each operating point. Moreover, we formulate a weight optimization problem as a generalized eigenvalue minimization problem, which reduces the designer's burden of weight selection. Finally, we realize robust and high performance control system by scheduling both weights and controllers. The effectiveness of the proposed control system is verified in terms of the achieved robust stability margin and experimental time responses of a rotary inverted pendulum which involves strong nonlinear dynamics.

Yubai, Kazuhiro; Okuhara, Kazunori; Hirai, Junji

25

Optimum nanoparticles for electrocatalytic oxygen reduction: the size, shape and new design.  

PubMed

The electrocatalytic oxygen reduction reaction (ORR) on nanoparticles has attracted much attention in recent years for its significance in fuel cell applications. Here by combining density functional theory (DFT) calculations with the periodic continuum solvation model based on modified-Poisson-Boltzmann (CM-MPB) electrostatics, we analyzed the ORR activity on a set of differently sized Pt nanoparticles in order to identify the optimum particles for a better designed catalyst. We show that Pt nanoparticles of ?2 nm size have the highest ORR mass activity, which is attributed to the variation of the effective reaction sites on the exposed {111} facet at the electrochemical conditions. We propose a type of a new nanocatalyst for the electrocatalytic oxygen reduction based on the knowledge from large-scale first principles simulations on Pt nanoparticles. The new catalyst has inert metal Au as the frame for the Pt nanoparticle and exposed Pt{111} sites are the active site for oxygen reduction. Such an architecture can not only prevent the initial O corrosion at the edge sites but also significantly improve the activity. The theoretical work provides a promising new direction for the rational design of a stable and active ORR catalyst via nano-structure engineering. PMID:24077215

Wei, Guang-Feng; Liu, Zhi-Pan

2013-10-01

26

Lead and lag compensators with complex poles and zeros design formulas for modeling and loop shaping  

Microsoft Academic Search

Complex lead and lag compensators are new additions to the repertoire of compensator structures for loop shaping. This article facilitates the use of these compensators by providing explicit formulas that relate the parameters of the compensators to features of their frequency responses. Two examples illustrate the utility of these compensators for system modeling and controller design. While the examples involve

WILLIAM C. MESSNER; MARK D. BEDILLION; Lu Xia; DUANE C. KARNS

2007-01-01

27

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

NASA Astrophysics Data System (ADS)

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

28

Optimum Design of Forging Process Parameters and Preform Shape under Uncertainties  

NASA Astrophysics Data System (ADS)

Forging is a highly complex non-linear process that is vulnerable to various uncertainties, such as variations in billet geometry, die temperature, material properties, workpiece and forging equipment positional errors and process parameters. A combination of these uncertainties could induce heavy manufacturing losses through premature die failure, final part geometric distortion and production risk. Identifying the sources of uncertainties, quantifying and controlling them will reduce risk in the manufacturing environment, which will minimize the overall cost of production. In this paper, various uncertainties that affect forging tool life and preform design are identified, and their cumulative effect on the forging process is evaluated. Since the forging process simulation is computationally intensive, the response surface approach is used to reduce time by establishing a relationship between the system performance and the critical process design parameters. Variability in system performance due to randomness in the parameters is computed by applying Monte Carlo Simulations (MCS) on generated Response Surface Models (RSM). Finally, a Robust Methodology is developed to optimize forging process parameters and preform shape. The developed method is demonstrated by applying it to an axisymmetric H-cross section disk forging to improve the product quality and robustness.

Repalle, Jalaja; Grandhi, Ramana V.

2004-06-01

29

Partial Tuning of Dynamical Controllers by Data-Driven Loop-Shaping  

NASA Astrophysics Data System (ADS)

In this paper, a data-driven design method that gives a desirable loop-shape is proposed for a single input plant. This method is applicable to the tuning of a static feedback gain and also that of the output matrix of a dynamical controller by using a transient response of the plant. Constraints on the feedback gain are derived from the maximum sensitivity and complementary sensitivity conditions based on the unfalsified control idea. A solution is obtained by solving a linear matrix inequality, where the integral gain of the loop transfer function is maximized subject to the constraints. Usefulness is demonstrated by two numerical examples.

Saeki, Masami; Sugitani, Yosuke

30

Shape of an elastic loop strongly bent by surface tension: experiments and comparison with theory.  

PubMed

When a very flexible wire is dipped into a soapy solution, it collapses onto itself. We consider the regions of high curvature where the wire folds back onto itself, enclosing a capillary film. The shapes of these end loops are measured in experiments using soap films and compared to a known similarity solution. The sizes of these structures provide a simple and reliable way to measure surface tension. PMID:23005837

Mora, Serge; Phou, Ty; Fromental, Jean-Marc; Audoly, Basile; Pomeau, Yves

2012-08-30

31

Gain Scheduled PID Controller Design by Data-Driven Loop-Shaping Method  

NASA Astrophysics Data System (ADS)

In this paper, a gain scheduled PID control system is constructed for a nonlinear plant whose steady state changes by the setpoint change. Our data-driven loop shaping method is applied to the direct design of PID gains using the plant input output response measured at several setpoints. The reference input is used for the scheduling parameter. Usefulness of our method is shown by simulation for a Hammerstein model.

Saeki, Masami; Ogawa, Kyosuke

32

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

33

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

34

Optimum shape for buckling and post-buckling behavior of a laminated composite panel with I-type stiffeners  

Microsoft Academic Search

A shape optimization of stiffener was conducted to increase buckling load or failure load with stiffened laminated composite\\u000a panel of I-type under compression loading. Design variables are cap length, web length, and\\/or thickness under the constraint\\u000a of volume constancy. The objective function is buckling load and failure load of post-buckling based on Tsai-Hill theory using\\u000a ABAQLJS 5.8 for analysis and

Gwang-Rog Lee; Won-Ho Yang; Myung-Won Suh

2002-01-01

35

Loop-shaping H INFINITY -control of a 2DOF piezoelectric-stack actuated platform for nanoscale positioning  

Microsoft Academic Search

Piezoelectric-stack actuated platforms are utilized in many nanopositioning applications. Their performance is limited by their low-frequency resonance due to the mechanical construction as well as piezoelectric nonlinear effects. We propose a hybrid control scheme comprising a loop-shaping Hinfin controller and an inversion-based feedforward control scheme, capable of delivering accurate nanopositioning performance at relatively high speeds, upto 40 Hz. It is

Sumeet S. Aphale; Antoine Ferreira; S. O. Reza Moheimani

2009-01-01

36

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

37

A capillary-pumped loop (CPL) with microcone-shaped capillary structure for cooling electronic devices  

Microsoft Academic Search

A MEMS-based integrated capillary-pumped loop (CPL), which can be used for cooling electronic devices such as the CPU of a personal computer or notebook, was developed. The CPL consists of an evaporator and condenser both with the same size of 30 mm × 30 mm × 5.15 mm, which were fabricated using two layers of glass wafer and one layer

Jung-Yeul Jung; Hoo-Suk Oh; Dae Keun Lee; Kyong Bin Choi; Sang Keun Dong; Ho-Young Kwak

2008-01-01

38

Optimum Gyrators.  

National Technical Information Service (NTIS)

A model gyrator was designed and tested, and will prove useful in development of an optimum monolithic gyrator. Theoretical methods of broadbanding were developed, but their usefulness is integrated-circuit form is not yet clear. A new circuit for tempera...

P. R. Geffe

1969-01-01

39

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

40

Closed-loop phase stepping in a calibrated fiber-optic fringe projector for shape measurement  

NASA Astrophysics Data System (ADS)

Active homodyne feedback control can be used to stabilize an interferometer against unwanted phase drifts introduced by, for example, temperature gradients. The technique is commonly used in fiber-optic sensors to maintain the fiber at its most sensitive (quadrature) position. We describe an extension of the technique to introduce stabilized, pi/2-rad phase steps in a full-field interferometer. The technique was implemented in a single-mode, fiber-optic interference fringe projector used for shape measurement and can be easily applied to other fiber- or bulk-optic interferometers, for example, speckle pattern and holographic interferometers. Fresnel reflections from the distal fiber ends undergo a double pass in the fibers and interfere at the fourth port of a directional coupler. The interference intensity (and hence phase) is maintained at quadrature by feedback control to a phase modulator in one of the fiber arms. Stepping between quadrature positions (separated by pi rad for light undergoing a double pass) introduces stabilized phase steps in the projected fringes (separated by pi/2 rad for a single pass). A root-mean-square phase stability of 0.61 mrad in a 50-Hz bandwidth and phase step accuracy of 1.17 mrad were measured.

Moore, Andrew J.; McBride, Roy; Barton, James S.; Jones, Julian D. C.

2002-06-01

41

Mutagenic Probes of the Role of Serine 209 on the Cavity Shaping Loop of Human Monoamine Oxidase A  

PubMed Central

Summary Literature reports implicating human monoamine oxidase A (MAO A) in apoptotic processes report levels of MAO A protein that do not correlate with activity suggesting unknown mechanisms may be involved in regulation of catalytic function. Bioinformatic analysis suggests Ser209 as a possible phosphorylation site that may be relevant to catalytic function since it is adjacent to a six-residue loop termed the “cavity shaping loop” from structural data. To probe the functional role of this site, MAO A Ser209Ala and Ser209Glu mutants were created and investigated. In its membrane-bound form, the MAO A Ser209Glu phosphorylation mimic exhibits similar catalytic and inhibitor binding properties as wild-type MAO A. Solubilization in detergent solution and purification of the Ser209Glu mutant results in considerable decreases in these functional parameters. In contrast, the MAO A Ser209Ala mutant exhibits similar catalytic properties to those of wild-type enzyme when purified. Compared with purified wild-type and Ser209Ala MAO A proteins, the Ser209Glu MAO A mutant shows significant differences in covalent flavin fluorescence yield, circular dichroism spectra and thermal stability. These structural differences in the purified MAO A Ser209Glu mutant are not exhibited in QSAR patterns using a series of para-substituted benzylamine analogues which are similar to wild-type enzyme. These data suggest that serine 209 in MAO A does not appear to be the putative phosphorylation site for regulation of MAO A activity and demonstrate the membrane environment plays a significant role in stabilizing the structure of MAO A and its mutant forms.

Wang, Jin; Harris, Johnny; Mousseau, Darrell D.; Edmondson, Dale E.

2009-01-01

42

Effect of tensile and compressive stress on dynamic loop shapes and power losses of Fe-Si electrical steels  

NASA Astrophysics Data System (ADS)

Magnetic energy losses and hysteresis loops have been determined in Fe-Si non-oriented laminations as a function of the applied compressive and tensile stress, made to range between -50 and +50 MPa. The loss separation analysis has been carried out in association with hysteresis loop calculation by means of the Dynamic Preisach Model. The strong modifications to the hysteresis loop and area introduced in a specific way by compressive stresses can be correctly accounted for by modelling.

Lobue, M.; Basso, V.; Fiorillo, F.; Bertotti, G.

1999-05-01

43

Optimum Flapping Wing Motions of Dragonfly  

NASA Astrophysics Data System (ADS)

We studied the optimum flapping wing motions of a dragonfly (Anax parthenope julius) from hovering to cruising flight at various speeds, using a 3D Navier-Stokes code coupled with an optimization algorithm. The minimum necessary power curve and optimum flapping wing motions for the various flight velocities were determined using the optimization algorithm. The minimum power curve shows the typical U-shape. The optimum flapping wing motions were evaluated by comparison with experimental data. Examining the flow patterns showed that the large-scale flow separation around the wings is suppressed at these optimum conditions, except for very low flight speeds including hovering.

Kamisawa, Yuichi; Isogai, Koji

44

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

45

The kissing-loop T-shaped structure translational enhancer of pea enation mosaic virus can bind simultaneously to ribosomes and a 5' proximal hairpin.  

PubMed

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. PMID:23986599

Gao, Feng; Gulay, Suna P; Kasprzak, Wojciech; Dinman, Jonathan D; Shapiro, Bruce A; Simon, Anne E

2013-08-28

46

The optimum flat plate solar collector  

NASA Astrophysics Data System (ADS)

The solar fluid heater problem is formulated as an unsteady, two-dimensional conduction problem. Simplified to a steady, one-dimensional problem provides a direct formulation far more flexible than the formulation hitherto in use, without any loss of generality. This flexibility is used to determine the geometry of optimum collectors, and to determine the performance of fan-shaped ones. An optimum collector would have a uniform effectiveness along the fluid path and, hence, effect a required fluid temperature rise with the least possible area. A fan-shaped collector of about the same geometrical proportions is shown to be nearly as effective as the corresponding optimum collector. The performance of either shape is determined for certain conditions. It shows that for this case a saving of some 6 to 13 percent could be obtained in comparison with the corresonding usual 'parallel-tube' design.

Hassan, K.-E.

47

Canonically optimum threshold detection  

Microsoft Academic Search

A general canonical theory is developed for the systematic approximation of optimum, or Bayes, detection procedures in the critical limiting threshold mode of operation. The approximations to Bayes detectors introduced here are called locally optimum Bayes detectors (LOBD's) and are defined by the condition that they produce the same value of average risk and its derivative for vanishingly small input

D. Middleton

1966-01-01

48

Temperature Dependent Morphology of Untwisted Coronal Loops.  

National Technical Information Service (NTIS)

The morphology of slender coronal loops with an untwisted magnetic field is investigated. The specific shape of a loop is delineated through application of equations determining the local minor radius and loop curvature along its length. These equations f...

D. A. Garren J. Chen P. J. Cargill

1992-01-01

49

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

50

Optimum Cassegrain baffle systems.  

PubMed

Formulas are developed for the precise calculation of optimum stray-light baffles for Cassegrain optical systems, including systems having extreme optical curvatures such as those in infrared missile guidance systems. Minimum diffraction and maximum optical efficiency are the primary considerations. PMID:20733716

Hales, W L

1992-09-01

51

Optimum design of diving snorkels.  

PubMed

This manuscript deals with the development of theoretical and experimental procedures for investigating the flow phenomena associated with the clearing and breathing phases of the simple J-type snorkel. Special test stands have been built to monitor the effect of changing the snorkel geometrical parameters on its clearing efficiency and breathing resistance characteristics. The experimental results are used to check the validity of the mathematically-developed models that simulate the flow during the clearing and breathing phases. These models are then used as a basis for the development of a rational design procedure that would enable snorkel designers to select the optimum geometrical parameters in a way that guarantees a balance between the breathing and clearing requirements in snorkels. The developed procedures are general in nature and can be readily extended to study snorkels of more complex shapes when operating under various conditions and constraints. PMID:6493023

Baz, A M

1984-08-01

52

Loop Representations  

Microsoft Academic Search

The loop representation plays an important role in canonical quantum gravity because loop variables allow a natural treatment of the constraints. In these lectures we give an elementary introduction to (i) the relevant history of loops in knot theory and gauge theory, (ii) the loop representation of Maxwell theory, and (iii) the loop representation of canonical quantum gravity.

Bernd Brugmann

53

Backfire antennas constructed with coaxial circular loops  

NASA Astrophysics Data System (ADS)

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 six loops are sufficient to construct the optimum reflector, and almost the same number of loops are required to form the optimum peripheral rim. The new structure reduces the weight, windage, and obstruction of view which accompany solid reflectors. In addition, the new antenna lends itself to exact analytical investigation.

Shoamanesh, A.; Shafai, L.

1980-09-01

54

A New Optimum Pin Fin Beyond the  

Microsoft Academic Search

The problem of determining the shape of a minimum volume pin fin that dissipates a given heat flow is solved without imposing the “length-of-arc” assumption. Based on the one-dimensional approximation to the temperature distribution and Schmidt's optimality principle, the profile of the optimum pin fin is found to be a circular arc and geometric parameters of the latter are determined.

Leonid Hanin

2008-01-01

55

OPTIMUM PLASMA STATES FOR NEXT STEP TOKAMAKS  

SciTech Connect

OAK A271 OPTIMUM PLASMA STATES FOR NEXT STEP TOKAMAKS. The dependence of the ideal ballooning {beta} limit on aspect ratio, A, and elongation {kappa} is systematically explored for nearly 100% bootstrap current driven tokamak equilibria in a wide range of the shape parameters (A = 1.2-7.0, {kappa} = 1.5-6.0 with triangularity {delta} = 0.5). The critical {beta}{sub N} is shown to be optimal at {kappa} = 3.0-4.0 for all A studied and increases as A decreases with a dependence close to A{sup -0.5}. The results obtained can be used as a theoretical basis for the choice of optimum aspect ratio and elongation of next step burning plasma tokamaks or tokamak reactors.

LIN-LIU,YR; STAMBAUGH,RD

2002-11-01

56

Loop Representations  

Microsoft Academic Search

The loop representation plays an important role in canonical quantum gravity\\u000abecause loop variables allow a natural treatment of the constraints. In these\\u000alectures we give an elementary introduction to (i) the relevant history of\\u000aloops in knot theory and gauge theory, (ii) the loop representation of Maxwell\\u000atheory, and (iii) the loop representation of canonical quantum gravity. (Based\\u000aon

B. Bruegmann

1993-01-01

57

The new booster synchronization loop  

SciTech Connect

The AGS Booster must be synchronized to the AGS rf system before bunch-to-bucket transfer of the beam. The Booster delivers four batches at 7.5 Hz and extraction occurs at full acceleration rate, leaving only 5 ms available for synchronization. An improvement has been made to the synchronization feedback loop. A new loop compensator has been designed using a state variable representation. The three state variables are, beam phase and frequency, and the reference input to the beam control phase loop. The design uses linear quadratic optimum control to achieve greater stability and smaller errors. Lock acquisition, without a transient, is accomplished by a circuit that derives the loop reference from the instantaneous state variable feedback value at loop closing. The reference is brought adiabatically to zero at transfer.

Onillon, E.; Brennan, J.M. [Brookhaven National Lab., Upton, NY (United States). AGS Dept.

1995-05-01

58

Investigation of Optimum Laser Pumping.  

National Technical Information Service (NTIS)

An important task of the Optimum Pumping Technology program is the investigation of the feasibility of discharge pumping electronic transition lasers. Such an investigation requires a detailed knowledge of the secondary electron transport properties that ...

B. N. ivastava J. H. Jacob M. Rokni

1978-01-01

59

''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

60

Optimum design of trusses with discrete sizing and shape variables  

Microsoft Academic Search

The objective here is to present a method for optimizing truss structures with discrete design variables. The design variables are considered to be sizing variables as well as coordinates of joints. Both types of variables can be discrete simultaneously. Mixed continuous-discrete variables can also be considered. To increase the efficiency of the method, the structural responses, such as forces and

E. Salajegheh; G. N. Vanderplaats

1993-01-01

61

Optimum Shape of a Cooling Fin on a Convex Cylinder.  

National Technical Information Service (NTIS)

The problem considered is that of maximizing the heat dissipation of a cooling fin of fixed weight attached to a cylinder with a convex cross-section by properly tapering the fin. It is assumed that Newton's law of cooling holds and that the boundary of t...

R. J. Duffin D. K. McLain

1968-01-01

62

Optimum Design of Telecommunication Systems  

Microsoft Academic Search

This paper presents a method for network synthesis and optimum design in telecommunication and computer communication systems. Our method uses two concepts: the dynamic buffer size queue and the equivalent product form network. While the first concept helps in reducing the complexity of the network by hiding local parts in the network, the latter provides a mathematical analysis that can

Chiheb Ben Ahmed; Noureddine Boudriga; Mohammad S. Obaidat

1998-01-01

63

Optimization of structural shapes  

Microsoft Academic Search

The direct design of shapes of two dimensional structures, loaded in their plane, within specified design constraints and exhibiting optimum distribution of stresses is studied. Photoelasticity and a large field diffused polariscope is used. The optimization process involves the removal of material (with a hand file or router) from the low stress portions of the hole boundary of the model

A. J. Durelli

1981-01-01

64

Open-loop versus closed-loop control of MEMS devices: choices and issues  

Microsoft Academic Search

From a controls point of view, micro electromechanical systems (MEMS) can be driven in an open-loop and closed-loop fashion. Commonly, these devices are driven open-loop by applying simple input signals. If these input signals become more complex by being derived from the system dynamics, we call such control techniques pre-shaped open-loop driving. The ultimate step for improving precision and speed

B. Borovic; A. Q. Liu; D. Popa; H. Cai; F. L. Lewis

2005-01-01

65

Development of an Optimum Noncylindrical Fiberglass Pressure Hull for Deep Submergence.  

National Technical Information Service (NTIS)

The purpose of this program was to determine the optimum noncylindrical shape for use as a glass-reinforced-plastic deep-submergence pressure hull. Analytical parametric studies were performed to identify the pressure hull design concepts. Several lightwe...

H. R. Jacobson

1969-01-01

66

Quantized Wilson Loops with Dimensional Regularization.  

National Technical Information Service (NTIS)

Calculation of Wilson Loops (WL) to second order, are performed for different shapes of the path, using dimensional regularization techniques. Some useful formulae are developed. In particular a discussion is given on the influence of points of contact, c...

M. Abud C. G. Bollini J. J. Giambiagi

1981-01-01

67

Solar panel installation configurations for optimum system performance  

NASA Astrophysics Data System (ADS)

The main object of this paper is to identify solar panel installation configurations to achieve optimum system performance irrespective of installation surface configurations. It is important to mention that the panel installation requirements are strictly dependent on the roof configurations, Northern and Southern hemispherical locations, and the latitudes of the installation locations. Panel installation schemes for flat roof, inclined roof, inverted V-shape roof and other roof configurations are briefly discussed. Potential tracking concepts, tracking algorithms, and controllers are identified.

Jha, A. R.

2010-08-01

68

Optimum gradient of mountain paths.  

PubMed

By combining the experiment results of R. Margaria (Atti Accad. Naz. Lincei Memorie 7: 299-368, 1938), regarding the metabolic cost of gradient locomotion, together with recent insights on gait biomechanics, a prediction about the most economical gradient of mountain paths (approximately 25%) is obtained and interpreted. The pendulum-like mechanism of walking produces a waste of mechanical work against gravity within the gradient range of up to 15% (the overall efficiency is dominated by the low transmission efficiency), whereas for steeper values only the muscular efficiency is responsible for the (slight) metabolic change (per meter of vertical displacement) with respect to gradient. The speeds at the optimum gradient turned out to be approximately 0.65 m/s (+0.16 m/s vertical) and 1.50 m/s (-0.36 m/s vertical), for uphill and downhill walking, respectively, and the ascensional energy expenditure was 0.4 and 2.0 ml O2.kg body mass-1.vertical m-1 climbed or descended. When the metabolic power becomes a burden, as in high-altitude mountaineering, the optimum gradient should be reduced. A sample of real mountain path gradients, experimentally measured, mimics the obtained predictions. PMID:8594031

Minetti, A E

1995-11-01

69

Effect of Power Plant Response on Optimum Load Frequency Control System Design  

Microsoft Academic Search

The effect of the power plant time response on the closed loop roots of an optimum load frequency control system which minimizes the integral square error of control action, economic error, area control error, and the integral of area control error was obtained using root square locus techniques. A maximum value of 30 seconds for the first order plant time

Wayne Barcelo

1973-01-01

70

NICMOS Optimum Coronagraphic Focus Determinaton  

NASA Astrophysics Data System (ADS)

This test will ascertain the optimum position of the PAM for maximizing the local contrast ratios in coronagraphic images. Because of the forward motion of the NICMOS optical bench and dewar, the nominal operational position for the PAM is set {for each camera} to achieve diffraction limited focus at the image plane formed at the detector. As a result of the forward motion of the camera 2 detector, hard images are no longer formed coincidentally at the field divider mirror surface {where the coronagraphic hole is located} and at the detector. This will lead to an increase in the diffracted energy in the wings of a PSF from a target placed inside of the coronagraphic hole as the image plane will fall behind the surface of the FDA mirror. The contrast in a coronagraphic image might be enhanced by placing the focus to form an image at either image planes {FDA or detector} or at a place in-between. This is highly dependent on scattering and must be ascertained by direct measurement.

Schneider, Glenn

1997-12-01

71

Optimum hypersonic airfoil with power law shock waves  

SciTech Connect

In the present paper the flow field over a class of two-dimensional lifting surfaces is examined from the viewpoint of inviscid, hypersonic small-disturbance theory (HSDT). It is well known that a flow field in which the shock shape S(x) is similar to the body shape F(x) is only possible for F(x) = x{sup k} and the freestream Mach number M{sub {infinity}} = {infinity}. This self-similar flow has been studied for several decades as it represents one of the few existing exact solutions of the equations of HSDT. Detailed discussions are found for example in papers by Cole, Mirels, Chernyi and Gersten and Nicolai but they are limited to convex body shapes, that is, k {le} 1. The only study of concave body shapes was attempted by Sullivan where only special cases were considered. The method used here shows that similarity also exists for concave shapes and a complete solution of the flow field for any k > 2/3 is given. The effect of varying k on C{sub L}{sup 3/2}/C{sub D} is then determined and an optimum shape is found. Furthermore, a wider class of lifting surfaces is constructed using the streamlines of the basic flow field and analysed with respect to the effect on C{sub L}{sup 3/2}/C{sub D}. 9 refs., 3 figs.

Wagner, B.A.

1990-01-01

72

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

73

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

74

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

75

Auto-loop improvement  

SciTech Connect

The Consolidated Edison Company of New York, Inc. (Con Edison) has developed a computer program that predicts the reliability of auto-loops and optimizes loop design. This paper describes the application of this program to auto-loops in an urban area, the calculation of loop-specific failure data using a Bayesian data update process and the development of strategies for enhancing loop reliability. Reliabilities predicted using loop-specific data are compared to those obtained using generic data. The paper also demonstrates two alternative means of enhancing auto-loop reliability: adding protective devices to a loop and realigning its main run.

Hong, L.; Yueh, W.H. (Consolidated Edison Co. of New York, Inc., New York, NY (United States)); Allen, D.J.

1994-04-01

76

Optimum release angle in the shot put  

Microsoft Academic Search

The aim of the study was to assess the accuracy of a method of calculating the optimum release angle in the shot put. Using the proposed method, the optimum release angle that produces the greatest flight distance is calculated by combining the equation for the range of a projectile in free flight with the relations between release speed, release height

Nicholas P. Linthorne

2001-01-01

77

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

78

Optimum Significance Levels for Multistage Comparison Procedures  

Microsoft Academic Search

The framework for multistage comparison procedures in the present paper is roughly that introduced by Duncan and treated more fully by Tukey. In the present paper we consider the problem of finding the optimum allocation of nominal significance levels for successive stages. The optimum procedure we obtain when the number $s$ of treatments is odd, and the compromise procedure we

E. L. Lehmann; Juliet Popper Shaffer

1979-01-01

79

Transverse kink oscillations of expanding coronal loops  

NASA Astrophysics Data System (ADS)

Aims: We investigate the nature of transverse kink oscillations of loops expanding through the solar corona and examine how can oscillations be used to diagnose plasma parameters and the magnetic field. In particular, we aim to analyse how the temporal dependence of the loop length (here modelling the expansion) will affect the P1/P2 period ratio of transverse loop oscillations. Methods: Due to the uncertainty of the loop's shape through its expansion, we discuss separately the case of the loop that maintains its initial semi-circular shape and the case of the loop that evolves into an elliptical-shape loop from a semi-circular shape. The equations that describe the oscillations in an expanding flux tube are complicated due to the spatial and temporal dependence of coefficients. Using the WKB approximation, we find approximative values for periods and their evolution as well as the period ratio. For small values of time (near the start of the expansion), we can employ a regular perturbation method to find approximative relations for eigenfunctions and eigenfrequencies. Results: Using simple analytical and numerical methods, we show that the period of oscillations are affected by the rising of the coronal loop. The change in the period due to the increase in the loop's length is more pronounced for loops that expand into a more structured (or cooler) corona. The deviation of periods will have significant implications in determining the degree of stratification in the solar corona. The effect of expansion on the periods of oscillations is considerable only when the loop is expanding but not after it has reached its final stage. Conclusions: The present study improves our understanding of the complexity of dynamical processes in the solar corona, in particular the changes of periods of kink oscillations due to temporal changes in the characteristics of the coronal loop. Our results clearly show that the problem of expansion of coronal loops can introduce significant changes in the period of oscillations, with consequences on the seismological diagnostics of the plasma and magnetic field.

Ballai, I.; Orza, B.

2012-09-01

80

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

81

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

82

Miniaturised Capillary Pumped Loops: Design and Operating Limits  

Microsoft Academic Search

This paper has two main objectives: i) to propose some design changes compared to the ones available in the literature in\\u000a order to improve the reliability of micro capillary pumped loop operating at steady state and ii) to demonstrate the existence\\u000a of an optimum in the loop ability to extract and transport heat flux considering classical constraint of electronic devices.

Valérie Serin; Pascal Lavieille; Marc Miscevic

2009-01-01

83

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

84

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

85

Optimum 3-step step-stress tests  

Microsoft Academic Search

Optimum simple step-stress accelerated life testing plans have practical limitations. They highly depend upon the assumption of a linear relationship between stress and time-to-failure and use only two extreme stresses that can cause irrelevant failure modes. Thus, 3-step plans are preferable. In this paper, the authors derive the optimum quadratic plan and propose and evaluate a 3-step test plan, the

Imad I. H. Khamis; James J. Higgins

1996-01-01

86

Loop transfer matrix and loop quantum mechanics  

NASA Astrophysics Data System (ADS)

The gonihedric model of random surfaces on a 3d euclidean lattice has equivalent representation in terms of transfer matrix K(Qi,Qf) which describes the propagation of loops Q. We extend the previous construction of loop transfer matrix to the case of non-zero self-intersection coupling constant kappa. We introduce loop generalization of Fourier transformation which allows to diagonalize transfer matrices depending on symmetric difference of loops and express all eigenvalues of 3d loop transfer matrix through the correlation functions of the corresponding 2d statistical system. The loop Fourier transformation allows to carry out analogy with quantum mechanics of point particles, to introduce conjugate momentum loop P and to define loop quantum mechanics. We also consider transfer matrix on 4d lattice which describes propagation of memebranes. This transfer matrix can also be diagonalized by using generalized Fourier transformation, and all its eigenvalues are equal to the correlation functions of the corresponding 3d statistical system. Particularly the free energy of the 4d membrane system is equal to the free energy of 3d gonihedric system of loops.

Savvidy, George K.

2000-09-01

87

Active Region Loop Models and Observations  

NASA Astrophysics Data System (ADS)

The analysis of broad band images from EIT and TRACE and spectra from SUMER and CDS have triggered a heated debate on 1) whether the loops are isothermal for most of their length 2) whether they are multithermal across their section and 3) what is the shape of their heating function. Our work describes a detailed comparison between SOHO-CDS observations of an active region loop with a standard RTV-like loop model developed assuming a temperature-independent heating function in the energy balance equation and a variable loop cross-section. Observations of an active region loop recorded by CDS have been analyzed. Additional data from EIT MDI and Yohkoh-SXT have been considered. Electron density temperature and pressure along the selected loop structure have been measured by means of line ratio techniques and an emission measure analysis. Comparison with CDS data has shown that 1) the RTV-like model is not able to reproduce the observations 2) the loop is isothermal along most of its length 3) the loop is isothermal across its section.

Landi, E.; Landini, M.

2004-01-01

88

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

89

Thermal analysis and optimum design for radiating spine of various geometries  

NASA Astrophysics Data System (ADS)

The general governing equations for radiating spines are solved to determine the general relationships for spine dimensions, the heat transfer characteristics under the optimum condition, and a least material profile among radiating spines. Similar to convecting spines, the optimum shapes of the radiating spines become wider at the base and longer in height. The optimum heat transfer rate is found to be proportional to the three-fifths power of the spine volume, and the spine profile with the larger value of n is shown to be always superior in terms of heat dissipation per unit volume or mass. From the optimum temperature distribution of radiating spine profiles of least material, the slope of the temperature curve at the spine tip is shown to approach infinity, though the heat flux is equal to zero at the spine tip.

Chung, B. T. F.; Nguyen, L. D.

90

Midpoint Shapes.  

ERIC Educational Resources Information Center

Emphasizes the importance of children exploring hands-on and minds-on mathematics. Presents a midpoint shape activity for students to explore the midpoint shape of familiar quadrilaterals, such as squares and rectangles. (KHR)

Welchman, Rosamond; Urso, Josephine

2000-01-01

91

Pulse distortion and optimum transmit waveform for pulse-based UWB communications  

Microsoft Academic Search

This paper initiates a new investigation of optimum transmission waveforms in the presence of per-path pulse wave shape distortion - a physical mechanism unique to impulsive signals. First, the transient electromagnetic analysis is carried out to derive, for the first time, closed-form expressions for the impulse responses of several canonical channels that are suitable for communication engineers. Second, numerical calculation

Chenming Zhou; Robert C. Qiu

2009-01-01

92

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

93

Optimization of structural shapes  

NASA Astrophysics Data System (ADS)

The direct design of shapes of two dimensional structures, loaded in their plane, within specified design constraints and exhibiting optimum distribution of stresses is studied. Photoelasticity and a large field diffused polariscope is used. The optimization process involves the removal of material (with a hand file or router) from the low stress portions of the hole boundary of the model till an isochromatic fringe coincides with the boundary both on the tensile and compressive segments. Applications are also shown to the design of dove tails and slots in turbine blades and rotors, and to the design of star shaped solid propellant grains for rockets, both for the case of parallel side rays and enlarged tip of rays. The use of other methods, in particular the method using finite elements, to optimize structural forms is discussed.

Durelli, A. J.

1981-04-01

94

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

95

Cellulose Shapes  

Microsoft Academic Search

This chapter surveys the shapes of cellulose molecules. New, high-resolution experiments on the various crystalline polymorphs are reviewed, and their similar twofold helical shapes are compared. Conversion between cellulose I and II is discussed, including interdigitation and chain-folding as possible mechanisms. Information on molecular shape from cellotriose and tetraose is also reviewed along with data for derivatives and complexes. To

Alfred D. French; Glenn P. Johnson

96

Response of an All Digital Phase-Locked Loop  

Microsoft Academic Search

An all digital phase-locked loop (DPLL) is designed, analyzed, and tested. Three specific configurations are considered, generating first, second, and third order DPLL's; and it is found, using a computer simulation of a noise spike, and verified experimentally, that of these configurations the second-order system is optimum from the standpoint of threshold extension. This substantiates results obtained for analog PLL's.

J. Garodnick; J. Greco; D. Schilling

1974-01-01

97

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

2012-01-17

98

VLF Loop Array Antenna.  

National Technical Information Service (NTIS)

The report describes a directional loop array antenna for very low frequency (VLF) reception. The array comprises four closely spaced loop antennas forming a unidirectional reception pattern with a main beam of less than 43 deg between half power points. ...

E. W. Seeley

1978-01-01

99

Phase-locked loops  

Microsoft Academic Search

An attempt to systematically outline the work done in the area of phase-locked loops which are now used in modern communication system design is presented. The analog phase-locked loops are well documented in several books but discrete, analog-digital, and digital. phase-locked loop work is scattered. Apart from discussing the various analysis, design, and application aspects of phase-locked loops, a number

S. C. Gupta

1975-01-01

100

Optimum synthesis for time scale generation.  

PubMed

A time scale can be regarded as a synthesis of readings from precise clocks. Usually such synthesis is based on the principle of weighted averaging, which balances the contribution of each clock according to its noise level. It is well known that there are five different noise processes in precise clocks. Therefore, a good synthesis should balance each of those noise levels. Most existing algorithms control only one or two noise types. If an algorithm can control all five noise types simultaneously, we consider it to be optimum. The key point of constructing an optimum algorithm is the separation of all five noise types. In this paper, an optimum algorithm is presented using the half-integrating/half-differentiating model by which the five noise types are separated correctly. Performances of the new algorithm are demonstrated with simulated and real data. PMID:18238481

Zhu, S; Wei, G

1999-01-01

101

On Open Loop and Closed Loop Nash Strategies.  

National Technical Information Service (NTIS)

For deterministic nonzero-sum differential games, every open loop Nash strategy set is a closed loop Nash strategy set. The converse, that the open loop strategy set generated by a closed loop Nash strategy set is Nash, is false.

N. R. Sandell

1973-01-01

102

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

Microsoft Academic Search

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)

Vigil

1988-01-01

103

Optimum design of single core shear walls  

Microsoft Academic Search

Design of reinforced concrete thin walled open sections subjected to combined loading such as axial force, biaxial bending moment and torsional moment is cumbersome. This is due to the fact that such structures possess very little torsional rigidity and the plane cross section does not remain plane after the deformation. In this study, an algorithm is developed for the optimum

S. S. Al-Mosawi; M. P. Saka

1999-01-01

104

Optimum design of vertical rectangular fin arrays  

Microsoft Academic Search

The goal of this analysis has been the search for the optimal configuration for a finned plate (with rectangular and vertical fins) to be cooled in natural convection. Utilizing a simplified relation of the fins heat exchange some simple expressions for the determination of the optimum value of the fins spacing have been developed as a function of the parameters

Andrea de Lieto Vollaro; Stefano Grignaffini; Franco Gugliermetti

1999-01-01

105

Optimum Part Deposition Orientation in Stereolithography  

Microsoft Academic Search

In the present work an attempt has been made to achieve minimum average part surface roughness (best overall surface quality) for Stereolithography processed parts by determining optimum part deposition orientation. A conventional optimization algorithm based on Trust Region Method (available with MATLAB 6.5 optimization tool box) has been used to solve the optimization problem. It is observed that the problem

S. K. Singhal; A. P. Pandey; P. M. Pandey; A. K. Nagpal

2005-01-01

106

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

107

On the optimum sizing of cooling towers  

Microsoft Academic Search

The optimum heat and mass transfer area at which minimum cost exists throughout the technical life of forced draft counter-current cooling towers is studied in the present work. Original formulae are developed and presented for the best thermoeconomical performance as a design point.

M. S Söylemez

2001-01-01

108

Optimum design of solid rocket motor nozzles  

Microsoft Academic Search

In order to design an optimum nozzle for air-air missile solid rocket motors, a mass model of a solid rocket motor, a nozzle specifice impulse model of a solid rocket motor, and the objective function are established. Five different type of nozzles are chosen for calculation. Conical, paraboloidal, two different arcs, quadratic polynomial, and cubic polynomial. The optimization results show

Guoyao Fang; Qing Wang; Shanhui Gao

1993-01-01

109

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

110

Optimum structured adsorbents for gas separation processes  

Microsoft Academic Search

Recent developments in separation technology by adsorption have included the development of new structured adsorbents which offer some attractive characteristics compared to a typical packed bed. These improved features include lower energy consumption, higher throughput and superior recovery and purity of product. However, the exact combination of structural, geometric parameters which yields optimum performance is unknown. This study formulates a

Fateme Rezaei; Paul Webley

2009-01-01

111

Optimum Propulsion of an Oscillating Hydrofoil.  

National Technical Information Service (NTIS)

A study is made on the optimization aspect of marine propulsion in the light of optimum control theory for distributed parameter systems. In particular, the problem of determining the motion of a thin hydrofoil or a 'thin fish' to maximize the average thr...

P. K. C. Wang

1966-01-01

112

Optimum siting of wind turbine generators  

Microsoft Academic Search

This paper investigates optimum siting of wind turbine generators from the viewpoint of site and wind turbine generator selection. The methodology of analysis is based on the accurate assessment of wind power potential of various sites. The analytical computations of annual and monthly capacity factors are done using the Weibull statistical model using cubic mean cube root of wind speeds.

Suresh H. Jangamshetti; V. G. Ran

2001-01-01

113

Optimum Probability Estimation from Empirical Distributions.  

ERIC Educational Resources Information Center

Discusses the interdependencies between parameter estimation and properties of probabilistic models, such as dependency assumptions, binary vs. nonbinary features, and estimation sample selection. An optimum estimation for binary features applicable to information retrieval is defined, a method for computing this estimation using empirical data is…

Fuhr, Norbert; Huther, Hubert

1989-01-01

114

On the optimum quantity of money  

Microsoft Academic Search

t is pretty well established within Austrian economics that the optimum quantity of money is whatever level is established at any given time. The logical implication of this claim is that any amount of the commodity that intermediates trade will do as well as any other in acquitting this task. This being the case, there is no social or even

WILLIAM BARNETT II; Walter Block

2004-01-01

115

The Optimum Thermal Environment for Naked Babies  

PubMed Central

The optimum thermal environment in which to nurse a baby naked in an incubator has been defined from a knowledge of the magnitude of the factors affecting thermal balance. Such a neutral environment allows body temperature to remain normal while oxygen consumption and evaporative water loss are both at a minimum.

Hey, E. N.; Katz, G.

1970-01-01

116

Optimum Network Var Planning by Nonlinear Programming  

Microsoft Academic Search

Controllable network VAr compensators are required in high voltage transmission networks for system loss reduction and voltage maintenance during normal and emergency operation. Long term planning of network compensators is generally based on contingencies which cause the system voltage to move out of the desired operational range. A non-linear analysis based on multi-contingency states is presented for optimum network VAr

S. S. Sachdeva; R. Billinton

1973-01-01

117

Adaptive techniques for Evolutionary Topological Optimum Design  

Microsoft Academic Search

This paper introduces some advances in Evolutionary Topological Optimum Design, thanks to extensive use of adaptive techniques. On the genotypic side, a variable length representation is used: the complexity of the representation of each individual is evolved by the algorithm rather than being prescribed by some fixed mesh of the design domain, resulting in self-adaptive complexity. On the phenotypic side,

Hatem Hamda; Marc Schoenauer

2000-01-01

118

Optimum scaling of buried-channel CCD's  

Microsoft Academic Search

The maximum charge packet size in a two-phase charge-coupled device (CCD) is limited by many constraints relating to the transfer efficiency requirement and control circuit limitations. The constraints are quantified and an optimization routine is developed for designing CCD's with maximum charge capacity per unit area under these constraints. The optimum charge capacity for scaled down CCD's is calculated and

P. K. Chatterjee; G. W. Taylor

1980-01-01

119

Optimum phase ratio in the triple jump  

Microsoft Academic Search

The purpose of this study was to develop and validate a method to determine the optimum phase ratio that yields the longest actual distance for a given triple jumper. Two hypotheses were tested: (a) for any given triple jumper, the greater the gain in the vertical velocity the greater the loss in the horizontal velocity; and (b) there is no

Bing Yu; James G. Hay

1996-01-01

120

A Near-Optimum Parallel Planarization Algorithm  

Microsoft Academic Search

A near-optimum parallel planarization algorithm is presented. The planarization algorithm, which is designed to embed a graph on a plane, uses a large number of simple processing elements called neurons. The proposed system, composed of an N × N neural network array (where N is the number of vertices), not only generates a near-maximal planar subgraph from a nonplanar graph

Yoshiyasu Takefuji; Kuo-Chun Lee

1989-01-01

121

OPTIMUM COAL MINE WATER RECLAMATION PROJECT  

Microsoft Academic Search

Optimum Coal Mine comprises numerous defunct, active and future mining sections. The mine is primarily a large opencast coal mine. Opencast and underground mining activities have a significant impact on surface and groundwater resources. To ensure that the mine will be able to continue with their mining operation in the catchment, the extent of this impact requires that substantial intervention

V. E. COGHO; A. M. van NIEKERK

122

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

123

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

124

Minimum engine size for optimum automobile acceleration  

SciTech Connect

The theoretical minimum for engine power rating required to accelerate a vehicle of mass {ital M} to velocity {ital V} in time {ital T} is shown to result from acceleration at constant maximum power. Because actual conditions do not allow infinite starting acceleration, the power per unit mass to provide optimum feasible acceleration with minimum engine power rating is given by {ital P}{sub opt}/{ital M}={ital a}{sup 2}{sub max}{ital T}{sub {ital c}}, where {ital a}{sub max} is the maximum starting acceleration and {ital T}{sub {ital c}} is the crossover time from maximum acceleration to the curve of acceleration at constant maximum power. Comparison with analysis of performance data for 18 automobiles reveals that 17 achieve near-optimum power usage.

Haaland, C.M. (Oak Ridge National Laboratory, Oak Ridge Tennessee 37831 (United States))

1992-05-01

125

Taux d'actualisation et optimum second  

Microsoft Academic Search

[fre] Cet article considère la littérature sur le taux d'actualisation en situation d'opti­mum second. Après examen des raisons pour lesquelles l'approche en termes d'optimum premier est inadéquate, et des quelques arguments s'y rattachant, dis­tinction est faite entre modèles « de politique optimale » et modèles « de réforme ». L'accent est mis sur la notion importante de coût d'opportunité des

Jean Tirole

1981-01-01

126

Optimum design of solid rocket motor nozzles  

NASA Astrophysics Data System (ADS)

In order to design an optimum nozzle for air-air missile solid rocket motors, a mass model of a solid rocket motor, a nozzle specifice impulse model of a solid rocket motor, and the objective function are established. Five different type of nozzles are chosen for calculation. Conical, paraboloidal, two different arcs, quadratic polynomial, and cubic polynomial. The optimization results show that the models established are correct. The method can be used as a reference for other nozzle designs.

Fang, Guoyao; Wang, Qing; Gao, Shanhui

1993-06-01

127

Optimum design of brushless tubular linear machines  

Microsoft Academic Search

A method which uses finite-element techniques for designing linear tubular brushless DC machines is described. The design technique makes use of approximate calculations to decide the machine dimensions. Finite-element analysis is then employed to calculate a series of designs and determine the optimum one. The effects of variation in slot depth and pole pitch are illustrated. The finite-element analysis is

J. F. Eastham; R. Akmese; H. C. Lai

1990-01-01

128

Optimum linear filter for speech communication  

Microsoft Academic Search

Linear filtering at the transmitter can enhance speech intelligibility over a noisy channel when the transmitter is peak-power limited. Griffiths (1968) derived an optimum filter analytically using the articulation index concept and measured an improvement equivalent to 2.5 to 4 dB increase in transmitter power. Thomas and Ohley (1972) derived a different filter empirically and measured a much larger improvement.

C. Allen

1979-01-01

129

Laminated BEAM loops  

NASA Astrophysics Data System (ADS)

BEAM sensors include treated loops of optical fiber that modulate optical throughput with great sensitivity and linearity, in response to curvature of the loop out of its plane. This paper describes BEAM sensors that have two loops treated in opposed fashion, hermetically sealed in flexible laminations. The sensors include an integrated optoelectronics package that extracts curvature information from the treated portion of the loops while rejecting common mode errors. The laminated structure is used to sense various parameters including displacement, force, pressure, flow, and acceleration.

Danisch, Lee A.

1996-10-01

130

Evaluation of tensile strength of different configurations of orthodontic retraction loops for obtaining optimized forces  

Microsoft Academic Search

SUMMARY The aim of this study was to analyze the mechanical behavior of different orthodontic retraction loops. Two designs of orthodontic loops for closing space were analyzed: teardrop-shaped (T) and circle-shaped loop (C), of two different heights (6 and 8 mm), and two types of orthodontic wires (stainless steel - 0.19' × 0.25'; TMA - titanium molybdenum alloy - 0.016'

Miceli Beck; Guimaraes Blaya; Graziela Henriques Westphalen; Magali Beck Guimaraes; Luciana Mayumi Hirakata

131

Optimum folding pathways of proteins: Their determination and properties  

NASA Astrophysics Data System (ADS)

We develop a dynamic optimization technique for determining optimum folding pathways of proteins starting from different initial configurations. A coarse-grained Go model is used. Forces acting on each bead are (i) the friction force, (ii) forces from bond length constraints, (iii) excluded volume constraints, and (iv) attractive forces between residue pairs that are in contact in the native state. An objective function is defined as the total attractive energy between nonbonded residues, which are neighbors in the native state. The objective function is minimized over all feasible paths, satisfying bond length and excluded volume constraints. The optimization problem is nonconvex and contains a large number of constraints. An augmented Lagrangian method with a penalty barrier function was used to solve the problem. The method is applied to a 36-residue protein, chicken villin headpiece. Sequences of events during folding of the protein are determined for various pathways and analyzed. The relative time scales are compared and scaled according to experimentally measured events. Formation times of the helices, turn, and the loop agree with experimental data. We obtain the overall folding time of the protein in the range of 600 ns-1.2 ?s that is smaller than the experimental result of 4-5 ?s, showing that the optimal folding times that we obtain may be possible lower bounds. Time dependent variables during folding and energies associated with short- and long-range interactions between secondary structures are analyzed in modal space using Karhunen-Loeve expansion.

Güner, U?ur; Arkun, Yaman; Erman, Burak

2006-04-01

132

SPL Shape  

Center for Drug Evaluation (CDER)

... Tablets with a capsule shape or a one part capsules (eg, soft gelatin capsules that are filled with a liquid) should be classified under OVAL. C48336. ... More results from www.fda.gov/drugs/developmentapprovalprocess/formssubmissionrequirements

133

Shape Up!  

NSDL National Science Digital Library

In this activity (25th on the page) about learning and memory, learners explore a training method that animal trainers employ called "shaping." Working in pairs, learners will attempt to "shape" each other to complete a task through rewarding and reinforcing positive behavior. Learners will earn "treats" for each correct behavior. Use this activity to teach learners how behaviors can be learned and trained and/or how trainers use non-verbal techniques to work with animals.

Chudler, Eric H.

2010-01-01

134

Shape Interrogation  

Microsoft Academic Search

Shape interrogation methods are of increasing interest in geometric modeling as well as in computer graphics. Originating\\u000a 20 years ago from CAD\\/CAM applications where “class A” surfaces are required and no surface imperfections are allowed, shape\\u000a interrogation has become recently an important tool for various other types of surface representations such as triangulated\\u000a or polygonal surfaces, subdivision surface, and algebraic

Stefanie Hahmann; Alexander Belyaev; Laurent Busé; Gershon Elber; Bernard Mourrain; Christian Rössl

135

Robust Hitting with Dynamics Shaping  

NASA Astrophysics Data System (ADS)

The present paper proposes the trajectory planning based on “the dynamics shaping” for a redundant robotic arm to hit a target robustly toward the desired direction, of which the concept is to shape the robot dynamics appropriately by changing its posture in order to achieve the robust motion. The positional error of the end-effector caused by unknown disturbances converges onto near the singular vector corresponding to its maximum singular value of the output controllability matrix of the robotic arm. Therefore, if we can control the direction of the singular vector by applying the dynamics shaping, we will be able to control the direction of the positional error of the end-effector caused by unknown disturbances. We propose a novel trajectory planning based on the dynamics shaping and verify numerically and experimentally that the robotic arm can robustly hit the target toward the desired direction with a simple open-loop control system even though the disturbance is applied.

Yashima, Masahito; Yamawaki, Tasuku

136

Molten salt test loop  

Microsoft Academic Search

The objective of the Molten Salt Test Loop Project was to design, construct, and demonstrate operation of an outdoor high temperature molten salt test facility. This facility is operational, and can now be used to evaluate materials and components, and the design features and operating procedures required for molten salt heat transport systems. The initial application of the loop was

J. R. Schuster; G. H. Eggers

1980-01-01

137

Fiber loop optical buffer  

Microsoft Academic Search

Fiber loop optical buffers enable data storage for discrete time intervals and therefore appear suitable for applications in optical asynchronous transfer mode (OATM)-based networks where data are transmitted in cells of fixed length. In this paper, the feasibility and the limitations of optical data storage in a fiber loop optical buffer are studied theoretically and experimentally, A model of a

R. Langenhorst; M. Eiselt; W. Pieper; G. Grosskopf; R. Ludwig; L. Kuller; E. Dietrich; H. G. Weber

1996-01-01

138

Physical structure of solar cool loops.  

NASA Astrophysics Data System (ADS)

Recently, studies and observations focused on the solar transition region and the low corona have shown the importance of small and cool magnetic loops in producing most of the solar EUV output at temperatures below 1 MK. This kind of structures has remained only poorly characterized in terms of physical properties. We study the possibility of obtaining cool loops using unidimensional hydrodynamic simulations, performed with a state-of-the-art numerical code with a fully adaptive grid. The dependence of their physical structures on the form of the radiative losses function has been explored. We find, as a first result, that the shape of the radiative losses function for T<105 K imposes restrictive conditions on the existence and the stability of such cool loops.

Sasso, C.; Susino, R.; Andretta, V.; Spadaro, D.

139

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

140

New method determines optimum surface casing depth  

SciTech Connect

A set of equations, based on kick tolerance theory and the driller's method and well control, helps determine the optimum depth for setting surface casing. Operators can drill wells more safely by understanding the primary purpose for surface casing instead of automatically setting the casing to a depth prescribed by regulations. This new method is the basis for recent regulation changes on surface casing setting depths in Alberta. The depths determined with the new method compare favorably with the depths currently used by industry. The paper discusses US regulations, Canadian regulations, surface casing depth, kick tolerance, leak-off tests, Alberta requirements, reduction system, and financial impact.

Baron, S.; Skarstol, S. (Energy Resources Conservation Board, Calgary, Alberta (Canada))

1994-02-07

141

Optimum Intensity Settings of Approach and Runway Light Systems.  

National Technical Information Service (NTIS)

Criteria for determining the optimum intensity settings of approach and runway lights, as a function of atmospheric transmissivity and/or meteorological visibility, have been developed. In determining the optimum intensity settings, consideration was give...

C. A. Douglas

1979-01-01

142

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

143

Shape control using sidewall imaging  

NASA Astrophysics Data System (ADS)

As gate widths shrink below 0.18 micrometer, the SPC (Statistical Process Control) based CD (Critical Dimension) control in lithography process becomes more difficult. Increasing requirements of a shrinking process window have called on the need for advanced CD control using a closed-loop feedback mechanism. This concept has been gaining momentum and shows promising advantages in shortening the time of feedback control. However, the current closed-loop feedback links only the average CD of a lot and the exposure dose (E), leaving out another critical lithography parameter -- stepper, or scanner, defocus (F). Up until now, F has been assumed constant while E has been shown to have one-to-one correlation with CD. Such an assumption is justified for feature sizes larger than 0.25 micrometer with a usable DOF (Depth Of Focus) of more than 1 micrometer. For 0.25 micrometer and below technologies, stepper defocus induces rapid feature profile, as well as CD, changes. Therefore, one parameter (exposure dose versus CD) feedback is not adequate enough to control CD in photolithography and a two-parameter (exposure dose and stepper defocus versus CD) feedback is needed. For stepper defocus variation, resist feature shape needs to be monitored in-line. We will present an innovative way of shape monitoring through sidewall imaging. The scanning beam is bent up to 5 degrees, so that a feature can be viewed from a tilted angle. Such tilted view greatly enhances edge resolution. Shape monitoring applications based on sidewall imaging will be presented. With both CD and shape are monitored in photolithography process, two critical parameters, i.e., exposure dose and defocus, can be easily controlled. Such shape control mechanism provides the base for two-parameter feedback loop.

Su, Bo; Oshana, Ramiel; Menaker, Mina; Barak, Yogev; Shi, Xuelong

2000-06-01

144

Dehumidification -- Closed loop systems  

SciTech Connect

Dehumidification is the removal of water from the air. Dehumidification equipment treats the ambient air before it is introduced to the enclosure. A closed loop system is one that theoretically routes all the air exiting an enclosure through the appropriate filter media and treatment equipment and then returns it to the enclosure. By establishing a closed loop system, the ``treated`` air is continuously processed, which improves the efficiency of this operation. The generic types of dehumidification equipment and their application in a closed loop system will be presented. This article will deal solely with the use of dehumidification and other related equipment used to control the environment within the work enclosure.

Wyatt, C.H. [Enviro-Air Control Corp., Houston, TX (United States); Crowe, A.R. [C.H. Heist Ltd., Oakville, Ontario (Canada)

1996-05-01

145

Multiprotein DNA looping.  

PubMed

DNA looping plays a fundamental role in a wide variety of biological processes, providing the backbone for long range interactions on DNA. Here we develop the first model for DNA looping by an arbitrarily large number of proteins and solve it analytically in the case of identical binding. We uncover a switchlike transition between looped and unlooped phases and identify the key parameters that control this transition. Our results establish the basis for the quantitative understanding of fundamental cellular processes like DNA recombination, gene silencing, and telomere maintenance. PMID:16803410

Vilar, Jose M G; Saiz, Leonor

2006-06-15

146

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

147

On the optimum range resolution of radar signals in noise  

Microsoft Academic Search

Optimum radar resolution is recognized to be a problem in distinguishing between different possible target configurations. Radar reception systems which perform optimum range resolution are then designed using the principles of statistical decision theory. In particular, the design of the optimum resolution system is carried out for a squared-error loss function, modified to provide extra penalties for wrong guesses about

N. Nilsson

1961-01-01

148

Natively Unstructured Loops Differ from Other Loops  

PubMed Central

Natively unstructured or disordered protein regions may increase the functional complexity of an organism; they are particularly abundant in eukaryotes and often evade structure determination. Many computational methods predict unstructured regions by training on outliers in otherwise well-ordered structures. Here, we introduce an approach that uses a neural network in a very different and novel way. We hypothesize that very long contiguous segments with nonregular secondary structure (NORS regions) differ significantly from regular, well-structured loops, and that a method detecting such features could predict natively unstructured regions. Training our new method, NORSnet, on predicted information rather than on experimental data yielded three major advantages: it removed the overlap between testing and training, it systematically covered entire proteomes, and it explicitly focused on one particular aspect of unstructured regions with a simple structural interpretation, namely that they are loops. Our hypothesis was correct: well-structured and unstructured loops differ so substantially that NORSnet succeeded in their distinction. Benchmarks on previously used and new experimental data of unstructured regions revealed that NORSnet performed very well. Although it was not the best single prediction method, NORSnet was sufficiently accurate to flag unstructured regions in proteins that were previously not annotated. In one application, NORSnet revealed previously undetected unstructured regions in putative targets for structural genomics and may thereby contribute to increasing structural coverage of large eukaryotic families. NORSnet found unstructured regions more often in domain boundaries than expected at random. In another application, we estimated that 50%–70% of all worm proteins observed to have more than seven protein–protein interaction partners have unstructured regions. The comparative analysis between NORSnet and DISOPRED2 suggested that long unstructured loops are a major part of unstructured regions in molecular networks.

Schlessinger, Avner; Liu, Jinfeng; Rost, Burkhard

2007-01-01

149

Dissociated Prismatic Dislocation Loops.  

National Technical Information Service (NTIS)

Transmission electron microscopy observations on heterogeneous precipitation in dilute aluminum-base silver alloys tend to support a previously proposed model for dissociated prismatic dislocation loops. During the initial stage of precipitation, the perf...

A. K. Eikum

1968-01-01

150

Heating of postflare loops  

SciTech Connect

The heating of postflare loops by slow MHD shocks is considered. Although such loops were once thought to represent the dying remnant of a two-ribbon flare, it is now realized that they are the main part of such an event and begin very early on. It is shown that, if the local temperature of a loop, its local angle of inclination to the vertical, and ambient coronal conditions are known from observations, then simple analytical formulae give the rise speed of the shocks and the magnitude of the evaporative flow incident upon them. The formulae are applied as an example to the 1973 July 29 and 1980 May 21 two-ribbon flares, and reasonable agreement with rise-speed observations is found. It is therefore claimed that shock heating is a viable method for heating postflare loops for the long times observed.

Cargill, P.J.; Priest, E.R.

1983-03-01

151

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

152

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,

153

Closed-Loop Systems  

NSDL National Science Digital Library

Teachers' Domain presents this interactive lesson on closed-loop systems, which includes an animation that describes the typical components of a closed-loop system (error detector, controller, actuator, and measurement device), and describes the input and output signals for each component. The interactive lesson includes three sections: introduction, system overview, and adjustment scenarios. The activity includes 18 screens with reading materials as well as a supplemental background essay, discussion questions, and standards alignment from Teachers' Domain.

2010-10-11

154

Pseudoresonance Argand loops  

Microsoft Academic Search

The root and logarithmic singularities of the partial amplitude corresponding to a box diagram with a resonance and a particle in the intermediate state lead to resonance-like loops (pseudoresonances) on the Argand diagram in the case of hadronic masses and widths. Examples of pseudoresonance loops are given for the reactions ..pi..d (..delta..N) ..pi..d, NN (..delta..N) ..pi..d, ..pi..N (rhoN) ..pi..N, KN

I. M. Narodetskii; Y. A. Simonov

1978-01-01

155

Optimum antenna for Alfven wave heating  

SciTech Connect

Modifications in the Alfven wave heating contributed by the plasma equilibrium current through the rotational transform and the enhanced Hall effect are studied in a model that includes electron Landau damping and a 3-D Faraday shielded antenna. Optimum coupling with Rapprox. =0.7..cap omega.. occurs for n = 8 and is not significantly affected by the equilibrium current. The antenna Qapprox. =17 is comparable to the ICRF antennas, while the surface heating is negligibly small. For the large napprox.8 values, mode splitting due to the removal of the poloidal degeneracy combined with the finite electron temperature effects, leads to significant broadening of the energy absorption profile. No evidence of discrete Alfven wave (DAW) excitation is observed.

Puri, S.

1987-09-01

156

The optimum dimensions of radiative spines  

NASA Astrophysics Data System (ADS)

Radiative pin fins (spines) are important in conjunction with heat rejection systems for space applications. In the design of radiators for space applications, spines possessing minimum mass are of great interest. In this study a conducting-radiating spine with an arbitrary profile is considered. The profile is assumed to be a function of the temperature in the spines by introducing a free parameter. With this choice of profile, the nonlinear heat transfer equation for the conducting-radiating spine can be integrated analytically. Using this method, a nonlinear integral equation for the temperature of the spine is obtained. This equation can be conveniently solved numerically to find the optimum dimensions of the spine.

Razani, A.; Zohoor, H.

157

Understanding Warm Coronal Loops  

NASA Astrophysics Data System (ADS)

One of the great mysteries of coronal physics that has come to light in the last few years is the discovery that warm (~ 1 MK) coronal loops are much denser than expected for quasi-static equilibrium. It has been shown that the excess density can be explained if loops are bundles of unresolved strands that are heated impulsively and quasi-randomly to very high temperatures. This picture of nanoflare heating predicts that neighboring strands of different temperature should coexist and therefore that loops should have multi-thermal cross sections. In particular, emission should be produced at temperatures hotter than 2 MK. Such emission is sometimes but not always seen, however. We offer two possible explanations for the existence of over-dense warm loops without corresponding hot emission: (1) loops are bundles of nanoflare heated strands, but a significant fraction of the nanoflare energy takes the form of a nonthermal electron beam rather then direct heating; (2) loops are bundles of strands that undergo thermal nonequilibrium that results when steady heating is sufficiently concentrated near the footpoints. We verify these possibilities with numerical hydro simulations. Time permitting, we will show FeXVII line profile observations from EIS/Hinode that support the existence of nanoflare heating. Work supported by NASA and ONR.

Klimchuk, J. A.; Karpen, J. T.; Patsourakos, S.

2007-12-01

158

Optimum frequency band for radio polarization observations  

NASA Astrophysics Data System (ADS)

Polarized radio synchrotron emission from interstellar, intracluster and intergalactic magnetic fields is affected by frequency-dependent Faraday depolarization. The maximum polarized intensity depends on the physical properties of the depolarizing medium. New-generation radio telescopes such as Low Frequency Array (LOFAR), the Square Kilometre Array (SKA) and its precursors need a wide range of frequencies to cover the full range of objects. The optimum frequency of maximum polarized intensity (PI) is computed for the cases of depolarization in magneto-ionic media by regular magnetic fields (differential Faraday rotation) or by turbulent magnetic fields (internal or external Faraday dispersion), assuming that the Faraday spectrum of the medium is dominated by one component or that the medium is turbulent. Polarized emission from bright galaxy discs, spiral arms and cores of galaxy clusters are best observed at wavelengths below a few centimetres (at frequencies beyond about 10 GHz), haloes of galaxies and clusters around decimetre wavelengths (at frequencies below about 2 GHz). Intergalactic filaments need observations at metre wavelengths (frequencies below 300 MHz). Sources with extremely large intrinsic rotation measure | RM | or RM dispersion can be searched with mm-wave telescopes. Measurement of the PI spectrum allows us to derive the average Faraday | RM | or the Faraday dispersion within the source, as demonstrated for the case of the spiral galaxy NGC 6946. Periodic fluctuations in PI at low frequencies are a signature of differential Faraday rotation. Internal and external Faraday dispersion can be distinguished by the different slopes of the PI spectrum at low frequencies. A wide band around the optimum frequency is important to distinguish between varieties of depolarization effects.

Arshakian, Tigran G.; Beck, Rainer

2011-12-01

159

The Energy Landscape of Hyperstable LacI-DNA Loops  

NASA Astrophysics Data System (ADS)

The Escherichia coli LacI protein represses transcription of the lac operon by blocking access to the promoter through binding at a promoter-proximal DNA operator. The affinity of tetrameric LacI (and therefore the repression efficiency) is enhanced by simultaneous binding to an auxiliary operator, forming a DNA loop. Hyperstable LacI-DNA loops were previously shown to be formed on DNA constructs that include a sequence-directed bend flanked by operators. Biochemical experiments showed that two such constructs (9C14 and 11C12) with different helical phasing between the operators and the DNA bend form different DNA loop shapes. The geometry and topology of the loops and the relevance of alternative conformations suggested by probable flexible linkers in LacI remain unclear. Bulk and single molecule fluorescence resonance energy transfer (SM-FRET, with D. English) experiments on a dual fluorophore-labeled 9C14-LacI loop demonstrate that it adopts a single, stable, rigid closed-form loop conformation. Here, we characterize the LacI-9C14 loop by SM-FRET as a function of inducer isopropyl-?,D-thiogalactoside (IPTG) concentration. Energy transfer measurements reveal partial but incomplete destabilization of loop formation by IPTG. Surprisingly, there is no change in the energy transfer efficiency of the remaining looped population. Models for the regulation of the lac operon often assume complete disruption of LacI-operator complexes upon inducer binding to LacI. Our work shows that even at saturating IPTG there is still a significant population of LacI-DNA complexes in a looped state, in accord with previous in vivo experiments that show incomplete induction (with J. Maher). Finally, we will report progress on characterizing the ``energy landscape'' for DNA looping upon systematic variation of the DNA linkers between the operators and the bending locus. Rod mechanics simulations (with N. Perkins) provide testable predictions on loop stability, topology, and FRET.

Kahn, Jason

2009-03-01

160

Frequency and Phase Lock Loop  

Microsoft Academic Search

A new electronic subsystem has been developed: The frequency and phase lock loop. It has an extended acquisition range compared to the standard phase lock loop. It will be advantageous to use this new loop in all applications where a simultaneous need for large acquisition range and a narrow tracking bandwidth can justify the added complexity of the new loop.

Richard Citta

1977-01-01

161

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

162

Optimum Construction of Heating Coil for Domestic Induction Cooker  

NASA Astrophysics Data System (ADS)

The design and optimization of the parameters of heating coil is very important for the analytical analysis of high frequency inverter fed induction cooker. Moreover, accurate prediction of high frequency winding loss (i.e., losses due to skin and proximity effects) is necessary as the induction cooker used in power electronics applications. At high frequency current penetration in the induction coil circuit is very difficult for conducting wire due to skin-effect. To eradicate the skin effect heating coil is made up of bundle conductor i.e., litz wire. In this paper inductances and AC resistances of a litz-wire are calculated and optimized by considering the input parameters like wire type, shape, number of strand, number of spiral turn, number of twist per feet of heating coil and operating frequency. A high frequency half bridge series resonant mirror inverter circuit is used in this paper and taking the optimum values of inductance and ac resistance the circuit is simulated through PSPICE simulations. It has been noticed that the results are feasible enough for real implementation.

Sinha, Dola; Bandyopadhyay, Atanu; Sadhu, Pradip Kumar; Pal, Nitai

2010-10-01

163

DBSolve Optimum: a software package for kinetic modeling which allows dynamic visualization of simulation results  

PubMed Central

Background Systems biology research and applications require creation, validation, extensive usage of mathematical models and visualization of simulation results by end-users. Our goal is to develop novel method for visualization of simulation results and implement it in simulation software package equipped with the sophisticated mathematical and computational techniques for model development, verification and parameter fitting. Results We present mathematical simulation workbench DBSolve Optimum which is significantly improved and extended successor of well known simulation software DBSolve5. Concept of "dynamic visualization" of simulation results has been developed and implemented in DBSolve Optimum. In framework of the concept graphical objects representing metabolite concentrations and reactions change their volume and shape in accordance to simulation results. This technique is applied to visualize both kinetic response of the model and dependence of its steady state on parameter. The use of the dynamic visualization is illustrated with kinetic model of the Krebs cycle. Conclusion DBSolve Optimum is a user friendly simulation software package that enables to simplify the construction, verification, analysis and visualization of kinetic models. Dynamic visualization tool implemented in the software allows user to animate simulation results and, thereby, present them in more comprehensible mode. DBSolve Optimum and built-in dynamic visualization module is free for both academic and commercial use. It can be downloaded directly from http://www.insysbio.ru.

2010-01-01

164

Robust STATCOM voltage controller design using loop-shaping technique  

Microsoft Academic Search

Static synchronous compensator (STATCOM) is a shunt-connected converter, which can affect rapid control of reactive flow in the transmission line by controlling the generated a.c. voltage. This article presents a robust STATCOM voltage controller design for power system damping. The method of multiplicative uncertainty has been employed to model the variations of the operating points. The design is carried out

A. H. M. A. Rahim; M. F. Kandlawala

2004-01-01

165

Baryon Shape  

SciTech Connect

Using a model based on the relativistic mean-field approach, we address the problem of baryon shape. The best option for unravelling a deviation from spherical symmetry being the study of the {gamma}N{delta} transition, we have evaluated its form factors at Q{sup 2} = 0. Our approach shows explicitly a quadrupolar distortion due to the pion cloud and quark angular momentum. Without any fits, we have obtained in the flavor SU(3) limit and up to the 5-quark level a nice agreement with experimental indications.

Lorce, C. [Departement d'Astrophysique, de Geophysique et d'Oceanographie, Universite de Liege, B5a, Sart-Tilman, B-4000 Liege (Belgium)

2008-08-29

166

Optimum structure with homogeneous optimum cellular material for maximum fundamental frequency  

Microsoft Academic Search

Ultra-light cellular materials exhibit high stiffness\\/strength to weight ratios and bring opportunity for multifunctional\\u000a performance. One of their potential applications is to build structure with optimum dynamic performance, which is extremely\\u000a important for some structural parts in vehicle engineering and attracts a great attention. This paper presents a two-scale\\u000a optimization method and aims at finding optimal configurations of macro structures

Bin Niu; Jun Yan; Gengdong Cheng

2009-01-01

167

The optimum weight of highway noise barriers  

NASA Astrophysics Data System (ADS)

The relative importances were studied of the two major sound paths between a highway and receivers when a noise barrier is interposed: over-barrier sound (i.e., diffracted) and through-barrier sound (i.e., transmitted). The overall insertion loss of the barrier is represented in terms of barrier height (affecting over-barrier sound) and barrier surface mass density (affecting through-barrier sound), the latter involving consideration of the particular incident sound field occurring with traffic noise. A procedure is developed for choosing barrier surface mass density to provide the most noise reduction at least cost. Using data for steel noise barrier cost, this optimum surface mass density is 7.5 to 15 kg/m2 (1.5 to 3 lb/ft2) for barrier heights of 3 to 6 m (10 to 20 ft) respectively. These mass densities are lower than the 20 kg/m2 (4 lb/ft2) currently considered a minimum. Barriers of 7.5 kg/m2 (1.5 lb/ft2) have been built in Ontario and perform satisfactorily. Cost savings are offered the barrier designer through use of this procedure. Now at Wyle Laboratories, 128 Maryland Street, El Segundo, California 90245, U.S.A.

May, D. N.

1980-01-01

168

Achieving optimum diffraction based overlay performance  

NASA Astrophysics Data System (ADS)

Diffraction Based Overlay (DBO) metrology has been shown to have significantly reduced Total Measurement Uncertainty (TMU) compared to Image Based Overlay (IBO), primarily due to having no measurable Tool Induced Shift (TIS). However, the advantages of having no measurable TIS can be outweighed by increased susceptibility to WIS (Wafer Induced Shift) caused by target damage, process non-uniformities and variations. The path to optimum DBO performance lies in having well characterized metrology targets, which are insensitive to process non-uniformities and variations, in combination with optimized recipes which take advantage of advanced DBO designs. In this work we examine the impact of different degrees of process non-uniformity and target damage on DBO measurement gratings and study their impact on overlay measurement accuracy and precision. Multiple wavelength and dual polarization scatterometry are used to characterize the DBO design performance over the range of process variation. In conclusion, we describe the robustness of DBO metrology to target damage and show how to exploit the measurement capability of a multiple wavelength, dual polarization scatterometry tool to ensure the required measurement accuracy for current and future technology nodes.

Leray, Philippe; Laidler, David; Cheng, Shaunee; Coogans, Martyn; Fuchs, Andreas; Ponomarenko, Mariya; van der Schaar, Maurits; Vanoppen, Peter

2010-03-01

169

Moving Shapes to Make Larger Shapes  

NSDL National Science Digital Library

Let\\'s practice playing with different shapes! Move the shape in Hextris to fit the others, once you make a line it goes away. Don\\'t let the shapes fill up the page or you will loose! Rearrange the smaller shapes in Tangram to create a larger picture. In the Geometry Workshop determine how the shapes are moved. ...

Frederick, Mrs.

2008-12-07

170

Loops in twistor space  

SciTech Connect

We elucidate the one-loop twistor-space structure corresponding to momentum-space maximally helicity-violating diagrams. We also discuss the infrared divergences, and argue that only a limited set of maximally helicity-violating diagrams contain them. We show how to introduce a twistor-space regulator corresponding to dimensional regularization for the infrared-divergent diagrams. We also evaluate explicitly the 'holomorphic anomaly' pointed out by Cachazo, Svrcek, and Witten, and use the result to define modified differential operators which can be used to probe the twistor-space structure of one-loop amplitudes.

Bena, Iosif; Bern, Zvi; Kosower, David A.; Roiban, Radu [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States); Service de Physique Theorique, CEA-Saclay F-91191 Gif-sur-Yvette cedex (France); Department of Physics, University of California, Santa Barbara, California 93106 (United States) and Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States)

2005-05-15

171

Smart feedback loops  

NASA Astrophysics Data System (ADS)

It is necessary to find the golden mean in allocating the processing resources of a computer control system. Traditionally, feedback loops operate at the lower levels to ensure safe and stable operation of the accelerator. At present we use analogue and digital feedback loops. Some systems, such as the RF, require more complex algorithms. A possible way of providing these, using digital signal processors is described. The results of tests with the Race-Track Microtron Linac are given and the sources of the main internal and external disturbances have been analysed.

Chepurnov, A. S.; Gribov, I. V.; Gudkov, K. A.; Shumakov, A. V.; Shvedunov, V. I.

1994-12-01

172

Mechanism of formation of loop prominences  

SciTech Connect

Chromospheric gas heated to high temperatures flows into the corona, filling and carrying upward arches of the coronal magnetic field. Under the action of the magnetic tension and gravitation some of the matter included in the field tubes begins to fall back. The magnetic pressure of a magnetic loop which has contracted to its former size prevents the vertical descent of the gas. The retardation of the gas is most substantial at the top of the loop due to the quasi-transverse nature of the field. Here its compression and cooling by emission primarily occur, after which the now visible matter flows away from the condensation point, defining the outlines of the loop. The continuous return to a state of equilibrium of new field tubes containing matter leads to the apparent ascent of the arch structure into the corona. As this happens the ''old'' loops disappear, since the excess gas flows out of them. The ribbon-shaped areas in the chromosphere formed by the descending gas represent two bright filaments on the disk diverging from each other.

Uralov, A.M.; Fedorov, L.V.

1978-07-01

173

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

174

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

175

Numerical computation of human body effects on radiation characteristics of loop antennas for watch-type wrist radiophone applications  

Microsoft Academic Search

Numerical simulation of a full-scale human body model on radiation characteristics of rectangular loop antennas at the wrist position for watch-type radiophone applications is presented. The loop antenna with a superquadric curve is used to model the rectangular loop antenna with rounded comers. The loop antenna may have different position and orientation relative to the wrist. A 3-D realistically shaped

Liang-Chen Kuo; Wen-Tzu Chen; Huey-Ru Chuang

2001-01-01

176

Optimum rotationally symmetric shells for flywheel rotors  

SciTech Connect

A flywheel rim support formed from two shell halves. Each of the shell halves has a disc connected to the central shaft. A first shell element connects to the disc at an interface. A second shell element connects to the first shell element. The second shell element has a plurality of meridional slits. A cylindrical shell element connects to the second shell element. The cylindrical shell element connects to the inner surface of the flywheel rim. A flywheel rim support having a disc connected an outer diameter of a shaft. Two optimally shaped shell elements connect to the optimally shaped disc at an interface. The interface defines a discontinuity in a meridional slope of said support. A cylindrical shell element connects to the two shell elements. The cylindrical shell element has an outer surface for connecting to the inner surface of the flywheel rim. A flywheel rim casing includes an annular shell connected to the central shaft. The annular shell connects to the flywheel rim. A composite shell surrounds the shaft, annular shell and flywheel rim.

Blake, H.W.

2000-04-04

177

Optimum design of a supercavitating torpedo considering overall size, shape, and structural configuration  

Microsoft Academic Search

A supercavitating torpedo is a complex high speed undersea weapon that is exposed to extreme operating conditions due to the weapon’s speed. To successfully design a torpedo that can survive in this environment, it is necessary to consider the torpedo shell as a critical component. The shell of a supercavitating torpedo must be designed to survive extreme loading conditions (depth

Edward Alyanak; Ramana Grandhi; Ravi Penmetsa

2006-01-01

178

Length Distributions in Loop Soups  

NASA Astrophysics Data System (ADS)

Statistical lattice ensembles of loops in three or more dimensions typically have phases in which the longest loops fill a finite fraction of the system. In such phases it is natural to ask about the distribution of loop lengths. We show how to calculate moments of these distributions using CPn-1 or RPn-1 and O(n) ? models together with replica techniques. The resulting joint length distribution for macroscopic loops is Poisson-Dirichlet with a parameter ? fixed by the loop fugacity and by symmetries of the ensemble. We also discuss features of the length distribution for shorter loops, and use numerical simulations to test and illustrate our conclusions.

Nahum, Adam; Chalker, J. T.; Serna, P.; Ortuño, M.; Somoza, A. M.

2013-09-01

179

Closing the Loop Sampler.  

ERIC Educational Resources Information Center

Closing the Loop (CTL) is a science curriculum designed to introduce students to integrated waste management through awareness. This document presents five lesson plans focusing on developing an understanding of natural resources, solid wastes, conservation, and the life of landfills. Contents include: (1) "What Are Natural Resources?"; (2)…

California Integrated Waste Management Board, Sacramento.

180

The inverse loop transform  

Microsoft Academic Search

The loop transform in quantum gauge field theory can be recognized as the Fourier transform (or characteristic functional) of a measure on the space of generalized connections modulo gauge transformations. Since this space is a compact Hausdorff space, conversely, we know from the Riesz-Markov theorem that every positive linear functional on the space of continuous functions thereon qualifies as the

Thomas Thiemann; Max Planck

1998-01-01

181

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

182

Flowcharting loops without cycles  

Microsoft Academic Search

In spite of recent progress in software engineering, many programmers continue to use flowcharting techniques which hamper rather than enhance their ability to create structured programs. This paper describes some of the problems of representing loops with existing techniques and suggests an alternative which solves these problems. The ideas presented here are meant to deal with some of the same

N. H. Weiderman; B. M. Rawson

1975-01-01

183

Loop effects in ?-->?+?-?  

NASA Astrophysics Data System (ADS)

We show that the incorporation of the model consisting of a loop of charged kaons in the description of the ?-->ƒ;0? decay has important effects on the expected signal to background ratio for e+e--->?(?)-->?+?-?. On leave of absence from Escuela Ciencias Físico-Matemáticas, Universidad Autónoma de Sinaloa.

Lucio, J. L. M.; Napsuciale, M.

1994-07-01

184

Closing the Loop Sampler.  

ERIC Educational Resources Information Center

|Closing the Loop (CTL) is a science curriculum designed to introduce students to integrated waste management through awareness. This document presents five lesson plans focusing on developing an understanding of natural resources, solid wastes, conservation, and the life of landfills. Contents include: (1) "What Are Natural Resources?"; (2)…

California Integrated Waste Management Board, Sacramento.

185

Mashup the OODA Loop.  

National Technical Information Service (NTIS)

This paper provides an overview of several Web 2.0 applications and how they can be constructed via mashups to augment current Army Command and Control (C2) processes via the Observe, Orient, Decide, and Act (OODA) Loop concept. As defined by Wikipedia, a...

J. E. Heier

2008-01-01

186

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

187

OMR DEGASIFIER LOOP EXPERIMENT  

Microsoft Academic Search

A loop was constructed to study the removal of water and highly volatile ; materials from Organic Moderated Reactor coolaint by vacuum degasification. An ; analysis of the process was made to determine the effects of pressure, feed rate, ; nozzle pressure drop, and temperature upon degasification efficiency. The rate ; of degasification was quite sensitive to pressure. The other

G. W. Corporales; P. R. Benson

1960-01-01

188

Correlation between Shape of Aggregate and Mechanical Properties of Asphalt Concrete  

Microsoft Academic Search

The importance of the shape of aggregate particles on their mechanical behavior of bituminous materials is well recognized. In asphalt concrete, the shape of aggregate particles affects the durability, workability, shear resistance, tensile strength, stiffness, fatigue response, and optimum binder content of the mixture. In recent years, DIP techniques are widely used to analyze the shape indexes of aggregate. In

Seracettin Arasan; Engin Yenera; Fatih Hattatoglu; Sinan Hinislioglua; Suat Akbuluta

2011-01-01

189

Loop models with crossings  

NASA Astrophysics Data System (ADS)

The universal behavior of two-dimensional loop models can change dramatically when loops are allowed to cross. We study models with crossings both analytically and with extensive Monte Carlo simulations. Our main focus (the “completely packed loop model with crossings”) is a simple generalization of well-known models that shows an interesting phase diagram with continuous phase transitions of a new kind. These separate the unusual “Goldstone” phase observed previously from phases with short loops. Using mappings to Z2 lattice gauge theory, we show that the continuum description of the model is a replica limit of the ? model on real projective space (RPn-1). This field theory sustains Z2 point defects, which proliferate at the transition. In addition to studying the new critical points, we characterize the universal properties of the Goldstone phase in detail, comparing renormalization group (RG) calculations with numerical data on systems of linear size up to L=106 at loop fugacity n=1. (Very large sizes are necessary because of the logarithmic form of correlation functions and other observables.) The model is relevant to polymers on the verge of collapse, and a particular point in parameter space maps to self-avoiding trails at their ? point; we use the RG treatment of a perturbed ? model to resolve some perplexing features in the previous literature on trails. Finally, one of the phase transitions considered here is a close analog of those in disordered electronic systems—specifically, Anderson metal-insulator transitions—and provides a simpler context in which to study the properties of these poorly understood (central-charge-zero) critical points.

Nahum, Adam; Serna, P.; Somoza, A. M.; Ortuño, M.

2013-05-01

190

Myosin-based contraction is not necessary for cardiac c-looping in the chick embryo  

Microsoft Academic Search

During the initial phase of cardiac looping, known as c-looping, the heart bends and twists into a c-shaped tube with the\\u000a convex outer curvature normally directed toward the right side of the embryo. Despite intensive study for more than 80 years,\\u000a the biophysical mechanisms that drive and regulate looping remain poorly understood, although some investigators have speculated\\u000a that differential cytoskeletal

Mathieu C. Rémond; Judy A. Fee; Elliot L. Elson; Larry A. Taber

2006-01-01

191

The ROSAT HRI X-Ray Survey of the Cygnus Loop  

Microsoft Academic Search

We describe and report progress on the joint U.S. and German campaign to map the X-ray emission from the entire Cygnus Loop with the ROSAT High Resolution Imager. The Cygnus Loop is the prototype for a supernova remnant that is dominated by interactions with the interstellar medium and supplies fundamental physical information on this basic mechanism for shaping the interstellar

N. A. Levenson; J. R. Graham; B. Aschenbach; W. P. Blair; W. Brinkmann; J.-U. Busser; R. Egger; R. A. Fesen; J. J. Hester; S. M. Kahn; R. I. Klein; C. F. McKee; R. Petre; R. Pisarski; J. C. Raymond; S. L. Snowden

1997-01-01

192

Characteristics of wideband ring loop antenna for digital terrestrial broadcasting  

Microsoft Academic Search

In the transmitting and receiving antenna for the UHF band broadcasting, the requirements of the antenna are wideband linear polarization characteristics. It is possible to make a wideband antenna using the loop antenna, arranged vertically, with a circumference length about one wavelength. Miniaturization becomes possible in a simple shape by the realization of a wideband and high-gain linearly polarized ring

H. Kawakami; T. Haga; S. Kon

2005-01-01

193

COLD TEST LOOP INTEGRATED TEST LOOP RESULTS  

SciTech Connect

A testing facility (Cold Test Loop) was constructed and operated to demonstrate the efficacy of the Accelerated Waste Retrieval (AWR) Project's planned sluicing approach to the remediation of Silos 1 and 2 at the Fernald Environmental Management Project near Cincinnati, Ohio. The two silos contain almost 10,000 tons of radium-bearing low-level waste, which consists primarily of solids of raffinates from processing performed on ores from the Democratic Republic of Congo (commonly referred to as ''Belgium Congo ores'') for the recovery of uranium. These silos are 80 ft in diameter, 36 ft high to the center of the dome, and 26.75 ft to the top of the vertical side walls. The test facility contained two test systems, each designed for a specific purpose. The first system, the Integrated Test Loop (ITL), a near-full-scale plant including the actual equipment to be installed at the Fernald Site, was designed to demonstrate the sluicing operation and confirm the selection of a slurry pump, the optimal sluicing nozzle operation, and the preliminary design material balance. The second system, the Component Test Loop (CTL), was designed to evaluate many of the key individual components of the waste retrieval system over an extended run. The major results of the initial testing performed during July and August 2002 confirmed that the AWR approach to sluicing was feasible. The ITL testing confirmed the following: (1) The selected slurry pump (Hazleton 3-20 type SHW) performed well and is suitable for AWR application. However, the pump's motor should be upgraded to a 200-hp model and be driven by a 150-hp variable-frequency drive (VFD). A 200-hp VFD is not much more expensive and would allow the pump to operate at full speed. (2) The best nozzle performance was achieved by using 15/16-in. nozzles operated alternately. This configuration appeared to most effectively mine the surrogate. (3) The Solartron densitometer, which was tested as an alternative mass flow measurement device, did not operate effectively. Consequently, it is not suitable for application to the AWR process. (4) Initially, the spray ring (operated at approximately 2300 psi) and the nozzles provided by the pump vendor did not perform acceptably. The nozzles were replaced with a more robust model, and the performance was then acceptable. (5) The average solids concentration achieved in the slurry before Bentogrout addition was approximately 16% by weight. The solids concentration of the slurry after Bentogrout addition ranged from 26% to approximately 40%. The slurry pump and ITL system performed well at every concentration. No line plugging or other problems were noted. The results of the CTL runs and later ITL testing are summarized in an appendix to this report.

Abraham, TJ

2003-10-22

194

Shape Classification Using a Flexible Graph Kernel  

NASA Astrophysics Data System (ADS)

The medial axis being an homotopic transformation, the skeleton of a 2D shape corresponds to a planar graph having one face for each hole of the shape and one node for each junction or extremity of the branches. This graph is non simple since it can be composed of loops and multiple-edges. Within the shape comparison framework, such a graph is usually transformed into a simpler structure such as a tree or a simple graph hereby loosing major information about the shape. In this paper, we propose a graph kernel combining a kernel between bags of trails and a kernel between faces. The trails are defined within the original complex graph and the kernel between trails is enforced by an edition process. The kernel between bags of faces allows to put an emphasis on the holes of the shapes and hence on their genre. The resulting graph kernel is positive semi-definite on the graph domain.

Dupé, François-Xavier; Brun, Luc

195

OPTIMUM DESIGN OF THIN-PLATED STEEL BOX COLUMNS  

Microsoft Academic Search

This paper deals with the optimum design of thin-plated box columns subjected to axial thrust and biaxial end moments. Design formulae based on an effective width approach, proposed by the authors, are utilized in the optimization studies. The problem is first viewed as a strength maximization problem in which the optimum plate slenderness is evaluated for columns having constant weight

J. Y. RICHARD LIEW; NANDIVARAM E. SHANMUGAM; SENG-LIP LEE

1990-01-01

196

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

197

Reliability-Based Optimum Design of Simple Plastic Frames.  

National Technical Information Service (NTIS)

Reliability analysis and optimum reliability-based design are discussed and illustrated in this report. A new iterative optimization scheme is exploited where at each stage of the design process both upper and lower bounds on the true optimum value of the...

E. H. Vanmarcke J. Diaz-Padilla D. A. Roth

1972-01-01

198

Research of Weighting Circuits for the Design of Optimum Beamforming  

Microsoft Academic Search

In underwater acoustic detection system, the performance of the system is greatly affected by beamforming techniques. For that reason, the design of optimum beamforming has been studied for a long time by many researchers. Weighting circuits are necessary to implement an optimum beamformer. In this paper, we introduce an array design software. It consists beampattern design tool(BeamCAD Tool), equivalent circuit

Nakjin Choi; Koeng-Mo Sung; Jun-seok Lim

199

Optimum College Admissions, Taxes and Tuitions When Completion Is Uncertain.  

ERIC Educational Resources Information Center

|Explores the rationale for college subsidies in most world economies, treating precollege achievement as an insurable risk. Contract theory considers optimum insurance contracts for this risk and views public finance of college education as providing the insurance. The theory yields conditions on optimum taxes and fees. Rationing by…

Garratt, Rod; Marshall, John M.

1995-01-01

200

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

201

Optimum design for reversible water–water heat pumps  

Microsoft Academic Search

The optimum energy consumption in an air conditioning system depends on many factors. Some of these are the following: the use of high performance devices, the utilization of these in the optimum efficiency range, a correct control strategy, a proper maintenance, etc.In air conditioning facilities most of the energy consumption corresponds to the thermal production, this being heat and cold.

C. J. Renedo; A. Ortiz; M. Mañana; J. Peredo

2006-01-01

202

Ground loops detection system in the RFX machine  

SciTech Connect

RFX is a toroidal machine for the fusion research based on the RFP configuration. During the pulse, in any conductive loop close to the machine very strong currents can be induced, which may damage the diagnostics and the other instrumentation. To avoid loops, the earthing system of the machine is tree-shaped. However, an accidental contact between metallic earthed masses of the machine may give rise to an unwanted loop as well. An automatic system for the detection of ground loops in the earthing system has therefore been developed, which works continuously during shutdown intervals and between pulses. In the paper the design of the detection system is presented, together with the experimental results on prototypes. 4 refs., 3 figs., 1 tab.

Bellina, F.; Pomaro, N. [ENEA-CNR-Uniersita di Padova (Italy); Trevisan, F. [Universita di Udine (Italy)

1996-12-31

203

Closed loop control of heliostats  

Microsoft Academic Search

Tracking control in current heliostats is performed with an open loop, without any verification that the radiation is actually arriving at the desired target. Errors due to open-loop tracking control are often around 1–2 mrad and can accumulate during operation. A significant reduction of tracking error by closing the control loop is presented. The method includes a dynamic measurement of

Abraham Kribus; Irina Vishnevetsky; Amnon Yogev; Tatiana Rubinov

2004-01-01

204

Service in a Loop System  

Microsoft Academic Search

The statistical behavior of a loop service system is studied. The system consists of a main station, a server and N stations arranged on a loop. Customers arrive at each station according to a random process. The server makes successive tours along the loop bringing customers from the N stations to the main station. Two related measures of the grade

Alan G. Konheim; Bernd Meister

1972-01-01

205

Getting Your Loops Straight  

NSDL National Science Digital Library

This article introduces a special issue on the study of biochemical signaling pathways. Complicated biochemical signaling pathways regulate the function of living cells. Such regulatory networks often have âÂÂdownstreamâ components that provide input to components that act earlier in a pathway, creating feedback loops. These feedback loops have the potential to greatly alter the properties of a pathway and how it responds to stimuli. To fully understand these regulatory systems and exploit their vast potential as targets of therapeutic strategies, we need quantitative information on the flow of signals through a pathway and on the timing and location of signaling events within cells. The papers assembled in this special issue and in the companion issue of Science Signaling highlight recent progress in tackling these challenges.

L. Bryan Ray (AAAS;)

2008-10-17

206

A Generalized Theory of DNA Looping and Cyclization  

NASA Astrophysics Data System (ADS)

We have developed a semi-analytic method for calculating the Stockmayer Jacobson J-factor for protein mediated DNA loops. The formation of DNA loops on the order of a few persistence lengths is a key component in many biological regulatory functions. The binding of LacI protein within the Lac Operon of E.coli serves as the canonical example for loop regulated transcription. We use a non-linear rod model to determine the equilibrium shape of the inter-operator DNA loop under prescribed binding constraints while taking sequence-dependent curvature and elasticity into account. Then we construct a Hamiltonian that describes thermal fluctuations about the open and looped equilibrium states, yielding the entropic and enthalpic costs of loop formation. Our work demonstrates that even for short sequences of the order one persistence length, entropic terms contribute substantially to the J factor. We also show that entropic considerations are able to determine the most favorable binding topology. The J factor can be used to compare the relative loop lifetimes of various DNA sequences, making it a useful tool in sequence design. A corollary of this work is the computation of an effective torsional persistence length, which demonstrates how torsion bending coupling in a constrained geometry affects the conversion of writhe to twist.

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

2010-03-01

207

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

208

Closing the loop.  

PubMed

The dream of closing the loop is actually the dream of creating an artificial pancreas and freeing the patients from being involved with the care of their own diabetes. Insulin-dependent diabetes (type 1) is a chronic incurable disease which requires constant therapy without the possibility of any 'holidays' or insulin-free days. It means that patients have to inject insulin every day of their life, several times per day, and in order to do it safely they also have to measure their blood glucose levels several times per day. Patients need to plan their meals, their physical activities and their insulin regime - there is only very small room for spontaneous activities. This is why the desire for an artificial pancreas is so strong despite the fact that it will not cure the diabetic patients. Attempts to develop a closed-loop system started in the 1960s but never got to a clinical practical stage of development. In recent years the availability of continuous glucose sensors revived those efforts and stimulated the clinician and researchers to believe that closing the loop might be possible nowadays. Many papers have been published over the years describing several different ideas on how to close the loop. Most of the suggested systems have a sensing arm that measures the blood glucose repeatedly or continuously, an insulin delivery arm that injects insulin upon command and a computer that makes the decisions of when and how much insulin to deliver. The differences between the various published systems in the literature are mainly in their control algorithms. However, there are also differences related to the method and site of glucose measurement and insulin delivery. SC glucose measurements and insulin delivery are the most studied option but other combinations of insulin measurements and glucose delivery including intravascular and intraperitoneal (IP) are explored. We tried to select recent publications that we believe had influenced and inspired people interested in the field. PMID:20377660

Dassau, E; Atlas, E; Phillip, M

2010-02-01

209

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

210

Physical mechanisms redirecting cell polarity and cell shape  

PubMed Central

Summary The fission yeast Schizosaccharomyces pombe has a cylindrical rod-shape that is organized and maintained by interactions between the microtubule, cell membrane, and actin cytoskeleton; i.e., microtubules deliver factors to the cell tips that subsequently recruit the actin machinery to direct localized cell growth [1]. Mutations affecting any components in this pathway lead to bent, branched, or round cells [2]. In this context, the cytoskeleton controls cell polarity and thus dictates cell shape. Here, we use soft-lithography techniques to construct microfluidic channels in order to control the shape of cells. We show that by physically forcing wildtype rod-shaped cells to grow bent, they will re-organize their cytoskeleton and re-direct cell polarity to make new ectopic cell tips. In addition, by physically forcing bent or round mutant cells to conform to the wildtype rod-shape, cells will reverse their mutational phenotypes by re-organizing their cytoskeleton to maintain proper wildtype-like microtubule, cell membrane proteins, and actin localizations. Our study provides direct evidence that the cytoskeleton controls cell polarity and cell shape and demonstrates that cell shape also controls the organization of the cytoskeleton, in a feedback loop. We present a model of the feedback loop which explains how fission yeast cells maintain a rod-shape, and how perturbation of specific parameters of the loop can lead to different cell shapes.

Terenna, Courtney R.; Makushok, Tatyana; Velve-Casquillas, Guilhem; Baigl, Damien; Chen, Yong; Bornens, Michel; Paoletti, Anne; Piel, Matthieu; Tran, Phong T.

2010-01-01

211

Optimum Strategy for Ex-Core Dosimeters/monitors in the IRIS Reactor  

NASA Astrophysics Data System (ADS)

International Reactor Innovative and Secure (IRIS) is a medium-power (~300 MWe) advanced light water reactor that features an integral primary system configuration to enhance safety. Steam generators are located inside the pressure vessel above the core, forming a thick (~1.68 m) annular region, that extends into an equally thick downcomer surrounding the core. As a result, neutron fluence at the pressure vessel and in the cavity is reduced by 5-6 orders of magnitude relative to present loop-type Pressurized Water Reactors (PWRs). Reduction of the RPV fluence eliminates embrittlement concerns, but introduces new challenges for the ex-core flux monitors. This paper proposes using advanced flux monitors, such as SiC semiconductor neutron detectors, and examines their optimum placement in the downcomer region. Furthermore, the requirements on neutron dosimetry/monitors considered for the IRIS-reactor are common to Generation-IV Integral Primary System Reactors (IPSRs).

Petrovi?, Bojan; Ruddy, Frank H.; Lombardi, Carlo

2003-06-01

212

Optimum heat release for a reciprocating internal combustion engine  

SciTech Connect

The problem of finding the cylinder pressure trace which maximizes engine efficiency is formulated in terms of cylinder pressure-dependent frictional, heat, and mass losses. The governing equations are recast into a form to which optimal control theory can be applied, and the pressure trace together with the corresponding optimum heat release profile which yield maximum efficiency are found. Results for optimum heat release are compared to results for both conventional rates of heat release and for the theoretical Otto cycle, and show that significant gains in efficiency are possible if the optimum heat release is employed.

Hoppie, L.O.; Min, Y.K.; Srinivasan, N.; Wu, S.H.

1987-01-01

213

Theoretical modelling of miniature loop heat pipe  

NASA Astrophysics Data System (ADS)

Development in the design and thermal performance of the loop heat pipes (LHPs) demands the corresponding improvement in the theoretical modeling capabilities of these devices. In this paper, mathematical model for assessing the thermal performance of the miniature LHPs (mLHPs) on the basis of the operating temperature and thermal resistance of the loop has been discussed in detail. In order to validate the theoretical model, a mLHP with the flat disk shaped evaporator, 30 mm in diameter and 10 mm thick, was developed and tested with nickel and copper wick structure. By comparison with experimental results, it was found that the theoretical model was able to predict the evaporator temperature and loop thermal resistance very well and within the uncertainties imposed by the underlying assumptions. The mathematical model can be used to validate the design of the mLHP and verify whether the proposed design is consistent with the maximum heat load capacity required for the intended application. In addition to this, the model can assists in understanding and refining the outcomes of the experimental studies.

Singh, Randeep; Akbarzadeh, Aliakbar; Dixon, Chris; Mochizuki, Masataka

2009-12-01

214

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

215

SHAPES and PATTERNS  

NSDL National Science Digital Library

Students will be working with extending a pattern, making shapes and comparing shapes! MATH IS FUN and lets have some fun with patterns! Click to begin: Making Patterns Now that we have worked with patterns, lets work on our shapes. The world is made up of shapes everywhere! Click to begin:Comparing Shapes to the Real World You have now seen that the world is full of shapes, lets make some shapes of ...

Simpson, Ms.

2007-10-29

216

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

217

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

218

On the optimum polarizations of incoherently reflected waves  

NASA Astrophysics Data System (ADS)

The Stokes scattering operator is noted to be the most useful characterization of incoherent scattering in radar imaging; the polarization that would yield an optimum amount of power received from the scatterer is obtained by assuming a knowledge of the Stokes scattering operator instead of the 2x2 scattering matrix with complex elements. It is thereby possible to find the optimum polarizations for the case in which the scatterers can only be fully characterized by their Stokes scattering operator, and the case in which the scatterer can be fully characterized by the complex 2x2 scattering matrix. It is shown that the optimum polarizations reported in the literature form the solution for a subset of a more general class of problems, so that six optimum polarizations can exist for incoherent scattering.

van Zyl, Jakob J.; Elachi, Charles; Papas, Charles H.

1987-07-01

219

Tactical Fighter Employment: The Optimum Role in Contingency Operations.  

National Technical Information Service (NTIS)

This study determines if an optimum role for tactical fighters exists in Contingency Operations, (formerly known as Peacetime Contingency Operations) a form of Low Intensity Conflict (LIC). This report traces the historical development of the terminology ...

M. A. Snodgrass

1991-01-01

220

Optimum Testing of Multiple Hypotheses in Quantum Detection Theory.  

National Technical Information Service (NTIS)

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 s...

H. P. Yuen R. S. Kennedy M. Lax

1974-01-01

221

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

222

Automatic construction of statistical shape models for vertebrae.  

PubMed

For segmenting complex structures like vertebrae, a priori knowledge by means of statistical shape models (SSMs) is often incorporated. One of the main challenges using SSMs is the solution of the correspondence problem. In this work we present a generic automated approach for solving the correspondence problem for vertebrae. We determine two closed loops on a reference shape and propagate them consistently to the remaining shapes of the training set. Then every shape is cut along these loops and parameterized to a rectangle. There, we optimize a novel combined energy to establish the correspondences and to reduce the unavoidable area and angle distortion. Finally, we present an adaptive resampling method to achieve a good shape representation. A qualitative and quantitative evaluation shows that using our method we can generate SSMs of higher quality than the ICP approach. PMID:21995066

Becker, Meike; Kirschner, Matthias; Fuhrmann, Simon; Wesarg, Stefan

2011-01-01

223

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 cryoprotective agent often\\u000a requires rather tedious, time consuming and repetitive tests. Integrating the functions of sample preparation and viability\\u000a detection, the concept of biochip technology was introduced to the field of cryopreservation, aiming at quickly finding an\\u000a optimum freezing and thawing program. Prototype devices were fabricated

Lina Yu; Jing Liu; Yixin Zhou; Zezhao Hua

2007-01-01

224

Optimum simple step-stress accelerated life tests with censoring  

Microsoft Academic Search

The authors present the optimum simple time-step and failure-step stress accelerated life tests for the case where a prespecified censoring time is involved. An exponential life distribution with a mean that is a log-linear function of stress, and a cumulative exposure model are assumed. The authors obtain the optimum test plans to minimize the asymptotic variance of the maximum-likelihood estimator

D. S. Bai; M. S. Kim; S. H. Lee

1989-01-01

225

Plasticity of 150-loop in influenza neuraminidase explored by Hamiltonian replica exchange molecular dynamics simulations.  

PubMed

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. PMID:23593372

Han, Nanyu; Mu, Yuguang

2013-04-10

226

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

227

Resultants and loop closure  

NASA Astrophysics Data System (ADS)

The problem of tripeptide loop closure is formulated in terms of the angles {?i} 3i=1 describing the orientation of each peptide unit about the virtual axis joining the C? atoms. Imposing the constraint that at the junction of two such units the bond angle between the bonds C??N and C??C is fixed at some prescribed value ? results in a system of three bivariate polynomials in ui ? tan ?i/2 of degree 2 in each variable. The system is analyzed for the existence of common solutions by making use of resultants, determinants of matrices composed of the coefficients of two (or more) polynomials, whose vanishing is a necessary and sufficient condition for the polynomials to have a common root. Two resultants are compared: the classical Sylvester resultant and the Dixon resultant. It is shown that when two of the variables are eliminated in favor of the third, a polynomial of degree 16 results. To each one of its real roots, there is a corresponding common zero of the system. To each such zero, there corresponds a consistent conformation of the chain. The Sylvester method can find these zeros among the eigenvalues of a 24 × 24 matrix. For the Dixon approach, after removing extraneous factors, an optimally sized eigenvalue problem of size 16 × 16 results. Finally, the easy extension to the more general problem of triaxial loop closure is presented and an algorithm for implementing the method on arbitrary chains is given.

Coutsias, Evangelos A.; Seok, Chaok; Wester, Michael J.; Dill, Ken A.

228

Fluorescence resonance energy transfer over approximately 130 basepairs in hyperstable lac repressor-DNA loops.  

PubMed

Lac repressor (LacI) binds two operator DNA sites, looping the intervening DNA. DNA molecules containing two lac operators bracketing a sequence-directed bend were previously shown to form hyperstable LacI-looped complexes. Biochemical studies suggested that orienting the operators outward relative to the bend direction (in construct 9C14) stabilizes a positively supercoiled closed form, with a V-shaped LacI, but that the most stable loop construct (11C12) is a more open form. Here, fluorescence resonance energy transfer (FRET) is measured on DNA loops, between fluorescein and TAMRA attached near the two operators, approximately 130 basepairs apart. For 9C14, efficient LacI-induced energy transfer ( approximately 74% based on donor quenching) confirms that the designed DNA shape can force the looped complex into a closed form. From enhanced acceptor emission, correcting for observed donor-dependent quenching of acceptor fluorescence, approximately 52% transfer was observed. Time-resolved FRET suggests that this complex exists in both closed- and open form populations. Less efficient transfer, approximately 10%, was detected for DNA-LacI sandwiches and 11C12-LacI, consistent with an open form loop. This demonstration of long-range FRET in large DNA loops confirms that appropriate DNA design can control loop geometry. LacI flexibility may allow it to maintain looping with other proteins bound or under different intracellular conditions. PMID:12547794

Edelman, Laurence M; Cheong, Raymond; Kahn, Jason D

2003-02-01

229

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

230

Plasma shape experiments for an optimized tokamak  

SciTech Connect

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. 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} 1.8 and 2.1) and low and high triangularities ({delta} {congruent} 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} {equivalent_to} {beta}/(I{sup p})/aB{sub T} and H {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. [General Atomics, San Diego, CA (United States); Lazarus, E.A. [Oak Ridge National Lab., TN (United States)

1994-07-01

231

Loop-the-Loop: Bringing Theory into Practice  

ERIC Educational Resources Information Center

|During the Thai high-school physics teacher training programme, we used an aluminum loop-the-loop system built by the Institute for the Promotion of Teaching Science and Technology (IPST) to demonstrate a circular motion and investigate the concept of the conservation of mechanical energy. There were 27 high-school teachers from three provinces,…

Suwonjandee, N.; Asavapibhop, B.

2012-01-01

232

Loop-the-Loop: Bringing Theory into Practice  

ERIC Educational Resources Information Center

During the Thai high-school physics teacher training programme, we used an aluminum loop-the-loop system built by the Institute for the Promotion of Teaching Science and Technology (IPST) to demonstrate a circular motion and investigate the concept of the conservation of mechanical energy. There were 27 high-school teachers from three provinces,…

Suwonjandee, N.; Asavapibhop, B.

2012-01-01

233

Loop-the-Loop: An Easy Experiment, A Challenging Explanation  

NASA Astrophysics Data System (ADS)

A loop-the-loop built by the Institute for the Promotion of Teaching Science and Technology (IPST) was used in Thai high school teachers training program to demonstrate a circular motion and investigate the concept of the conservation of mechanical energy. We took videos using high speed camera to record the motions of a spherical steel ball moving down the aluminum inclined track at different released positions. The ball then moved into the circular loop and underwent a projectile motion upon leaving the track. We then asked the teachers to predict the landing position of the ball if we changed the height of the whole loop-the-loop system. We also analyzed the videos using Tracker, a video analysis software. It turned out that most teachers did not realize the effect of the friction between the ball and the track and could not obtain the correct relationship hence their predictions were inconsistent with the actual landing positions of the ball.

Asavapibhop, B.; Suwonjandee, N.

2010-07-01

234

Phase-Locked Loops  

NSDL National Science Digital Library

Phase-locked loops (PLL) are unique feedback control circuits that offer many useful features and benefits in electronic applications. PLLs are available either in integrated circuit (IC) form for general applications or built into larger system IC chips. Today, PLLs are found in virtually all types of electronic equipment from PCs to consumer products like TV sets and cell phones. This module provides an introduction to the PLL and its applications. It begins with an overview of the main components of a PLL and how these components work together. It then describes PLL specifications and a description of the most widely used applications including frequency synthesizers, clock multipliers, clock and data recovery circuits, FM demodulators, and filters.

2012-09-06

235

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

236

Computer simulation of feedback loops  

Microsoft Academic Search

The effect of the sampling rate on the behavior of computer simulated phase locked loops (PLL) is studied. The choice of integrators used in feedback systems is also analyzed. The performance degradation of the first order loop is obtained analytically, and verified by simulation on the Block Oriented Systems Simulator, BOSS. A bound on the allowable sampling rate is obtained

J. Fernandez; B. Hinton; J. Holtzman

1990-01-01

237

The Projectile Inside the Loop  

ERIC Educational Resources Information Center

|The loop-the-loop demonstration can be easily adapted to study the kinematics of projectile motion, when the moving body falls inside the apparatus. Video capturing software can be used to reveal peculiar geometrical effects of this simple but educational experiment.|

Varieschi, Gabriele U.

2006-01-01

238

The projectile inside the loop  

NASA Astrophysics Data System (ADS)

The loop-the-loop demonstration can be easily adapted to study the kinematics of projectile motion, when the moving body falls inside the apparatus. Video capturing software can be used to reveal peculiar geometrical effects of this simple but educational experiment.

Varieschi, Gabriele U.

2006-03-01

239

Optimum Tuning of a Slow Sampling Digital Control Algorithm.  

National Technical Information Service (NTIS)

The selection of control algorithms for direct digital control loops is a degree more difficult than the selection of continuous analog controllers, primarily because analog hardware considerations limit the selection to proportional, proportional-integra...

A. M. Lopez P. W. Murrill C. L. Smith

1969-01-01

240

Heating of braided coronal loops  

NASA Astrophysics Data System (ADS)

Aims: We investigate the relaxation of braided magnetic loops in order to find out how the type of braiding via footpoint motions affects resultant heating of the loop. Methods: Two magnetic loops, braided in different ways, are used as initial conditions in resistive MHD simulations and their subsequent evolution is studied. Results: The fields both undergo a resistive relaxation in which current sheets form and fragment and the system evolves towards a state of lower energy. In one case this relaxation is very efficient with current sheets filling the volume and homogeneous heating of the loop occurring. In the other case fewer current sheets develop, less magnetic energy is released in the process and a patchy heating of the loop results. The two cases, although very similar in their setup, can be distinguished by the mixing properties of the photospheric driver. The mixing can be measured by the topological entropy of the plasma flow, an observable quantity.

Wilmot-Smith, A. L.; Pontin, D. I.; Yeates, A. R.; Hornig, G.

2011-12-01

241

Coronal Loop detection and seismology  

NASA Astrophysics Data System (ADS)

Using a TRACE image with a bipolar active region and over one hundred distinguishable loops, we examine several current methods for automated coronal loop detection. Using the same TRACE image, several new approaches are also taken in an attempt to increase accuracy and completeness rates for the automated detection process. By means of these new methods the expectation is to achieve a higher degree of completeness while maintaining a high level of accuracy in the detection process. To increase completeness, an automated attempt for the reconnection between orphaned loop segments will also be tested. In the future, an approach to reconstruction of three-dimensional images from several two-dimensional images can be devised by using the detected coronal loops and a known 3D offset of each image. However this process heavily depends on the ability to accurately and completely detect the coronal loops.

Pevtsov, Alexander; McAteer, R. T. J.; Jackiewicz, J.; Kirk, M.; McNamara, B.; DeGrave, K.; Amani Al-Ghraibah, A.; Boucheron, L.; Voelz, D.; Cao, H.; Taylor, G.

2011-05-01

242

Coronal Loop detection and seismology  

NASA Astrophysics Data System (ADS)

Using a TRACE image with a bipolar active region and over one hundred distinguishable loops, we examine several current methods for automated coronal loop detection. Using the same TRACE image, several new approaches are also taken in an attempt to increase accuracy and completeness rates for the automated detection process. These new methods are applied to AIA data from the Solar Dynamic Observatory with the expectation to achieve a higher degree of completeness while maintaining a high level of accuracy in the detection process. To increase completeness, an automated attempt for the reconnection between orphaned loop segments will also be tested. In the future, an approach to reconstruction of three-dimensional images from several two-dimensional images can be devised by using the detected coronal loops and a known 3D offset of each image. However this process heavily depends on the ability to accurately and completely detect the coronal loops.

Pevtsov, Alexander; McAteer, R. T. J.; Jackiewicz, Jason; Calabro, Brandon; McNamara, Bernie

2011-10-01

243

Scaling of cosmic string loops  

SciTech Connect

We study the spectrum of loops as a part of a complete network of cosmic strings in flat spacetime. After a long transient regime, characterized by production of small loops at the scale of the initial conditions, it appears that a true scaling regime takes over. In this final regime the characteristic length of loops scales as 0.1t, in contrast to earlier simulations which found tiny loops. We expect the expanding-universe behavior to be qualitatively similar. If this expectation is correct, then the large loop sizes have important cosmological implications. In particular, the nucleosynthesis bound then becomes G{mu} < or approx. 10{sup -7}, much tighter than that obtained from earlier analyses.

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

2006-09-15

244

Brightness and blue-shift of chromospheric foot-points of coronal loops in pre-flare phase  

Microsoft Academic Search

A phenomenon of the brightness and blue shift of chromospheric foot-points of coronal loops in pre-flare phase observed by the Fine Structure Telescope of Yunnan Observatory, is reported. The 4 foot-points of two coronal loops were confirmed by Yohkoh\\/HXT\\/SXT observations. In the pre-flare phase, the separated point-shaped bright chromospheric plages, which are counterparts of the foot-points of the coronal loops

Heng Zhang; Di Luan

1999-01-01

245

24—ANALYSIS OF THE DRY-RELAXED KNITTED-LOOP CONFIGURATION: PART I: TWO-DIMENSIONAL ANALYSIS  

Microsoft Academic Search

Models of the relaxed plain-knit structure proposed by previous workers suffer from the disadvantage of being based on the assumption of some geometrical shape for the knitted loop and are not derived from equilibrium considerations of the forces and couples applied to one loop by its neighbours. In the work described in this paper, the dry-relaxed knitted-loop configuration is considered

R. Postle; D. L. Munden

1967-01-01

246

Determining the Optimum Number of Increments in Composite Sampling  

SciTech Connect

Composite sampling can be more cost effective than simple random sampling. This paper considers how to determine the optimum number of increments to use in composite sampling. Composite sampling can be more cost effective than simple random sampling. This paper considers how to determine the optimum number of increments to use in composite sampling. Composite sampling terminology and theory are outlined and a method is developed which accounts for different sources of variation in compositing and data analysis. This method is used to define and understand the process of determining the optimum number of increments that should be used in forming a composite. The blending variance is shown to have a smaller range of possible values than previously reported when estimating the number of increments in a composite sample. Accounting for differing levels of the blending variance significantly affects the estimated number of increments.

Hathaway, John E.; Schaalje, G Bruce; Gilbert, Richard O.; Pulsipher, Brent A.; Matzke, Brett D.

2008-09-30

247

Tool Geometry for Friction Stir Welding—Optimum Shoulder Diameter  

NASA Astrophysics Data System (ADS)

The most important geometric parameter in the friction stir welding (FSW) tool design is the shoulder diameter, which is currently estimated by trial and error. Here, we report a combined experimental and theoretical investigation on the influence of shoulder diameter on thermal cycles, peak temperatures, power requirements, and torque during FSW of AA7075-T6. An optimum tool shoulder diameter is identified using a three-dimensional, heat transfer and materials flow model. First, the predictive capability of the model is tested by comparing the computed values of peak temperature, spindle power, and torque requirements for various shoulder diameters against the corresponding experimental data. The change in the values of these variables with shoulder diameter is correctly predicted by the model. The model is then used to identify the optimum tool shoulder diameter that facilitates maximal use of the supplied torque in overcoming interfacial sticking. The tool with optimum shoulder diameter is shown to result in acceptable yield strength (YS) and ductility.

Mehta, M.; Arora, A.; de, A.; Debroy, T.

2011-09-01

248

Bag of Shapes  

NSDL National Science Digital Library

Students are given a bag containing two different shapes and asked to find the shape in the bag with certain attributes, to trace the shape on a piece of paper, and to write the name of the shape and a description of its attributes.

Sherdan, Danielle

2010-07-21

249

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

250

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

251

Oversampling A-to-D and D-to-A converters with multistage noise shaping modulators  

Microsoft Academic Search

High-resolution oversampling analog-to-digital-to-analog converters are proposed. The converters utilize multistage noise shaping modulation techniques that can be implemented with VLSI MOS technology. The modulators consist of multiconnected single-integration delta-sigma modulation loops. Quantization noise in the first delta-sigma loop is requantized by the next delta-sigma loop and cancelled by adding the requantized noise to the first-stage signal. Quantization noise in the

KUNIHARU UCHIMURA; TOSHIO HAYASHI; T. Kimura; A. Iwata

1988-01-01

252

Feedback compensation of shape memory alloy hysteresis  

NASA Astrophysics Data System (ADS)

Traditionally, actuators have been large and heavy (eg., motors). Because of their physical size and structure, they increase the size and weight of the entire system. In many applications, it is desirable to find an alternative to these conventional type of actuators. Shape memory alloy (SMA) has been considered as an actuator for applications that require large force and displacement. SMA are small and light weight which greatly reduces the overall size of a system. However, two factors have hampered the usefulness of such actuators, hysteresis and bandwidth limitation. This thesis examines the hysteresis phenomenon from a control point of view. Particular focus is placed on SMA wires attached to a flexible structure. Generally speaking, there are two ways to compensate for hysteresis, open loop compensation and closed loop feedback compensation. The open loop compensation requires an accurate model; this thesis uses a closed loop approach which considers the feedback of the SMA wire force or length. Very little previous work exists in the literature in this area since most researchers consider SMA to be essentially a static device. However even at low bandwidths, SMA cannot be considered a static device due in part to its intrinsic hysteretic properties. By using a simple lumped temperature model, it is shown that proportional feedback with a suitable range of gains would render the closed loop system stable. This is verified experimentally in a simple experimental setup consisting of a flexible aluminum beam and to a Nitinol shape memory alloy wire that applies it bending force to the end of the beam.

Dickinson, Carrie A.

253

Hydrofoils: optimum lift-off speed for sailboats.  

PubMed

For a hydrofoil sailboat there is a unique optimum lift-off speed. Before this speed is reached, if there are no parasitic vertical hydrofoil appendages, the submerged or partially submerged hydrofoils increase drag and degrade performance. As soon as this speed is reached and the hydrofoils are fully and promptly deployed, the performance of a hydrofoil-borne craft is significantly improved. At speeds exceeding optimum lift-off speed, partially submerged hydrofoils impair performance if there is no significant effect of loading on the hydrofoil lift-to-drag ratio. PMID:17756335

Baker, R M

1968-12-13

254

Significance of Quality Control of Liner-Wall Symmetry on Shaped Charge Perforator Performance  

Microsoft Academic Search

The objectives of this paper are to demonstrate experimentally the significance of liner-wall mass uniformity and concentricity on the penetrating effectiveness (total target penetration and target hole size and symmetry) of conical shaped charges and to devise a systematic approach for selecting the optimum manufacturing conditions for the production of acceptably uniform shaped-charge liners. Experimental results indicated that total target

Ifiyenia Kececioglu

1991-01-01

255

Wilson loops T-dual to short strings  

NASA Astrophysics Data System (ADS)

We show that closed string solutions in the bulk of AdS space are related by T-duality to solutions representing an open string ending at the boundary of AdS. By combining the limit in which a closed string becomes small with a large boost, we find that the near-flat space short string in the bulk maps to a periodic open string world surface ending on a wavy line at the boundary. This open string solution was previously found by Mikhailov and corresponds to a time-like near-BPS Wilson loop differing by small fluctuations from a straight line. A simple relation is found between the shape of the Wilson loop and the shape of the closed string at the moment when it crosses the horizon of the Poincaré patch. As a result, the energy and spin of the closed string are encoded in properties of the Wilson loop. This suggests that closed string amplitudes with one of the closed strings falling into the Poincaré horizon should be dual to gauge theory correlators involving local operators and a Wilson loop of the T-dual ("momentum") theory.

Kruczenski, M.; Tseytlin, A. A.

2013-10-01

256

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

257

Loop heat pipe radiator  

SciTech Connect

This paper describes the design and testing of a Loop Heat Pipe Radiator (LHPR) which was developed as an alternative to state-of-the-art axially-grooved heat pipes for space-based heat rejection which would be usable with tubing made of aluminum foil covered with a carbon-epoxy composite. The LHPR had an aluminum envelope and a polymer wick, and used ammonia as a working fluid. It was 4 meters long with a mass of 1.4 kg. The LHPR transported 500 watts at a 2.3 meter adverse inclination and 1500 watts when horizontal. This non-optimized LHPR had a 3000 watt-meter capability, which is four times greater than an axially-grooved heat pipe of similar power-handling capability and mass. In addition to a higher power handling capability, the LHPR has a much higher capillary margin than axially-grooved pipes. That high capillary margin simplifies ground testing in a 1-g environment by reducing the need for the careful levelling and vibration reduction required by axially-grooved pipes. {copyright} {ital 1996 American Institute of Physics.}

Sarraf, D.B.; Gernert, N.J. [Thermacore, Inc., 780 Eden Rd., Lancaster, Pennsylvania (United States)

1996-03-01

258

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

259

Unimodular loop quantum cosmology  

SciTech Connect

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, D.-W.; Geiller, Marc [Department of Physics, Beijing Normal University, Beijing 100875 (China); APC-Astroparticule et Cosmologie, Universite Paris Diderot Paris 7, Paris (France)

2010-09-15

260

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

261

Constraining Light Colored Particles with Event Shapes  

SciTech Connect

Using recently developed techniques for computing event shapes with soft-collinear effective theory, CERN Large Electron Positron Collider event shape data are used to derive strong model-independent bounds on new colored particles. In the effective field theory computation, colored particles contribute in loops not only to the running of {alpha}{sub s} but also to the running of hard, jet, and soft functions. Moreover, the differential distribution in the effective theory explicitly probes many energy scales, so even shapes have a strong sensitivity to new particle thresholds. Using thrust data from ALEPH and OPAL, colored adjoint fermions (such as a gluino) below 51.0 GeV are ruled out to 95% confidence. This is nearly an order-of-magnitude improvement over the previous model-independent bound of 6.3 GeV.

Kaplan, David E.; Schwartz, Matthew D. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 (United States)

2008-07-11

262

Glueball masses and the loop-loop correlation functions  

Microsoft Academic Search

We analyse the pure gauge lattice QCD by measuring loop-loop correlation functions on a 123×32 lattice at beta=5.9. We select a set of operators given by the smearing procedure. We obtain a good estimate of the mass of the 0++ state and for the string tension, and upper bounds for the masses of the 2++ and the 1+- states.

M. Albanese; F. Costantini; G. Fiorentini; F. Flore; M. P. Lombardo; R. Tripiccione; P. Bacilieri; L. Fonti; E. Remiddi; M. Bernaschi; N. Cabibbo; L. A. Fernandez; E. Marinari; G. Parisi; G. Salina; S. Cabasino; F. Marzano; P. Paolucci; S. Petrarca; F. Rapuano; P. Marchesini; P. Giacomelli; R. Rusack

1987-01-01

263

A unified theory of adaptive locally optimum processing  

Microsoft Academic Search

By using the concept of deflection and treating the signal as of known or unknown structure, a unified approach to adaptive locally optimum processing can be developed. This theory brings together processing techniques which have been treated by various authors for application to the detection of either broadband or narrowband signals in undersea surveillance and communications. The theory applies in

James Bond; Stefen Hui; D. Stein; J. Zeidler

1993-01-01

264

Optimum mix of conservation and solar energy in buildings  

SciTech Connect

A methodology is developed for optimally allocating resources between conservation and solar strategies in building design. Formulas are presented for a constrained optimum in which the initial investment is limited. The procedure is amenable to hand analysis if tables are available which give the Solar Savings Fraction as a function of the Load Collector Ratio for the locality. A numerical example is given.

Balcomb, J.D.

1980-01-01

265

Optimum Efficiency Control of Traveling-Wave Ultrasonic Motor System  

Microsoft Academic Search

The operational efficiency of ultrasonic motor motion control systems is much lower than that of traditional electromag- netic motors, which badly restricts the application of ultrasonic motor in portable devices. Lower efficiency, robustness, and wear condition are the main problems of ultrasonic motor systems. This paper studies on the optimum efficiency control strategy of an ultrasonic motor system and selects

Jingzhuo Shi; Bo Liu

2011-01-01

266

Optimum grounding grid design by using an evolutionary algorithm  

Microsoft Academic Search

A new application is proposed for getting the optimum design of grounding grids. The basic design quantities of the grounding grids are the ground resistance (Rg), the ground potential rise (GPR), touch and step voltages. These mentioned quantities depend on the grid parameters, which are its side lengths, radius of grid conductors and length of vertical rods. The dependence of

Sherif Ghoneim; Holger Hirsch; Ahdab Elmorshedy; Rabah Amer

2007-01-01

267

Design of cellular structures for optimum efficiency of heat dissipation  

Microsoft Academic Search

Metal cellular material is a new material attractive for its light weight and potential multifunctionality. In the present paper, we study cylindrical structures made of linear metal cellular material. The outer surface of the cylindrical structure is subjected to thermal boundary condition, and cooling fluid is forced through the cylinder to remove heat through the inner cell walls. Optimum design

Bo Wang; GengDong Cheng

2005-01-01

268

Optimum Input Selection For Data Driven Modeling. Mirage or Reality?  

Microsoft Academic Search

The implementation and evaluation of data driven modeling have been facing multiple challenges over the past two decades. Some of these challenges (e.g., the choice of the modeling technique, predictive uncertainty, assessment of the model performance) are shared with physical and conceptual modeling. But other challenges, such as selection of optimum inputs and lack of conceptual\\/physical justification, are unique to

Amin Elshorbagy; Zohreh Izadifar

2010-01-01

269

Simultaneous optimum detection and estimation of signals in noise  

Microsoft Academic Search

The problem of simultaneous detection and estimation of signals in noise is formulated in the language of statistical decision theory. Optimum structures and corresponding general measures of system performance are derived under the Bayes criterion of minimum average risk for the detectors and estimators appropriate to this type of joint operation: It is shown that whereas the structures of the

DAVID MIDDLETON; RAFFAELE ESPOSITO

1968-01-01

270

An Optimum Reverberation Time for Mosques in Bangladesh  

Microsoft Academic Search

For a mosque in Bangladesh, the acoustical requirements in terms of intelligibility and liveliness are dissimilar for the types of sounds - recitation from the Holy Koran and speech on religious subjects. To attain an overall satisfactory acoustical performance, it is significant to find an optimum Reverberation Time (RT), which is one of the important factors affecting intelligibility and liveliness.

Sheikh Muhammad Najmul Imam; Nizamuddin Ahmed; Daiji Takahashi

2009-01-01

271

Solar panel installation configurations for optimum system performance  

Microsoft Academic Search

The main object of this paper is to identify solar panel installation configurations to achieve optimum system performance irrespective of installation surface configurations. It is important to mention that the panel installation requirements are strictly dependent on the roof configurations, Northern and Southern hemispherical locations, and the latitudes of the installation locations. Panel installation schemes for flat roof, inclined roof,

A. R. Jha

2010-01-01

272

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

273

Optimum harmonic spacing for MT-MFSK synchronization symbols  

NASA Astrophysics Data System (ADS)

Synchronization of multitone M-ary frequency-shift keying (MT-MFSK) symbols can be achieved by examining the relationship between phase and harmonic number of a received symbol. The authors identify two alternative estimation strategies to determine the received symbol's optimum harmonic spacing.

Evans, M. J.; Yates, K. W.

1994-03-01

274

Optimum Balanced Block and Latin Square Designs for Correlated Observations  

Microsoft Academic Search

In this paper designs are found which are optimum for various models that include some autocorrelation in the covariance structure $V$. First it is noted that the ordinary least squares estimator is quite robust against small perturbations in $V$ from the uncorrelated case $V_0 = \\\\sigma^2_I$. This \\

J. Kiefer; H. P. Wynn

1981-01-01

275

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° 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

276

Optimum insulation thickness of external walls for energy saving  

Microsoft Academic Search

Most of energy is used up to space heating in the cold regions of Turkey. Insulation in external walls of buildings has been gaining much more interest in recent years not only for the environmental effect of the consumed energy but also the high cost of the energy. Therefore, the optimum insulation thickness was investigated in this study for the

Kemal Çomakl?; Bedri Yüksel

2003-01-01

277

Generalized optimum PWM technique: analysis and application to battery charging  

Microsoft Academic Search

The basic variables that characterize the classes of waveforms considered for optimization of PWM waveforms are evaluated. To alleviate computational problems a shift to the time domain is found quite attractive. This shift greatly reduces the computational effort and time and will bring the applications of optimum PWM waveforms techniques closer to the real time application. Another advantage of the

Elhussein; A. E. M

1984-01-01

278

Optimum Image Thresholding via Class Uncertainty and Region Homogeneity  

Microsoft Academic Search

Abstract?hresholding is a popular image segmentation method that converts a gray-level image into a binary image. The selection of optimum thresholds has remained a challenge over decades. Besides being a segmentation tool on its own, often it is also a step in many advanced image segmentation techniques in spaces other than the image space. Most of the thresholding methods reported

Punam K. Saha; Jayaram K. Udupa

2001-01-01

279

A Global Optimum Approach for One-Layer Neural Networks  

Microsoft Academic Search

The article presents a method for learning the weights in one-layer feed-forward neural networks minimizing either the sum of squared errors or the maximum absolute error, measured in the input scale. This leads to the existence of a global optimum that can be easily obtained solving linear systems of equations or linear programming problems, using much less computational power than

Enrique Castillo; Oscar Fontenla-romero; Bertha Guijarro-berdiñas; Amparo Alonso-betanzos

2002-01-01

280

A note on optimum MMSE\\/ZF multichannel equalization delay  

Microsoft Academic Search

The reconstruction delay has been, for long time, recognized a significant impact on the performance of an equalizer. Still, no proofs were given that sustain the experimental observations. In this note, we develop a formal analysis that shows that optimum equalization performance is met at a delay larger than the channel memory and smaller than the equalizer order. While it

Houcem Gazzah

2010-01-01

281

Optimum tilt angle and orientation for solar collectors in Syria  

Microsoft Academic Search

One of the important parameters that affect the performance of a solar collector is its tilt angle with the horizon. This is because of the variation of tilt angle changes the amount of solar radiation reaching the collector surface. A mathematical model was used for estimating the solar radiation on a tilted surface, and to determine the optimum tilt angle

Kamal Skeiker

2009-01-01

282

Speculative Attacks on Debts, Dollarization and Optimum Currency Area  

Microsoft Academic Search

The purpose of this article is to contribute to the discussion of the financial aspects of dollarization and optimum currency areas. Based on the model of self-fulfilling debt crisis developed by Cole and Kehoe (4), it is possible to evaluate the comparative welfare of economies, which either keep their local currency and an independent monetary policy, join a monetary union

Aloisio Araujo; Márcia Leon

283

Optimum Placement of Heated Blocks in Laminar Forced Convection  

Microsoft Academic Search

Improvements in cooling techniques of electronic components are paramount to the continuous increase in the complexity and thermal output of circuit boards. Recent studies show that a uniform distribution of the blocks might not be the optimum choice. In this paper, a parametric study of the different choices for interblock spacing is performed numerically using the finite volume method. Multiple

Raed I. Bourisli; Esam M. Alawadhi

2011-01-01

284

Optimum field squeezing from atomic sources: Three-level atoms  

Microsoft Academic Search

Light emitted from laser-driven atoms often has squeezed quadrature fluctuations reflecting the phase dependence of the atomic source excited into a coherent superposition by the driving field. In this paper, we study the maximum squeezing in the emitted light fields from three-level atoms, paying particular attention to the role of atomic coherences in governing the optimum squeezing which is possible.

B. J. Dalton; Z. Ficek; P. L. Knight

1994-01-01

285

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

286

Heat Transfer Characteristics and Optimum Insulation Thickness for Cavity Walls  

Microsoft Academic Search

The optimum thickness of insulation layers in cavity walls in buildings is determined under steady periodic conditions using the climatic data of Riyadh, Saudi Arabia. Different insulation materials are investigated at different locations in the cavity for a west-facing wall. The yearly cooling and heating transmission loads are calculated by an implicit finite-volume procedure that has been previously validated. These

Sami A. Al-Sanea; M. F. Zedan; Saleh A. Al-Ajlan; Atif S. Abdul Hadi

2003-01-01

287

Optimum Evaluation of Reactive Power Requirements in Power Distribution Systems  

Microsoft Academic Search

This paper presents three methodologies for determining optimum locations and magnitudes of reactive power compensation in power distribution systems. Method I and Method II are suitable for complex distribution systems with a combination of both radial and ring-main feeders and having different voltage levels. Method III is suitable for low-tension single voltage level radial feeders. Method I is based on

D. Thukaram; K. Parthasarathy; B. S. Ramakrishna IYENGAR

1985-01-01

288

Optimum geometry for torque ripple minimization of switched reluctance motors  

Microsoft Academic Search

For switched reluctance motors, one of the major problems is torque ripple which causes increased undesirable acoustic noise and possibly speed ripple. This paper describes an approach to determine optimum magnetic circuit parameters to minimize low speed torque ripple for such motors. The prediction of torque ripple is based on a set of normalized permeance and force data obtained from

F. Sahin; H. B. Ertan; K. Leblebicioglu

2000-01-01

289

Induction Motor Optimum Design, Including Active Power Loss Effect  

Microsoft Academic Search

The paper presents the optimum design of three-phase squirrel-cage induction motor on the basis of minimizing the annual cost of the motor. The annual cost is the sum of the annual interest and depreciation of the motor active material costs, annual cost of the active power loss of the motor and the annual energy cost required to supply such power

N. H. Fetih; H. M. El-Shewy

1986-01-01

290

OPTIMUM PERFORMANCE OF A COMBINED CYCLE POWER PLANT  

Microsoft Academic Search

A 37MW combined cycle power plant has been modelled and simulated. The behaviour of the gas turbine was studied at part load. Results of a sensitivity analysis of the effect of atmospheric temperature on the gas turbine performance are presented. The best combination of process parameters of steam leaving the steam generator that will give optimum performance of the combined

C. O. Ojo

291

Linear superconducting OGMS system: optimum configuration and performance  

Microsoft Academic Search

The linear superconducting OGMS system is described in terms of an analytical theory, computer simulation and particle stream analysis. The magnetic fields, force densities and equations of particle motion are established to yield the particle trajectories and deflections. These are obtained analytically and numerically, and their examination provides the optimum configuration of the system and the criterion for separation independent

R. Gerber; M. H. Watmough

1989-01-01

292

Shape tuning of adaptive structures for MEMS actuator applications  

NASA Astrophysics Data System (ADS)

This paper describes a systematic shape tuning procedure of adaptive structures for MEMS actuator applications. Due to fabrication process variations, MEMS devices can have different shapes with varied deflections. Such shape variations should be corrected for specific applications. As a result, it is necessary to establish a shape tuning procedure. Finite element modeling and optimization approach were used to minimize the shape variations. The procedure integrated Python programming, ABAQUS, and optimization algorithm for engineering applications. It used the powerful Python scripts programming, the vast library of ABAQUS functions, and a robust preexisting optimization algorithm, NLPQL, which provides more efficient, flexible, and systematic tools for optimization problems. Optimization was used in the adaptive structural designs and the shape tuning procedure after the assembly. Using this approach, three bimorph, gold-on-polysilicon, samples with different initial shapes were studied for shape tuning. The shape was characterized by maximum tip deflection resulting from thermo-mechanical deformations. The standard deviation of the shape variations was reduced from 1.21 to 0.05 ?m after tuning. This reduction was verified by experimental data. Another case with ten devices was studied to confirm the effectiveness of the procedure. The standard deviation of the deflections was reduced from 0.81 to 0.02 ?m after tuning. These results demonstrated the effectiveness of the optimum procedure for shape tuning. This general-purpose systematic methodology can be applied to adaptive structures for a variety of aerospace applications.

Ma, Zhichun; Lee, Yung-Cheng

2005-05-01

293

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

294

Design considerations for optimum ignition and dimming of fluorescent lamps using a resonant inverter operating open loop  

Microsoft Academic Search

The design of dimming electronic ballasts for fluorescent lamps has to be made taking into account that fluorescent lamp life is greatly affected by the starting scenario and by how the filament heating current is varied during dimming operation. Another important aspect is that the ballast should provide a wide stable control range of the output power, some applications require

J. Ribas; J. M. Alonso; E. L. Corominas; A. J. Calleja; M. Rico-Secades

1998-01-01

295

Optical loop framing  

SciTech Connect

The ATA provides an electron beam pulse of 70-ns duration at a 1-Hz rate. Our present optical diagnostics technique involve the imaging of the visible light generated by the beam incident onto the plant of a thin sheet of material. It has already been demonstrated that the light generated has a sufficiently fast temporal reponse in performing beam diagnostics. Notwithstanding possible beam emittance degradation due to scattering in the thin sheet, the observation of beam spatial profiles with relatively high efficiencies has provided data complementary to that obtained from beam wall current monitors and from various x-ray probes and other electrical probes. The optical image sensor consists of a gated, intensified television system. The gate pulse of the image intensifier can be appropriately delayed to give frames that are time-positioned from the head to the tail of the beam with a minimum gate time of 5-ns. The spatial correlation of the time frames from pulse to pulse is very good for a stable electron beam; however, when instabilities do occur, it is difficult to properly assess the spatial composition of the head and the tail of the beam on a pulse-to-pulse basis. Multiple gating within a pulse duration becomes desirable but cannot be performed because the recycle time (20-ms) of the TV system is much longer than the beam pulse. For this reason we have developed an optical-loop framing technique that will allow the recording of two frames within one pulse duration with our present gated/intensified TV system.

Kalibjian, R.; Chong, Y.P.; Prono, D.S.; Cavagnolo, H.R.

1984-06-01

296

Magnetic Field from Loops Model  

NSDL National Science Digital Library

The EJSMagnetic Field from Loops model computes the B-field created by an electric current through a straight wire, a closed loop, and a solenoid. Users can adjust the vertical position of the slice through the 3D field. The Magnetic Field from Loops 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_ntnu_MagneticFielfFromLoops.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 for classical mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang; Hwang, Fu-Kwun

2008-11-17

297

GENE LOOPS ENHANCE TRANSCRIPTIONAL DIRECTIONALITY  

PubMed Central

Eukaryotic genomes are extensively transcribed, forming both messenger (m) and noncoding (nc) RNAs. ncRNAs made by RNA polymerase II (Pol II) often initiate from bidirectional promoters (nucleosome-depleted chromatin) that synthesise mRNA and ncRNA in opposite directions. We demonstrate that actively transcribed mRNA encoding genes by adopting a gene loop conformation, restrict divergent transcription of ncRNAs. Since gene loop formation depends on a protein factor (Ssu72) that co-associates with both promoter and terminator, its inactivation leads to increased synthesis of promoter-associated divergent ncRNAs, referred to as Ssu72 restricted transcripts (SRT). Similarly, inactivation of individual gene loops by gene mutation enhances SRT synthesis. We demonstrate that gene loop conformation enforces transcriptional directionality on otherwise bidirectional promoters.

Tan-Wong, Sue Mei; Zaugg, Judith B.; Camblong, Jurgi; Xu, Zhenyu; Zhang, David W.; Mischo, Hannah E.; Ansari, Aseem Z.; Luscombe, Nicholas M.; Steinmetz, Lars M.; Proudfoot, Nick J.

2012-01-01

298

Feasibility study and optimum loading pattern of a multi-ring inflatable intravaginal applicator  

PubMed Central

Purpose A cylinder applicator is the standard treatment device for intravaginal brachytherapy. However, they are limited in their ability to simultaneously spare the organs at risk (OAR), and reduce the hot spot in the vaginal mucosa, while achieving adequate dose conformality. This study aims to compare the dosimetric characteristics of single and multi-channel cylinders, and utilizes volume point dose optimizations to investigate the feasibility and optimum loading method for a multi-ring inflatable intravaginal applicator. Material and methods Studies were designed to: (1) test the feasibility of multi-ring applicators, (2) compare dose distributions between different multi-channel applicators and loading patterns, (3) test non-uniform prescription depths around the multi-ring cylinder. Results Compared to a cylinder with a single central channel, a cylinder with 6 lumina arranged around the periphery, providing the lumina had adequate distance to the cylinder surface, could reduce dose beyond the prescription depth. However, when the number of outer lumina increased from 6 to 12, no further dose reduction could be achieved and the high dose volume close to the surface of the cylinder increased. Moreover, an additional ring, with lumina further away from the surface, provided increased dose shaping capabilities, allowing for individualized dose distributions. Conclusions Dose could be reduced to normal tissue and the inner mucosa, and better conformity was seen to unique anatomical shapes. A modified peripheral loading pattern provided the optimum dose distribution, yielding good conformity, dose sparing at adjacent organs, and dose reduction in the high dose region of the vaginal mucosa.

Mehta, Keyur J.; Yaparpalvi, Ravindra; Hong, Linda; Mynampati, Dinesh; Tome, Wolfgang A.; Kalnicki, Shalom

2013-01-01

299

Effect of magnetic field and temperature on the ferroelectric loop in MnWO4  

NASA Astrophysics Data System (ADS)

The ferroelectric properties of MnWO4 single crystal have been investigated. Despite a relatively low remanent polarization, we show that the sample is ferroelectric. The shape of the ferroelectric loop of MnWO4 strongly depends on magnetic field and temperature. While its dependence does not directly correlate with the magnetocapacitance effect before the paraelectric transition, the effect of magnetic field on the ferroelectric polarization loop supports magnetoelectric coupling.

Kundys, Bohdan; Simon, Charles; Martin, Christine

2008-05-01

300

Effects of orientational degrees of freedom in closed-loop solubility phase diagrams  

Microsoft Academic Search

It is shown, within a lattice-gas model calculation, how fluctuating orientational degrees of freedom are responsible for closed-loop phase diagrams observed in many binary liquid mixtures. Quantitative agreement with experiment is obtained, and qualitative features, such as the shape of the closed-loops, are related to molecular properties of the liquids in the mixture. To whom reprint requests should be sent.

Chester A. Vause; James S. Walker

1982-01-01

301

Wilson loops and spin networks  

NASA Astrophysics Data System (ADS)

If G is any finite product of orthogonal, unitary and symplectic matrix groups, then Wilson loops generate a dense subalgebra of continuous observables on the configuration space of lattice gauge theory with structure group G. If G is orthogonal, unitary or symplectic, then Wilson loops associated to the natural representation of G are enough. This extends a result of A. Sengupta [4]. In particular, our approach includes the case of even orthogonal groups.

Lévy, Thierry

2006-03-01

302

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

303

Wireless loops: What are they?  

Microsoft Academic Search

Several loop applications of wireless technology are aimed at reducing the cost of deploying communications services ranging\\u000a from telephone to wideband video. In these applications, wireless links replace a portion of a wireline loop from a central\\u000a location (a central office or cable headend) to a subscriber. The replacement of labor-intensive wireline technology by complex\\u000a mass-produced integrated electronics in wireless

Donald C. Cox

1996-01-01

304

Synthesizing robust mode shapes with ? and implicit model following  

Microsoft Academic Search

Control synthesis problems involving assignment of closed-loop model shapes using implicit model following (IMF) structure are considered in the context of H2, H?, and ?-synthesis theories. An extension to the dynamic output feedback case is given for the quadratic or H 2 IMF problem. The IMF problem is embedded within the framework of ? control theory, and extensions for including

J. C. Morris; P. Apkarian; J. C. Doyle

1992-01-01

305

Tooth - abnormal shape  

MedlinePLUS

Hutchinson incisors; Abnormal tooth shape; Peg teeth; Mulberry teeth; Conical teeth ... The appearance of normal teeth varies, especially the molars. Abnormally shaped teeth can result from many different conditions. Specific diseases can have a profound effect ...

306

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

307

Simulation of polarization and butterfly hysteresis loops in bismuth layer-structured ferroelectric thin films  

NASA Astrophysics Data System (ADS)

Modeling of the hysteresis loop of ferroelectric thin films has been thought very difficult owing to its nonlinear and history-dependent electric field effects. Here we extend the Preisach model [Z. Phys. 94, 277 (1935)] by using the distribution function integral and superposition method. The model shows improved hysteresis loop that agrees reasonably well with the experimental data measured from the bismuth layer-structured ferroelectric thin films. Compared with the previous model, the current model provides polarization-field (P-E) loop with full and symmetric shape, suitable coercive field (Ec), and few undesirable parameters. The butterfly loop of perovskite-type ferroelectric thin films is also simulated. Additionally, the approach is able to describe the unsaturated loops obtained under various ac electric fields, which is very useful in circuit simulation of ferroelectric field effect transistor or ferroelectric capacitor.

Ye, Z.; Tang, M. H.; Cheng, C. P.; Zhou, Y. C.; Zheng, X. J.; Hu, Z. S.

2006-11-01

308

Affective loop experiences: designing for interactional embodiment.  

PubMed

Involving our corporeal bodies in interaction can create strong affective experiences. Systems that both can be influenced by and influence users corporeally exhibit a use quality we name an affective loop experience. In an affective loop experience, (i) emotions are seen as processes, constructed in the interaction, starting from everyday bodily, cognitive or social experiences; (ii) the system responds in ways that pull the user into the interaction, touching upon end users' physical experiences; and (iii) throughout the interaction the user is an active, meaning-making individual choosing how to express themselves-the interpretation responsibility does not lie with the system. We have built several systems that attempt to create affective loop experiences with more or less successful results. For example, eMoto lets users send text messages between mobile phones, but in addition to text, the messages also have colourful and animated shapes in the background chosen through emotion-gestures with a sensor-enabled stylus pen. Affective Diary is a digital diary with which users can scribble their notes, but it also allows for bodily memorabilia to be recorded from body sensors mapping to users' movement and arousal and placed along a timeline. Users can see patterns in their bodily reactions and relate them to various events going on in their lives. The experiences of building and deploying these systems gave us insights into design requirements for addressing affective loop experiences, such as how to design for turn-taking between user and system, how to create for 'open' surfaces in the design that can carry users' own meaning-making processes, how to combine modalities to create for a 'unity' of expression, and the importance of mirroring user experience in familiar ways that touch upon their everyday social and corporeal experiences. But a more important lesson gained from deploying the systems is how emotion processes are co-constructed and experienced inseparable from all other aspects of everyday life. Emotion processes are part of our social ways of being in the world; they dye our dreams, hopes and bodily experiences of the world. If we aim to design for affective interaction experiences, we need to place them into this larger picture. PMID:19884153

Höök, Kristina

2009-12-12

309

Affective loop experiences: designing for interactional embodiment  

PubMed Central

Involving our corporeal bodies in interaction can create strong affective experiences. Systems that both can be influenced by and influence users corporeally exhibit a use quality we name an affective loop experience. In an affective loop experience, (i) emotions are seen as processes, constructed in the interaction, starting from everyday bodily, cognitive or social experiences; (ii) the system responds in ways that pull the user into the interaction, touching upon end users' physical experiences; and (iii) throughout the interaction the user is an active, meaning-making individual choosing how to express themselves—the interpretation responsibility does not lie with the system. We have built several systems that attempt to create affective loop experiences with more or less successful results. For example, eMoto lets users send text messages between mobile phones, but in addition to text, the messages also have colourful and animated shapes in the background chosen through emotion-gestures with a sensor-enabled stylus pen. Affective Diary is a digital diary with which users can scribble their notes, but it also allows for bodily memorabilia to be recorded from body sensors mapping to users' movement and arousal and placed along a timeline. Users can see patterns in their bodily reactions and relate them to various events going on in their lives. The experiences of building and deploying these systems gave us insights into design requirements for addressing affective loop experiences, such as how to design for turn-taking between user and system, how to create for ‘open’ surfaces in the design that can carry users' own meaning-making processes, how to combine modalities to create for a ‘unity’ of expression, and the importance of mirroring user experience in familiar ways that touch upon their everyday social and corporeal experiences. But a more important lesson gained from deploying the systems is how emotion processes are co-constructed and experienced inseparable from all other aspects of everyday life. Emotion processes are part of our social ways of being in the world; they dye our dreams, hopes and bodily experiences of the world. If we aim to design for affective interaction experiences, we need to place them into this larger picture.

Hook, Kristina

2009-01-01

310

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

2013-06-15

311

Revealing triple-shape memory effect by polymer bilayers.  

PubMed

Bilayer polymers that consist of two epoxy dual-shape memory polymers of well-separated glass transition temperatures have been synthesized. These bilayer epoxy samples exhibit a triple-shape memory effect (TSME) with shape fixities tailorable by changing the ratio between the two layers. The triple-shape fixities of the bilayer epoxy polymers can be explained by the balance of stress between the two layers. Based on this work, it is believed that the following three molecular design criterions should be considered in designing triple-shape memory polymers with optimum TSME: 1) well-separated thermal transitions, 2) a strong interface, and 3) an appropriate balance of moduli and relative ratios between the layers (or microphases). PMID:21638460

Xie, Tao; Xiao, Xingcheng; Cheng, Yang-Tse

2009-08-04

312

The Holocene Thermal Optimum in the Barents Sea  

NASA Astrophysics Data System (ADS)

AMS 14C-dated oxygen isotope records on planktic and benthic foraminifer in our Core ASV 880 from the eastern branch of the Franz Victoria Trough (Northern Barents Sea) shows the Holocene thermal optimum at 7.8 - 6.9 cal ka BP (Duplessy et al., 2001) manifested by low oxygen isotope values as a result of warming of subsurface to bottom waters related to the increased Atlantic water input. Benthic foraminiferal assemblages during this optimum are enriched in the species indicating rather long ice-free season. We test here a hypothesis that the optimum can also be identified by foraminiferal assemblages in other parts of the sea with present water column structure indicating subsurface Atlantic water. We studied the Holocene benthic and planktic foraminiferal assemblages at several locations within the passage of the Atlantic water in surface and subsurface layers,and tried to identify the timing of assumed optimum by the interpolation between AMS 14C-dates when available, and using a level of polychaetas appearance in the Barents Sea at about 5 cal ka BP. The base of the Holocene layer is legibly distinguished in our cores by pronounced changes in sediment color, grain size, sedimentary structures, and an appearance of numerous foraminiferal tests. These two levels provide us with the tick-points for the age control in undated cores. An increase in abundance of species related to Atlantic-derived water is found at the end of Early Holocene in the south-western branch of the Franz Victoria Trough, whereas any faunal indication of the optimum are absent in other cores. On the contrary, our new oxygen isotope data clearly demonstrate the optimum at some locations. The maximum content of so-called "atlantic" benthic species occurs at different time levels in specific cores, and the same is true for planktic foraminifers generally considered to be related to the Atlantic water in the Barents Sea. Therefore, the above hypothesis is not confirmed by our data. It means that besides the water mass properties foraminifer distribution in the region is strongly controlled by food supply.

Murdmaa, I.; Ivanova, E.; Risebrobakken, B.; Akhrimenko, N.; Yamskova, E.

2005-12-01

313

Laser beam shaping  

Microsoft Academic Search

This presentation deals with the theoretical and practical aspects of the design and fabrication of laser beam shapers. Laser beam shaping methods are categorized as: (i) external shaping which is applied to an existing laser beam; and (ii) internal cavity shaping which is an integral part of the laser cavity. An exact diffraction-based algorithm is developed for the design of

L. N. Hazra

2008-01-01

314

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

315

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

316

Bacterial cell shape  

Microsoft Academic Search

Bacterial species have long been classified on the basis of their characteristic cell shapes. Despite intensive research, the molecular mechanisms underlying the generation and maintenance of bacterial cell shape remain largely unresolved. The field has recently taken an important step forward with the discovery that eukaryotic cytoskeletal proteins have homologues in bacteria that affect cell shape. Here, we discuss how

Matthew T. Cabeen; Christine Jacobs-Wagner

2005-01-01

317

Automatic tiling of iterative stencil loops  

Microsoft Academic Search

Iterative stencil loops are used in scientific programs to implement relaxation methods for numerical simulation and signal processing. Such loops iteratively modify the same array elements over different time steps, which presents opportunities for the compiler to improve the temporal data locality through loop tiling. This article presents a compiler framework for automatic tiling of iterative stencil loops, with the

Zhiyuan Li; Yonghong Song

2004-01-01

318

Heating the solar corona by plasma loops  

Microsoft Academic Search

We investigate the heating of the corona via plasma loops. It is shown that it may be possible to maintain the high corona temperatures using plasma loops as conduits. Under certain conditions heat can flow across magnetic fields up temperature gradients, a mechanism that has been previously applied to the heating of plasma loops. A typical conduit loop is hotter

J. M. A. Ashbourn; L. C. Woods

2006-01-01

319

Structural States and Dynamics of the D-Loop in Actin  

PubMed Central

Conformational changes induced by ATP hydrolysis on actin are involved in the regulation of complex actin networks. Previous structural and biochemical data implicate the DNase I binding loop (D-loop) of actin in such nucleotide-dependent changes. Here, we investigated the structural and conformational states of the D-loop (in solution) using cysteine scanning mutagenesis and site-directed labeling. The reactivity of D-loop cysteine mutants toward acrylodan and the mobility of spin labels on these mutants do not show patterns of an ?-helical structure in monomeric and filamentous actin, irrespective of the bound nucleotide. Upon transition from monomeric to filamentous actin, acrylodan emission spectra and electron paramagnetic resonance line shapes of labeled mutants are blue-shifted and more immobilized, respectively, with the central residues (residues 43–47) showing the most drastic changes. Moreover, complex electron paramagnetic resonance line shapes of spin-labeled mutants suggest several conformational states of the D-loop. Together with a new (to our knowledge) actin crystal structure that reveals the D-loop in a unique hairpin conformation, our data suggest that the D-loop equilibrates in F-actin among different conformational states irrespective of the nucleotide state of actin.

Durer, Zeynep A. Oztug; Kudryashov, Dmitri S.; Sawaya, Michael R.; Altenbach, Christian; Hubbell, Wayne; Reisler, Emil

2012-01-01

320

Offline loop investigation for handwriting analysis.  

PubMed

Resolution of different types of loops in handwritten script presents a difficult task and is an important step in many classic word recognition systems, writer modeling, and signature verification. When processing a handwritten script, a great deal of ambiguity occurs when strokes overlap, merge, or intersect. This paper presents a novel loop modeling and contour-based handwriting analysis that improves loop investigation. We show excellent results on various loop resolution scenarios, including axial loop understanding and collapsed loop recovery. We demonstrate our approach for loop investigation on several realistic data sets of static binary images and compare with the ground truth of the genuine online signal. PMID:19110488

Steinherz, Tal; Doermann, David; Rivlin, Ehud; Intrator, Nathan

2009-02-01

321

The optimum design configurations of Savonius wind turbines  

SciTech Connect

This paper describes results of a systematic wind tunnel study aimed at development of an optimum configuration of Savonius rotor wind mill. Model tests were conducted in a wind tunnel on a number of Savonius rotor configurations in wind speed of 4 - 12m/s. The variables tested were blade aspect ratio, blade overlap, blade separation gap, profile of the rotor blade cross-section and the effect adding the guide vane. From this study, the power coefficient of the basic Savonius rotor is relatively low value of 0.15-0.20, with optimum blade configuration and guide vane, a maximum value of power coefficient of 0.34 was obtained and the results appears quite encouraging. Moreover, a special study was made of the flow visualization in a water channel to confirm the inference for the air flow patterns round and through the rotor.

Ushiyama, I.; Mino, M.; Nagai, H.

1982-08-01

322

Optimum Design of Balanced SAW Filters Using Differential Evolution  

NASA Astrophysics Data System (ADS)

An optimum design technique of balanced surface acoustic wave (SAW) filters using a differential evolution (DE) is proposed. First of all, in order to evaluate the performance of balanced SAW filters based on the computer simulation, a network model of them is composed by using mixed-mode S-parameters. Then the structural design of balanced SAW filters is formulated as a function optimization problem for improving their performance in both the balance characteristics and the filter characteristics. For solving the function optimization problem, a basic DE is employed. In order to apply the basic DE to the optimization problem effectively, a distorted problem space defined by various design parameters is embedded in a regularized continuous search space. Finally, through the computational experiments conducted on a balanced SAW filter, the usefulness of the proposed optimum design technique is demonstrated. Besides, it is clarified that the non-symmetric structure of SAW filter has a possibility to improve its balance characteristics.

Tagawa, Kiyoharu

323

Measured optimum BNS damping configuration of the SLC linac  

SciTech Connect

Transverse wakefield (or BNS{sup 1}) damping has been successfully used in the linac of the Stanford Linear Collider (SLC) to reduce emittance enlargement from beam trajectory jitter coupled with transverse wakefields. The authors are presently in the process of raising the bunch intensities from 3 x 10{sup 10} particles per bunch to over 4 x 10{sup 10}. With these higher currents the RF phasing configuration which produces BNS damping must be improved. Too little damping allows excessive emittance growth from jitter but too much damping increases emittance growth from chromatic effects and produces an unacceptable loss of overall energy. Several experiments were performed to find the optimum settings for the present situation. An empirical optimum was found with a combination of (1) somewhat stronger BNS RF phase settings in the upstream section of the linac and (2) a stronger quadrupole lattice in the downstream section.

Seeman, J.T.; Decker, F.J.; Holtzapple, R.L.; Spence, W.L.

1993-06-01

324

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

325

Optimum Simple StepStress Plans for Accelerated Life Testing  

Microsoft Academic Search

This paper presents optimum plans for simple (two stresses) step-stress tests where all units are run to failure. Such plans minimize the asymptotic variance of the maximum likelihood estimator (MLE) of the mean life at a design stress. The life-test model consists of: 1) an exponential life distribution with 2) a mean that is a log-linear function of stress, and

Robert Miller; Wayne Nelson

1983-01-01

326

Optimum priming dose of vecuronium for tracheal intubation  

Microsoft Academic Search

To determine the optimum priming dose of vecuronium, we divided 173 surgical patients into five groups according to priming\\u000a dose (0, 2.5, 5.0, 7.5, and 10 ?g·kg?1). For endotracheal intubation, we administered a priming dose of vecuronium, and then after 4 min, the remainder was injected\\u000a for a total dosage of 0.15 mg·kg?1. Onset time was determined by a 95%

Tetsuo Takaya; Hidekazu Kato; Mamoru Takiguchi

1996-01-01

327

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

328

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

329

Identification and Creation of Optimum Habitat Conditions for Livestock  

Microsoft Academic Search

Abstract Optimum,habitat condition,is a concept,typically used for wildlife rather than livestock. The definition for optimal,livestock habitat will vary with management objectives. Abiotic factors, such as topography, water availability, and thermal cover, affect animal,performance,and uniformity,of grazing. Livestock usually prefer gentle slopes and avoid traveling long horizontal and vertical distances to water. Shade and nearby water are used for thermoregulation when temperatures

Derek W. Bailey

2005-01-01

330

Adjoint method for the optimum planning of industrial pollutant sources  

Microsoft Academic Search

The optimum planning of industrial pollutant sources, which optimizes the economic object without violating environmental\\u000a constraints, is an important and hard task to be conquered. In this paper, an adjoint method is developed to solve the problem.\\u000a The penalty function is introduced to deal with the environmental inequality constraints, and Lagrange function is constructed\\u000a to derive the adjoint equation and

Feng Liu; Fei Hu; Jiang Zhu

2005-01-01

331

Optimum take-off angle in the long jump  

Microsoft Academic Search

In this study, we found that the optimum take-off angle for a long jumper may be predicted by combining the equation for the range of a projectile in free flight with the measured relations between take-off speed, take-off height and take-off angle for the athlete. The prediction method was evaluated using video measurements of three experienced male long jumpers who

NICHOLAS P. LINTHORNE; MAURICE S. GUZMAN; LISA A. BRIDGETT

2005-01-01

332

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

333

An optimum design selection approach for product customization development  

Microsoft Academic Search

Consumer preferences and information on product choice behavior can be of significant value in the development processes of\\u000a innovative products. In this paper, product customization evaluation and selection model is introduced to support imprecision\\u000a inherent of qualitative inputs from customers and designers in the decision making process. Focusing on customer utility generation,\\u000a an optimum design selection approach based on fuzzy

Chen Liu; Alejandro Ramirez-Serrano; Guofu Yin

334

Optimum selection of an energy resource using fuzzy logic  

Microsoft Academic Search

Optimum selection of an energy resource is a vital issue in developed countries. Considering energy resources as alternatives (nuclear, hydroelectric, gas\\/oil, and solar) and factors upon which the proper decision will be taken as attributes (economics, availability, environmental impact, and proliferation), one can use the multi-attribute utility theory (MAUT) to optimize the selection process.Recently, fuzzy logic is extensively applied to

Ayah E. Abouelnaga; Abdelmohsen Metwally; Mohammad E. Nagy; Saeed Agamy

2009-01-01

335

Optimum Design of Experiments for Enzyme Inhibition Kinetic Models  

Microsoft Academic Search

We find closed-form expressions for the D-optimum designs for three- and four-parameter nonlinear models arising in kinetic models for enzyme inhibition. We calculate the efficiency of designs over a range of parameter values and make recommendations for design when the parameter values are not well known. In a three-parameter experimental example, a standard design has an efficiency of 18.2% of

Barbara Bogacka; Maciej Patan; Patrick J. Johnson; Kuresh Youdim; Anthony C. Atkinson

2011-01-01

336

Tax evasion and the optimum general income tax  

Microsoft Academic Search

This paper incorporates tax evasion into an optimum general income tax problem with endogenous labor supply. It posits a two-group model with high- and low-wage individuals to investigate the properties of optimal audit and tax structures. The following main results are obtained. First, high-wage persons are never audited while low-wage persons are audited with a probability strictly less than one.

Helmuth Cremer; Firouz Gahvari

1996-01-01

337

Managerial implications of calculating optimum nurse staffing in medical units.  

PubMed

A critical managerial decision in health care organizations is the staffing decision. We offer a model to derive an optimum mix of different staff categories that minimizes total cost subject to constraints imposed by the patient acuity system and minimum staffing policies in a medical unit of Fairbanks Memorial Hospital, Alaska. We also indicate several managerial implications on how our results and their sensitivity analyses can be used effectively in decision making in a variety of categories. PMID:10572787

Bordoloi, S K; Weatherby, E J

1999-01-01

338

Optimum tunnel barrier in ferromagnetic–insulator–ferromagnetic tunneling structures  

Microsoft Academic Search

Al2O 3 tunnel barriers I, formed by the oxidization of Al metal of various thicknesses between two ferromagnetic (FM) films were investigated to understand the influence of overlayer metal Al on the junction magnetoresistance (JMR). The optimum thickness of Al was observed to lie in the range of 1–1.6 nm to achieve good JMR in FM–I–FM junctions. Additionally, such junctions

Jagadeesh S. Moodera; Elizabeth F. Gallagher; Keziah Robinson; Janusz Nowak

1997-01-01

339

Optimum thickness for 3He neutron polarising filters  

NASA Astrophysics Data System (ADS)

Gaseous 3He neutron polarisers are undergoing rapid development for use with neutron beams. For any polarising transmission filter, polarisation increases and transmission decreases with increasing filter thickness. There is an optimum thickness for such filters to minimise the errors in quantities measured in a given available time. Formulae and sample calculations are presented for a number of important cases including the use of 3He polarising filters in conjunction with other types of polarisers.

Goossens, D. J.; Cussen, L. D.

1999-06-01

340

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

341

Optimum constant-stress accelerated life-test plans  

Microsoft Academic Search

This paper deals with optimal design of four-level constant-stress accelerated life test plans with various censoring times. The optimum plans choose the stress levels, test units allocated to each stress, and censoring times to minimize the asymptotic variance of the MLE of the mean (log) life at design stress and test length. A FORTRAN-77 program was written to calculate the

Guang-Bin Yang; Reader Aids

1994-01-01

342

Material design of aerated concrete—An optimum performance design  

Microsoft Academic Search

An optimum design for Autoclaved Aerated Concrete (AAC) panel is proposed on the basis of the performance requirements for\\u000a dwellings. With bulk density representing “property” as an intensive variable and thickness of the wall representing “quantity”\\u000a as an extensive variable. Performance requirements such as cost, thermal, acoustic insulation and structural safety are illustrated\\u000a in terms of bulk density d and

S. Tada

1986-01-01

343

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

2010-03-01

344

Optimum temporal update periods for regional ionosphere monitoring  

NASA Astrophysics Data System (ADS)

Monitoring of the ionospheric variability is necessary for improving the performance of communication, navigation, and positioning systems. Total electron content (TEC) is an important parameter in analyzing the variability of the ionosphere. Owing to sparse distribution of TEC in a given region, spatial interpolation methods are used for mapping TEC on a dense grid. Typically, TEC maps are produced at time intervals that do not match the variability of the regional ionosphere. To capture the local, small-scale variability, the temporal update period (TUP) in regional TEC monitoring has to be optimized. In this study, the wide sense stationarity (WSS) period is proposed to be used as the optimum TUP of the regional TEC maps. Individual WSS periods of TEC are obtained by the sliding window statistical analysis method. Four types of measures are employed to compute the differences between TEC maps. When WSS periods of the sampling points and the differences of TEC maps are compared with each other, it is observed that for the quiet days of the ionosphere where the general temporal trends dominate, the maximum WSS period in the region can be chosen as the optimum TUP. For the disturbed days of the ionosphere where high temporal and spatial variability is observed, averages or the minimums of WSS periods in a given region have to be chosen as the optimum TUP. Thus, WSS period can be developed into a useful tool in monitoring the ionospheric variability in a given region.

Sayin, I.; Arikan, F.; Akdogan, K. E.

2010-12-01

345

On the Derivatives of Central Loops  

Microsoft Academic Search

The right(left) derivative, a?1,e? and e,a?1? isotopes of a C-loop are shown to be C-loops. Furthermore, for a central loop (L,F), it is shown thatF,Fa 1 ,Fa 1,eand ? F,F a 1,Fe,a 1 ? are systems of isotopic C-loops that obey a form of generalized dis- tributive law. Quasigroup isotopes (L, ?) and (L, ?) of a loop (L,?) and

T. G. Jaiyeo; J. O. Aden ´ õran

346

Loop Quantum Cosmology and Phenomenology  

SciTech Connect

Loop quantum cosmology has provided a large set of insights about the dynamics of loop quantum gravity, based on symmetric (sometimes exactly solvable) model systems combined with advanced perturbation techniques around them. Starting with an exactly solvable, harmonic system (which happens to illustrate singularity resolution by providing examples for bouncing solutions) a systematic perturbation theory is set up. As a key challenge, it remains to formulate general inhomogeneities in a fully consistent way, respecting space-time covariance. Only if this is achieved can loop quantum gravity provide a valid proposal for a modified-gravity theory with quantum corrections, and by this gain access to observational constraints. Recent progress in this direction is described.

Bojowald, Martin [Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, PA 16802 (United States)

2010-07-12

347

Changes in lung tumor shape during respiration.  

PubMed

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. PMID:22290510

Kyriakou, E; McKenzie, D R

2012-01-31

348

Coronal loops: isothermal or multithermal?  

NASA Astrophysics Data System (ADS)

Are coronal loops isothermal? A controversy over this question has arisen recently because different investigators using different techniques have obtained very different answers. Analysis of SOHO-EIT and TRACE data using narrowband filter ratios to obtain temperature maps has produced several key publications that suggest that coronal loops may be isothermal. We have constructed a multi-thermal distribution for several pixels along a relatively isolated coronal loop on the southwest limb of the solar disk using spectral line data from SOHO-CDS taken on 1998 Apr 20. These distributions are clearly inconsistent with isothermal plasma along either the line of sight or the length of the loop, and suggested rather that the temperature increases from the footpoints to the loop top. We speculated originally that these differences could be attributed to pixel size -- CDS pixels are larger, and more `contaminating' material would be expected along the line of sight. To test this idea, we used CDS iron line ratios from our data set to mimic the isothermal results from the narrowband filter instruments. These ratios indicated that the temperature gradient along the loop was flat, despite the fact that a more complete analysis of the same data showed this result to be false! The CDS pixel size was not the cause of the discrepancy; rather, the problem lies with the isothermal approximation used in EIT and TRACE analysis. These results should serve as a strong warning to anyone using this simplistic method to obtain temperature. This warning is echoed on the EIT web page: ``Danger! Enter at your own risk!'' In other words, values for temperature may be found, but they may have nothing to do with physical reality.

Schmelz, J.; Cirtain, J.

349

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

350

Geometry of mediating protein affects the probability of loop formation in DNA.  

PubMed

Recent single molecule experiments have determined the probability of loop formation in DNA as a function of the DNA contour length for different types of looping proteins. The optimal contour length for loop formation as well as the probability density functions have been found to be strongly dependent on the type of looping protein used. We show, using Monte Carlo simulations and analytical calculations, that these observations can be replicated using the wormlike-chain model for double-stranded DNA if we account for the nonzero size of the looping protein. The simulations have been performed in two dimensions so that bending is the only mode of deformation available to the DNA while the geometry of the looping protein enters through a single variable which is representative of its size. We observe two important effects that seem to directly depend on the size of the enzyme: 1), the overall propensity of loop formation at any given value of the DNA contour length increases with the size of the enzyme; and 2), the contour length corresponding to the first peak as well as the first well in the probability density functions increases with the size of the enzyme. Additionally, the eigenmodes of the fluctuating shape of the looped DNA calculated from simulations and theory are in excellent agreement, and reveal that most of the fluctuations in the DNA occur in regions of low curvature. PMID:18192346

Agrawal, Neeraj J; Radhakrishnan, Ravi; Purohit, Prashant K

2008-01-11

351

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

352

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

353

Optimum Aerodynamic Design Using the Navier–Stokes Equations  

Microsoft Academic Search

:   This paper describes the formulation of optimization techniques based on control theory for aerodynamic shape design in viscous\\u000a compressible flow, modeled by the Navier–Stokes equations. It extends previous work on optimization for inviscid flow. The\\u000a theory is applied to a system defined by the partial differential equations of the flow, with the boundary shape acting as\\u000a the control. The

A. Jameson; L. Martinelli; N. A. Pierce

1998-01-01

354

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

355

Optimum Thread Rolling Process That Improves SCC Resistance  

SciTech Connect

Accelerated testing in environments aggressive for the specific material have shown that fastener threads that are rolled after strengthening heat treatments have improved resistance to SCC initiation. For example, intergranular SCC was produced in one day when machined (cut) threads of high strength steel (ASTM A193 B-7 and A354 Grade 8) were exposed to an aggressive aqueous environment containing 8 weight % boiling ammonium nitrate and stressed to about 40% of the steel's yield strength (120 ksi, 827 MPa). In similar testing conditions, fasteners that had threads rolled before heat-treatment (quench and temper) had similar susceptibility to SCC. However, threads rolled after strengthening, exhibited no SCC after a week of exposure, even when stressed to 100% of the B-7 alloy yield strength. Similarly, intergranular SCC was produced in less than one day when machined (cut) threads of nickel-base alloys (X-750 and aged 625) were exposed to an aggressive 750 F doped steam environment (containing 100 ppm of chloride, fluoride, sulfate, nitrate and a controlled hydrogen overpressure) and stressed to about 80% of the alloy yield strength (117 ksi, 807 MPa). In similar testing conditions, threads rolled after strengthening exhibited no SCC after 50 days of exposure. This beneficial effect of the optimum thread rolling process (i.e., threads rolled after strengthening) is due to the retention of large residual compressive stresses in the thread roots (notches) which mitigate the applied notch tensile stresses resulting from joint design pre-loads. use of these material specific aggressive environments can provide an accelerated test to verify that threads were produced by the optimum thread rolling process. These tests could support fastener acceptance criteria or failure analysis of fasteners with unknown or uncertain manufacturing processes. The optimum process effects may not always be detected by more conventional methods (e.g., metallography or hardness testing).

A.R. Kephart

2001-10-29

356

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.

1988-03-01

357

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

358

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

359

Optimum value of original events on the PEPT technique  

SciTech Connect

Do Positron emission particle tracking (PEPT) has been used to track the motion of a single radioactively labeled tracer particle within a bed of similar particles. In this paper, the effect of the original event fraction on the results precise in two experiments has been reviewed. Results showed that the algorithm can no longer distinguish some corrupt trajectories, in addition to; further iteration reduces the statistical significance of the sample without improving its quality. Results show that the optimum value of trajectories depends on the type of experiment.

Sadremomtaz, Alireza; Taherparvar, Payvand [University of Guilan, P.O. Box 3489, Rasht, Guilan (Iran, Islamic Republic of)

2011-12-26

360

Optimum Onager: The Classical Mechanics of a Classical Siege Engine  

NASA Astrophysics Data System (ADS)

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 machine might be improved, a student can gain insight beyond the equations of motion and can test hypotheses on readily available working models. Some of these performance improvements are considered in this paper.

Denny, Mark

2009-12-01

361

Elastic carbon nanotube straight yarns embedded with helical loops.  

PubMed

Introducing stretchability and elasticity into carbon nanotube (CNT) yarns could extend their applications to areas such as stretchable and deformable fiber-based devices and strain sensors. Here, we convert a straight and inelastic yarn into a highly elastic structure by spinning a predefined number of helical loops along the yarn, resulting in a short helical segment with smooth structural transition to the straight portions. The loop-forming process is well controlled, and the obtained straight-helical-straight hybrid yarn is freestanding, stable, and based entirely on CNTs. The elastic and conductive yarns can be stretched to moderate tensile strains (up to 25%) repeatedly for 1000 cycles without producing residual deformation, with a simultaneous and linear change of electrical resistance depending on the strain. Our results indicate that conventional straight CNT yarns could be used as fiber-shaped strain sensors by simple structural modification. PMID:23400109

Shang, Yuanyuan; Li, Yibin; He, Xiaodong; Zhang, Luhui; Li, Zhen; Li, Peixu; Shi, Enzheng; Wu, Shiting; Cao, Anyuan

2013-03-21

362

TCR-alpha CDR3 loop audition regulates positive selection.  

PubMed

How positive selection molds the T cell repertoire has been difficult to examine. In this study, we use TCR-beta-transgenic mice in which MHC shapes TCR-alpha use. Differential AV segment use is directly related to the constraints placed on the composition of the CDR3 loops. Where these constraints are low, efficient selection of alphabeta pairs follows. This mode of selection preferentially uses favored AV-AJ rearrangements and promotes diversity. Increased constraint on the alpha CDR3 loops leads to inefficient selection associated with uncommon recombination events and limited diversity. Further, the two modes of selection favor alternate sets of AJ segments. We discuss the relevance of these findings to the imprint of self-MHC restriction and peripheral T cell activation. PMID:16888009

Ferreira, Cristina; Furmanski, Anna; Millrain, Maggie; Bartok, Istvan; Guillaume, Philippe; Lees, Rosemary; Simpson, Elizabeth; MacDonald, H Robson; Dyson, Julian

2006-08-15

363

Closing the Loop with Exercises  

ERIC Educational Resources Information Center

|Conducting exercises provides a critical bridge between the theory of an Emergency Action Plan and its effective implementation. When conducted properly, exercises can fill the gap between training and after-action review to close the preparedness loop--before an actual emergency occurs. Often exercises are planned and conducted on campus based…

Altizer, Andy

2008-01-01

364

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

365

Validation of Causal Loop Diagrams  

Microsoft Academic Search

In this paper, we present techniques for manually assessing the structural validity of each link in a causal loop diagram (CLD). A link is defined as consisting of an origination quantity, a destination quantity and a connection edge between them. Each link is considered as a separate and distinct causal hypothesis whose validity should stand on its own merits. Following

James R. Burns

366

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...

367

Deductive Planning with Inductive Loops  

Microsoft Academic Search

Agents plan to achieve and maintain goals. Maintenance that requires continuous action excludes the representation of plans as finite sequences of actions. If there is no upper bound on the number of actions, a simple list of actions would be infinitely long. Instead, a compact representation requires some form of looping construct. We look at a specific tem- porally extended

Martin Magnusson; Patrick Doherty

2008-01-01

368

Loop spaces and homotopy operations  

Microsoft Academic Search

The question of whether a given H-space X is, up to homotopy, a loop space has been studied from a variety of viewpoints. Here we address this question from the aspect of homotopy operations, in the classical sense of operations on homotopy groups. First, we show how an H-space structure on X can be used to define the action of

David Blanc

1998-01-01

369

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

370

Shaped time-optimal feedback control for disk-drive systems with back-electromotive force  

Microsoft Academic Search

In this paper, we describe the design of closed-loop control laws for disk-drive systems that account for back-electromotive force (back-EMF) by using a phase-plane approach. The time-optimal control law for a rigid body is shaped by using input shaping ideas to address the flexible mode, and then the altered rigid body phase-plane trajectories resulting from this shaping are calculated and

Chanat La-orpacharapan; Lucy Y. Pao

2004-01-01

371

A high-resolution, adaptive beam-shaping system for high-power lasers.  

PubMed

A high-resolution, high-precision beam-shaping system for high-power-laser systems is demonstrated. A liquid-crystal-on-silicon spatial light modulator is run in closed-loop to shape laser-beam amplitude and wavefront. An unprecedented degree of convergence is demonstrated, and important practical issues are discussed. Wavefront shaping for the applications in OMEGA EP laser is demonstrated, and other interesting examples are presented. PMID:20588762

Bahk, Seung-Whan; Fess, Ed; Kruschwitz, Brian E; Zuegel, Jonathan D

2010-04-26

372

Statistical-mechanical theory of DNA looping.  

PubMed

The lack of a rigorous analytical theory for DNA looping has caused many DNA-loop-mediated phenomena to be interpreted using theories describing the related process of DNA cyclization. However, distinctions in the mechanics of DNA looping versus cyclization can have profound quantitative effects on the thermodynamics of loop closure. We have extended a statistical mechanical theory recently developed for DNA cyclization to model DNA looping, taking into account protein flexibility. Notwithstanding the underlying theoretical similarity, we find that the topological constraint of loop closure leads to the coexistence of multiple classes of loops mediated by the same protein structure. These loop topologies are characterized by dramatic differences in twist and writhe; because of the strong coupling of twist and writhe within a loop, DNA looping can exhibit a complex overall helical dependence in terms of amplitude, phase, and deviations from uniform helical periodicity. Moreover, the DNA-length dependence of optimal looping efficiency depends on protein elasticity, protein geometry, and the presence of intrinsic DNA bends. We derive a rigorous theory of loop formation that connects global mechanical and geometric properties of both DNA and protein and demonstrates the importance of protein flexibility in loop-mediated protein-DNA interactions. PMID:16361335

Zhang, Yongli; McEwen, Abbye E; Crothers, Donald M; Levene, Stephen D

2005-12-16

373

Modeling the Lac repressor-operator assembly: the influence of DNA looping on Lac repressor conformation.  

PubMed

Repression of transcription of the Escherichia coli Lac operon by the Lac repressor (LacR) is accompanied by the simultaneous binding of LacR to two operators and the formation of a DNA loop. A recently developed theory of sequence-dependent DNA elasticity enables one to relate the fine structure of the LacR-DNA complex to a wide range of heretofore-unconnected experimental observations. Here, that theory is used to calculate the configuration and free energy of the DNA loop as a function of its length and base-pair sequence, its linking number, and the end conditions imposed by the LacR tetramer. The tetramer can assume two types of conformations. Whereas a rigid V-shaped structure is observed in the crystal, EM images show extended forms in which two dimer subunits are flexibly joined. Upon comparing our computed loop configurations with published experimental observations of permanganate sensitivities, DNase I cutting patterns, and loop stabilities, we conclude that linear DNA segments of short-to-medium chain length (50-180 bp) give rise to loops with the extended form of LacR and that loops formed within negatively supercoiled plasmids induce the V-shaped structure. PMID:16785444

Swigon, David; Coleman, Bernard D; Olson, Wilma K

2006-06-19

374

Elastic carbon nanotube straight yarns embedded with helical loops  

NASA Astrophysics Data System (ADS)

Introducing stretchability and elasticity into carbon nanotube (CNT) yarns could extend their applications to areas such as stretchable and deformable fiber-based devices and strain sensors. Here, we convert a straight and inelastic yarn into a highly elastic structure by spinning a predefined number of helical loops along the yarn, resulting in a short helical segment with smooth structural transition to the straight portions. The loop-forming process is well controlled, and the obtained straight-helical-straight hybrid yarn is freestanding, stable, and based entirely on CNTs. The elastic and conductive yarns can be stretched to moderate tensile strains (up to 25%) repeatedly for 1000 cycles without producing residual deformation, with a simultaneous and linear change of electrical resistance depending on the strain. Our results indicate that conventional straight CNT yarns could be used as fiber-shaped strain sensors by simple structural modification.Introducing stretchability and elasticity into carbon nanotube (CNT) yarns could extend their applications to areas such as stretchable and deformable fiber-based devices and strain sensors. Here, we convert a straight and inelastic yarn into a highly elastic structure by spinning a predefined number of helical loops along the yarn, resulting in a short helical segment with smooth structural transition to the straight portions. The loop-forming process is well controlled, and the obtained straight-helical-straight hybrid yarn is freestanding, stable, and based entirely on CNTs. The elastic and conductive yarns can be stretched to moderate tensile strains (up to 25%) repeatedly for 1000 cycles without producing residual deformation, with a simultaneous and linear change of electrical resistance depending on the strain. Our results indicate that conventional straight CNT yarns could be used as fiber-shaped strain sensors by simple structural modification. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr33633f

Shang, Yuanyuan; Li, Yibin; He, Xiaodong; Zhang, Luhui; Li, Zhen; Li, Peixu; Shi, Enzheng; Wu, Shiting; Cao, Anyuan

2013-02-01

375

Crystallographic Analysis of Antigen–Antibody Complexes: End-on Insertion of Ligands in Antibodies—CDR3 Loops as Arbiters  

Microsoft Academic Search

As the dominant constituents of the active sites, complementarity-determining regions (CDRs) and particularly the CDR3 loops strongly influence the size and shape of this interdomain space. Six sets of CDR3 loops were extracted from our collection of crystal structures and examined for their modes of association. The CDR3 loops of the NC6.8 Fab face each other across a small crevice

Allen B. Edmundson; Lin Shan; Zhao-chang Fan; Luke W. Guddat; B. Leif Hanson; Kim N. Andersen

1996-01-01

376

Numbers as Shapes  

NSDL National Science Digital Library

In this activity students are asked to relate the numbers 1- 20 to rectangular shapes. Learners use unit squares or cubes to sort numbers by their 'shapes,' either squares, rectangles or sticks (rectangles of unit width). Ideas for implementation, extension and support are included.

2011-08-01

377

Semiconductor sidewall shape estimation  

Microsoft Academic Search

For process control, linewidth measurements are com- monly performed on semiconductor wafers using top-down images from critical dimension measurement scanning electron micro- scopes (CD-SEMs). However, a measure of the line sidewall shape will be required as linewidths continue to shrink. Sidewall shape can be measured by physically cleaving the device and performing an SEM scan of the cross section, but

Philip R. Bingham; Jeffery R. Price; Kenneth W. Tobin; Thomas P. Karnowski

2004-01-01

378

Shape memory polymer nanocomposites  

Microsoft Academic Search

The paper describes the fabrication and characterization of composites with a shape memory polymer matrix and SiC nanoparticulate reinforcements. Composites based on a SMP matrix are active materials capable of recovering relatively large mechanical strains due to the application of heat. The composites were synthesized from a commercial shape memory polymer resin system and particulate SiC with an average diameter

Ken Gall; Martin L. Dunn; Yiping Liu; Dudley Finch; Mark Lake; Naseem A. Munshi

2002-01-01

379

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

380

Shape Modeling Using Homotopy  

Microsoft Academic Search

Introduces a new method of shape modeling using homotopy and object-oriented modeling. Homotopy is a kind of topology that gives more general ideas of presenting invariant properties of geometrical objects and is further expanded to conceptual objects. The conventional shape modeling method, using polygonalization, has serious difficulties in preserving invariant properties, leading to the necessity of a massive amount of

Kenji Ohmori; Tosiyasu L. Kunii

2001-01-01

381

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

382

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

383

Carbon sequestration, optimum forest rotation and their environmental impact  

SciTech Connect

Due to their large biomass forests assume an important role in the global carbon cycle by moderating the greenhouse effect of atmospheric pollution. The Kyoto Protocol recognises this contribution by allocating carbon credits to countries which are able to create new forest areas. Sequestrated carbon provides an environmental benefit thus must be taken into account in cost-benefit analysis of afforestation projects. Furthermore, like timber output carbon credits are now tradable assets in the carbon exchange. By using British data, this paper looks at the issue of identifying optimum felling age by considering carbon sequestration benefits simultaneously with timber yields. The results of this analysis show that the inclusion of carbon benefits prolongs the optimum cutting age by requiring trees to stand longer in order to soak up more CO{sub 2}. Consequently this finding must be considered in any carbon accounting calculations. - Highlights: Black-Right-Pointing-Pointer Carbon sequestration in forestry is an environmental benefit. Black-Right-Pointing-Pointer It moderates the problem of global warming. Black-Right-Pointing-Pointer It prolongs the gestation period in harvesting. Black-Right-Pointing-Pointer This paper uses British data in less favoured districts for growing Sitka spruce species.

Kula, Erhun, E-mail: erhun.kula@bahcesehir.edu.tr [Department of Economics, Bahcesehir University, Besiktas, Istanbul (Turkey); Gunalay, Yavuz, E-mail: yavuz.gunalay@bahcesehir.edu.tr [Department of Business Studies, Bahcesehir University, Besiktas, Istanbul (Turkey)

2012-11-15

384

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

385

Optimum take-off angle in the long jump.  

PubMed

In this study, we found that the optimum take-off angle for a long jumper may be predicted by combining the equation for the range of a projectile in free flight with the measured relations between take-off speed, take-off height and take-off angle for the athlete. The prediction method was evaluated using video measurements of three experienced male long jumpers who performed maximum-effort jumps over a wide range of take-off angles. To produce low take-off angles the athletes used a long and fast run-up, whereas higher take-off angles were produced using a progressively shorter and slower run-up. For all three athletes, the take-off speed decreased and the take-off height increased as the athlete jumped with a higher take-off angle. The calculated optimum take-off angles were in good agreement with the athletes' competition take-off angles. PMID:16195020

Linthorne, Nicholas P; Guzman, Maurice S; Bridgett, Lisa A

2005-07-01

386

Optimum frequency of communication channel for indoor radio telemetry  

NASA Astrophysics Data System (ADS)

A major problem in application of radiotelemetry to biological research and medical practice is indoor interference caused by superposition of forward and reflected waves, with resulting signal fadeout. Avoidance of this effect requires that the radio transmitter operate at the optimum signal wavelength and the radio receiver be placed in the optimum location. A method of determining both is proposed on the basis of an experimental study and a theoretical model. Measurements are made with the Prima radiotelemetry system developed and built by A. A. Kvitka with others and V6-1 selective microvoltmeter, in an 8x5x3.5 cu m large room where the radio receiver is placed successively in three different locations (first in corner 0,0,0 m, then closer to the center 2.5,1.5,1.0 m and 1.25,0.75,1.0 m) while the radio transmitter on a dielectric post is moved around in 0.25 m steps successively in three horizontal planes 1, 1.5, 2 m, respectively, above the floor. Measurements are made at eight frequencies (60, 30, 20, 15, 12, 10, 8.89, 7.5 MHz).

Kvitka, A. A.; Podlepetskiy, B. I.; Chernysheva, S. D.

1985-10-01

387

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

388

Rotation of the geomagnetic field about an optimum pole  

NASA Astrophysics Data System (ADS)

Since 1693, when Halley proposed that secular change was the result of the westward drift of the main field, his simple model has undergone many refinements. These include different drift rates for dipole and non-dipole parts; separation into drifting and standing parts; latitudinal dependence of drift rate; northward drift of the dipole; and non-longitudinal rotations of the individual harmonics of the geomagnetic field. Here we re-examine the model of Malin and Saunders, in which the main field is rotated about an optimum pole which does not necessarily coincide with the geographical pole. The optimum pole and rotation angle are those that bring the main field for epoch T1 closest to that for T2, as indicated by the coefficients of correlation between the spherical harmonic coefficients for the two epochs, after rotation. Malin and Saunders examined the pole positions and rates of rotation using data from 1910 to 1965, and noticed a number of trends. We show that these trends are confirmed by recent IGRF models, spanning the interval 1900-2000 and to degree and order 10. We also show that the effect of the level of truncation is small.

Bülent Tank, S.

2000-02-01

389

Improving submicron CD measurements through optimum operating points  

NASA Astrophysics Data System (ADS)

Some problems encountered when measuring submicron CD patterns with white light conventional optical microscopy are presented. These are intended to support the development of a flexible software controlled new high performance optical system, allowing variation in the illumination degree of coherence, numerical aperture, threshold edge detection criteria, focus plane, giving the user opportunities to optimize the measurements. The paper will present results in measuring 0.90 to 0.65 patterns with opposite polarities in different measuring conditions from which an optimum 'operating point' can be defined considering either +/- 0.030 micrometers accuracy criteria or a +/- 0.020 micrometers reproducibility criteria. From such operating points an optimum numerical aperture and illumination aperture can be selected for a given edge detection criteria. NA selection for best resolution and accuracy is also function of the measuring plane position. For small amount of changes in focus plane, increasing the objective NA may actually decrease the quality of the image intensity profile used for measurement, resulting in decreased reproducibility. Such effects, reported also for submicron lithography imaging systems were observed. An increase in overall accuracy when focus plane is moved from the resist upper surface to the bottom resist surface (wafer surface) is observed for windows measurements.

Dusa, Mircea V.; Roeth, Klaus-Dieter; Jung, Christoph

1991-03-01

390

Pulse shaping system  

DOEpatents

Temporally shaped electrical waveform generation provides electrical waveforms suitable for driving an electro-optic modulator (EOM) which produces temporally shaped optical laser pulses for inertial confinement fusion (ICF) research. The temporally shaped electrical waveform generation is carried out with aperture coupled transmission lines having an input transmission line and an aperture coupled output transmission line, along which input and output pulses propagate in opposite directions. The output electrical waveforms are shaped principally due to the selection of coupling aperture width, in a direction transverse to the lines, which varies along the length of the line. Specific electrical waveforms, which may be high voltage (up to kilovolt range), are produced and applied to the EOM to produce specifically shaped optical laser pulses.

Skeldon, Mark D. (Penfield, NY); Letzring, Samuel A. (Jemez Springs, NM)

1999-03-23

391

Pulse shaping system  

DOEpatents

Temporally shaped electrical waveform generation provides electrical waveforms suitable for driving an electro-optic modulator (EOM) which produces temporally shaped optical laser pulses for inertial confinement fusion (ICF) research. The temporally shaped electrical waveform generation is carried out with aperture coupled transmission lines having an input transmission line and an aperture coupled output transmission line, along which input and output pulses propagate in opposite directions. The output electrical waveforms are shaped principally due to the selection of coupling aperture width, in a direction transverse to the lines, which varies along the length of the line. Specific electrical waveforms, which may be high voltage (up to kilovolt range), are produced and applied to the EOM to produce specifically shaped optical laser pulses. 8 figs.

Skeldon, M.D.; Letzring, S.A.

1999-03-23

392

Near-far resistance of optimum and suboptimum CDMA detectors under multipath  

Microsoft Academic Search

Near-far resistance is one of the most important performance measures in a multiuser communication system, especially in a code division multiple access (CDMA) system. The optimum multiuser detector can achieve the optimum near-far resistance. However, due to its high computational complexity, the optimum detector is impractical to implement. Nevertheless, computation of the near-far resistance of the optimum multiuser detector is

Xiaodong Yue; H. Howard Fan

2005-01-01

393

Effect of loading and lamination parameters on the optimum design of laminated plates  

Microsoft Academic Search

This paper illustrates the effect of loading conditions and lamination parameters on the optimum design of the laminated composite\\u000a plates. Optimum design procedure based on the flexibility criterion is presented in this paper. The objective is to determine\\u000a the optimum thickness of the laminate layers and its optimum orientations without exhibiting any failure. The finite element\\u000a method based on Mindlin

A. E. Assie; A. M. Kabeel; F. F. Mahmoud

2011-01-01

394

Observing the reconnection region in a transequatorial loop system  

NASA Astrophysics Data System (ADS)

A vertical current sheet is a crucial element in many flare/coronal mass ejection (CME) models. For the first time, Liu et al. reported a vertical current sheet directly imaged during the flare rising phase with the EUV Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO). As a follow-up study, here we present the comprehensive analysis and detailed physical interpretation of the observation. The current sheet formed due to the gradual rise of a transequatorial loop system. As the loop legs approached each other, plasma flew at ~ 6 km s-1 into a local area where a cusp-shaped flare loop subsequently formed and the current sheet was seen as a bright, collimated structure of global length (>= 0.25 Rodot) and macroscopic width ((5-10)×103km), extending from 50 Mm above the flaring loop to the border of the EIT field of view (FOV). The reconnection rate in terms of the Alfvén Mach number is estimated to be only 0.005-0.009, albeit a halo CME was accelerated from ~ 400 km s-1 to ~ 1300 km s-1 within the coronagraph FOV. Drifting pulsating structures at metric frequencies were recorded during the impulsive phase, implying tearing of the current sheet in the high corona. A radio Type III burst occurred when the current sheet was clearly seen in EUV, indicative of accelerated electrons beaming upward from the upper tip of the current sheet. A cusp-shaped dimming region was observed to be located above the post-flare arcade during the decay phase in EIT; both the arcade and the dimming expanded with time. With the Coronal Diagnostic Spectrometer (CDS) aboard SOHO, a clear signature of chromospheric evaporation was seen during the decay phase, i.e., the cusp-shaped dimming region was associated with plasma upflows detected with EUV hot emission lines, while the post-flare loop was associated with downflows detected with cold lines. This event provides a comprehensive view of the reconnection geometry and dynamics in the solar corona.

Liu, Rui; Wang, Tong-Jiang; Lee, Jeongwoo; Stenborg, Guillermo; Liu, Chang; Park, Sung-Hong; Wang, Hai-Min

2011-10-01

395

Constricted Hysteresis Loops of Barium Titanate.  

National Technical Information Service (NTIS)

An empirical analysis was made of the change in polarization with time for a constricted hysteresis loop at fixed field strengths. Synthetic constricted loops were obtained by placing two polarized disks in antiparallel and applying a high alternating pot...

G. W. Marks R. D. Redin

1967-01-01

396

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

397

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

398

Mapping the interface between the Local and Loop I bubbles using Strömgren photometry  

Microsoft Academic Search

Context: The Sun is located inside an extremely low density region of quite irregular shape called the Local Bubble or Local Cavity. The fraction of this cavity filled with extremely hot gas is known as the Local Hot Bubble. Close to the Local Bubble, there is an even larger cavity known as Loop I. A ring-like feature observed in X-ray

W. Reis; W. J. B. Corradi

2008-01-01

399

Optimum Design for Suction Chambers of Pipeline Pumps Based on Uniform Design and CFD  

Microsoft Academic Search

Based on the maximal velocity distribution uniformity, the minimal velocity-weighed average bias angle of the outlet section and the minimal hydraulic loss of the suction chamber, three optimum object functions of suction chambers of pipeline pumps are established. According to uniform design, ten optimum schemes are determined with the height H3 and the length L as the optimum parameters, and

Wang Kai; Liu Hou-lin; Yuan Shou-qi; Tan Ming-gao; Wang Yong; Dong Liang

2009-01-01

400

Selection of optimum strapdown attitude algorithms for a spinning reentry vehicle  

Microsoft Academic Search

This paper develops optimum attitude algorithms for a Strapdown Laser Gyro Navigation System for a maneuvering reentry vehicle. Algorithms are selected both for a spinning and coning environment and for a nonspinning maneuvering environment. The optimum algorithm is defined to be one which provides, minimum error between true and computed attitude due to algorithm truncation. The optimum algorithms are obtained

S. G. Hummel

1977-01-01

401

Optimum detection and design of TCM signals under impulsive noise environment  

Microsoft Academic Search

The optimum detection and the design of trellis-coded modulation (TCM) signals under an impulsive noise environment are investigated. The optimum TCM receiver designed for impulsive noise is proposed, and it is shown that the TCM signals achieve better performance than the uncoded ones. Computer simulation shows that this optimum receiver, which is simple and easy to realize, gives a coding

S. Miyamoto; M. Katayama; N. Morinaga

1992-01-01

402

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

403

Operator Calculations in Loop Quantum Gravity  

NASA Astrophysics Data System (ADS)

In canonical quantum gravity we express various geometrical and physical quantities as non-local operators based on loops. The action of these operators leads to expressions which are evaluated with the aid of a specific loop calculus. The loop calculus is closely related to the recoupling theory of colored knots and links with trivalent vertices. We introduce the basic ingredients of the loop calculus and present few examples.

Borissov, R.

1997-08-01

404

Non-Gaussian features from the inverse volume corrections in loop quantum cosmology  

NASA Astrophysics Data System (ADS)

In this paper we study the non-Gaussian features of the primordial fluctuations in loop quantum cosmology with the inverse volume corrections. The detailed analysis is performed in the single field slow-roll inflationary models. However, our results reflect the universal characteristics of bispectrum in loop quantum cosmology. The main corrections to the scalar bispectrum come from two aspects: one is the modifications to the standard Bunch-Davies vacuum, and the other is the corrections to the background dependent variables, such as slow-roll parameters. Our calculations show that the loop quantum corrections make fNL of the inflationary models increase 0.1%. Moreover, we find that two new shapes of non-Gaussian signal arise, which we name F1 and F2. The former gives a unique loop quantum feature, which is less correlated with the local, equilateral, and single types, while the latter is highly correlated with the local one.

Li, Li-Fang; Cai, Rong-Gen; Guo, Zong-Kuan; Hu, Bin

2012-08-01

405

Integer Loop Code Generation for VLIW  

Microsoft Academic Search

Code generation for complex integer loops within the context of a VLIW architecture, has to date, been handled by several disparate methodologies. We provide an empirical study to characterize what a typical complex integer loop is and propose a general solution that optimally modifies the key control dependencies in common integer loops. This single algorithm, integrates several software techniques (assuming

James Radigan; Pohua P. Chang; Utpal Banerjee

1995-01-01

406

Small latin squares, quasigroups, and loops  

Microsoft Academic Search

We present the numbers of isotopy classes and main classes of Latin squares, and the numbers of isomorphism classes of quasigroups and loops, up to order 10. The best previous results were for Latin squares of order 8 (Kolesova, Lam and Thiel, 1990), quasigroups of order 6 (Bower, 2000) and loops of order 7 (Brant and Mullen, 1985). The loops

Brendan D. McKay; Alison Meynert; Wendy Myrvold

2007-01-01

407

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…

Burke, Daniel L.

408

Novel use of an "insertable" loop recorder  

PubMed Central

A patient with palpitations and suspected arrhythmia underwent Holter and external loop recorder monitoring. No arrhythmias were detected by these traditional monitoring methods. An insertable loop recorder (ILR) was placed on the patient’s chest and used as an extended loop recorder. An arrhythmia was ultimately recorded by the externally placed ILR leading to appropriate treatment.

Gimbel, J R

2003-01-01

409

Novel use of an "insertable" loop recorder.  

PubMed

A patient with palpitations and suspected arrhythmia underwent Holter and external loop recorder monitoring. No arrhythmias were detected by these traditional monitoring methods. An insertable loop recorder (ILR) was placed on the patient's chest and used as an extended loop recorder. An arrhythmia was ultimately recorded by the externally placed ILR leading to appropriate treatment. PMID:12748241

Gimbel, J R

2003-06-01

410

Loop Transmission Aspects of ISDN Basic Access  

Microsoft Academic Search

The status of the formulation of standards for loop transmission to provide Basic Access in the North American loop plant is reviewed. The impact of loop plant bridged taps on performance is discussed, the reasons for preferring echo canceller technology over time compression multiplexing are reviewed, and issues involved in the specification of echo canceller requirements are discussed. This includes

JOSEPH W. LECHLEIDER

1986-01-01

411

Identify Current in a Magnetic Loop  

NSDL National Science Digital Library

A cross-section of a circular wire loop carrying an unknown current is shown in the animation. The user can add magnetic field lines, drag the center of the loop to reposition it, drag the top or bottom of the loop to change its size, and add a compass.

Christian, Wolfgang; Belloni, Mario

2006-01-14

412

Rotation scheduling: a loop pipelining algorithm  

Microsoft Academic Search

We consider the resource-constrained scheduling of loops with interiteration dependencies. A loop is modeled as a data flow graph (DFG), where edges are labeled with the number of iterations between dependencies. We design a novel and flexible technique, called rotation scheduling, for scheduling cyclic DFGs using loop pipelining. The rotation technique repeatedly transforms a schedule to a more compact schedule.

Liang-fang Chao; Andrea S. Lapaugh; Edwin Hsing-mean Sha

1997-01-01

413

Noise analysis of phase-locked loops  

Microsoft Academic Search

This work addresses the problem of noise analysis of phase locked loops (PLLs). The problem is formulated as a stochastic differential equation and is solved in presence of circuit white noise sources yielding the spectrum of the PLL output. Specifically, the effect of loop filter characteristics, phase-frequency detector and phase noise of the open loop voltage controlled oscillator (VCO) on

Amit Mehrotra

2000-01-01

414

Interplanetary shocks generated by expanding magnetic loops  

Microsoft Academic Search

We present a self-consistent numerical model of shock wave formation in the heliosphere by an expanding magnetic loop. In the model a coronal mass ejection is initiated by a loss of magnetohydrostatic equilibrium of the loop as a result of an increase of underlying magnetic field strength. The expanding magnetic loops produce propagating shock waves. The plasma motions are described

T. V. Stepanova; A. G. Kosovichev

1993-01-01

415

Shape regression machine.  

PubMed

We present a machine learning approach called shape regression machine (SRM) to segmenting in real time an anatomic structure that manifests a deformable shape in a medical image. Traditional shape segmentation methods rely on various assumptions. For instance, the deformable model assumes that edge defines the shape; the Mumford-Shah variational method assumes that the regions inside/outside the (closed) contour are homogenous in intensity; and the active appearance model assumes that shape/appearance variations are linear. In addition, they all need a good initialization. In contrast, SRM poses no such restrictions. It is a two-stage approach that leverages (a) the underlying medical context that defines the anatomic structure and (b) an annotated database that exemplifies the shape and appearance variations of the anatomy. In the first stage, it solves the initialization problem as object detection and derives a regression solution that needs just one scan in principle. In the second stage, it learns a nonlinear regressor that predicts the nonrigid shape from image appearance. We also propose a boosting regression approach that supports real time segmentation. We demonstrate the effectiveness of SRM using experiments on segmenting the left ventricle endocardium from an echocardiogram of an apical four chamber view. PMID:17633685

Zhou, Shaohua Kevin; Comaniciu, Dorin

2007-01-01

416

Shaped pupil coronagraphy  

NASA Astrophysics Data System (ADS)

At Princeton we have been studying shaped pupil coronagraphs for high contrast imaging and planet finding. These will find applications in both ground and space imaging. In this article we summarize the design procedure for shaped pupils and review the various families of designs we have found. We describe the manufacturing processes we have used to make free standing shaped pupil masks and review our most recent laboratory results with and without wavefront control. We also discuss the factors limiting high contrast in the laboratory and our plans for mitigating them. To cite this article: N.J. Kasdin et al., C. R. Physique 8 (2007).

Kasdin, N. Jeremy; Vanderbei, Robert J.; Belikov, Ruslan

2007-04-01

417

Early structure formation from cosmic string loops  

NASA Astrophysics Data System (ADS)

We examine the effects of cosmic strings on structure formation and on the ionization history of the universe. While Gaussian perturbations from inflation are known to provide the dominant contribution to the large scale structure of the universe, density perturbations due to strings are highly non-Gaussian and can produce nonlinear structures at very early times. This could lead to early star formation and reionization of the universe. We improve on earlier studies of these effects by accounting for high loop velocities and for the filamentary shape of the resulting halos. We find that for string energy scales G?gtrsim10-7, the effect of strings on the CMB temperature and polarization power spectra can be significant and is likely to be detectable by the Planck satellite. We mention shortcomings of the standard cosmological model of galaxy formation which may be remedied with the addition of cosmic strings, and comment on other possible observational implications of early structure formation by strings.

Shlaer, Benjamin; Vilenkin, Alexander; Loeb, Abraham

2012-05-01

418

Loop diuretics in heart failure  

Microsoft Academic Search

Congestion is a major component of the clinical syndrome of heart failure, and diuretic therapy remains the cornerstone of\\u000a congestion management. Despite being widely used, there is very limited evidence from prospective randomized studies to guide\\u000a the prescription and titration of diuretics. A thorough understanding of the pharmacology of loop diuretics is crucial to\\u000a the optimal use of these agents.

G. Michael Felker

419

Loop quantum cosmology: an overview  

Microsoft Academic Search

A brief overview of loop quantum cosmology of homogeneous isotropic models is presented with emphasis on the origin of and\\u000a subtleties associated with the resolution of big bang and big crunch singularities. These results bear out the remarkable\\u000a intuition that John Wheeler had. Discussion is organized at two levels. The the main text provides a bird’s eye view of the

Abhay Ashtekar

2009-01-01

420

Analytical formulation of optimum material properties for viscoelastic damping  

Microsoft Academic Search

Expressions for stored and dissipated energies in anisotropic viscoelastic bodies are derived using generalized Maxwell models. The relationships between shapes of master relaxation modulus curves and dissipation energy and the latter's influence on passive structural motion control are investigated. The master relaxation modulus curves are analytically generated for parametric variations of initial and relaxed moduli, slopes of the transition region

H. H. Hilton; Sung Yi

1992-01-01

421

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

422

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

423

Optimum heart sound signal selection based on the cyclostationary property.  

PubMed

Noise often appears in parts of heart sound recordings, which may be much longer than those necessary for subsequent automated analysis. Thus, human intervention is needed to select the heart sound signal with the best quality or the least noise. This paper presents an automatic scheme for optimum sequence selection to avoid such human intervention. A quality index, which is based on finding that sequences with less random noise contamination have a greater degree of periodicity, is defined on the basis of the cyclostationary property of heart beat events. The quality score indicates the overall quality of a sequence. No manual intervention is needed in the process of subsequence selection, thereby making this scheme useful in automatic analysis of heart sound signals. PMID:23668337

Li, Ting; Qiu, Tianshuang; Tang, Hong

2013-03-17

424

Simulation of an Optimum Multilevel Dynamic Round Robin Scheduling Algorithm  

NASA Astrophysics Data System (ADS)

CPU scheduling has valiant effect on resource utilization as well as overall quality of the system. Round Robin algorithm performs optimally in time shared systems, but it performs more number of context switches, larger waiting time and larger response time. In order to simulate the behavior of various CPU scheduling algorithms and to improve Round Robin scheduling algorithm using dynamic time slice concept, in this paper we produce the implementation of new CPU scheduling algorithm called An Optimum Multilevel Dynamic Round Robin Scheduling (OMDRRS), which calculates intelligent time slice and warps after every round of execution. The results display the robustness of this software, especially for academic, research and experimental use, as well as proving the desirability and efficiency of the probabilistic algorithm over the other existing techniques and it is observed that this OMDRRS projects good performance as compared to the other existing CPU scheduling algorithms.

Goel, Neetu; B. Garg, R.

2013-08-01

425

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

426

Optimum design of composite stiffened panels under combined loading  

NASA Astrophysics Data System (ADS)

Minimum-weight designs of T-stiffened and hat-stiffened panels made of laminated composite material are found with the PANDA2 program. The panels, subjected to axial compression, in-plane shear, and normal pressure, are designed for service in their locally postbuckled states. A program called STAGSMODEL is used for transforming output from PANDA2 to input for STAGS, a general-purpose nonlinear finite element code. STAGS is then used to evaluate the optimum designs. Agreement between results obtained with PANDA2 and STAGS is reasonable for these very complex, very nonlinear problems. Therefore, PANDA2 appears to qualify as a preliminary design tool for composite panels operating in their locally postbuckled states.

Bushnell, D.; Bushnell, W. D.

1995-06-01

427

Optimum mixture design of granular materials reinforced by short fiber  

NASA Astrophysics Data System (ADS)

The strength and deformation characteristics of the granular sand are improved by mixing the flexible short fibers. Many factors such as the mixture ratio, fiber materials, fiber length and orientation affect the improvement effect of the short fiber reinforcement sands. Especially, the mixture ratio of short fiber play very important role for the improvement effect and the mixture design. Although the strength of sand increases by mixing a fiber, excessive mixture reduces that of reinforced sand. In this study, we focused on the relationship between the strength and the mixture ratio of fibers by the triaxial compression experiments and the discrete element simulations. Also, we tried to find the critical point of the improvement effect which would be maximized for the strength of granular sand. As a result, the existence of optimum mixture ratio for the strength of granular sand was confirmed.

Nozoe, Shigeaki; Kaneko, Kenji; Hashizume, Yutaka

2013-06-01

428

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

429

Optimum compositions for thermal insulation of burners and regenerators  

SciTech Connect

The thermal and mechanical properties of thermal insulation compositions applied by spraying were evaluated to determine the optimum composition for the parameters posed by the burners and regenerators of glass-melting furnaces. The effects of varying spray parameters on these properties were also assessed. Changes were made in the binder density while leaving the amount of filler unaltered. With an increase in binder density there was an increase in the apparent density of the insulation. Kaolin wool with an aluminoborophosphate concentrate binder was tested for thermal conductivity, apparent density, and bending, shear, and compression strength against asbestos with water glass as a binder. For walls of the regenerators and a single-layer heat insulation, insulation made from an asbestos-perlite mixture with water glass was recommended.

Zasypkin, V.I.; Popov, O.N.

1988-07-01

430

OPTIMUM DESIGN OF GROYNES FOR STABILIZATION OF LOWLAND RIVERS  

NASA Astrophysics Data System (ADS)

Alluvial rivers at low land as in Bangladesh are highly dynamic in nature; where huge landloss due to severe bank erosion at high flood as well as repeated interruptions of navigation system due to rapid sedimentation at low flow are very common. Groynes, revetments etc. are typically used to overcome these problems, but the goals are not achieved as expected. This study investigates the optimum design of a groyne for its effective functioning. A 2D model, RIC-Nays is utilized in this study upon confirmation. The channel and flow parameters are based on conformity to a typical river of Bangladesh. Four orientations and three configurations of groynes are considered here. The performance of groynes is evaluated through three key indices erosion in channel bed (thalweg), deposition in groyne field, and scour near groyne-tip. Computations reveal that a modified groyne functions better over the straight ones through protection of channel bank from erosion and maintenance of navigation channel as well.

Alauddin, Mohammed; Tsujimoto, Tetsuro

431

Effect of Bending Anisotropy on the 3D Conformation of Short DNA Loops  

NASA Astrophysics Data System (ADS)

The equilibrium three dimensional shape of relatively short loops of DNA is studied using an elastic model that takes into account anisotropy in bending rigidities. Using a reasonable estimate for the anisotropy, it is found that cyclized DNA with lengths that are not integer multiples of the pitch take on nontrivial shapes that involve bending out of planes and formation of kinks. The effect of sequence inhomogeneity on the shape of DNA is addressed, and shown to enhance the geometrical features. These findings could shed some light on the role of DNA conformation in protein DNA interactions.

Norouzi, Davood; Mohammad-Rafiee, Farshid; Golestanian, Ramin

2008-10-01

432

Membranes: Shaping biological matter  

NASA Astrophysics Data System (ADS)

Biological membranes form an extremely complex and dynamic network in cells, guided by specialized protein machinery. A new algorithm analyses membrane shape to extract forces applied by proteins controlling the membranes.

Frolov, Vadim A.; Zimmerberg, Joshua

2009-03-01

433

Shaping Educational Accountability Systems.  

ERIC Educational Resources Information Center

Discusses shaping educational accountability systems in the context of the No Child Left Behind Act of 2001. Suggests ways in which evaluation can contribute to improving and changing accountability systems, especially through the development of standards. (SLD)

Ryan, Katherine

2002-01-01

434

Interactives: 3D Shapes  

NSDL National Science Digital Library

How much liquid can that glass hold? What are the dimensions of that package that's heading off to a friend overseas? Answers to both of those questions (and many more) can be found in this lovely interactive feature on 3D shapes created by experts at the Annenberg Media group. Visitors to this site will learn about three-dimensional geometric shapes by examining a number of objects through a number of interactive exercises and games. The materials are divided into four sections, which include "3D Shapes", "Surface Area & Volume", and "Platonic Solids". The "Platonic Solids" area is quite a bit of fun, as visitors will get the opportunity to print out foldable shapes such as a tetrahedron. A short fifteen question quiz that tests the materials covered by these various activities rounds out the site.

435

The performance of optical phase-locked loops in the presence of nonnegligible loop propagation delay  

Microsoft Academic Search

The optical phase-locked loop is analyzed taking into account shot noise, phase noise, and loop propagation delay. The degradation of loop phase error due to propagation delay is evaluated in terms of the delay bandwidth productomega_{n} cdot tau_{D}. This product was found to have a maximum value of 0.736 for absolute loop stability. The resulting effect on a Costas loop

M. A. Grant; W. Michie; M. Fletcher

1987-01-01

436

Shaped Crystal Growth  

NASA Astrophysics Data System (ADS)

Crystals of specified shape and size (shaped crystals) with controlled defect and impurity structure have to be grown for the successful development of modern engineering. Since the 1950s many hundreds of papers and patents concerned with shaped growth have been published. In this chapter, we do not try to enumerate the successful applications of shaped growth to different materials but rather to carry out a fundamental physical and mathematical analysis of shaping as well as the peculiarities of shaped crystal structures. Four main techniques, based on which the lateral surface can be shaped without contact with the container walls, are analyzed: the Czochralski technique (CZT), the Verneuil technique (VT), the floating zone technique (FZT), and technique of pulling from shaper (TPS). Modifications of these techniques are analyzed as well. In all these techniques the shape of the melt meniscus is controlled by surface tension forces, i.e., capillary forces, and here they are classified as capillary shaping techniques (CST). We look for conditions under which the crystal growth process in each CST is dynamically stable. Only in this case are all perturbations attenuated and a crystal of constant cross section grown without any special regulation. The dynamic stability theory of the crystal growth process for all CST is developed on the basis of Lyapunov's dynamic stability theory. Lyapunov's equations for the crystal growth processes follow from fundamental laws. The results of the theory allow the choice of stable regimes for crystal growth by all CST as well as special designs of shapers in TPS. SCG experiments by CZT, VT, and FZT are discussed but the main consideration is given to TPS. Shapers not only allow crystal of very complicated cross section to be grown but provide a special distribution of impurities. A history of TPS is provided later in the chapter, because it can only be described after explanation of the fundamental principles of shaping. Some shaped crystals, especially sapphire and silicon, have specified structures. The crystal growth of these materials, and some metals, including crystal growth in space, is discussed.

Tatartchenko, Vitali A.

437

Venn Diagram Shape Sorter  

NSDL National Science Digital Library

This interactive Java applet helps students explore attributes of objects by sorting different sized, colored, shapes into Venn Diagrams. The user chooses the type of Venn Diagram including 2 intersecting circles, 2 non-intersecting circles, or a single circle. Two modes include "make the rule," where users create the rules of the circles and then sort, or "guess the rule," where users attempt to sort the shapes into the circles in order to guess the rule the computer has chosen.

2005-01-01

438

Vacancy and interstitial loops in irradiated copper  

SciTech Connect

Significant advances have been made in diffuse scattering studies of irradiation induced dislocation loops in metals. Numerical calculational procedures have been developed that provide accurate diffuse scattering cross sections for vacancy and interstitial loops, and these cross sections have been used in conjunction with x-ray diffuse scattering studies of neutron and ion irradiated copper. Size distributions and concentrations have been obtained for both vacancy and interstitial loops and these results are compared with electron microscopy measurements. The size distributions obtained from diffuse scattering measurements show the vacancy loops to be smaller and more numerous than the interstitial loops, and indicate that equal numbers of vacancies and interstitials are in loops. The diffuse scattering and microscopy size distributions agree at the larger sizes, but the diffuse scattering method identifies more loops of the smaller sizes.

Larson, B.C.; Young, F.W. Jr.

1981-11-01

439

Identification of types of kink modes in coronal loops: principles and application to TRACE results  

NASA Astrophysics Data System (ADS)

We explore the possible signatures of different types of kink modes (horizontal and vertical oscillations in their fundamental mode and second harmonic) which may arise in coronal loops. Based on the 3D geometrical parameters of 14 TRACE loops of transverse oscillations, we simulate qualitatively the loop displacements due to these types of kink mode oscillations. We find that for many combinations of viewing and loop geometry it is not straightforward to distinguish between the two types of kink modes. We have also considered Doppler signatures and found that these can in principle help to obtain unique identifications of the oscillation modes. We then compared the simulated spatial signatures with the observations for 14 TRACE loops. We find that two cases of loop oscillations previously identified as a fundamental horizontal mode appear to be a fundamental vertical mode, while in two other cases it is not possible to clearly distinguish between a horizontal oscillation of the fundamental mode and the second-harmonic, and in six cases it is not possible to clearly distinguish between a fundamental horizontal mode and a second-harmonic vertical mode. In addition, for the particular case that the oscillating loop has a S-shape, we find that the fundamental vertical oscillation can take on the appearance of the horizontal second harmonic due to projection effects. We also present numerical results of three dimensional MHD model of an idealized active region field with S-shaped field-lines. The active region is initialized as a force-free dipole magnetic configuration with uniform density and contains a loop with a higher density than its surroundings. We introduce a velocity pulse which models the impact of a flare on surrounding fields. Both the qualitative study and the MHD simulation support the conclusion of the presence of fundamental mode of vertical kink oscillations in an S-shaped loop. Our interpretation can naturally solve the puzzle of the absence of the fundamental mode and the apparent presence of second harmonic oscillations observed in a TRACE loop by De Moortel and Brady (2007).

Wang, T.; Solanki, S.; Selwa, M.; Ofman, L.

2008-05-01

440

Study of one-dimensional electron hopping and its effects on ESR line shape  

SciTech Connect

Random hopping processes between discrete sites along a finite open chain or around a closed finite loop are examined. Closed form formulae are prescribed for the dependence of the ESR (electron spin resonance) line shape on the chain length and hopping rate. Significant differences between the closed loop and open chain are demonstrated. Deviation at short time from the results of diffusion in a continuum is presented.

Tang, Jau [Argonne National Lab., IL (United States); Dikshit, S.N. [Univ. of Chicago, IL (United States). Dept. of Chemistry; Norris, J.R. [Argonne National Lab., IL (United States)]|[Univ. of Chicago, IL (United States). Dept. of Chemistry

1997-08-01

441

Optimum Structural and Manufacturing Design of a Braided Hollow Composite Part  

NASA Astrophysics Data System (ADS)

Simultaneous material consolidation and shaping, as performed in manufacturing of composite materials, causes a strong interconnection between structural and manufacturing parameters which makes the design process complicated. In this paper, the design of a carbon fiber bicycle stem is examined through the application of a multi-objective optimization method to illustrate the interconnection between structural and manufacturing objectives. To demonstrate the proposed method, a test case dealing with the design of composite part with complex geometry, small size and hollow structure is described. Bladder-assisted Resin Transfer Molding is chosen as the manufacturing method. A finite element model of the stem is created to evaluate the objectives of the structural design, while a simplified 2D model is used to simulate the flow inside the preform during the injection process. Both models are formulated to take into account the variation of fiber orientation, thickness and fiber volume fraction as a function of braid diameters, injection pressure and bladder pressure. Finally, a multiobjective optimization method, called Normalized Normal Constraint Method, is used to find a set of solutions that simultaneously optimizes weight, filling time and strength. The solution to the problem is a set of optimum designs which represent the Pareto frontier of the problem. Pareto frontier helps to gain insight into the trade-off among objectives, whose presence and importance is confirmed by the numerical results presented in this paper.

Ghiasi, Hossein; Lessard, Larry; Pasini, Damiano; Thouin, Maxime

2010-04-01

442

Estrogen receptor action in three dimensions - looping the loop.  

PubMed

Due to advances in genomic technologies, our understanding of estrogen receptor (ER)-mediated transcription in breast cancer cells has evolved significantly in recent years. Genome-wide mapping experiments revealed thousands of ER-binding events, but linking them to the target genes has been an ongoing struggle. A recent paper describes a new technique, called ChIA-PET (chromatin interaction analysis using paired-end tag sequencing), that can directly address these questions. ChIA-PET is an unbiased approach for simultaneously identifying all genome-wide binding events of a transcription factor and those involved in long-range chromatin loops. PMID:20156333

Theodorou, Vasiliki; Carroll, Jason S

2010-02-08

443

Looping of anisotropic, short double-stranded DNA  

NASA Astrophysics Data System (ADS)

Bending of double-stranded DNA (dsDNA) is associated with fundamental biological processes such as genome packaging and gene regulation, and therefore studying sequence-dependent dsDNA bending is a key to understanding biological impact of DNA sequence beyond the genetic code. Average mechanical behavior of long dsDNA is well described by the wormlike chain model, but sequence-dependent anisotropic bendability and bendedness of dsDNA can in principle lead to abnormally high looping probability at short length scales. Here, we measured the looping probability density (J factor) and kinetics of dsDNA as a function of length and curvature using single-molecule FRET (F"orster Resonance Energy Transfer). For theoretical comparison, we calculated the J-factor using a discrete dinucleotide chain model, and also simulated it by Monte Carlo methods. We provide evidences that even when the intrinsic shape of dsDNA is accounted for, the wormlike chain model fails to describe looping dynamics of dsDNA below 200-bp length scale.

Kim, Harold; Le, Tung

2013-03-01

444

Engineering of boron-induced dislocation loops for efficient room-temperature silicon light-emitting diodes  

SciTech Connect

We have studied the role of boron ion energy in the engineering of dislocation loops for silicon light-emitting diodes (LEDs). Boron ions from 10 to 80 keV were implanted in (100) Si at ambient temperature, to a constant fluence of 1x10{sup 15} ions/cm{sup 2}. After irradiation the samples were annealed for 20 min at 950 deg. C by rapid thermal annealing. The samples were analyzed by transmission electron microscopy and Rutherford backscattering spectroscopy. It was found that the applied ion implantation/thermal processing induces interstitial perfect and faulted dislocation loops in {l_brace}111{r_brace} habit planes, with Burgers vectors a/2<110> and a/3<111>, respectively. The loops are located around the projected ion range, but stretch in depth approximately to the end of range. Their size and distribution depend strongly on the applied ion energy. In the 10 keV boron-implanted samples the loops are shallow, with a mean size of {approx}30 nm for faulted loops and {approx}75 nm for perfect loops. Higher energies yield buried, large, and irregularly shaped perfect loops, up to {approx}500 nm, coexisting with much smaller faulted loops. In the latter case much more Si interstitials are bounded by the loops, which are assigned to a higher supersaturation of interstitials in as-implanted samples, due to separated Frenkel pairs. An interesting phenomenon was found: the perfect loops achieved a steady-state maximum size when the ion energy reached 40 keV. Further increase of the ion energy only increased the number of these large loops and made them bury deeper in the substrate. The results of this work contribute to laying a solid ground in controlling the size and distribution of dislocation loops in the fabrication of silicon LEDs.

Milosavljevic, M.; Shao, G.; Lourenco, M.A.; Gwilliam, R.M.; Homewood, K.P. [Advanced Technology Institute, School of Electronics and Physical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH (United Kingdom); School of Engineering, University of Surrey, Guildford, Surrey, GU2 7XH (United Kingdom); Advanced Technology Institute, School of Electronics and Physical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH (United Kingdom)

2005-04-01

445

Neural Network Modeling of Weld Pool Shape in Pulsed-Laser Aluminum Welds.  

National Technical Information Service (NTIS)

A neural network model was developed to predict the weld pool shape for pulsed-laser aluminum welds. Several different network architectures were examined and the optimum architecture was identified. The neural network was then trained and, in spite of th...

Y. S. Iskander E. M. Oblow J. M. Vitek

1998-01-01

446

A study of three-dimensional shape machining with an EC?M system  

Microsoft Academic Search

This paper presents an electrochemical micromachining (EC?M) system developed with a machining gap control system. As a preliminary, electrochemical machining (ECM) experiments are carried out. The optimum machining condition of ECM is determined in terms of machining voltage, machining pulse length, amplitude of the electrode for flushing out contamination, and electrolyte concentration. After the preliminary ECM experiments, three-dimensional shape micromachining

Tsuneo Kurita; Kunio Chikamori; Shinichirou Kubota; Mitsuro Hattori

2006-01-01

447

Shaping of an electron beam in high-resolution CRTs for reduction of moire fringes  

Microsoft Academic Search

In order to reduce the raster moire fringes appearing in high-resolution CRTs, an evaluation technique is developed which simulates visual appearances of the moire patterns by using a Gaussian weighting method. It has been found that the moire patterns are strongly influenced by the shape of an electron beam profile. By using the evaluation technique, optimum electron beam profiles for

S. Onozawa; S. Mikoshiba; S. Shirai; K. Oku; K. Oshita; M. Sawahata

1999-01-01

448

Sagnac interferometric multipass loop amplifier.  

PubMed

We propose and investigate experimentally an interferometrically stable, polarization-selective pulse multiplexing scheme for direct laser amplification of picosecond pulses. The basic building block of this scheme is a Sagnac loop which allows for a straightforward scaling of the pulse-multiplexing scheme. Switching the amplifier from single-pulse amplification to burst mode increases extraction efficiency, reduces parasitic non-linearities in the gain medium and allows for higher output energies. Time-frequency analysis of the amplified output pulses demonstrates the viability of this approach. PMID:23187278

Roither, S; Verhoef, A J; Mücke, O D; Reider, G A; Pugžlys, A; Baltuška, A

2012-10-22

449

Amplitude Control: Closing the Loop  

NASA Astrophysics Data System (ADS)

We are using a compensated zero-path-difference Michelson interferometer to control optical amplitude and phase for application to the correction of optical errors in telescopes. Two spatial light modulators are used in place of the usual mirrors in the Michelson. The spatial light modulators are 128x128 pixel arrays from Boulder Nonlinear Systems. We have previously shown how this device can be used for amplitude control using laser and white-light sources. In this study we will present results of closing the loop around this device with the purpose of making an incident optical field uniform in amplitude. This work is supported by NASA and Princeton University.

Littman, M. G.; Carr, M.; Kasdin, J.; Vanderbei, R.; Spergel, D.

2002-12-01

450

Singularities in loop quantum cosmology.  

PubMed

We show that simple scalar field models can give rise to curvature singularities in the effective Friedmann dynamics of loop quantum cosmology (LQC). We find singular solutions for spatially flat Friedmann-Robertson-Walker cosmologies with a canonical scalar field and a negative exponential potential, or with a phantom scalar field and a positive potential. While LQC avoids big bang or big rip type singularities, we find sudden singularities where the Hubble rate is bounded, but the Ricci curvature scalar diverges. We conclude that the effective equations of LQC are not in themselves sufficient to avoid the occurrence of curvature singularities. PMID:19113690

Cailleteau, Thomas; Cardoso, Antonio; Vandersloot, Kevin; Wands, David

2008-12-17

451

Effect of DNA Hairpin Loops on the Twist of Planar DNA Origami Tiles  

PubMed Central

The development of scaffolded DNA origami, a technique in which a long single-stranded viral genome is folded into arbitrary shapes by hundreds of short synthetic oligonucleotides, represents an important milestone in DNA nanotechnology. Recent findings have revealed that two-dimensional (2D)DNA origami structures based on the original design parameters adopt a global twist with respect to the tile plane, which may be because the conformation of the constituent DNA (10.67 bp/turn) deviates from the natural B-type helical twist (10.4 bp/turn). Here we aim to characterize the effects of DNA hairpin loops on the overall curvature of the tile and explore their ability to control, and ultimately eliminate any unwanted curvature. A series of dumbbell-shaped DNA loops were selectively displayed on the surface of DNA origami tiles with the expectation that repulsive interactions among the neighboring dumbbell loops and between the loops and the DNA origami tile would influence the structural features of the underlying tiles. A systematic, atomic force microscopy (AFM) study of how the number and position of the DNA loops influenced the global twist of the structure was performed, and several structural models to explain the results were proposed. The observations unambiguously revealed that the first generation of rectangular shaped origami tiles adopt a conformation in which the upper right (corner 2) and bottom left (corner 4) corners bend upward out of the plane, causing linear superstructures attached by these corners to form twisted ribbons. Our experimental observations are consistent with the twist model predicted by the DNA mechanical property simulation software CanDo. Through the systematic design and organization of various numbers of dumbbell loops on both surfaces of the tile, a nearly planar rectangular origami tile was achieved.

Li, Zhe; Wang, Lei; Yan, Hao; Liu, Yan

2012-01-01

452

Laser beam shaping techniques  

SciTech Connect

Industrial, military, medical, and research and development applications of lasers frequently require a beam with a specified irradiance distribution in some plane. A common requirement is a laser profile that is uniform over some cross-section. Such applications include laser/material processing, laser material interaction studies, fiber injection systems, optical data image processing, lithography, medical applications, and military applications. Laser beam shaping techniques can be divided into three areas: apertured beams, field mappers, and multi-aperture beam integrators. An uncertainty relation exists for laser beam shaping that puts constraints on system design. In this paper the authors review the basics of laser beam shaping and present applications and limitations of various techniques.

DICKEY,FRED M.; WEICHMAN,LOUIS S.; SHAGAM,RICHARD N.

2000-03-16

453

The Dynamics of Shape  

NASA Astrophysics Data System (ADS)

This thesis consists of two parts, connected by one central theme: the dynamics of the "shape of space". The first part of the thesis concerns the construction of a theory of gravity dynamically equivalent to general relativity (GR) in 3+1 form (ADM). What is special about this theory is that it does not possess foliation invariance, as does ADM. It replaces that "symmetry" by another: local conformal invariance. In so doing it more accurately reflects a theory of the "shape of space", giving us reason to call it emph{shape dynamics} (SD). In the first part we will try to present some of the highlights of results so far, and indicate what we can and cannot do with shape dynamics. Because this is a young, rapidly moving field, we have necessarily left out some interesting new results which are not yet in print and were developed alongside the writing of the thesis. The second part of the thesis will develop a gauge theory for "shape of space"-theories. To be more precise, if one admits that the physically relevant observables are given by shape, our descriptions of Nature carry a lot of redundancy, namely absolute local size and absolute spatial position. This redundancy is related to the action of the infinite-dimensional conformal and diffeomorphism groups on the geometry of space. We will show that the action of these groups can be put into a language of infinite-dimensional gauge theory, taking place in the configuration space of 3+1 gravity. In this context gauge connections acquire new and interesting meanings, and can be used as "relational tools".

Gomes, Henrique

2011-08-01

454

Fuel optimum low-thrust elliptic transfer using numerical averaging  

NASA Astrophysics Data System (ADS)

Low-thrust electric propulsion is increasingly being used for spacecraft missions primarily due to its high propellant efficiency. As a result, a simple and fast method for low-thrust trajectory optimization is of great value for preliminary mission planning. However, few low-thrust trajectory tools are appropriate for preliminary mission design studies. The method presented in this paper provides quick and accurate solutions for a wide range of transfers by using numerical orbital averaging to improve solution convergence and include orbital perturbations. Thus, preliminary trajectories can be obtained for transfers which involve many revolutions about the primary body. This method considers minimum fuel transfers using first-order averaging to obtain the fuel optimum rates of change of the equinoctial orbital elements in terms of each other and the Lagrange multipliers. Constraints on thrust and power, as well as minimum periapsis, are implemented and the equations are averaged numerically using a Gausian quadrature. The use of numerical averaging allows for more complex orbital perturbations to be added in the future without great difficulty. The effects of zonal gravity harmonics, solar radiation pressure, and thrust limitations due to shadowing are included in this study. The solution to a transfer which minimizes the square of the thrust magnitude is used as a preliminary guess for the minimum fuel problem, thus allowing for faster convergence to a wider range of problems. Results from this model are shown to provide a reduction in propellant mass required over previous minimum fuel solutions.

Tarzi, Zahi; Speyer, Jason; Wirz, Richard

2013-05-01

455

Optimum Conditions for Artificial Fruiting Body Formation of Cordyceps cardinalis  

PubMed Central

Stromatal fruiting bodies of Cordyceps cardinalis were successfully produced in cereals. Brown rice, German millet and standard millet produced the longest-length of stromata, followed by Chinese pearl barley, Indian millet, black rice and standard barley. Oatmeal produced the shortest-length of fruiting bodies. Supplementation of pupa and larva to the grains resulted in a slightly enhanced production of fruiting bodies; pupa showing better production than larva. 50~60 g of brown rice and 10~20 g of pupa mixed with 50~60 mL of water in 1,000 mL polypropylene (PP) bottle was found to be optimum for fruiting body production. Liquid inoculation of 15~20 mL per PP bottle produced best fruiting bodies. The optimal temperature for the formation of fruiting bodies was 25?, under conditions of continuous light. Few fruiting bodies were produced under the condition of complete darkness, and the fresh weight was considerable low, compared to that of light condition.

Kim, Soo-Young; Shrestha, Bhushan; Sung, Gi-Ho; Han, Sang-Kuk

2010-01-01

456

Optimum frequency for subsurface-imaging synthetic-aperture radar  

SciTech Connect

A subsurface-imaging synthetic-aperture radar (SISAR) has potential for application in areas as diverse as non-proliferation programs for nuclear weapons to environmental monitoring. However, most conventional synthetic-aperture radars operate at higher microwave frequencies which do not significantly penetrate below the soil surface. This study attempts to provide a basis for determining optimum frequencies and frequency ranges which will allow synthetic-aperture imaging of buried targets. Since the radar return from a buried object must compete with the return from surface clutter, the signal-to-clutter ratio is an appropriate measure of performance for a SISAR. A parameter-based modeling approach is used to model the complex dielectric constant of the soil from measured data obtained from the literature. Theoretical random-surface scattering models, based on statistical solutions to Maxwell`s equations, are used to model the clutter. These models are combined to estimate the signal-to-clutter ratio for canonical targets buried in several soil configurations. Initial results indicate that the HF spectrum (3--30 MHz), although it could be used to detect certain targets under some conditions, has limited practical value for use with SISAR, while the upper vhf through uhf spectrum ({approximately}100 MHz--1 GHz) shows the most promise for a general purpose SISAR system. Recommendations are included for additional research.

Brock, B.C.; Patitz, W.E.

1993-05-01

457

Optimum frequency for subsurface-imaging synthetic-aperture radar  

SciTech Connect

A subsurface-imaging synthetic-aperture radar (SISAR) has potential for application in areas as diverse as non-proliferation programs for nuclear weapons to environmental monitoring. However, most conventional synthetic-aperture radars operate at higher microwave frequencies which do not significantly penetrate below the soil surface. This study attempts to provide a basis for determining optimum frequencies and frequency ranges which will allow synthetic-aperture imaging of buried targets. Since the radar return from a buried object must compete with the return from surface clutter, the signal-to-clutter ratio is an appropriate measure of performance for a SISAR. A parameter-based modeling approach is used to model the complex dielectric constant of the soil from measured data obtained from the literature. Theoretical random-surface scattering models, based on statistical solutions to Maxwell's equations, are used to model the clutter. These models are combined to estimate the signal-to-clutter ratio for canonical targets buried in several soil configurations. Initial results indicate that the HF spectrum (3--30 MHz), although it could be used to detect certain targets under some conditions, has limited practical value for use with SISAR, while the upper vhf through uhf spectrum ([approximately]100 MHz--1 GHz) shows the most promise for a general purpose SISAR system. Recommendations are included for additional research.

Brock, B.C.; Patitz, W.E.

1993-05-01

458

Optimum data transmission over land mobile satellite channels  

NASA Astrophysics Data System (ADS)

Multipath fading severely restricts the accurate data transmission over land mobile satellite networks. The fading plagues the propagation medium by imposing random amplitude and phase variations on the transmission signal. However, the relative effect of an undesired random variation is reduced by the presence of a strong line of sight component. A Rician fading model is used to analyze the data transmission performance of the satellite to ground mobile channel. For this model the received multipath signal consists of the sum of a direct or line of sight component and a fading component due to reflections from objects adjacent to the transmission path. Generally, when a data packet encounters a fade, it most likely contains errors and it will have to be retransmitted. Thus, the size of the packet is crucial to determine the performance of the channel. The optimum packet size is found by applying an analytical model of the dynamics of the Rician channel. The performance criterion is based on the rate of information transfer through the network, the vehicle speed and the modulation fade margin.

Castro, Jonathan P.

1991-10-01

459

Optimum circuit design for the detection of laser photodetachment signals  

NASA Astrophysics Data System (ADS)

Laser photodetachment is a widely used diagnostic technique for the detection of negative ions in low-temperature plasma sources. In one common method electrons, photodetached from the negative ions by an incident laser beam, are collected by a Langmuir probe biased above the local plasma potential. The photodetachment current signal, transmitted through the Langmuir probe feedthrough and interconnecting cables (transmission circuit), is converted into a voltage signal by a detection circuit. The negative ion density and temperature (using the two-pulse technique) are obtained from signal processing. Circuit analysis of the signal acquisition circuit, both transmission and detection parts, is used to obtain the design criteria for the undistorted transmission of the photodetachment signal. The effects of changing the circuit parameters from their optimum values are investigated experimentally in a conventional low-pressure magnetron system. The results show that an inappropriate choice of the circuit parameters can lead to significant distortion of the temporal photodetachment signal, leading to large measurement errors of the negative ion density and temperature.

Bryant, P. M.; Bradley, J. W.

2013-02-01

460

Optimum cooking conditions for shrimp and Atlantic salmon.  

PubMed

The quality and safety of a cooked food product depends on many variables, including the cooking method and time-temperature combinations employed. The overall heating profile of the food can be useful in predicting the quality changes and microbial inactivation occurring during cooking. Mathematical modeling can be used to attain the complex heating profile of a food product during cooking. Studies were performed to monitor the product heating profile during the baking and boiling of shrimp and the baking and pan-frying of salmon. Product color, texture, moisture content, mass loss, and pressed juice were evaluated during the cooking processes as the products reached the internal temperature recommended by the FDA. Studies were also performed on the inactivation of Salmonella cocktails in shrimp and salmon. To effectively predict inactivation during cooking, the Bigelow, Fermi distribution, and Weibull distribution models were applied to the Salmonella thermal inactivation data. Minimum cooking temperatures necessary to destroy Salmonella in shrimp and salmon were determined. The heating profiles of the 2 products were modeled using the finite difference method. Temperature data directly from the modeled heating profiles were then used in the kinetic modeling of quality change and Salmonella inactivation during cooking. The optimum cooking times for a 3-log reduction of Salmonella and maintaining 95% of quality attributes are 100, 233, 159, 378, 1132, and 399 s for boiling extra jumbo shrimp, baking extra jumbo shrimp, boiling colossal shrimp, baking colossal shrimp, baking Atlantic salmon, and pan frying Atlantic Salmon, respectively. PMID:23387897

Brookmire, Lauren; Mallikarjunan, P; Jahncke, M; Grisso, R

2013-02-01

461

Toward the global optimum in zoom lens design  

NASA Astrophysics Data System (ADS)

After more than a century from the introduction of zoom lenses, the selection of the right zoom lens type for a given specification is still a challenge for the optical designer. In the process of lens design, the optical designer is permanently searching for the best zoom lens structure in order to fulfill the complex balance between weight, cost and optical performance. This is a continuous optimization process and the result is a global optimum. The most important factors influencing zoom lens cost are: the number of spherical and aspherical lenses, the number of moving groups and lenses and finally the group sensitivity to displacement and tilt. Every lens group whether moving or not inside the zoom lens, has a specific complexity and sensitivity behavior dependent on the zoom lens type. It is not obvious which type of zoom lens will optimally satisfy the required specification. This paper describes the selection process exemplary for a zoom lens with a medium focal length range from 28mm to 80mm and a quasi constant f-number (FNO) during zooming. The lens is used mainly for cinematographic applications and must be able to maintain best image position for the entire range of object positions during zooming. Alternative solutions with their advantages and disadvantages are shown, analyzed and evaluated.

Dodoc, Aurelian

2012-10-01

462

OPTIMUM INTEGRAL DESIGN FOR MAXIMIZING THE FIELD IN SHORT MAGNETS.  

SciTech Connect

An Optimum Integral Design is introduced for cosine(n{theta}) coils where the entire end-to-end length of the coil generates field with the dilution from ends practically eliminated. The benefits of such a design are particularly significant in short magnets where the overall coil length is comparable to or a few times the coil diameter. The integral field strength is further enhanced since the design allows a larger number of turns than in typical magnet coils. In this concept, the ends and body harmonics are optimized together to create an integral cosine(n{theta}) azimuthal current distribution. The concept was initially developed for wire/cable wound magnets where the bend radius of turns in the ends can be small. However, the benefit of this general approach can be applied to cable magnets as well. The magnetic design of a corrector dipole for the AGS helical magnet, which was recently built and tested, is presented as one of several examples. The other examples include a few sub-compact designs: a dipole with coil length less than a coil diameter, a quadrupole with coil length less than a coil radius, etc. Apart from generating a large integral field for the given length, the computed integral field harmonics in these designs are only a few parts in 10,000 at 2/3, of the coil radius.

GUPTA,R.

2004-10-03

463

Optimum contribution selection for conserved populations with historic migration  

PubMed Central

Background In recent decades, local varieties of domesticated animal species have been frequently crossed with economically superior breeds which has resulted in considerable genetic contributions from migrants. Optimum contribution selection by maximizing gene diversity while constraining breeding values of the offspring or vice versa could eventually lead to the extinction of local breeds with historic migration because maximization of gene diversity or breeding values would be achieved by maximization of migrant contributions. Therefore, other objective functions are needed for these breeds. Results Different objective functions and side constraints were compared with respect to their ability to reduce migrant contributions, to increase the genome equivalents originating from native founders, and to conserve gene diversity. Additionally, a new method for monitoring the development of effective size for breeds with incomplete pedigree records was applied. Approaches were compared for Vorderwald cattle, Hinterwald cattle, and Limpurg cattle. Migrant contributions could be substantially decreased for these three breeds, but the potential to increase the native genome equivalents is limited. Conclusions The most promising approach was constraining migrant contributions while maximizing the conditional probability that two alleles randomly chosen from the offspring population are not identical by descent, given that both descend from native founders.

2012-01-01

464

[An optimum donor site for venous grafting for microsurgery].  

PubMed

We report the results of an anatomic study based on 10 cadavers. The aim of this work is to find an optimum donor site for venous grafts which is safe, reproducible, and suitable for microsurgery stitches especially in finger reimplantation, when a long and small calibre graft is needed. This study describes the deep venous network of the radial artery, an original donor site for microsurgical venous grafts. The second aim is to describe our technique of harvesting. Dissections always show two satellite veins, that can be harvested with optimal average diameter of 1.8mm constant over the whole length. The maximum length available is about 126.5mm for the radial satellite vein, and 125 mm for the ulnar one, with a few number of collateral ligatures needed. No tying is required in 60% cases for radial satellite vein, and one ligature for the other 40%, whereas in the ulnar satellite vein, no tying is needed in 80% and just one in the other 20%. This original site is advantageous in microsurgery of the upper limb, offering an easy, quick, safe and reproducible option in an emergency situation. PMID:21621446

Grimaud, O; Delpit, X; Hardy, P

2011-05-10

465

Shapes and Angles  

NSDL National Science Digital Library

In this activity (page 7 of PDF), learners will identify the general two-dimensional geometric shape of the uppermost cross section of an impact crater. They will also draw connections between the general two-dimensional geometric shape of an impact crater and the projectile's angle of impact. There are two versions of this activity: Challenge, where students construct a launcher and create their own craters; and Non-Challenge where students analyze pictures of craters. The Moon Math: Craters! guide follows a 5E approach, applying concepts of geometry, modeling, data analysis to the NASA lunar spacecraft mission, LCROSS.

Nasa

2012-05-08

466

Light-Cone Wilson Loops and the String/Gauge Correspondence  

NASA Astrophysics Data System (ADS)

We investigate a Pi-shape Wilson loop in N=4 super Yang-Mills theory, which lies partially at the light-cone, and consider an associated open superstring in AdS5 × S5. We discuss how this Wilson loop determines the anomalous dimensions of conformal operators with large Lorentz spin and present an explicit calculation in perturbation theory to order lambda. We find the minimal surface in the supergravity approximation, that reproduces the Gubser, Klebanov and Polyakov prediction for the anomalous dimensions at large lambda = gYM2N, and discuss its quantum-mechanical interpretation.

Makeenko, Yuri

2003-01-01

467

Extended loop representation of quantum gravity  

SciTech Connect

A new representation of quantum gravity is developed. This formulation is based on an extension of the group of loops. The enlarged group that we call the extended loop group behaves locally as an infinite dimensional Lie group. Quantum gravity can be realized on the state space of extended loop-dependent wave functions. The extended representation generalizes the loop representation and contains this representation as a particular case. The resulting diffeomorphism and Hamiltonian constraints take a very simple form and allow us to apply functional methods and simplify the loop calculus. In particular we show that the constraints are linear in the momenta. The nondegenerate solutions known in the loop representation are also solutions of the constraints in the new representation. An approach to the regularization problems associated with the formal calculus is performed. We show that the solutions are generalized knot invariants, smooth in the extended variables, and any framing is unnecessary.

Di Bartolo, C. (Departamento de Fisica, Universidad Simon Bolivar, Apartado 89000, Caracas 1080-A (Venezuela)); Gambini, R.; Griego, J. (Instituto de Fisica, Facultad de Ciencias, Tristan Narvaja 1674, Montevideo (Uruguay))

1995-01-15

468

Wilson loop from a Dyson equation  

SciTech Connect

The Dyson equation proposed for planar temporal Wilson loops in the context of supersymmetric gauge theories is critically analyzed thereby exhibiting its ingredients and approximations involved. We reveal its limitations and identify its range of applicability in nonsupersymmetric gauge theories. In particular, we show that this equation is applicable only to strongly asymmetric planar Wilson loops (consisting of a long and a short pair of loop segments) and as a consequence the Wilsonian potential can be extracted only up to intermediate distances. By this equation the Wilson loop is exclusively determined by the gluon propagator. We solve the Dyson equation in Coulomb gauge for the temporal Wilson loop with the instantaneous part of the gluon propagator and for the spatial Wilson loop with the static gluon propagator obtained in the Hamiltonian approach to continuum Yang-Mills theory and on the lattice. In both cases we find a linearly rising color potential.

Pak, M.; Reinhardt, H. [Institut fuer Theoretische Physik, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

2009-12-15

469

Resolving the Coronal Loop Controversy with AIA  

NASA Astrophysics Data System (ADS)

An important component of the coronal loop controversy involves conflicting results on the diagnostic of one of the fundamental properties: the cross-field temperature distribution. Are loops isothermal or multithermal? Is the observed loop a single flux tube or a collection of tangled magnetic strands? Resolving this controversy has important implications for the coronal heating problem. The coronal filters in the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory peak at different temperatures; the series covers the entire active region temperature range, making AIA ideal for multithermal analysis. Here we analyze coronal loops from several active regions that have been observed by AIA. We find that a few of our loops have narrow temperature distributions, which may be consistent with isothermal plasma and can be modeled with a single flux tube. Other loops, however, have broader temperature distributions, and are not well-modeled by isothermal plasma; these appear to be multi-stranded.

Schmelz, Joan T.

2011-05-01

470

Piecewise linear loop quantum gravity  

NASA Astrophysics Data System (ADS)

We define a modification of loop quantum gravity (LQG) in which graphs are required to consist of piecewise linear edges, which we call piecewise linear LQG (plLQG). At the diffeomorphism-invariant level, we prove that plLQG is equivalent to standard LQG, as long as one chooses the class of diffeomorphisms appropriately. That is, we exhibit a unitary map between the diffeomorphism-invariant Hilbert spaces that maps physically equivalent operators into each other. In addition, using the same ideas as in standard LQG, one can define a Hamiltonian and master constraint in plLQG, and the unitary map between plLQG and LQG then provides an exact isomorphism of dynamics in the two frameworks. Furthermore, loop quantum cosmology (LQC) can be exactly embedded into plLQG. This allows a prior program of the author to embed LQC into LQG at the dynamical level to proceed. In particular, this allows a formal expression for a physically motivated embedding of LQC into LQG at the diffeomorphism-invariant level to be given.

Engle, Jonathan

2010-02-01

471

Smooth-shape assumption for perceiving shapes from shading.  

PubMed

Humans can perceive three-dimensional shapes from shading, but reconstructing the original shape of an object from shading alone (luminance distribution) is mathematically impossible. Researchers have used different assumptions and reported that the human visual systems can resolve this difficulty. Here, we propose an assumption for perceiving shape from shading: that the object shape is assumed to be smooth rather than angular. In experiment 1, we investigated the effect of shape smoothness by manipulating the shading profile of the test region. In experiment 2, we further investigated the effect of shape smoothness by manipulating shapes of the regions bordering on the test region using binocular disparity. Each stimulus in our experiments is interpretable from shading as having either smooth or angular edges. Observers responded to the perceived shape while viewing the stimuli, and most tended to perceive smooth rather than angular edges. These results support the idea that the smooth-shape assumption is effective for perceiving shape from shading. PMID:17455755

Sawada, Tadamasa; Kaneko, Hirohiko

2007-01-01

472

Experimental investigation of penetration performance of shaped charge into concrete targets  

NASA Astrophysics Data System (ADS)

In order to develop a tandem warhead that can effectively destroy concrete targets, this paper explores the penetration performance of shaped charges with different cone angles and liner materials into concrete targets by means of experiments. The penetration process and the destruction mechanism of concrete targets by shaped charges and kinetic energy projectiles are analyzed and compared. Experimental results suggest that both kinetic energetic projectile and shaped charge are capable of destroying concrete targets, but the magnitudes of damage are different. Compared with a kinetic energy projectile, a shaped charge has more significant effect of penetration into the target, and causes very large spalling area. Hence, a shaped charge is quite suitable for first-stage charge of tandem warhead. It is also found that, with the increase of shaped charge liner cone angle, the depth of penetration decreases gradually while the hole diameter becomes larger. Penetration depth with copper liner is larger than of aluminum liner but hole diameter is relatively smaller, and the shaped charge with steel liner is between the above two cases. The shaped charge with a cone angle of 100° can form a jet projectile charge (JPC). With JPC, a hole with optimum depth and diameter on concrete targets can be formed, which guarantees that the second-stage warhead smoothly penetrates into the hole and explodes at the optimum depth to achieve the desired level of destruction in concrete targets.

Wang, Cheng; Ma, Tianbao; Ning, Jianguo

2008-06-01

473

Classical Polylogarithms for Amplitudes and Wilson Loops  

SciTech Connect

We present a compact analytic formula for the two-loop six-particle maximally helicity violating remainder function (equivalently, the two-loop lightlike hexagon Wilson loop) in N=4 supersymmetric Yang-Mills theory in terms of the classical polylogarithm functions Li{sub k} with cross ratios of momentum twistor invariants as their arguments. In deriving our formula we rely on results from the theory of motives.

Goncharov, A. B. [Department of Mathematics, Brown University, Box 1917, Providence, Rhode Island 02912 (United States); Spradlin, M.; Vergu, C.; Volovich, A. [Department of Physics, Brown University, Box 1843, Providence, Rhode Island 02912 (United States)

2010-10-08

474

Classical Polylogarithms for Amplitudes and Wilson Loops  

NASA Astrophysics Data System (ADS)

We present a compact analytic formula for the two-loop six-particle maximally helicity violating remainder function (equivalently, the two-loop lightlike hexagon Wilson loop) in N=4 supersymmetric Yang-Mills theory in terms of the classical polylogarithm functions Lik with cross ratios of momentum twistor invariants as their arguments. In deriving our formula we rely on results from the theory of motives.

Goncharov, A. B.; Spradlin, M.; Vergu, C.; Volovich, A.

2010-10-01

475

Threshold hadronic event shapes with effective field theory  

SciTech Connect

Hadronic event shapes, that is, event shapes at hadron colliders, could provide a great way to test both standard and nonstandard theoretical models. However, they are significantly more complicated than event shapes at e{sup +}e{sup -} colliders, involving multiple hard directions, multiple channels, and multiple color structures. In this paper, hadronic event shapes are examined with soft-collinear effective theory (SCET) by expanding around the dijet limit. A simple event shape, threshold thrust, is defined. This observable is global and has no free parameters, making it ideal for clarifying how resummation of hadronic event shapes can be done in SCET. Threshold thrust is calculated at next-to-leading fixed order (NLO) in SCET and resummed to next-to-next-to-leading logarithmic (NNLL) accuracy. The scale-dependent parts of the soft function are shown to agree with what is expected from general observations, and the factorization formula is explicitly shown to be renormalization group invariant to 1-loop. Although threshold thrust is not itself expected to be phenomenologically interesting, it can be modified into a related observable which allows the jet p{sub T} distribution to be calculated and resummed to NNLL+NLO accuracy. As in other processes, one expects resummation to be important even for moderate jet momenta due to dynamical threshold enhancement. A general discussion of threshold enhancement and nonglobal logs in hadronic event shapes is also included.

Kelley, Randall; Schwartz, Matthew D. [Center for the Fundamental Laws of Nature, Harvard University, Cambridge, Massachusetts 02138 (United States)

2011-02-01

476

Hydration structure of antithrombin conformers and water transfer during reactive loop insertion.  

PubMed Central

The serine protease inhibitor antithrombin undergoes extensive conformational changes during functional interaction with its target proteases. Changes include insertion of the reactive loop region into a beta-sheet structure in the protein core. We explore the possibility that these changes are linked to water transfer. Volumes of water transferred during inhibition of coagulation factor Xa are compared to water-permeable volumes in the x-ray structure of two different antithrombin conformers. In one conformer, the reactive loop is largely exposed to solvent, and in the other, the loop is inserted. Hydration fingerprints of antithrombin (that is, water-permeable pockets) are analyzed to determine their location, volume, and size of access pores, using alpha shape-based methods from computational geometry. Water transfer during reactions is calculated from changes in rate with osmotic pressure. Hydration fingerprints prove markedly different in the two conformers. There is an excess of 61-76 water molecules in loop-exposed as compared to loop-inserted conformers. Quantitatively, rate increases with osmotic pressure are consistent with the transfer of 73 +/- 7 water molecules. This study demonstrates that conformational changes of antithrombin, including loop insertion, are linked to water transfer from antithrombin to bulk solution. It also illustrates the combined use of osmotic stress and analytical geometry as a new and effective tool for structure/function studies.

Liang, J; McGee, M P

1998-01-01

477

The role of mechanical forces in dextral rotation during cardiac looping in the chick embryo.  

PubMed

Cardiac looping is a vital morphogenetic process that transforms the initially straight heart tube into a curved tube normally directed toward the right side of the embryo. While recent work has brought major advances in our understanding of the genetic and molecular pathways involved in looping, the biophysical mechanisms that drive this process have remained poorly understood. This paper examines the role of biomechanical forces in cardiac rotation during the initial stages of looping, when the heart bends and rotates into a c-shaped tube (c-looping). Embryonic chick hearts were subjected to mechanical and chemical perturbations, and tissue stress and strain were studied using dissection and fluorescent labeling, respectively. The results suggest that (1) the heart contains little or no intrinsic ability to rotate, as external forces exerted by the splanchnopleure (SPL) and the omphalomesenteric veins (OVs) drive rotation; (2) unbalanced forces in the omphalomesenteric veins play a role in left-right looping directionality; and (3) in addition to ventral bending and rightward rotation, the heart tube also bends slightly toward the right. The results of this study may help investigators searching for the link between gene expression and the mechanical processes that drive looping. PMID:15282152

Voronov, Dmitry A; Alford, Patrick W; Xu, Gang; Taber, Larry A

2004-08-15

478

MutS mediates heteroduplex loop formation by a translocation mechanism.  

PubMed Central

Interaction of Escherichia coli MutS and MutL with heteroduplex DNA has been visualized by electron microscopy. In a reaction dependent on ATP hydrolysis, complexes between a MutS dimer and a DNA heteroduplex are converted to protein-stabilized, alpha-shaped loop structures with the mismatch in most cases located within the DNA loop. Loop formation depends on ATP hydrolysis and loop size increases linearly with time at a rate of 370 base pairs/min in phosphate buffer and about 10,000 base pairs/min in the HEPES buffer used for repair assay. These observations suggest a translocation mechanism in which a MutS dimer bound to a mismatch subsequently leaves this site by ATP-dependent tracking or unidimensional movement that is in most cases bidirectional from the mispair. In view of the bidirectional capability of the methyl-directed pathway, this reaction may play a role in determination of heteroduplex orientation. The rate of MutS-mediated DNA loop growth is enhanced by MutL, and when both proteins are present, both are found at the base of alpha-loop structures, and both can remain associated with excision intermediates produced in later stages of the reaction.

Allen, D J; Makhov, A; Grilley, M; Taylor, J; Thresher, R; Modrich, P; Griffith, J D

1997-01-01

479

Attojoule calorimetry of mesoscopic superconducting loops.  

PubMed

We report the first experimental evidence of nontrivial thermal behavior of the simplest mesoscopic system--a superconducting loop. By measuring the specific heat C of an array of 450,000 noninteracting aluminum loops with very high accuracy of approximately 20 fJ/K, we show that the loops go through a periodic sequence of phase transitions (with a period of an integer number of magnetic flux quanta) as the magnetic flux threading each loop is increased. The transitions are well described by the Ginzburg-Landau theory and are accompanied by discontinuities of C of only several thousands of Boltzmann constants kB. PMID:15783684

Bourgeois, O; Skipetrov, S E; Ong, F; Chaussy, J

2005-02-10

480

(Re)inventing the circadian feedback loop.  

PubMed

For 20 years, researchers have thought that circadian clocks are defined by feedback loops of transcription and translation. The rediscovery of posttranslational circadian oscillators in diverse organisms forces us to rethink this paradigm. Meanwhile, the original "basic" feedback loops of canonical circadian clocks have swelled to include dozens of additional proteins acting in interlocked loops. We review several self-sustained clock mechanisms and propose that minimum requirements for diurnal timekeeping might be simpler than those of actual free-running circadian oscillators. Thus, complex mechanisms of circadian timekeeping might have evolved from random connections between unrelated feedback loops with independent but limited time-telling capability. PMID:22421040

Brown, Steven A; Kowalska, Elzbieta; Dallmann, Robert

2012-03-13

481

Multi-instrument observations of coronal loops  

NASA Astrophysics Data System (ADS)

This document exhibits results of analysis from data collected with multiple EUV satellites (SOHO, TRACE, STEREO, Hinode, and SDO). The focus is the detailed observation of coronal loops using multiple instruments, i.e. filter imagers and spectrometers. Techniques for comparing the different instruments and deriving loop parameters are demonstrated. Attention is given to the effects the different instruments may introduce into the data and their interpretation. The assembled loop parameters are compared to basic energy balance equations and scaling laws. Discussion of the blue-shifted, asymmetric, and line broadened spectral line profiles near the footpoints of coronal loops is made. The first quantitative analysis of the anti-correlation between intensity and spectral line broadening for isolated regions along loops and their footpoints is presented. A magnetic model of an active region shows where the separatrices meet the photospheric boundary. At the boundary, the spectral data reveal concentrated regions of increased blue-shifted outflows, blue wing asymmetry, and line broadening. This is found just outside the footpoints of bright loops. The intensity and line broadening in this region are anti-correlated. A comparison of the similarities in the spectroscopic structure near the footpoints of the arcade loops and more isolated loops suggests the notion of consistent structuring for the bright loops forming an apparent edge of an active region core.

Scott, Jason Terrence

482

Cosmic string loops in the expanding universe  

SciTech Connect

We study the production of loops in the cosmic string network in the expanding background by means of a numerical simulation exact in the flat-spacetime limit and first order in the expansion rate. We find an initial regime characterized by production of small loops at the scale of the initial correlation length, but later we see the emergence of a scaling regime of loop production. This qualitatively agrees with earlier expectations derived from the results of flat-spacetime simulations. In the final scaling regime we find that the characteristic length of loops scales as {approx}0.1t in both radiation and matter eras.

Olum, Ken D.; Vanchurin, Vitaly [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, Massachusetts 02155 (United States); Arnold Sommerfeld Center for Theoretical Physics, Department fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Theresienstr. 37, D-80333, Munich (Germany)

2007-03-15

483

Laser net shape welding  

Microsoft Academic Search

Over the last 40 years of laser welding practice, weld bead geometry always experiences a section of the weld bead slightly above or below the parent material surface. In this paper, a new concept – net shape welding is introduced, whereby the weld joint fusion zone is flat to the parent material surface. Experimental work was carried out to demonstrate

Lin Li; Ramadan Eghlio; Sundar Marimuthu

2011-01-01

484

Coordination of hand shape.  

PubMed

The neural control of hand movement involves coordination of the sensory, motor, and memory systems. Recent studies have documented the motor coordinates for hand shape, but less is known about the corresponding patterns of somatosensory activity. To initiate this line of investigation, the present study characterized the sense of hand shape by evaluating the influence of differences in the amount of grasping or twisting force, and differences in forearm orientation. Human subjects were asked to use the left hand to report the perceived shape of the right hand. In the first experiment, six commonly grasped items were arranged on the table in front of the subject: bottle, doorknob, egg, notebook, carton, and pan. With eyes closed, subjects used the right hand to lightly touch, forcefully support, or imagine holding each object, while 15 joint angles were measured in each hand with a pair of wired gloves. The forces introduced by supporting or twisting did not influence the perceptual report of hand shape, but for most objects, the report was distorted in a consistent manner by differences in forearm orientation. Subjects appeared to adjust the intrinsic joint angles of the left hand, as well as the left wrist posture, so as to maintain the imagined object in its proper spatial orientation. In a second experiment, this result was largely replicated with unfamiliar objects. Thus, somatosensory and motor information appear to be coordinated in an object-based, spatial-coordinate system, sensitive to orientation relative to gravitational forces, but invariant to grasp forcefulness. PMID:21389230

Pesyna, Colin; Pundi, Krishna; Flanders, Martha

2011-03-01

485

Optimization of shaped charges  

Microsoft Academic Search

Efficient design of shaped charges requires a full calculation of all three basic processes involved: liner collapse, jet fragmentation, and subsequent penetration in the target. Claims have been made [S. S. Grigoryan and N. S. Sanasaryan, Mekh. Zhidkosti Gaza 6, 9 (1974); N. S. Sanasaryan, ibid. 6, 151 (1975)] that for given standoff distance, a certain initial jet velocity profile

B. S. Haugstad; O. S. Dullum

1984-01-01

486

The Shape Song  

NSDL National Science Digital Library

This video features a sing-along song about shapes. The first half of this song is for preschoolers: circle, triangle, rectangle, square. The second half is for primary grade students: oval, diamond, heart, crescent, rhombus, trapezoid, pentagon, hexagon, heptagon, and octagon.

Grancie48

2011-06-17

487

Geometric Shapes in Architecture  

NSDL National Science Digital Library

A unit designed to improve students' understanding and appreciation of basic geometric shapes used in architecture. It describes various plane geometric figures and discusses in detail the properties of several of these figures. Perimeters and areas of polygons and circles are computed.

Fox, Lauretta J.

2007-02-22

488

Sounds exaggerate visual shape  

PubMed Central

While perceiving speech, people see mouth shapes that are systematically associated with sounds. In particular, a vertically stretched mouth produces a /woo/ sound, whereas a horizontally stretched mouth produces a /wee/ sound. We demonstrate that hearing these speech sounds alters how we see aspect ratio, a basic visual feature that contributes to perception of 3D space, objects and faces. Hearing a /woo/ sound increases the apparent vertical elongation of a shape, whereas hearing a /wee/ sound increases the apparent horizontal elongation. We further demonstrate that these sounds influence aspect ratio coding. Viewing and adapting to a tall (or flat) shape makes a subsequently presented symmetric shape appear flat (or tall). These aspect ratio aftereffects are enhanced when associated speech sounds are presented during the adaptation period, suggesting that the sounds influence visual population coding of aspect ratio. Taken together, these results extend previous demonstrations that visual information constrains auditory perception by showing the converse – speech sounds influence visual perception of a basic geometric feature.

Sweeny, Timothy D.; Guzman-Martinez, Emmanuel; Ortega, Laura; Grabowecky, Marcia; Suzuki, Satoru

2012-01-01